Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Biodiesel production process

3,845 views

Published on

Biodiesel production process

Published in: Science

Biodiesel production process

  1. 1. Biodiesel production using chemical and biological methods – A review of process, catalyst, acyl acceptor, source and process variables B. Bharathiraja, M. Chakravarthy, R. Ranjith Kumar, D. Yuvaraj, J. Jayamuthunagai, R. Praveen Kumar, S. Palani Presented By: Bijaya K. Uprety PhD (Biotechnology) student
  2. 2. Introduction Biodiesel has gained good reputation in the catalogue of renewable energy Produce reduced toxic emission and can be blended with diesel and used in conventional engines too Its direct use into vehicle  impossible due to higher viscosity, low volatility & reactivity of unsaturated hydrocarbon chains present 1
  3. 3. In 1990 Scientist found ways to reduce viscosity and molecular weight of vegetable oil Most notable one were 1. Pyrolysis 2. Tranesterification Pyrolysis  expensive and yield of undesirable products. Hence, research was extensively made on the transesterification and resulting fuel was called as biodiesel. 2
  4. 4. Chemically, it is known as Fatty Acid Alky Esters (FAAE) and the alkyl group is decided by the acyl acceptor used for the reaction Compared to vegetable oil 1/3rd reduction in MW, 1/10th reduction in viscosity and contains 10- 11% oxygen (w/w) which enhances its combustion process The versatility of the biodiesel  various methods by which it can be produced commercially It can be done by varying any one of the following: (i) Oil/Fat source (ii) Catalyst (iii) Acyl acceptor and (iv) Solvent 3
  5. 5. Biodiesel Production Produced by transesterification (also called as alcoholysis) is the reaction of fat or oil with an alcohol to form esters and glycerol. Usually a catalyst is used to mediate the reaction and bring out quicker reaction rate 1. Acid catalyst 2.Base catalyst 3. Enzyme catalyst After transesterification of triglycerides, the products are a mixture of esters, glycerol, alcohol, catalyst and tri-, di- and mono-glycerides. 4
  6. 6. Typical Production of Biodiesel from veg. oil 1.http://www.lct.ugent.be/sites/default/files/events/Lecture%202%20Studies%20on%20esterification%20of%20Free%20Fatty%20 Acids%20in%20biodiesel%20production.pdf. If feedstock contain <4% FFA: Trans-esterification reaction: Oil + Alcohol  Ester + Glycerol Catalyst: NaOH, KOH, & carbonates, H2SO4, HCl, lipases etc. (Acid catalyzed rxn is slow). If feedstock contains >4% FFA: i. Before trans-esterification, FFAs are converted into soaps and removed from the Oil (triglycerides). ii. Application of the Acid Catalysis method to trans-esterify the triglycerides & esterify the FFAs in parallel in the same reactor. 5
  7. 7. Acid catalyzed process The transesterification process is catalyzed by acids and these catalysts give very high yields of alkyl esters, but the reactions are very slow The homogeneous acid catalysts are H2SO4, HCl, BF3, H3PO4 and some organic sulfonic acids  upto 99% conversion has been reported When excess of acid is added, better conversion of triglyceride is obtained Advantage: Direct biodiesel production from low cost lipid feed stocks, such as waste cooking oil, greases etc. These oil sources have FFAs level of 46% 6
  8. 8. Generally, liquid based acid catalyst are used Acid addition  protonation of the carbonyl group of the ester  results in carbocation Produces the tetrahedral intermediate (after a nucleophilic attack of the alcohol )  which eliminates glycerol to form the new ester and regenerates the catalyst H+ 7 Reaction Mechanism
  9. 9. 8 Protonation Carbocation Tetrahedral intermediate Removal of glycerol & regeneration of proton
  10. 10. Advantage of Solid heterogeneous acid catalysts Insensitive to FFA content of the oil so regular removal of biodiesel and by-product from the reactors not required Enabling easy recovery and reuse of solid catalyst which in turn reduces corrosion problems Disadvantage  The reactions are slow  Typically requires temperatures above 100 °C  Requires more than 3 h to reach complete conversion 9 Solid heterogeneous acid catalysts have the potential to replace liquid acid catalysts
  11. 11. Alkali catalyzed process Most widely used homogeneous base catalysts are NaOH, CH3ONa and KOH Presence Moisture enhance soap formation  consumes the catalyst and reduces the efficiency & increase viscosity Reactions with alkali catalysts are found to perform quick than the acid catalyzed reactions Standard value of the reaction to take place is 60 0C, but depending on the oil source and catalyst, different degrees of conversion is obtained at various temperature ranging from 25 to 120 0C Heterogeneous solid alkali catalysts are basic zeolites, alkaline earth metal oxides and hydrotalcites 10
