The Role of Brønsted Acidity In The Dimethyl Ether Aromatization Over ZSM-5 Zeolites

A series of commercial nanosized zeolites and zeolites prepared by in situ seed-induced synthesis with a ZSM-5 structure and a close silica modulus were studied to explore the influence of physicochemical characteristics on the dimethyl ether aromatization and catalyst stability. It was shown that a larger strong Brønsted acidity enhanced the total aromatics formation with an increased light arenes content (especially at elevated WHSV). At low WHSV, excess Brønsted acidity leads to the declined aromatics yield due to its high cracking ability. On the contrary, a higher Lewis acidity and extensive mesoporosity promoted the heavier aromatics production accelerating the coke formation and shortening the catalyst lifetime. An improved aromatization performance and a prolonged durability of the zeolite catalyst were controlled by a balanced Brønsted/Lewis acid site ratio and the ratio of WHSV to acid site concentration.