Abstract

A series of Mg/Al/Zr hydrotalcite-like compounds catalysts were prepared using coprecipitation method with $\frac{{\mathrm{Zr}}^{4+}}{{\mathrm{Al}}^{3+}+{\mathrm{Zr}}^{4+}}$ ranging from 0 to 0.62. The catalytic performance of prepared hydrotalcite was evaluated in the synthesis of carbamates from carbon dioxide, amines and alcohols. The effect of Zr incorporation on the structural and textural features was performed using a panel of techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), elemental analysis (ICP-OES), ${\mathrm{N}}_2$ physisorption at 77 K and temperature-programmed desorption of NH₃ and CO₂. It has demonstrated that the catalyst Mg/Al/Zr containing the lowest amount of Zr exhibited a well crystallized hydrotalcite like phase, a highest specific surface area with an average particle size of 20 nm. The results of catalytic performances were in good correlation with the specific surface area and the basic properties of the catalysts favoring the yield of carbamate. Catalyst HT_0.20 showed the best performance in the phosgene-free-halogen-free synthesis of carbamates with a 46% of amine conversion at 473 K and a CO₂ pressure of 90 bars and selectivity toward the carbamate of 63% in presence of DMP as a dehydrating agent.

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摘要

采用共沉淀法制备了一系列 Mg/Al/Zr 类水滑石化合物催化剂$\frac{{\mathrm{锆}}^{\mathrm{4个}+}}{{\mathrm{阿尔}}^{\mathrm{3个}+}+{\mathrm{锆}}^{\mathrm{4个}+}}$范围从 0 到 0.62。在由二氧化碳、胺和醇合成氨基甲酸酯时评价了所制备的水滑石的催化性能。使用包括透射电子显微镜 (TEM)、X 射线光电子能谱 (XPS)、X 射线衍射 (XRD)、元素分析 (ICP-OES) 在内的一组技术来执行 Zr 掺入对结构和纹理特征的影响,${\mathrm{否}}_{\mathrm{2个}}$_{NH 3}和CO ₂的77 K 物理吸附和程序升温解吸。已经证明，含有最低量 Zr 的催化剂 Mg/Al/Zr 表现出结晶良好的类水滑石相，平均粒径为 20 nm 的最高比表面积。催化性能的结果与比表面积和有利于氨基甲酸酯产率的催化剂的基本性质具有良好的相关性。催化剂 HT _0.20在氨基甲酸酯的无光气无卤素合成中表现出最佳性能，在 473 K 和 CO ₂压力为 90 巴时胺转化率为 46%，在 DMP 存在下对氨基甲酸酯的选择性为 63%一种脱水剂。

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