Continuous Flow Reactor for Hydroxylation of Benzene to Phenol by Hydrogen Peroxide

The direct hydroxylation of benzene to phenol catalyzed by activated carbon-supported Fe (Fe/AC) in acetonitrile using H₂O₂ as the oxidant was studied in a continuous flow reactor. Results showed that the continuous operation could obtain high phenol yield of 28.1%, coupled with the turnover frequency of 3 h^-1, and high selectivity of 98% under mild condition. The catalyst was characterized by N₂ adsorption/desorption, Boehm titration, X-ray photoelectron spectra, and Fourier transform infrared spectroscopy. It was observed that iron may interact with the carboxyl group forming iron-carboxylate like species, which act as the active phase. The apparent activation energy obtained by fitting an Arrhenius model to the experimental data was 13.4 kJ/mol. The reaction order was calculated to be about 1, 0.2 for benzene and 0.7 for H₂O₂.     

Preparation, Characterization And Catalytic Properties OF α -Fe2O3/SiO2 Catalyst in Phenol Hydroxylation with Hydrogen Peroxide

7KH .H₂ O₃ /SiO₂ catalyst was synthesized by simple impregnation. The catalyst was characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and Mössbauer spectroscopy. The results showed that the size RI .H₂ O₃ particles on silica was very small. This kind of catalyst exhibited very good catalytic performance in phenol hydroxylation by H₂ O₂ to dihydroxy-benzene.     

Direct hydroxylation of benzene to phenol by supported vanadium substitution polyoxometalates using H<Subscript>2</Subscript>O<Subscript>2</Subscript> as oxidant

A practical method for the direct hydroxylation of benzene to phenol catalyzed by supported vanadium-substituted polyoxometalates using H₂O₂ as an oxidant is described. Three vanadium-doped polyoxometalate Na₂H₃PMo₁₀V₂O₄₀·xH₂O catalysts were designed and prepared through support on graphitic carbon nitride (g-C₃N₄), montmorillonite, and activated carbon and named as CN-PMoV₂, M-PMoV₂, and C-PMoV₂, respectively. Their characterization was elucidated through the Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). This heterogeneous catalyst demonstrated promising activity in the hydroxylation of benzene to phenol with H₂O₂. Especially, CN-PMoV₂ catalyst was highly active and selective even under mild conditions. Moreover, CN-PMoV₂ catalyst still has a certain catalytic effect even after three instances of repeated use.     

Surface characterization and catalytic evaluation of copper-promoted Al-MCM-41 toward hydroxylation of phenol

The Mobil Composition of Matter No. 41 (MCM-41) containing Cu and Al with Si/Al ratios varying from 100 to 10 and 1 to 6 wt.% of Cu was synthesized under hydrothermal and impregnation conditions, respectively. The samples were characterized by nitrogen adsorption–desorption measurements, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and ²⁹Si and ²⁷Al magic-angle spinning–nuclear magnetic resonance (MAS–NMR) spectra. X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. TPR patterns show the two-step reduction of Cu species. TPD study shows that Cu-impregnated Al-MCM-41 samples are more acidic than Al-MCM-41. From the MAS–NMR it was confirmed that most of the Al atoms are present tetrahedrally within the framework and some are present octahedrally in extraframework position. Impregnation of Cu shifted Al to the extraframework position. The catalytic activity of the samples toward hydroxylation of phenol in aqueous medium was evaluated using H₂O₂ as the oxidant at 80 °C. The effects of reaction parameters such as temperature, catalyst amount, amount of H₂O₂, and solvent were also investigated. Sample containing 4 wt.% copper-loaded Al-MCM-41-100 showed high phenol conversion (78%) with 68% catechol and 32% hydroquinone selectivity.     

Hydrodechlorination of 4-Chlorophenol on Pd-Fe Catalysts on Mesoporous ZrO2SiO2 Support

