Synthesis And Properties Of Efficient Nano Copper-based And Nickel-based Catalyst In The Hydrogenation Of Diol Reaction

Ethylene glycol (EG), an important chemical widely used in antifreeze and polyester manufacture, is universally produced from petroleum-derived ethylene via its epoxidation in the present industrial approach. However, this process is greatly restricted by the dwindling petroleum resource. In this respect, the indirect synthesis of EG from syngas via the coupling of CO with nitrite esters to obtain oxalates and then hydrogenation of oxalates to EG has huge potential both in the economic and environmental persistent development.It is well known that mesoporous materials which possess high surface area, large pore volume, regular structure, uniform pore size distribution, and relative high thermal stability have drawn much attention in the field of separation, adsorption, and drug delivery. Immobilization of nanoscopic materials in such high-surface area supports with improved catalytic activity and product selectivity is a task of great economic and environmental importance in the chemical industries.Propylene glycol (PG), used as high value-added speciality chemical intermediates, are widely used for manufacturing polyester fibers, unsaturated polyester resins, antifreeze, pharmaceuticals and other important products. At present, PG is mainly produced from the hydration of corresponding epoxy alkanes, which are commonly derived from a petrochemical approach. However, as crude oil resource shrinks, synthesis of the two diols from biomass glycerol attracts more and more interest. In this work catalytic hydrogenation of dimethyl oxalate to glycerol and catalytic hydrogenalysis of glycerol to diols on Cu catalyst and Ni catalyst has been studied in details. Through characterizations, the effect of bulk structure and surface component of catalysts on the catalytic performance were investigated.Ultra-high (50%) copper contented mesoporous Cu/SBA-15 catalysts were successfully prepared through the simple ammonia-driving deposition-precipitation method. The catalyst shows high copper dispersion and perfect activity in the selective hydrogenation of DMO to EG, much better than that of the catalyst prepared by the traditional impregnation method. The catalyst with a copper content of 50 wt% also exhibited the best catalytic performance at 0.6 h-1,while the conversion of DMO was kept at 100% and the selectivity to EG was above 99%. Such promotion can be ascribed to the much smaller particle size, much higher dispersion of copper species, and more resistance to sintering. With the rapid development of the bio-diesel industry by transesterification of seed oils with methanol, glycerol of renewable origin, as a by-product of bio-diesel production, seems to be an attractive option as a new feedstock. Catalysts containing an active copper compound such as Cu-chromite, Cu-ZnO, Cu-SiO2 or Cu-Al2O3 are active in glycerol hydrogenation. Cu/Al2O3 and Cu/ZnO/Al2O3 catalysts with high copper content and high copper dispersion were successfully synthesized via the simple co-precipitation method that can efficiently catalyze the hydrogenolysis of glycerol to 1,2-propanediol in an autoclave. Cu/Al2O3 (molar ratio:1/1)proved as effective for the production of 1,2-propanediol because of the high selectivity (about 90.1%),but the conversion of glycerol is relative low (about 71.3%). As addition of ZnO, Cu/ZnO/Al2O3 (molar ratio:4/2/4) catalyst shows higher conversion of glycerol (about 92.5%) and keeps high selectivity (about 99.0%). The physical and chemical properties of these catalysts have been studied through various characterization methods such as BET, XRD, TEM and TPR.Raney-Ni catalysts (skeletal catalysts) with a ponge-like structure are one kind of well-known catalyst used in several hydrogenation processes. The prepared Raney-Ni catalysts mainly contains of metal Ni, about 4.64 nm. A new and efficient catalytic route for the production of PG and EG by catalytic combination of glycerol aqueous reforming and hydrogenation of glycerol has been developed using the Raney Ni catalyst. The reaction conditions are much milder than those previously reported, since no hydrogen was needed and the reaction can be conducted under ambient pressure. At 453 K,0.1 MPa of N2 conditions the reaction can get 58.5% diols yield and the 100% conversion of glycerol solution(10wt%).