【作者】 姜南；

【导师】 张雄福； 王蕾；

【作者基本信息】 大连理工大学 ， 膜科学与技术， 2010， 硕士

【摘要】 低碳烯烃,如乙烯、丙烯等,是重要的基础化工原料,广泛应用于化工行业。通常,低碳烯烃主要来源于非可再生化石燃料资源的石油裂解,开发一种可替代非石油路线的低碳烯烃合成路线显得尤为重要。合成气通过费-托合成反应直接制备低碳烯烃,具有工艺路线短、原料来源广泛、投资少、操作费用低等特点,具有广阔的发展前景,长期以来一直是人们研究攻克的难题。主要问题是低碳烯烃的选择性较差,生成的烃类范围可从甲烷直到石蜡烃,定向调控难度大。为了实现合成气直接制备低碳烯烃,就需要打破Schulz-Flory产物碳数分布方程的限制,提高低碳烯烃的选择性。本文针对合成气直接制备低碳烯烃选择性低的问题,研究了作为负载催化剂的载体Silicalite-2 (Sil-2)分子筛和Silicalite-1 (Sil-1)分子筛膜包覆型铁基核-壳结构催化剂的制备及其催化性能。探讨了Sil-1分子筛包覆炭的新型复合材料的制备。主要内容如下：(1)采用浓缩合成体系的改进水热法制备了不同形貌的Sil-2分子筛,并通过调控浓缩合成液的浓度、晶化温度和模板剂含量等参数,实现控制合成分子筛的形貌,并运用XRD、SEM等表征手段对其晶体类型、形貌和粒径大小进行表征。结果表明,通过调控合成条件,可以获得结晶度高、不同形貌的纯相Sil-2分子筛,而且晶化时间比传统水热法更短。(2)以制备的Sil-2分子筛为载体,采用浸渍法制备了FeK/Sil-2负载型催化剂,研究发现,与以传统水热法制备的Sil-2为载体的负载型催化剂相比,新方法制备的载体催化剂对C2-3=具有更高的选择性,最高达11.1%,比以传统法制备的分子筛为载体的催化剂高5%,CO的转化率随着制备载体结晶度的升高而提高。(3)设计制备了一种Sil-1分子筛膜包覆的Fe/SiO2-Sil-1具有核-壳结构的催化剂。采用等体积浸渍法制备20.0 wt%的Fe-SiO2传统费-托催化剂,再采用晶种二次成膜法制备了不同膜厚的Fe/SiO2-Sil-1核-壳结构催化剂,并运用SEM-对其形貌进行表征。将膜厚为7μm的核-壳结构催化剂用于合成气直接制备低碳烯烃,与传统的Fe/SiO2催化剂相比,C2-3=的选择性提高了10%,同时抑制了长碳链烯烃的形成。(4)分别采用活性炭表面直接合成Sil-1沸石壳、SiO2包覆活性炭后转化成Sil-1分子筛壳法和模板炭法制备不同的分子筛包覆炭的复合材料。其中,模板炭法制备的复合炭材料表面的分子筛分布较均匀、致密且Si含量达到17.66%。更多还原

【Abstract】 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%.更多还原