Ammoximation Of Cyclohexanone Research Articles

Chemical and engineering bases for green H2O2 production and related oxidation and ammoximation of olefins and analogues.

Plastics, fibers and rubber are three mainstream synthetic materials that are essential to our daily lives and contribute significantly to the quality of our lives. The production of the monomers of these synthetic polymers usually involves oxidation or ammoximation reactions of olefins and analogues. However, the utilization of C, O and N atoms in current industrial processes is <80%, which represents the most environmentally polluting processes for the production of basic chemicals. Through innovation and integration of catalytic materials, new reaction pathways, and reaction engineering, the Research Institute of Petroleum Processing, Sinopec Co., Ltd. (RIPP) and its collaborators have developed unique H2O2-centered oxidation/ammoximation technologies for olefins and analogues, which has resulted in a ¥500 billion emerging industry and driven trillions of ¥s' worth of downstream industries. The chemical and engineering bases of the production technologies mainly involve the integration of slurry-bed reactors and microsphere catalysts to enhance H2O2 production, H2O2 propylene/chloropropylene epoxidation for the production of propylene oxide/epichlorohydrin, and integration of H2O2 cyclohexanone ammoximation and membrane separation to innovate the caprolactam production process. This review briefly summarizes the whole process from the acquisition of scientific knowledge to the formation of an industrial production technology by RIPP. Moreover, the scientific frontiers of H2O2 production and related oxidation/ammoximation processes of olefins and analogues are reviewed, and new technological growth points are envisaged, with the aim of maintaining China's standing as a leader in the development of the science and technologies of H2O2 production and utilization.

MOR-Type Titanosilicate with Specific Ti Location in Defective T3 Sites for Efficient Cyclohexanone Ammoximation

MOR-Type Titanosilicate with Specific Ti Location in Defective T3 Sites for Efficient Cyclohexanone Ammoximation

Electrocatalytic ORR-coupled ammoximation for efficient oxime synthesis.

State-of-the-art technology for cyclohexanone oxime production typically demands elevated temperature and pressure, along with the utilization of expensive hydroxylamine sulfate or oxidants. Here, we propose an electrochemistry-assisted cascade strategy for the efficient cyclohexanone ammoximation under ambient conditions by using in situ cathode-generated green oxidants of reactive oxygen species (ROS) such as OOH* and H2O2. This electrochemical reaction can take place at the cathode, achieving over 95% yield, 99% selectivity of cyclohexanone oxime, and an electron-to-oxime (ETO) efficiency of 96%. Mechanistic analysis reveals that, in addition to the direct ammoximation by in situ-generated OOH* by electrocatalytic ORR, Ti-MOR also play a major role in capturing OOH* directly and converting the in situ-generated H2O2 to OOH*, thus accelerating the ORR-coupled cascade production of cyclohexanone oxime. This work paves a mild, economical, and sustainable energy-efficient electrocatalytic route for the oxime production using oxygen, ammonium bicarbonate, and cyclohexanone.

Enhanced catalytic activity and catalyst stability in cyclohexanone ammoximation by introducing anatase into TS-1 zeolite

Titanosilicate (TS-1) is widely used in the oxidations with hydrogen peroxide as a green oxidant. In the conventional synthesis of TS-1, it is easy to form anatase, which has been normally regarded as a catalyst for invalid decomposition of H2O2. Here, we have demonstrated that the anatase in TS-1 can enhance both activity and stability of the catalysts in cyclohexanone ammoximation. These features could be attributed to the interaction of anatase with ammonia, which not only favors ammonia absorption in the ammoximation evidenced by changing ammonia order to lower value, but also raise the corrosive resistance of zeolite framework by stronger anatase-ammonia interaction. This strategy has been successfully applied to the preparation of industrial TS-1 for cyclohexanone ammoximation at a scale of 300,000 tons per year, which might open a new opportunity for the industrial production of titanosilicate with enhanced alkaline resistance and catalytic reactivity in the future.

