Epoxidation of propylene with hydrogen peroxide catalyzed by heteropolyphosphatotungstate

The epoxidation of propylene with hydrogen peroxide catalyzed by a reaction-controlled phase transfer catalyst (RCPT) composed of quaternary ammonium heteropolyoxotungstates in acetonitrile medium is studied. The influence of several factors on the reaction is studied, such as the reaction temperature, the effect of H₂O amount, the reaction time, the effect of the catalyst amount, solvent effect and the recycle of the catalyst. Under mild conditions, H₂O₂ conversion is 98.6%, and propylene oxide (PO) selectivity based on H₂O₂ is 97.2%. During the epoxidation, the catalyst is dissolved in the solution. However, after H₂O₂ is used up, the catalyst can be recovered as a precipitate and can be recycled. We find that the recycled catalyst has similar catalytic activity as the fresh one.     

Efficient conversion of fructose to 5‐hydroxymethylfurfural by functionalized γ‐Al2O3 beads

Millimeter size γ‐Al₂O₃ beads were prepared by alginate assisted sol–gel method and grafting organic groups with propyl sulfonic acid and alkyl groups as functionalized γ‐Al₂O₃ bead catalysts for fructose dehydration to 5‐hydroxymethylfurfural (5‐HMF). Experiment results showed that the porous structure of γ‐Al₂O₃ beads was favorable to the loading and dispersion of active components, and had an obvious effect on the properties of the catalyst. The lower calcination temperature of γ‐Al₂O₃ beads increased the specific surface area, the hydrophobicity and the activity of catalysts. Competition between the reaction of alkyl groups and ‐SH groups with surface hydroxyl during the preparation process of the catalyst influenced greatly the acid site densities, hydrophobic properties and activity of the catalyst. With an increase in the alkyl group chain, the hydrophobicity of catalysts increased obviously and the activity of the catalyst was enhanced. The most hydrophobic catalyst C₁₆‐SO₃H‐γ‐Al₂O₃–650°C exhibited the highest yield of 5‐HMF (84%) under the following reaction conditions: reaction medium of dimethylsulfoxide/H₂O (V/V, 4:1), catalyst amount of 30 mg, temperature of 110°C and reaction time of 4 hr.     

Catalytic Performance and Characterization of Pt‐Co/Al2O3 Catalysts for CO2 Reforming of CH4 to Synthesis Gas

Pt‐Co/Al₂O₂ catalyst has been studied for CO₂ reforming of CH₄ to synthesis gas. It was found that the catalytic performance of me catalyst was sensitive to calcination temperature. When Co/Al₂O₃ was calcined at 1473 K prior to adding a small amount of Pt to it, the resulting bimetallic catalyst showed high activity, optimal stability and excellent resistance to carbon deposition, which was more effective to the reaction than Co/Al₂O₃ and Pt/Al₂O₃ catalysts. At lower metal loading, catalyst activity decreased in the following order: Pt‐Co/ Al₂O₃ > Pt/Al₂O₃ > Co/Al₂O₃. With 9% Co, the Co/Al₂O₃ calcined at 923 K was also active for CO₂ reforming of CH₄, however, its carbon formation was much more fast man that of the Pt‐Co/Al₂O₃ catalyst. The XRD results indicated that Pt species well dispersed over the bimetallic catalyst. Its high dispersion was related to the presence of CoAl₂O₄, formed during calcining of Co/Al₂O₃ at high temperature before Pt addition. Promoted by Pt, Co/Al₂O₄ in the catalyst could be reduced partially even at 923 K, the temperature of pre‐reduction for the reaction, confirmed by TPR. Based on these results, it was considered that the zerovalent platinum with high dispersion over the catalyst surface and the zerovalent cobalt resulting from Co/Al₂O₄ reduction are responsible for high activity of the Pt‐Co/Al₂O₃ catalyst, and the remain Co/Al₂O₄ is beneficial to suppression of carbon deposition over the catalyst.     

Cooperative Effect of Platinum and Alumina on Catalyst Deactivation for Dehydrogenation Reaction

The cooperative effect on catalyst deactivation of Pt-based catalysts for dehydrogenation reaction was investigated using the combination of Pt-based/SiO₂ and Al₂O₃. The presence of the effect was confirmed by reaction test, CO adsorption, H₂-TPD and TPO. Considering conversion, active site, H₂ uptake and the nature and amount of coke, interestingly, the physical mixture of Pt-based catalyst supported on SiO₂ with 100-120 mesh and Al₂O₃ 60-80 mesh was similar to Pt-based Al₂O₃. The concept of combination of two catalytic functions, acidity and metallic species, will certainly provide the possibility of better catalyst design.     

