The critical role of Zr in controlling the activity of Pd/Beta on the hydrogenation of phenol to cyclohexanone

The promoting effect of zirconium addition on Pd/Beta catalysts has been investigated in the selective hydrogenation of phenol to cyclohexanone in the aqueous phase. The activity of the catalyst in the reaction was greatly improved by introducing Zr atoms into the framework of H-Beta zeolite. An important synergy between the Zr species and Pd, affecting the Pd dispersion state on the support, has been observed. The modification of the support with Zr^(4+) improves the Lewis/Brφnsted acid ratio of the catalyst, suppressing the further transformation of cyclohexanone. The kinetics of Pd/Zr-Beta catalyst showed high selectivity to cyclohexanone. The catalytic results showed that the Pd/Zr-Beta had the best catalytic performance at the desired temperature of 80℃ for 5 h.

Progress in Processes and Catalysts for Dehydrogenation of Cyclohexanol to Cyclohexanone

The dehydrogenation of cyclohexanol to cyclohexanone is a crucial industrial process in the production of caprolactam and adipic acid, both of which serve as important precursors in nylon textiles. This endothermic reaction is constrained by thermodynamic equilibrium and involves a complex reaction network, leading to a heightened focus on catalysts and process design. Copper-based catalysts have been extensively studied and exhibit exceptional low-temperature catalytic performance in cyclohexanol dehydrogenation, with some being commercially used in the industry. This paper specifically concentrates on research advancement concerning active species, reaction mechanisms, factors influencing product selectivity, and the deactivation behaviors of copper-based catalysts. Moreover, a brief introduction to the new processes that break thermodynamic equilibrium via reaction coupling and their corresponding catalysts is summarized here as well. These reviews may off er guidance and potential avenues for further investigations into catalysts and processes for cyclohexanol dehydrogenation.

Kinetics of Cyclohexanone Ammoximation over Titanium Silicate Molecular Sieves

An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading, and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H2O2 decomposition reaction must be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.

Selective hydrogenation of phenol to cyclohexanone in water over Pd catalysts supported on Amberlyst-45

A series of Pd catalysts were prepared on different supports（Fe2O3,SiO2,ZnO,MgO,Al2O3,carbon,and Amberlyst-45） and used in the selective hydrogenation of phenol to cyclohexanone in water.The Amberlyst-45 supported Pd catalyst（Pd/A-45） was highly active and selective under mild conditions（40-100 ℃,0.2-1 MPa）,giving a selectivity of cyclohexanone higher than 89%even at complete conversion of phenol.Experiments with different Pd loadings（or different particle sizes） confirmed that the formation of cyclohexanone was a structure sensitive reaction,and Pd particles of12-14 nm on Amberlyst-45 gave better selectivity and stability.

Catalytic synthesis of cyclohexanone 1,2-propanediol ketal with H_4SiW_(12)O_(40)/PAn

A new environmental friendly catalyst, H_4SiW_(12)O_(40)/PAn was prepared andidentified by means of FT-IR, XRD and TG/DTA. Cyclohexanone 1,2-propanediol ketal was synthesizedfrom cyclohexanone and 1,2-propanediol in the presence of H_4SiW_(12)O_(40)/PAn The factorsinfluencing tlie synthesis were discussed and the best conditions were found out. The optimumconditions are: molar ratio of cyclohexanone to 1,2-propanediol is 1:1.4, the quantity of catalystis equal to 1.0 percent of feed stocks, and the reaction time is 40 min. H_4SiW_(12)O_(40)/PAn is anexcellent catalyst for synthesizing cyclohexanone 1,2-propanediol ketal and its yield can reachover 96.5 percent.

