Niobium- and tantalum-containing mesoporous molecular sieves MCM-41 have been
synthesized, and applied as a catalyst for vapor phase Beckmann rearrangement of cyclohexanone
oxime to ε-caprolactam. NbMCM-41 catalyst exhibited high catalytic performance in the vapor
phase Beckmann rearrangement of cyclohexanone oxime. The oxime conversions were almost
100% and the lactam selectivities were around 80%. The lactam selectivities of NbMCM-41
catalyst were higher than those of AlMCM-41 catalyst. However, TaMCM-41 catalyst exhibited
lower catalytic performance than AlMCM-41 catalyst, and it was fast deactivated with time. These
results may be due to the acidity difference among the catalysts. The results from NH3-TPD showed
that NbMCM-41 catalyst possessed weak and medium acid sites, while TaMCM-41 catalyst
possessed only very weak acid sites. AlMCM-41 catalyst also exhibited only weak acid sites.