One-Step Alkylation of Benzene with Syngas over Non-NobleCatalysts 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 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 carefully 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 to understanding the one-pot syngas conversion and benzene alkylation processes.