环己酮肟气相重排制备己内酰胺工艺

报道了一种具有MFI结构的高硅亚微米级分子筛MS1,该分子筛制备工艺简便、成本低、环境友好。研究了MS1分子筛催化环己酮肟气相Beckmann重排制备己内酰胺的催化效果,考察了汽化温度、反应温度、环己酮肟浓度及质量空速（WHSV）等反应条件对环己酮肟气相Beckmann重排反应的影响;在优化的反应条件下环己酮肟转化率≥99.5%,己内酰胺选择性达95%,且催化剂稳定性较好;结果表明,MS1分子筛催化剂具有良好的工业化应用前景。     

Vapor-phase beckmann rearrangement over alumina-supported boria catalyst prepared by vapor decomposition method

An alumina-supported boria (B₂O₃ content 25 wt%) prepared by vapor decomposition technique using ethyl borate in the presence of oxygen under atmospheric pressure exhibited high catalytic efficiency for the vapor-phase Beckmann rearrangement of cyclohexanone oxime: oxime conversion 100%, ε-caprolactam selectivity 95–98 mol% at 300 °C. The vapor decomposition B₂O₃/Al₂O₃ excelled the counterpart obtained by means of the conventional impregnation method in the selectivity to the lactam. The results of microscopic observation and surface area measurement suggested that the high lactam selectivity of the vapor decomposition catalyst was probably due to uniform dispersion of B2O3 onto Al2O3 which was effected by a procedure of vapor decomposition.     

S-1催化环己酮肟气相Beckmann重排反应动力学

目前尼龙6生产中主要采用发烟硫酸催化环己酮肟液相Beckmann重排制己内酰胺,副产大量硫酸铵,而且存在设备腐蚀等问题。采用气相重排法可以克服上述缺点。本工作在以前得到的优化反应条件下,根据实验并采用催化剂失活的Wojciechowski模型获得了S-1催化环己酮肟气相Beckmann重排制己内酰胺反应动力学方程及参数。该模型将催化剂的活性与在线反应时间相关联,进而可以计算任何在线反应时间时催化剂的失活速率,或者根据要求的转化率最低允许值计算催化剂能在线反应的时间。     

Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime Over Rare Earth Pyrophosphates

A new application of rare earth pyrophosphates in vapor phase Beckmann rearrangement of cyclohexanone oxime was investigated. The rare earth phosphates were characterized by means of XRD, FT-IR, NH₃-TPD and water contact angle measurement. It was found that the weak surface acidity and appropriate surface hydrophobicity should be two key factors in the excellent performance of these catalysts.     

Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime over Different Ferrierite Zeolite Catalysts

Ferrierite zeolite catalysts prepared using different procedures have been tested for their activity for vapor phase Beckmann rearrangement of cyclohexanone oxime to -caprolactam. We report here the results of a study seeking the influence of temperature, nitrogen feed rate, oxime concentration and solvents on the catalyst performance. At low concentration of oxime (2.5 wt%), using acetonitrile as solvent the maximum in the conversion of oxime and selectivity to -caprolactam has been obtained. The presence of weak, medium and strong acid sites as indicated by temperature-programmed desorption of NH₃ corroborates well with the catalytic activities of various ferrierites shown here. Solvent polarity is found to significantly affect the conversion of cyclohexanone oxime.     

Crosslinked TS-1 as stable catalyst for the Beckmann rearrangement of cyclohexanone oxime

Crosslinked TS-1 zeolite materials have been studied in the gas phase Beckmann rearrangement reaction of cyclohexanone oxime to ε-caprolactam. Crosslinking of the zeolite particles resulted in the formation of an additional mesoporosity leading to increased activity in the Beckmann rearrangement reaction. The increased activity can be correlated with the newly created mesopore surface. Possibly more important, together with increased catalytic activity of the materials, the deactivation behavior of the catalysts is very significantly improved.     

Acidity Control and Catalysis of Pentasil Zeolites

Acidities of pentasil zeolites were measured and correlated with aluminum content using the following methods: (1) Acid-base indicator method, (2) NH₃-TPD spectra, (3) GC pulse adsorption of pyridine and 4-methylquinoline, and (4) FTIR spectroscopy of adsorbed pyridine.

By controlling the acidity of pentasil zeolites, we have succeeded in obtaining high catalytic performance both in paraselective dealkylation of cymenes and in vapor-phase Beckmann rearrangement of cyclohexanone oxime to ?-caprolactam. In the dealkylation, moderate acidity of Li-ZSM-5 was the key to avoid side reactions while keeping a high conversion of cymenes. In the Beckmann rearrangement, neutrality and crystallinity of the pentasil zeolite were keys to obtain a high lactam selectivity, and a high lactam selectivity of 95% was attained by the surface treatment with chlorotrimethylsilane. The active sites were elucidated to be neutral silanols on the external surface of zeolite.     

