Construction And Selective Regulation Of Ru-based Catalytic Systems For Efficient Hydrogenolysis Of Bio-based Polyol

Dihydric alcohol is very important polymer monomer for polyesters. Ethylene glycol and propylene glycol can react with acid to produce excellent polyester material, thus the demand and production for dihydric alcohol are huge. The diol alcohol demand in China has been more than 7 million tons per year, and the external dependence is up to 86%, it has been harder to depend on the petroleum-based production line. With the growth of the national economy, the demand for diol is increasing, it is of important practical significance to develop a new route for bio-based diol alcohol production by using the biomass-based sugar alcohol as raw materials.However, in the catalytic hydrogenation process of bio-based carbohydrate, the reaction conditions of high temperature and high pressure easily cause the selectivity decline for the target products. Considering the problems of high reaction temperature and low product selectivity in hydrogenation process of carbohydrate for diol alcohol, this study tried to develop a carbohydrate selective catalytic hydrogenolysis system to get higher catalytic activity and selectivity under mild conditions. Accordingly, this paper designed catalysts loading Ru by using different carriers to study the methods for adjusting the catalyst activity center and surface physico-chemical properties, to make sure the catalysts can keep a good hydrogenation activity of small molecule intermediates, and decrease the hydrogenation activity of monosaccharide molecular as well. The research further studied the adsorption and selective bond-breaking path of carbohydrates on the catalysts. The results are as follows:(1) For different carriers (zeolite, hydrotalcite, hydrotalcite-like compounds, carbon nanotubes) loaded catalysts, the results showed that carbon nanotubes supported Ru catalysts which were prepared by impregnation showed the highest hydrogenation activity and the highest selectivity for target alcohols.(2) For different carbon nanotubes (amination, carboxylation, hydroxylation, graphitization and untreated) loaded catalysts, functionalized carbon nanotubes were more conducive for active metal load. Using sorbitol as substrate, the order of hydrogenolysis reactivity was Ru/ACNTs> Ru/CNTs> Ru/GCNTs> Ru/CCNTs> Ru/HCNTs.(3) The sorbitol was hydrogenolysed by using Ru/ACNTs as the catalyst under different alkali additives, the order of reactivity was LiOH> NaOH> Ca(OH)2> CaO> Mg(OH)2> Sr(OH)2> Ba(OH)2> KOH. Considering the conversion of the reactants, the yield and selectivity of the target products, it showed that Ca(OH)2 was the best base additives. Also the effects of the dosage of Ca(OH)2, the amount of catalyst, reaction time, temperature and initial hydrogen pressure were investigated on the catalytic reaction system of hydrogenolysis. It showed that nearly 93.9% of sorbitol was converted,55.2% yield and 58.5% selectivity to ethylene glycol and 1,2-propylene glycol could be achieved under the condition of 200?, initial hydrogen pressure 5 MPa, reaction time 2 h, using Ca(OH)2 (0.5 g) as additive and Ru/ACNTs (0.3 g) as catalyst.