| Ethylenediamine is an important organic chemical raw material.At present,the production capacity of ethylenediamine in China is insufficient,and the existing industrial production has the defect of unfriendly environment.With the rapid development of biodiesel industry,the problem of overcapacity of glycerol has emerged.Therefore,the reactions of glycerol hydrogenolysis to ethylene glycol and amination of ethylene glycol to ethylenediamine were investigated successively in the present thesis which will provide the basis for a novel process of the direct synthesis of ethylenediamine from biomass glycerol via ethylene glycol.Firstly,the catalytic hydrogenolysis of glycerol to ethylene glycol was studied.To determine the most possible pathway,a thermodynamic analysis for retro-aldol and decarbonylation pathway of glycerol hydrogenolysis to ethylene glycol was performed using Aspen Plus software.After that,the catalyst for glycerol hydrogenolysis to ethylene glycol was studied.A series of supported single metal catalysts were prepared by excessive impregnation method.Among them,Ru/Ti O2 showed the best catalytic performance for glycerol hydrogenolysis.Combined with NH3-TPD and CO2-TPD characterization and activity evaluation of Ru-based catalysts with different carriers,it can be seen that metals are the main factor influencing the selectivity of ethylene glycol;the glycerol conversion is positively correlated with catalysts’acid amount and the ethylene glycol selectivity is essentially negatively correlated with catalysts’base amount.In order to improve the catalytic performance,the effect of different metal oxide promoters and preparation conditions on the catalytic performance of Ru/Ti O2 was investigated.It can be observed that Ru/La-Ti O2 had the highest catalytic activity for glycerol hydrogenolysis.The appropriate preparation conditions of Ru/La-Ti O2 were obtained as follows:a rutile Ti O2 as support,a Ru loading of2 wt.%,a La addition of 5 wt.%,a reduction temperature of 300℃and a reduction time of4 h.Based on the results of XPS characterization and activity evaluation,it can be concluded that the addition of La species promotes the reduction degree of Ru and the ethylene glycol selectivity is improved with the increasing of Ru atomic ratio on the catalyst surface.The effect of reaction conditions on glycerol hydrogenolysis was also studied by single-factor experiments and the suitable reaction conditions were obtained as follows:a reaction temperature of 210℃,a hydrogen pressure of 7 MPa,a glycerol concentration of 20 wt.%,a catalysts mass of 8 wt.%and a reaction time of 2 h.Under these conditions,the selectivity of ethylene glycol was 47.9%,the total selectivity of diol was 89.4%,and the selectivity of total alcohol was 97.0%.On this basis,by comparing the results obtained from the data of catalyst characterization and activity evaluation with those obtained from thermodynamic simulation,it is speculated that glycerol hydrogenolysis to ethylene glycol over Ru/La-Ti O2catalysts is likely to proceed with the route of glycerol dehydrogenation followed by decarbonylation directly.Secondly,the catalytic amination of ethylene glycol to ethylenediamine was studied.Based on Ru/La-Ti O2 for glycerol hydrogenolysis,the Co-Ru/HAP showed a better catalytic performance by introducing different loadings of main active metal Co,changing the kind of second metal components,as well as modifying the carrier.The influences of preparation conditions on the catalytic performance of Co-Ru/HAP were evaluated and its appropriate preparation conditions were obtained as follows:a p H value of 10,a metal loading of 9 wt.%,a mass ratio of Co to Ru of 10:1 and a reduction temperature of 500℃.Under these conditions,the conversion of ethylene glycol was 30.2%,the selectivity of ethylenediamine,the sum of the selectivity of ethylenediamine and ethanolamine and the selectivity of piperazine can reach 35.4%,58.0%and 16.0%,respectively.The catalysts were characterized by H2-TPR,XRD,ICP,BET,NH3-TPD and CO2-TPD,respectively.Combined with the catalyst characterization and activity evaluation,it is found that there is an obvious synergistic effect between metal Co and Ru;Metal Co mainly facilitates dehydrogenation and hydrogenation steps in ethylene glycol amination,while metal Ru mainly inhibits the adsorption of NH3 on the surface of metal Co,which can ensure more Co metal sites are preserved to activate ethylene glycol.The acid-base active sites of the catalyst have obvious synergistic effect,and the basic sites and acidic sites are respectively beneficial to dehydrogenation step and imine hydrogenation step in amination reaction.Then a qualitative analysis for the amination of glycerol was performed by GC-MS analysis,and the reaction network of Co-Ru/HAP catalyzing ethylene glycol amination was established. |
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