AmmAmmoximation of Cyclohexanone to Cyclohexanone Oxime Catalyzed by Titanium Silicalite-1 Zeolite in Three-phase System

An innovative green process of producing ε-caprolactam was proposed by integrating ammoximation and Beckmann rearrangement effectively. As a first part of the new process, TS-1 molecular sieve-catalyzed synthesis of cyclohexanone oxime from cyclohexanone, ammonia and hydrogen peroxide was carried out in a batch plant. Cyclohexane was used as the solvent in the three-phase reaction system. The influences of essential process parameters on ammoximation were investigated. Under the reaction conditions as catalyst content of 2.5% (by mass); H 2 O 2 /yclohexanone molar ratio of 1.10; NH 3 /cyclohexanone molar ratio of 2.20; reaction temperature of 343 K; reaction time of 5 h, high conversion of cyclohexanone and selectivity to oxime (both>99%) were obtained. Thus, the three-phase ammoximation process showed equal catalytic activity as TS-1 but much more convenient and simpler for the separation of catalyst in comparison to the industrial two-phase system with t-butanol used as solvent.

Synthesis of ε-Caprolactone by Oxidation of Cyclohexanone with Monoperoxysuccinic Acid

In the absence of catalyst,70%hydrogen peroxide was used to oxidize succinic anhydride to solid monoperoxysuccinic acid(PSA).Then PSA was applied to synthesis ofε-caprolactone(ε-CL)by oxidation of cyclohexanone in the heterogeneous system.In order to achieve material recycle,solid precipitated in the process of synthesizingε-CL was dehydrated via reactive distillation followed by recrystallization to prepare succinic anhydride,which was characterized by IR(infrared spectra)and1HNMR(1H nuclear magnetic resonance).Effects of molar ratio of PSA to cyclohexanone,acetic acid dosage,reaction temperature,reaction time on conversion of cyclohexanone,yield and selectivity ofε-CL were investigated respectively.The results indicated that conversion of cyclohexanone,yield and selectivity ofε-CL were upto 98.1%,97.5%and 99.4%respectively under the optimal conditions.In addition,in the process of synthesizing succinic anhydride,the optimal yield of succinic anhydride reached 67.4%.

A “Green” Cyclohexanone Oxidation Route Catalyzed by Hollow Titanium Silicate Zeolite for Preparing ε-Caprolactone,6-Hydroxyhexanoic Acid and Adipic Acid

Hollow titanium silicalite （HTS） molecular sieve has been synthesized, and information on its structure, physico- chemical characterization, as well as surface property was investigated by a host of analytical methods, such as XRF, XRD, low-temperature N2 adsorption/desorption, TEM, FT-IR, UV-Vis, 29Si MAS NIVIR, and XPS techniques. The characterization results suggest that HTS zeolite has a special hollow crystal structure and its mesopore volume is larger than that of TS-1 zeolite. The titanium species in this zeolite are composed of the framework tetrahedral Ti （IV） ions and extra-framework octahedral Ti （IV） ions, which tend to disperse into its bulk phase. This zeolite material also has been applied to catalyze the cyclohexanone oxidation process, and the products are not completely consistent with those results obtained by using TS-1 zeolite, which might be caused by their difference in pore structure and pore volume, especially the mesopore volume. Cy- clohexanone oxidation catalyzed by HTS zeolite is a representative consecutive reaction, the main target products of which are e-caprolactone, 6-hydroxyhexanoic acid and adipic acid. The effect of H202/cyclohexanone mole ratio on the cyclohexa- none conversion, the total target product selectivity, the distribution of three target products selectivity and their variations along with reaction time is also researched and analyzed, which indicate that HTS zeolite shows a high performance for the Baeyer-Villiger reaction of cyclohexanone and catalytic oxidation of 6-hydroxyhexanoic acid under mild conditions, and the quantity of active surface titanium species as well as the pore structure and mesopore volume controlling the mass diffusion rate are the key factors determining the catalytic activity of HTS zeolite and product selectivity.

