Catalytic Selective Oxidation Of Isobutane

Methyl methacrylate(MMA)has important applications in the fields of resins,adhesives,coatings,and rubber.Methacrylic acid(MAA)and methacrolein(MAL)are the raw materials for the synthesis of methyl methacrylate,respectively.At present,there are three main industrial methods for the synthesis of MAA and MAL:acetone cyanohydrin method,ethylene carbonylation,and isobutylene oxidation.The above synthesis method involves highly toxic hydrocyanic acid in the process of factory operation,and the acidic substance will corrode pipelines,increase maintenance costs,pollute the environment,and have high raw material costs.In order to solve the above shortcomings,the safe and non-polluting selective oxidation synthesis route of MAA and MAL from cheap isobutane has attracted much attention.In this thesis,three types of catalytic selective oxidation of isobutane to MAA or MAL were studied.(1)Selective oxidation of isobutane to MAA catalyzed by(Cs2.20Cu0.260V0.382)xPMo12O40 heteropolyacid catalysts:Among the(Cs2.20Cu0.260V0.382)xPMo12O40(x=1.3,1.1,1.0 and 0.88)heteropolyacid catalysts,the Cs2.20Cu0.260V0.38PMo12O40 catalyst was screened as a highly active catalysts for selectve oxidation of isobutane to MAA.It exhibited a isotutane conversion of,a MAA selectivity of,and a MAA formation rate of 0.68 mmolMAA·h-1·gcatalyst-1 under a reaction condition of i-C4H10:O2:N2=(1 atm,flow rate:600 mL·h-1·gcatalyst-1)at 335℃.As demonsrated by structural characterization and mechanistic study results,the medium lattice oxygen release rate and fast lattice oxygehn migration rate of Cs2.20Cu0.260V0.38PMo12O40 are responsible for the high MAA selectivity and isotutane conversion,respectively;meanwhile,the strong Br?nsted acid sites on Cs2.20Cu0.260V0.38PMo12O40 facilitated the MAA desorption and enhanced the MAA selectivity,whereas the strong Lewis acid sites strongly adsorbed MAA,leading to the polymerization of MAA into produces of high boiling points and the decrease of catalyst selectivity.(2)Selective oxidation of isobutane to MAL catalyzed by Cs0.3FexCoyMnBiMo12 mixed oxide catalysts:Among the Cs0.3FexCoyMnBiMo12 mixed oxide catalysts,the Cs0.3Fe1.5Co6MnBiMo12 catalyst was screened as a highly active catalysts for selectve oxidation of isobutane to MAL.It exhibited a isotutane conversion of 40.0%,a MAL selectivity of 31.4%,and a MAA formation rate of 6.73 mmolMAL·h-1·gcatalyst-1,catalyst under a reaction condition of i-C4H10:O2:N2=10:20:2(1 atm,flow rate:3840 mL·h-1·gcatalyst-1)at 375℃.As demonstrated by structural characterization and mechanistic study results,α-Bi2Mo3O12 was the catalytic active phase;an addition of Fe greatly enhanced the lattice oxygen release rate,O2 activation capacity and isotutene adsorption,and consequently catalytic activity and CO2 selectivity;an addition of Co resulted in the formation of CoMoO4 with a higher lattice oxygen release rate,which,however,did not form lattice oxygen migration route with α-Bi2Mo3O12 and consequently did not influence the catalytic performance;upon a co-addition of Fe and Co,Fe was preferentially doped into CoMoO4 to enhance the lattice oxygen release rate,and formed the FexCo1-xMoO4-Fe-α-Bi2Mo3O12 interfacial structure to open up the lattice oxygen migration path from FexCo1-xMoO4 to α-Bi2Mo3O12,which appropriately enhanced the lattice oxygen supply rate of α-Bi2Mo3O12,togenther with the enhanced isobutene adsorption,promoting the partial oxidation of isobutene to MAL and consequently the selectivity and production rate of MAL.(3)Photothermal catalytic selective oxidation of isobutane to MAA:Effects of photo radiation on the catalytic selective oxidation of isotutane to MAA over(Cs2.20Cu0.260V0.382)xPMo12O40 heteropolyacid catalysts was explored.The preliminary results demonstrated that an introduction of photo radiation increased both isobutane conversion and MAA selectivity for the heteropolyacid(Cs2.2Cu0.26V0.382)xPMo12O40 catalyzed selective oxidation of isotutane reaction.