Synthesis of porous catalysts for Beckmann rearrangement of oximes

摘要

It is generally known that vapor phase oximes rearrangement on solid catalysts is strongly dependent on the material acidic properties and porosity. Recent studies led to synthesize high performing catalysts with high silica content. In this paper we report the synthesis of several crystalline materials in order to understand the effect of the channels system and of the defective groups on the catalytic behaviour in Beckmann reaction. The MEL, MFI, MTW type zeolites were prepared and tested in the cyclohexanone-oxime conversion. Due to its unique channel system and to the presence of defective sites, the MFI and MEL type zeolites, in pure silica form (Sil-1 and Sil-2) and in boron form (B-MFI-(A), H_3BO_3/SiO_2=0.066 and B-MFI-(B), H_3BO_3/SiO_2=0.033) showed the best catalytic results. However silicalite-1 is still the most performing catalyst, the zig-zag channels structure has the same kind of acid sites (same desorption temperature) of three-dimensional straight channel silicalite-2, but an higher active sites distribution (Si-OH and Si-N groups). The introduction of boron atoms decreases the catalytic performances.