Chloride-free Cu-modified SAPO-37 catalyst for the oxidative carbonylation of methanol in the gas phase

Abstract

The substitution of harmful phosgene or chloride-containing catalysts in the synthesis of dimethyl carbonate (DMC) and its use as “green solvent” or polycarbonate building block direct its manufacture towards environmental benign syntheses. Thus, copper was introduced into silicoaluminophosphate structure SAPO-37 (belonging to the same FAU structure family like aluminosilicate zeolites Y and X) by solid state ion exchange (SSIE) using Cu(II) acetyl acetonate. This strategy circumvented structural breakdown being observed when using aqueous copper solutions for impregnation or ion exchange. The SSIE efficiently ran when the organic template is widely extracted from the synthesis form of SAPO-37, e.g. through treatment with methanolic HCl. The parent SAPO-37, template-free SAPO-37 and Cu-SAPO-37 materials were characterized by XRD, TG, temperature programmed reduction (TPR), temperature programmed desorption of ammonia (TPDA) and FTIR spectroscopy of adsorbed pyridine and CO. The Cu-SAPO-37 catalyst pre-treated in inert gas exhibits a high selectivity for DMC and dimethoxymethane (DMM) in the oxidative carbonylation of methanol (OCM). The catalytic behavior of Cu-SAPO-37 is shown to be comparable with those of a Cu-containing Y zeolite catalyst that is so far regarded as one of the best chloride-free catalyst for the OCM reaction in the gas phase.