Synthesis of hierarchical titanium silicalite-1 by seed silanization for selective oxidation reactions

The sole microporous structure of titanium silicalite-1 (TS-1) zeolite usually leads to diffusion resistances, which would negatively influence its catalytic performance. Herein, a small-crystal TS-1 zeolite with micropore/mesopore structure has been successfully synthesized by silanization of seed in a tetrapropylammonium bromide (TPABr)-ethanolamine hydrothermal system. Dodecyltrichlorosilane (DTS) was used to modify the surface of nanosized S-1 seed, then the synthetic precursor of TS-1 was crystallized around the silanized seed, and the mesopores were generated in the spaces occupied by the organosilanes as a result of the calcination of solid zeolite material. The pore diameter of mesopore could be adjusted from 2.9 nm to 7.3 nm relative to the changing of the molar ratio of DTS to SiO2 in seed from 0.05 to 0.45. The resultant hierarchical TS-1 with micropore/mesopore structure exhibited excellent catalytic performances in the propylene epoxidation and cyclohexanone ammoximation, which were even superior to that of hollow TS-1 obtained from post-synthesis treatment. This approach for the preparation of TS-1 with micro-mesopores could be easily realized in industrial application to provide a feasible strategy for the exploration of other hierarchical zeolites.

Green organic conversion with H2O2: challenges and opportunities

Hydrogen peroxide (H2O2), as a green oxidant, plays an important role in organic conversion reactions, such as cyclohexanone ammoximation and olefin oxidation. However, the production of H2O2 relies on the anthraquinone process, which is costly, complex, and typically done on clustered production. Furthermore, H2O2 is prone to decomposition or the generation of ineffective byproducts and unfavorable reactive groups, leading to low efficiency and waste of resources. Achieving the widespread application of H2O2 in green organic conversion reactions requires efficient utilization and low-cost on-site production of H2O2. Effective activation of H2O2 is the key to realizing efficient utilization of H2O2, which has been widely recognized. In addition, some emerging methods of on-site production of H2O2 are convenient and low-cost, which may gradually overcome the shortcomings of traditional methods in the future. In this review, we introduce common organic conversion reactions with H2O2, summarize the challenges of H2O2 activation, and review the progress on electrochemical, photoelectrochemical or photochemical H2O2 production. We also discuss the vision of organic conversion reactions via in-situ-generated H2O2.

Recent advances in the synthesis of TS-1 zeolite.

Heteroatomic zeolites as an important class of zeolites, have been widely applied in industrially catalytic processes due to their unique properties. As one of the most representative heteroatomic zeolites, titanosilicate zeolites have been extensively used in the selective oxidations of organic substrates with H2O2 such as cyclohexanone ammoximation, epoxidation of alkenes, and phenol hydroxylation. In this review, recent advances in the synthesis of TS-1 zeolite are briefly summarized, including use of low-cost raw materials (organic templates, silicon, and titanium sources), development of new synthesis routes (post-treatment synthesis, dry-gel conversion synthesis, solvent-free synthesis, and microwave-assisted synthesis), and new strategy for enhanced mass transfer in TS-1 crystals (synthesis of hierarchical and nanosized TS-1 zeolite). This review might help researchers to have a deep understanding on the synthesis of TS-1 zeolite and provide a new opportunity for the design and preparation of highly efficient TS-1 catalysts in the future.

Highly efficient catalytic production of oximes from ketones using in situ-generated H2O2.

The ammoximation of cyclohexanone using preformed hydrogen peroxide (H2O2) is currently applied commercially to produce cyclohexanone oxime, an important feedstock in nylon-6 production. We demonstrate that by using supported gold-palladium (AuPd) alloyed nanoparticles in conjunction with a titanium silicate-1 (TS-1) catalyst, H2O2 can be generated in situ as needed, producing cyclohexanone oxime with >95% selectivity, comparable to the current industrial route. The ammoximation of several additional simple ketones is also demonstrated. Our approach eliminates the need to transport and store highly concentrated, stabilized H2O2, potentially achieving substantial environmental and economic savings. This approach could form the basis of an alternative route to numerous chemical transformations that are currently dependent on a combination of preformed H2O2 and TS-1, while allowing for considerable process intensification.