Shielded Sliding Discharge-Assisted Hydrocarbon Selective Catalytic Reduction of NOx over Ag/Al2O3 Catalysts Using Diesel as a Reductant

The nonthermal plasma generated in a shielded sliding discharge reactor was used to reform diesel for the hydrocarbon-selective catalytic reduction (HC-SCR) of NO_x on Ag/Al₂O₃ catalysts. Compared with raw diesel, the reformed diesel enhanced the NO_x reduction efficiency, mitigated hydrocarbon poisoning of the catalyst and reduced the fuel penalty for the HC-SCR reaction. The NO_x conversion values obtained with a commercial Ag/Al₂O₃ catalyst exceeded that of a 2.0 wt% Ag/Al₂O₃ catalyst prepared by wet impregnation. A significant amount of NH₃ was produced as a by-product during the HC-SCR reaction, which suggests that further NO_x conversion enhancement can be achieved by placing a second NH₃-SCR catalyst in series with the Ag/Al₂O₃ catalyst.     

Isotopic Labeling Reveals Active Reaction Interfaces for Electrochemical Oxidation of Lithium Peroxide

The unresolved debate on the active reaction interface of electrochemical oxidation of lithium peroxide (Li₂O₂) prevents rational electrode and catalyst design for lithium‐oxygen (Li‐O₂) batteries. The reaction interface is studied by using isotope‐labeling techniques combined with time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and on‐line electrochemical mass spectroscopy (OEMS) under practical cell operation conditions. Isotopically labelled microsized Li₂O₂ particles with an Li₂¹⁶O₂/electrode interface and an Li₂¹⁸O₂/electrolyte interface were fabricated. Upon oxidation, ¹⁸O₂ was evolved for the first quarter of the charge capacity followed by ¹⁶O₂. These observations unambiguously demonstrate that oxygen loss starts from the Li₂O₂/electrolyte interface instead of the Li₂O₂/electrode interface. The Li₂O₂ particles are in continuous contact with the catalyst/electrode, explaining why the solid catalyst is effective in oxidizing solid Li₂O₂ without losing contact.     

Kinetics of the Selective Reduction of NO with CH4 Over an In-Fe2O3/HZSM-5 Catalyst

A kinetic model presented for the selective reduction of NO with CH₄ over an In-Fe₂O₃/HZSM-5 catalyst by considering the process as a combination of two simultaneous reactions: NO+O₂+CH₄ (reaction 1) and O₂+CH₄ (reaction 2). Linear regression calculation was employed to find the kinetic parameters. It was found that although the activation energies of the two reactions were almost identical, the reaction rate constants were dramatically different, namely, k₁k₂, indicating that the NO+O₂+CH₄ reaction was more preferable to take place on the In-Fe₂O₃/HZSM-5 catalyst as compared with the O₂+CH₄ reaction.     

反应控制相转移催化原位过氧化氢环氧化丙烯反应

 以原位 H₂O₂ 为氧源, 在新型反应控制相转移催化剂 (RCPTC) 作用下丙烯环氧化反应中, 考察了反应温度、反应时间、H₂O₂ 浓度和催化剂浓度对反应性能的影响. 结果表明, 在适宜的反应条件下, RCPTC 催化剂循环使用 5 次后, 环氧丙烷产率仍维持在 85.6% 以上, 且催化剂循环反应 3 次后, 其组成趋于稳定.     

Development of high performance Cu/ZnO-based catalysts for methanol synthesis and the water-gas shift reaction