A mesoporous support based on silica and zirconia (ZS) was used to prepare monometallic 1 wt% Pd/ZS, 10 wt% Fe/ZS, and bimetallic FePd/ZS catalysts. The catalysts were characterized by TPR-H₂, XRD, SEM-EDS, TEM, AAS, and DRIFT spectroscopy of adsorbed CO after H₂ reduction in situ and tested in hydrodechlorination of environmental pollutant 4-chlorophelol in aqueous solution at 30 °C. The bimetallic catalyst demonstrated an excellent activity, selectivity to phenol and stability in 10 consecutive runs. FePd/ZS has exceptional reducibility due to the high dispersion of palladium and strong interaction between FeOx and palladium, confirmed by TPR-H₂, DRIFT spectroscopy, XRD, and TEM. Its reduction occurs during short-time treatment with hydrogen in an aqueous solution at RT. The Pd/ZS was more resistant to reduction but can be activated by aqueous phenol solution and H₂. The study by DRIFT spectroscopy of CO adsorbed on Pd/ZS reduced in harsh (H₂, 330 °C), medium (H₂, 200 °C) and mild conditions (H₂ + aqueous solution of phenol) helped to identify the reasons of the reducing action of phenol solution. It was found that phenol provided fast transformation of Pd⁺ to Pd⁰. Pd/ZS also can serve as an active and stable catalyst for 4-PhCl transformation to phenol after proper reduction.     

Ni-Ti-O混合氧化物的制备、表征及其富氧选择性催化还原NO

采用均匀共沉淀法制备了不同Ni/Ti摩尔比的Ni-Ti-O混合氧化物,考察了它们在富氧条件下丙烯选择性催化还原NO反应中的催化性能,并运用X射线衍射,N₂吸附-脱附、吡啶吸附、程序升温脱附和原位红外光谱对催化剂进行了表征.结果表明,Ni/Ti摩尔比为1的催化剂表现出最佳催化活性,430℃时NO_x转化率达68%.该催化剂具有锐钛矿结构,比表面积较高(149m²/g),有利于提高催化活性;其表面Lewis酸性位有利于硝酸盐物种的吸附,而硝酸盐物种是该反应的重要中间体.     

SBA-15负载的Cu(Ⅱ)席夫碱配合物催化的苯乙烯氧化反应制备苯甲醛

采用一步法将原硅酸四乙酯与3-氨丙基三乙氧基硅烷在表面活性剂P123作用下,酸性共水解制备出氨基功能化的介孔分子筛SBA-15(NH2-SBA-15),再利用其中氨基与水杨醛的缩合反应制备SBA-15固载的席夫碱,该席夫碱与Cu(NO3)2溶液反应最终制成固定于SBA-15的Cu(II)席夫碱配合物多相催化剂Cu-SBA-15.采用X射线衍射、红外光谱仪、紫外可见分光光度计、场发射电镜、透射电镜、N2吸附-脱附、元素分析、原子发射光谱和热重分析对催化剂进行了表征,并将此催化剂用于无有机溶剂条件下催化氧化苯乙烯制备苯甲醛,考察了反应时间、反应温度、H2O2用量、水的用量、催化剂用量对反应的影响.当反应温度为100°C,反应时间8 h,H2O2与苯乙烯的摩尔比为2:1,不额外添加溶剂,且催化剂用量为3.8 wt%时,苯乙烯的转化率最高为84.4%,苯甲醛选择性为83.9%,催化剂的TOF值为261.1 h–1,并且重复使用3次后活性没有明显下降.规则的孔道、较大的比表面积以及分布均匀的活性中心可能是催化剂活性提高的原因.     

固载于 Al-MCM-41 纳米孔道中的钒离子催化氧化烷基芳基硫化物

 VOSO₄ immobilized within nanoreactors of Al-MCM-41 (VO²⁺/Al-MCM-41) was synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption, and chemical analysis techniques. The prepared VO²⁺/Al-MCM-41 successfully catalyzes the oxidation of aryl alkyl sulfides and up to 99% conversion and 90% selectivity for the corresponding sulfoxides were obtained with H₂O₂ as oxidant in acetonitrile at room temperature in 30 min.     

Synthesis new Co–Mn mixed oxide catalyst for the production of light olefins by tuning the catalyst structure

In order to increase the catalyst activity for Fischer–Tropsch synthesis (FTS), the preparation methods of two new catalysts were studied. The chemically identical bimetallic Co–Mn/Al₂O₃ catalysts were synthesized by different synthetic methods: (a) via thermal decomposition of the complex [Co_1.33Mn_0.667(C₇H₃NO₄)₂(H₂O)₅].2H₂O ( 1 ) and (b) by the impregnation technique. The complex was characterized by the single‐crystal analysis, elemental analysis, and Fourier‐transform infrared (FT‐IR) spectroscopy. Both catalysts were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectrometry (EDS), Brunauer–Emmett–Teller (BET) specific surface area, hydrogen temperature‐programmed reduction (H₂‐TPR), and H₂‐chemisorption. The catalysts' activity was investigated for the Fischer–Tropsch synthesis in a fixed bed microreactor. Higher activity was obtained for the catalyst prepared by thermal decomposition of the inorganic precursor due to its small particle size, superior dispersion, and higher surface area. The results show that the catalyst prepared thermal decomposition has 21% ethylene, 10% propylene, and 50% C₅⁺ selectivity, while methane selectivity of this catalyst is 11% at 250°C. On the other hand, the catalyst obtained by the impregnation method displays 15% ethylene, 8% propylene, 29% C₅⁺_, and 29% methane selectivity at the same temperature.     

