Selective preparation of light aromatic hydrocarbons from catalytic fast pyrolysis vapors of coal tar asphaltene over transition metal ion modified zeolites

Abstract

The catalytic cracking of coal tar asphaltene (CTA) pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons (L-ArHs) in a pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) micro-reactor system. The effects of ultra stable Y (USY), Co/USY and Mo/USY on the selectivity and yield of L-ArHs products and the extent of deoxygenation ( E deoxygenation ), lightweight ( E lightweight ) from CTA pyrolysis volatiles were investigated. Results showed that the yields of L-ArHs are mainly controlled by the acid sites and specific surface area of the catalysts, while the deoxygenation effect is determined by theirs pore size. The E lightweight of CTA pyrolysis volatiles over USY is 9.65%, while the E deoxygenation of CTA pyrolysis volatiles over Mo/USY reaches 20.85%. Additionally, the modified zeolites (Mo/USY and Co/USY) exhibit better performance than USY on L-ArHs production, owing to the synergistic effect of metal ions (Mo, Co) and acid sites of USY. Compared with the non-catalytic fast pyrolysis of CTA, the total yield of L-ArHs obtained over USY (4032 mg∙kg −1 ), Co/USY (4363 mg∙kg −1 ) and Mo/USY (4953 mg∙kg −1 ) were increased by 27.03%, 38.19% and 54.78%, respectively. Furthermore, the possible catalytic conversion mechanism of transition metal ion (Co and Mo) modified zeolites was proposed based on the distribution of products and the characterizations of catalysts.