Insights into the role of titanium sites in cyclohexanone ammoximation over titanium silicalite-1

The discovery of titanium silicalite-1(TS-1) is a milestone in the development of heterogeneous catalysts for the eco-benign and mild catalytic oxidation process. However, the interpretation of specific Ti location and its role in oxidation is severely hindered due to the limited crystal size of as-synthesized TS-1. Here, a high quality TS-1 (ca. 10 μm) was successfully fabricated by the pre-hydrolysis silica source strategy. As evidenced by powder X-ray diffraction crystallography, the preferred Ti locations were mainly found at T2, T4, and T11 in Ti-containing MFI framework. Combining multiple spectroscopy methods (i.e., FT-IR, UV–Vis, and UV Raman) and the reaction kinetics, the active center in TS-1 was demonstrated as an exposed site of hexa-coordinated titainum species. Furthermore, the powder X-ray crystallography also revealed that the ketone and oxime adsorbed in the zeolite host with intense host-guest interaction of framework oxygen atoms, and exhibiting an overwhelming spatial intimacy to the Ti species at the molecular scale. This unique phenomenon affords a plausible interpretation for the oxime reaction.

A novel hybrid process for production of cyclohexanone oxime and high temperature hydrogen production using solar energy

In the presented study, an integrated novel process for cyclohexanone oxime and power production by utilizing solar dish collectors and high temperature hydrogen production systems (water decay) is studied. This process is comprised from solar dish collectors, Cu-Cl thermochemical cycle, direct H2O2 production cycle, cyclohexanone oxime and organic Rankine cycle. In the thermochemical process, 2208 kg/h of oxygen and 278.5 kg/h of hydrogen are generated that 139.4 kg/h of hydrogen is the net generated hydrogen. Moreover, this system generates 9429.8 kW of power that 2419 kW of power is employed in Cu-Cl cycle, 808.8 kW is consumed in hydrogen peroxide production cycle and the rest, which is 6202 kW is the net produced power. This process for 6305.9 kg/h cyclohexanone produces 8504.3 kg/h cyclohexanone oxime. The cyclohexanone ammoximation also generates 1238 kW heat. Furthermore, a sensitivity analysis is performed to investigate the effect of some performance parameters on various design indicators. It can be comprehended that the increment of operating wall temperature leads to decrement of solar collector energy efficiency. On the other hand, increment of geometric concentration ratio results in higher collector thermal efficiency. By using more solar dishes, the generated cyclohexanone oxime, hydrogen and hydrogen peroxide molar flow rates rises 40.5%. 43.5% and 37.8%, respectively. Moreover, the organic Rankine cycle and total system’s efficiency increases 38.1% and 43.3%, respectively by increase in number of solar dishes.

Clean Synthesis of Ti-MWW by Utilizing the Recycled Mother Liquor.

This article introduces a clean and efficient method for the synthesis of Ti-MWW by utilizing the recycled mother liquor. The effects of titanium and silicon sources on the synthesis of Ti-MWW and the recycling of the mother liquor are discussed in detail. Precipitated silica prepared with Na2SiO3 and CO2 was selected as the silicon source, and TiCl3 was selected as the titanium source. The mother liquor was recycled five times, and the obtained samples showed good catalytic activity in cyclohexanone ammoximation. This work can be conducive to reducing the influence on the environment and economizing on materials for the industrial production of Ti-MWW.

