高稳定性CaO-ZrO2固体碱催化剂的表征和催化性能

用共沉淀法经高温焙烧制备了CaO摩尔分数从10%至50%的CaO-ZrO₂系列催化剂, 将其应用于碳酸丙烯酯和甲醇酯交换合成碳酸二甲酯过程, 并通过XRD, FT-IR, BET, ICP, CO₂-TPD, XPS等表征手段研究了催化剂的物性及其催化性能随组成变化的的规律. 结果表明, 当CaO摩尔分数高于30%时, 表面出现游离的CaO, 虽然具有强碱性和高活性, 但是稳定性差; 而当CaO摩尔分数低于30%时, Ca^2＋进入ZrO₂晶格, CaO与ZrO₂形成连续固溶体, 并且随着CaO含量的增加, 晶格氧的电荷密度增加, 催化剂的碱性增强, 使得CaO-ZrO₂催化剂在碳酸丙烯酯和甲醇酯交换合成碳酸二甲酯过程中获得了高活性和高稳定性.

Characterization and Catalytic Properties of Highly Stable CaO-ZrO2 Catalysts

CaO-ZrO2 catalysts with CaO content ranging from 10% to 50% were prepared by coprecipita- tion and their catalytic performances were evaluated in the synthesis of dimethyl carbonate from propylene carbonate and methanol. The characterization by XRD, FT-IR, BET, ICP, XPS and CO2-TPD indicated that when CaO content was higher than 30%, CaO segregated at grain boundaries and the catalysts showed high activity but low stability. Whereas, Ca2 ion substituted for Zr4 ions in the host lattice to form homoge- neous CaO-ZrO2 solid solution when CaO content changed from 10% to 30%, as a result, the base strength were enhanced and the catalysts showed both high activity and stability towards the synthesis of dimethyl carbonate. The formation of homogeneous CaO-ZrO2 solid solution was responsible for the stability of cata- lysts.