| Light alkenes, such as ethylene and propylene, are very important basic organic chemical materials in the great demand for the chemical industry now. Usually, they are mainly produced by the steam cracking of naphtha, where the naphtha is the distillation product obtained from non-renewable fossil resources, such as petroleum or coal tar. It is necessary to develop an alternative route, non-petroleum way, for the production of light alkenes. Directly making light alkenes from syngas is a promising way due to short process route, raw materials from various ways, less investment cost and lower operation fees. Making light alkenes from syngas is realized by FTS reaction, however, the selectivity of light alkenes via FTS reaction is not so ideal, as the main products of FTS reaction are normal paraffins and follows the Anderson-Schultz-Flory (ASF) distribution.Zeolites or zeolite membranes have been widely used as adsorbents, seprarating agents and catalysts to be applied in petroleum and chemical industries due to their uniform and well-defined micropores-system with pores of nearly molecular size. Recently, some compound materials with core (catalyst)-shell (zeolite) structure were applied in fuel cell field.In order to improve the selectivity of light alkenes, supported catalysts (FeK/Silicalite-1) with zeolite carrier and capsulated catalyst with Silicalite-1 shell (Fe/SiO2-Silicalite-1) were prepared. At the same time, a kind of compound material with Silicalite-1 (Sil-1) zeolite covered carbon was synthesized.(1) Pure phase and high relative crystallinity of Silicalite-2 (Sil-2) zeolites with different morphology were prepared in a short crystal time by a condensing precursor method. The morphology of Sil-2 crystals in this method can be controlled by changing concentrating content of SiO2, content of SDA and crystallization temperature. The synthesized zeolites were characterized by XRD, SEM and N2 adsorption.(2) The FeK/Sil-2 catalysts with proposed Sil-2 carriers prepared by an incipient impregnation method were used for the direct synthesis of light olefins based on the FTS reaction, and showed a higher selectivity for C2～3= than that with Sil-2 synthesized by traditional hydrothemal synthsisi method. The convention of CO increased as the increasing relative crystallinity of as-synthesis Sil-2 zeolites by IHSM. This improved method may provide some useful information on the structure, properties of zeolites and the catalysts materials.(3) A novel zeolite capsule catalyst with a Core (Fe/SiO2)-Shell (Sil-1) structure was designed and prepared successfully by the secondary hydrothermal method (seeding the Fe/SiO2 core catalysts with sub-micrometer Sil-1 zeolite seeds and then hydrothermal synthesis). Characterization on this zeolite capsule catalyst indicated that it had a compact and defect-free zeolite shell enwrapping core catalyst. Light alkenes direct synthesis via Fischer-Tropsch synthesis (FTS) reaction was the application of this zeolite capsule catalyst. Benefitting from the confined space effect and shape selectivity function of zeolite shell, this zeolite capsule catalyst showed better abilities than that of naked core catalyst in FTS reaction, not only on the controlled synthesis of light alkenes but also in depressing the formation of unexpected long-chain hydrocarbons.(4) The compound material of Sil-1 covered carbon was prepared in three methods:1. Active carbon was the C resource, growth Sil-1 zeolite on the surface of active carbon; 2. Firstly, SiO2 capasued C, then transfer Sil-1 zeolite; 3. Firstly, synthesis model carbon used Sil-1 zeolite as template then covered with Sil-1 shell. The synthesized materials with indirect method have a regular distribution of zeolite on their surface and the content of Si is 17.66%.
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