Alkali-catalyzed biodiesel production processes

Generally, alkali-catalyzed transesterification is performed near the boiling point of the alcohol, but several researchers have reported high conversion yield at room temperature (8,14). Low reaction temperature was desirable, since reaction temperature was closely related to the energy cost of the biodiesel production process. 

The problems caused by high free fatty acid content in low quality oils, which may cause interference in biodiesel production using alkali catalysts, could be overcome using an acid-catalyzed process. However, acid catalysis has shown some inconveniences, such aslower yields than thosereached by alkali catalysis, need of high temperatures and more corrosiveness than other processes (Meher et al., 2006 Akoh et al., 2007). 

Although immobilization can reduce the overall production cost, the overall cost is still much higher than that of chemical-catalyzed processes. Jegannathan et al. (2011) determined the economic feasibility of producing 1000 tons of biodiesel from palm oil using alkali and lipase catalysts in both soluble and immobilized forms. The alkali-catalyzed process cost was found to be lowest followed by the immobilized form of the lipase. However, in this research it was assumed that lipase could be reused only five times. If reusability is increased, the lipase processes becomes more feasible. 

In terms of biodiesel conversion processes, chemical conversion using alkali and acid-based catalysts is stiU the most favorite approach. Various investigations have been carried out to develop novel catalysts and/or novel processes for efficient conversion of TAG to FAME. This part was reviewed in the chapter Production of biodiesel via catalytic upgrading refining of sustainable oleageneous feedstocks. The chapter Biochemical catalytic production of biodiesel introduced a promising alternative way of biodiesel production via enzyme-catalyzed processes. Recentiy, microalgae... 

Several processes for the production of biodiesel fuel have been developed by acid-, alkali-, and enzyme-catalyzed transesterification reactions (7-10). Transesterification, called alcoholysis, is the displacement of alcohol from an ester by another alcohol in a process similar to hydrolysis. Transesterification is represented by a number of consecutive and reversible reactions. The reaction step is the conversion of triglycerides to diglycerides, followed by the conversion of diglycerides to monoglycerides and of monoglycerides to glyceride at each step (11,12). 

Biodiesel (fatty acid methyl esters) is an alternative and renewable energy source, the development of which is hoped to reduce global dependence on petroleum, as well as air pollution. Biodiesel generated Ifom a variety of vegetable oils and animal fats has characteristics similar to those associated with petro-diesel, including viscosity, volumetric heating value, cetane number, and flash point [1-3]. Several processes have thus far been developed for the production of biodiesel via acid-, alkali-, and enzyme-catalyzed... 

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