Synthesis of Mesoporous Titanium Silicalite-1 with High Stability in Cyclohexanone Ammoximation

Mesoporous titanium silicalite-1(TS-1)was hydrothermally synthesized with the addition of triethanolamine(TEA)in the conventional process, and used in the cyclohexanone ammoximation in a continuous slurry reactor. The as-prepared TS-1 was characterized with X-ray diffraction(XRD), scanning electron microcopy(SEM), N_2 adsorption-desorption, Fourier transform infrared(FT-IR)spectroscopy, UV-Visible(UV-Vis)diffuse reflectance spectra and UV Raman spectroscopy. The results indicated that the addition of TEA resulted in the formation of mesopores and the slight increase of framework titanium in TS-1. TS-1 synthesized with the addition of TEA exhibited a higher stability in the cyclohexanone ammoximation than that without the addition of TEA, attributing to the increase of mesopore volumes and the slight increase of the framework titanium in TS-1. However, when the addition of TEA was up to TEA/SiO_2 ratio of 0.24, the crystallinity and framework titanium of TS-1 decreased markedly, and the average crystal sizes of TS-1 increased, with the catalyst stability becoming poor.

Phenol hydrogenation to cyclohexanone over palladium nanoparticles loaded on charming activated carbon adjusted by facile heat treatment

Selective phenol hydrogenation is a green approach to produce cyclohexanone.It still remains a big challenge to prepare efficient supports of the catalysts for the phenol hydrogenation via a simple and cost-effective approach.Herein,a facile approach was developed,i.e.,direct calcination of activated carbon(AC)under argon at high temperature,to improve its structure and surface properties.The modified AC materials were supported with Pd nanoparticles(NPs)to fabricate the Pd/C catalysts.The as-prepared Pd/C600 catalyst exhibits superior catalytic performance in the phenol hydrogenation,and its turnover frequency(TOF)value is 199.2 h^-1,1.31 times to that of Pd/C-raw.The Pd/C600 catalyst presents both better hydrophobicity and more structural defects,contributing to the improved dispersibility in the reaction solution(phenol-cyclohexane),the better Pd dispersion and the smaller Pd size,which result in the enhancement of the catalytic performance.Furthermore,the as-prepared Pd/C600 catalyst shows a good recyclability.

Environmentally-Friendly Catalytic Oxidation of Cyclohexanone with 30% H_2O_2 Solution: A Comparison Study between Hollow Titanium Silicate and Dealuminated HBEA Zeolites

Two clean liquid–phase cyclohexanone oxidation routes catalyzed by DHBEA and HTS zeolites, in the absence of organic solvents, have been developed for producing high value-added chemical intermediates. Under optimized conditions,the cyclohexanone conversion reaches up to 60%, and the selectivity of total target products(ε-caprolactone, 6-hydroxyhexanoic acid and adipic acid) is over 90% achieved by the HTS zeolite; while both cyclohexanone conversion and the 6-hydroxyhexanoic acid selectivity are over 95% obtained on the DHBEA zeolite. Both the Lewis and Br鰊sted acid sites of DHBEA zeolite can preferentially activate the carbonyl group of cyclohexanone without any impact on H_2O_2 molecules.Meanwhile, the HTS zeolite can predominantly make H_2O_2 more reactive, which agrees well with the molecular calculation results. Hence, two different Baeyer-Villiger oxidation mechanisms based on the activation of H_2O_2 and cyclohexanone are proposed. Then, 6-hydroxyhexanoic acid is formed via the ring-opening of ε-caprolactone. However, C-OH groups cannot be reactivated by DHBEA zeolite, leading to insignificant adipic acid formation, while the selectivity of adipic acid is 28.5% obtained on the HTS zeolite. Consequently, the higher catalytic performance of the DHBEA zeolite is ascribed to its larger amount of active sites and greater diffusion features than those of HTS zeolite.

