Beckmann rearrangement of cyclohexanone oxime p-toluenesulfonate on acidic catalysts

The Beckmann rearrangement of cyclohexanone oxime p-toluenesulfonate has been studied using several catalysts. The reaction is catalyzed by weakly acidic sites and seems to occur by way of O-(p-toluenesulfonyl)--caprolactim.

---

- -, . - -(-)--.

     

Vapor phase Beckmann rearrangement of cyclohexanone oxime over fluorinated alumina catalysts

The Beckmann rearrangement of cyclohexanone oxime to caprolactam has been studied in the vapor phase over fluorinated alumina catalysts containing 1 to 61 wt. % F. Addition of fluorine enchances the catalytic activity of Al₂O₃. Selectivity to caprolactam shows a maximum in the fluorine range 11–31%. It is likely that an optimum distribution of Lewis and Brönsted acidic sites on the catalyst surface is responsible for the high selectivity observed at intermediate fluorine contents. Addition of water to the gas phase causes a decrease in selectivity.

---

, 1 61 . % . Al₂O₃. 11–31%. , , . .

     

Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam using mesoporous molecular sieves ALSBA-15

Vapor-phase synthesis of ε-caprolactam (ε-C) from cyclohexanone-oxime (CHO) has been studied at 300-400^oC and atmospheric pressure using AlSBA-15(X) catalysts with different Si/Al mol ratios X in a fixed-bed, integral-flow reactor. The catalysts were characterized with ICP-AES, XRD, TEM, N₂ adsorption, ²⁷Al and ²⁹Si MAS-NMR, FT-IR and TPD of ammonia. A decrease of X value in AlSBA-15(X) diminishes both the BET surface area and the unit cell length but enhances the acid amount. The catalytic activity correlates with the catalyst acidity. AlSBA-15(10) exhibits excellent catalytic performance. This revised version was published online in June 2006 with corrections to the Cover Date.     

Hydrogen bond driven chemical reactions: Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water

Recent experiments have shown that supercritical water (SCW) has the ability to accelerate and make selective synthetic organic reactions, thus replacing the common but environmentally harmful acid and basic catalysts. In an attempt to understand the intimate mechanism behind this observation, we analyze, via first-principles molecular dynamics, the Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water, for which accurate experimental evidence has been reported. Differences in the wetting of the hydrophilic parts of the solute, enhanced by SCW, and the disrupted hydrogen bond network are shown to be crucial in triggering the reaction and in making it selective. Furthermore, the enhanced concentrations of H(+) in SCW play an important role in starting the reaction.     

A DFT study on secondary reaction pathways in the acid-catalysed Beckmann rearrangement of cyclohexanone oxime in aprotic solvent

In recent studies regarding acid-catalysed Beckmann rearrangement of cyclohexanone oxime in aprotic solvents it has been observed that a quite surprising hydrolysis of the starting material, i.e., cyclohexanone oxime, occurs even if the experimental conditions and the water concentration in the reaction mixture can not justify such a side-reaction. Being this apparent hydrolysis critical for catalyst selectivity and poisoning, a computational DFT study on a possible secondary reaction pathway, involving a bi-molecular reaction between two cyclohexanone oxime molecules in acid media as the primary step, is here reported to explain the experimental results.     

Synthesis of Ti-Hβ zeolites by liquid-solid isomorphous substitution and the catalytic properties in the vapor phase Beckmann rearrangement of cyclohexanone oxime

A series of Ti-Hβ zeolites were synthesized by liquid-solid isomorphous substitution. Hβ and Ti-Hβ zeolites were characterized by BET, XPS, IR, etc., and studied in the vapor phase Beckmann rearrangement of cyclohexanone oxime. In comparison with pure Hβ, the incorporation of Ti in the Hβ framework leads to larger BET surface area and weaker Br?nsted acid sites. The incorporation of Ti in the Hβ framework increases the conversion of cyclohexanone oxime and its stability. It is inferred that for the catalysts having the structure of a β zeolite, the suitable acid sites for the vapor phase Beckman rearrangement might be the weak Br?nsted acid sites.     

