| 摘要 |
PURPOSE:To improve the selectivity in the preparation of a lower olefin from methanol, etc., by using a composite zeolite prepared by crystallizing zeolites having different chemical compositions or skeleton structure in layers, and making the outermost layer to an Al-containing crystalline layer. CONSTITUTION:In the preparation of a lower olefin by the reaction of methanol and/or dimethyl ether at 250-450 deg.C and 0.5-10atm in the presence of a zeolite catalyst, a particular composite zeolite is used as the catalyst. The composite zeolite is composed of zeolite crystal forming nucleus, and at least one zeolite crystal layer formed around the nucleus by the hydrothermal synthesis. At least two of the above crystal layers have different chemical compositions and/or skeleton structures from each other, and the outermost layer is a zeolite crystal layer containing Al (the ratio of SiO2/Al2O3 is <300). The skeleton structure of the outermost layer is preferably ZSM-5-type, ZSM-11-type or their mixed crystal, and its thickness is usually about 0.1-50mum. |