Our groups studies on Cu/ZnO-based catalysts for methanol synthesis via hydrogenation of CO₂ and for the water-gas shift reaction are reviewed. Effects of ZnO contained in supported Cu-based catalysts on their activities for several reactions were investigated. The addition of ZnO to Cu-based catalyst supported on Al₂O₃, ZrO₂ or SiO₂ improved its specific activity for methanol synthesis and the reverse water-gas shift reaction, but did not improve its specific activity for methanol steam reforming and the water-gas shift reaction. Methanol synthesis from CO₂ and H₂ over Cu/ZnO-based catalysts was extensively studied under a joint research project between National Institute for Resources and Environment (NIRE; one of the former research institutes reorganized to AIST) and Research Institute of Innovative Technology for the Earth (RITE). It was suggested that methanol should be produced via the hydrogenation of CO₂, but not via the hydrogenation of CO, and that H₂O produced along with methanol should greatly suppress methanol synthesis. The Cu/ZnO-based multicomponent catalysts such as Cu/ZnO/ZrO₂/Al₂O₃ and Cu/ZnO/ZrO₂/Al₂O₃/Ga₂O₃ were highly active for methanol synthesis from CO₂ and H₂. The addition of a small amount of colloidal silica to the multicomponent catalysts greatly improved their long-term stability during methanol synthesis from CO₂ and H₂. The purity of the crude methanol produced in a bench plant was 99.9 wt% and higher than that of the crude methanol from a commercial methanol synthesis from syngas. The water-gas shift reaction over Cu/ZnO-based catalysts was also studied. The activity of Cu/ZnO/ZrO₂/Al₂O₃ catalyst for the water-gas shift reaction at 523 K was less affected by the pre-treatments such as calcination and treatment in H₂ at high temperatures than that of the Cu/ZnO/Al₂O₃ catalyst. Accordingly, the Cu/ZnO/ZrO₂/Al₂O₃ catalyst was considered to be more suitable for practical use for the water-gas shift reaction. The Cu/ZnO/ZrO₂/Al₂O₃ catalyst was also highly active for the water-gas shift reaction at 673 K. Furthermore, a two-stage reaction system composed of the first reaction zone for the water-gas shift reaction at 673 K and the second reaction zone for the reaction at 523 K was found to be more efficient than a one-stage reaction system. The addition of a small amount of colloidal silica to a Cu/ZnO-based catalyst greatly improved its long-term stability in the water-gas shift reaction in a similar manner as in methanol synthesis from CO₂ and H₂.     

Fe3O4改性的Ru/γ-Al2O3催化剂的原位液相加氢性能

采用分步浸渍法制备负载型Ru-Fe₃O₄/γ-Al₂O₃ 催化剂, 并利用透射电子显微镜(TEM)、X 射线衍射(XRD)、N₂吸附-脱附(BET)、傅里叶变换红外(FTIR)光谱与X射线光电子能谱(XPS)表征催化剂的纳米颗粒粒径分布、晶相组成、表面结构及吸附物种等性质. 将Ru-Fe₃O₄/γ-Al₂O₃催化剂用于3,4-二氯硝基苯选择性原位液相加氢反应, 考察了反应条件对催化活性的影响, 并讨论了不同制备条件下催化剂的稳定性能. 结果表明, 在473 K、液压3 MPa、原料质量分数2%, 乙醇/水体积比75:25 的反应条件下, 3,4-二氯硝基苯的转化率为100%, 3,4-二氯苯胺的选择性高达96.4%. Fe₃O₄含量对催化剂稳定性能有显著影响, 当Ru和Fe 的质量分数分别为2%和6%时, 催化剂可稳定200 h以上. 表面吸附CO与积碳是导致催化剂失活的主要原因, 以Fe₃O₄作为高效的助剂, 进行水汽转换(WGS)反应与费托合成(FTS)可移除CO, 而采用煅烧法去除表面积碳. 晶相变化与纳米颗粒的聚集可能导致催化剂部分失活, 其原因以及再生方法需进一步考察.     

Physicochemical and Reactivity Studies on Polystyrene‐Cu/Al2O3 Catalysts: An Attempt to Control Copper Dispersion

The influence of coating of 5.0 (w/w%) Cu/γ‐Al₂O₃ catalyst by different ratios of polystyrene on the physicochemical and textural properties was studied. The physicochemical and textural properties of polystyrene‐`Cu/γ‐Al₂O₃ catalysts were investigated by N₂ adsorption, O₂ chemisorption, FTIR, XRD, TEM, and SEM. In addition, the kinetics of H₂O₂ decomposition as a model redox reaction over polymer coated and uncoated catalysts was investigated. The highest activity was achieved by 0.06 wt% polystyrene‐5.0Cu/γ‐Al₂O₃ catalyst. The parent 5.0Cu/γ‐Al₂O₃ catalyst showed auto‐catalytic first order mechanism, which was subjected to a pronounced modification to a simple first order one upon coating by polystyrene. This modification in the mechanism was accompanied with an increase in the apparent activation energy of the reaction. The observed high activity of 0.06 wt% polystyrene‐5.0Cu/γ‐Al₂O₃ catalyst was attributed to the role of polymer in enhancement of the degree of dispersion of the surface copper. However, the modification in kinetics of the reaction was attributed to the difference in the nature of Cu active sites namely, the polymer protected the metallic copper species on the surface of γ‐Al₂O₃ support against possible oxidation to copper sub‐oxides and/or that polymer might change the hydrophilic properties of the reaction media.     