Application of novel and reusable Fe3O4@CoII(macrocyclic Schiff base ligand) for multicomponent reactions of highly substituted thiopyridine and 4H-chromene derivatives

In this research study we designed and synthesized Co^II(macrocyclic Schiff base ligand containing 1,4-diazepane) immobilized on Fe₃O₄ nanoparticles as a novel, recyclable, and heterogeneous catalyst. The nanomaterial was fully characterized using various techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy-dispersiveX-ray spectroscopy, thermogravimetric analysis, vibrating sample magnetometry, differential reflectance spectroscopy, Brunauere–Emmette–Teller method, inductively coupled plasma, and elemental analysis (CHNS). Then, the catalytic performance was successfully investigated in the multicomponent synthesis of 2-amino-4-aryl-6-(phenylsulfanyl)pyridine-3,5-dicarbonitrile and 2-amino-5,10-dioxo-4-aryl-5,10-dihydro-4H-benzo[g]chromene-3-carbonitrile derivatives. Furthermore, the catalyst was isolated using a simple filtration, and recovery of the nanocatalyst was demonstrated five times without any loss of activity.     

Baeyer‐Villiger oxidation of cyclopentanone over zeolite Y entrapped transition metal‐Schiff base complexes

Transition metal [M = VO (IV) and/or Cu (II)] complexes with Schiff base ligand, (Z)‐2‐((2‐hydroxybenzylideneamino)phenol (H₂L) have been entrapped in the super cages of zeolite‐Y by Flexible Ligand Method. Synthesized materials have been characterized by preferential physico‐chemical techniques such as inductively coupled plasma optical emission spectroscopy (ICP‐OES), elemental analyses (CHN), fourier transmission infrared spectroscopy (FTIR), electronic and UV‐reflectance spectra, Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron micrographs (SEMs), X‐ray diffraction patterns (XRD) and thermogravimetric analysis (TGA). The catalytic competence of zeolite‐Y entrapped transition metal complexes was examined in Baeyer‐Villiger (BV) oxidation of cyclopentanone using 30% H₂O₂ as an oxidant beside neat complexes to check the aptitude of heterogeneous catalysis over the homogeneous system. The effect of experimental variables such as mole ratio of substrate to an oxidant, amount of catalyst, reaction time, varying oxidants and solvents on the conversion of cyclopentanone was also tested. Under the optimized reaction conditions, one of the zeolite‐Y entrapped transition metal complex viz. [VO(L)H₂O]‐Y [where L = (Z)‐2‐((2‐hydroxybenzylideneamino)phenol] was found to be a potential contender by providing 80.22% conversion of cyclopentanone (TON: 10479.42), and the selectivity towards δ‐valerolactone was 83.56%.     

Green synthesis and application of nanoscale zero-valent iron/rectorite composite material for P-chlorophenol degradation via heterogeneous Fenton reaction

A zero-valent iron/rectorite nanocomposite (NZVI/rectorite) was developed as a heterogeneous H₂O₂ catalyst for P-chlorophenol degradation. The physicochemical properties of NZVI/rectorite were characterized by various techniques including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller analysis. Results showed that NZVI sphere nanoparticles were successfully loaded on the rectorite surface with less aggregation and good dispersion. Moreover, compared with acid-leached rectorite (30.91 m²/g), the NZVI/rectorite appeared to have larger surface area (50.75 m²/g). In addition, the effects of pH, reaction time, initial P-chlorophenol concentration, catalyst amount, and H₂O₂ dosage on the P-chlorophenol degradation were systematically investigated. Results showed that NZVI/rectorite presents better properties for the degradation and mineralization of P-chlorophenol compared with pristine NZVI due to the large surface area, low aggregation, and good dispersion of the former. The degradation mechanisms of P-chlorophenol by NZVI/rectorite were adsorption and reduction coupled with a Fenton-like reaction. Four successive runs of the stability and regeneration study also showed that the NZVI/rectorite were unchanged even after 100% of P-chlorophenol degradation ratio. This study has extended the application of NZVI/rectorite as environment function material for the removal of P-chlorophenol from the environment.     

