Feasibility of modified bentonite as acidic heterogeneous catalyst in low temperature catalytic cracking process of biofuel production from nonedible vegetable oils

Abstract

Acidic bentonite clay was obtained through surface modification of bentonite clay using hydrochloric acid as acidic precursor to increase the acidity of the bentonite. The modified catalyst was examined via X-ray fluorescence (XRF), XRD analysis, Brunauer Emmett and Teller surface area (BET), FTIR analysis and temperature-programmed desorption (TPD) analysis. XRF analysis showed that the acid modification of bentonite clay results in an increase in the silica content and lower abundance of metal oxides, due to the dissolve of Fe2O3, MnO, CaO, Na2O. Ca2+, Na+ cations from the interlayer and octahedral sheets. FTIR spectroscopy showed that the acid activation decreased the intensity of the absorption bands at 915, 875 and 836 cm−1 which arise from the binding modes of OH groups. NH3-TPD analysis showed a considerable increase in the moderate and strong Bronosted acid cites on the modified bentonite compared to the native clay. The modified bentonite was evaluated as economic and efficient heterogeneous catalyst in catalytic cracking process of two nonedible vegetable oils to obtain the corresponding biofuels at moderate processing temperature of 250–280 °C. It was observed that the catalytic conversion was preceded under mild temperature and obtained efficient biofuels with approved physical and fuel properties according to ASTM specifications. The role of the catalyst ratio was considerable on the yield percent and the properties of the obtained biofuels. The catalytic activity-reaction mechanism was discussed based on NH3-TPD analysis.