This document summarizes a study that uses a pseudo-homogeneous CSTR simulation to model a fluidized bed reactor for producing polyethylene via gas-phase polymerization of ethylene. The simulation includes the effect of adding the inert condensing agent n-hexane to the feed stream. It uses the Sanchez-Lacombe equation of state to predict how n-hexane increases the solubility of ethylene in the growing polyethylene phase, thereby enhancing the polymerization rate. The results show that adding 0.1 bar of n-hexane can increase polyethylene production by about 2%. Reactor temperature decreases more sharply when operating in condensed mode with higher n-hexane levels in the feed.
This document discusses using a pseudo-homogeneous CSTR simulation to model a fluidized bed reactor producing polyethylene via gas-phase polymerization including the effect of n-hexane co-solubility predictions using the Sanchez-Lacombe equation of state. The simulation considers an ethylene/nitrogen/n-hexane gas phase in equilibrium with an ethylene/polyethylene/n-hexane polymer phase. Results showed polyethylene production increased about 2% with 0.1 bar of n-hexane due to co-solubility effects. Reactor temperature decreased more sharply in condensed mode with each 0.1 bar increase in n-hexane pressure.
Kinetics in UP
This document discusses chemical kinetics and reaction rates. It defines key kinetics concepts like reaction order, rate laws, and rate constants. Specific examples covered include first-order, second-order, and zero-order reactions. The effects of temperature, catalysts, and physical conditions on reaction rates are also explained. Several industrial reaction mechanisms are summarized, such as the chlorination of methane, hydrolysis, nitration of benzene, and sulfonation of benzene.
Introduction
Basis
Importance
Classification
Homogeneous catalysis
Mechanism
Example
Heterogeneous catalysis
Mechanism
Examples
Promoters
Catalytic Poisoning
Autocatalysis
Enzyme catalysis
Enzymes
References
Catalyst: -
The substances that alter the rate of a reaction but itself remains chemically unchanged at the end of the reaction is called a Catalyst.
The process is called Catalysis.
prop-
A catalyst cannot start the reaction by itself.
Catalytic activity increases as surface area of catalyst increases.
Catalysts are thermolabile, this effect is very well pronounced in enzymes.
Catalytic activity is maximum at a catalyst’s optimum temperature.
A catalyst does not alter the position of the equilibrium, instead it helps in achieving the equilibrium faster.
Dynamic modeling and simulation of catalyticJhonatan Soto
This document summarizes a study on dynamic modeling and simulation of catalytic naphtha reforming. The dynamic model developed includes reaction kinetics, heat exchanger models, and furnace models. Kinetic modeling of the fixed bed reactors connected in series forms the core of the simulation. Reaction rates are represented using Hougen-Watson Langmuir-Hinshelwood expressions. Simulation results using MATLAB show fair agreement with plant data. The model can capture major dynamics in the reforming process system.
The Effect of Temperature on Aromatic Yield of Treated Heavy Naphthene From B...IJRESJOURNAL
The document discusses the effect of temperature on aromatic yield from treated heavy naphthene from Bonga Aromatic crude. It was observed that increasing the temperature of the catalytic reformer leads to an increase in aromatic yield. Specifically, the aromatic yield increased from 23.46% volume at 430°C to 51.38% volume at 540°C. Additionally, higher temperatures resulted in changes to the reformate composition, with decreasing naphthenes and increasing aromatics.
These slides may be used for a part of Advanced level course in Chemical Reaction Engineering. I taught this course to Masters level students covering 1.5 credit hours.
1. The document describes a mathematical model developed to model esterification in a batch reactor coupled with pervaporation for producing ethyl acetate.
2. The model accounts for the reaction kinetics of esterification catalyzed by Amberlyst 15 resin and permeation rates of components through a polydimethylsiloxane membrane based on experimental data.
3. A parametric study using the model found that conversion increases with increasing temperature, molar ratios of reactants, and catalyst concentration, with optimal conditions being a temperature of around 343K, catalyst concentration of 10g, and 50% excess acetic acid relative to ethanol.
This document provides an overview of catalysis and catalytic principles. It defines catalysis as the science of catalysts and catalytic processes, which plays an important role in industries like petrochemicals. A catalyst enhances the rate and selectivity of a chemical reaction while being regenerated in the process. Key points discussed include:
- Catalysts are composed of an active phase (e.g. metal), support, and optional promoters. Common supports include metal oxides like alumina.
- Reaction rate depends on temperature, pressure, concentration, and contact time according to rate laws. Temperature particularly impacts reaction rates through its exponential effect in the Arrhenius equation.
- Mass transfer and internal diffusion limitations can
This document discusses using a pseudo-homogeneous CSTR simulation to model a fluidized bed reactor producing polyethylene via gas-phase polymerization including the effect of n-hexane co-solubility predictions using the Sanchez-Lacombe equation of state. The simulation considers an ethylene/nitrogen/n-hexane gas phase in equilibrium with an ethylene/polyethylene/n-hexane polymer phase. Results showed polyethylene production increased about 2% with 0.1 bar of n-hexane due to co-solubility effects. Reactor temperature decreased more sharply in condensed mode with each 0.1 bar increase in n-hexane pressure.
Kinetics in UP
This document discusses chemical kinetics and reaction rates. It defines key kinetics concepts like reaction order, rate laws, and rate constants. Specific examples covered include first-order, second-order, and zero-order reactions. The effects of temperature, catalysts, and physical conditions on reaction rates are also explained. Several industrial reaction mechanisms are summarized, such as the chlorination of methane, hydrolysis, nitration of benzene, and sulfonation of benzene.
Introduction
Basis
Importance
Classification
Homogeneous catalysis
Mechanism
Example
Heterogeneous catalysis
Mechanism
Examples
Promoters
Catalytic Poisoning
Autocatalysis
Enzyme catalysis
Enzymes
References
Catalyst: -
The substances that alter the rate of a reaction but itself remains chemically unchanged at the end of the reaction is called a Catalyst.
The process is called Catalysis.
prop-
A catalyst cannot start the reaction by itself.
Catalytic activity increases as surface area of catalyst increases.
Catalysts are thermolabile, this effect is very well pronounced in enzymes.
Catalytic activity is maximum at a catalyst’s optimum temperature.
A catalyst does not alter the position of the equilibrium, instead it helps in achieving the equilibrium faster.
Dynamic modeling and simulation of catalyticJhonatan Soto
This document summarizes a study on dynamic modeling and simulation of catalytic naphtha reforming. The dynamic model developed includes reaction kinetics, heat exchanger models, and furnace models. Kinetic modeling of the fixed bed reactors connected in series forms the core of the simulation. Reaction rates are represented using Hougen-Watson Langmuir-Hinshelwood expressions. Simulation results using MATLAB show fair agreement with plant data. The model can capture major dynamics in the reforming process system.
The Effect of Temperature on Aromatic Yield of Treated Heavy Naphthene From B...IJRESJOURNAL
The document discusses the effect of temperature on aromatic yield from treated heavy naphthene from Bonga Aromatic crude. It was observed that increasing the temperature of the catalytic reformer leads to an increase in aromatic yield. Specifically, the aromatic yield increased from 23.46% volume at 430°C to 51.38% volume at 540°C. Additionally, higher temperatures resulted in changes to the reformate composition, with decreasing naphthenes and increasing aromatics.
These slides may be used for a part of Advanced level course in Chemical Reaction Engineering. I taught this course to Masters level students covering 1.5 credit hours.
1. The document describes a mathematical model developed to model esterification in a batch reactor coupled with pervaporation for producing ethyl acetate.
2. The model accounts for the reaction kinetics of esterification catalyzed by Amberlyst 15 resin and permeation rates of components through a polydimethylsiloxane membrane based on experimental data.
3. A parametric study using the model found that conversion increases with increasing temperature, molar ratios of reactants, and catalyst concentration, with optimal conditions being a temperature of around 343K, catalyst concentration of 10g, and 50% excess acetic acid relative to ethanol.
This document provides an overview of catalysis and catalytic principles. It defines catalysis as the science of catalysts and catalytic processes, which plays an important role in industries like petrochemicals. A catalyst enhances the rate and selectivity of a chemical reaction while being regenerated in the process. Key points discussed include:
- Catalysts are composed of an active phase (e.g. metal), support, and optional promoters. Common supports include metal oxides like alumina.
- Reaction rate depends on temperature, pressure, concentration, and contact time according to rate laws. Temperature particularly impacts reaction rates through its exponential effect in the Arrhenius equation.