Kinetics and reaction mechanism of phenol hydroxylation catalyzed by La-Cu<Subscript>4</Subscript>FeAlCO<Subscript>3</Subscript>

The present work synthesizes La-Cu₄FeAICO₃ catalyst under microwave irradiation and characterizes its structure using XRD and IR techniques. The results show that the obtained La-Cu₄FeAICO₃ has a hydrotalcite structure. In the phenol hydroxylation with H₂O₂ catalyzed by La-Cu₄FeAICO₃, the effects of reaction time and phenol/H₂O₂ molar ratio on the phenol hydroxylation, and relationships between the initial hydroxylation rate with concentration of the catalyst, phenol, H₂O₂ and reaction temperature are also investigated in details. It is shown the phenol conversion can reach 50.09% (mol percent) in the phenol hydroxylation catalyzed by La-Cu₄FeAICO₃, under the reaction conditions of the molar ratio of phenol/H₂O₂1/2, the amount ratio of phenol/catalyst 20, reaction temperature 343 K, reaction time 120 min, 10 ml_ distilled water as solvent. Moreover, a kinetic equation of v = k[La-Cu₄FeAlCO₃][C₆H₅OH][H₂O₂]. and the activation energy of E _a=58.37 kJ/mol are obtained according to the kinetic studies. Due to the fact that the HO-Cu⁺-OH species are detected in La-Cu₄FeAICO₃/H₂O₂ system by XPS, the new mechanism about the generation of hydroxyl free radicals in the phenol hydroxylation is proposed, which is supposed that HO-Cu⁺-OH species are transition state in this reaction.     

Synthesis and characterization of copper(II) complexes of sulfadiazine with amino acids: catalytic activity toward oxidation of phenol and catechol

New copper complexes of DL-methioninoylsulfadiazine (MTS) and L-cystinoylsulfadiazine (CYS) were prepared and characterized using elemental analysis, IR, electronic spectroscopy, EPR spectroscopy, and thermal analysis. The mode of binding indicates that copper binds to MTS through carbonyl oxygen with the amino group nitrogen while for Cu^II–CYS the copper binds through carbonyl oxygen and SH with removal of its proton. The proposed structures were supported by conformational analysis which showed predominance of the trans form of copper(II)-L-cystinoylsulfadiazine. The two complexes enhanced oxidation of phenol and catechol in the presence of H₂O₂ under mild conditions. The catalyst shows proficiency toward oxidation of phenol and catechol compared to the auto-catalytic oxidation. Cu^II–MTS exhibited higher catalytic activity than Cu^II–CYS. The phenol and catechol oxidation is inhibited by Kojic acid.     

制备方法对Al2O3掺杂Pt/WO3-ZrO2催化剂上正庚烷异构化反应的影响

采用恒pH法和非恒pH法制备了Al₂O₃掺杂的Pt/WO₃/ZrO₂催化剂,并用N₂吸附-脱附、X射线衍射、紫外-可见漫反射、CO化学吸附、X射线光电子能谱、²⁷Al魔角旋转核磁共振和吡啶吸附红外等技术对催化剂进行了表征.结果表明,相比于非恒pH法制备的催化剂,恒pH法制备的催化剂具有较高的比表面积和Pt分散度,在H₂气氛中产生更多的B酸位,从而表现出更高的催化正庚烷临氢异构化反应活性; 在200℃和质量空速0.9h^-1的反应条件下,正庚烷转化率达70.0%,明显高于非恒pH法制备的催化剂(43.5%).     

Iron oxide on carbon‐based supports as efficient catalysts for organic compounds oxidation

For the first time, iron oxide on carbon aerogel, amine functionalized carbon nanotube, black carbon and carboxylic acid functionalized carbon nanotube in the presence of H₂O₂ was reported as an efficient and stable catalyst for the selective oxidation of sulfides and alcohols. The catalysts were characterized by scanning electron microscopy, energy‐dispersive spectroscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. In the next step, catalytic reactivity toward sulfide to sulfoxide and alcohol to aldehyde/ketone oxidation in the presence of H₂O₂ was studied and discussed.     

