Preparation Of Metal Organic Frameworks Cu-(BTC)Immobilized HPW For The Esterification Of Cyclohexene With Formic Acid

The preparation of cyclohexanol by indirect hydration of cyclohexene can effectively overcome the thermodynamic limit of direct hydration and reduce the energy consumption of the reaction system,and it has a good application prospect.Indirect hydration method consists of esterification of cyclohexene and formic acid to form cyclohexyl formate and hydrolysis of ester to form cyclohexanol two step reaction.The esterification of cyclohexene and formic acid is a typical acid catalysis reaction,and it is also the key step for the realization of indirect hydration.The development of catalysts with strong acidity and high acid content is the focus of this study.In this thesis,phosphotungstic acid(HPW)was used as active component and metal organic frameworks Cu(BTC)as carrier.The supported catalyst HPW-Cu(BTC)was prepared by three methods.Its structure was systematically characterized.Its catalytic performance was evaluated in the esterification of cyclohexene and formic acid.The work was aimed to provide effective technology accumulation for the development of cyclohexanol by indirect hydration.Firstly,a supported catalyst HPW-Cu(BTC)was prepared by one-step hydrothermal synthesis method using Cu(NO3)2 · 3H20 as copper source and trimesic acid(H3BTC)as ligand..The effects of HPW loading on the structure and properties of the catalysts were investigated.The results indicated that when the material ratio is m(HPW):m(Cu(NO3)2 · 9H2O):m(HBTC)=2.0:2.4:2.1,the catalyst prepared has a good pore structure,and the loading capacity of HPW is 33.7%..Then the process conditions were systematically studied,under the conditions of 120? for 12h,the amount of the catalyst was 8wt%of the total amount of the reaction liquid and the molar ratio of formic acid to cyclohexene was 3:1,the conversion of cyclohexene was 69.5%and the selectivity of cyclohexyl formate was 98.5%,Secondly,HPW-Cu(BTC)was prepared by template hydrothermal method using hexadecyl trimethyl ammonium bromide(CTAB)and N,N-dimethylformamid(DMF)as template..The results showed that the templates can improve the deprotonation ability of organic ligands and facilitate the formation of catalyst structure.The catalyst prepared by DMF as template is low in crystallinity and covered with oxide on the surface.CTAB is a relatively ideal template.When the amount of CTAB is m(CTAB):m(HBTC)=0.2:2,the structure of the catalyst is complete and the pore size is raised to 3.8 nm,which is beneficial to the free entry of the reactant molecules into the channel and the reaction,and the agglomeration of the catalyst particles is solved.The conversion of cyclohexene was improved to 77.2%,and the selectivity of cyclohexyl formate is 94.2%by using catalyst with CTAB as template for esterification.Finally,using p-methylbenzoic acid(PTA)as a regulator,the crystal structure of HPW-Cu(BTC)is modulated during the preparation process,and the catalyst is converted from the original eight facet structure of the {111} surface to the cubic structure of the {100}surface..The transformation of crystal face reduced the formation of perforation.At this time,the loading amount of catalyst HPW was 14.3%,and more active sites were exposed.The experiments indicated that at M(PTA):m(BTC)-20,the crystal surface of the catalyst is completely covered by the {100} crystal surface.The conversion of cyclohexene is increased to 87.2%and the selectivity of cyclohexyl formate is 97.6%in the esterification reaction..The catalyst still maintains better catalytic activity than the {111} crystal catalyst in the reaction mixture according to the ratio of industrial raw materials.The characterization of the recovered catalyst indicated that the polar reaction system caused partial damage to the structure of the catalyst,resulting in a decrease in catalytic performance.