Gas-phase Beckmann Rearrangement Research Articles

Improving the stability and reactivity of SAPO-11 catalyst for gas-phase beckmann rearrangement by a simple and effective alkali-treated approach

ε-Caprolactam (CPL) is an important organic chemical raw material for preparing nylon-6 fiber and polyamide engineering plastics. Traditional production technology based on concentrated sulfuric acid leads to serious environmental pollution. Herein, we develop an economical and environmentally friendly strategy based on SAPO-11 molecular sieve as catalyst to produce CPL. Importantly, alkali engineering strategy to treat SAPO-11 molecular sieve was profited to remove the framework P and increase much Si island edge structures, consequently formatting the larger mesopores and enhancing the acidic properties, thus the catalytic performance and stability of the catalyst were significantly improved. Compared with the original SAPO-11, SAPO-11-TH had outstanding catalytic performance, the conversion of CHO and the selectivity for CPL were still more than 92% and 87% respectively when the reaction continuous reacted for 5 h at 6 h−1 weight hourly space velocity (WHSV). Interestingly, we found that the reactants can complete the conversion within an extremely short residence time (0.86 s), thereby obtaining higher spatiotemporal yields. What else, the catalyst obtained from simple calcination still exhibited excellent catalytic performance. We provide a facile, intriguing and scalable approach to treat catalyst SAPO-11 molecular sieve to form larger mesopores and high acidic strength that can be applied in the many catalytic fields.

Synthesis of titania-pillared layered tetratitanate and catalytic application in gas-phase Beckmann rearrangement

Synthesis of titania-pillared layered tetratitanate and catalytic application in gas-phase Beckmann rearrangement

Controlled synthesis of hierarchical beta zeolite through design template to enhance gas-phase beckmann rearrangement performance

Hierarchical Beta (BEA-H) with intra-crystalline mesoporosity was synthesized by employing a designed template of N(CH3)2-C6H12-N+(CH3)2-CH2-(p-C6H4)-CH2-N+(CH3)2-C6H12-N(CH3)2 [Cl-]2. Characterization results indicate that BEA-H was crystallized from the outer surface of quasi-spherical particle to the inner part. When it was used as a catalyst for the gas-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam, BEA-H exhibited a 2.3-fold longer lifetime in comparison to conventional Beta zeolite (BEA-C). The superior catalytic performance of BEA-H is attributed to its hierarchical pore structure and suitable acidity.

Preparation of NbOx/SiO2-coated structured packing material and it's catalytic performance in the gas-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam

Potential industrial applicability of a NbOx/SiO2 catalyst material was strongly improved by fixing μm-particles onto a structured packing. The granular catalyst displays a high catalytic performance in producing ε-caprolactam via gas-phase Beckmann rearrangement. However, applicability is strongly hampered because a high linear gas velocity and a small particle size are necessary to avoid diffusion limitations. These requirements would lead to an unacceptably high pressure drop in an industrial reactor. The novel NbOx/SiO2 structured packing catalyst displays, at high WHSV in a tube reactor, a constant high ε-caprolactam yield (96%) for at least 32h time-on-stream, without any indication of deactivation.

Kinetic Study on Gas-Phase Beckmann Rearrangement of Cyclohexanone Oxime to ε-Caprolactam over a Silica-Supported Niobia Catalyst

Reaction kinetics of the gas-phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam was studied over a NbOx/SiO2 catalyst in a fixed-bed reactor. Kinetic measurements were carried out by variation of cyclohexanone oxime partial pressure and reactor temperature in the range of 5 to 80 hPa and 360 to 420 °C, respectively. It was found that ethanol, used as solvent in addition to toluene, is essential for high catalytic performance. Reaction rates as a function of cyclohexanone oxime partial pressure display Langmuir-type behavior, but the results could not be interpreted satisfactorily on the basis of a Langmuir–Hinshelwood mechanism. Another kinetic scheme is proposed, involving a kinetic adsorption step for cyclohexanone oxime instead of an adsorption equilibrium. Activation energies for the adsorption step and for the Beckmann rearrangement reaction were found to be 154 and 68 kJ·mol–1, respectively. Substitution of ethanol by alcohols with longer chain length (e.g., n-hexanol) resulted in ...

