Fe@Si_S-34催化剂的制备及其合成气制烯烃性能_陈治平.pdf

研究论文 Article *E-mail:;Z;Tel:029-85583183 Received July 23,2022;published December 19,2022.Project supported by the National Natural Science Foundation of China(Nos.21908174,22178283),the Natural Science Basic Research Plan in Shaanxi Province of China(No.2020JM-517),the Excellent Youth Science Foundation in Xian University of Science and Technology(2021).国家自然科学基金(Nos.21908174,22178283)、陕西省自然科学基础研究计划面上项目(No.2020JM-517)和西安科技大学 2021 年度优秀青年科学基金资助.14 http:/sioc- 2023 Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences Acta Chim.Sinica 2023,81,1419 化 学 学 报 化 学 学 报 ACTA CHIMICA SINICA FeSi/S-34 催化剂的制备及其合成气制烯烃性能 陈治平*,a,b 孟永乐a 芦静a 周文武*,a,b 杨志远a,b 周安宁a,b(a西安科技大学 化学与化工学院 西安 710054)(b西部煤炭绿色安全开发国家重点实验室(筹)西安 710054)摘要摘要 合成气经费托合成反应直接制低碳烯烃是极具开发前景的合成气直接制烯烃技术,其关键是通过产物分布的调控提高低碳烯烃的选择性.本工作将疏水性 Fe 基费托合成催化剂与 SAPO-34 分子筛进行复合,制备了一系列不同SAPO-34 分子筛含量的 FeSi/S-34 复合催化剂.采用 X 射线衍射、扫描电子显微镜、N2吸附-脱附、NH3程序升温脱附和水接触角测量仪考察了 SAPO-34 分子筛含量对催化剂物化性质的影响.结果表明 SAPO-34 分子筛的含量对催化剂的表面积、孔体积、酸性和疏水性具有显著的影响.随着 SAPO-34 分子筛含量的增加,催化剂的比表面积和总孔体积增加,弱酸和中强酸位点增加,疏水性减弱.催化性能评价结果表明,FeSi/S-34 复合催化剂明显降低了 C5+产物选择性,增加了 C2C4烃类的选择性,适量的 SAPO-34 分子筛能够显著提高 C2C4烯烃的选择性.本研究将 FeSi 催化剂的疏水性和 SAPO-34 分子筛对 C5+烃的裂解活性耦合在一起,在抑制水煤气变换(WGS)反应,降低 CO2选择性的同时获得较高的 C2C4烯烃选择性,为费托合成制烯烃催化剂的研制提供了一条新的策略.关键词关键词 合成气;低碳烯烃;费托合成;疏水催化剂;SAPO-34 分子筛 Preparation of FeSi/S-34 CatalystPreparation of FeSi/S-34 Catalysts and Its Catalytic Performance and Its Catalytic Performance for Syngas to Olefins Syngas to Olefins Chen,Zhiping*,a,b Meng,Yonglea Lu,Jinga Zhou,Wenwu*,a,b Yang,Zhiyuana,b Zhou,Anninga,b(a College of Chemistry and Chemcial Engineering,Xian University of Science and Technology,Xian 710054,China)(b The State Key Laboratory of Green and Safe Coal Development in Western China,Xian 710054,China)Abstract The direct synthesis of light olefins from syngas via Fischer-Tropsch synthesis reaction is a promising technology for direct synthesis of olefins from syngas.The key is to improve the selectivity of light olefins through the regulation of product distribution.In this work,the hydrophobic FeSi catalyst was prepared by room temperature solid state method-Stber-silylation method,and then the catalyst was combined with SAPO-34 molecular sieves with different contents to pre-pare FeSi/S-34 composite catalysts.The effects of SAPO-34 molecular sieve content on the physicochemical properties of the catalysts were investigated by X-ray diffraction,scanning electron microscopy,N2 adsorption-desorption,NH3 tempera-ture programmed