Vapor phase reaction of cyclohexanone oxime over boria modified HSZM-5 zeolites

The vapor phase Beckmann rearrangement of cyclohexanone oxime has been carried out over zeolites and boria modified HZSM-5 zeolites to elucidate the effects of acidity and acid strength distribution on the conversion and ε-caprolactam selectivity. Although ε-caprolactam selectivity was increased with the SiO₂Al²O³ ratio in a HZSM-5 zeolite, the highest selectivity in the study was accomplished over a boria modified HZSM-5. The selectivity was dependent on the ratio of weak acid sites to strong acid sites. The boria played an important role in controlling the acid strength distribution of the zeolites. It was found that the production of a polymer over strong acid sites caused a decrease in ε-caprolactam selectivity during the reaction.     

A modified mixed-acid catalytic system for Beckmann rearrangement of cyclohexanone oxime

ε-Caprolactam (CPL) is mainly produced through Beckmann rearrangement of cyclohexanone oxime catalyzed by oleum in industry nowadays, which suffers the problems like high viscosity and bad mixing, leading to multiple by-products. To this end, a modified mixed-acid catalytic system containing oleum and trifluoroacetic acid (TFA) was proposed to intensify the reaction. The viscosity of the reaction system was studied and the effects of several experimental parameters on the reaction rate and selectivity were also investigated, including oleum/oxime ratio, TFA/oleum ratio, temperature, and SO₃ concentration. Extremely high selectivity (>99.6%) was obtained under all conditions, revealing that by-products in industrial process were mainly formed owing to the insufficient mixing and poor mass and heat transfer rather than experimental parameters. A preliminary mathematical model considering the effect of CPL was developed to predict the reaction rate. These results are helpful to improve the industrial process of CPL production.     

Modification of a heterogeneous catalyst: Sulfonated graphene oxide coated by SiO2 as an efficient catalyst for Beckmann rearrangement

In this work and in continuation of our strategy for improving the performance of heterogeneous catalysts, the SiO₂@GO-OSO₃H catalyst was applied as a very efficient solid acid catalyst for the Beckmann rearrangement. This catalyst effectively catalyzed the liquid-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam in high yield under very mild conditions. The improvement of GO-OSO₃H catalyst in regard to its separation from reaction mixture is achieved by coating it with a mesoporous SiO₂ layer. The influence of the operating parameters on the performance of the catalyst namely solvent, temperature, amount of catalyst, and time was studied.     

P2O5液相催化环己酮肟重排制己内酰胺

研究了以环己酮肟、五氧化二磷(P_2O_5)、二甲基甲酰胺(DMF)组成的反应体系进行Beckmann重排制备己内酰胺工艺,考察了不同溶剂、催化剂用量、温度、浓度及水分含量对重排反应的影响。结果表明,由DMF、P_2O_5、少量水组成的反应体系,当P_2O_5与环己酮肟质量比为(1.0：4.5)～(1.0：5.6),温度为160～170℃,停留时间为0.75～1.00 h时,实现环己酮肟Beckmann重排制己内酰胺,转化率达99.5％以上,选择性达94.5％     

离子液体系中催化环己酮肟重排反应的研究

发现由室温离子液体正丁基吡啶氟硼酸盐,异丁基吡啶氟硼酸盐,正戊基吡啶氟硼酸盐,正辛基吡啶氟硼酸盐等和含磷化合物组成的催化体系,可以高效地实现对环己酮肟重排制己内酰胺的反应,此方法具有不再用有机溶剂,反应副产物少等特点,并考察了不同的离子液、不同磷化合物催化剂、离子液的用量、反应温度、反应时间等对反应的转化率和产物分布的影响,以寻找出一最适宜的反应条件。     

Theoretical study on vapour phase Beckmann rearrangement of cyclohexanone oxime over a high silica MFI zeolite

We have studied an activation mechanism of cyclohexanone oxime in a cavity of high silica MFI zeolite by using PIO analysis proposed by Fujimoto et al. DFT calculation reveals that the bond length of N–OH becomes longer when water coordinates on oxygen of oxime. The PIO clearly shows out-of-phase interaction between N and O. This out-of-phase interaction is also observed in the PIO of oxime/MFI zeolite cluster model and weakens the N---O bond. Hydrogen bond of Si–OH of nest silanols to oxime is a trigger of vapour phase Beckmann rearrangement.     