- Mass transfer and internal diffusion limitations can
Effects of heat treatment on the catalytic activity and methanol tolerance of...sunidevi
This document summarizes a study on the effects of heat treatment on the catalytic activity and methanol tolerance of carbon-supported platinum alloys. Carbon-supported platinum (Pt/C) and platinum alloy (Pt-Co/C, Pt-Cu/C, Pt-Fe/C, Pt-Ni/C) catalysts were subjected to heat treatments at different temperatures. X-ray diffraction, transmission electron microscopy, and electrochemical measurements were used to characterize the catalysts and evaluate their oxygen reduction reaction activity and methanol tolerance. The results showed that heat treatment improved catalytic activity by increasing particle size but the optimal temperature depended on the catalyst. Pt-Cu/C treated at 350°C showed the highest activity and
Alkylation of Diphenyl Oxide with Benzyl Alcohol over HZSM-5Ranjeet Kumar
The study investigated the alkylation of diphenyl oxide with benzyl alcohol over HZSM-5 zeolite catalyst. Experiments were conducted in a glass reactor at 120°C for 3 hours with a catalyst loading of 100kg/m3. Analysis showed the reaction produced an isomeric mixture of benzyl-diphenyl-oxide. Kinetic studies established the reaction as pseudo-first order and found the activation energy to be 26.74kJ/mol. The catalyst was determined to be reusable with a conversion decrease from fresh to first reuse.
This document summarizes a study on the catalytic dehydration of methanol to dimethyl ether over γ-alumina. The researchers investigated the effects of temperature and feed composition on the conversion of methanol and deactivation of the catalyst. They found that methanol conversion strongly depended on the reactor operating temperature, increasing with higher temperatures. Using pure methanol as a feed resulted in slow catalyst deactivation, while adding water to the feed increased deactivation significantly. A temperature-dependent model was developed to predict methanol conversion and reasonably correlated with experimental data.
This document discusses control of polymerization reactors. It outlines several key control problems including controlling reaction rates and temperature, monomer conversion and production rates, molecular weight and distribution, copolymer composition, and particle size and distribution. It then discusses various measurement techniques used for monitoring these properties, including viscosity, composition, surface tension, molecular weight distribution, and particle size distribution. Control is achieved through manipulation of parameters like temperature, feed rates, catalysts, and chain transfer agents.
This document summarizes research on converting lignin into liquid compounds through a solvolysis (alcoholysis) process. Lignin was heated to 270-300°C with an alcohol and acid in a high-pressure reactor. Key results include:
- Formic acid produced the highest pressures and yields of phenolic compounds, while acetic acid yielded mainly esters.
- Gas chromatography/mass spectrometry analysis showed the main products with formic acid were phenolic compounds, while acetic acid yielded esters like ethyl acetate and isopropyl acetate.
- Temperature reached 300°C within 75-90 minutes and pressure was regulated to not exceed 200 bars.
So in summary, this
The document discusses the design of catalyst reactors accounting for catalyst deactivation. It begins by introducing fixed bed and fluidized bed reactors. It then discusses criteria for selecting between these reactors, including catalyst deactivation behavior and reaction conditions. The document goes on to provide steps for designing catalyst reactors and single adiabatic packed bed reactors. It also discusses models for fluidized bed reactors and approaches for designing reactors to account for catalyst deactivation over time.
This document discusses reactor design for single chemical reactions. It compares the size and performance of batch, mixed flow, and plug flow reactors. For single reactions where product distribution is fixed, plug flow reactors generally require less volume than mixed flow reactors to achieve the same conversion. The size ratio of mixed to plug flow reactors depends on the reaction order and conversion level. Connecting reactors in series improves performance by making the flow more plug-like.
This document describes a computational fluid dynamics (CFD) study of methane decomposition into hydrogen and solid carbon in a packed bed fluid catalytic cracking (FCC) reactor. The study used CFD modeling in COMSOL Multiphysics to simulate the decomposition reaction over time in the packed bed reactor. Results showed that increasing the reaction time from 0 to 1000 seconds increased the production of hydrogen from 0 to 42 mol/dm3 and carbon from 0 to 21 mol/dm3, while decreasing methane concentration from 50 to 29 mol/dm3, indicating that decomposition was occurring. Spatial profiles of velocity, concentration, pressure and permeability within the reactor were also determined and discussed.
Kinetic And Mechanism of Oxidation of Cobalt Metal Complex By Acidic Potassiu...IJMERJOURNAL
ABSTRACT: The Kinetic of oxidation of Cobalt derived from 8-hydroxy quinolone and salicylaldehyde by potassium permanganate has been studied in the presence of acidic medium. The overall reaction is first order with respect to KMnO4, Substrate acid and temperature. No effect of salts has been found suitable mechanism is given.
Dynamic Modeling for Gas Phase Propylene Copolymerization in a Fluidized Bed ...IJRES Journal
The document presents a dynamic two-phase model for a fluidized bed reactor used to produce polypropylene. The model divides the reactor into an emulsion phase and bubble phase, with reaction assumed to occur in both phases. Simulation results show the temperature profile is lower than previous single-phase models due to considering both phases. Approximately 13% of the produced polymer comes from the bubble phase, demonstrating the importance of accounting for both phases.
- The document describes models developed for a fluid catalytic cracking fluidized bed reactor using a four-lump kinetic scheme.
- The reactor is modeled as a two-phase system consisting of a bubble phase modeled as plug flow and an emulsion phase modeled as continuous stirred-tank reactor.
- Kinetic rate equations are provided for the cracking of gas oil to gasoline, light gases, and coke based on the four-lump scheme. Mass balance equations are developed for each phase and solved numerically.
Dra Núria López - IN SITU SURFACE COVERAGE ANALYSIS OF RUO2-CATALYSED HCL OXI...xrqtchemistry
IN SITU SURFACE COVERAGE ANALYSIS OF RUO2-CATALYSED HCL OXIDATION REVEALS THE ENTROPIC ORIGIN OF COMPENSATION IN HETEROGENEOUS CATALYSIS - Nature Chemistry (29 July 2012)
Kinetic Study of Esterification of Acetic Acid with n- butanol and isobutanol...Hugo Balderrama
The document summarizes a study on the kinetics of esterification reactions between acetic acid and n-butanol or isobutanol catalyzed by ion exchange resin. The effects of temperature, catalyst loading, and initial molar ratios on reaction rates were examined. Activation energies for the reactions were determined to be 28.45 kJ/mol for n-butanol and 23.29 kJ/mol for isobutanol. The study found reaction rates increased with higher temperatures, catalyst loadings, and molar ratios of alcohol to acid.
Chain reactions in liquid phase polymerization can be initiated by thermal, photochemical, or radiation sources. While similar to gas phase chain reactions, liquid phase polymerization is affected by solvent non-ideality and the solvent plays a role in the chain length and final polymer structure. Free radical solution polymerization typically results in linear chains if a single radical is involved in each reaction step. Temperature can change the types of reacting radicals initiated in free radical polymerizations. Chain transfer processes transfer the growing polymer radical activity to another molecule like a monomer, initiator, or solvent, terminating the original chain and allowing the transfer agent to continue adding monomers.
Formulation and operation of a Nickel based methanation catalystSakib Shahriar
The objective of this experiment was to get a firsthand experience of the preparation of a catalyst for methanation reaction and to evaluate the performance of the catalyst in a fixed bed tubular reactor. In the first part of the experiment a nickel-based catalyst was synthesized. The catalyst will have nickel as the active component and alumina as the support. the catalyst precursor was prepared by co-precipitation from a solution of nitrate salts of nickel and aluminum. The precipitate was filtered out, washed, dried and calcined to obtain the catalyst. In the second part, the catalyst was activated and performance analysis was done alone with loaded in a fixed bed reactor. The percentage conversion of CO to CH4 was 96.38% and the selectivity of CH4 production to CO2 production was 3.348.
This document discusses the topic of chemical equilibrium. It provides an introduction to key concepts such as reversible reactions occurring at the same rate and the equilibrium constant. It also discusses factors that affect chemical equilibrium such as concentration, pressure, temperature and catalysts. Le Chatelier's principle is explained, which states that applying stress to a system at equilibrium causes it to counteract the change. Specific examples are provided to illustrate how changing concentration, pressure and temperature impacts the position of equilibrium.
Definition of reaction kinetics, law of mass action, rates of reaction- zero, first, second, pseudo zero & pseudo first order reaction, molecularity of reaction, determination of reaction order- graphic method, substitution method, half life method.
This document provides an overview of catalysis. It defines catalysis as a process where a substance called a catalyst alters the rate of a chemical reaction but remains unchanged. Catalytic reactions are classified as homogeneous if reactants and catalysts are in the same phase, or heterogeneous if they are in different phases. Common industrial applications of catalysis include the Haber process for ammonia production and the Contact process for sulfuric acid manufacture. Theories for catalytic mechanisms include intermediate compound formation and adsorption of reactants onto catalyst surfaces.
Ethika People Solutions provides various employee wellness programs and services that can result in benefits such as more engaged and productive employees, lower health care costs, reduced absenteeism and turnover, and improved organizational morale. Their solutions include health risk assessments, employee assistance programs, rewards and recognition tools, weekly wellness newsletters, and expert-led educational webinars on topics like nutrition, stress management, and work-life balance.
