Study On Catalytic Hydrogenolysis Of Glycerol To Propanediol

As much attention has given to the production of biodiesel for taking place of crude oil, it is imperative to find a way to treat abundant by-product of glycerol in order to improve the economy of the whole biodiesel production process. The process for using glycerol to produce propanediol is both the optimum process for the low cost production propanediol and a outlet for glycerol. 1,2-propanediol is extensively used for polyester resins, food products and pharmaceuticals. Polyesters produced by copolymerized 1,3-PDO and terephthalic acid have exhibited goodlight stability, elastic recovery, chemical resistance and biodegradability, which are widely used for manufacturing engineering plastics and carpet. Therefore, the manufacture of propanediol has attracted considerable interest.In this paper, the synthesis of propanediol by catalytic hydrogenolysis of glycerol using different kinds of catalysts, such as Pd/C, Ru/C, copper chromite, Pt/C and nano CuO/SiO₂ copper-based catalyst was carried out. The optimum reaction conditions were obtained by orthogonal experiment and single-factor experiments. It has been confirmed that nano copper-based catalysts were of highly catalytic activity.The co-precipitation method for preparing nano copper-based catalysts and hydrogenolysis of glycerol catalyzed by the above-mentioned catalysts were studied. The catalysts were characterized by XRD,TEM,BET,TG/DTG,SEM,ICP to establish the relationship of preparation-structure-performance of catalysts, so as to provide guidance for the preparation of catalysts and reaction mechanism. Nano CuO/SiO₂ copper-based catalyst was prepared by a co-precipitation method and was used for the synthesis of 1,2-PDO by hydrogenolysis of glycerol in the fixed bed microreactor. The influences of reaction temperature,H₂ pressure,hydrogen alcohol ratio and liquid hourly space velocity on hydrogenolysis of glycerol were considered. The results indicated that the conversion of glycerol was 100%, while the selectivity of 1,2-propanediol was 98.7% under the following reaction conditions: reaction temperature 200℃, H₂ pressure 1.0 MPa, n(H₂): n(glycerol)=30:1, and liquid hourly space velocity 0.30 h^-1. The yield of 1,2-PDO could maintain about 95% under the condition of continuous production of 1,2-PDO by hydrogenolysis of glycerol catalyzed by nano CuO/SiO₂ within 700 h, which indicated the catalyst was of high stability and longer life-span. The addition of Ti, Pd, Al etc. made the selectivity of 1,3-PDO reach up to 78.2% because of stronger synergy effcct, better dispersion of active components. Catalytic performance of four catalysts was contrasted, which were used to catalyze the preparation of 1,3-PDO by hydrogenolysis of glycerol. The optimum conditions were obtained as follows: nano CuO-TiO₂-PTA-PdO/SiO₂ as catalyst, reaction temperature 220℃, hydrogen pressure 4.0 MPa, hydrogen alcohol ratio 40:1, the conversion of glycerol was 44.6% with selectivity of 1,3-PDO 38.2%.