Beckmann rearrangement of cyclohexanone oxime in a microchemical system: The role of SO3 and product inhibition

The mechanism of Beckmann rearrangement of cyclohexanone oxime in oleum is investigated with a multiphase microchemical system, which is designed to give good control of the reaction temperature and residence time. The influences of SO₃ and caprolactam concentrations in oleum on the conversion are investigated. The results indicate that SO₃ acts as the catalyst and caprolactam plays a product inhibition role. Based on these results and previous mechanism analysis, an equilibrium relation between protonated caprolactam and caprolactam hydrogen sulfate is proposed and the equilibrium constants at 70, 80, and 90^°C are gained. According to the equilibrium, the lowest acid/oxime molar‐ratio of 0.5 for sufficient conversion (>99%) at 100^°C has been provided. This quantitative mechanism analysis gives the reason for the negative influences of higher caprolactam concentration and lower temperature on the reaction conversion, which is very useful for the optimization and reliable design of Beckmann rearrangement processes. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3156–3160, 2012     

环己酮肟气相Beckmann 重排制己内酰胺催化剂研究进展

环己酮肟Beckmann 重排制己内酰胺是重要的工业过程。本文较为详细地评述了用于环己酮肟气相Beckmann 重排反应的固体酸催化剂, 主要有氧化物、金属磷酸盐和分子筛等     

固体酸催化环己酮肟Beckmann重排制己内酰胺研究进展

环己酮肟 Beckmann 重排制己内酰胺是重要的工业过程.本文介绍了用以代替浓硫酸催化该反应的固体酸催化剂及其影响因素以及催化剂的失活与再生等.     

Sulfonic acid functionalised SBA-15 as catalysts for Beckmann rearrangement and esterification reaction

Hybrid inorganic–organic solid acid materials SBA-15–Ph–SO₃H were synthesized by the directly co-condensation method under the acid medium. The resulting materials perform well both in the liquid phase Beckmann rearrangement (The yield is 32.3%) and esterification reaction (The yield is 95.5%). And more, the catalysts show the different catalytic performance in these two reactions.     

Enhancement effect of organic additives on liquid-phase production of ε-caprolactam

The effect of various organic additives on the catalytic performance of zeolites and Al-containing MCM-41 in the liquid-phase Beckmann rearrangement of cyclohexanone oxime was investigated at 130 °C using benzonitrile as solvent. Over USY zeolite with a large amount of extraframework aluminum (EFAL), the lactam yield was dramatically improved, up to 82%, by adding ethanol, dimethyl sulfoxide, ammonia, diethylamine, or pyridine to the oxime solution. It is due to a selective adsorption of these additives on the detrimental hydrolysis sites as suggested by FTIR results. On the other hand, the additives enhanced both the oxime conversion and the lactam yield through a promotion of the desorption of lactam product from acid sites when beta zeolite and Al-MCM-41 with relatively low EFAL content were used as catalysts.     

Acidity Control and Catalysis of Pentasil Zeolites

Acidities of pentasil zeolites were measured and correlated with aluminum content using the following methods: (1) Acid-base indicator method, (2) NH₃-TPD spectra, (3) GC pulse adsorption of pyridine and 4-methylquinoline, and (4) FTIR spectroscopy of adsorbed pyridine.

By controlling the acidity of pentasil zeolites, we have succeeded in obtaining high catalytic performance both in paraselective dealkylation of cymenes and in vapor-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam. In the dealkylation, moderate acidity of Li-ZSM-5 was the key to avoid side reactions while keeping a high conversion of cymenes. In the Beckmann rearrangement, neutrality and crystallinity of the pentasil zeolite were keys to obtain a high lactam selectivity, and a high lactam selectivity of 95% was attained by the surface treatment with chlorotrimethylsilane. The active sites were elucidated to be neutral silanols on the external surface of zeolite.     

Effects of acid strength and micro pore size on -caprolactam selectivity and catalyst deactivation in vapor phase Beckmann rearrangement over acid solid catalysts

The vapor phase Beckmann rearrangement of cyclohexanone oxime (CHO) over solid acid catalysts including zeolites was carried out to elucidate the effects of the acid strength and the micropore size of the catalysts on the selectivity of -caprolactam (CL) and the catalyst deactivation rate. It was found that the catalyst deactivation rate was strongly dependent on the acid strength of the acid catalysts. The improvement of catalyst life was achieved by using MFI-type metallosilicates having weak acid sites. The CL selectivity decreased over the acid catalysts with micropores larger than those of the MFI zeolites. Furthermore, using methanol and carbon dioxide as the diluent solvent and diluent gas improved CL selectivity and catalyst life, respectively.