Review of Catalytic Transesterification Methods for Biodiesel Production

3. Heterogeneousversus homogenous catalysis

Catalyst fundamentally has a place with the classifications of homogeneous or heterogeneous. Homogeneous catalyst act in a soluble stage from the blend, while heterogeneous catalyst act in an alternate stage from the response blend. The outline of reactant process is given in Figure 2. Being in an alternate stage, heterogeneous impetuses have the upside of simple partition and reuse [17].

Heterogeneous catalyst is supplanting homogeneous catalyst because of hurdles in catalyst separation and waste disposal. [18]. The need for the neutralization step and subsequent disposal of neutralized salt in acid and base catalyzed reactions could be eliminated by replacing a homogeneous acid or base by a heterogeneous catalyst. This trend to switch homogeneous catalysts with heterogeneous catalysts is part of the drive toward green chemistry which in turn minimize waste and eliminate the need for harmful reactants. Comparison of catalysis for biodiesel production is given in Table 1 which reveals that many industrial processes now operate with solid acid catalysts [19]. But fewer processes operate with solid bases, as solid bases are less prevalent than solid acids [20].

The homogeneous catalysts, commonly utilized for commercial processes, have some disadvantages, such as they cannot recycle, large amounts of waste water is being produced, produce low grade glycerol as byproduct. In other hand, the heterogeneous catalysis offers easy production and purification process with reference to economic and environment. Truth is told, a few scientists have announced the potential monetary focal points of the heterogeneous reactant process over the option homogeneous one [21, 22, 23].

Cost of biodiesel production by heterogeneous catalysts is 4-20% less then homogeneous catalysts. Preparation of new long-lasting heterogeneous catalysts with anticipated physical and chemical properties is one of the most important and eye-attracting emphases of the latest studies. This is the main reason for the production of new heterogeneous catalysts which are suitable for pure biodiesel from different type of fatty acids that have been produced and appraised for FAME synthesis processes [24, 25, 26].

However, numerous additional thought-provoking issues endure to be resolved until highly proficient solid catalysts can be industrialized. However, with a specific end goal to build up a superior comprehension of impetus outline for the transesterification procedure, distinctive heterogeneous incentive utilized for biodiesel generation has been considered and examined in this article. It can be concluded that each of these catalyst properties have remarkable effect on the transesterification reaction. The application of catalysts is for various kinds of oils, reaction parameters and there for stability of the catalysts are also incorporated in this discussion. It can be inferred that each of these catalyst properties have significant influences on the transesterification process.