One-Step Alkylation of Benzene with Syngas over Non-Noble Catalysts Mixed with Modified HZSM-5

para-Xylene is an important chemical for industry. In this work, alkylation of benzene with syngas (ABS) is carried out to prepare toluene and xylene over zinc/chromium (Zn/Cr) oxide and modified HZSM-5. The catalyst with a Zn/Cr ratio of 1.6 and 20% (wt) silicate-1 zeolite (S1) coated HZSM-5 has the best catalytic performance, exhibiting 34.4% benzene conversion and 94.7% total selectivity of toluene and xylene, with 73.2% of xylene as para-xylene. The catalyst is carefiilly characterized; results showed that the activity was enhanced by excessive zinc atoms, which would replace the surface chromium atoms, and this substitution led to more oxygen vacancies. Besides, by coating a layer of S1 on HZSM-5, the production of trimethylbenzene was suppressed and the selectivity of para-xylene among all xylene was increased, due to the coverage of zeolite surface acid sites. These findings are helpful for understanding the one-pot syngas conversion and benzene alkylation processes.