Enhanced catalytic performance of low-Si/Al-ratio beta-zeolite modified by La/Cu on C4 alkylation

Zeolites have emerged as the highly potential solid catalysts in isobutane (C4) alkylation due to their adjustable acidity and structural properties. The introduction of rare earth metal or transition metal can effectively regulate the acidic site distribution and strength of beta zeolite. The structural stability, acid properties and catalytic performance of low Si/Al ratio beta zeolites functionalized with various lanthanum and copper loadings are systematically investigated for the C4 alkylation through experimental characterization and catalytic evaluation. It is revealed that the optimal metal loading can impart superior acidic properties to beta zeolites. Lanthanum modification increases the total amount of Brønsted acid sites (BAS), and enhances the population of moderate and strong BAS compared to copper modification. Catalytic evaluation demonstrated that copper-modified beta zeolites achieve a higher research octane number (RON) up to 93 for alkylate, but exhibit a shorter catalyst lifetime. Lanthanide-modified counterparts exhibit a catalytic lifetime of 320 min and 65 wt% trimethylpentane (TMPs) selectivity with relatively stable RON of 90 during a prolonged stable operation, and meanwhile, the optimal lanthanide-modified HB-1 zeolites (0.35 wt% La@HB-1) demonstrate high level of catalytic lifetime and TMPs selectivity after three cycle experiment. The information obtained from this work will contribute to a better understanding of the metal-modified low-Si/Al-ratio beta zeolites for catalyzing the C4 alkylation.