| Based on the metal-organic framework(MOFs),four new transesterification heterogeneous solid catalysts with excellent performance,adjustable function and controllable structure were prepared by functional design of MOFs and immobilization of amino-functionalized basic ionic liquids,heteropoly acid ionic liquids and organic guanidine compounds on the supports.FT-IR,XRD,SEM,TEM N2 adsorption-desorption method,TG,VSM,TG,ICP-OES and Hammett function titration method were used to characterize and determine the surface material composition,structure,properties(specific surface area,particle and pore size,acid-base properties,etc.).The results demonstrate that all kinds of catalytic activity centers are successfully loaded on MOFs,and the structure and properties of MOFs materials have not changed.The catalytic performance,separation performance and stability of the prepared catalyst was evaluated,and the characteristics of the active center and the mechanism of catalytic performance regulation were revealed.The preparation process of Fe3O4@HKUST-1-ABILs comprises the following steps of:firstly,preparing a core-shell structure Fe3O4@HKUST-1-ABILs with a magnetic core and a porous metal-organic framework shell by a layer-by-layer self-assembly method;and then coordinating an unsaturated site of the metal ion Cu2+ of the MOFs material with an alkaline ionic liquid to obtain a multiphase solid base catalyst.The optimum conditions were as follows:the reaction temperature was 65 ?,the amount of catalyst was 1.2%wt,the molar ratio of methanol to oil was 30;1 and the conversion rate of soybean oil reached 92.3%within 3 h.The solid base catalyst can be easily recovered by a simple external magnetic field and reused five times without significantly reducing its catalytic activity.The solid catalyst has the characteristics of good stability,strong structure,easy recovery and the like,and is particularly suitable for industrial chemical processes.The synthesis of AILs/HPA@UiO-66-2COOH catalyst adopts a new strategy of"shipbuilding in bottles".The main environment is provided by the mesoporous cage of the MOFs material UiO-66-2COOH,and the heteropoly acid ionic liquid is immobilized in the pore channels of the MOFs material by a packaging method,so that the loading rate of the ionic liquid is greatly improved,and the problem of easy loss of active components is well alleviated.The structure and catalytic properties of three heteropoly acid ionic liquid heterogeneous solid acid catalysts(AILs/HPW@UiO-66-2COOH.AILs/HSiW@UiO-66-2COOH AILs/HPMo@UiO-66-2COOH)were compared.Taking AILs/HPW@UiO-66-2COOH as an example,the optimum conditions were as follows:the reaction temperature was 110?,the amount of catalyst was 10%wt,the molar ratio of methanol to oil was 35;1 and the conversion rate of soybean oil reached 95.8%within 6h.The solid acid catalyst can be easily recovered by simple reduced-pressure filtration and reused five times without significantly reducing its catalytic activity and no significant loss of active components is discovered.The water resistance,acid resistance and esterification performance of the solid acid catalyst were studied by adding water and free fatty acid to the oil to simulate the low-quality oil with high acid value.The solid acid catalyst has the characteristics of good stability,firm structure,easy recovery,superior water resistance,FAA performance and the like,and is particularly suitable for industrial workers to catalyze inferior oil with high acid value.Preparation of AILs/HPMo@MIL-100(Fe)heterogeneous solid acid catalyst also adopts the method of" building a ship in a bottle".The mesoporous cage of MOFs material MIL-100(Fe)is used to provide the main environment,and phosphomolybdic acid ionic liquid is immobilized in the cage-window structure of the MOFs material.The results showed that the solid acid catalyst greatly improved the loading rate of ionic liquid on the basis of not destroying the carrier structure,and well alleviated the problem of easy loss of active components.Optimal reaction conditions of transesterification catalyst by solid acid were examined by single factor analysis.The conversion rate of soybean oil could reach 92.30%when the substrate ratio was 30:1,the amount of catalyst was 10%,and the reaction time was 8 hours at 120?.The solid acid catalyst can be easily recovered by simple reduced pressure filtration,and reused for five times without significantly reducing its catalytic activity,and no obvious loss of active components was found.The structure,morphology and performance of the catalyst remained unchanged before and after the reaction,which showed that the solid acid catalyst also had the characteristics of good stability,easy recovery,good water resistance and FAA performance,and was suitable for transesterification of inferior oil with higher acid value.The ZIF-90-Gua catalyst is prepared by reacting organic guanidine with an aldehyde group on ZIF-90 framework material in the form of covalent bond,and fixing on the zeolitic imidazole ester framework.After loading organic guanidine,the structure and properties of ZIF-90 framework materials remained unchanged.ZIF-90-Gua catalyst was employed in the transesterification of soybean oil and methanol by heterogeneous catalysis.The optimum reaction conditions were studied as follows:the ratio of reactants to substrate was 15;1.The amount of catalyst was 1.0%,and the conversion rate of soybean oil was 95.36%at 65? for 6h.The solid base catalyst can be easily recovered by a simple reduced-pressure filtration method and reused five times without significantly reducing its catalytic activity and no active center leakage phenomenon is found.The solid base catalyst has the characteristics of good stability,high catalytic performance,easy recovery and the like,and is suitable for industrial chemical processes. |
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