| As an important industrial raw material,ethylene glycol(EG)is widely used in chemical production,polyester and automobile antifreeze.At present,the general route of EG synthesis is the oil route.Due to the special energy distribution in China,it is of great significance to develop a oil-free route to produce EG.The technology of synthesizing DMO from syngas by C1 route has become feasible,but the Cu/SiO2 catalytic system for the DMO hydrogenation to EG still can not meet the needs of industrializa.tion.For this reason,a large number of studies have been carried out by the researchers.It is found that the catalyst carrier,the preparation method and the doping can improve the activity and stability of the catalyst.There is still much space for finding suitable catalyst additive.Fullerene,as the third isomorphs of carbon,is a new type of carbon material with unique properties.C60 has a suitable HOMO-LUMO,which can reversibly obtain electrons and release them.C60 has important applications in photo[P]taic devices and catalysis.At present,the study of C60 as a catalyst or catalytic additive is mainly concentrated in the fields of photocatalysis.There are few applications in the heterogeneous catalytic system for industrial use,so there is still plenty of space for the potential of the"electronic storage" as acatalytic additive.Mass spectrometry is an effective method for detecting reaction intermediates.By on-line and real-time monitoring of the catalytic reaction,the molecular weight and structural information of the intermediate can be obtained.It plays an important role in understanding the mechanism of the catalytic reaction.Electrospray ionization technology allows us to detect intermediates in liquid phase,while the detection of intermediates in gas phase reactions has not yet been reported.Based on the above research,we have carried out the following works:(1)We studied the electrochemical behavior of the reduced Cu/SiO2 and the C60-Cu/SiO2 catalyst modified with C60.Through the cyclic[P]tammetry(CV)under the anhydrous and anaerobic condition,we found the two electron transfer between C60 and Cu in the way of C60 +at the i Cu0? C60-+ Cu+ and Cu2+ + C60-?Cu+ + C60.C60 can get the electron from Cu and then release it back.In consideration of the synergy effect of Cu0-Cu+ in DMO hydrogenation,we think th nteraction between C60 and Cu can stabilize the Cu+ species in the system,and then improve the catalytic activity of the catalyst.(2)The interaction between Cu24O24Si8R8 and C60 was also studied by cyclic[P]tammetry,too.And the electron transfer process similar to that of the C60-Cu/SiO2 catalyst system was found.Combined with the calculation of HOMO-LUMO orbital energy levels,we confirmed the theoretical possibility of the such interaction.(3)The gas phase hydrogenation of DMO to EG under the atmospheric pressure was detected by online ESI-MS.It was found that the gas phase reaction could be detected in the presence of methanol steam in the ESI ionization source.By comparing the mass spectra of on-line and off-line detection,we found that the two signal peaks with molecular weights of 115 and 143 may be the intermediates of the catalytic reaction.By MS-MS characterization,we think that the molecular weight 143 is 2-hydroxyl-2-methoxy methyl acetate,which is in line with the intermediate A of the hydrogenation mechanism of DMO non dissociated adsorption. |
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