Characterization of aluminophosphates: Identification of 18-member ring structure in AlPO4-8

Abstract

The first claim in 1987 of an aluminophosphate (VPI-5) with a pore diameter greater than 7 Å regenerated interest in ultra-large pore molecular sieves for which theoretical models have existed since 1969. Large micropore materials are needed, especially in the oil industry, as catalysts which have the high acidity of zeolites, are thermally stable at high temperatures and pressures, and have significant porosity to allow diffusion of heavier feedstocks currently being seen in refineries.The aluminophosphate VPI-5 is reported to be the first molecular sieve to contain an 18-member ring structure with a pore diameter greater than 12 Å based on X-ray powder diffraction and adsorption data. Researchers at Mobil laboratories have crystallized the silicoaluminophosphate molecular sieve MCM-9 an its X-ray powder diffraction pattern has been shown to match a mixture of VPI-5 and AIPO4-11.