Catalytic conversion of methanol into light alkenes on mordenite-like zeolites

The paper deals with the effect of the numberand strength of acid sites and with feed composition during methanol conversion into hydrocarbons on mordenite and dealuminated mordenite. The mordenite sample used in this work possesses principally aluminium-hydroxyl groups that absorb at 3650 and 3610 cm−1. They can interact strongly with product molecules. A rapid deactivation by coke was observed. The dealuminated mordenites exhibit principally aluminium-hydroxyl groups that absorb at 3530 cm−1. Their interaction with the product molecules is less pronounced than that of the high frequency aluminium-hydroxyl groups. This and the reduction of the number of strong acid sites lead to a lower deactivation by coke and a higher selectivity to light alkenes. Decreasing the partial pressure of methanol and the addition of water to the feed lead to higher yields of light alkenes, principally of propene, and less coke deposition. Water competes with alkenes and aromatics for the Lewis and Brønsted acid sites. The coke deposition suppresses the conversion of alkenes into alkenes and aromatics so that the selectivity to propene, butene and C5+ alkenes is increased.