Development of highly effective catalyst for Beckmann rearrangement

采用连续流动装置进行了环己酮肟气相Beckmann重排反应。对各种沸石进行了研究，以阐明沸石孔对选择性的影响。在Ca-A和硼硅酸盐上获得了对ε-己内酰胺的高选择性，模板分子保留在孔中。这些沸石的孔径太小，环己酮肟分子无法进入。因此，揭示了产生大体积ε-己内酰胺的反应选择性地在这些沸石的外表面上进行，并且产生较小分子的副反应在孔内占主导地位。考察了各种氧化物的催化性能，以澄清活性中心的性质。强酸沸石、H-ZSM-5、H-丝光沸石、H-Y等，对ε-己内酰胺的选择性低（30-60摩尔%），这主要是因为形成了具有高沸点的副产物。碱性沸石、K-ZSM-5、K-镁碱沸石等，也表现出低选择性， ...更多信息 度（30-60摩尔%）。无定形氧化物、γ-氧化铝、二氧化钛、氧化锆等，得到低于40mol%的选择性。当使用结晶氧化物如H-镁碱沸石、Ca-A沸石、H-SAPO-5和silicalite-1时，获得较高的选择性（> 80mol%）。这些催化剂不具有强酸和强碱位点，由于副产物的积累少得多，这也导致了更高的稳定性。这些结果表明中性和弱酸性羟基对于ε-己内酰胺的形成也是活性的，并且这些羟基对于ε-己内酰胺的选择性和稳定形成比强酸或强碱位点更有效。然而，也具有中性羟基的硅胶表现出低选择性。用氯化铝处理硅胶，消除了部分表面羟基，提高了选择性。表面中性羟基浓度对ε-己内酰胺的选择性生成有重要影响。少

Vapor phase Beckmann rearrangement of cyclohexanone oxime was carried out with continuous flow system. Various zeolites were examined to clarify the effect of zeolite pore on the selectivity. High selectivity to epsilon-caprolactam was obtained on Ca-A and borosilicate with template molecules remaining in the pore. The pore sizes of these zeolites are too small for the molecules of cyclohexanone oxime to enter. Therefore, it was revealed that the reaction to produce bulky epsilon-caprolactam proceeds selectively on the external surface of these zeolite and that the side reaction to produce smaller molecules dominates inside the pore. Catalytic performances of various oxides were examined to clarify the nature of the active site. Strong acid zeolites, H-ZSM-5, H-mordenite, H-Y,etc., gave low selectivity to epsilon-caprolactam (30-60 mol%) mainly because of the formation of by-products having high boiling point. Basic zeolites, K-ZSM-5, K-ferrierite, etc., also exhibited the low selectiv … More ity (30-60 mol%). Amorphous oxides, gamma-alumina, titania, zirconia, etc., gave the selectivity lower than 40 mol%. Higher selectivity (>80 mol%) was obtained when crystalline oxides, such as H-ferrierite, Ca-A zeolite, H-SAPO-5 and silicalite-1, were used. These catalysts do not have strong acid and base sites, which also results in the higher stability due to much less accumulation of the by-products. These results indicate that neutral and weakly acidic hydroxyl groups are also active for the formation of epsilon-caprolactam and that these hydroxyls are more effective for the selective and stable formation of epsilon-caprolactam than strong acid or base sites. However, silica gel, which has also neutral hydroxyl groups, exhibited low selectivity. Treatment with aluminum chloride on silica gel, which eliminated part of surface hydroxyls, enhanced the selectivity. The surface concentration of neutral hydroxyl group may have an important role on the selective formation of epsilon-caprolactam. Less