This document summarizes a study into how musicianship alters one's interaction with and perception of music. Through interviews with musicians, the study found that becoming a musician causes one to engage with music differently in several ways. Musicians now focus on individual instrumental parts and are able to identify specific notes and sounds. They also want to understand how the different musical parts fit together and translate what they hear to their own instruments. One musician noted starting to pick out these details more after his second year of classical guitar lessons. The findings suggest that musicianship fundamentally changes how one listens to and understands music.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
Blow out Bar - Interior Finishes final ProjectAmy Hill
This document provides conceptual sketches and design details for Mimi's Blowout & Beauty Bar. The goal is to create a luxurious and relaxing environment for services like facials, makeup, and hairstyling. On the main floor, an elegant contemporary design includes a marble reception desk, crystal chandeliers, and a waiting area with purple vinyl seating. The blow dry bar has semi-circular styling stations and dramatic elements like mirrored walls and a spiral floor. Upstairs, tranquil facial rooms have warm and relaxing atmospheres with acoustic wall panels. Materials like marble, glass, wood, and various flooring options create texture and visual interest throughout.
Effects of heat treatment on the catalytic activity and methanol tolerance of...sunidevi
This document summarizes a study on the effects of heat treatment on the catalytic activity and methanol tolerance of carbon-supported platinum alloys. Carbon-supported platinum (Pt/C) and platinum alloy (Pt-Co/C, Pt-Cu/C, Pt-Fe/C, Pt-Ni/C) catalysts were subjected to heat treatments at different temperatures. X-ray diffraction, transmission electron microscopy, and electrochemical measurements were used to characterize the catalysts and evaluate their oxygen reduction reaction activity and methanol tolerance. The results showed that heat treatment improved catalytic activity by increasing particle size but the optimal temperature depended on the catalyst. Pt-Cu/C treated at 350°C showed the highest activity and
Alkylation of Diphenyl Oxide with Benzyl Alcohol over HZSM-5Ranjeet Kumar
The study investigated the alkylation of diphenyl oxide with benzyl alcohol over HZSM-5 zeolite catalyst. Experiments were conducted in a glass reactor at 120°C for 3 hours with a catalyst loading of 100kg/m3. Analysis showed the reaction produced an isomeric mixture of benzyl-diphenyl-oxide. Kinetic studies established the reaction as pseudo-first order and found the activation energy to be 26.74kJ/mol. The catalyst was determined to be reusable with a conversion decrease from fresh to first reuse.
This document summarizes a study on the catalytic dehydration of methanol to dimethyl ether over γ-alumina. The researchers investigated the effects of temperature and feed composition on the conversion of methanol and deactivation of the catalyst. They found that methanol conversion strongly depended on the reactor operating temperature, increasing with higher temperatures. Using pure methanol as a feed resulted in slow catalyst deactivation, while adding water to the feed increased deactivation significantly. A temperature-dependent model was developed to predict methanol conversion and reasonably correlated with experimental data.
This document discusses control of polymerization reactors. It outlines several key control problems including controlling reaction rates and temperature, monomer conversion and production rates, molecular weight and distribution, copolymer composition, and particle size and distribution. It then discusses various measurement techniques used for monitoring these properties, including viscosity, composition, surface tension, molecular weight distribution, and particle size distribution. Control is achieved through manipulation of parameters like temperature, feed rates, catalysts, and chain transfer agents.
This document summarizes research on converting lignin into liquid compounds through a solvolysis (alcoholysis) process. Lignin was heated to 270-300°C with an alcohol and acid in a high-pressure reactor. Key results include:
- Formic acid produced the highest pressures and yields of phenolic compounds, while acetic acid yielded mainly esters.
- Gas chromatography/mass spectrometry analysis showed the main products with formic acid were phenolic compounds, while acetic acid yielded esters like ethyl acetate and isopropyl acetate.
- Temperature reached 300°C within 75-90 minutes and pressure was regulated to not exceed 200 bars.
So in summary, this
The document discusses the design of catalyst reactors accounting for catalyst deactivation. It begins by introducing fixed bed and fluidized bed reactors. It then discusses criteria for selecting between these reactors, including catalyst deactivation behavior and reaction conditions. The document goes on to provide steps for designing catalyst reactors and single adiabatic packed bed reactors. It also discusses models for fluidized bed reactors and approaches for designing reactors to account for catalyst deactivation over time.
This document discusses reactor design for single chemical reactions. It compares the size and performance of batch, mixed flow, and plug flow reactors. For single reactions where product distribution is fixed, plug flow reactors generally require less volume than mixed flow reactors to achieve the same conversion. The size ratio of mixed to plug flow reactors depends on the reaction order and conversion level. Connecting reactors in series improves performance by making the flow more plug-like.
This document describes a computational fluid dynamics (CFD) study of methane decomposition into hydrogen and solid carbon in a packed bed fluid catalytic cracking (FCC) reactor. The study used CFD modeling in COMSOL Multiphysics to simulate the decomposition reaction over time in the packed bed reactor. Results showed that increasing the reaction time from 0 to 1000 seconds increased the production of hydrogen from 0 to 42 mol/dm3 and carbon from 0 to 21 mol/dm3, while decreasing methane concentration from 50 to 29 mol/dm3, indicating that decomposition was occurring. Spatial profiles of velocity, concentration, pressure and permeability within the reactor were also determined and discussed.
Kinetic And Mechanism of Oxidation of Cobalt Metal Complex By Acidic Potassiu...IJMERJOURNAL
ABSTRACT: The Kinetic of oxidation of Cobalt derived from 8-hydroxy quinolone and salicylaldehyde by potassium permanganate has been studied in the presence of acidic medium. The overall reaction is first order with respect to KMnO4, Substrate acid and temperature. No effect of salts has been found suitable mechanism is given.
Dynamic Modeling for Gas Phase Propylene Copolymerization in a Fluidized Bed ...IJRES Journal
The document presents a dynamic two-phase model for a fluidized bed reactor used to produce polypropylene. The model divides the reactor into an emulsion phase and bubble phase, with reaction assumed to occur in both phases. Simulation results show the temperature profile is lower than previous single-phase models due to considering both phases. Approximately 13% of the produced polymer comes from the bubble phase, demonstrating the importance of accounting for both phases.
- The document describes models developed for a fluid catalytic cracking fluidized bed reactor using a four-lump kinetic scheme.
- The reactor is modeled as a two-phase system consisting of a bubble phase modeled as plug flow and an emulsion phase modeled as continuous stirred-tank reactor.
- Kinetic rate equations are provided for the cracking of gas oil to gasoline, light gases, and coke based on the four-lump scheme. Mass balance equations are developed for each phase and solved numerically.
Dra Núria López - IN SITU SURFACE COVERAGE ANALYSIS OF RUO2-CATALYSED HCL OXI...xrqtchemistry
IN SITU SURFACE COVERAGE ANALYSIS OF RUO2-CATALYSED HCL OXIDATION REVEALS THE ENTROPIC ORIGIN OF COMPENSATION IN HETEROGENEOUS CATALYSIS - Nature Chemistry (29 July 2012)
Kinetic Study of Esterification of Acetic Acid with n- butanol and isobutanol...Hugo Balderrama
The document summarizes a study on the kinetics of esterification reactions between acetic acid and n-butanol or isobutanol catalyzed by ion exchange resin. The effects of temperature, catalyst loading, and initial molar ratios on reaction rates were examined. Activation energies for the reactions were determined to be 28.45 kJ/mol for n-butanol and 23.29 kJ/mol for isobutanol. The study found reaction rates increased with higher temperatures, catalyst loadings, and molar ratios of alcohol to acid.
Chain reactions in liquid phase polymerization can be initiated by thermal, photochemical, or radiation sources. While similar to gas phase chain reactions, liquid phase polymerization is affected by solvent non-ideality and the solvent plays a role in the chain length and final polymer structure. Free radical solution polymerization typically results in linear chains if a single radical is involved in each reaction step. Temperature can change the types of reacting radicals initiated in free radical polymerizations. Chain transfer processes transfer the growing polymer radical activity to another molecule like a monomer, initiator, or solvent, terminating the original chain and allowing the transfer agent to continue adding monomers.
Formulation and operation of a Nickel based methanation catalystSakib Shahriar
The objective of this experiment was to get a firsthand experience of the preparation of a catalyst for methanation reaction and to evaluate the performance of the catalyst in a fixed bed tubular reactor. In the first part of the experiment a nickel-based catalyst was synthesized. The catalyst will have nickel as the active component and alumina as the support. the catalyst precursor was prepared by co-precipitation from a solution of nitrate salts of nickel and aluminum. The precipitate was filtered out, washed, dried and calcined to obtain the catalyst. In the second part, the catalyst was activated and performance analysis was done alone with loaded in a fixed bed reactor. The percentage conversion of CO to CH4 was 96.38% and the selectivity of CH4 production to CO2 production was 3.348.
This document discusses the topic of chemical equilibrium. It provides an introduction to key concepts such as reversible reactions occurring at the same rate and the equilibrium constant. It also discusses factors that affect chemical equilibrium such as concentration, pressure, temperature and catalysts. Le Chatelier's principle is explained, which states that applying stress to a system at equilibrium causes it to counteract the change. Specific examples are provided to illustrate how changing concentration, pressure and temperature impacts the position of equilibrium.
Definition of reaction kinetics, law of mass action, rates of reaction- zero, first, second, pseudo zero & pseudo first order reaction, molecularity of reaction, determination of reaction order- graphic method, substitution method, half life method.