Hydrophobized hollow TS-1 zeolite as pickering interfacial catalyst for selective oxidation reactions

Design of catalyst particles bearing excellent diffusion performance and suitable surface wettability is of great importance to the successful application of Pickering interfacial catalysis. In this study, selective oxidation reactions over hydrophobized hollow TS-1 zeolite were applied as probe reactions to investigate the influence of catalyst diffusion performance closely related to mesopore size on its catalytic activity. Hydrophobized hollow TS-1 zeolite particles were prepared via a post desilication treatment accompanied with precrystallization treatment. The synthesized hydrophobized hollow TS-1 zeolite was characterized by Scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, UV–vis absorption spectrometry, Fourier-transform infrared spectroscopy and Nitrogen adsorption-desorption. Stable Pickering emulsions including 1-hexene-hydrogen peroxide, cyclohexene-hydrogen peroxide and cyclohexanone-water were prepared with hydrophobized hollow TS-1 zeolite particles as emulsifier. HTS-1–393(2)-S zeolite synthesized with precrystallization at 393 K for 2 h presented the maximum values of 43.9 mol/(Ti-mol·h) for 1-hexene epoxidation, 15.7 mol/(Ti-mol·h) for cyclohexene epoxidation and 247.3 mol/(Ti-mol·h) for cyclohexanone ammoximation. In addition, HTS-1–393(2)-S zeolite particles displayed good reusability for more than five cycles.

Al-Modified Ti-MOR as a robust catalyst for cyclohexanone ammoximation with enhanced anti-corrosion performance

The skeleton desilication accompanied by Ti active sites leaching accounts for the dominant chemical deactivation reasons in the alkali liquid-phase ammoximation, which could be retarded by creating a protective Al-rich shell.

A Single‐Crystalline Hierarchical Zeolite via an Oriented Co‐Growth of Nanocrystals Based on Synergy of Polyelectrolytes and Hetero‐Atoms

AbstractHierarchical zeolites have attracted great attention due to the integration of mesopores and/or macropores into the microporous crystalline framework, which decreases the steric and diffusional limitations in the small‐size micropores of zeolites. Among them, single‐crystalline hierarchical zeolites are much desirable due to fewer crystalline defects, higher mechanical stability, and less blocking of the uniform direction of microporous channels, which show high catalytic performance in conventional industrially‐important small‐molecule reactions, and heavy‐oil catalytic cracking, biomass catalytic conversion, polymer degradation, etc. Here, a novel one‐pot kinetics‐dominated strategy was developed to synthesize titanium‐containing single‐crystalline hierarchical zeolites via synergy of polyelectrolytes and framework hetero‐atoms by means of concentrating the starting precursor, restriction of the Oswald ripening to protect nano‐crystals, as well as oriented attachment between nano‐crystals. The resultant zeolite displayed a much higher catalytic performance in olefin epoxidation and cyclohexanone ammoximation than those of conventional pure‐microporous zeolites.

Crossed intergrowth triggered TS-2 microsphere: Formation mechanism, modification and catalytic performance

TS-2 microspheres, consisting of intergrown primary nanocrystals, was prepared by controlling the synthetic parameters. The effects of the amount of quaternary ammonium cations as structure-directing agent, H2O/Si ratio, the presence of alcohol and the temperature were carefully investigated on the crystallization process. The high alkalinity was proved to be highly important for the preservation of the microsphere morphology initially formed, due to the unique intergrown stacking style. An alkali treatment with the aqueous solution of structure-directing agent, organic amine and ammonium salt and subsequent Na+ ion-exchange were performed to enhance the catalytic activity of TS-2 microsphere in the cyclohexanone ammoximation reactions, with both the conversion and selectivity higher than 99%. In the continuous reaction, the TS-2 microspheres exhibited to be durable catalyst with potential application in industrial ammoximation processes.

