Research Of Cu-Based Composite Oxide For The Catalytic Hydrogenolysis Of Glycerol To Propanediols

Converting glycerol to propanediols by selective catalytic hydrogenolysis has attracted much attention in recent years. Propanediols include 1,2-propanediol (1,2-PDO) and 1,3-propanediol (1,3-PDO). Compared with 1,2-PDO,1,3-PDO has better economic benefit and development prospect. At present, the researches on the hydrogenolysis of glycerol to 1,3-PDO mostly base on the supported noble-metal catalysts. While our previous studies showed that copper-based acid-base bifunctional catalysts could also convert glycerol into 1,3-PDO, and Bransted acid sites was conducive to the generation of 1,3-PDO. Composite oxide catalysts derived from hydrotalcite-like compounds (HTLCs) have acid-base properties, and it could be modulated by varying proportion of the components. HTLCs consist of alternating anionic An"*zH20 layers. Heteropoly acids (HPAs) and/or acid salts have strong Bransted acid sites. Therefore, Heteropoly anionic can be introduced into HTLCs via ion exchange method to increase the Bransted acid sites on the catalyst, which will be beneficial for the high selectivity of 1,3-PDO.Catalysts derived from Cu-Ca-Al hydrotalcites prepared by co-precipitation method were applied for hydrogenolysis of glycerol to propanediols. Effects of the reaction time, reaction temperature and initial hydrogen pressure on the hydrogenolysis of glycerol were systematically investigated. It was observed that the Cu-Ca-Al catalyst with a mole ratio of 1:3:5 showed the best catalytic activity. Under the reaction conditions of 3.5 MPa initial hydrogen pressure at 200℃ for 8 h, the conversion of glycerol was up to 73.2% with 42.6% selectivity to 1,2-PDO and 9.1% selectivity to 1,3-PDO.CuZnAlH-NO3 type of hydrotalcite-like compound was synthesized firstly by co-precipitation method, and CuZnAlH-SiW heteropoly anion column hydrotalcite-like compound was prepared by iron exchange method. Catalysts derived from CuZnAlH-SiW were applied for hydrogenolysis of glycerol to propanediols. Effects of the mass fraction of SiW, reaction time, reaction temperature and initial hydrogen pressure on the hydrogenolysis of glycerol were systematically investigated. It was observed that the introduction of heteropoly anion promoted the generation of 1,3-PDO significantly, and the CuZnAl-30SiW catalyst showed the best catalytic activity. Under the reaction conditions of 3.5 MPa initial hydrogen pressure at 220℃ for 11 h, the conversion of glycerol was up to 72.5% with 29.4% selectivity to 1,2-PDO and 19.9% selectivity to 1,3-PDO.Catalysts derived from CuZnFeH-SiW were applied for hydrogenolysis of glycerol to propanediols. Effects of the mass fraction of SiW, reaction time, reaction temperature and initial hydrogen pressure on the hydrogenolysis of glycerol were systematically investigated. It was observed that the CuZnFe-30SiW catalyst showed the best catalytic activity. Under the reaction conditions of 3.5 MPa initial hydrogen pressure at 220℃ for 11 h, the conversion of glycerol was up to 68.9% with 35.6% selectivity to 1,2-PDO and 22.4% selectivity to 1,3-PDO.