Hybrid catalysts composed of different loadings of Zr-promoted Zn/Al₂O₃ with SAPO-34 zeolite were investigated for the direct synthesis of lower olefins from syngas in a fixed-bed reactor. Zn/Al₂O₃ catalysts and Zr-promoted Zn/Al₂O₃ catalysts with different weight ratios were prepared by a co-precipitation method, respectively. Nano-sized SAPO-34 zeolite was synthesized by a hydrothermal method. The crystallinity, morphology, textural properties and acidic properties of the catalysts were characterized well by XRD, ICP-OES, TEM, H₂-TPR, N₂ adsorption–desorption isotherm analysis, XPS, and NH₃-TPD, respectively. The H₂-TPR results suggested that the presence of Zr on the surface of the support favors the reducibility of zinc oxide with a shift to a lower reduction temperature. The Zr promoter improved the Zn dispersion and enhanced the surface area of Zn/Al₂O₃ catalysts. Various factors that influenced the catalytic activity, including the reaction temperature, the different weight ratios of the methanol synthesis catalyst to SAPO-34 zeolite, the gas flow rate and stability, were investigated in detail. The hybrid catalysts composed of Zr·Zn/Al₂O₃ and SAPO-34 showed excellent catalytic performance in terms of activity, selectivity and stability for the conversion of syngas into lower olefins. When Zr-free Zn/Al₂O₃ was used for the hybrid catalyst instead of Zr·Zn/Al₂O₃, the conversion and stability were low. The results show that a synergistic effect existed between the Zr·Zn/Al₂O₃ component and SAPO-34 zeolite and it was directly related to the resulting catalytic performance. This study will contribute to the development of efficient catalysts for the production of lower olefins from syngas.

中文翻译：

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Zn / Al ₂ O ₃ -SAPO-34杂化催化剂上合成气合成低级烯烃的研究：掺杂Zr的作用及Zn / Al ₂ O ₃比例的影响

研究了由Zr促进的Zn / Al ₂ O ₃与SAPO-34沸石负载量不同的杂化催化剂，用于在固定床反应器中由合成气直接合成低级烯烃。采用共沉淀法分别制备了不同重量比的Zn / Al ₂ O ₃催化剂和Zr-促进的Zn / Al ₂ O ₃催化剂。通过水热法合成了纳米级SAPO-34沸石。通过XRD，ICP-OES，TEM，H ₂ -TPR，N ₂吸附-解吸等温线分析，XPS和NH ₃很好地表征了催化剂的结晶度，形貌，质构性质和酸性。-TPD。H ₂ -TPR结果表明，在载体表面上Zr的存在有利于氧化锌的还原性，同时转变为较低的还原温度。Zr促进剂改善了Zn的分散并增加了Zn / Al ₂ O ₃催化剂的表面积。详细研究了影响催化活性的各种因素，包括反应温度，甲醇合成催化剂与SAPO-34沸石的不同重量比，气体流速和稳定性。Zr·Zn / Al ₂ O ₃组成的杂化催化剂SAPO-34在合成气转化为低级烯烃的活性，选择性和稳定性方面表现出优异的催化性能。当将无Zr的Zn / Al ₂ O ₃代替Zr·Zn / Al ₂ O ₃用作杂化催化剂时，转化率和稳定性低。结果表明，Zr·Zn / Al ₂ O ₃组分与SAPO-34分子筛存在协同作用，与催化性能直接相关。这项研究将有助于开发由合成气生产低级烯烃的有效催化剂。