  12. 12. The first step is the reaction of base with the alcohol, producing an alkoxide and the protonated catalyst The nucleophilic attack of the alkoxide at the carbonyl group of the triglyceride generates a tetrahedral intermediate, from which the alkyl ester and the corresponding anion of the diglyceride are formed The latter deprotonates the catalyst, thus regenerating the active species, which is now able to react with a second molecule of the alcohol, starting another catalytic cycle. Diglycerides and monoglycerides are converted by the same mechanism to a mixture of alkyl esters and glycerol 11
  13. 13. 12 Alcohol Base Alkoxide Protonated catalyst Nucleophilic attack of alkoxide at carbonyl group Tetrahedral intermediate Alkyl ester Anion of diglyceride Deprotonation Reacts with another alcohol for new cycle
  14. 14. Super critical methanol process A fluid is considered supercritical when its temperature and pressure go above its critical point They can effuse through solids like gas and dissolve materials like liquid Problems with transesterification process • Time consuming process • Separation of catalyst and Saponified impurities • Reduced catalyst efficiency & its high consumption 13
  15. 15. SCM have hydrophobic nature with a lower dielectric constant form a single phase oil/methanol mixture Since the reaction is catalyst free, purification of biodiesel is easy, environment friendly and completes in 2–4 min These problems are eliminated in the non-catalytic supercritical methanol method of transesterification Saka and Kusdiana preheated methanol (350 0C, 24 h) enough to convert rape seed oil to methyl esters 14
  16. 16. Hence it is not a viable option for industry level commercialization The uses of co-solvents such as carbon dioxide, hexane, propane, etc. are being investigated to reduce the operational parameters and make the process economical Yield of methyl esters increases with increase in molar ratio of oil to methanol Due to severe reaction conditions and high operational costs, this method suffers few disadvantages 15
  17. 17. Enzyme catalyzed transesterification – lipases Lipase dependent catalysis have certain advantages over conventional catalysis Use of lipase easy removal of glycerol by-product and environmentally friendly Problem with alkali based catalyst- Difficult glycerol recovery & treatment of highly alkaline waste water Extracted Lipase and some Lipase producing Microorganisms (mostly Fungi) are immobilized in biomass support particles and used as catalytic beds to obtain prolong use Commercial names of lipases are Novozym, Lipolase, Lipozyme, Lipomax, Lumafast 16
  18. 18. 17
  19. 19. A. Extracellular lipase Extracellular enzyme catalysis Requires Downstream processing technique (enzyme extraction) & Immobilization to ensure repeated use Preparation of lipase solution Commercial Lipase (0.5 g) + 5.0 ml of water (stirred for 1 h) followed by centrifugation at 3500g for 10 min Supernatant was used as enzyme solution after dilution with water 18
  20. 20. Immobilization of lipase enzyme and optimization Many techniques and different carriers have been employed for immobilization of lipases to produce biodiesel Carrier used: Both hydrophilic and hydrophobic Commonly used: Kaolite particles, macroporous resin, functionalized nanoscale SiO2 spheres Most lipases exist in two confirmations an open (dominative in hydrophobic interface) and a closed confirmations (dominative in water) 19
  21. 21. The covalent attachment of lipase on styrene-divinyl benzene- polyglutaraldehyde support has been found to be twice stable than lipase immobilized on to styrene-divinylbenzene beds by hydrophobic interactions In closed conformation Flap exposes hydrophilic side  towards water and hydrophobic side towards catalytic side In presence of triglyceride the hydrophobic part of lipase (catalytic site) changes in confirmation, opens and adsorbs the substrate in open configuration 20
  22. 22. B. Intracellular lipase or whole cell biocatalyst for biodiesel fuel production Use of extracellular lipase expensive due to downstream process Some of the species of lipase producing microorganisms having the ability to act as whole cell biocatalyst have been studied Rhizopus oryzae, Mucor meihei , Candida antartica, Candida rugosa and Candida cylindracea  Studied for their use as whole cell biocatalyst 21
  23. 23. B1. Whole cell immobilization or bed preparation Immobilized R. oryzae cells were the first whole cell biocatalysts used in the process of transesterification Cells were cultivated under normal conditions and then immobilized within biomass support particles (BSP) In some cases immobilized culturing of cells has been carried out 22
