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Synthesis Of Temperature Sensitive P?DEA-co-DMAEMA?/Na2WO4 Hydrogel And Its Catalytic Behaviors Toward Oxidation Of Benzyl Alcohol

Posted on:2018-11-10Degree:MasterType:Thesis
Country:ChinaCandidate:J J MaFull Text:PDF
GTID:2321330533956381Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Sodium tungstate dihydrate?Na2WO4·2H2O?is an important transition metal catalyst which is widely used in the oxidation of alcohols and olefins.But due to the separation of water-organic two-phase,Na2WO4 and substrate are only in contact with the two phases which leads to very low catalytic efficiency.Thermo-sensitive hydrogels are widely used in the field of catalysis due to their unique three-dimensional network structure and special phase transition behavior.The catalytic efficiency could be improved due to the enrichment of the catalyst and substrate by the shrink of the volume with the rise of environmental temperature.In this thesis,Na2WO4 was loaded by one pot and impregnation method respectively,and the structure and properties of hydrogels were studied.Besides,the green oxidation of benzyl alcohol was achieved by the use of hydrogen peroxide?H2O2?as oxidant,and thermo-sensitivity and interaction between polymers and Na2WO4 were explored with respect to catalytic performance.Main contents are as follows: 1.Temperature and pH sensitive poly?N,N-diethylacrylamide-co-dimethylaminoethyl methacrylate??P?DEA-co-DMAEMA??hydrogel was synthesized by one pot method.The structure and composition of the hydrogel were determined by FT-IR and SEM.The result of rheological test showed that there existed a physical cross-linking?hydrogen bonding and coordination?between Na2WO4 and polymers in addition to chemical cross-linking in composite hydrogel.The storage modulus of the composite hydrogel increased with the increasement of Na2WO4 content.When the content of Na2WO4 was 3%,the storage modulus of the hydrogel reached 2.26 kPa.The hydrogel also exhibited excellent temperature and pH sensitivity,and both of the sensitivities could be adjusted by varying the Na2WO4 content.2.P?DEA-co-DMAEMA?/Na2WO4 hydrogel which was prepared by one pot method was used as catalyst to catalyze the oxidation of benzyl alcohol with H2O2 as oxidant in aqueous phase.The composition and thermal stability of P?DEA-co-DMAEMA?/Na2WO4 hydrogel were determined by TEM and TG.The benzyl alcohol adsorption and desorption capacities of the hydrogel were studied.The effects of different catalysts,reaction temperature and catalyst dosage on the catalytic results were investigated.When the mass of D7:3W2 hydrogel was 1.0 g,n?H2O2?: n?benzyl alcohol?=1:1,and reacted at 80°C for 14 h,the conversion of benzyl alcohol was 23.1%,while the selectivity and yield of benzaldehyde reached 84.4% and 19.5%,respectively.However,Na2WO4 dropped from the polymer matrix due to the weak interaction between Na2WO4 and polymers.3.The P?DEA-co-DMAEMA?/Na2WO4 hydrogel catalyst was prepared by impregnation method using P?DEA-co-DMAEMA?hydrogel as supporter to adsorb Na2WO4 in the acidic environment.As a result,there existed electrostatic interaction between protonated amine groups in hydrogel and Na2WO4.The structure and dosage of catalyst were determined by FT-IR,SEM and TG.The catalytic performance of the oxidation of benzyl alcohol was also studied.When the mass of D7:3/W hydrogel was 0.05 g,n?H2O2?: n?benzyl alcohol?=1:1,and reacted at 80°C for 8 h,the conversion of benzyl alcohol was 30%,while the selectivity and yield of benzaldehyde reached 66% and 19.8%,respectively.Compared with the composite hydrogel prepared by one pot method,the interaction between Na2WO4 and polymers is enhanced,so it has relatively good recycling capability.The conversion of benzyl alcohol was 19.1% after three cycles of recycling.
Keywords/Search Tags:temperature sensitive, hydrogel, Na2WO4, green oxidation
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