Preparation of tantalum-pillared magadiite and its catalytic performance in Beckmann rearrangement

Vapor phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam has been carried out using tantalum-pillared magadiites (Ta-magadiites) with different surface areas as catalysts. The Ta-magadiite catalysts of relatively large surface areas showed high catalytic activities, due to a large number of active sites. For the Ta-magadiite catalyst of the largest surface area, the oxime conversion reached 99.1%, with 97.5% of lactam selectivity. FT-IR and NH₃-TPD results demonstrated that the new hydroxyl groups and a large amount of acidic sites generated by Ta pillaring into the magadiite interlayer were responsible for the high catalytic performance of Ta-magadiite catalyst.     

Beckmann rearrangement of 15N-cyclohexanone oxime on zeolites silicalite-1, H-ZSM-5, and H-[B]ZSM-5 studied by solid-state NMR spectroscopy

By means of solid-state 15N NMR spectroscopy, evidence for the formation of nitrilium ions as intermediates of the Beckmann rearrangement of 15N-cyclohexanone oxime to epsilon-caprolactam on silicalite-1, H-ZSM-5, and H-[B]ZSM-5 is reported. The zeolites under study are characterized by different acid strengths (silicalite-1 < H-[B]ZSM-5 < H-ZSM-5). Depending on the nature of catalytically active surface OH groups, reactant and product molecules exist in the nonprotonated or protonated state. In addition, formation of byproducts such as 5-cyano-1-pentene and epsilon-aminocapric acid as a result of dehydration and hydrolysis of the reactant and product molecules, respectively, were observed.     

Catalyzed Beckmann rearrangement of cyclohexanone oxime in heterogeneous liquid/solid system: Part 2: Influence of acid catalysts and organic promoters

The influence of some transition metal oxide promoters in the catalyzed Beckmann rearrangement of cyclohexanone oxime was studied by preparing several heterogeneous H₂SO₄/M/SiO₂ catalysts using SiO₂ as support and H₂SO₄ as acid source. A definite effect of each metal has been observed and the best results have been obtained with Cr-, Zr- and Zn-oxides based promoter, which have shown an improved selectivity towards -caprolactam formation if compared to the H₂SO₄/SiO₂ catalytic system. Moreover, the influence of some organic promoters on the reaction pathway was investigated. Acetic and trifluoroacetic anhydrides gave the best results, even if only the latter allowed the rearrangement even without solid acid catalysts. The transacetylation of the cyclohexanone oxime by using the acetyl caprolactam, which is the product of rearrangement of the acetyl cyclohexanone oxime, was studied for developing a step wise catalytic cycle. Finally, some preliminary results on a homogeneous organic catalyzed process are reported.     

Beckmann rearrangement of acetylthiophene oxime benzenesulfonates as a method for the synthesis of acetamidothiophenes

The Beckmann rearrangement of 2-acetylthiophene, 5-methyl-2-acetylthiophene, 5-chloro-2-acetylthiophene, and 2,5-dichloro-3-acetylthiophene oxime benzenesulfonates to the corresponding acetamidothiophenes was carried out by heating with an aqueous methanol solution of sodium acetate. This method can be used for the preparative synthesis of 2-acetamidothiophene and 2,5-dichloro-3-acetamido-thiophene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–485, April, 1985.     

Beckmann rearrangement of the E isomer of cis-4,6,6-trimethylbicyclo[3.1.1]-heptan-2-one oxime

The individual E isomer of 4,6,6-trimethylbicyclo[3.1.1]heptan-2-one oxime has been obtained, and its transformations under the conditions of acid catalysis have been studied. The action of sulfuric acid on a solution of the oxime in acetonitrile leads to the selective formation of 5,7,7-trimethyl-2-azabicyclo[4.1.1]octan-3-one, while the action of hydrochloric acid with heating gives 4-isopropyl-3-methylaniline.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 29–32, January–February, 1991.     

