Study On The Catalytic Synthesis Of Levulinic Acid Long-chain High-carbon Esters

Biomass is the most abundant renewable resource on earth,and its development and utilization is of great significance to alleviate energy shortage and promote sustainable development.Alkyl Levulinates?ALs?is an important organic chemical that converts from biomass,and has important application prospect in chemical,food,spices,medicine and other fields.Recent studies have shown that,ALs can be used as fuel additives,because ALs contains a certain amount of oxygen,it can promote the fuel burn adequately,at the same time,ALs can reduce NO_x emissions from the burning of fuel.Through the adjustment of alkyl carbon chain,ALs could change the carbon content of the fuel,improve the calorific value of fuel,high carbon levulinate esters expected to become a new generation of biofuels.Currently,the synthesis of ALs by biomass conversion has received widespread attention,but the synthesis mainly focuses on the synthesis of low carbon levulinate esters,while the synthesis of high carbon levulinate esters is rarely reported.The study on the synthesis of high carbon levulinate esters is of great significance for the further utilization of biomass.In this paper,a bio-based platform compound levulinic acid?LA?was used as raw material,mainly research the catalytic reaction of esterification of n-hexyl levulinate?n-HL?.Different metal chloride and metal-supported heteropoly acid were used as catalysts to explore the influence of different reaction factors on thereaction activity of catalysts,researching the reaction mechanism of esterification process,providing a theoretical reference for synthesis of high carbon levulinate esters from LA.The main research contents are as follows:?1?The synthesis of n-HL was catalyzed by LA esterification with different metal chlorides.Among the investigated metal chlorides,WCl6 showed the best catalytic activity at low temperature.WCl6 with acid molar mass of 10% was used as catalyst,and the reactant with acid alcohol molar ratio of 1:5 was used to react at 50? for 30 min.The LA conversion rate was 98% and the yield of n-HL was 84%.In the catalytic performance test of different isomerized hexanol and 1-octanol,WCl6 also showed good catalytic effect,with LA conversion up to 99% and n-HL yield up to 82-91%.?2?Based on the research of metal chloride catalyst,this paper respectively loads phosphotungstic acid?H3PW?and silicotungstic acid?H₄SiW?with Ta and Hf,Ta_0.6PW,Hf0.75 PW,Ta0.8Si W,Hf Si W,four heterogeneous catalysts were obtained.By comparing the catalytic effect of different reaction temperatures,Ta0.8Si W showed the great catalytic activity.By changing the Ta loading,Ta/Hx Si W series catalysts were preparedand characterized by XRD and FT-IR.Through the detailed exploration of the influencing factors,Ta0.8Si W with acid mass fraction of20% was used as the catalyst,the reactant with the molar ratio ofacid-alcohol 1:5 was used to react at 80? for 60 min,the conversion of LA was 97%,the yield of n-HL was 78%,and the yield of n-HL was 92%after the reaction at 120? for 60 min.Ta0.8Si W had a good catalytic effect on the synthesis of n-HL from LA.