This document provides an overview of catalysis. It defines catalysis as a process where a substance called a catalyst alters the rate of a chemical reaction but remains unchanged. Catalytic reactions are classified as homogeneous if reactants and catalysts are in the same phase, or heterogeneous if they are in different phases. Common industrial applications of catalysis include the Haber process for ammonia production and the Contact process for sulfuric acid manufacture. Theories for catalytic mechanisms include intermediate compound formation and adsorption of reactants onto catalyst surfaces.
Ethika People Solutions provides various employee wellness programs and services that can result in benefits such as more engaged and productive employees, lower health care costs, reduced absenteeism and turnover, and improved organizational morale. Their solutions include health risk assessments, employee assistance programs, rewards and recognition tools, weekly wellness newsletters, and expert-led educational webinars on topics like nutrition, stress management, and work-life balance.
This document summarizes a study into how musicianship alters one's interaction with and perception of music. Through interviews with musicians, the study found that becoming a musician causes one to engage with music differently in several ways. Musicians now focus on individual instrumental parts and are able to identify specific notes and sounds. They also want to understand how the different musical parts fit together and translate what they hear to their own instruments. One musician noted starting to pick out these details more after his second year of classical guitar lessons. The findings suggest that musicianship fundamentally changes how one listens to and understands music.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
Blow out Bar - Interior Finishes final ProjectAmy Hill
This document provides conceptual sketches and design details for Mimi's Blowout & Beauty Bar. The goal is to create a luxurious and relaxing environment for services like facials, makeup, and hairstyling. On the main floor, an elegant contemporary design includes a marble reception desk, crystal chandeliers, and a waiting area with purple vinyl seating. The blow dry bar has semi-circular styling stations and dramatic elements like mirrored walls and a spiral floor. Upstairs, tranquil facial rooms have warm and relaxing atmospheres with acoustic wall panels. Materials like marble, glass, wood, and various flooring options create texture and visual interest throughout.
Grand Goa Exotica is a hotel, located in North Goa, the most happening place on the planet.
We've spacious rooms, multi-cuisine restaurant, swimming pool, bar along with life size chess board and billiards, to make your vacation a memorable one.
This 3 slide presentation provides a brief overview. Slide 1 acts as an introduction. Slide 2 continues the presentation. Slide 3 concludes the presentation.
This document summarizes the state of the solar industry in Arizona in 2015. It finds that while the US solar industry grew 20.2% in 2015, adding over 35,000 jobs, Arizona saw a 24.5% reduction in solar jobs. Solar capacity additions in Arizona have stagnated since 2012, installing just 141 MW in 2015, less than neighboring Nevada. Utility-scale solar makes up most new capacity but the residential and commercial markets have struggled due to policy changes reducing the economics of rooftop solar.
Trabajo en grupo: Deporte, ejercicio físico y estilos de vidaGabrielcano92
El documento distingue entre deporte, ejercicio físico y estilos de vida, y describe los beneficios de cada uno para la salud. Ambos el deporte y el ejercicio físico previenen enfermedades, pero el deporte también fomenta la competitividad y es más popular entre los hombres. Los estilos de vida saludables conducen a menor riesgo de enfermedad y más energía. Finalmente, se discuten trastornos como la anorexia y la bulimia que ponen en duda la relación entre actividad física y salud.
Improving the prevention, recognition and management of AKI: the ‘Think Kidne...Renal Association
The "Think Kidneys" initiative aims to reduce preventable harm from acute kidney injury (AKI) through various workstreams including risk identification, education, detection, measurement, intervention, and implementation. The program will develop tools and interventions to better prevent, detect, treat, and manage AKI. It will also work to ensure patients who develop AKI receive appropriate care to avoid further deterioration, long-term issues, and death. A key goal is having various guidelines and educational resources adopted across healthcare settings to standardize AKI care.
This document discusses work health and safety responsibilities for horse clubs and organizations in South Australia. It explains that most horse sport and recreation activities fall under the jurisdiction of the Work Health and Safety Act through affiliation with state or national bodies or by employing workers like judges or contractors. It emphasizes that committee members are responsible for providing a safe working environment and managing risks through processes like hazard identification, assessment, and implementing control methods. The document provides examples of record keeping, training, safe work procedures, first aid, and control measures that clubs can use to comply with their health and safety obligations.
This CV summarizes Hanu Wilsenach's personal and professional experience. He currently works as a Branch Manager at Plasticland, and has over 10 years of experience in retail management, logistics, and administration roles in South Africa and Rwanda. His education includes a Bachelor of Business Administration degree from UNISA. He is proficient in Afrikaans and English.
The document describes the development of a dynamic model of an industrial packed bed multi-tubular reactor used for producing ethylene oxide. Ethylene oxide is produced through the catalytic oxidation of ethylene with oxygen over a silver-based catalyst. The model is developed using a system of non-linear partial differential equations and is benchmarked against plant data from an industrial ethylene oxide reactor. Both a heterogeneous two-phase model and a reduced homogeneous single-phase model are considered and compared against plant data.
The document describes the development of a dynamic model of an industrial packed bed multi-tubular reactor used to manufacture ethylene oxide through the catalytic oxidation of ethylene with oxygen. A system of non-linear partial differential equations is used to model the highly exothermic gas phase reactions. The model is benchmarked against plant data and reasonably predicts the reactor behavior. The heterogeneous two phase model is reduced to a single phase homogeneous model for simplicity. A comparison shows the homogeneous model provides accurate predictions of the reactor performance.
Study on Coupling Model of Methanol Steam Reforming and Simultaneous Hydrogen...IOSR Journals
1) A simplified mechanistic model was developed for coupling methanol steam reforming and hydrogen combustion in microchannels of a parallel plate reactor. The reforming reaction is endothermic and requires heat, which is provided by the exothermic hydrogen combustion reaction in an adjacent channel.
2) Kinetic expressions were used to model the reforming and combustion reactions. MATLAB simulations were performed to analyze parameters like temperature, velocity and conversion. Operative diagrams showed the temperature and velocities required for complete methanol conversion.
3) Efficiency curves were generated based on hydrogen produced versus consumed. With a molar ratio of 0.9664, the maximum efficiency was 86.8%, indicating over 80% efficiency is achievable via coupling of
An insight into spray pulsed reactor through mathematical modeling of catalyt...Siluvai Antony Praveen
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Kinetics of the Hydrolysis of
Atmospherically Relevant
Isoprene-Derived Hydroxy Epoxides
N E I L C . C O L E - F I L I P I A K ,
A L I S O N E . O ’ C O N N O R , A N D
M A T T H E W J . E L R O D *
Department of Chemistry and Biochemistry, 119 Woodland
Street, Oberlin College, Oberlin, Ohio 44074
Received June 4, 2010. Revised manuscript received July
16, 2010. Accepted July 19, 2010.
Isoprene (the most abundant nonmethane hydrocarbon
emitted into the atmosphere) is known to undergo oxidation to
2-methyl-1,2,3,4-butanetetraol, a hydrophilic compound
present in secondary organic aerosol (SOA) in the atmosphere.
Recent laboratory work has shown that gas phase hydroxy
epoxides are produced in the low NOx photooxidation of isoprene
and that these epoxides are likely to undergo efficient acid-
catalyzed hydrolysis on SOA to 2-methyl-1,2,3,4-butanetetraol at
typical SOA acidities. In order to confirm this hypothesis, the
specific hydroxy epoxides observed in the isoprene photooxidation
experiment (as well as several other related species) were
synthesized, and the hydrolysis kinetics of all species were
studied via nuclear magnetic resonance (NMR) techniques. It
was determined that the isoprene-derived hydroxy epoxides
should undergo efficient hydrolysis under atmospheric conditions,
particular on lower pH SOA. An empirical structure-reactivity
model was constructed that parametrized the hydrolysis
rate constants according to the carbon substitution pattern on
the epoxide ring and number of neighboring hydroxy functional
groups. Compared to the previously studied similar nonfunc-
tionalized epoxides, the presence of a hydroxy group at the R
position to the epoxy group was found to reduce the hydrolysis
rate constant by a factor of 20, and the presence of a hydroxy
group at the beta position to the epoxy group was found to
reduce the hydrolysis rate constant by a factor of 6.
Introduction
Because secondary organic aerosol (SOA) is known to play
a critical role in issues such as air pollution (1) and climate
change (2), there continues to be intense interest in the
formation mechanisms for these particles. Isoprene,
the dominant non-methane hydrocarbon emitted into the
atmosphere (3), has only recently been implicated in SOA
formation. In 2004, Claeys et al. identified 2-methyl-1,2,3,4-
butanetetraol in SOA found in air samples from the Amazon
and inferred that it must be an oxidation product of isoprene
(4). Several laboratory an.
2. Journal of Engineering for Rookies 1 (2014) 58-68
2
Thermodynamic models like Sanchez-Lacombe have given
strong answers on it. This local/micro-scale phenomena
increases kinetics that, in turn, will lead to bigger reactor
productions. That’s what it will be confirmed in this study
with ICA n-hexane.