钒氧化物催化CO2氧化异丁烷脱氢的研究

采用溶胶-凝胶法制备了一系列钒氧化物催化剂,并用于CO₂氧化异丁烷脱氢反应. 采用X射线衍射、低温N₂吸附-脱附、O₂程序升温氧化、程序升温表面反应和原位傅里叶变换红外光谱等方法研究了催化剂的性质. 反应结果表明,尽管所有钒氧化物催化剂的丁烯选择性都大于85%,但随着催化剂组成和制备方法的改变,催化活性和稳定性差异显著. 其中,12 wt% V₂O₅/Ce_0.6Zr_0.4O₂（7 wt%）-Al₂O₃的催化活性最高,而6 wt% V₂O₅-Ce_0.6Zr_0.4O₂（7 wt%）-Al₂O₃的稳定性最佳. 关联分析催化反应结果与催化剂表征表明,钒氧化物的催化活性取决于VO_x物种的结晶度和分散度,而催化剂表面所积重质焦炭的特性是决定催化剂稳定性的关键. 非稳态反应和原位光谱结果确认,CO₂氧化异丁烷脱氢遵循Mars-van Krevelen氧化还原机理.     

An active phase transformation on surface of Ni-Au/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst during partial oxidation of methane to synthesis gas

It was studied the influence of gold addition on physico-chemical properties and catalytic activity of bimetallic Ni-Au/Al₂O₃ catalyst in partial oxidation of methane (POM). The reduction behavior in hydrogen, XRD crystal structure, XPS spectra and POM catalytic activity were investigated. The reduction of Ni-Au catalyst is a prerequisite condition to catalyze POM reaction. The formation of Ni-Au alloy during high temperature reduction in hydrogen and also in the conditions of POM reaction was experimentally proved. The addition of gold to Ni/Al₂O₃ system improves catalyst stability and activity in POM reaction.     

Liquid-Phase Hydrogenation of Acetylene to Ethylene in a Flow on Pd/Al2O3 and Pd-Ga/Al2O3 Catalysts in the Presence of CO

Catalytic properties of Pd/Al₂O₃ and Pd-Ga/Al₂O₃ in selective liquid-phase hydrogenation of acetylene in a flow under pressure and the effect exerted on them by introduction of CO into the feed were studied. The presence of CO in the reaction mixture ensures the reaction with the predominant formation of ethylene. Introduction of gallium into the catalyst formulation prevents the catalyst deactivation. Simultaneous action of these factors allows reaching high yield of the target product in combination with long operation life of the catalyst.

     

Removal of dibenzothiophene in diesel oil by oxidation over a promoted activated carbon catalyst

Oxidative removal of dibenzothiophene (DBT) in n-octane solution by H₂O₂ on a promoted activated carbon (AC) catalyst was studied. DBT adsorption and catalytic behaviors on AC were examined. Effects of pH in aqueous phase, amounts of AC and formic acid (HCOOH) for promotion as well as initial molar H₂O₂/S ratio were investigated. Experimental results led to conclusion that DBT was readily oxidized by H₂O₂ over an AC catalyst promoted by HCOOH. Suitable amount of AC can improve the activity of H₂O₂ resulting in a deeper extent of sulfur removal. A 100% conversion of DBT in an octane solution by H₂O₂ oxidation was attained on the HCOOH-H₂O₂/AC catalyst at 80°C for a reaction time of 30 min.     

Study on CuO/Al2O3 catalytic ozone treatment of acid red B solution

A CuO/Al₂O₃ catalyst was prepared using the impregnation method. The catalytic activity of CuO/Al₂O₃ for the ozonation of acid red B (ARB) in aqueous solution was studied, the chemical oxygen demand (COD) removal rate was an indicator for catalytic activity evaluation. The effects of initial ARB concentration, solution pH, and different oxidative degradation systems on oxidative degradation of ARB solution were studied. The CuO/Al₂O₃ catalyst was characterized using X‐ray diffractometry (XRD), N₂ adsorption desorption test, X‐ray photoelectron spectroscopy (XPS), and zero‐point charge (pH_zpc). The results show that copper species on the carrier were in the form of CuO and highly dispersed on the carrier. CuO can increase the alkalinity of the Al₂O₃ surface, and the CuO/Al₂O₃ catalyst facilitates the decomposition of O₃ into ·OH, which was beneficial for the catalytic O₃ oxidation degradation reaction. With the increase of the initial concentration of simulated wastewater, the CuO/Al₂O₃ catalytic reaction still has a high COD removal rate. Alkaline solution was of benefit to catalyze the degradation of ARB solution. When the ARB solution pH = 8.93, the degradation reaction was carried out for 40 min, the COD removal rate reached 83.2%. The degradation reaction was dominated by the hydroxyl radical (·OH) reaction.     

