The process of the catalytic cracking over highly acidic catalysts was proposed for transformation of triglycerides to obtain chemicals or fuels. The catalytic cracking of fatty acids is a highly unselective process involving cleavage of C-C bond of the fatty acids. In the case of HDO and decarboxylation/decarbonylation process oxygen removal is based on highly selective reactions over a-carbon, whereas in the case of catalytic cracking the reaction can occur independently on the position of carbon-carbon bond in the fatty acid.

Microporous, highly acidic zeolites, such as ZSM-5, have also been used as catalyst in the transformation of fatty acids esters [40] and triglycerides [41]. Transformation of the methyl octanoate gave 99% conversion of the ester at 500°C with a broad distribution of the products from C1 to C7 hydrocarbons from which the highest selectivity was achieved for ethane (34%). Aromatic products such as benzene, toluene, C8, and C9+ aromatics were found in the reaction mixture and their yield exceeds 20% [40]. Transformation of triglycerides over ZSM-5 at temperature of 400°C gave similar product distribution, but with different selec — tivities [41]. After 90% of triolein conversion, propylene was the main product with the selectivity of 44%. Selectivity toward benzene and toluene reached 40 and 20%, respectively.

The example of ZSM-5 suggests that zeolites are not good catalysts for pro­duction of the green diesel because of highly unselective transformation of fatty acids and their derivatives, leading to the formation of undesired aromatic com­pounds. However, it was recently proposed that catalytic cracking of fatty acid esters over MgO/Al2O3 catalysts resulted in minor formation of aromatic com­pounds, maintaining good deoxygenation activity [42].

The effect of MgO loading in Al2O3 was studied in oleic acid deoxygenation. The experiments were carried out at the temperature of 300, 350 and 400°C in presence of MgO-Al2O3 catalysts with magnesium oxide loading of 30, 63, and 70 wt% of the total catalyst weight [42]. With the MG-63 (MgO 63 wt%) and MG-70 (MgO 70 wt%) the oleic acid was converted in 98%. The oxygen content in the reaction mixture was below 1 wt%, for reaction at 400°C. The reaction mixture was composed from hydrocarbons in the range of C7-C17, and minor aromatics compounds. The reaction should be performed above 350°C to avoid saponification of fatty acids.

Recently, the use of Cs-containing zeolites (CsNaX) as a deoxygenation cata­lyst was proposed [43]. The CsNaX catalyst has an advantage of high selectivity toward n to n—2 carbon length hydrocarbons (n—length of fatty acid chain) compared to non-Cs-containing zeolites over which poor selectivities have been achieved. The transformation over CsNaX catalyst of 10% methyl octanoate was performed in methanol which sustains catalyst activity, at 425°C and inert atmospheric pressure. The CsNaX catalyst is superior to MgO, in the activity, which indicates that not only basic sites are needed for the conversion of fatty acids esters, but also synergy of basic and acidic zeolite sites is required.