Catalytic Cracking

A variant of thermal cracking is the catalytic cracking, extensively used in the petrochemical industry to produce a significant percentage of the fossil-derived fuel currently used. This possibility has also been pursued for the production of biofuels from a wide variety of feedstocks, especially from low-value triglyceride-based biomass. The reaction takes place in fluid catalytic cracking (FCC) units where triglyceride mol­ecules are transformed into water, CO2, CO, and a mixture of hydrocarbons, some of the aromatic type [68]. The employment of a catalyst permits the utilization of milder con­ditions of temperature and pressure, with a better control of the final products [27, 92].

Hua et al. [50] studied the catalytic cracking transformation of vegetable oils and animal fats in the laboratory. The results show that they can be used as FCC feed singly or co-feeding with vacuum gas oil, which can give high yield (by mass) of liquefied petroleum gas (LPG), C2-C4 olefins, for example, 45% LPG, 47% C2-C4 olefins, and 77.6% total liquid yield produced with palm oil cracking. Co-feeding with vacuum gas oil gives a high yield of LPG (39.1%) and propylene (18.1%).

Different combinations of reactors and catalysts can be used, as for example pil­lared clays, alumina metal-supported catalysts, zeolites, among others. Also, the huge experience gathered in the petrochemical industry can be relevant in the devel­opment and implementation of cracking processes for biodiesel production.

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