Transition Metals-Modified SAPO-34for Methanol Conversion To Light Olefins

Ethylene and propylene as two important organic chemical raw materials, have a pivotal position in the modern chemical industry. The process from coal to methanol, then methanol to light olefins (MTO) makes the non-oil line to produce light olefins vision can be achieved, has a very important practical significance. The research and development of MTO catalyst is the core technology of the MTO.In this thesis, the Me-A catalysts prepared by modifying SAPO-34with transition metals(Zn, Fe, Ni, Co) were investigated by equal volume method, while the Me-B catalysts prepared by modifying SAPO-34with transition metals(Zn, Fe, Ni, Co were investigated by hydrothermal method. The performance of Me-A and Me-B was evaluated in a continuous flow fixed-bed reactor. Catalysts were characterized by XRD, BET, SEM, XPS, NH3-TPD and FT-IR to study physical and chemical properties. The main conclusions were as fllows:(1)1%Zn-A catalyst exhibited the higher selectivity of light olefins compared with other1%Me-A. In order to improve the yield of total olefins,2%was the most appropriate content of Zn. The ethylene yield of2%Zn-A was increased by1.9%than SAPO-34. And the total yield of olefins of2%Zn-A was increased by2.8%than SAPO-34.(2)2%Me-B catalysts exhibited longer lifetime compared with SAPO-34.2%Zn-B catalyst exhibited the higher selectivity of light olefins compared with other2%Me-B. In order to improve the yield of total olefins,6%was the most appropriate content of Zn. The ethylene yield of6%Zn-B was increased by4.0%than SAPO-34, while the total yield of olefins of6%Zn-B was increased by5.0%than SAPO-34.(3) In order to improve the yield of total light olefins and reduce the main byproduct methane,6%Zn-B was filtered out as the optimal catalyst for the MTO process. The optimal condition was determined as follows:the reaction temperature was450℃, the methanol WHSV was4h-1, the ratio of water and methanol (mol ratio) was5:1.