The key of dimethyl ether to olefins (DTO) technology is to synthesize catalysts with high selectivity of light olefins and long lifetime. Crystalline silicoaluminophosphates (SAPO) are microporous material with many applications. SAPO-18 (with AEI framework topology) is a solid acid catalyst with microporous structure that is extensively used in the processes of methanol to olefins (MTO), DTO, CO2/CH4 separation and selective catalyst reduction (SCR) of NOx, and it is structurally similar to SAPO-34 (with CHA framework). However, the drawback of these catalysts in MTO or DTO is rapid deactivation.
Many attempts have been made to enhance the catalytic performance and lifetime of SAPO-18, but the effect of post-acid treatment on DTO performance of SAPO-18 has been barely addressed.
Ho Yu Gyong, a researcher at the Institute of Nano Science and Technology, proposed post-HCl treatment as a method for improving DTO performance of SAPO-18 in DTO reactions and compared the catalytic performances such as crystalline structure, morphology, textural properties, acidity and DTO performance.
She investigated the effect of post-treatment with hydrochloric acid (1-5h with 0.01-0.2M HCl) to improve the catalytic performance of hydrothermally synthesized SAPO-18 (S-0). The microporous surface area of S-0.1-3 (S-0 treated with 0.1M HCl for 3h) was 642m2/g, and the pore channel entrance of crystal surface was extended. The single-run lifetime in DTO was prolonged by 1.5-1.7 times that of S-0 while the light olefins selectivity was increased by about 11%.
For more information, please refer to her paper “Improved DTO Performance after HCl Treatment of SAPO-18” in “Proceedings of KUTIC-2025”.