Silicalite-1空心球材料制备及其在Beckmann重排反应中催化应用研究

以碳微球作为硬模板、纳米Silicalite-1分子筛作为壳层,采用水热法合成了Silicalite-1空心球材料。采用XRD、SEM、FT-IR、N_2吸附、29Si M AS NM R、TG、XPS等技术对催化剂的物相、形貌和性能等进行表征,发现该空心材料具有较高的结晶度、发达的多级孔道结构和丰富的表面羟基。与传统方法制备的Silicalite-1分子筛催化剂相比,Silicalite-1空心材料在环己酮肟Beckmann重排反应中表现出优异的催化性能,使环己酮肟的转化率达99%、己内酰胺的选择性达94%,同时催化剂保持极佳的稳定性。研究表明,Silicalite-1空心材料中具有的大量巢式硅羟基和末端硅羟基是Beckmann重排反应的主要活性位,且可通过简单焙烧再生实现羟基活性位的完全恢复。     

Controlling the performance of silicalite-1 membranes

The structural and performance characteristics (for n- and i-butane separation) of self-supported silicalite-membranes, were optimised by fine-tuning their syntheses by screening a total of nine silica sources and many reaction conditions. The mass balances indicate that membrane thickness is a function of both the synthesis volume and the silica source used. The excellent properties of the final membrane are demonstrated by its high permselectivity of 31 for n-butane combined with a n-butane flux of 10 mmol m(-2)s(-1), indicating perfect performance. For 50/50 mixtures (of n and i) the selectivity for nbutane was 48 and its flux was 3.8 mmol m(-2)s(-1). For the given selectivities, in relation to the membrane thickness, the theoretical fluxes are the highest values ever reported, underlining the point that high structural integrity is essential to achieve superior functionality.     

Deactivation and regeneration of the B2O3/TiO2-ZrO2 catalyst in the vapor phase Beckmann rearrangement of cyclohexanone oxime

The deactivation and regeneration of B₂O₃/TiO₂-ZrO₂ catalyst for the vapor phase Beckmann rearrangement of cyclohexanone oxime to -caprolactam were studied. The fresh, deactivated and regenerated catalysts were characterized by using adsorption of nitrogen, X-ray diffraction (XRD), thermogravimetry (TG) and NH₃-temperature-programmed desorption (NH₃-TPD) techniques. The crystal structure and pore size distribution of the catalyst were retained after reaction, but the number of acid sites decreased significantly. There was a relationship between the amount of coke deposited on the catalyst and the decline in catalytic activity. These results suggest that the coke deposition on the surface of catalyst is mainly responsible for the catalyst deactivation. The catalytic activity can be recovered completely after calcining the deactivated catalyst in air flow at 600 °C for 8 h.     

Vapor-phase Beckmann rearrangement of cyclohexanone oxime over B2O3 catalysts supported on TiO2-ZrO2 mixed oxide

A novel catalyst, boria supported on titania-zirconia mixed oxide, exhibits very high catalytic activity and selectivity in vapor-phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam. It gives 99.7% oxime conversion and 97.0% lactam selectivity at 300°C.     

Quantum-chemical modelling of proton transfer in the Beckmann rearrangement

A model of proton transfer in the Beckmann rearrangement was developed by density functional theory (DFT) for the example of acetaldoxime. It was concluded that the Beckmann rearrangement of acetaldoxime may consist of three stages: Transfer of a proton from the imine carbon atom to the nitrogen atom with the formation of an acetaldoxime cation; formation of an enolic imine by an intermolecular mechanism; formation of acetamide (the final product of the Beckmann rearrangement) also by an intermolecular mechanism. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 144–147, May–June, 2008.