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.

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.

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.

Effect of Extra-Framework Titanium in TS-1 on the Ammoximation of Cyclohexanone

Titanium silicalite (TS-1) without and with extra-framework titanium have been prepared and TiO_2 is also prepared under the same conditions.All the samples are characterized with XRD,FT-IR,and UV–Vis.The effects of extra-framework titanium in TS-1 on the ammoximation of cyclohexanone have been studied in a continuous slurry reactor.The characterization results reveal that the extra-framework titanium exists as anatase.The catalytic evaluation results show that the anatase has a positive effect on the ammoximation of cyclohexanone by extending the catalytic life because it also exhibits some activity,while the conversion of cyclohexanone and the selectivity to cyclohexanone oxime are not influenced.The anatase TiO_2 does not catalyze H_2O_2 decomposition appreciably compared with TS-1 without extra-framework titanium.The results are very useful in guiding the TS-1 production.

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.

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.

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.

Fluorine Modified TAPO-5： Synthesis and Catalytic Performance in Cyclohexanone Ammoximation

A series of fluorine modified TAPO-5 molecular sieves was synthesized by one-pot method using ammo- nittm hexafluorotitanate as titanium and fluorine sources. The XPS and DRS UV-Vis results indicated that the exis- tence of F could promote the formation of tetrahedrally coordinated framework Ti and A1, meanwhile, inhibit the formation of anatase TiO2 in TAPO-5 sieves due to the unique role ofF in the sol-gel process of metal ions. Further- more, TG, contact angle test, Py-FTIR and 27A1 MAS NMR results revealed that fluorine modification increased the surface hydrophobicity and the Lewis acidity of Ti active sites through forming AlxFy units in the neighborhood. All these factors make these fluorine modified TAPO-5 sieves exhibit good catalytic performance in the arnmoximation of cyclohexanone.

Note Microwave synthesis and pharmacological activity of Mannich base cyclohexanone derivatives

We have synthesized mannich base cyclohexanone using microwave irradiation method,and studied their pharma-cological activity.Based on analytical and spectral(IR,NMR and Mass) data,a number of mono as well as double mannich base cyclohexanones have been synthesized from primary and secondary amines and formaldehyde,and then purified and characterized. The required 3-aryl-2,4-diacetyl-5-hydroxy-5-methylcyclohexanone was prepared from appropriate aldehyde and acetylacetone. The synthesized compounds were screened for analgesic activity via standard approaches,and they have shown positive analgesic activity.

Catalytic oxidation of cyclohexene to cyclohexanone by a triple system in acidic aqueous acetonitrile medium

The catalytic oxidation of cyclohexene to cyclohexanone using Pd(OAc)(2)/HQ/FePc was investigated in an acidic aqueous solution of acetonitrile. The role of each component of this system in the oxidation of cyclohexene was explored by means of UV-VIS, IR, XPS spectroscopy and. cyclic voltammetry, respectively. Based on the experimental results, the mechanism of the oxidation of cyclohexene catalyzed by Pd(OAc)(2)/HQ/FePc was elucidated.

Asymmetric Direct Aldol Reaction of Cyclohexanone Catalyzed by （ N＇-BenzyI-N＇-D-prolyl）-trans-4- hydroxy-L-proline Hydrazide

A new proline catalyst, namely （N＇-benzyl-N＇-D-prolyl）-trans-4-hydroxy-L-proline hydrazide, has been prepared and proved to be a superior catalyst for the asymmetric aldol reaction of cyclohexanone and aromatic aldehydes, affording up to 98 ： 2 dr and 98% ee.

Gas-Phase Beckmann Rearrangement of Cyclohexanone Oxime over B-ZSM-5 Derived Titanosilicalite

Four different ZSM 5 zeolites are tested for the gas phase Beckmann rearrangement of cyclohexanone oxime (CHO) into lactam. B ZSM 5 derived titanosilicalite (Ti ZSM 5) exhibits catalytic performances comparable to hydrothermally synthesized titanosilicalite (TS 1), much better than B ZSM 5 and Al ZSM 5. The effect of reaction conditions (solvent, feed space velocity, and water) on the catalytic performance of Ti ZSM 5 is studied. It is found that a quantitative relationship exists among the feed space velocity, the reaction time, and the CHO constant conversion. Ethanol or methanol as solvent shows higher activity, lactam selectivity, and stability than benzene and n hexanol. The addition of water to the rearrangement with a maximum amount of 1.0 mole per mole CHO results in the increase of CHO conversion while no meaningful changes in lactam selectivity and stability are observed.

Influence of Na^(+) on the synthesis of silicalite-1 catalysts for use in the vapor phase Beckmann rearrangement of cyclohexanone oxime

Silicalite-1 was hydrothermally synthesized in the presence of different concentrations of Na+using tetrapropylammonium hydroxide(TPAOH)as a template.The synthesis was followed by a base treatment.The silicalite-1samples were characterized using X-ray diffrac-tion,scanning electron microscopy,N2 adsorption,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy and NH3 temperature-programmed deso-rption.The samples were used as catalysts for the vapor phase Beckmann rearrangement of cyclohexanone oxime.During the synthesis,the sodium ions were incorporated onto the silicalite-1 crystals,but were then removed by the base treatment.All the catalysts exhibited nearly complete conversion of cyclohexanone oxime toε-caprolactam with selectivities grater than 95%.Addition of less than 2.5 mol-%Na^(+)(relative to TPAOH)did not influence the catalytic properties.However,for Na+concentrations≥5 mol-%,the particle sizes of silicalite-1 increased and the catalytic activities decreased,which can be attributed to carbon deposition.The results in this work are of great importance for the polymer industry.

HREELS study on coadsorption of oxygen and cyclohexanone on the Pt(111) surface

The coadsorption of cyclohexanone and oxygen on Pt(111) has been investigated by HREELS and TDS. At 205 K the presence of oxygen induces an "extra" red\|shift of the C--O stretching of coadsorbed cyclohexanone. Heating this coadsorbed surface from 205 to 250 K leads to further dehydrogenation to form intermediate species and to complete disappearance of the C--O stretching band. Above 300 K, the molecule rings of dehydrogenation species cleave to form hydrocarbon fragments and CO molecules which directly desorb into the vacuum or react with preadsorbed oxygen to produce CO\-2 which leave the surface immediately. TDS results provide further evidence that the preadsorbed oxygen promotes the decomposition of cyclohexanone.

Towards the selectivity distinction of phenol hydrogenation on noble metal catalysts

Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry.Though a few catalysts with promising performances have been developed in recent years,the basic principle for catalyst design is still missing owing to the unclear catalytic mechanism.This work tries to unravel the mechanism of phenol hydro-genation and the reasons causing the selectivity discrepancy on noble metal catalysts under mild conditions.Results show that different reaction pathways always firstly converge to the formation of cyclohexanone under mild conditions.The selectivity discrepancy mainly depends on the activity for cyclohexanone sequential hy-drogenation,in which two factors are found to be responsible,i.e.the hydrogenation energy barrier and the competitive chemisorption between phenol and cyclohexanone,if the specific co-catalyzing effect of H 2 O on Ru is not considered.Based on the above results,a quantitative descriptor,E b(one/pl)/E a,in which E a can be further correlated to the d band center of the noble metal catalyst,is proposed by the first time to roughly evaluate and predict the selectivity to cyclohexanone for catalyst screening.