Selective formation of light olefins from dimethyl ether over MCM-68 modified with phosphate species

• Phosphate-modification of MCM-68 enhanced propylene yield up to 50 C-atom % in DTO reaction.
• The external acid sites on dealuminated MCM-68 were selectively deactivated.
• Phosphate-modified MCM-68 achieved propylene/ethylene ratio as high as 42.
• The prepared catalyst efficiently improved coke durability.

To control the acid sites distribution in MCM-68 zeolite catalyst, phosphate-loaded MCM-68 catalyst was prepared by impregnation with aqueous solution of (NH4)2HPO4 onto MCM-68 and subsequent calcination. Phosphate impregnation was effective for increasing the selectivity to propylene and butylenes. The propylene/ethylene ratio in the products was significantly increased by phosphate modification. The considerable enhancement of the yields of propylene and butylenes could be attributed to diminution of stronger acid sites, especially the acid sites distributed on the external surface of MCM-68 catalyst. Furthermore, phosphate-modified MCM-68 showed high resistance to coke formation, indicating this modification technique is useful to obtain long-lived catalysts in DTO reaction.

Figure optionsDownload high-quality image (235 K)Download as PowerPoint slide