Catalytic conversion of dimethyl ether into propylene over MCM-68 zeolite

• MCM-68 (MSE-type) catalysts with different Si/Al ratios were prepared.
• The MCM-68 catalysts were applied to the DTO reaction.
• Catalytic performance was highly dependent on aluminum content of the catalyst.
• The DTO reaction over MSE-type zeolite gives propylene and butylenes in high yields.

Control of the acid site distribution on MCM-68 zeolite catalysts can be achieved by the acid treatment with nitric acid. Less coke is deposited during DTO reactions over dealuminated MCM-68 compared to the parent MCM-68 probably due to the selective removal of acid sites on the external surface of the parent MCM-68. The higher yields of propylene and butylenes are obtained with lower selectivity for ethylene and lower paraffins over dealuminated MCM-68, whereas ethylene and lower paraffins are predominant over parent MCM-68. The acid treatment may preferentially remove the strong acid sites, and thus the retained acid sites with moderate strength mainly convert dimethyl ether into propylene and butylenes with high propylene/ethylene (P/E) molar ratio. Besides the issue of high P/E ratio, the ratio is also widely controllable by changing the reaction temperature.

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