Catalytic Hydrogenation Of Ethyl Lactate To Produce1,2-propanediol

The1,2-propanediol is an important raw material for the production of unsaturated polyester and epoxide resin. Because of its low toxicity and good hygroscopicity,1,2-propanediol has been also widely applied in food, medicine, cosmetic and tobacco industries. With the possible depletion of the petroleum resource, it is of great significance to explore an environmental friendly synthetic route for preparation of1,2-propanediol using a renewable substance such as ethyl lactate instead of petroleum products.In this work, the catalytic hydrogenation of ethyl lactate to produce1,2propanediol has been systematically studied. The research work consists of three parts.First, the catalysts with different supports and additives for the hydrogenation have been studied. The role of active metals, such as Cu, Co, Ni, Mo, and the influence of the supports,such as y-Al2O3, SiO2, MgO, TiO2, ZrO2, to the hydrogenation of ethyl lactate have been investigated. The results show that the catalysts with base oxide supports are generally better than those with acidic oxide supports, possibly because the base oxides have a strong interaction with the active metal and can prevent active metal from sintering during preparation. The Cu/γ-Al2O3gives a best catalytic performance over the other catalysts studied, as far as the selectivity of1,2-propanediol and the covnversion rate of the ethyl lactate are concerned. The role of different additives (Cr, Fe, Zn, Sn) were studied. The addition of Cr to Cu/y-Al2O3leads to an obvious improvement of catalytic performance. The amount of Cr additives was optimized experimentally. The Cu-Cr/y-Al2O3gives he best catalytic activity with a Cu/Cr ratio of2:1and an ethyl lactate conversion rate of79.8%and a selectivity of80.1%for1,2-propanediol were achieved by using this catalyst with Cu loading of10wt%.Second, the influence of the reaction temperature, hydrogen pressure, reaction time, internal and external diffusion on the hydrogenation of ethyl lactate has been studied. It is shown that when the stirring rate is over800r/min, the influence of the external diffusion on the reaction can be ignored. The hydrogenation reaction conditions were opitimized. An ethyl lactate conversion rate of84.7%and a selectivity of85.9%for1,2-propanediol can be achieved by using Cu-Cr/y-Al2O3catalyst at a reaction temperature of200℃, a hydrogen pressure of4MPa and a stirring rate of900r·min-1after6hours of reaction.Third, the reaction mechanism of the hydrogenation of ethyl lactate has been studied by using GC-MS analysis and some contrast experiments. The side reactions of the hydrogenation of ethyl lactate on copper base catalysts were analyzed.