2. Science and engineering needed
As already mentioned, the feed stream of polyethylene in
a FBR is a mixture of different components with different
functionalities. So for more realistic modelling it should be
included at least ternary phase in polymer solubility species
studies. Some thermodynamics models have been tested to
predict and account ethylene solubilization. The Sanchez-
Lacombe (SL) equation of state (EOS) [1] is one of the most
applied models in simulation of polymer phase
thermodynamics [2]. In this work it will be used its most
lately results concerning ethylene solubility and
concentration in growing polymer phase when it’s present n-hexane.
Several studies for LLDPE production have included
particle growth models that led to a better understanding of
the reactor behavior as well as properties of the polymer
produced. Modelling at the particle level requires not only
thermodynamics but naturally transfer phenomena too.
Nevertheless it has been established in the literature that,
under many conditions, heat transfer and diffusional
resistances do not play an important role at the particle level
in gas-phase polyethylene reactors when it is already in a
mature/developed state [3]. Under this statement, and since it
meets the purposes of this work, it will be considered only
thermodynamics. Deeper considerations are in topic 2.1.
Modelling fluidized-bed polymerization reactors is not
simple since many interactions between phases need to be
taken into account. The fluidized reactor model mostly
accepted relies on Kunni & Levenspiel fluidized bed
theory [4]. In their model, the gas flows up the reactor in the
form of bubbles exchanging gas with reactive particles (like
catalysts) in a called emulsion phase. The product formed in
these particle then returns back into a bubble and leaves the
bed when it reaches the top of the reactor. The fluidized bed
reactors for LLDPE production have been modelled as single,
two, or three-phase reactors. In topic 2.2 will be discussed the
single-phase modelling once it’s the similar approach mode
used in this work, despite the simple pseudo-homogeneous
steady-state CSTR admitted here has no mass and heat
transfer concerns nor even accurate FBR’s description as
well.
2.1. Sanchez-Lacombe n-hexane co-solubility effect
prediction
The rate law of ethylene polymerization adopted in this
thesis is the one proposed by Floyd [5]. It’s a simple catalytic
single-site and first order rate with respect to the ethylene
concentration at the active sites of catalyst. Formally, the
local rate of polymerization inside a polymer particle can be
expressed as:
Rp.loc – local ethylene polymerization rate
kp – kinetic constant rate
C* – local concentration of active sites in a catalyst fragment
C*
et. – ethylene local concentration in the polymer phase
surrounding some catalyst fragment
To predict satisfactorily the ethylene concentration in
amorphous polymer phase, C*
m in eq. 1, a thermodynamic
model has to be capable of detecting the effect of n-hexane
on the ethylene solubility and polymer swelling. The figure 1
illustrates a polymer particle in a ternary system. The particle
surrounded by a gas phase (a) is zoomed until a catalyst
fragment surrounded by produced semi-crystalline
polyethylene (b) which in turn is zoomed until a mix of
polymer chains are viewed to be immobilized on the surface
of catalyst fragment (c). Both ethylene (red) and n-hexane (in
blue) are present.
Figure 1 – Schematic representation of ethylene-n-hexane-polyethylene
ternary system at different scale levels. (Alizadeh A. , 2014, Figure 4.3)
Hutchinson and Ray [6] have developed thermodynamic
models to predict equilibrium monomer concentrations at the
catalyst sites from external gas-phase monomer
concentrations in the vicinity of the polymer particles. Kosek
[3] explored the advantage of the steady-state modeling as the
possibility of dependence of temperature and concentrations
in the particle on model parameters. He found that for many
catalyst systems in which heat and mass transfer resistances
do not influence monomer concentrations and temperatures
within the polymer particles, the monomer concentration at
the catalyst sites is determined by the equilibrium sorption of
the monomer within the polymer particles.
Yang [7] measured the solubility of ethylene/isopentane
and ethylene/n-hexane in semicrystalline PE of crystallinity
of 48.6%, at temperatures of 70, 80, and 90°C, 2 MPa total
pressure, 80–190KPa isopentane pressure and 20–90KPa n-hexane
pressure. He concluded isopentane and n-hexane
increase the solubility of ethylene in the corresponding
ternary system. On the contrary, the solubility of isopentane
or n-hexane remains unchanged with an increase of the
ethylene partial pressure.
Bashir et al. [8] used SL EOS predictions in the
multicomponent system of ethylene/1-hexene/LLDPE-1-
hexene mixture at 70°C, 90°C and 150°C. Their predictions
were in good agreement with the experimental data. They
also noted the solubility enhancement is co-monomer-type
dependent.
Alizadeh [9] extended the application of Sanchez-
Lacombe EOS from the binary system of ethylene/PE to the
ternary system of ethylene/n-hexane/PE in order to describe
the change in concentration of ethylene in the amorphous
phase of polyethylene. He fitted his SL predictions with the
sorption equilibrium data acquired by group of Yang [7] by
adjusting the binary interaction parameters (kij). Yang’s team
used some commercial LLDPE at three equilibrium
* *
Rp,loc. kpC Cm (1)
3. Journal of Engineering for Rookies 1 (2014) 58-68
3
temperature of 70, 80, and 90 °C, up to 20 bar total pressure and up to 1 bar n-hexane. In a global conclusion, the trend predictions of ternary SL model area according to Yang’s group experimental data but they have outputted some overestimation of the solubility of both ethylene and n- hexane (except for ethylene solubility at 90 °C and 5bar total pressure). But as the equilibrium temperature increases, the predicted solubility magnitude overestimation for both ethylene and n-hexane is decreased.
2.2. Gas-phase ethylene polymerization in a FBR and condensed-mode operation
The polymerization of ethylene on supported catalyst in gas phase FBR’s is the most common process for production of LLDPE. A small amount of high activity catalyst particles, with diameter of 10–50μm, is supplied continuously or semi- continuously to the reactor carried by nitrogen. Before they enter the reactor, they can be pre-activated and/or prepolymerized. Catalyst injection rates are in the range of 0.001- 0.05 g/s depending on catalyst activity and reactor capacity. Since the catalyst particles are the smallest/less dense in the reactor they move upwards. But at the same time they are moving upward, they are increasing their size due to the polymerization. The gas feed should be designed in order to not elutriate the particles having in account their maximum weight (which depends on their residence time). As these catalyst particles are exposed to monomer or monomer mixture in the reactor, polymerization occurs almost immediately and the catalyst particles are quickly encapsulated by the newly- formed polymers to a size of around 300–1000μm. Their sizes (naturally depending on their residence time in the reactor) range from the initial catalyst particle diameter to the large particle in the bed, composed by that time mostly of polymer. In the first stage of particle life, the polymer starts to fill the pores of the supported catalyst particle and a gradual fragmentation of the catalyst support takes place. However, the fragments are kept together by the polymer. The time-scale of the fragmentation process ranges from fractions of a second to a few seconds. The reaction heat is dissipated from the growing polymer particles by a fast growing gas stream. Fully-grown polymer particles are withdrawn continuously or intermittently from the bottom portion of the reactor (above distributor plate) while keeping the bed level approximately constant. The superficial gas velocity can vary from 3 to 8 times the minimum fluidization velocity [10]. Since very high fluidizing gas velocity is used for heat removal purpose, the monomer conversion per pass is quite low (<5%) and a large amount of unreacted gas containing an inert gas leaving the reactor is cooled, compressed, and recycled back to the reactor. An inert hydrocarbon liquid may also be added to the recycle gas stream to increase the reactor heat removal capacity (condensed mode operation) and hence to increase the polymer throughput. Overall conversion is about 98% [11]. Industrial fluidized bed reactors typically operate at temperatures of 75-110°C and pressures of 20-40 bar [12]. The pressure drop across the bed is slightly higher than the weight of the particles divided by the cross sectional area.
In case of low to moderate activity of the catalyst, heat transfer and diffusion resistances do not play an important role at the particle level in the gas-phase polyethylene reactors. In the limiting case, where either bubbles are small or interphase mass and energy transfer rates are high and catalyst is at low to moderate activity, intraparticle temperature and concentration gradients are negligible [5]. In this case, LLDPE production fluidized bed reactors could be modelled as a CSTR proposed by McAuley et al. [11], [12]. He considered the polymerization reactor to be a well-mixed reactor (CSTR). For this to be a well-mixed reactor, the mixing index should be near by 1 [13]. McAuley et al. revised Choi and Ray's model [14]. In both works, the emulsion phase is assumed to behave as a CSTR fully mixed. This assumption is good for small fluidized-beds that are violently fluidized and have a height to diameter ratio close to one, as it was demonstrated by Lynch and Wanke [15]. However for a typical ethylene polymerization reactor, mixing index is about 0.4-0.5. This indicates a low reactor mixing and makes a single CSTR a not very realistic approach. Alizadeh et. al. [16] employed a tanks-in-series model to represent a pseudo- homogeneous model for predicting the performance of an industrial-scale gas-phase polyethylene production reactor. Weijuan et al. [17] simulated the steady-state behavior of industrial slurry polymerization of ethylene in 2 continuous stirred tank reactors. The model demonstrated that changing the catalyst flow rate, changes simultaneously the mean residence-time in both reactors, which plays a significant role on the establishment of polyethylene architecture properties such as molecular mass and polydispersity index.
