Structural Load Construction And Application Of Heteropoly Acid Composite Microspheres

The study of biphasic catalysis has attracted wide interests.Considerable research findings showed that micellar phase-transfer catalysis has obvious advantages.However,separation of both surfactants and products is relatively difficult.Therefore,enhancement of biphasic catalysis and simplization of process in separation and recovery of the catalysts and products are still significant for theory and application.Based on the micellar phase-transfer catalysis features and our previous works related to preparation of core-shell composite microspheres,a novel method for preparation of composite microspheres with microgel core and phase-transfer catalyst shell was proposed in this thesis.This kind of composite microspheres has the feature of micellar phase-transfer catalysis and the advantage in separation.Based on the idea mentioned above,the main contents of this thesis include four aspects as follows:1 Preparation of the composite microshperes by using copolymer microspheres of surfmer (polymerizable surfactant) and AM as templatesSurfmer[3-(Acryloylamino)propyldodecyldimethylammonium bromide,APDDAB]has been synthesized and characterized.Based on the reverse emulsion polymerization technique,the copolymer microgels have been obtained by using copolymerization of AM and APDDAB.Then, the resulting copolymer microgels were placed in phosphotungstic acid(PWA) aqueous solution. Finally,the P(AM-co-APDDAB)/PW₁₂O₄₀ composite microspheres were prepared by ion-exchange reaction.The morphologies and compositions of the P(AM-co-APDDAB)/PW₁₂O₄₀ composite microspheres were characterized by scanning electron microscopy(SEM), thermogravimetric analysis(TGA) and Fouier transform infrared spectroscopy(FT-IR), respectively.The results indicated that the P(AM-co-APDDAB)/PW₁₂O₄₀ composite microspheres are of core/shell structure.For the composite microspheres,the hydrogel P(AM-co-APDDAB) dominantly locates in the core,and the complexes of PWA with APDDAB mainly locates in the shell.The structure of the P(AM-co-APDDAB)/PW₁₂O₄₀ composite microspheres is similar to that of the micellar phase-transfer catalyst.However,the composite microspheres are easy to be separated.2 Preparation of the composite microspheres by using the porous PAM microspheres immersed with APDDAB as templates The PAM/APDDAB-PWA composite microspheres were prepared by following method. Firstly,the water-swollen PAM microspheres were treated by the freeze-drying to obtain porous microspheres.Secondly,the porous microspheres were impregnated in methanol solution containing APDDAB.Then the PAM/APDDAB microspheres were placed in HPW aqueous solution for 7days.At last,the PAM/APDDAB-PWA composite microspheres were obtained.The morphologies and compositions of PAM/APDDAB-PWA composite microspheres were characterized by scanning electron microscopy(SEM),thermogravimetric analysis(TGA),Fouier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectra(XPS),inductive coupled plasma atom emission spectrometer(ICP-AES),and Elementar Analyzer,respectively.The results indicated that PAM/APDDAB-PWA composite microsphere with different hierarchical surface structures could be obtained by controlling the weight ratio of APDDAB to PAM microgels,cross-linking degree of PAM microgels,the amount of PWA reacted with APDDAB in PAM/APDDAB,and solvent-washing process.A general feature of PAM/APDDAB-PWA composite microsphere was of the core-shell structure and the wrinkly surface covered with APDDAB-PWA particles.The formation of the wrinkly surface is attributed to the difference in shrink between inside and outside of PAM microgel frameworks,and the formation of APDDAB-PWA small particles originates from the reaction between APDDAB aggregation and PWA.This composite microsphere with PAM hydrogel core is suitable to store water-soluble substances,and the shell composed of the surfactant/Keggin-type polyoxometalate complexes is not only amphiphilic but also catalytic.3 Preparation of the composite microspheres by using the quaterised PAM microspheres as templatesMannich reaction of PAM microgel with hydroxymethyl dimethylammonia was conducted in pH 9-11 aqueous solution.Then,resulting products were quarterized with dodecyl bromide.At last, the quaterised microspheres(CPAM) were placed in the HPW aqueous solution for ion-exchange. The CPAM/PWA composite microspheres were obtained.The morphologies and compositions of the CPAM/PWA composite microspheres were characterized by scanning electron microscopy (SEM),thermogravimetric analysis(TGA),X-ray photoelectron spectra(XPS) and Fouier transform infrared spectroscopy(FT-IR),respectively.The results indicated that the CPAM/PWA composite microspheres are of core/shell structure.For the composite microspheres,the hydrogel CPAM dominantly locates in the core,and the complexes of PWA with quaternary ammonium salt mainly locates in the shell.The structure of the CPAM/PWA composite microspheres is similar to that of P(AM-co-APDDAB)/PW₁₂O₄₀.The CPAM/PWA composite microspheres are mainly controlled by mole ratio of PAM to hydroxymethyl dimethylammonia.4 The catalytic performances of the PAM/APDDAB-PWA composite microspheres were systematically investigated by using dibenzothiophene(DBT) oxidized by H₂O₂ in decalin as a model system so that some key factors related to the catalytic performances of the composite microspheres were obtained.The results indicated that the PAM/APDDAB-PWA composite microspheres used as microreactors have excellent performances in ultra-deep desulfurization.Meanwhile,the microreactors are renewable.The results indicated that PAM/APDDAB-PWA composite microspheres can extract sulfoxide-the product of the oxidized DBT.So,the prepared PAM/APDDAB-PWA composite microspheres are of bifunctions in extaction and separation.The results indicated that swelling degree of PAM/APDDAB-PWA composite microspheres with H₂O₂ is very important in biphasic catalysis.The results indicated that the size of the PAM/APDDAB-PWA composite microspheres is a very important factor in the catalytic efficiency.The smaller PAM/APDDAB-PWA composite microspheres,the higher the catalyticaly efficiency.In summary,based on the results from application of the PAM/APDDAB-PWA composite microspheres in the ultra-deep desulfurization based on biphasic catalysis,the following conclusions for general biphasis catalysis could be obtained.Firstly,the composite microspheres with the hydrogel core and the shell composed of phase-transfer catalysts are feasibly used in biphasic catalysis,and the composite microspheres are easily separated from the reaction medium.