| Ethylene hydroformylation is an important industrial process for producing propanal. In this work, a gas-solid heterogeneous catalysis-reaction technology was applied to this reaction system. Three kinds of supported complex catalysts Cu2(μ-X)2/SiO2 (X=OMe,Cl,OAc) were designed and prepared by surface modification combined with ion-exchange method. The physico-chemical structures, thermal stability , chemisorption properties and reaction behaviors were characterized by methods of titration analysis, IR, BET, XRD, TEM, TG/DTA, TPD and microreactor technique. The results obtained from the experiments are as follows:The active component of the supported dinuclear complexes Cu2(μ-X)2/SiO2 were dispersed highly on the surface of silica with particle size around 5 nm. These dinuclear bridged complexes existed on the catalyst surface, copper (II) bonded with the surface O2- on SiO2 carrier in bidentate fashion, and bis-μ-OMe(Cl,OAc) bridged structure Cu2(μ-X)2 was formed between two copper (II) ions. They decomposed to mononuclear complexes CuX/SiO2 at 153190℃, and the CuX/SiO2 continued to decompose to metal oxides at the temperature up to 450℃.These supported dinuclear bridged complexes had the thermal stability in the order of Cu2(μ-OMe)2/SiO2>Cu2(μ-Cl)2/SiO2 >Cu2(μ-OAc)2/SiO2.Three kinds of the catalysts had a better chemisorption property to H2, CO and C2H4. The H2 could be mainly chemisorbed on the active sites of Cu(II) and bridged ligands with the activation order of Cu2(μ-OAc)2/SiO2>Cu2(μ-Cl)2/SiO2 >Cu2(μ-OMe)2/SiO2. The CO and C2H4 could be chemisorbed on copper(II) to form liner CO adsorption state and alkene complex byσ/πfor hydroformylation respectively. The activation ability for CO and C2H4 were in the order of Cu2(μ-OMe)2/SiO2>Cu2(μ-Cl)2/SiO2 >Cu2(μ-OAc)2/SiO2.The reaction products of ethylene hydroformylation on the three kinds of catalysts were mainly propanal, ethane and propanol. The temperature, space velocity, pressure and reactant composition had some influence upon the conversion of ethylene and the selectivity of propanal. Under the conditions of 100℃, 1000h-1, 0.1MPa, n (C2H4) / n (CO) / n (H2)= 1/1/1, the ethylene conversion of 8% and the propanal selectivity of 85% was obtained over Cu2(μ-OMe)2/SiO2.Based on the above experimental results, a probable reaction mechanism of ethylene hydroformylation over supported dinuclear complexes Cu2(μ-X)2/SiO2 (X=OMe,Cl,OAc) was discussed.
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