NbOx/SiO2 in the gas-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam: Influence of calcination temperature, niobia loading and silylation post-treatment

NbOx/SiO2 catalyst materials prepared by the incipient wetness impregnation method were studied in the industrially relevant gas-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam. The catalytic experiments were carried out in a fixed bed reactor system at atmospheric pressure. Results have been complemented with Raman and FT-IR spectroscopy as well as N2 physisorption measurements. Optimal catalytic results were observed for a catalyst calcination temperature of 600°C and a niobia loading of 0.3wt.%. Raman spectroscopy revealed that isolated tetrahedral mono-oxo NbO4 surface species most probably play a key role in the catalytic reaction. Very positive effects were achieved by applying a catalyst silylation post-treatment. Firstly, the catalytic long-term stability increased very substantially as a consequence of a decreased coke deposition on the catalyst surface. Secondly, the harmful effect of water on catalytic performance was strongly suppressed even to such an extent that water could be added to the feed to enhance catalytic long-term stability. Cyclohexanone oxime conversion and ε-caprolactam selectivity could be maintained at constant high values >99% and around 95% respectively, for 26h time-on-stream. Finally, considering the Sumitomo gas-phase Beckmann rearrangement process as a benchmark, we made a rough comparison between the catalytic performances of our niobia/silica catalyst and the silicalite catalyst used by Sumitomo.

Nanosized molecular sieves as petroleum refining and petrochemical catalysts

Nanosized ZSM-5 was synthesized and used for straight run gasoline reforming. Nanosized β was synthesized and used for the alkylation of benzene and ethylene in ethylbenzene production. Nanosized titanosilicate molecular sieve with a hollow structure (HTS) was synthesized and used for the oximation of cyclohexanone. Nanosized silicalite-1 was synthesized and used for the gas phase Beckmann rearrangement of cyclohexanone oxime in caprolactam production. Recent progress in the synthesis and application of nanosized ZSM-5, β, TS-1, and silicalite-1 were reviewed. The catalyst lifetimes were prolonged when nanosized molecular sieves were used as petroleum refining and petrochemical catalysts. 概述了微藻生物能源技术中的微藻规模化培养的研究现状, 从藻种筛选、代谢机理、培养条件和光生物反应器几个不同的角度阐述了影响微藻规模化培养的因素, 为微藻生物能源的发展及光生物反应器的研发提供建议与思路.

New non-zeolitic Nb-based catalysts for the gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam

Niobium oxide (Nb2O5) supported on different oxides were investigated as catalysts for the gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam. Niobium supported on SiO2, SiO2Al2O3, TiO2 and ZrO2 were prepared by the incipient wetness impregnation method. The physico-chemical properties of all the catalysts were characterized by various techniques including X-ray diffraction (XRD), N2 physisorption, atomic emission spectroscopy (ICP–AES), scanning electron microscope (SEM), Fourier transmission infra red (FTIR) and Raman spectroscopy. The acidity of the catalysts was determined by measurements using NH3-TPD and FTIR of adsorbed pyridine. All these techniques revealed that niobium was well dispersed on the surface. The addition of niobium oxide on the SiO2 support resulted in very weakly up to medium acid sites, but only strongly reduced or almost negligible Brønsted acidity was identified. A cyclohexanone oxime conversion of about 100% and up to 98% caprolactam selectivities were achieved in the presence of Nb2O5/SiO2 catalyst depending on the reaction conditions. The catalytic performance of the different catalysts follow the order Nb2O5/SiO2>Nb2O5/SiO2Al2O3>Nb2O5/ZrO2>Nb2O5/TiO2. The effects of temperature, pressure, and solvents have been investigated. Based on these investigations, it can be conclude that in a comparison with the very expensive Nb loaded mesoporous MCM-41 catalyst, which is suitable for Beckmann rearrangement, can be replaced efficiently by very cheaply available Nb2O5-silica gel catalyst.

Gas phase Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam over mesoporous, microporous and amorphous Nb2O5/silica catalysts: A comparative study

The gas phase Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam was investigated over niobium containing mesoporous (Nb-MCM-41, Nb-HMS and Nb-SBA-15), microporous (Nb-Beta zeolite) and amorphous (Nb impregnated on SiO2) catalysts. A relation between catalytic activities, structural and the acidic properties was derived. The catalysts Nb2O5/SiO2, Nb-MCM-41, Nb-SBA-15, and Nb-HMS resulted in higher cyclohexanone oxime conversion and caprolactam selectivity compared with Nb-Beta zeolite. Almost 100% cyclohexanone oxime conversion and up to 98% caprolactam selectivity were achieved over Nb2O5/SiO2 catalyst. Further, the catalytic activity results of Nb-MCM-41 are fairly similar to Nb2O5/SiO2. The high activity of both catalysts is related to vicinal silanol groups and silanol nests with weak acidity and negligible Brønsted acid sites. The physico-chemical properties of the investigated catalysts were characterized by various techniques including X-ray diffraction, N2 physisorption, Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance, atomic emission spectroscopy (ICP-AES), and Raman spectroscopy. Catalyst acidity was measured by NH3-TPD and pyridine adsorbed FTIR spectroscopy. The structural characterization results revealed that Nb was incorporated into the mesoporous and microporous materials framework.

