Effect of CO2 co-feeding on the conversion of syngas derived from waste to liquid fuel over a bi-functional Co/H-ZSM-5 catalyst

Abstract

A bi-functional Co-HZSM-5 catalyst was synthesised by the Incipient Wetness Impregnation (IWI) of cobalt onto H-ZSM-5 and effect of CO2-co-feeding on the performance of the catalyst during Fischer Tropsch (F-T) was investigated. Physico-chemical property of the catalyst was checked with N2 physisorption (for BET surface area), Transmission Electron Microscopy and Scanning Electron Microscopy equipped with EDS. Effect of CO2 co-feeding was investigated at Gas Hourly Space Velocity (GHSV):1200mlh−1g−1; pressure: 15bar, temperature: 250°C; and H2/CO ratio: 2.5; with a syngas mixture containing 5% CO2. Pre-calibrated GCs were used to analyse the reaction products. The BET surface area, the pore volume and the pore size of the catalyst were 292m2/g, 0.18cm3/g and 2.83nm, respectively. TEM images showed that cobalt particles were well dispersed within the support. In the presence of CO2 co-feeding, CO conversion was 73% and CO conversion was 53% without CO2 co-feeding. In addition, the co-fed CO2 was converted to hydrocarbons and a CO2 conversion of 63% was obtained. The selectivity of the catalyst to methane was 53%, 34% to C2, <4% to C4-C5 and <10% to C6+ in the presence of CO2 co-feeding. Co-feeding CO2 also affected the selectivity of the catalyst to olefin as well. Selectivity of the catalyst to C3 decreased from 43% to 35% while C4 increased from 25% to 32% during CO2 co-feeding. However, selectivity of the catalyst to C6+ olefin hydrocarbon increased from 9% to 15% during CO2 co-feeding.