A cleaner ammoximation of cyclohexanone over Ti-MWW in dimethyl carbonate

In this paper, dimethyl carbonate was selected as the solvent for the cyclohexanone ammoximation over Ti-MWW. Under the optimized reaction conditions, high conversion of cyclohexanone (99.8%) and high selectivity to oxime (99.6%) were achieved. The results of reuse of the catalyst showed that the Ti-MWW in this reaction system had better stability. Though the deactivation of the catalyst occurred after being used five times, the selectivity to cyclohexanone oxime was still kept above 99.9%, and calcining could easily recover catalytic activity. This work may provide a more environmentally benign solution for the industry production of cyclohexanone oxime.

Improved Ti species distribution and hierarchical pores in TS-1: towards regeneration of TS-1 deactivated due to alkali corrosion

TS-1 deactivated in industrial cyclohexanone ammoximation can be effectively regenerated by hydrothermal treatment with TPABr and ethanolamine solution.

Highly efficient and greener synthesis of TS-1 in a flow system by recycling the mother liquid

Abstract In this work, a highly efficient synthetic route for TS-1 zeolites has been developed in a flow system, a greener preparation method is further proposed by recycling the mother liquid. The prepared TS-1 by recycling the mother liquid contained no extraframework Ti species with uniform size and high crystallization as well as excellent catalytic performance for cyclohexanone ammoximation in the flow system containing a tubular reactor and an autoclave. As the fast heating rate of flow chemical process, the crystallization time was shortened to 20 min at 175 °C. Due to the short crystallization, hardly TPAOH participated in the Hofmann elimination reaction except for the structure-directing usage. The full recycle of remained TPAOH in the mother liquid was reused after being concentrated via vacuum distillation, and this novel recycling technology could have 98.5% TPAOH utilization as well as 98.3% TS-1 yield. These results indicate that the flow chemical process plays a key role in the new greener approach for the TS-1 synthesis.

Regulation of framework titanium siting in MWW-type titanosilicates by boron and aluminum incorporation and its effect on the catalytic performance

Abstract The exploration of efficient catalysts with more accessible active titanium species based on the titanosilicate zeolites is in incremental demands for the construction of the high utilization active centers to the various reactions. Here, we report an active oxidation catalyst MWW-type titanosilicate (Al-Ti-MWW) with more “Ti” active species distributed on the zeolite surface obtained through the implantation of the heteroatom aluminum to the conventional Ti-MWW synthesis. Combined with the overall measurements, it was deduced that more “Ti” species were regulated to evenly distributed in the zeolite crystal, which was due to the competitive occupancy of the heteroatom Al, B and Ti over T locations. Consequently, the bulky-substrate reaction results such as the cyclohexene epoxidation reaction and cyclohexanone ammoximation reaction showed that the Al-Ti-MWW catalyst had a superior catalytic oxidation activity than that of conventional Ti-MWW. It is believed that the application of the convenient treatment method could provide an effective strategy for designing high-performance titanosilicate catalysts.

Improving the energy efficiency and production performance of the cyclohexanone ammoximation process via thermodynamics, kinetics, dynamics, and economic analyses

Abstract Cyclohexanone ammoximation is widely used as an efficient method to synthesize cyclohexanone oxime in industrial production. In this study, the cyclohexanone ammoximation production process was explored based on reaction kinetics in order to reduce its energy consumption and total annual cost. The effects of the reaction temperature, space time, and raw material ratios on the cyclohexanone oxime yield were analyzed. Under the optimized operating conditions, the maximum C6H11NO yield was 99.86%, and the minimum total annual cost was 5.988 × 107 $ per year. Dynamic control of the cyclohexanone ammoximation production process was further explored under the optimized conditions. The proposed control structure could achieve effective control and maintain the desired product yield when flow rate and composition disturbances were introduced. The energy and exergy analyses of the cyclohexanone ammoximation process show that its energy efficiency can be improved from a thermodynamic perspective. The combination of a steady state simulation and dynamic control, thermodynamic analysis, and economic performance evaluation provide insight into the improvement and operation of the cyclohexanone oxime production process.