Deoxygenation of Triglycerides by Catalytic Cracking with Enhanced Hydrogen Transfer Activity

Abstract

The efficient use of plant oils as alternative fuels was investigated by studying triglyceride deoxygenation in catalytic cracking using a fluid catalytic cracking catalyst with enhanced hydrogen transfer activity. Unsaturated triglyceride deoxygenation was rapid and complete, but small amounts of oxygenated products such as fatty acids, ketones, and aldehydes were produced from saturated triglycerides. Reaction product analysis showed that hydrogen transfer reactions between oxygenates and hydrocarbons produced by cracking fatty acid carbon chains caused hydrodeoxygenation even in the absence of hydrogen. Catalytic cracking of triglycerides with fatty acid carbon chains of various lengths showed that triglyceride deoxygenation is not affected by steric hindrance, and probably occurs on zeolite external surfaces, whereas secondary cracking of hydrocarbons occurs on the internal surfaces. We showed that catalytic cracking can be used for efficient conversion of triglycerides to hydrocarbons in the absence of hydrogen.

Co-processing of Saturated and Unsaturated Triglycerides in Catalytic Cracking Process for Hydrocarbon Fuel Production

“…Thus, the increase in C 12 /C 11 ratios is consistent with the increase in H 2 O/CO 2 ratios observed in Figure 5. Relatedly, we previously reported that the catalytic cracking of dodecanal gave a lower CO 2 yield and a higher C 12 /C 11 ratio than those obtained for trilaurin and lauric acid (Shimada et al, 2017). We, therefore, concluded that the hydrodeoxygenation pathway in the catalytic cracking of trilaurin includes dodecanal formation.…”

“…Coconut oil consists mainly of saturated C 12 and C 14 fatty acids (46.9 mol% and 15.7 mol%, respectively), while sunflower oil is mainly unsaturated C 18 fatty acids (88.5 mol%). We have previously reported detailed fatty acid compositions of the plant oils used (Shimada et al, 2017). We also used two model triglycerides: trilaurin (a saturated triglyceride composed of C 12 fatty acids; Tokyo Chemical Industry Co., Ltd.) and triolein (an unsaturated triglyceride composed of C 18 fatty acids with a single double bond; Wako Pure Chemical Industries, Ltd.).…”

“…In both experiments, the detected oxygenates were mainly lauric acid (a C 12 fatty acid), 12-tricosanone (a C 23 ketone), 2-tridecanone (a C 13 ketone) and dodecanal (a C 12 aldehyde). These compounds were typical reaction products from the catalytic cracking of trilaurin (a C 12 triglyceride) (Shimada et al, 2017). However, the oxygenates derived from triolein were barely observed in the products from the cracking of the trilaurin/triolein mixture, suggesting the rapid deoxygenation of unsaturated triglycerides.…”

“…Deoxygenation and decomposition of unsaturated triglycerides proceed rapidly, but the products contain large amounts of polyaromatics, which are unsuitable for fuel applications (Dupain et al, 2007;Melero et al, 2010). In contrast, the catalytic cracking of saturated triglycerides produces more paraffins and olefins than aromatics, but the deoxygenation proceeds slowly and must be accelerated to achieve an efficient conversion of plant oils to hydrocarbon fuels (Shimada et al, 2017). To understand the difference in deoxygenation rate for saturated and unsaturated triglycerides, we previously focused on the impact of the hydrogentransfer reaction (Shimada et al, 2017), a bimolecular reaction that proceeds in the catalytic cracking process.…”

“…In contrast, the catalytic cracking of saturated triglycerides produces more paraffins and olefins than aromatics, but the deoxygenation proceeds slowly and must be accelerated to achieve an efficient conversion of plant oils to hydrocarbon fuels (Shimada et al, 2017). To understand the difference in deoxygenation rate for saturated and unsaturated triglycerides, we previously focused on the impact of the hydrogentransfer reaction (Shimada et al, 2017), a bimolecular reaction that proceeds in the catalytic cracking process. Here, hydrogen species are released from a hydrogen donor and received by a hydrogen acceptor.…”