Synthesis,crystal structure and catalytic activity of an oxo-diperoxo tungsten(VI) complex containing an oxazine ligand for selective oxidation of sulfides

Abstract

A novel oxo-diperoxo tungsten(VI) complex, [WO(O₂)₂(Hphox)], was prepared by reaction of WO₃ in H₂O₂ with an oxazine-type ligand, 2-(2′-hydroxylphenyl)oxazine (Hphox). The complex was characterized by FTIR, ¹H NMR and elemental analysis. The single-crystal X-ray diffraction studies revealed a seven-coordinate tungsten center with a distorted octahedral geometry. The [WO(O₂)₂(Hphox)] complex was applied as a catalyst in efficient and selective oxidation of sulfide to sulfoxide using 30% H₂O₂ or UHP (urea hydrogen peroxide) as oxidants. This catalyst showed excellent catalytic activities and high selectivities in producing a variety of aryl and alkyl sulfoxides under mild conditions. To get an insight into the mechanisms of oxidation of sulfides, the mechanistic studies were monitored by UV–Vis spectroscopy.     

CoNiFe2O4@Silica-SO3H nanoparticles: New recyclable magnetic nanocatalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones under solvent-free conditions

A useful and green synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones derivatives were achieved by one-pot cyclocondensation between substituted aryl aldehydes, diketone/ketoester, and urea/thiourea using magnetic CoNiFe₂O₄@Silica-SO₃H nanoparticles under solvent-free condition. The choice of this approach showed essential advantages such as short reaction time, simple work-up procedure, high activity of the catalyst, high yield of the reaction products, the magnetic properties of the catalyst, and environmentally amiable conditions. In addition, the catalyst recovered and reused four times without notable loss of its activity. The magnetic CoNiFe₂O₄@Silica-SO₃H nanoparticles were described by Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and vibrating sample magnetometer. The products were obtained with excellent yields (88–98%). The formation of the products was confirmed and identified with their physical properties (melting points), the FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry, and the elemental analysis.     

无溶剂条件下磷酸锆纳米粒子作为固体酸催化剂催化苯酚选择性烷基化(英文)

A facile synthesis of α-zirconium phosphate(ZP) nanoparticles as an effective, eco-friendly, and recyclable solid acid catalyst is reported. Polyvinylpyrrolidone(PVP) and polyvinyl alcohol(PVA) were used as organic matrix as dispersing agents and served as a template for the nanoparticles. Hydrogen bonds between ZP and PVA or PVP, along the polymer chains, appear to play an important role for improving the dispersion of in situ formed ZP. Following calcination of PVA/ZP or PVP/ZP, pure hexagonal ZP nanoparticles were obtained. The catalysts were characterized by nitrogen sorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy, and transmission electron microscopy. Pyridine-FTIR and temperature-programmed desorption of NH3 suggest the presence of Brnsted acid sites. The acidic properties of the catalyst were studied in Friedel-Crafts alkylation of phenol by tert-butanol, producing 2-tert-butylphenol, 4-tert-butylphenol, and 2,4-ditert-butylphenol. The alkylation reaction was performed in the presence of catalysts P2O5/Al2O3, P2O5/SiO2, α-ZrP(prepared in the absence of the polymers), and various ionic liquids. The use of the hexagonal ZP nanoparticle catalyst afforded an excellent phenol conversion(86%) and selectivity towards 4-tert-butylphenol(83%) under optimized reaction conditions. The catalyst was easily recovered from the reaction mixture, regenerated, and reused at least four times without significant loss in the catalytic activity.     

Synthesis and characterization of new synthetic oxygen carriers. A kinetic study of the reaction of the binuclear iron(III)–copper(II) complex with H<Subscript>2</Subscript>O<Subscript>2</Subscript>

New oxygen carriers have been synthesized by the interaction of the Cu^II/Ni^II derivative of the bis(5-nitroindazolyl)methane complex with 14-membered 1,8-dihydro-1,3,6,8,10,13-hexaazacyclotetradecane (M-mac), where M=Fe^III, Ni^II, Co^II, to yield binuclear complexes. These complexes have been characterized by physico-chemical methods: elemental analysis, i.r., ¹H-n.m.r., ¹³C-n.m.r., 2D cosy n.m.r., e.p.r., u.v.–vis. spectroscopy and cyclic voltammetry. A representative binuclear Fe^III–Cu^II complex was chosen to interact with H₂O₂ to elucidate the mechanistic pathway of oxygen binding in solution spectrophotometrically, and also by cyclic voltammetry. Hydrogen peroxide exhibits two mechanisms for binding, either (i) homolysis or (ii) heterolytic cleavage. The mode of H₂O₂ binding can be hazardous in (i) due to the threat of oxidative damage to the cellular structure, proteins and metabolites, or eco-friendly as in (ii) which produces innocuous products such as water and dioxygen. This study aims to combat the problems associated with H₂O₂ binding in nature by producing a parallel study on model compounds.