Bismuth supported SBA-15 catalyst for vapour phase Beckmann rearrangement reaction of cyclohexanone oxime to ɛ-caprolactam

•Low cost bismuth metal precursor is used for Beckmann rearrangement reaction.•Non-polar solvent is found beneficial than polar solvent.•Surface silanol in the vicinity of Lewis acid centre is suggested for protonation during reaction.

Development of environmental benign as well as low cost metal precursor based catalyst is a challenge for chemical industry. In this work we report Bi promoted SBA-15 catalyst for vapour phase Beckmann rearrangement reaction of cyclohexanone oxime. The three different Bi loaded SBA-15 catalysts are prepared and characterized by BET surface area and porosity measurement, small angle X-ray scattering, wide angle X-ray diffraction, field emission scanning electron microscope, high resolution transmission electron microscope, ultraviolet–visible spectroscope, Fourier transform infrared spectroscopy and temperature programmed desorption techniques. Further, catalytic activity is optimized by changing reaction temperature, pre-treatment temperature and pre-treatment time so that 100% cyclohexanone oxime conversion and 100% ɛ-caprolactam selectivity has been achieved. Role of solvent, silylation and time on stream has also been examined. The TPD profiles of all three bismuth loaded samples are mainly characterized by weak acidic sites or surface silanol groups. The FTIR profile shows hydroxyl rich surface in the vicinity of bismuth at Bi-SBA-15 (Bi/Si = 1/100). Based on catalyst characterization and activity data correlation, it can be suggested that protonation at oxime oxygen can be triggered by surface silanol in the vicinity of a Lewis acid centre bismuth. The high space-time-yield of caprolactum was 114.3 mol gcat−1 h−1 was obtained.

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