Hiroshi Ichihashi

The development of new heterogeneous catalytic processes for the production of ε-caprolactam

Abstract Two catalytic methods emerging newly for the production of e-caprolactam are reviewed: the ammoximation, and the vapor phase Beckmann rearrangement. These processes do not produce any ammonium sulfate as a by-product. The key for the processes are the catalysts used. The TS-1 zeolite comprising Ti and Si oxides with the structure of MFI is applied as an effective catalyst in the ammoximation reaction. This work reviews its catalysis and the features of the reaction. Although many solid acid catalysts have been tested for the Beckmann rearrangement, recently high silica MFI zeolites without so-called acidic sites are developed for the reaction. A brief history of the catalyst development on the rearrangement is presented, and the catalysis of high silica MFI zeolite is reviewed.

Some aspects of the vapor phase Beckmann rearrangement for the production of ε-caprolactam over high silica MFI zeolites

A high silica MFI zeolite catalyst has been developed for the vapor phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam. Methanol fed into the reactor with the oxime improves the yield of caprolactam. Methanol is not converted to dimethylether during the reaction. Moreover, when ammonia is fed to the catalyst with cyclohexanone oxime and methanol, the selectivity remains at a high level, without affecting the conversion. Hence, we conclude that the active sites of high silica MFI are extremely weak acid sites that cannot be detected by ammonia TPD measurement. A fluidized bed reaction system has been developed for the manufacturing process of caprolactam. High quality product is obtained with more than 95% yield.

The Catalysis of Vapor-Phase Beckmann Rearrangement for the Production of ε-Caprolactam

Recently, Sumitomo Chemical Co., Ltd. developed the vapor-phase Beckmann rearrangement process for the production of ε-caprolactam. In the process, cyclohexanone oxime is rearranged into ε-caprolactam using a zeolite as a catalyst instead of sulfuric acid. EniChem in Italy developed the ammoximation process that involves the direct production of cyclohexanone oxime without producing any ammonium sulfate. Sumitomo Chemical Co., Ltd. has commercialized the combined process of vapor-phase Beckmann rearrangement and ammoximation in 2003.In this paper, the authors focus on some aspects of the vapor-phase Beckmann rearrangement catalysis. A solid catalyst that is mainly composed of a high-silica MFI zeolite (Silicalite-1) has been developed for the vapor-phase Beckmann rearrangement. This catalyst does not possess acidity that can be detected by ammonia TPD. Methanol fed into the reactor with cyclohexanone oxime improves the yield of caprolactam. Methanol reacts with terminal silanols on the zeolite surface and converts them to methoxyl groups. The modification of the catalyst by methanol has an important role for the Beckmann rearrangement reaction.Nest silanols located just inside the pore mouth of the MFI zeolite are supposed to be the active sites of the catalyst. We propose that the coordination between the NOH group of cyclohexanone oxime molecule and the nest silanols through hydrogen bonding is responsible for the reaction. The reaction mechanism of Beckmann rearrangement under vapor-phase conditions is the same as in the liquid phase, namely, the alkyl group in anti-position against the hydroxyl group of the oxime migrates to the nitrogen atoms position.

1.7 The Role of Alcohols on Lactam Selectivity in the Vapor-Phase Beckmann Rearrangement Reaction

Abstract For the vapor-phase Beckmann rearrangement reaction of cyclohexanone oxime over high-silicious pentasil zeolites, the selectivity to e-caprolactam increased when methanol was supplied with cyclohexanone oxime into the reaction system. FT-IR measurements showed that the neutral silanol groups of the zeolite were methylated by the alcohol. This indicates that the neutral silanol is not the active site for producing e-caprolactam.

10 Vapor phase beckmann rearrangement over a high silica MFI zeolite

Abstract A catalyst that is mainly composed of a high silica MFI zeolite (Silicalite-1) has been developed for the vapor phase Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam. This catalyst does not possess acidity that can be detected by ammonia TPD. Methanol fed into the reactor with the oxime improves the yield of caprolactam. Methanol reacts with terminal silanols on the zeolite surface at an elevated temperature and converts them to methoxyl groups. The modification of the catalyst by methanol plays an important role in the Beckmann rearrangement reaction. We consider that the reaction mechanism of Beckmann rearrangement under vapor phase conditions is the same as in the liquid phase, namely the alkyl group in the anti position against the hydroxyl group of the oxime migrates to the N atom position. Nest silanols located just inside the pore mouth of the MFI zeolite are assumed to be the active sites of the catalyst. We propose that the NOH group of cyclohexanone oxime molecule adsorbed on the zeolite surface is coordinated by OH groups of the nest silanols with hydrogen bonding. This coordination seems to play an important role in the reaction.

Vapor Phase Catalytic Oxidation of Isobutene to Methacrylic Acid

A number of aspects of the two stage vapor phase catalytic oxidation of isobutene to methacrylic acid as related to the design of the industrial catalysts involved are discussed in particular in comparison with the counter parts of the case of propylene to acrylic acid. An overall yield exceeding seventy percent has been attained in the laboratory and that only a few percent less in the pilot.