Quantitative control and identification of copper species in Cu–SAPO-34: a combined UV–vis spectroscopic and H2-TPR analysis

Abstract

A series of Cu–SAPO-34 catalysts with different copper contents were prepared using a modified ion-exchange method, i.e., impregnation–activation. Controlled amounts of well-dispersed active copper species and integrated physical properties were obtained by this method. The Cu–SAPO-34 catalysts retained the CHA structure, high specific surface area, and pore volume of the H–SAPO-34. Based on a combined analysis of UV–vis spectra and H2-TPR, these common laboratory techniques enabled the identification of the different copper species present in the catalysts. Only isolated copper ions balanced by two framework charges were present in the catalysts at copper contents ≤ 0.8 wt%. With increasing the Cu content, isolated Cu2+ ions charge-balanced by one negative charge became dominant. Further higher Cu contents could result in formation of copper oxides after consumption of all ion-exchange sites.