Preparation Of SO₄^2-/TiO₂-Y₂O₃ Solid Superacids And Its Application In The Synthesis Of Ethyl Lactate

The traditional production based on lactic acid,ethyl lactate and ethanol as a raw material,concentrated sulfuric acid as a catalyst,benzene,toluene was removed as an agent with the reaction of water to direct esterification of ethyl lactate.However,the process by-product and more serious corrosion of equipment,the production cost is high.compared with the conventional catalyst of sulfuric acid,solid super acid capable of activating acid-catalyzed reactions under relatively mild conditions,but also has high selectivity,fewer side effects,and easily separated from the reactants,equipment corrosion,can be reused,waste catalyst treatment is simple and less environmental pollution and other advantages.Therefore,this paper proposed a benign preparation method of EL via direct esterification from HL and EtOH using the solid super acid SO42-/TiO2-Y2O3 as catalyst,which was based on the drawbacks of traditional synthetic method.The research focused on the following aspects:(1)Use Y2O3 modify The solid super acid catalyst TiO2/SO42-which was prepared by impregnation method.The orthogonal test was employed to optimize the synthesis method of solid super caid catalyst and the more suitable synthesis method was obtained:the concentration of sulfuric acid solution 2mol/L,the sulfuric acid solution was used in solution of Y2O3 0.015mol/L,the calcination temperature 450℃,the drying temperature 90 ℃ and the calcination time 4h.Then get the best solid super acid S042-/TiO2-Y2O3 powder.(2)The reaction kinetics for the liquid phase synthesis of ethyl lactate over solid super acid Catalyst was investigated in a stirred batch reactor.By elimination of internal and external diffusion,the influences of catalyst dosage,reaction temperature and molar ratio of HL to EtOH on the esterification were investigated.(3)The experiments of esterification synthesis of EL with HL and EtOH over 5O42-/TiO2-Y2O3 catalyst were carried out in the batch reactive distillation column.By using cyclohexane as entrainer,the operation factors,catalyst amount,reactant molar ratio and the reaction time on HL conversion were investigated.The results shown that the final conversion of HL could be promoted significantly by using this technology.When the catalytic loading was 4wt%,the EtOH/HL feed molar ratio was 4:1,the reflux ration was 2:1,the conversion of HL was above 88%in 4.5h.(4)The molding process of solid super acid SO42-/TiO2-Y2O3 was studied.The molding scheme was determined based on catalytic performance and the orthogonal test was used to optimize the molding formula of solid super caid catalyst SO42-/TiO2-Y2O3 and the more appropriate molding formula was that:binder 7wt%,reinforcing agent 20wt%,pore forming agent 2.5wt%,lubricant 4wt%and the others were solid super acid catalyst SO42-/TiO2-Y2O3.The structures of molded catalyst were characterized by BET,TG and XRD methods.The characterization results showed that the surface area was 20.56 m2·g-1,the average pore diameter was 17.16 nm,inner channel of the catalyst was still mesoporous.The tolerant temperature of molded catalyst was 600 ℃and the titanium dioxide molecule still existed in the form of anatase type,the catalytic performance of this catalyst was higher than others.