Hydrogenolysis Catalysts For Lower Carbon Glycols Production From Sugar Alcohol Mixture

With the growing awareness of environmental protection and the increasing depletion of fossil resources,the chemicals production of propylene glycol,ethylene glycol and butylene glycol by using sugar alcohol is of great significance for the sustainable development of human society.As a big agricultural producer,China has a good foundation on carrying out the research in this area.The development of new and efficient sugar alcohol hydrogenolysis catalysts will help to improve the green technology and economy of sugar alcohol hydrogenolysis.Noble metal catalysts involve after all the economical issues.In this paper,three nickel-based bimetallic catalysts were prepared by using nickel as active metal and by changing the carrier,adding modified metals and changing the preparation methods.The active metal structure and state on the catalysts were studied through detailed catalyst characterization,and catalyst activity,selectivity and stability were evaluated through sugar alcohol mixture hydrogenolysis tests.The metal states of three catalysts were analyzed,based on the characterization results,and the reasons for good performance were explored,as well as the reaction mechanism was presumed,in combination with the reacted products distribution and catalyst preparation methods.Through recycled reaction tests,a preliminary study on the catalyst stability was made.The main work and research results of this paper are as follows.（1）Six nickel and ruthenium catalysts were selected,and polyol mixture hydrogenolysis tests were made.Test apparatus,and analysis methods were established in this process to determine the reaction parameters and to screen out nickel-containing dienes hydrogenation catalyst and desulfurization catalyst with better performance,and the results for future research were explored.（2）The reduced-state NiRu/clay catalyst was prepared by using Ni/clay catalyst as carrier and RuC1₃ hydrate as Ru precursor,which was able to catalyze the hydrogenolysis reaction to produce lower-carbon glycols with C₅ and C₆ sugar alcohol mixtures as raw materials.With XRD,TEM and XPS characterization methods,it proved that the addition of ruthenium to nickel-containing catalyst,the conversion rate of C₅ and C₆ sugar alcohol mixtures decreased slightly（reaches91.2%）,but the total selectivity of lower-carbon glycols increased from 38.9%to74.1%.The addition of ruthenium significantly improved the selectivity of lower-carbon glycols.In the product,propylene glycol held the highest proportion,1,2-propanediol,and ethylene glycol followed.（3）The Ni-Ru/C catalyst prepared using two-step process was suitable for sugar alcohol mixture hydrogenolysis.The conversion rate was more than 94%,and selectivity was over 71%.Glycol product was mainly composed of 1,2-propanediol,ethylene glycol and 1,2-butylene glycol.The introduction of ruthenium significantly improved the catalyst selectivity,made nickel particle size smaller and more even dispersion,and the existing forms of nickel and ruthenium were oxides on Ni-Ru/C catalyst.（4）The NiSn/C catalyst prepared using one-step precipitation process was suitable for the hydrogenolysis reaction to produce lower-carbon glycol from C5 and C6 sugar alcohol mixtures.The introduction of Sn greatly improved the catalyst selectivity,mainly attributed to the formation of alloy nanoparticles of Ni₃Sn₃,Ni₁₇Sn₃ and Ni₃Sn₄.The NiSn/C catalyst prepared using two-step process almost had no catalytic activity on sugar alcohol mixture hydrogenolysis.It was probably caused by the phenomenon that Sn tightly surrounded Ni,and the formation of the core-shell structure that Ni outside and Ni inside made Ni fail in hydrogenation.Sn itself had no activity of hydrogenation,and the catalytic activity mainly relied on Ni.（5）The three nickel-based catalysts developed in this paper could obtain higher conversion and selectivity for the sugar alcohol mixture hydrogenolysis,and the main products were 1,2-propanediol and ethylene glycol.The conversion of sugar,yields and selectivity of glycols are as follows:Ni-Sn/C>Ni-Ru/C>Ni-Ru/clay,Ni-Ru/clay>Ni-Sn/C>Ni-Ru/C and Ni-Sn/C>Ni-Ru/clay>Ni-Ru/C,respectively.The metal dispersion and existing form on catalysts directly impacted the catalyst performance.During the catalyst preparation,passivation in air after reduction could ensure the catalysts to be stored normally in the air,no special measurements needed.（6）Low carbon diglycol is base chemical material and have a big demand.As the raw material pure sugar alcohols are far from enough to meet the growing demand whaterever quantity and price.Finding new material instead of pure sugar alcohol necessary for the hydrogenolysis process.This paper adopted sugar alcohol mixture as material to manufacture low carbon diglycols and get satisfied conversation,selectivity and yields.The material cost decreases a lot and have a better economic value.