Improved brønsted to lewis (B/L) ratio of co-and mo-impregnated ZSM-5 catalysts for palm oil conversion to hydrocarbon-rich biofuels

Abstract

The purposes of this study are to investigate the effect of metal (Co and Mo) impregnation to ZSM-5 catalysts on the Brønsted to Lewis (B/L) ratio as the active sites of cracking reaction, and the catalysts’ performance testing for palm oil cracking to produce hydrocarbon-rich biofuels. Both metals were impregnated on the ZSM-5 catalyst using a wet-impregnation method. The catalysts were characterized using X-ray diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET), and Pyridine-probed Fourier-Transform Infrared (Py-FTIR) spectroscopy methods. The catalysts were tested on the cracking process of palm oil to biofuels in a continuous fixed-bed catalytic reactor. In order to determine the composition of the organic liquid product (OLP, biofuels), the product was analyzed using a gas chromatography-mass spectrometry (GC-MS) method. The results showed that the co-impregnation of Co and Mo to ZSM-5 highly increased the Brønsted to Lewis acid site (B/L) ratio, although the total number of acid sites decreased. However, the impregnation of Co and Mo on the ZSM-5 decreased the surface area of catalysts due to pore blocking by metals, while the B/L ratio of the catalysts increased. It was obtained that by utilizing Co-and Mo-impregnated ZSM-5 catalysts, the hydrocarbons product selectivity increased from 84.32% to 95.26%; however, the yield of biofuels decreased from 67.57% to 41.35%. The increase in hydrocarbons product selectivity was caused by the improvement of the Brønsted to Lewis (B/L) acid sites ratio.