Cooperative effects of secondary mesoporosity and acid site location in Pt/SAPO-11 on n-dodecane hydroisomerization selectivity

• n-Dodecane hydroisomerization was studied over mesoporous SAPO-11 catalysts.
• Organosilane templating produced mesoporous SAPO-11 with mainly external acid sites.
• Carbon templating produced mesoporous SAPO-11 with mainly internal acid sites.
• Mesoporosity is either beneficial or detrimental to hydroisomerization depending on the acid site locations.
• Enhancing diffusion and removing external acidity are desirable for hydroisomerization.

Two different methods, organosilane templating and carbon templating, were used to generate secondary mesoporosity within SAPO-11. The former method produced mesoporous SAPO-11 samples with a large amount of external acidity, while the latter produced mesoporous samples containing predominantly internal acid sites. It was shown that, depending on the location of Brønsted acid sites, Pt supported on mesoporous SAPO-11 samples can exhibit widely ranging maximum isomerization yields from 13% to 84%, while solely microporous SAPO-11 showed 44% isomerization yield. The results indicate that the presence of secondary mesoporosity can be either remarkably beneficial or detrimental to hydroisomerization selectivity depending on the spatial location of the acid sites. The present results clearly showed that hydroisomerization selectivity of the catalysts can be significantly enhanced by facilitating the hydrocarbon diffusion via the formation of secondary mesopores while suppressing the formation of external acid sites that can non-selectively catalyze consecutive cracking reactions.

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