The condensed mode operation in the gas-phase fluidized bed ethylene polymerization process increases the space-time yield of polymer production. The cooling capacity of the recycle gas stream is increased by addition of non- polymerizing condensable agents in order to increase the dew-point temperature of the stream. An even further increasing in cooling capacity is achieved in the super- condensed mode operation [18]. This is actually a mean of expanding the plant capacity without resizing the reactor. Ramanathan [19] used a CSTR with a polymer phase very well-mixed and a residence-time for polymer particle of several hours. The catalyst was present in the polymer phase and the solubility of monomers and other reactants were predicted by SL. In his simulation with 3 different catalysts he concluded that the polymer produced, cooler duty and the amount of condensation in recycle stream are the same for dry or wet mode. There is about 160 % increase in productivity if 10 mole % of liquid is present in the recycle stream. Mirzaei [20] used Peng-Robson EOS for flash calculations to evaluate the liquid fraction as well as the gas and liquid composition in the inlet stream to the reactor. For polymer particles, he used SL EOS in order to calculate the concentration of monomers, hydrogen and condensable components from the concentration of the components in the
Figure 2 – Gas-phase FBR illustration for ethylene polymerization
4. Journal of Engineering for Rookies 1 (2014) 58-68
4
gas phase. Their results were according to some patent they
used for comparison.
Alizadeh and Mckenna [21] thought the liquid to
evaporate at hot spots in the bed. Parameters like droplet size,
size distribution, heat of vaporisation and properties of solid
particle phase as well as eventual contact between these two
phases will control the overall vaporisation process of the
liquid droplet in the presence of fluidising solid particles.
They analysed time scales for droplet heat up and
vaporisation compared in case of homogenous vaporisation
of the droplet. Based on their assumptions and calculations
they expected the major part of the liquid injected through the
bottom of an FBR to vaporise at a height of between 1 and
2m. Since the evaporation process is quite rapid, the gas
phase will be quite rich in the heavier ICA and so the
polymer.
3. Reactor model
The reactor model developed in this work consists in a
pseudo-homogeneous CSTR type. It’s assumed that all bed
operates in such approach. There are no concerns about mass
or heat transfer phenomena nor real fluidizing bed reactor
characteristics. Based on this, it will be assumed a simple
model in steady-state that can give important indications on
how the reactor temperature and polyethylene mass rate
vary with different hexane pressures and for different sets of
conditions such as different kinetic constants, kp, catalyst
flowrates, Qc.0, and inflow temperatures, T0.
First, all the assumptions for this reactor simulation will
be enumerated. Then the model equations are written and
briefly commented. Finally the results of simulations are
shown in plots and discussed. In the end it’s made a sensible
analysis to some parameters of balance equations to check
which are the ones that may strongly twist the results.
3.1. Assumptions
Single-phase CSTR approach
1 inlet gas flowing containing a mixture of ethylene, n-hexane
and nitrogen
1 inlet solid flow containing the catalyst
1 outlet gas flow containing ethylene, n-alkane and all
nitrogen
1 outlet solid flow containing the polymer phase which
includes catalyst, polyethylene, dissolved ethylene and
n-hexane. Dissolved nitrogen in the particle is negligible
and it’s considered to be zero.
Equilibrium is instantaneous and particles are mature (no
mass or heat transfer phenomena in every volume of
reactor and particles)
The absorbing latent heat species (n-hexane and
ethylene) do it instantaneously
Elutriation of solids is neglected at the top of the bed
No pressure gradient or even difference pressure between
reactor inlet and outlet
The catalyst particle size is spherical shape and mono-dispersed
Fast catalyst activation
Spherical and Constant mean particle size
The reacting volume is the catalyst volume, Vc. There’s
an inflow of catalyst and an inflow of gas of ethylene, n-hexane
and nitrogen. The outflows are composed by the
polymer phase and the gas not reacted and not dissolved as
well in polymer phase. The reactor is also characterized by a
bed height, hb, and a base area, b.
3.2. Model Equations
The model equations consist essentially in a steady-state
polyethylene mass balance and a global heat balance in a
CSTR approach. They are exposed in the next lines as well
as the terms constituting them.
- Polyethylene Mass Balance (PEMB)
The polyethylene production, mPet., is evaluated in mass
balance according to:
The reaction rate, Rp, is an extrapolation of eq.1 for
every particle in the reactor. It’s an average polymerization
rate.
The concentration of ethylene in polymer phase, Cet.
p, is
a function of hexane pressure. Its variation was predicted in
Alizadeh work [9] with SL EOS and such data is in table 2.
The kinetic constant, kp, has an Arrhenius temperature
dependence:
The catalyst active concentration, C*, is obtained
through a mass balance to the active moles of catalyst in the
reactor:
Solving for C* and with catalyst outflow, Qc, equal to
catalyst inflow, Qc.0:
The deactivation constant, kd, has also an Arrhenius
temperature dependence:
- Heat Balance (HB)
Left eq. 8 term respects to the polymerization heat, middle
one represents sensible heat and right one denotes global heat
Rp(T,P)Vc m Pet 0 (2)
et
p
Rp(T,P) kp(T )C Cet (P)M .
* (3)
R T T
E
T
p p
a
k T k e
1 1
exp . exp . ( )
(4)
Qc 0C0 QcC kd T C Vc 0 * * *
. ( ) (5)
0
0
1
.
*
*
( )
c
c
d
Q
V
k T
C
C
(6)
R T T
E
T
d d
d
k T k e
1 1
exp . exp . ( )
(7)
0 0
0 0 T
v
L
Pet g p g p p p
T
Hr m T T m c . m c . F H
(8)
5. Journal of Engineering for Rookies 1 (2014) 58-68
5
vaporization term. This one, F0
LΔHv, is the weighted sum of
n-hexane and ethylene vaporization rate contributions:
The amount of liquid hexane (Fhex.0
L) and ethylene (Fet.0
L)
in eq. 9 were estimated, for the work temperatures and
pressures, with Redlich-Kwong-Soave (RKS) equation of
state (in Aspen®). The inflow stream gas should enter the
reactor in a liquid-gas equilibrium mixture. And once inside,
it should vaporize totally (and instantaneously). To know
what are the appropriate thermodynamic conditions for the
inlet flows, so that their content can vaporize at the reactor
pressure and temperature, it’s necessary phase equilibria data.
The numerical mass liquid fractions predicted for this work
are shown in table 2.
The hexane vaporization heat is estimated by a Watson
type correlation [22]. For ethylene vaporization heat it was
used the ethylene thermodynamic EOS predictions of
Smulaka [23] by fitting his results at 10bar pressure.
Corresponding expressions are in eq. 10 and eq. 11
respectively.
A small caveat about ethylene presence in vaporization
process and its vaporization heat correlation (eq.11) shall be
said. Although ethylene is clearly a gas in normal pressure
conditions, it was included in vaporization phenomena
simply because that’s what RKS model predicted at work
conditions. And to maintain consistency, it was assumed to
be also in gas-liquid equilibrium. For example, RKS model
estimates there is about a 10-15% liquid ethylene fraction in
the range of work conditions. Concerning ethylene heat
vaporization, at 10bar total pressure it boils at -53.15°C.
Using eq. 11 out of the temperature range is admitting a
pseudo-liquid state for ethylene at higher temperatures. It
may not be the most corrected consideration but assumed the
prediction of RKS model of an ethylene liquid state in the
working conditions it makes necessary to have some
estimation of it.
The outlet gas mass, mg, in eq. 8 is the sum of the three
existing gases:
And each of its terms are (through specie mass balance):
With ethylene and hexane dissolved mass in polymer
phase, met.d and met.d respectively, equal to:
Met. and Mhex, are ethylene and hexane molar masses.
In what concerns polymer mass term, mp, in eq. 8 it is the
sum of polyethylene mass rate, mPet., catalyst mass rate, mc,
and ethylene plus hexane dissolved mass rate in polymer
phase, met.d and mhex.d respectively:
With the proper algebra and substitutions, the final mass
and heat balance system is:
With initial inlet gas mass rate, mg.0:
The letter f in eq. 19 is abbreviating the following
quantity:
To calculate the bed volume, Vb, polymer particle
volume, Vp and catalyst volume, Vc, it was used:
The reactor base area, b, and bed height were fixed. With
it, bed volume, Vb, is straightforward (eq. 22) as well as
polymer particle volume, Vp, (eq. 23) at some typical
fluidizing porosity, ε. The diameter and height of the
fluidized bed reactor were adjusted to be in a usual range of
industrial reactors. According some patents they are [10-
15]m for bed height and [2.44-4.4]m for bed diameter [24].
In turn, the catalyst volume, Vc, needed for this particle
volume was calculated assuming particles are spherical
shaped and assuming each catalyst particle will turn into
0 0 0
0 0 0
T
v et
L
et
T
v hex
L
hex
T
v
L F H F H F H . . . . . . (9)
342 480
507 43
45 61 1
0 401
, ( )
.
.
.
. . T K
T
Hv hex (10)
98 15 53 15
10 0 0202 72 836 112 72 2
. ( ) .
