Improved catalytic activity and selectivity of (A1+B)-MCM-41 mesoporous materials treated with ammonium fluoride in the vapor-phase Beckmann rearrangement of cyclohexanone oxime

摘要

Aluminum-boron-silicate MCM-41 mesoporous molecular sieves with Al/B ratio in the range 2-0.5 were characterized by XRD,N_2 adsorption,MAS NMR,and DRIFT,and their acid properties were determined by pyridine (Py) adsorption.(A1+B)-MCM-41 samples were prepared by two procedures: (i) direct synthesis by using TEOS,H_3BO_3 and Cl_3Al6H_2O as silica,boron and aluminum sources,respectively and (ii) the as-synthesized samples obtained in (i) were suspended in 300 mL of NH_4F 0.1 M for 34 h.The aluminum-boron-silicate MCM-41 materials treated with NH_4F improved both the selectivity to epsilon-caprolactam (related mainly to boron content) and the life span (related mainly to NH_4F treatment).