Synthesis And Catalytic Performance Of Containing Sn Mesoporous Molecular Sieve For Baeyer-Villiger Oxidation Of Cyclohexanone

?-Caprolactone is an important organic intermediate and monomer with wide application.In terms of raw material,production process and economic benefit,Baeyer-Villiger oxidation of cyclohexanone is the most effective method for the production of ?-caprolactone and it is also the main method for industrial production.Because of the huge potential safety hazard and the by-product carboxylic acid of the peroxy acid oxidants used in industry,the use of low concentration H2O2,tert butyl peroxide(TBHP)or cyclohexyl hydrogen peroxide(CHHP)as oxidant has the advantages of high utilization rate of oxygen atom,easy economy and simple post-processing,which is in line with the concept of green chemistry.However,the oxidation capacity of these three oxidants is not strong and the carbonyl group can not be activated directly.Therefore,the development of high active catalyst has become the focus of the research on the production of?-Caprolactone by cyclohexanone Baeyer-Villiger oxidation reaction.Firstly,Sn was loaded onto the mesoporous molecular sieve MCM-41 carrier by chemical vapor deposition(CVD),ion exchange(TIE)and impregnation method.The obtained Sn-MCM-41 was compared with the one prepared by direct hydrothermal synthesis(DHT).In addition,four kinds of catalysts were modified by silylation.The detailed characterizations of the obtained samples are determined with FT-IR,UV-Vis,XRD,N,physical adsorption,TG techniques and Element analysis.The catalytic performance are evaluated by the Baeyer-Villiger oxidation of cyclohexanone with TBFHP and CHHP as oxidant.The results showed that CVD method is a good method to prepare Sn-MCM-41 catalyst.The catalyst skeleton contains more Sn(IV)with Lewis acid,which can catalyze the Baeyer-Villiger oxidation of cyclohexanone effectively.When TBHP was used as oxidant,the conversion of cyclohexanone was 30.83%and the selectivity of caprolactone was 27.82%.Because of CHHP's weak oxidation capacity and the solvent effect is not obvious,only the catalyst synthesized by CVD method showed the activity used CHHP as oxidant.Silane modification will improve the hydrophobicity of the catalyst.whichh make the reactants more accessible to the active sites of Sn.thus increasing the selectivity of caprolactone.In this thesis,a mesoporous molecular sieve SBA.-15,which is similar to the MCM-41 structure,is also selected to prepare the Sn containing catalyst by chemical vapor deposition(CVD)using the anhydrous SnCl4 as the tin source.The influence of the ratio of peroxide to ketone on the reaction performance of cyclohexanone Baeyer-Villiger oxidation with CHHP as oxygen source was also investigated.FT-IR,UV-Vis,XRD,N2 physical adsorption,ICP-AES?NH3-TPD and pyridine infrared spectra were used to characterize the two species.The results showed that the content of four coordinated Sn(IV)in Sn-MCM-41 skeleton is higher than that in Sn-SBA-15,and L acid is stronger than Sn-SBA-15.The catalytic activity of Sn-MCM-41 for cyclohexanone Baeyer-Villiger oxidation with CHHP as oxygen source is better than that of Sn-SBA-15.SnO2 in the catalyst is responsible for the invalid decomposition of peroxide,when the molar ratio of CHHP to cyclohexanone is 1:1,the catalytic activity was reduced.When CHHP was excessive,the selectivity of ?-caprolactone was 4.48%.Finally,the influence of carrier pretreatment is also investigated.The MCM-41 mesoporous molecular sieves were calcined and hydrothermal pretreated respectively,then Sn was loaded by chemical vapor deposition.Comparative characterization and performance evaluation were compared with the catalyst without carrier pretreatment.The samples are characterized by FT-IR,UV-Vis,XRD,N2 physical adsorption,ICP-AES,NH3-TPD and vacuum IR,the results showed that pretreatment can change the distribution of the silanol hydroxyl groups on the surface of the carrier,and reduce tbhe formation of six-coordinate tin and SrnO2 in extra-framework.Hydrothermal pretreatment I can increase the proportion of vicinal silanol,which is favorable for Sn to enter the framework of molecular sieves and bond with silanol group to form four coordinated Sn(IV)with,catalytic activity.The catalyst obtained without any pretreatment is prone to produce a large number of extra-framework Sn02 species.For the Baeyer-Villiger oxidation of cyclohexanone with H2O2 as oxidant,the catalyst by hydrothermal pretreatment showed best catalytic activity with the conversion of cyclohexanone 48.7%and the selectivity of ?-caprolactone 38.3%,the number of TON was up to 869.