1. Definition of The Project
A Methane to Acetic acid plant is to be set up at Brammanbaria in Bangladesh having a capacity
of 300 ton 99% Acetic Acid per day, corresponding to 109500 ton of 99%Acetic Acid per
year, and an intermediate capacity of 450 ton of 91.5% Methanol per day corresponding to ton
of 16500 tons 91.5% of Methanol per year including all offsites, auxiliaries, utilities and
supporting facilities using Industrial Grade Methane (96.48% CH4) fromTitas Gas Field as
raw material.
2. Product & Raw material
Specifications
Acetic Acid, CH3COOH:
Acetic acid,systematically named ethanoic acid,is an organic compound.It is a colourless liquid
that when undiluted is also called glacial acetic acid. Acetic acid has a distinctive sour taste and
pungent smell.
Liquid acetic acid is a hydrophilicprotic solvent, similar to ethanol and water. It dissolves not
only polar compounds such as inorganic salts and sugars, but also non-polar compounds such as
oils and elements such as sulfur and iodine. It readily mixes with other polar and non-polar
solvents such as water, chloroform, and hexane. With higher alkanes (starting with octane),
acetic acid is not completely miscible anymore, and its miscibility continues to decline with
longer n-alkanes. This dissolving property and miscibility of acetic acid makes it a widely used
industrial chemical, for example, as a solvent in the production of dimethyl
terephthalate.Although it is classified as a weak acid, concentrated acetic acid is corrosive and
can attack the skin.
Table 1.1:Properties of CH3COOH:
Molecular formula CH3COOH
Molar mass 60.05 g·mol−1
Appearance Colourless liquid
Odor Pungent/Vinegar-like
Density 1.049 g cm−3
Melting point 16 °C; 61 °F; 289 K
Boiling point 118 °C; 244 °F; 391 K
Solubility in water Miscible
log P -0.322
Acidity (pKa) 4.76
Basicity (pKb) 9.198 (basicity of acetate ion)
Refractive index (nD) 1.371
Viscosity 1.22 mPa s
Dipole moment 1.74 D
Specific
heat capacity (C)
123.1 J K−1
mol−1
3. Std molar
entropy (So
298)
158.0 J K−1
mol−1
Std enthalpy of
formation (ΔfHo
298)
-483.88--483.16 kJ mol−1
Std enthalpy of
combustion (ΔcHo
298)
-875.50--874.82 kJ mol−1
Methanol, CH3OH:
Methanol, also known as methyl alcohol,wood alcohol, wood naphtha or wood spirits. It is
the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a pleasant smell . It
is highly toxic and unfit for consumption. At room temperature, it is a polar liquid, and is used as
an antifreeze, solvent, fuel, and as a denaturant for ethanol.
Table 1.2: Properties of Methanol
Molecular formula CH3OH
Molar mass 32.04 g·mol−1
Appearance Colorless liquid
Density 0.7918 g·cm−3
0.7925 g·cm−3
@20°C
Melting point −97.6 °C (−143.7 °F; 175.6 K)
Boiling point 64.7 °C (148.5 °F; 337.8 K)
log P -0.69
Vapor pressure 13.02 kPa (at 20 °C)
Acidity (pKa) 15.5[3]
Refractive index (nD) 1.33141[4]
Viscosity 0.545 mPa×s (at 25°C) [5]
Dipole moment 1.69 D
Flash point 11 to 12 °C (52 to 54 °F; 284 to 285 K)
Autoignition
temperature
385 °C (725 °F; 658 K)
Explosive limits 6%-36%
4. Availability of Raw Materials:
CH4: Bought from Titas Gas Field, Brammanbaria
H2O (cooling, treated, DM water, etc.): Available in Bangladesh.
Raw material specification
Natural Gas from Titas Gas Fiel
5. Process Selection
Methane to Methanol conversion process
Catalytic Conversion
Features:
Conversion of methane to methanol with an economic yield of 10%
In most experiments with solid catalysts, selectivities to methanol fell rapidly as methane
conversions exceeded 59%
complete oxidation of methane to carbon dioxide (ΔH = -877 kJ/mol) is highly favored
over partial oxidation of methane to methanol (ΔH = -200 kJ/mol)
A noticeable progress, however, has been made in the field of molecular catalysis by
Periana et al., who demonstrated the selective conversion of methane to methanol at
temperatures around 473 K over platinum bipyrimidine complexes. According to their
experiment, 81% selectivity to methyl bisulfate, a methanol derivative, was reached at
methane conversion of 90% in concentrated sulfuric acid
Although these results are promising, commercial applications are hampered by difficult
separation and recycling of the molecular catalyst.
Thermal Cracking
Methane is converted to methanol by partial oxidation to hydrogen gas and carbon
monoxide (synthesis gas or syngas) at high temperatures normally several hundred
degrees celsius
Syngas is then catalytically converted to methanol over a copper or platinum surface, also
at a couple hundred degrees Celsius
It is only around five or ten percent efficient due to accidental total oxidation to carbon
dioxide and water.
Photo-Catalytic Conversion
Ultraviolet light breaks water into a hydrogen and hydroxyl free radical, which are highly
reactive. When a hydroxyl radical reacts with a methane molecule, a hydrogen is
displaced and methanol is produced.
6. With the use of tungsten oxide or a similar semiconductor, photons of lower energy than
ultraviolet (down to blue) can be used.
Using Of WO₃ as photo-catalyst visible laser light can be used in room temperature
It is highly energy inefficient (only 2-3% efficiency)
The process is not out in commercial production yet
Biological conversion
Conversion combines both methane and ammonia streams using methane-oxidizing
bacteria and ammonia-oxidizing bacteria, in both wild type and genetically modified
forms
Can convert heterogeneous methane feedstocks, unlike existing commercial process
Does not require a pure source of methane
It does not require expensive chemical catalysts
Cleanup and dehumidification processes not required
Widely applicable to digester gas, landfill gas, peatbogs, marshes, and wastewater
treatment facilities
Conversion process is time consuming
ICI process
Catalyst: Copper-Zinc oxide catalyst
Temperature: 200-30000
C
Pressure: 5-10 MPa
Activity of this catalyst is more sensitive to impurities (poisoning)
Reduced manufacturing costs.
7. Methanol to Acetic acid
Cativa Process
Process developer: BP chemicals
Catalyst: Iridium/iodide catalyst
Improved catalyst stability
Allowing operation at low water concentrations
High reaction rates
Reduced formation of liquid by-products
Improved yield on carbon monoxide
Temperature:
Pressure:
Monsanto process
Process developer: Monsanto
Temperature: 150-2000
C
Pressure: 30-60 bar
Catalyst: rhodium/iodide catalyst
Selectivity: 99%
To prevent rhodium loss the reactor composition is maintained within limits on water,
methyl acetate, methyl iodide and rhodium concentrations
High H2O concentrations to prevent catalyst precipitation and maintain high reaction
rates
BASF process
Catalyst: cobalt /iodide catalyst
Temperature: 2500
C
Pressure: 680 bar
Selectivity: 90% (based upon methanol)