Study on the performance of alkali acid modified ZSM-5 catalysts for thiophene alkylation reaction

HZSM-5 zeolites with SiO₂/Al₂O₃ molar ratio of 50 as the raw material were treated by a certain concentration of NaOH and then impregnated with citric acid solution to prepare microporous and mesoporous hierarchical HZSM-5 catalyst. The catalytic performance of the prepared catalysts for thiophene alkylation reaction was investigated using simulated oil. The results show that the residual impurities in the pores after alkali treatment can be eliminated by acid washing with citric acid solution. When the concentration of the citric acid solution is 0.5 mol/L, the HZ(AC-0.5) catalyst has the appropriate pore size and acidity, so the conversion of thiophene alkylation is the highest, which is up to 95.6%. The performance of thiophene alkylation reaction was also investigated by respectively using dibenzothiophene thiophene derivatives as model compounds, olefin isoprene as model compounds, aromatic benzene as model compound on the HZ (AC-0.5) catalyst. And then we analyzed the influence of different components in the simulated oil on the conversion and selectivity of thiophene alkylation reaction. It has been demonstrated that the optimum reaction temperature of thiophene alkylation reaction is 120℃. At the optimum temperature, the conversion of benothiophene alkylation is higher than that of thiophene alkylation. The conversion of thiophene will be increased when the olefin isoprene is used as model compound. The conversion of thiophene will be decreased when benzene is used as aromatic model compound.