Research On The Reaction Of Methanol/syngas As Methylation Reagen

Methylation is a class of reaction that can achieve C-C bond or C-N bond coupling,which can be used to synthesize a variety of organic compounds.Most of the traditional methylation methods are based on the methylation of dimethyl sulfate,dimethyl carbonate,etc.Most of the process is based on homogeneous catalysis,the separation and recovery of homogeneous catalyst is still a problem.Therefore,the development of heterogeneous catalysts with high activity and low cost has great significance and broad prospects.In this paper,based on the application of different methylation reagents in the reaction,two different types of catalysts were prepared for the methylation reactions with methanol and syngas as the methylation reagents,which provided new methods and ideas for the design of methylation catalysts and construction of reactions.The specific research contents are as follows:1.A series of SiO₂-supported carbonate catalysts were prepared by impregnation method to catalyze the methylation of methyl cyanoacetate with methanol.A series of screenings were carried out on the type and loading of catalysts and the conditions of the reaction.Among them,the 10%K₂CO₃/Si O₂catalyst has the best reaction activity,and the conversion of methyl cyanoacetate and the selectivity of 2-cyanopropionic acid methyl ester can reach 57%and 45%,respectively,at the liquid hourly space velocity（LHSV）of 0.3 m L·g^-1·h^-1,230℃,1 MPa.After 39 h of reaction,the catalyst began to deactivate,then the catalyst was regenerated to restore the activity.The structure and morphology of the catalyst were studied by XRD,XPS,NH₃-TPD,CO₂-TPD,TG,etc.The reaction mechanism of catalysis was discussed.2.A series of CuZnCrO_x compound metal oxide catalysts of different proportions were prepared by co-precipitation method.The obtained catalysts were used to catalyze syngas to replace methanol as a new methylation reagent for N-methylation of aniline.Different Cu-Zn mass ratios have significant effects on the activity of the reaction.Among them,Cu₃Zn₆Cr₁O_xhas excellent catalytic activity for the methylation of aniline with syngas.Under the reaction conditions of liquid hourly space velocity（LHSV）of0.55 m L·g^-1·h^-1,the gas hourly space velocity（GHSV）of 3000 m L·g^-1·h^-1,CO/H₂=1:1,220℃,3 MPa,the highly selective conversion of aniline to the target product N-methylaniline（95%selectivity）was achieved with 92%conversion of aniline.The catalyst show an excellent stability after 100 h stability test.The catalyst integrates Cu Zn-based catalyst,which can efficiently convert syngas to methanol and realize N-methylation of aniline on Cu-based catalyst.In situ reaction of CO hydrogenation and N-methylation of aniline was realized under the same condition.In the N-methylation reaction of aniline,the conversion of aniline with syngas as methylation reagent is more obvious than that of methanol as methylation reagent under the same reaction condition.The structure and morphology of the catalyst were studied by XRD,XPS,chemisorbent,etc.The construction of this system provides a new idea and experimental support for N-methylation and C-N bond coupling of aniline.