Surfactant-Directed Zeolite Nanosheets: A High-Performance Catalyst for Gas-Phase Beckmann Rearrangement

Silica nanosheets with an MFI zeolite topology having a thickness of 2 nm were synthesized following a synthetic route using [C16H33−N+(CH3)2−C6H12−N+(CH3)2−C6H13](OH−)2 as a zeolite structure-directing agent. The surfactant-directed zeolite nanosheets exhibited a remarkably long catalytic lifetime and high selectivity for the production of e-caprolactam via gas-phase Beckmann rearrangement of cyclohexanone oxime, as compared with amorphous silica and bulk silica zeolite. The distinct catalytic performance of the nanosheets is attributable to silanol groups located on the surfactant-terminated crystal surfaces.

Silicalite-1 deactivation in vapour phase Beckmann rearrangement of cyclohexanone oxime to caprolactam

Defective silicalite-1 is an efficient and selective catalyst in gas phase Beckmann rearrangement. A kinetic study of catalyst decay applied to Beckmann reaction of cyclohexanone oxime into ɛ-caprolactam performed with silicalite-1 as catalyst was carried out with reference to time on stream theory. Information about kinetic deactivation constant was obtained. Kinetic deactivation expressions based on the Wojciechowski model were developed by regressing the experimental data over the silicalite-1 catalyst. The kinetic reaction constant for fresh catalyst k o, the catalyst site deactivation constant k d , the sites deactivation reaction order m and the deactivation reaction order n′ with respect to cyclohexanone oxime were determined. It was established that k d was independent from residence time and only was affected by temperature and cyclohexanone oxime concentration. The model suggested a deactivation rate established on a second order reaction kinetic both for active centre and cyclohexanone oxime concentration.

Gas-phase Beckmann rearrangement of cyclododecanone oxime on Al,B-MCM-41 mesoporous materials

Gas-phase Beckmann rearrangement of cyclododecanone oxime (Cdox) to ω-laurolactam is reported for the first time on Al,B-MCM-41 catalysts. The Cdox conversion was studied by using a temperature programmed reaction experiment in the 325–450 °C temperature range employing 0.15 M Cdox in toluene/acetone solution. The oxime conversion increased gradually with reaction temperature from ca. 90% at 325 °C to ca. 95% at 450 °C, whereas the yield of the desired product ω-laurolactam decreased. The optimal reaction temperature was 375 °C, which balanced the conversion of Cdox, selectivity to ω-laurolactam and catalyst lifetime. In parallel, liquid-phase experiments were carried out under conventional heating. Weak and medium strength acid sites, higher strong acid B/L ratios and adequate pore diameter of untreated Al,B-MCM-41 materials favored an optimal performance for the gas-phase Beckmann rearrangement of Cdox, clearly improving the conversion, selectivity to ω-laurolactam and catalyst lifetime in gas-phase with respect to the conventional liquid-phase reactions.

Crosslinked TS-1 as stable catalyst for the Beckmann rearrangement of cyclohexanone oxime

Crosslinked TS-1 zeolite materials have been studied in the gas phase Beckmann rearrangement reaction of cyclohexanone oxime to ε-caprolactam. Crosslinking of the zeolite particles resulted in the formation of an additional mesoporosity leading to increased activity in the Beckmann rearrangement reaction. The increased activity can be correlated with the newly created mesopore surface. Possibly more important, together with increased catalytic activity of the materials, the deactivation behavior of the catalysts is very significantly improved.

Gas-phase Catalytic Beckmann Rearrangement over Crystalline BPO4 of Dehydration Ability

Abstract The crystalline BPO4 with a P/B ratio around 1.5 prepared by dehydration of boric and phosphoric acid was found to be an effective heterogeneous catalyst for the gas-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam.

Synthesis and Characterization of Boron Hydrotalcite-Like Compounds as Catalyst for Gas-Phase Transposition of Cyclohexanone-Oxime

Hydrotalcite-like compounds with boron anions in the interlayer were obtained using a coprecipitation method. The effect of different pH values during the preparation was investigated and the effect on crystallinity and phase distribution studied. The influence of different methods of acidity regulation was also analyzed. The efficiency of synthesis of boron-containing anionic clays was evaluated, and the good thermal stability of the materials was noted. Surface characteristics were determined by X-ray photoelectron spectroscopy and correlated to the bulk properties obtained by X-ray diffraction and 27Al and 11B MAS NMR. The samples tested in gas-phase Beckmann rearrangement showed caprolactam formation, and the results were related to the surface features.