. .( ) . . . ,
T K
Hv et bar T T (11)
m g m et. m hex. mN2 (12)
met. met.0 met.d mPet. (13)
mhex. mhex. mhex.d
0 (14)
mN2 mN2.0 (15)
.
. .
. Pet
p
et
p
et
et d m
C M
m
(16)
.
. .
. Pet
p
hex
p
hex
hexd m
C M
m
(17)
mp mPet. mc met.d mhex.d
(18)
p p p g
Tr
g p g c p p
T
v
L
Pet
c
p
et
Tp
Pet
H T T f c c
F H T T m c m c
HB m
PEMB m k T C C V
. .
. . .
.
*
. :
. ( )
0
0 0 0
:
(19)
m g.0 m et.0 m hex.0 mN2.0 (20)
1 1
p
hex
p
hex
p
et
p
et C M C M
f
. . . . (21)
Vb bhb d hb 1 2 4 (22)
Vp Vb1 (23)
c p
p
c
c c c p n n
d
d
V n d V
6
3
3 ,
(24)
6. Journal of Engineering for Rookies 1 (2014) 58-68
6
each polymer particle. So total number of polymer particles,
np, are equal to the total number of catalyst particles, nc.
The catalyst volume finally comes the eq. 24. The
catalyst and particle diameter, dc and dp, were adjusted
according reference values. They are [30-50]μm for catalyst
particle and [300-1000]μm for polymer particle [12].
The volumetric inlet gas flowrate, Qg.0, is useful to
check the proper range of superficial gas velocity value:
With eq. 26 and the base area of reactor fixed, the
superficial velocity of gas, ug.0 is:
According some patents [24], [25] these velocities are
around 0.48<ug.0<1 m/s.
The average particle residence time, σp, is defined as the
quotient between particle volume in the rector, Vp, and the
volumetric inflow rate, Q0, which comprises catalyst
volumetric inlet rate, Qc.0, and gas volumetric inlet rate that
contributes to polymerization, Qg.0’. Q0 is numerically the
same as the polymer volumetric outlet rate, Qp.
The bulk density of the fluidized bed, ρ, is estimated
by:
mb is the mass of the bed. Reducing eq. 29:
3.3. Data tables
The left side of table 1 contains the thermodynamic and
catalyst parameters established by Alizadeh in his work [9].
They are used in the current simulation. The right side shows
the parameters and numerical volumes concerning reactor.
Table 2 contains, in first left half, equilibrium data for
the concentration of ethylene and n-hexane in polymer
phase. The original data was extracted from Alizadeh work
[9] and it consisted in 4 predictions of the mentioned
concentrations at 4 hexane pressures – 0.2, 0.3, 0.6 and 0.8
bar. These values were interpolated in order to have a more
continuous range of hexane pressures. The correlation
obtained was also extrapolated for 0.9 and 1.0bar hexane. The
2nd right half of the table shows the mass liquid fraction,
mliq., of inlet stream at 40, 45 and 50°C, predicted by Redlich-
Kwong-Soave (RKS) equation of state. It is also indicated the
dew-point at given conditions. Below 0.40 bar n-hexane
(including) there’s no liquid phase (dew-point is below the
inlet flow temperature). On the other hand, the maximum
percentage of liquid mass in the flow is at 1bar hexane. At
40°C inlet flow, there is no liquid until hexane pressure
reaches 0.5bar. From this level until 1 bar hexane, the amount
of liquid is always increasing. At 45°C, only at 0.60 bar
hexane pressure starts to exist liquid in inlet flow. Finally the
50°C temperature flow only starts to have liquid at 0.70 bar
hexane pressure. The liquid quantity fractions, at the same
hexane pressure, decreases with increasing temperature.
Table 3 displays the Simulation I results. It fixes total
molar flow, F, inlet temperature, T0, and catalyst flowrate,
Qc, for 3 different values of referential kp. The simulation
results table show polyethylene mass rate, mPet., reactor
temperature, T, ethylene conversion, %Conv.,
polymerization rate, Rp, superficial gas velocity, ug.0, and
average particle residence time, σp. The mPet. and T are
represented in plots in topic 3.4. Besides Simulation 1, there
is Simulation 2 and Simulation 3. Their numerical output are
omitted and they’re only represented in plots (in terms of
mPet. and T). Thereat, the characteristics of such simulations
and discussions on their results are exposed.
Table 1
General parameters/constants used in simulations. General thermodynamic and catalyst parameters were extracted form Alizadeh work.
General thermodynamic parameters Reactor Parameters
Texp. (°C) Pet. (bar) PN2 (bar) d (m) b (m2)
80 7.00 1.00 4.0 12.6
Cp.c (J.kg-1.K-1) (-ΔHr
80°C) (J/molet.) Cp.p (J.kg-1.K-1) hb (m) Vb (m3)
2000 107 600 2000 10.7 134
Catalyst parameters ε dp (μm)
kd
80°C
(s-1) Ed (kJ/mol) Ea (kJ/mol) 0.55 500
1.00x10-4 42 42 Vp (m3) dc (μm)
ρc (kg/m3) C0
* (mol/m3
c) 60.4 30
2300 0.55 Vc (L)
13
3 6 3
6
Vp np dp np Vpdp
(25)
g
g
g
m
Q
0
0
.
.
(26)
b
Q
u
g
g
0
0
.
. (27)
p
p
c g
p p
Q
V
Q Q
V
Q
V
0 .0 .0'
(28)
b
b p b g
b
b
bh
bh bh
V
m
1
(29)
p g p (30)
8. Journal of Engineering for Rookies 1 (2014) 58-68
8
3.4. Plot simulation results
The simulation 1 fix total molar flow, F, inlet temperature, T0, and catalyst flowrate, Qc, for 3 different values of kp80°C.
In the particularly set of conditions with kp80°C=1200m3Petmol-ac.-1.s-1 one can see there are no values for 1bar hexane pressure. This is a particular case of thermodynamic constraint. The dew point of such inflow is above the reactor temperature. So there is no total vaporization making the gas-phase to have a different composition from the intended one.
The progress of curves in figure 3 show an increasing polyethylene rate production (about 2.5% relative variation) with increasing hexane pressure/concentration in polymer phase. Moreover, curves appear to have a smaller relative variation in production as the hexane pressure increases, especially from starting of condensing mode. The 3 curves differ in propagation constant rate, kp80°C. Higher ones leads naturally to bigger production rates. The figure 4 shows a global decreasing temperature with increasing hexane pressure. From 0 to 0.4bar hexane pressure, the temperature gradually decreases (about 1.5% relative variation) due to heat capacity of gases and after it, a more abrupt lowering of temperature (about 8% relative variation) proceeds thanks to heat vaporization of condensed hexane (and ethylene). Polyethylene mass rate relative variation increases during dry-mode operation and then it starts to decrease. This is pronouncedly for set of kp80°C = 1200 m3mol-site-1s-1. As the hexane pressure increases, the liquid amount gets higher and the reactor temperature will drop due to considerable cooling capacity. At a certain value of hexane pressure, the reactor temperature gets too low and kinetics is clearly affected. For the other kp’s, since they are bigger, the related productions are more “slowly” affected.
For the 3 kp’s tested there are an average relative variation between them of about 15% for polymer production. For temperature, there’s a relative variation of about 10% (in condensed-mode). It’s also noticed a trend of decreasing of production and temperature relative variation between kp’s with increasing kp. This is, in the kp’s presented, the biggest relative variations occurred between simulation sets of kp’s = 1200 m3mol-site-1s-1 and kp’s = 1350 m3mol-site-1s-1.
In the simulation 2 (figures 5 and 6) there are 3 catalyst flow rates (Qc.0) tested.
This simulation appears to have similar trends to the simulation 1. But here, because catalyst flowrates has not the same impact on temperature as kinetic constant, kp, the highest relative variation between them is for production. For the three catalyst flow rates (Qc) tested, there are a relative variation between them of about 9% for polymer production and 7% for temperature when reactor operates in condensed- mode. Since this relative variations are quite the same as the case of simulation 1, this may lead to the question of what preferably to boost: catalyst kinetic constant or catalyst flowrate for analogous productivity?! The cost factor might be the natural “decision variable”. But in principle, catalyst kinetic constant in not immediately available to change unlike the catalyst flowrate. Temperature decreases with a smooth rate until 0.4bar hexane pressure and from this value on, it has a pronounced decreasing. For example, for Qc.0 =
Figure 4 – Reactor temperature result simulation 1 given the conditions in plot title. Numerical data is in table 3
Figure 3 – Polyethylene mass rate steady-state simulations 1 results given the condition in plot title. Numerical output is in table 3.
Figure 5 – Polyethylene mass rate steady-state simulations 2 results given the conditions in plot title.
Figure 6 - Reactor temperature result simulation 2 given the conditions in plot title.
