Mesoporous silicon sulfonic acid as a highly efficient and stable catalyst for the selective hydroamination of cyclohexe
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RESEARCH ARTICLE
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 Jingbin Wen1, Kuiyi You (✉)1,2, Minjuan Chen1, Jian Jian3, Fangfang Zhao1, Pingle Liu1,2, Qiuhong Ai1,2, He’an Luo (✉)1,2
1 School of Chemical Engineering, Xiangtan University, Xiangtan 411105, China 2 National & Local United Engineering Research Center for Chemical Process Simulation and Intensification, Xiangtan University, Xiangtan 411105, China 3 School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
© Higher Education Press 2020
Abstract 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 °C. 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. Keywords mesoporous silicon sulfonic acid, catalytic hydroamination, cyclohexene, dicyclohexylamine, vapor phase Received March 29, 2020; accepted June 15, 2020 E-mails: [email protected] (You K); [email protected] (Luo H)
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Introduction
Amines are important organic chemical materials and intermediates widely used in fine chemicals, pharmaceuticals, pesticides, and petrochemicals. For example, dicyclohexylamine (DCHA) is used as an excellent corrosion inhibitor in steam pipes and boilers [1,2], a vulcanization accelerator for synthetic rubber [3,4], and a useful commercial insecticide [5]. The preparation methods for DCHA mainly include catalytic hydrogenations of aniline over Ru, Pd, or Ru/Pd catalysts [6,7], nitrobenzene over Pd/C catalysts [8], cyclohexanone and aniline over Ru, Rh and/or Pd catalysts [9], nitrobenzene and phenol over metallic palladium catalysts [10], or cyclohexylamine and cyclohexanone over a specific catalyst [11] (Scheme 1). However, these processes have many disadvantages, such as expensive catalyst co
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