Nb_(2)O_(5)promoted Pd/AC catalyst for selective phenol hydrogenation to cyclohexanone

Phenol hydrogenation is a green route to prepare cyclohexanone,an intermediate for the production of nylon 66 and nylon 6.The development of high-performance catalysts still keeps a great challenge.Herein,the activated carbon(AC)was modified with an acidic material Nb_(2)O_(5)to adjust the microstructure and surface properties of AC,and the influences of the calcination temperature and Nb_(2)O_(5)content on the catalytic performance of the Pd/AC-Nb_(2)O_(5)catalysts for the phenol hydrogenation to cyclohexanone were investigated.The Nb_(2)O_(5)with proper content can be highly uniformly distributed on the AC surface,enhancing the acidity of the Pd/AC-Nb_(2)O_(5)catalysts with comparable specific surface area and Pd dispersion,thereby improving the catalytic activity.The hybrid Pd/AC-10 Nb_(2)O_(5)-500 catalyst exhibits the synergistic effect between the Pd nanoparticles and AC-10 Nb_(2)O_(5),which enhances the catalytic activity for the hydrogenation of phenol.Furthermore,the as-prepared Pd/AC-10 Nb_(2)O_(5)-500 catalyst shows good reusability during 7 reaction cycles.

Measurement and Correlation of Vapor-Liquid Equilibrium of the 1,2-Epoxycyclohexane-Cyclohexanone Binary System at 101.3kPa

Many by-products are generated in the process of oxidizing cyclohexene to produce 1,2-epoxycyclohexane by hydrogen peroxide, including cyclohexanol, cyclohexanone, etc. To obtain high-purity 1,2-epoxycyclohexane, the by-products must be removed through rectification. Refining 1,2-epoxycyclohexane through rectification requires vapor-liquid equilibrium(VLE) data of the related system. Therefore, the VLE data of 1,2-epoxycyclohexane- cyc-lohexanone system were measured at 101.3 kPa using an improved EC-2 VLE still. The thermodynamic consistency of the data was then tested by Herington's method and the rigorous point-to-point method. The results obtained were exemplary. The VLE data were correlated by the Wilson and non-random two-liquid(NRTL) equations, using the error sum squares of the vapor composition as the objective function to obtain the model parameters. The difference between the calculated values and the experimental data is minor, indicating that the VLE data are suitable for engineering design.

Solid-Liquid Equilibria of Succinic Acid in Cyclohexanone,Cyclohexanol and Their Mixed Solvents

Solubilities were measured for succinic acid dissolved in cyclohexanone, cyclohexanol and 5 of their mixed solvents at the temperature range from 291. 85 K to 358.37 K using a dynamic method. The solubility data were regressed by λh equation, with,the average absolute relative deviation 3.47%. The binary interaction parameter is 0.306 7 for the mixed solvent of oyolohexanone and cyclohexanol was determined by correlating the experimental solubilities with the modified λh equation. When the binary interaction parameter was determined it can be used to extrapolate the solubilities of succinic acid in mixed solvents of cyclohexanone and cyclohexanol at any proportion.The average absolute relative deviation was 7. 69% by using the modified λh equation to correlate the solubility data, however, the average absolute relative deviation was 8.89% by using NRTL equation to correlate the solubility data. The results show that the accuracy of the modified λh equation is better than that of the NRTL equation for the solubility of succinic acid in the 5 mixed solvents of cyclohexanone and cyclohexanol.

The Effect of Platinum on Stability of the B_2O_3/TiO_2-ZrO_2 Catalyst for Beckmann Rearrangement of Cyclohexanone Oxime

The addition of platinum over the B2O3/TiO2-ZrO2 remarkably enhanced its catalytic stability in the vapor phase Beckmann rearrangement of cyclohexanone oxime under the carder gas of H2. The content of coke deposited on catalyst surface was decreased from 1.92% over the B2O3/TiO2-ZrO2 to 1.14% over the platinum promoted B2O3/TiO2-ZrO2 after reaction of six hours. This result indicates that the platinum added on the B2O3/TiO2-ZrO2 catalyst plays an important role in reducing the coke formation on the catalyst surface.

