MnO_x/TS-1 And Co/Mo Oxides Catalyzed Oxidation Of Ethylbenzene And Cyclohexene With Molecular Oxygen

TS-1 was synthesized by hydrothermal method has good stability.However,the limitation of mesoporous pore size in TS-1 and hydrogenperoxide as a more expensive oxidant greatly limit its application in industry.In this work,the pore size of TS-1 was broadened to improve its catalytic performance,modifying the TS-1 to obtain the HTS-1was necessary.Then used transition metal doped it,got the MnO_x/TS-1 catalyst.At last,tested the catalytic performance of prepared catalysts which through the catalytic oxidation reaction of ethylbenzene.The reaction conditions were optimized and the stability of the catalyst was investigated.Tetrahedral Ti⁴⁺and MnO_x species homogeneous were dispersed on the hollow TS-1 surface and strong favourable synergic interactions between them were occurred,which supported by the comprehensive analysis of XRD,N₂ physical adsorption,TEM,H₂-TPR,FT-IR,UV-vis,XPS and Raman spectroscopy.The virtue of such synergic effects was reflected in a catalytic efficiency enhancement of valuable ketone and alcohol products(TOF=137 h^-1).MnO_x/TS-1 catalyst was showed about 2.2 times higher efficiency compared to MnO_x/silicate-1 references.Furthermore,the Mn species content and calcination temperature of the MnO_x/TS-1 catalyst were presented significant effects of lower-nuclearity Mn³⁺on the structural,chemical,and catalytic properties.Excessive calcination temperature leaded to the sintering of the catalyst surface and the collapse of the structure.When the temperature was low,the crystal development was not complete.The dispersed manganese was increased with the increase of the surface coverage,which prevented the reactant and the subsequent intermediate contacted with all catalytically active sites.Based on the theoretical calculations,the reaction mechanism was proposed where the cleavage of the longer methylene C–H bond?1.0935??of ethylbenzene and O–O bond?1.5267??of alkyl hydroperoxide over the O–Ti–O–Mn sites was a key step to yield radical continuously for recycle.The Co/Mo bimetallic oxide has been exploited in the aerobic epoxidation of alkenes containing labile allylic hydrogen atoms?cyclohexene,cycloheptene,1–octene?using alkylbenzene?cumene,ethylbenezene?as a solvent.Cooperativity between Co?II?sites and Mo?VI?sites consisting of Co–O–Mo bonds on oxide surfaces was investigated for controlling preferred epoxidation catalysis via tandem oxygen transfer.Various characterization techniques like XRD diffraction,N₂ physisorption,TEM,H₂-TPR and Raman,XPS,Infrared,and UV-visible spectroscopies were employed to reveal the relationship between structure of active species and catalytic performance.In this unique tandem catalytic process,Co?II?sites effectively mediated the first step of the overall oxidation cycle yielding a alkyl peroxy radical by oxygen activation[Co?II?to Co?III?-O^2-to alkyl radical and finally to an alkyl peroxy radical].On the other hand,Mo?VI?sites were shown to be the excellent catalytic sites for the subsequent epoxidation step by the transfer of oxygen atom of the alkyl peroxy radical to alkene.Hence,a 78%epoxidation selectivity with 40%alkene conversion was accomplished through the required combination of Co?II?and Mo?VI??2:1?,allowing to tune epoxidation efficiency toward higher driving forces?relative to oxygenation of allylic hydrogen atom?.This remarkably different catalytic performances between Co?II?and Mo?VI?can be attributed to the stronger overall polarization ability of Mo?VI?toward?*O–O orbital of the O–O unit derived from its d-type orbitals,which helped the donor-acceptor interactions with the double bond.