Improvement of renewable transportation fuel properties by deoxygenation process using thermal and catalytic cracking of triglycerides and their methyl esters

Growth of the world energy consumption, depletion of energy sources and global warming related to fossil fuel consumption have increased the attention toward the production of renewable fuels. Conversion of vegetable oil and fats (natural triglycerides) to biofuel is one of the options to produce renewable fuels for the transportation sector, but the yield and quality of products are among the important factors in the process. This paper presents some of the results obtained from the study of deoxygenation and ketonization processes using thermal/catalytic cracking of sunflower oil and its methyl esters for the production of transportation biofuels. Sunflower oil was converted to methyl ester in the presence of KOH through transesterification reaction and was used as a feed for the cracking process. Fuel properties after thermal cracking of sunflower oil and its methyl esters have been compared to determine the benefits of transesterification process as a pretreatment step for the triglycerides. To reduce the oxygen content of the liquid products and improve properties of the fuel after catalytic cracking using HZSM-5, deoxygenation over gamma-Al2O3 and ketonization over MnO2/gamma-Al2O3 catalysts were examined. Results show that depending on the thermal cracking severity, while the yields of the liquid organic products from thermal cracking of sunflower oil and its methyl esters were almost the same, their acidity vary between 3.78 and 5.41 mg KOH/g for methyl esters and between 66.16 and 123.41 mg KOH/g for triglycerides. The extracted heavier cuts similar to gas oil vary between 5.26% and 2235% for methyl esters and between 18.39% and 51.03% for triglycerides, which proves the benefits of methyl ester cracking to the original oil cracking. Decarboxylation and ketonization of the liquid products with catalysts reduce the acidity and improve other properties of the fuel to the standard level. (C) 2016 Elsevier Ltd. All rights reserved.