Pd Catalysts For Oxidative Carbonylation Synthetic Glycerine Glycerine Carbonate

In recent years, with the development of biodiesel industry large amounts of byproduct glycerol have been produced. The conversion of glycerol byproducts to various valuable chemicals has attracted much attention. Catalytic chemistry is the key to achieve the goal and key technologies to promote the development of green chemistry. Among them, the oxidative carbonylation reaction due to the high utilization of atoms has obtained people’s favor. In the reaction of oxidative carbonylation of glycerol to glycerol carbonate, PdCl2(phen)/KI、PdI2/KI、Pd(oac)/Mn(acac)3/KBr homogeneous catalyst system can effectively catalyze the reaction. However, the homogeneous system suffers from difficulty in the separation and recovery of catalysts from the reaction mixtures. Hence, a heterogeneous catalyst is desired highly.In this thesis, the oxidation carbonylation of glycerol catalyzed by various Pd catalysts has been investigated. First, we found that the commercially available Pd/C catalyst could be an efficient catalyst for the synthesis of glycerol carbonate by the oxidative carbonylation of glycerol with the aid of NaI. Moreover, the influences of various parameters e.g. types of catalysts, solvents, additives, reaction temperature, pressure, time on the conversion of glycerol were investigated. High conversion of glycerol (82.2%), selectivity to glycerol carbonate (>99%), and TOF (900h-1) were obtained under the conditions of5MPa (pCO:pO2=2:1),140℃,2h. The highly active palladium species were generated in situ by dissolution from the carbon support and stabilized by re-deposition onto the support surface after the reaction was finished. Palladium dissolution and re-deposition were crucial and inherent parts of the catalytic cycle, which clearly involved heterogeneous reactions. This Pd/C catalyst could be recycled and efficiently reused for four times with a gradually decrease in activity. At the same time, we characterize the catalyst before and after the reaction by XRD, TEM, XPS, AAS, BET. In addition, reaction mechanism was proposed for oxidative carbonylation of glycerol to glycerol carbonate.In this thesis, we also prepared Pd sol with narrow size distribution and high dispersion and then deposited it onto various metal oxides supports by colloid-deposition. Their catalytic performance in the oxidative carbonylation of was investigated. The findings are as follows: 1. The effects of preparation parameters e.g. temperature, protective agent type, the amount of protective agent on Pd nanoparticle size were studied. The optimal preparation conditions of Pd sol are:ice bath, polyvinyl alcohol (PVA) as a protecting agent, the ratio of Pd to PVA of1:2mg mg-1.2. The Pd sol with-2.5nm in diameters were load on five different metal oxide supporters (CeO2, TiO2, SiO2, ZnO, Nb2O5), and characterized by means of XRD, TEM, BET and AAS technology. We found that in the catalytic oxidative carbonylation of glycerol, the elemental state Pd is the main active species; The greater Pd-Leaching in the reaction, the greater yield of the glycerol carbonate. Pd/TiO2has the highest catalytic activity, with73.1%conversion of glycerol,96.6%selectivity to glycerol carbonate, and1192h-1TOF. However, the activity was significantly decreased after three recycling.