Study and modification of organic species formed in HSAPO-34 cages during methanol-to-olefin catalysis by ex situ analysis

Silicoaluminophasphate HSAP-34 (CHA topology) is a promising catalyst for the methanol-to-olefin (MTO) reaction. The essential features of CHA topology are cages of ca. 10 by 6.7 A interconnected by 3.8 A diameter windows. Methylbenzenes formed during the MTO reaction are trapped inside the HSAPO-34 cages and act as organic reaction centers to help making and breaking C-C bonds. The organic reaction centers are modified by selective synthesis of naphthalene and methylphenols, respectively. Methylnaphthalenes are reaction centers with higher ethylene selectivity but one-third the activity of the methylbenzenes reaction centers at comparable conversion. Methylphenols show almost no activity towards methanol conversion. On new ex situ analysis method, cryogenic grinding, has been developed to destroy the HSAPO-34 framework. Total ion chromatograms show identical results for CCl4 extracts from acid digestion and cryogenic grinding.