Design and preparation of highly efficient zeolite catalysts for gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam are attractive but still challenging.Herein,we show a one-pot synthesis of silica...Design and preparation of highly efficient zeolite catalysts for gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam are attractive but still challenging.Herein,we show a one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols.The key to this success is the use of urea in the synthetic system.Catalytic tests of cyclohexanone oxime gas-phase Beckmann rearrangement show that the silicalite-1 zeolite nanosheets with H-bonded silanols exhibit higher selectivity for caprolactam and longer reaction lifetime than those of the conventional silicalite-1 zeolite.Theoretical simulations reveal that the ammonium decomposed by urea is a critical additive for the formation of H-bond silanols.Obviously,one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols plus excellent catalytic performance in the Beckmann rearrangement offer a new opportunity for development of highly efficient zeolites for catalytic applications in the future.展开更多
The liquid phase Beckmann rearrangement of cyclohexanone oxime (CHO) using fuming sulfuric acid as a catalyst is a traditional method for preparing ε-caprolactam (CPL). This process has drawbacks, such as environment...The liquid phase Beckmann rearrangement of cyclohexanone oxime (CHO) using fuming sulfuric acid as a catalyst is a traditional method for preparing ε-caprolactam (CPL). This process has drawbacks, such as environmental pollution, corrosion of equipment, and low added value of by-product ammonium sulfate. This article designed and prepared a green silica gel-supported trifluoromethanesulfonic acid catalyst for the liquid-phase Beckmann rearrangement of CHO to prepare (CPL). The influencing factors of catalyst preparation and the optimal reaction conditions for Beckmann rearrangement were investigated. It was found that the optimal conditions for catalyst preparation were as follows: raw material silica gel:trifluoromethanesulfonic acid = 1:0.2 (mass ratio), room temperature, stirring time of 2.5 hours, and solvent of acetonitrile, silica gel mesh size is 100 - 200. The optimal reaction conditions for Beckmann rearrangement are CHO: catalyst = 1:2 (mass ratio), temperature of 130˚C, solvent of benzonitrile, volume of 30 mL/g CHO, and reaction time of 4 hours. Under the above conditions, the conversion of CHO is 90%, and the selectivity of CPL is 90%.展开更多
研究了氢氟酸后处理对silicalite-1催化环己酮肟气相Beckmann重排反应性能的影响.结果表明,经适当浓度的氢氟酸溶液处理后,催化剂的选择性和稳定性都明显改善.其中,silicalite-1原粉先经硝酸铵预处理后再进行氢氟酸后处理所得到的催化...研究了氢氟酸后处理对silicalite-1催化环己酮肟气相Beckmann重排反应性能的影响.结果表明,经适当浓度的氢氟酸溶液处理后,催化剂的选择性和稳定性都明显改善.其中,silicalite-1原粉先经硝酸铵预处理后再进行氢氟酸后处理所得到的催化剂催化性能最好,反应53 h后环己酮肟的转化率仍保持在96%左右,己内酰胺的选择性高达96.1%.XRD,FT-IR和29Si MAS NMR的结果表明,较高的具有氢键相互作用的硅羟基与孤立硅羟基的比例值对环己酮肟气相Beckmann重排反应有利,同时,silicalite-1表面硅原子的排布方式对该反应也有重要影响.展开更多
文摘Design and preparation of highly efficient zeolite catalysts for gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam are attractive but still challenging.Herein,we show a one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols.The key to this success is the use of urea in the synthetic system.Catalytic tests of cyclohexanone oxime gas-phase Beckmann rearrangement show that the silicalite-1 zeolite nanosheets with H-bonded silanols exhibit higher selectivity for caprolactam and longer reaction lifetime than those of the conventional silicalite-1 zeolite.Theoretical simulations reveal that the ammonium decomposed by urea is a critical additive for the formation of H-bond silanols.Obviously,one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols plus excellent catalytic performance in the Beckmann rearrangement offer a new opportunity for development of highly efficient zeolites for catalytic applications in the future.
文摘The liquid phase Beckmann rearrangement of cyclohexanone oxime (CHO) using fuming sulfuric acid as a catalyst is a traditional method for preparing ε-caprolactam (CPL). This process has drawbacks, such as environmental pollution, corrosion of equipment, and low added value of by-product ammonium sulfate. This article designed and prepared a green silica gel-supported trifluoromethanesulfonic acid catalyst for the liquid-phase Beckmann rearrangement of CHO to prepare (CPL). The influencing factors of catalyst preparation and the optimal reaction conditions for Beckmann rearrangement were investigated. It was found that the optimal conditions for catalyst preparation were as follows: raw material silica gel:trifluoromethanesulfonic acid = 1:0.2 (mass ratio), room temperature, stirring time of 2.5 hours, and solvent of acetonitrile, silica gel mesh size is 100 - 200. The optimal reaction conditions for Beckmann rearrangement are CHO: catalyst = 1:2 (mass ratio), temperature of 130˚C, solvent of benzonitrile, volume of 30 mL/g CHO, and reaction time of 4 hours. Under the above conditions, the conversion of CHO is 90%, and the selectivity of CPL is 90%.
文摘研究了氢氟酸后处理对silicalite-1催化环己酮肟气相Beckmann重排反应性能的影响.结果表明,经适当浓度的氢氟酸溶液处理后,催化剂的选择性和稳定性都明显改善.其中,silicalite-1原粉先经硝酸铵预处理后再进行氢氟酸后处理所得到的催化剂催化性能最好,反应53 h后环己酮肟的转化率仍保持在96%左右,己内酰胺的选择性高达96.1%.XRD,FT-IR和29Si MAS NMR的结果表明,较高的具有氢键相互作用的硅羟基与孤立硅羟基的比例值对环己酮肟气相Beckmann重排反应有利,同时,silicalite-1表面硅原子的排布方式对该反应也有重要影响.
