Interface mediated crystallization of plate-like SAPO-41 crystals to promote catalytic hydroisomerization

Abstract

Silicoaluminophosphates SAPO-41 is a superior unidimensional zeotype catalyst used in hydroisomerization. Generation of hierarchically structured SAPO-41 provides an effective way to promote its hydroisomerization selectivity, which is nonetheless difficult to achieve due to the formation of impurities. Herein, we report crystallization of plate-like crystals of pure phase SAPO-41 in a toluene-aqueous biphasic media in the presence of both Pr2NH and oleylamine. The obtained material has a larger adjustable range of silicon content (nSi/(nAl+nSi+nP) = 0.02−0.15), intermediate acidity and reduced diffusion path length along the micropore channel direction. Catalytic tests for n-heptane hydroisomerization on Pt loaded plate-like SAPO-41 crystals showed that the yield of the isomerized products could reach up to 68 %, with respect to 57 % for a control sample. The selectivities for isomers were found to increase with decreasing Si contents and enhanced diffusion properties, suggesting side β-scission reaction was disfavored at reduced acid site density and shortened diffusion path length.