Improved aromatic yield and toluene selectivity in propane aromatization over Zn–Co/ZSM-5: effect of metal composition and process conditions

Abstract

In this report, a catalytic enhanced-conventional process production background was employed to determine the most cost-effective and environmentally friendly techniques to improve the catalytic production of toluene and other aromatic compounds from propane aromatization. 2 wt% of zinc was co-impregnated with 1-3 wt% of cobalt on HZSM-5. Characterizations and analysis showed that catalysts are crystalline and microporous. Propane conversion was carried out at 540 °C, 1200 ml/g-h gas hourly space velocity and atmospheric pressure over Zn-Co/ZSM-5 bimetallic catalysts. Toluene selectivity in the aromatic products was greatly improved and sustained significantly together with other aromatic products. Catalytic conversion of propane and aromatic yield over Zn-Co/ZSM-5 was improved and stabilized due to metallic collaboration on HZSM-5. Aromatic yield averaged 46, 32, and 36%, respectively, for 1-3 wt% Co in Zn-Co/ ZSM-5 bimetallic catalyst. Average toluene selectivity in the aromatic products for 12 h time on stream from 60, 50 and 51% for 1-3 wt% Co loading. The threshold loading of cobalt with zinc was 2% above which the general aromatic selectivity declined. A decrease in conversion from 73 to 15% was observed for flowrate increase from 6 to 35 ml min −1 and an increase in aromatic selectivity from 80 to 87%. An increase in temperature of 500-560 °C increased catalytic performance, 32-47% for propane conver-sion, and 79-86% aromatic selectivity. KeywordsPropane conversion • Aromatic yield • Toluene selectivity • Zn-Co/ZSM-5 Abbreviations BET Brunauer-Emmett-Teller BTEX Benzene toluene ethylbenzene xylene FTIR Fourier transform infra-red H 2 -TPR Hydrogen-temperature programming reduction SEM Scanning slmctron microscopy TEM Transmission electron microscopy XPS X-ray photoelectron spectroscopy XRD X-ray diffraction XRF X-ray fluorescence * G. G. Oseke