Acid-Treated SAPO-18 Catalyst with High Light Olefins Selectivity and Stability

Abstract The light olefins selectivity and stability of SAPO-18 catalyst was greatly improved by the post acid treatment. The effect of post treatment with different inorganic acids (H3PO4, H2SO4, HCl and HNO3) on the physicochemical properties of SAPO-18 and on the performance of dimethyl ether to olefins (DTO, WHSV: 3.546 h–1, 400°C, atmospheric pressure) conversion was investigated. The order of the effect of acid treatment on the catalytic performance of SAPO-18 was HNO3 > HCl > H2SO4, and there was no acid treatment effect of H3PO4. In particular, SAPO-18 (SN) post-treated with HNO3 was newly created mesopores (V meso: 91 mm3 g–1) and micropores (V micro: 305 mm3 g–1), and also the amount of acid sites (Lewis: 267 µmol g–1, Brønsted: 253 µmol g–1) was optimized, resulting in excellent physicochemical properties compared to the untreated SAPO-18 (S). Consequently, in the DTO performance test, the light olefins selectivity of SN (95.7%, ethylene: 31.1%, propylene: 46.2%, butene: 18.4%) and the single-run lifetime (6.5 h) were increased 11.2% and 2.1 times compared to S (light olefins selectivity: 84.5%, single-run lifetime: 3 h), respectively.