Efficient post-HCl treatment for promoting DTO performance of SAPO-18 and Ni-substituted SAPO-18

Silicoaluminophosphate-18 (SAPO-18) may be a potential catalyst with relatively enhanced stability in dimethyl ether to olefins (DTO) process. In this work, the effect of post-treatment with hydrochloric acid (1 ∼ 5 h with 0.01 ∼ 0.2 M HCl) was investigated to improve the catalytic performance of hydrothermally synthesized SAPO-18 (S-0). The physicochemical and catalytic performances of DTO were compared with those of S-0 and Ni-0 (Ni-substituted SAPO-18), and the effect of the post-treatment of Ni-0 was also identified. The microporous surface areas of S-0.1-3 (S-0 treated with 0.1 M HCl for 3 h) and NiS-0.1-3 (NiS-0 treated with 0.1 M HCl for 3 h) were 645 m2·g−1 and 642 m2·g−1, respectively, and the pore channel entrance of crystal surface was extended compared to S-0 (590 m2·g−1). Due to the moderate acidity (Brønsted/Lewis ratios of 0.96 and 0.98, respectively) of S-0.1-3 and NiS-0.1-3, the single-run lifetime in DTO was prolonged by 1.5–1.7 times that of S-0, while the light olefins selectivity was elevated by about 11 %. Therefore, the modification of S-0 and NiS-0 by HCl treatment was evidenced to be a facile method to promote its performance.