Mesoporous silicon sulfonic acid as a highly efficient and stable catalyst for the selective hydroamination of cyclohexene with cyclohexylamine to dicyclohexylamine in the vapor phase

In this work,a new mesoporous silicon sulfonic acid catalyst derived from silicic acid has been successfully prepared by the chemical bonding method.The physicochemical properties of mesoporous silicon sulfonic acid catalysts have been systematically characterized using various techniques.The results demonstrate that sulfonic acid groups have been grafted on silicic acid by forming a new chemical bond(Si-O-S).The mesoporous silicon sulfonic acid exhibits excellent catalytic performance and stability in the vapor phase hydroamination reaction of cyclohexene with cyclohexylamine.Cyclohexene conversion of 61% and 97% selectivity to dicyclohexylamine was maintained after running the reaction for over 350 h at 280℃.The developed mesoporous silicon sulfonic acid catalyst shows advantages of low cost,superior acid site accessibility,and long term reactivity stability.Moreover,a possible catalytic hydroamination reaction mechanism over silicon sulfonic acid was suggested.It has been demonstrated that the sulfonic acid groups of the catalyst play an important role in the hydroamination.The present work provides a simple,efficient,and environmentally friendly method for the hydroamination of cyclohexene to valuable dicyclohexylamine,which also shows important industrial application prospects.

Catalytic Hydrogenation of Aromatic Compounds in the Liquid Phase

Peculiarities of a liquid phase hydrogenation, namely lower diffusivity of components influencing the reaction rate and deactivation of catalysts by leaching, are discussed. A focus is on hydrogenation of aromatic compounds, whereas the following processes are evaluated： （l） partial hydrogenation of benzene to cyclohexene; （2） hydrogenation of aniline; （3） hydrogenation of diphenylamine; （4） preparation of aniline from nitrobenzene; （5） hydrogenation of chloronitrobenzenes; （6） hydrogenation of 4-nitrosodiphenylamine and 4-nitrodiphenylamine mixture. Processes （1） and （6） are typically carried out in the water-oil system. Generally, this type of system allows reaching a higher selectivity to desired products. In the case of hydrogenation of 4-nitrosodiphenylamine and 4-nitrodiphenylamine mixture, the water phase extracts a water soluble catalyst; which is recycled and used for condensation of aniline and nitrobenzene. Problems of reaction kinetics, as well as catalysts deactivation are here discussed.