CATALYTIC CONVERSION OF METHANOL TO LIGHT ALKENES ON SAPO MOLECULAR-SIEVES

The effect of pore structure, type of acidity, temperature, silicon/aluminium ratio and amount of water in the feed has been investigated on methanol conversion into hydrocarbons on SAPO-34 and SAPO-11. In the case of SAPO-34, water seems to compete with oxygenated and hydrocarbon molecules for the strong acid sites. Increasing the water content of the feed results in a higher alkene yield and lower coke production rate. The same effect may be obtained by raising the reaction temperature and lowering the silicon/aluminium ratio. A pore size smaller than 0.45 nm and Bronsted acid sites caused by aluminium-hydroxyl groups appear to play an important role in the activity and selectivity for the light alkenes.