二氧化碳和丙烯在Cu2(OEt)2/SiO2催化下超临界合成甲基丙烯酸

负载型双核金属乙氧基配合物催化剂Cu2(OEt)2／SiO2采用表面改性法制备。运用滴定、IR、DSC和超临界反应技术对催化剂的表面结构、化学吸附性质和反应性能进行了研究。结果表明：负载型双核金属乙氧基配合物Cu2(OEt)2／SiO2中Cu”与载体SiO2表面O^2-以双齿配位形式键合，存在Cu2(OEt)2双核结构；二氧化碳在催化剂表面吸附形式形成桥式和乙氧碳酸酯基物种两种吸附态，丙烯则只有一种分子吸附态；在超临界的反应条件下，二氧化碳和丙烯在Cu2(OEt)2／SiO2催化剂上可以高选择性地合成甲基丙烯酸；反应物分子共吸附于催化剂表面，同一活性基元以及羧酸根与丙烯解离吸附态的形成是反应顺利进行的关键因素。

Synthesis of Methacrylic Acid from CO2 and C3H6on Cu2(Oet)2/SiO2 Catalyst under Supercritical Condition

The Cu 2(OEt) 2/SiO 2 was prepared by surface reaction modification and ion-exchange method. Surface structure, thermal stability, chemisorption and reactivity of the catalyst were characterized by titration, IR, DSC and supercritical reaction. The experimental results indicated that Cu\+ 2+ bonded with the surface O 2- of SiO\-2 support in bidentate fashion and formed binuclear bridged complex Cu\-2(OEt)\-2 on the SiO 2 support; the bridged ethoxy of Cu\-2(OEt)\-2/SiO\-2 was dissociated at 560K and 668K; the CO 2 chemisorbed on the catalysts to form bridged adsorption state and ethoxy carbonate species, the bridged adsorption state of CO 2 could convert into ethoxy carbonate species under higher temperature, and the propylene chemisorbed on the catalyst to form a molecular adsorption state; the effects of catalyst amount, reaction pressure and reaction temperature on the conversion of propylene were investigated under certain reaction conditios. Under supercritical condition (313K, 7.5MPa), the Cu\-2(OEt)\-2/SiO\-2 catalyst had better propylene conversion and 100% methacrylic acid selection in methacrylic acid synthesis from CO 2 and propylene;the reactivity was determined by CO 2 and propylene co-adsorping on the same active center on the surface of Cu 2(OEt) 2/SiO 2 as well as the COOH and propylene in dissociated adsorption states.