Synthesis and Crystal Structure of(2E,6E)-2,6-bis(2,3-dimethoxybenzylidene)cyclohexanone

The new title compound （2E,6E）-2,6-bis（2,3-dimethoxybenzylidene）cyclohexanone （C 24 H 26 O 5,M r=394.45） has been synthesized,and its crystal structure was studied.The title compound crystallizes in the orthorhombic system,space group Pca2 1 with a=17.536（2）,b=14.8515（16）,c=8.0512（9）,V=2096.8（4） 3,Z=4,D c=1.250 g/cm 3,λ=0.71073,μ=0.087 mm-1 and F（000）=840.The structure was solved by direct methods and refined to R=0.0533 and wR=0.1248 from 2727 observed reflections （I 2σ（Ⅰ））.The title molecules are connected through hydrogen bonds to generate a 3-D supramolecule.The preliminary biological tests showed definitely biological activity for the title compound.

Study on the Performance of Regenerated Catalyst for Ammonoximation of Cyclohexanone

The study on the deactivated catalyst and the regenerated catalyst for the 70 kt/a cyclohexanone ammonoximation commercial test unit had revealed that addition of a proper amount of silicon additive could suppress the solubilization-induced loss of silicon in catalyst while providing protection to the catalyst. Compared to the direct calcination method for catalyst regeneration, adoption of the regeneration method through pretreatment-calcination of catalyst could be more beneficial to the restoration of catalyst channels and enhancement of the performance of the regenerated catalyst, which could be repeatedly regenerated and utilized. The outcome of commercial scale testing of the catalyst had indicated the good performance of the regenerated catalyst, which could be used for four times, resulting in a reduction of the production cost of cyclohexanone-oxime in big chunks.

Crystal and Molecular Structure of 4-Phenyl-cyclohexanone Semicarbazone

C13H17N3O,Mr=231.30,monoclinic,P21/,a=7.094(5).b =32.14(l),c=5.894(4)A,β=112.84(4)°,Z=4,Dx=l.24 gcm-3,V=1238(l) A 3,λ(MoKα)=0.71069 A,μ=0.76 cm-1.F(000)=496,T=293K,R=0.060,Rω=0.062 for 1205 reflections(I】3σ(I)).The cyclohexane ring shows a slightly distorted chair conformation.The NHCONH2 group has a conformation with the C=O bond trans to the N-N bond.The molecules in the crystal are linked together by the O…H-N hydrogen bonding.forming an infinite ribbon.

Rapid Access to Free Phenols by Photocatalytic Acceptorless Dehydrogenation of Cyclohexanones at Room Temperature

Phenols are ubiquitous substructures in natural products and bioactive compounds.However,practical methods for the direct construction of phenols under mild conditions remain challenging.Herein,a photocatalytic acceptorless hydrogen-evolution aromatization of cyclohexanones or cyclohexenones at room temperature has been developed.The reaction features the visible-light and cobalt co-catalyzed sequential dehydrogenation of in-situ formed enol silyl ethers,which are regarded as a challenging process.This operationally simple method enables the synthesis of a series of phenols with diverse substitution patterns from cyclohexanones or cyclohexenones.Moreover,diverse substituted 1,2-,1,3-,and 1,4-benzenediols were obtained from cyclohexanediones,providing a general and straightforward method for the synthesis of phenols from simple starting materials under mild conditions.

Effect of sodium ions in synthesis of titanium silicalite-1 on its catalytic performance for cyclohexanone ammoximation

Titanium silicalite-1 （TS-1） has been hydrothermally synthesized with tetrapropylammonium hydroxide （TPAOH） as the template in the presence of various amounts of Na＋, characterized by inductively coupled plasma, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and ultro-violet-visible spectroscopy and studied in cyclohexanone ammoximation. The characterization results show that with the increase of Na＋ concentration in the synthesis, both the crystal sizes of TS- land extra framework Ti increase but framework Ti decreases. The addition of Na＋ below 3 mol-% of TPAOH in the synthesis does not influence the catalytic properties with above 98% conversion of cyclohexanone and 99.5% selectivity to cyclohexanone oxime. However, at the concentrations of Na＋≥3mol-% of TPAOH in the synthesis, the catalysts are deactivated faster with the increase of Na＋ addition, which can be attributed to more high molecular weight byproducts deposited in the large TS-1 particles and the loss of the frame-work titanium. The results of this work are of great importance for the industry.