Liquid Phase Friedel‐Crafts Alkylation over Mixed Metal Oxide Catalyst

Liquid phase Friedel‐Crafts alkylation of benzene with benzyl chloride was carried out over various ferrites viz. CuFe₂O₄, NiFe₂O₄, CoFe₂O₄, ZnFe₂O₄, and MgFe₂O₄. Among the various ferrites ZnFe₂O₄ showed the highest activity. These ferrites were prepared by co‐precipitation technique. The effect of variation of catalyst, speed of agitation and reaction temperature has been studied. Benzylation of other substrates such as toluene, anisole and chlorobenzene was also studied. The catalyst ZnFe₂O₄ was found to be reusable. The acid base properties of the catalyst were studied by cyclohexanol dehydration reaction and the data was correlated with activity.     

Selective oxidation of hydrogen sulfide to ammonium thiosulfate and sulfur over vanadium-bismuth oxide catalysts

The selective oxidation of hydrogen sulfide containing excess water and ammonia was studied over vanadium-bismuth mixed oxide catalysts. The investigation was focused on understanding the complex reaction steps and the roles of each metal oxide. Therefore, supported V₂O₅/TiO₂, V-Bi-O/TiO₂ catalysts and a mechanical mixture of V₂O₅ + Bi₂O₃ were tested in the reaction. Ammonia reacted either with H₂S or SO₂, produced from the oxidation of H₂S. Water vapor promoted the reaction of ammonia and SO₂. Strong synergistic phenomena in catalytic activity were observed for the mechanically mixed catalyst of V₂O₅ and Bi₂O₃. V-Bi-O/TiO₂ catalyst showed very high H₂S conversion without any considerable emission of SO₂. Temperature-programmed studies (TPR and TPO), XRD and Raman analyses revealed that the high catalytic performance of V-BiO/TiO₂ catalyst originated from the high redox capacity of the bismuth vanadate phase.     

The mechanism of selective NO<Subscript>x</Subscript> reduction by hydrocarbons in excess oxygen on oxide catalysts: VI. Spectroscopic and kinetic characteristics of surface complexes on a Ni-Cr oxide catalyst

The reaction mechanism of the selective catalytic reduction of NO_x by propane in the presence of O₂ on a commercial Ni-Cr oxide catalyst was studied using in situ IR spectroscopy. It was found that nitrite, nitrate, and acetate surface complexes occurred under reaction conditions. Considerable amounts of hydrogen were formed in the interaction of NO + C₃H₈ + O₂ or C₃H₈ + O₂ reaction mixtures with the catalyst surface. The rates of conversion of the surface complexes detected under reaction conditions were measured. The resulting values were compared to the rate of the process. It was found that, at temperatures lower than 200°C, nitrate complexes reacted with the hydrocarbon to form acetate complexes; in this case, the formation of reaction products was not observed. In the temperature region above 250°C, two reaction paths took place. One of them consisted in the interaction of acetate and nitrate complexes with the formation of reaction products. The decomposition of NO on the reduced surface occurred in the second reaction path. Nitrogen atoms underwent recombination, and oxygen atoms reoxidized the catalyst surface and reacted with the activated hydrocarbon to form CO₂ and H₂O in a gas phase.     

Hydrodeoxygenation of Anisole over Ni/α-Al2O3 Catalyst

Ni-based catalysts supported on di erent supports (α-Al₂O₃,γ-Al₂O₃, SiO2, TiO₂, and ZrO₂) were prepared by impregnation. Effects of supports on catalytic performance were tested using hydrodeoxygenation reaction (HDO) of anisole as model reaction. Ni/α-Al₂O₃ was found to be the highest active catalyst for HDO of anisole. Under the optimal conditions, the anisole conversion is 93.25% and the hydrocarbon yield is 90.47%. Catalyst characteriza-tion using H₂-TPD method demonstrates that Ni/α-Al₂O₃ catalyst possesses more amount of active metal Ni than those of other investigated catalysts, which can enhance the cat-alytic activity for hydrogenation. Furthermore, it is found that the Ni/α-Al₂O₃ catalyst has excellent repeatability, and the carbon deposited on the surface of catalyst is negligible.