Lanthanum incorporation in H-MOR zeolite to improve shape selectivity and stability against coke formation during the alkylation of toluene with isopropanol

Abstract

In aromatic alkylation over acidic zeolites, an optimal catalyst must exhibit shape selectivity for desirable products and resistance to coke formation, both of which can be enhanced by additives like lanthanum (La). This study examines the incorporation of La into H-MOR and its effects on shape selectivity and catalyst stability during the alkylation of toluene with isopropanol. La modifies the zeolite’s pore size and Brønsted acidity, improving reaction selectivity and coke resistance. The results show that La enhances para-selectivity while suppressing ortho-selectivity by inhibiting the formation of bulkier products, either by altering transition states in isomer formation or restricting isomer diffusion within the zeolite channels. Additionally, La-MOR demonstrates greater coke resistance, as La promotes hydrogen transfer from coke precursors to surface carbenium ions and titrates Brønsted acid sites, reducing olefin oligomerization. These findings highlight La’s potential for tuning zeolite properties to enhance catalytic performance.