| With the acceleration of the industrial development,fossil fuels on the earth are increasingly exhausted and the energy crisis is gradually approaching.Biomass,as a sustainable and abundant resource on the earth,has been gradually developed to alleviate the energy crisis.In the presence of suitable catalyst,biomass can be gradually transformed into various functional small molecules,and gamma-valerolactone(GVL)is one of them.GVL has certain research value because it can be used as fuel additive,solvent and precursor of many high value-added fine chemicals.It is very important to find efficient and environment-friendly catalyst for biomass preparation of GVL.This subject is mainly on inorganic-organic zirconium phosphonate materials as catalyst,catalysing ethyl levulinate for preparing gamma-valerolactone,and the catalysts with good effect were applied to the catalytic hydrogenation reaction of other carbonyl compounds.The research contents include the following three aspects:(1)Zirconium pyrophosphate(Zr OPP)was synthesized by a simple coprecipitation method and the catalyst was characterized by IR,pyridine IR,scanning electron microscopy,transmission electron microscopy,N2 adsorption desorption,CO2 and NH3 temperature programmed desorption characterization,which were used to analyse the structure and internal distribution of acid-base sites in the catalyst.Using the catalyst in the conversion of EL to GVL,we explored the effect of reaction time,temperature,amount of catalyst,zirconium phosphorus ratio,solvent and other factors on the catalytic activity.The results showed that 5 m L isopropanol was used as solvent and hydrogen source,0.1710 g naphthalene as an internal standardand,and zirconium phosphorus ratio of 1:1 Zr OPP as catalyst,ethyl levulinate reacted 11 h at 160 o C,EL conversion and GVL yield could reach97.4% and 94.1%,respectively.The catalyst leaching experiments showed that the catalytic reaction was heterogeneous catalysis.The recycle performance of Zr OPP was investigated.After five cycles,the apparent structure and element content did not change significantly.So the catalyst has good cycling performance and stability.(2)Selecting organic phosphonic acid with functional groups as precursor,we prepared four organic zirconium phosphonate catalysts,which were characterized by a series of methods to explore apparent structure and element content.The prepared catalysts were used to transform EL into GVL,exploring the effect of reaction time,temperature,amount of catalyst and zirconium phosphorus ratio on catalytic hydrogenation reaction of EL.The results obtained,5 m L isopropanol as solvent and hydrogen source,0.1710 g naphthalene as an internal standardand,and zirconium phosphorus ratio of 1:1,Zr HEDP as catalyst,the reaction at 160 o C for 12 h,EL conversion and GVL yield were 98.6% and 92.3%;Zr EDTMPs as catalyst,the reaction at 160 oC for 9 h,EL conversion and GVL yield were98.1% and 88.4%;Zr ATMP as catalyst,the reaction at 160 o C for 11 h,EL conversion and GVL yield were 98.4% and 89.9%;Zr DTPMPA as catalyst,the reaction at 160 o C for 11 h,EL conversion and GVL yield were 90.4% and 73.2%.As shown in experimental results,with-OH group in the structure of Zr HEDP,improving the overall number of Br?nsted acid sites,(3)which is conducive to the lactonization of 4-hydroxypentanoate to achieve a higher yield of GVL;with N in the structure of Zr ATMP and Zr EDTMPs,improving the overall number of basic sites,which is in favor of the dissociation of isopropanol to promote the hydrogenation of carbonyl group in EL,finally to get a higher yield of GVL;with poor symmetry and low active sites in precursor of Zr DTPMPA,which lead to poor stability and smaller BET area,so the result on conversion from EL to GVL is poor.(4)The four catalysts which converted EL into GVL with good effect were applied to catalytic hydrogenation of other aldehydes and ketones,including furfural,benzaldehyde,4-methyl-2-pentanone,2-heptanone,2-octanone,cyclohexanone and acetophenone.Through the condition optimization on the reaction time and temperature,it could be found that the catalysts have good catalytic activity for the catalytic hydrogenation reaction of aldehydes and ketones.Compared with ketones,aldehydes are easier to achieve catalytic hydrogenation because of lower steric hindrance effect.For the straight chain ketones,the shorter carbon chain,the better symmetry,they are easier to achieve catalytic hydrogenation.The existence of double bond or benzene ring in ketone compounds to form conjugated structure with carbonyl,because of taking up active centers.So more severe conditions are needed to achieve catalytic hydrogenation. |
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