Catalytic performance of ‘silica-rich core/catalytic shell' type HZSM-5 in the alkylation of 1,2,4-trimethylbenzene with methanol

By selectively passivating acidic sites in the mid-section of the catalyst pores, an acidity-graded channel with the active regions at both ends and the inert region in the middle is constructed, where it can provide the most optimal catalytic micro-environment. In this study, a novel Si-HZSM-5 catalyst was ingeniously synthesized using poly dimethyl diallyl ammonium chloride (PDDA) and tetrapropylammonium hydroxide (TPAOH) as dual templates, and was applied to the alkylation of 1,2,4-Trimethylbenzene with methanol. TEM characterization revealed that the Si-HZSM-5 catalyst possesses a unique structure with ‘silicon-rich core/catalytic shell’. Moreover, by varying the dosage of the dual templates, the catalysts exhibited a well-organized growth pattern, ultimately achieving optimal physicochemical properties (e.g. pore structure and acidity-graded channel) that correlated with the reaction performance. Finally, the Si-HZSM-5-3 catalyst demonstrated the highest activity, achieving a 1,2,4-Trimethylbenzene conversion of 50.7% and a 1,2,4,5-Tetramethylbenzene selectivity of 82.4% under optimized conditions.