Abstract:

Synthesis of light olefins directly from carbon dioxide is one of the most efficient approaches for utilizing CO₂ resources and mitigating carbon emissions. InZr oxide is an excellent choice for CO₂ activation component of bifunctional catalyst. A series of In-based oxides with different In/Zr were synthesized by co-precipitation method. The CO₂ hydrogenation performance over the bifunctional catalysts composed of InZr binary oxides and SAPO-34 zeolites was investigated. A CO₂ conversion of 34.9% with a C₂—C₄ olefins selectivity of 70.9% (CO free) was achieved as the In/Zr was 2. The structure and reduction properties of the binary oxides were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (H₂-TPR). The results indicate that the bcc-In₂O₃ phase is the main active oxide component for CO₂ hydrogenation, and the introduction of Zr enhances the structural stability of the oxides. In addition, the influence of mixing manner on the performance of the bifunctional catalyst was also investigated. The bifunctional catalyst prepared by mixing in powder state shows a state of oxide adhering to the surface of zeolite particles, which would hinder the diffusion of methanol. However, excess reactants will inhibit the formation of carbon deposits in zeolites. Finally, the effects of reaction temperature, pressure, space velocity and H₂ or CO₂ in reactant on the reaction performance and the stability of the bifunctional catalysts were investigated.

Key words: carbon dioxide, hydrogenation, light olefins, Indium-based oxide, catalyst

摘要：

由二氧化碳加氢直接制取低碳烯烃是实现CO₂资源化利用、缓解碳排放压力的有效途径之一。InZr氧化物是双功能催化剂CO₂活化组分的优异选择。本文采用共沉淀法制备了不同In/Zr比的InZr复合氧化物，并将其与SAPO-34相耦合，测试了该双功能催化剂的CO₂加氢反应性能，当In/Zr比为2时，CO₂转化率达34.9%，C₂~C₄烯烃选择性为70.9%（排除CO选择性）。通过X射线衍射、H₂-程序升温还原等表征方法研究了不同In/Zr比对复合氧化物结构的影响。结果表明氧化物主要以bcc-In₂O₃相存在，Zr的引入增强了氧化物的结构稳定性。此外，本文还考察了混合方式对双功能催化体系性能的影响，粉末混合的催化剂呈现一种氧化物附着在分子筛颗粒表面的状态，这种状态会阻碍甲醇的扩散。而大量反应物的存在不利于分子筛上积炭的形成。最后考察了反应温度、压力、空速、原料H₂或CO₂等工艺条件对耦合催化体系反应性能的影响及其稳定性。

关键词: 二氧化碳, 加氢, 低碳烯烃, 铟基氧化物, 催化剂