超临界条件下负载型配合物催化剂Cu_2(μ-OEt)_2/SiO_2合成碳酸二甲酯的反应性能

DMC Synthesis from CO_2 and CH_3OH on Cu_2(μ-OEt)_2/SiO_2 Catalyst under Supercritical Conditions

采用表面改性和离子交换相结合的方法制备了负载型配合物Cu2(μ-OEt)2/SiO2催化剂,用化学分析、IR、TPD和超临界反应技术考察了催化剂的表面构造、CO2和甲醇在催化剂上的化学吸附及超临界条件下的反应性能,结果表明:双核配合物Cu2(μ-OEt)2中金属离子Cu2+与载体SiO2表面O2-以双齿配位键合,配体以桥基形式连接双金属离子形成双核物种Cu2(μ-OEt)2;CO2在催化剂表面存在桥式和乙氧碳酸酯基两种吸附态,其中乙氧碳酸酯基吸附态是生成DMC的关键物种;CH3OH在催化剂上只有一种分子吸附态.催化剂用量、反应压力、反应温度和反应时间对甲醇的转化率都有不同程度的影响,在超临界条件下,DMC的选择性为100%,甲醇的转化率超过4%.

SiO_2 supported binuclear complex, Cu_2(μ-OEt)_2/SiO_2 was prepared by surface reaction modification and ion-exchange method. Surface structure of the catalyst, chemisorption and reaction properties of CO_2 and CH_3OH under supercritical conditions on the catalyst were studied by chemical analysis, IR and supercritical techniques. The experimental results showed that, in the Cu_2(μ-OEt)_2/SiO_2, copper (II) bonds with the surface O_2^- of SiO_2 support in bidentate fashion and bis-μ-OEt bridged structure Cu_2(μ-OEt)_2 is formed between two copper (II), that CO_2 can chemisorb on the catalyst as bridged adsorption state and ethoxy carbonate species, the later is the key species for DMC synthesis, and that the molecular adsorption state of CH_3OH forms on the catalyst. The catalyst amount, pressure, temperature and reaction time have influence to certain extent on the conversion of CH_3OH. Under supercritical conditions, the conversion of CH_3OH is above 4% with the DMC selectivity of 100%.