Preparation Of Ru Catalysts Supported On Graphene And Their Applications In The Hydrogenation Of Ethyl Lactate

1,2-propanediol(1,2-PDO) is an important industrial chemicals, and it is also widely used in food, pharmaceutical, cosmetics and other fields. Hydrogenation of lactic acid and lactates to 1,2-PDO will provides an eco-friendly alternative to the petroleum-based process for 1,2-PDO production. Because hydrogenations of carboxylic acids and esters to the corresponding alcohols are often carried out under vigorous reaction conditions due to weak polarisability and intrinsic steric hindrance of the C=O bond esters. Therefore, development of active catalysts for the hydrogenation of esters to the corresponding alcohols under mild conditions is of great importance. The heterogeneous catalysts have received much attention due to their excellent activities, which provides a possibility for hydrogenation of lactic acid and lactates under mild reaction conditions.Graphene is a new carbon nano material, which has the large specific surface area, good resistance to acid/alkali and superior thermal conductivity. The recent emergence of graphene nano sheets has opened a new avenue for utilizing the new carbon material as a support due to their high specific surface area and high chemical stability compared with the traditional activated carbon and carbon nano tubes. Ru-based catalysts showed good reaction performance in hydrogenation of carboxylic acids and esters. Two Ru-based amorphous catalysts were prepared by chemical reduction have been investigated systematically for hydrogenation of ethyl lactate.(1) The graphene oxide prepared by Hummers method, which is the classic chemical reduction method. The Ru/RGO catalyst prepared by reductant impregnation method. XRD, SEM, FTIR and XPS results of GO and Ru/RGO demonstrated that highly dispersed amorphous Ru are formed on the graphene sheets and the GO with highly oxidized. The optimum condition for hydrogenation of lactate esters are investigated. The convention of lactate esters reaches 97.6 % and the selectivity to 1,2-PDO is 98.8 % under conditions of 150 ?,5 MPa for 12 h, lactate esters /Ru molar ratio of 100:1 and 5 wt% Ru. The catalyst was recycled for six times without the marked loss in both the activities and selectivities of 1,2-PDO(selectivity to 1,2-PDO of 71.9 % was obtained at ethyl lactate conversion of 95.2 %).(2) Nitrogen-doped graphene was first used as the catalytic support which prepared by solid-state yrolysis of phthalocyanine. The UV, XRD, SEM, TEM, and AFM results of Nitrogen-doped graphene demonstrated that the in situ synthesis of nitrogen-doped graphene from phthalocyanine is a simple and efficient method.(3) Ru/NG catalysts was prepared by impregnation method using nitrogen-doped graphene as support. The optimum conditions for hydrogenation of lactate esters are investigated. The convention of lactate esters reaches 99.4 % and the selectivity to 1,2-PDO is 98.3 % under conditions of 150 ?,5 MPa for 12 h, lactate esters /Ru molar ratio of 100:1 and 5 wt% Ru. The catalyst was recycled for six times without the marked loss in both the activities and selectivity of 1,2-PDO(selectivity to 1,2-PDO of 73.8 % was obtained at ethyl lactate conversion of 97.7 %). The catalytic performance of Ru/NG is a little higher than Ru/RGO for hydrogenation of lactate esters, which provides a new green process route for the preparation of 1,2-PDO. NG will become a new type of catalyst carrier.