0
2
4
6
8
10
0
0,2
0,4
0,6
0,8
1
Pet. (ton/h)
PHex.(bar)
SIMULATION 1 -Production
Qc,0= 0.222g/s; F = 2000mol/s; T0= 40°C
Kp(80°C) = 1200m3/mol-site.s
Kp(80°C) = 1350m3/mol-site.s
Kp(80°C) = 1500m3/mol-site.s
0
20
40
60
80
100
120
140
0
0,2
0,4
0,6
0,8
1
T (°C)
PHex.(bar)
SIMULATION 1 -Temperature
Qc,0= 0.222g/s; F = 2000mol/s; T0= 40°C
Kp(80°C) = 1200m3/mol-site.s
Kp(80°C) = 1350m3/mol-site.s
Kp(80°C) = 1500m3/mol-site.s
0
2
4
6
8
0,2
0,4
0,6
0,8
1
Pet. (ton/h)
PHex.(bar)
SIMULATION 2 -Production
kp80°C= 1200m3Pet.mol-site-1.s-1; T0= 40°C; F = 1800mol/s
Qc0 = 0.222 g/s
Qc0 = 0.236 g/s
Qc0 = 0.250 g/s
40
60
80
100
120
140
0,2
0,4
0,6
0,8
1
T (°C)
PHex.(bar)
SIMULATION 2 -Temperature
kp80°C= 1200m3Pet.mol-site-1.s-1; T0= 40°C; F= 1800mol/s
Qc0 = 0.222 g/s
Qc0 = 0.236 g/s
Qc0 = 0.250 g/s
9. Journal of Engineering for Rookies 1 (2014) 58-68
9
0.236g/s, from 0.2-0.4bar hexane pressure, the average rate of decreasing is about 1.5% and from 0.5 bar on is about 8%.
Simulation 3 results (figure 7 and 8) are lastly shown.
Figure 7 shows there’s small production difference especially between curves T0 = 45°C and T0 = 50°C. Actually before condensing mode (<0.5bar hexane), production is quite the same for 3 curves. Concerning case with T0 = 40°C, it starts to deviate from the others at 0.5bar hexane (its condensed mode beginning). The production increases with hexane pressure, although moderately, and it seems to stabilize (and eventually even to decrease) near by the biggest hexane pressure tested (1.0bar). The other two curves start, in turn, to deviate from each other around 0.6bar hexane (starting cooling capacity for 45°C T0 curve). Their individual progress show an increasing polyethylene rate production with increasing hexane concentration in polymer phase. For example, for T0 = 45°C, the rate of polyethylene increasing is about 2.4% in average. Temperature decreases at a considerable rate with increasing hexane pressure. For example, for T0 = 45°C, the average rate of decreasing is about 6%. They have pointedly more productivities with increasing hexane pressure when compared with 40°C T0 case. This clearly remarks the cooling capacity influence in polymer production. 40°C T0 curve will have a too high liquid content and it’ll quickly make production to decrease. On the other side, for example 45°C T0 curve has less liquid content and it will allow bigger productions not only due to higher temperatures but also because hexane pressure is higher and its co-solubility effect will be more active. For the three inlet flow temperatures there is very high temperature relative variation between them. For example at 0.8bar hexane, when inlet temperature changes from 45°C to 50°C, there is a temperature relative variation of about 15%. And it is even higher between 40°C and 45°C (about 18%). These variations appear to decrease with increasing inlet temperature and increasing hexane pressure
This set of simulation indicates that differences in inlet temperature make substantial changes in production and reactor temperature. Basically, this happens because there’s a big changing in flow composition in terms of liquid portion when the temperature changes, at least, 5°C (for instance, from 40 to 45°C). Even though hexane pressure gets higher – enhancing co-solubility effect and production in addition – if the liquid content in inlet flow is too high, it will soften the reaction.
3.5. Sensible analysis
The steady-state model simulated in this work naturally involves some physical quantities. And some of them may not be properly estimated for the work temperature and/or pressures. The sensible analysis will provide the information on equation balances terms that may have bigger deviations. Those ones should deserve more attention in the future for having better predictions and consequently allow accurate reactor simulations. The parameters were tested by varying its original simulation numerical value in a certain amount (percent) and observing the impact on the the polyethylene mass rate relative variation, ΔmPet (%) and reactor temperature relative variation, ΔT (%). The parameters “perturbed” are those at 0.6bar hexane and 0.9bar hexane conditions, both related to Simulation 1 results.
The sensible analysis for ethylene vaporization heat, ΔHv,et. and heat capacity of polymer phase, Cp,p, do not have a relevant influence in model output. They were considerably perturbed in 200 and 100% respectively varying only - 0.67% and -0.50% in production for 0.6bar hexane condition. In opposite direction, solely 5% ethylene concentration in polymer phase, Cet. p, perturbation leads to relative variation of 5.73% in production and 3.82% in reactor temperature. For example, a mere 5% Cet. p deviation would mean changing from 97.41mol/m3p to 102.3mol/m3p. It’s just a small difference but it has a big impact in polyethylene production and in temperature as seen before. This emphasizes the importance of acquiring good predictions for this quantity.
Reaction enthalpy, ΔHr, hexane equilibrium gas fraction in inlet stream, yhex. T0 and hexane vaporization heat, ΔHv.hex., make reasonable changes in temperature. When they are, for the following order, perturbed in 10, 15 and 20% they alter the reactor temperature in 6.50, 5.00 and -3.0°C. With the largest difference in temperature from the original values comes gas heat capacity, Cp.g. deviation. When it varies 20%, the reactor temperature changes about -9.7°C. This may be explained with the fact the gas flowrate crossing the reactor is very big. There’s in consequence a big amount of sensible heat and heat capacity becomes a sensible parameter in the context of this analysis
Conclusions
A gas-phase ethylene polymerization reactor working in condensed mode was simulated using a simple pseudo- homogeneous CSTR model. The main purpose was to
Figure 7 – Polyethylene mass rate steady-state simulations 3 results given the conditions in plot title
Figure 8 – Reactor temperature result simulation 3 given the conditions in plot title
5
6
7
8
0,4
0,5
0,6
0,7
0,8
0,9
1
Pet. (ton/h)
PHex.(bar)
SIMULATION 3 -Production
F = 2000mol/s; kp80°C=1500m3Pet.mol-site-1.s-1; Qc.0=0.200g/s
To = 40°C
To = 45°C
To = 50°C
40
60
80
100
120
140
0,4
0,6
0,8
1
T (°C)
PHex.(bar)
SIMULATION 3 -Temperature
F = 2000mol/s; kp80°C=1500m3Pet.mol-site-1.s-1; Qc.0=0.200g/s
To = 40°C
To = 45°C
To = 50°C
10. Journal of Engineering for Rookies 1 (2014) 58-68
10
analyse the impact of n-hexane (ICA) in productivity and reactor temperature. The model included a simple approach composed by a single-site kinetics where the first-order ethylene concentration was predicted by Sanchez-Lacombe EOS. The particular aspect here was using an ethylene solubility Sanchez-Lacombe prediction for the ternary system – ethylene, n-hexane and polyethylene. This way the simulations for polymer production and reactor temperature were taking into account the co-solubility effect of n-hexane.
A global evaluation of simulations indicates an increasing of about 2% of production as the n-hexane pressure increases 0.1bar while there’s no too much cooling capacity able to ease kinetics. With respect to temperature, there’s a significant decreasing of about 8% when the reactor is operating in condensed-mode in contrast with only 1.5% when it is operating in a dry regime. At some point of inlet liquid content – associated with higher hexane pressures – the heat removal makes the reaction temperature to fall down too much and kinetics is diminished.
The simulations tested different kinetic constants (kp), different catalyst flowrates and different inlet gas temperatures. The changing of kinetic constants led to a relative variation between them of 15% for production and 10% for temperature. Changing the catalyst flowrate meant a relative variation of 9% for production and 7% for temperature. On the other way, when the inlet stream temperature is changed, the polymer production is differently trended: for the lowest inlet stream temperature, production grows less and decreases faster. The other two inlet temperatures tested seem to be more production maximized given the operation conditions.
From the sensitive analysis, the main parameters causing bigger deviations are hexane vaporization heat - influencing productivity and temperature, gas heat capacity – influencing productivity and temperature, vapour composition of inlet flow gas – influencing temperature, as well as polymerization heat influencing a lot temperature. The concentration of ethylene in polymer phase have a pronounced impact on production and temperature.
It would be interesting to simulate the model with other alkanes with different heat capacities and co-solubility effects than from those of n-hexane, namely isopentane and n- butane. In addition, for similar co-solubility and heat removal behaviour, economic and n-alkane easier degasing operation from polymer particles may also be a factor for ICA’s choosing. As it was referred, n-hexane has a very high solubility in polyethylene compared with other similar n- alkanes. This will promote the co-solubility effect (positive) but it also intensifies the degasing operation of polymer particles (negative).
The reactor simulations in this thesis are based on a very simple reactor model. Continuing the current work will mean adopting more realistic reactor models working in a transient mode where they can combine not only mature polymerization times but also initial ones (with related kinetics). Catalyst size distribution as well as catalyst residence time should incorporate such models since industrial catalyst particles are not all uniform in their size and they remain different times in the reactor. This factors affect kinetics and productivity/temperature by extension. Howsoever the results obtained here were suitable for reproducing the effect of the ICA n-hexane in PE productivity and temperature and they may be also a comparison basis for other works in this field.
References
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