desorption and water contact angle measurement.The results showed that the content of SAPO-34 molecu-lar sieve has significant influence on the surface area,pore volume,acidity and hydrophobicity of the catalysts.With the in-crease of SAPO-34 molecular sieve content,the specific surface area and total pore volume of the catalyst increased,the weak acid and medium-strong acid sites increased,and the hydrophobicity weakened.The catalytic performance evaluation results showed that the FeSi/S-34 composite catalyst decomposed C5+hydrocarbons into light hydrocarbons,significantly reduced the selectivity of C5+products and increased the selectivity of C2C4 hydrocarbons.Appropriate SAPO-34 molecu-lar sieve could significantly improve the selectivity of C2C4 olefins.When the mass ratio of FeSi catalyst to SAPO-34 is 2,the C2C4 olefin selectivity of FeSi/S-34 catalyst is the highest,the conversion of CO is 80.0%,the selectivity of CO2 in the product is 8.9%,and the selectivity of C2C4 olefins is 31.1%.In this study,the hydrophobicity of FeSi catalyst and the cracking activity of SAPO-34 molecular sieve for C5+hydrocarbon were coupled together to inhibit the water-gas shift(WGS)reaction,reduce the CO2 selectivity and obtain higher C2C4 olefin selectivity,which provided a new strategy for the development of catalysts for Fischer-Tropsch synthesis to olefins.Keywords syngas;light olefins;Fischer-Tropsch synthesis;hydrophobic catalyst;SAPO-34 molecular sieve DOI:10.6023/A22070329 化化 学学 学学 报报 研究论文 Acta Chim.Sinica 2023,81,1419 2023 Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences http:/sioc- 15 1 引言 低碳烯烃(特别是乙烯、丙烯、丁烯等)是最重要和最基本的有机化工原料,传统的生产工艺严重依赖于石油,根据我国“相对富煤、缺油、少气”的资源状况,以“煤”代“油”生产低碳烯烃,是实现我国煤炭清洁高效利用和保证国家能源安全的重要途径之一1-5,开发煤基合成气制取低碳烯烃技术具有重要的战略意义和实际应用价值.煤经合成气可通过间接法或直接法制取低碳烯烃,间接法中合成气经甲醇制低碳烯烃(MTO)技术已实现商业化6-8.与间接法相比,合成气直接制低碳烯烃工艺省去了甲醇(或二甲醚)合成这一中间过程,具有工艺流程短、能耗低、投资和运行费用较低,富产高附加值油品等特点,在工艺流程优化、节能降耗和烯烃选择性等方面带来较大创新,市场前景广阔.合成气直接转化制低碳烯烃方法主要有两种,一是基于费托合成反应直接制烯烃的 FTO(Fischer-Tropsch to Olefins)过程9-10,该方法主要通过改性费托合成催化剂(Fe 系、Co 系等)获得较高的烯烃选择性.另一方法是基于反应耦合策略的双功能催化路线,使用金属氧化物(非费托活性金属)对 CO 进行吸附、活化,并使其转化为C1或C2中间产物,然后通过分子筛将C1或C2中间产物转化为低碳烯烃,即氧化物-分子筛(OX-ZEO)过 程11-13.与 OX-ZEO 过程相比,FTO 过程具有 CO 转化率高、副产液体燃料等优点,是合成气直接转化制低碳烯烃研究的热点.由于 Fe 基费托合成催化剂具有价格低廉、链增长能力弱、催化剂活性高、助剂效果明显等优点,在 FTO 过程中得到研究者的广泛关注9,14-15.费托合成反应直接制烯烃技术的核心是催化剂选择性的调控,即抑制 C1副产物的生成和提高低碳烯烃的选择性.近年来众多研究者发现调控费托合成催化剂的亲/疏水性能调控费托合成产物的分布,特别是对 Fe基费托合成催化剂进行疏水改性能够抑制 WGS(Water-Gas Shift)反应,减少C1副产物的生成,大幅度降低CO2的排放,显著提高碳原子的利用效率.Fellenz 等16对Fe/MCM-41 催化剂经硅烷化改性制备得到疏水