乙撑胺改性纯硅分子筛用于环己酮肟气相重排制已内酰胺

Ethylenediamine-modified pure silicalite molecular sieves applied in preparation of caprolactam via cyclohexanone oxime gas-phase rearrangement

通过环己酮肟(CHO)气相Beckmann重排工艺制备己内酰胺(CPL)是一条绿色环保的生产工艺,但是气相Beckmann重排催化剂的性能始终制约着该工艺的工业化应用。为了强化气相Beckmann重排催化剂的性能,利用分子尺寸不同的乙撑胺对纯硅分子筛进行了改性。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和N_(2)吸/脱附测试等方法对改性纯硅分子筛进行了表征,同时进行了CHO气相Beckmann重排的催化剂的催化性能评价。结果表明,乙撑胺改性的纯硅分子筛保持了原有的MFI型拓扑结构,Brunner-Emmet-Teller(BET)比表面积减小至354.1 m^(2)/g,CPL选择性增大至97.00%。对反应温度、CHO重时空速和质量分数对CHO气相Beckmann气相重排的影响进行了考察,优化得到的最佳反应工艺为:反应温度370℃,CHO重时空速1.0 h^(-1),CHO质量分数30%。在最佳工艺条件下,S-1-B催化剂的CHO转化率≥99.90%,CPL选择性≥97.00%,催化剂单程运行寿命达1200 h且再生性能稳定,具有良好的工业应用前景。

The preparation of caprolactam(CPL)by cyclohexanone oxime(CHO)gas-phase Beckmann rearrangement is a green and environmentally friendly production process,but the performance of gas-phase rearrangement catalysts has always restricted the industrial application of this process.In order to enhance the reaction performance of gas-phase Beckmann rearrangement,ethyleneamine with different molecular sizes were used to modify pure silicalite molecular sieves.Characterization of the modified pure silicalite molecular sieves was carried out by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD)and N_(2) adsorption/desorption tests,and the catalytic performance of the catalysts for CHO gas-phase Beckmann rearrangement was evaluated.The results indicate that the pure silicalite molecular sieves maintain their original MFI topology after ethyleneamine-modification,and the Brunner-Emmet-Teller(BET)specific surface area decreases to 354.1 m^(2)/g,and the CPL selectivity increases to 97.00%.The effects of reaction temperature,weight hourly space velocity and mass fraction of CHO on gas-phase Beckmann rearrangement were investigated.The optimal reaction processes are as follows:reaction temperature 370℃,weight hourly space velocity of CHO 1.0 h^(-1) and mass fraction of CHO 30%.Under the optimal reaction processes,the CHO conversion rate of S-1-B catalysts is≥99.90%,and the CPL selectivity of S-1-B catalyst is≥97.00%.The S-1-B catalyst has single-pass life of 1200 hours and stable regeneration performance,which has good industrial application prospect.