The catalytic and acidic properties of an i‐Pr2NH‐templated SAPO‐11 and dealuminated derivatives

Abstract

Crystalline silicoaluminophosphate (SAPO‐11) samples were synthesized with i‐Pr2NH as a novel template, then dealuminated in H4EDTA solution. These samples were characterized by catalytic skeletal isomerization of linear butylenes, IR analysis of adsorbed pyridine and 31P, 29Si MAS‐NMR. Strong acid sites were concerned with Si domains, that were formed by either increasing the Si content of SAPO‐11 via a synthesis process or dealuminating treatment of as‐synthesized SAPO‐11. Acid sites of medium strength were located around isolated Si together with adjacent Al and the second nearest element P. Deep dealumination led to amorphous AlPO4, and reduced crystallinity degree. The maximum yield of isobutylene in catalytic skeletal isomerization of linear butylenes were achieved around 763 K. It was confirmed that these reactions were mainly performed on Bronsted acid sites of medium strength.