Improved evaporation methods for the system ethanol + cyclohexanone oxime

Abstract The heterogeneously catalyzed gas phase Beckmann rearrangement for the production of e -caprolactam — the precursor of the polyamid Nylon-6 — requires the evaporation of the reactant mixture cyclohexanone oxime + ethanol in such a way that the formation of thermodynamically preferred byproducts, which strongly influence the product quality, is minimized. To optimize the evaporation process a fluidized bed evaporator, a flash evaporator and a pipe evaporator are compared. The lowest average by product formation was observed with the fluidized bed evaporator (0.69%), followed by the flash evaporator (1.67%) and the pipe evaporator (2.75%).

Hydroxyls nests in defective silicalites and strained structures derived upon dehydroxylation: vibrational properties and theoretical modelling

Defective silicalite, an efficient and selective catalyst in the gas phase Beckmann rearrangement reaction, has been characterised by infrared spectroscopy and by molecular modelling techniques. We report a detailed IR study on the effect of outgassing treatments at increasing temperature on silanols bands and on framework modes. The effect of a temperature decrease up to 100 K (during the IR measurement) on the H-bonding interactions has also been investigated. The interaction of silanols with mesitylene, a probe molecule which cannot penetrate the channels, has been studied in order to distinguish between internal and external OH groups. Molecular mechanics and ab initio methods have also been used to model the structure and the vibrational features of a properly designed nest in order to support the assignments of the IR spectrum.

Recent topics of research and development of catalysis by niobium and tantalum oxides

Current topics of catalysts containing niobium and tantalum, especially in the field of solid acid catalysis and selective oxidation of hydrocarbons are reviewed. Hydrated niobium oxide and hydrated tantalum oxide are highly acidic. Hydrated niobium oxide is active for the hydration of ethene to ethanol, and Nb–W mixed metal oxide is more active for the reaction. Acid properties of tantalum oxide are changed by being supported on SiO 2. Ta oxide/SiO 2, prepared by the chemical reaction between tantalum alkoxide and surface hydroxyl groups of SiO 2, is active and selective for the gas phase Beckmann rearrangement of cyclohexanoneoxime to caprolactam. Niobium oxide and tantalum oxide easily react with many other oxides to form mixed metal oxide phases with complex structure. Mixed metal oxide catalysts, containing molybdenum, vanadium, certain elements together with niobium are active for the selective oxidation of hydrocarbons. Especially, the selective oxidation of propane by such mixed metal oxide catalysts has been paid attention. Additionally, recent progress of environmental catalysts, promoted by niobium and tantalum compounds, namely catalysts for the pollution abatement is reviewed.

Gas phase beckmann rearrangement of cyclohexanone oxime over zirconia-supported boria catalyst

Gas phase Beckmann rearrangement of cyclohexanone oxime is studied with B 2O 3/ZrO 2 as the catalyst at 250–350°C. It is shown that B 2O 3/ZrO 2 is highly active and selective for the synthesis of ε-caprolactam at 300–320°C. Activity and selectivity of the B 2O 3/ZrO 2 catalyst are compared with other boria catalysts supported on Al 2O 3, TiO 2, SiO 2, MgO, and HZSM-5 (Si/Al = 25) on an 10% B 2O 3 basis at 300°C. At this boria load level, B 2O 3/ZrO 2 produces the best catalysis for the lactam synthesis. The load level of boria affects the behavior of B 2O 3/ZrO 2 catalyst: increasing the boria load (≤20%) results in an increase of the lactam selectivity, but the lactam yield follows variation of the oxime conversion which shows a maximum at 10% boria load. Acidity and boria dispersion structure of the B 2O 3/ZrO 2 catalysts are measured, respectively, by NH 3-TPD and IR spectroscopy. It is shown that the lactam yield is correlated with the number of intermediate strong acid sites that are responsible for ammonia desorption at 200–400°C. The optimum boria load (10%) of the B 2O 3/ZrO 2 catalyst corresponds to two overlayers of boria on the support. The first layer of boria interacts directly with the support surface with tetrahedral BO 4 as the structure unit; the other layers of boria are constructed by trigonal BO 3 units.

New catalytic technologies in Japan

Recent trends in R&D of catalytic technology in Japan (cleaner and more efficient production, environmental catalysts, and recycling processes) are overviewed and examples of recent achievements are listed. Examples are then described as zeolite-catalyzed organic reactions recently commercialized and expected to be commercialized: hydration of cyclohexene, synthesis of pyridine derivatives and gas-phase Beckmann rearrangement of cyclohexanone oxime. Finally, as an example of environmental catalysts, the NO x storage–reduction type three-way automobile catalyst, is introduced.