  24. 24. Hama grew R. oryzae in 100 ml basal media (30 0C, 24 hr) For immobilized cell culturing Transferred to air lift bioreactor (30 0C) 101 Basal medium with olive oil (30 g/l) and 24,000 Biomass support particle (BSP) Aeriation  cause liquid & particle mixing After cultivation, the BSP immobilized cells were separated from the culture and stabilized (packed bed reactor or bottle flask) 23
  25. 25. Use of novel acyl acceptors in lipase catalyzed process Apart from the regular acyl acceptors like methanol and ethanol, researchers have also proposed the use of other novel acyl acceptors such as methyl acetate, ethyl acetate and dimethyl carbonate Use of excess lower chain alcohols deactivation of the immobilized lipase Use of less amount of methanol or use of Alternative solvents such as hexane and t-butanol  Can solve the problem Use of Alt. solvents is expensive 24
  26. 26. Use of Methyl acetate Du et al. Replaced alcohol with methyl acetate High yield (92%, molar ratio of oil: methyl acetate: 1:12) was obtained The yield was obtained for crude and refined soybean oil 25
  27. 27. Use of Ethyl acetate Lipase B from C. antartica immobilized on acrylic resin reacted with crude oil of Jatropha, Karanj and Sunflower oil in presence of ethyl acetate Yield of 91.3%, 90% and 92.7% resp. obtained Molar ratio; EA/oil : 11/1 Temp: 50 0C, 12 hr By-product obtained was triacetin, a valuable molecule which has wide spread application 26
  28. 28. Use of dimethyl carbonate For use of methyl acetate and ethyl acetate large amount of compound is required (1:12 of oil/methyl acetate; 1:11 of oil/ethyl acetate) DMC is a neutral, odorless, cheap, non corrosive, non-toxic compound that exhibits good solvent properties With DMC reaction remains in positive product formation side (Biodiesel) as the product is CO2 which escapes as gas. 27
  29. 29. Process variables Basic parameters that are considered to affect the conversion rates Type of lipase Type of substrate Temperature & pH Water, solvent & glycerol content Molar ratio of substrates Purity of reactant 28
  30. 30. Selection of lipase/organism Selection of the lipase mainly depends on  Whether the system is a solvent involved system/solvent independent system Type of fatty acid involved  The lipase is to be used intra-cellular or extra-cellular along with other reaction parameters 29
  31. 31. An organic solvent such as n-hexane, s-butanol, petroleum ether are added to a system Increase the miscibility between the triglyceride and methanol  Increasing the catalytic efficiency of lipase Reactions can also be carried out in a solvent free system Lipases from various microbes give various results in different systems Triacyl glycerol (TAG) and free fatty acids (FFA) present in the oil decides the activity of the lipase Specificity of lipases for biodiesel synthesis refers to their region specificity or specificity with respect to the length of hydrocarbon chain of fatty acid 30
  32. 32. Whole cell biocatalysts are considered better  cheaper Disadvantage of reduced conversion rates compared to immobilized lipases The lipases selected for the catalysis are those that display wide substrate specificity. Examples are lipases from pseudomonas and candida species 31
  33. 33. Selection of Substrates for biodiesel production Selection of Lipids source Selection of solvents Selection of acyl acceptors  Proper selection of source important  High amount of phospholipid in the oil gives low flame: lipase pretreatment, oil degumming/ dewaxing required  Refined oil gives higher yields but it is costly  Methanol, ethanol, isopropanol  Iso-butanol, 2-butanol and 1-butanol  methyl acetate, ethyl acetate and di methyl carbonate Ideal solvent should ensure the good solubility of oil and alcohol & also maintain the enzyme stability (so mixture of solvent better) 32
  34. 34. Glycerol effect Glycerol formation Influence the transesterification process by inactivating the enzyme Inactivation of enzymes could be due to 1. Formation of hydrophilic coating of glycerol  due to binding of glycerol to supporting matrix where lipase is bound reduce the access of enzyme to TAG 2. Decrease in the water activity of the enzyme Glycerol has to be continuously removed  Add hydrophilic compounds such as silica gel to the system  Washing immobilized lipase after transesterification with isopropyl alcohol 33
  35. 35. Conclusion Though many plants and microbes are known to produce oil, most of them are not able to produce oil sustainably Production of biodiesel involves different methods Use of biological catalyst has recently got interest but still at naïve stage Various process variables should also be considered many researches are ongoing to optimize each of the production steps 34

×