Preparation Of Inorganic Zirconium Phosphate Catalyst And Its Application In Catalytic Transfer Hydrogenation

With the rapid development of the global economy,fossil energy has been unable to meet the needs of industry,and environmental pollution problems have emerged endlessly.Therefore,it is urgent to develop new renewable green resources that can replace fossil energy.As a kind of renewable organic carbon resource with abundant reserves,biomass can be converted into various high value-added platform compounds through different chemical reactions.?-valerolactone(GVL)is one of the most important biomass platform molecules.It can be used as a gelling agents,additives,solvents and intermediate of related compounds.Therefore,it is of great significance to design and synthesize highly efficient and stable catalysts for the preparation of biomass platform molecules such as GVL.In this paper,two inorganic zirconium phosphate catalysts were firstly synthesized to catalyze the hydroesterification of ethyl levulinate(EL)to prepare GVL,and then the two catalysts were applied to the catalytic transfer hydrogenation(CTH)reaction of other carbonyl compounds.The specific research contents were as follows:(1)Three different metal-centered trimetaphosphate catalysts(Zr-TMPA,Sn-TMPA,Ti-TMPA)were synthesized and characterized.These three catalysts were used for the CTH reaction of EL to GVL.Then the effects of the type of catalyst,the amount of catalyst,the reaction temperature and reaction time on the CTH reaction were studied.The optimal reaction conditions and results were as follows:0.2 g Zr-TMPA could catalyze the reaction of 1 mmol EL with isopropanol as hydrogen donor at 160°C for 8 h to achieve 100%EL conversion and96.2%GVL yield.Subsequently,levulinic acid,methyl levulinate and butyl levulinate were used as substrates for the preparation of GVL,and it was found that Zr-TMPA also exhibited a good catalytic effect.Finally,the reason why the Zr-TMPA catalyst has high activity was analyzed,and a possible reaction mechanism was proposed by means of the catalyst poisoning experiment.(2)A series of porous acid-base bifunctional zirconium tripolyphosphate catalysts(Zr-TPPA-X)were synthesized for catalyzing the CTH reaction of EL to GVL.The characterization results and experimental results consistently showed that Zr-TPPA-3 with a large number of Lewis acid-base sites and high specific surface area was the most active catalyst.Under the optimal reaction conditions(0.2 g Zr-TPPA-3,160 ~oC,8 h,IPA as the hydrogen source),the EL conversion and the GVL yield were 99.5%and 93.1%,respectively.In addition,catalyst leaching experiments indicated that Zr-TPPA-3 was a heterogeneous catalyst in the reaction system.The results of recycling of the catalyst showed that Zr-TPPA-3 could still maintain high catalytic activity after 5 cycles.(3)In view of the excellent catalytic activity of Zr-TMPA and Zr-TPPA-3 catalysts in the CTH reaction of EL to GVL,the two catalysts were first used in the hydrogenation of furfural(FF)to furfuryl alcohol(FA).The results showed that both catalysts could achieve good catalytic effect.The apparent activation energy of the reaction was then calculated by reaction kinetics and it was found that the catalytic activity of Zr-TMPA was indeed slightly higher than that of Zr-TPPA-3.Finally,the two catalysts were extended to the CTH reaction of other carbonyl compounds,and the results indicated that each carbonyl compound could be efficiently converted into the corresponding target product.In addition,it was observed that the aldehyde substance was more likely to undergo transfer hydrogenation than the ketone substance.