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High-silica ZSM-5 zeolites were synthesized by the addition of pentavalent ions, such as phosphorus and arsenic ions, to the mother gel for the zeolite preparation. The Beckmann rearrangement of cyclohexanone oxime in the vapor phase was carried out over the high-silica ZSM-5 zeolites or zeolites modified with noble metals to elucidate the effects of the diluent gas and diluent solvent on the e-caprolactam selectivity and catalyst deactivation. The catalyst lives of the zeolites modified with noble metals were much longer than that of the unmodified zeolite during the rearrangement using carbon dioxide and methanol as the diluent gas and diluent solvent, respectively. Furthermore, the life of the zeolites modified with noble metals was significantly improved by using a small amount of oxygen as the diluent gas. In this case, methanol was the most suitable diluent solvent for the improvement of catalyst life. The catalyst life decreased with increased cyclohexanone oxime concentration in methanol. Therefore, the coke or coke precursor on the acid sites was presumably removed by methanol vapor. These results indicate that a prolonged catalyst life in the vapor phase Beckmann rearrangement can be achieved by the optimum combination of catalyst and reaction atmosphere.調製ゲルにヒ素あるいはリンのような5価イオンを添加して調製した高シリカZSM-5およびこれを貴金属で修飾した触媒を用いてシクロヘキサノンオキシムの気相ベックマン転位反応を行い触媒の活性劣化に及ぼす希釈ガスおよび希釈溶媒の影響について検討した。希釈ガスとして二酸化炭素を用い希釈溶媒としてメタノールを使用すると貴金属修飾ZSM-5の触媒寿命が未修飾触媒の場合よりも著しく向上した。さらに希釈ガスとして微量の酸素を含むヘリウムを用いて転位反応を行うと貴金属修飾触媒の寿命が長くなった。この系に対しても希釈溶媒として触媒寿命に最良の効果を与えるものはメタノールであった。シクロヘキサノンオキシム濃度を増加させると触媒寿命が短くなることからメタノールは酸点に吸着したε-カプロラクタムのオリゴマーを脱離・除去するのに寄与していると考えられた。これらの結果から反応雰囲気を調整することにより固定層反応器による気相系ベックマン転位反応用触媒の寿命の延長が可能となることが分かった

Catalyst Deactivation of High-silica ZSM-5 Zeolite Modified with Noble Metals during Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime