Nanostructured ruthenium on γ-Al2O3 catalysts for the efficient hydrogenation of aromatic compounds

Free and trioctylamine (TOA)-stabilized ruthenium nanoparticles have been prepared by decomposition of the metal precursor Ru(η⁶-cycloocta-1,3,5-triene)(η⁴-cycloocta-1,5-diene) under mild conditions (room temperature, hydrogen atmospheric pressure). The nanoparticles have been deposited on γ-Al₂O₃ supports having different surface area. The resulting systems are active in the hydrogenation of methyl benzoate to methyl cyclohexanoate with a reaction rate decreasing in the order Ru(TOA)/γ-Al₂ O₃ (high surface area, catalyst D) > Ru(TOA)/γ-Al₂O₃ (catalyst C) > Ru/γ-Al₂O₃ (high surface area, catalyst B) > Ru/γ-Al₂O₃ (catalyst A). Catalysts A-D are long lived and can be reused without loss of activity; they are considerably more active than a commercial ruthenium on γ-Al₂O₃ sample. High Resolution Transmission Electron Microscopy analyses of such systems show that the nanoparticles are homogeneously dispersed on the support and that the size distribution decreases in the order catalyst A, 2.9 nm > catalyst B, 2.8 nm > catalyst C, 2.4 nm > catalyst D, 2.3 nm. Based on the easy hydrogenation of the aromatic ring to the cyclohexane derivative, an efficient synthesis of 4-carbomethoxyformylcyclohexane, important starting material in the preparation of pharmaceutical products, from the largely available methyl 4-formylbenzoate, has been set up in the presence of catalyst D.     

Catalytic Combustion of Styrene over the Binary Mixture of Manganese and Copper Based Catalyst in the Absence and Presence of Water Vapor

MnO _x and MnCu based catalysts prepared by ultrasonic impregnation methods were characterized by XRD, TPR-H₂, XPS and N₂ adsorption and tested for styrene combustion in the presence and absence of water vapor. Results showed that the loading of binary mixtures of manganese oxide and copper oxide on γ-Al₂O₃ increased the ratio of Cu⁺/Cu²⁺ of the defect spinel of Cu_1.5Mn_1.5O_4–x and the reducibility of the catalyst and in this way increased the catalytic activity of the catalysts for styrene combustion. The catalyst MnCu/γ-Al₂O₃ (20%/l) with 20 wt % loading amount and the Mn/Cu ratio of 1 : 1 showed the highest catalytic activity with T₉₀ = 214°C. Water vapor in feed steam decreased the activity of the catalysts MnCu/γ-Al₂O₃ (20%/l) and Mn₂O₃/γ-Al₂O₃ (10%). The catalyst MnCu/γ-Al₂O₃ (20%/l) had more resistant to negative influence of water vapor. Upon addition of 2.94 vol % water vapor to the feed stream a 6.5% decrease in styrene conversion was observed whereas for the catalyst Mn₂O₃/γ-Al₂O₃ (10%) a 14% reduction in conversion at the same condition was recorded. Higher resistance to the negative influence of water vapor could be due to weaker interactions between water molecules and the surface of catalyst.     

Ethanol synthesis from syngas on Mn- and Fe-promoted Rh/γ-Al2O3

The catalytic hydrogenation of CO was studied over Mn- and/or Fe-promoted Rh/γ-Al₂O₃ catalysts. The catalysts were characterized by means of XRD, BET, H₂-TPR·H₂-TPD, XPS and DRIFTS. CO hydrogenation results showed that the doubly Mn- and Fe-promoted Rh/γ-Al₂O₃ catalysts exhibited superior catalytic activity and better ethanol selectivity. The DRIFTS results showed that Mn promoter stabilized the adsorbed CO on Rh⁺ and Fe stabilized adsorbed CO on Rh⁺ and Rh⁰, especially Rh⁰. The fact that doubly Mn- and Fe-promoted Rh/γ-Al₂O₃ owned more (Rhx⁰–Rhy⁺)–O–Fe³⁺·(Fe²⁺) active species was proposed to be a crucial factor accounting for its higher ethanol selectivity.     

Hydrogen production by methanol steam reforming on a cordierite monolith reactor coated with Cu–Ni/LaZnAlO<Subscript>4</Subscript> and Cu–Ni/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The performance of Cu–Ni/LaZnAlO₄ and Cu–Ni/γ-Al₂O₃ catalysts in the methanol reforming process in a monolith reactor in the temperature range of 200–350 °C, feed flow rate of WHSV = 20.8 h^?1 and atmospheric pressure has been investigated. In order to perform a more thorough investigation, surface area, morphology and crystalline structure of the synthetic catalysts have been studied using BET, FE-SEM, TPR, FT-IR, TEM, TGA and XRD analyses. The results have shown that Cu–Ni/LaZnAlO₄ catalyst synthesized by combustion reaction method under ultrasound irradiation has a very high efficiency and catalytic activity, low reduction temperature, high mechanical resistance and large pore sizes. The latter causes a higher percentage of active metal impregnation and better distribution on the support, greater resistance against sintering and maintenance of catalyst inertness at temperatures over 1000 °C, in comparison with conventional catalysts such as Cu–Ni/γ-Al₂O₃. This make its substitution for currently used catalysts affordable.     

Promotion effect of nickel for Cu–Ni/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts in the transfer dehydrogenation of primary aliphatic alcohols

Cu–Ni/γ-Al₂O₃ bimetallic catalysts were developed for anaerobic dehydrogenation of non-activated primary aliphatic alcohols to aldehydes. Systematic investigation about the promotion effect of nickel on the catalytic performance was carried out. Hydrogenation of C=C bond rather than C=O bond, was significantly improved over Cu–Ni/γ-Al₂O₃ catalyst by introducing nickel, which interprets the good conversion of primary aliphatic alcohols. This work would contribute to design new catalysts for dehydrogenation of primary aliphatic alcohols.     

Upgrading of palm biodiesel fuel over supported palladium catalysts

Partial hydrogenation of palm biodiesel fuel (BDF) over 0.5wt%Pd/SBA-15 and 0.5wt%Pd/Zr-SBA-15 catalysts was examined by using a continuous fixed-bed reactor at 100 °C and 0.3 MPa under an atmosphere of H₂, in comparison to the commercial 0.5wt%Pd/γ-Al₂O₃ catalyst. The results showed that the 0.5wt%Pd/SBA-15 catalyst with high Pd dispersion and fast molecular diffusion through the short channeling pores gave the highest activity and selectivity in partial hydrogenation of polyunsaturated fatty acid methyl esters (FAME) as unstable components of palm BDF into cis-mono-unsaturated FAME as a target component of upgraded palm BDF with excellent oxidation stability and cold flow properties, which makes the addition of antioxidants unnecessary. By contrast, the 0.5wt%Pd/Zr-SBA-15 catalyst with strongly and moderately acidic sites gave low selectivity toward cis-mono-unsaturated FAME. The commercial 0.5wt%Pd/γ-Al₂O₃ catalyst displayed much lower polyunsaturated FAME conversion and cis-mono-unsaturated FAME selectivity, associated with poor Pd dispersion and slow molecular diffusion through the disordered pores.     

Comparative Study of the Support Role on the Activity of Copper Species for Nitric Oxide Reduction

In this work three different supports (γ-Al₂O₃, ZSM-5, and SAPO-34) of varying degree of acid sites and textural properties were used to evaluate the influence of support specifics in the Cu/supported nanocatalysts on NO conversion. The nanocatalysts were prepared by homogeneous deposition precipitation (HDP) method and characterized by N₂ pore size distribution, TEM, H₂-TPR for investigation the reducibility of the copper species and acidity measurement by NH₃ adsorption. The Cu/ZSM-5 and Cu/SAPO-34 catalysts were more active for NO conversion than Cu/γ-Al₂O₃ catalyst. The characterization and conversion differences in the copper supported on different types of support indicated that these differences arise from the differences in surface area, pore size distribution, and acidity of the supports. The higher SCR-DeNO activity of Cu/ZSM-5 and Cu/SAPO-34 nano-catalysts can be explained by higher surface area and acidity of ZSM-5 and SAPO-34 supports. These catalysts also have larger amount of reducible Cu species compared to Cu/γ-Al₂O₃ which correlates with the structure of the support used. Considering these findings, the NO conversion ability of Cu/supported catalysts has been correlated with support structure and acidity.     

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.     

A theoretical and experimental XAS study of monolayer dispersive supported CuO/γ-Al2O3 catalysts

The local structures of supported CuO/γ-Al₂O₃ monolayer dispersive catalysts with different CuO loadings have been investigated by EXAFS and multiple scattering XANES simulations. The EXAFS results show that the first nearest neighbors around the Cu atoms in the CuO/γ-Al₂O₃ catalysts are similar to that of the polycrystalline CuO powder, which is independent of the CuO loadings. Moreover, the Cu K-XANES FEFF8 calculations for CuO reveal that the monolayer-dispersed CuO species are of small distorted (CuO₄)_mⁿ⁺ clusters, which is mainly composed of a distorted CuO₆ octahedron incorporated in the surface octahedral vacant sites of the γ-Al₂O₃ support. We consider that the CuO species for the CuO/γ-Al₂O₃ catalysts with loadings of 0.4 and 0.8 mmol/100 m² are distorted (CuO₄)_mⁿ⁺ clusters composed mainly of a distorted CuO₆ octahedron incorporated in the surface octahedral vacant sites of the γ-Al₂O₃ support after calcinations at high temperature in air for a few hours. On the contrary, for the CuO/γ-Al₂O₃ with loading of 1.2 mmol/100 m², the local structure of Cu atoms in CuO/γ-Al₂O₃ is similar to that of polycrystalline CuO powder.     

Mo_2C/γ-Al_2O_3催化剂上苯加氢反应的原位红外光谱研究

采用程序升温反应法制备了钝化态、还原钝化态和新鲜态Mo2C/γ-Al2O3催化剂,结合原位红外光谱表征技术和反应性能评价,考察、比较了三种催化剂苯加氢反应活性.原位红外光谱结果表明,新鲜态Mo2C/γ-Al2O3催化剂在室温就显示了较好的苯加氢反应活性,表现了类贵金属的催化活性.CO吸附在反应前后新鲜态Mo2C/γ-Al2O3催化剂上的对比结果表明,低价态的Mo位(Moδ+(0δ2))是苯加氢反应活性中心.三种催化剂的反应活性结果表明,新鲜态Mo2C/γ-Al2O3催化剂反应活性最好,催化剂寿命最长,失活之后在500°C下H2处理即可恢复原有活性.     

Highly Selective Pd–Cu/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for Liquid-Phase Hydrogenation: The Influence of the Pd: Cu Ratio on the Structure and Catalytic Characteristics

The structure and catalytic characteristics of a series of Pd–Cu/α-Al₂O₃ catalysts with Pd: Cu ratio varied from Pd₁–Cu_0.5 to Pd₁–Cu₄ were studied. The use of α-Al₂O₃ with a small surface area (S_sp = 8 m²/g) as a support made it possible to minimize the effect of diffusion on the catalytic characteristics and to study the structure of Pd–Cu nanoparticles by X-ray diffraction (XRD) analysis. The XRD analysis and transmission electron microscopy (TEM) data indicated the formation of uniform bimetallic Pd–Cu nanoparticles (d = 20–60 nm), whose composition corresponded to a ratio between the metals in the catalyst, and also the absence of monometallic Pd⁰ and Cu⁰ nanoparticles. The study of catalytic properties in the liquid-phase hydrogenation of diphenylacetylene (DPA) showed that the activity of the catalysts rapidly decreased with the Cu content increase; however, in this case, the yield of a desired alkene compound significantly increased. The selectivity of alkene formation on the catalysts with the ratios Pd: Cu = 1: 3 and 1: 4 was superior to the commercial Lindlar catalyst.     

Structural Properties of Ni/γ−Al2O3 and Cu/γ−Al2O3 Catalyst and its Application for Hydrogenation of Furfurylidene Acetone

Hydrogenation of furfurylidene acetone has been carried out using Ni/γ−Al₂O₃ and Cu/γ−Al₂O₃ catalyst in the presence of isopropanol in autoclave batch reactor. The hydrogenation using Cu/γ−Al₂O₃ at 120^oC for 6 h gives main formation of 1,5-bis-(furan-2-yl)-pentan-3-one. Reaction at higher temperature at 140^oC for 8 h using Ni/γ−Al₂O₃ leads to 1,5-bis-(furan-2-yl)-penta-1-en-3-one. The different selectivity of both catalysts is explained by physical properties including the surface area and distribution of metal loading.     

炭载钌催化剂的微波制备及其水相乙酰丙酸加氢性能

生物质衍生物乙酰丙酸是生物质转化过程中重要的平台分子,对其进行催化加氢可以得到高附加值的产物,是连接生物质转化和石油化工的重要途径。本实验研究了无溶剂微波辅助热解法绿色制备负载型钌基催化剂,以Ru₃（CO）₁₂为金属前体,碳纳米管、椰壳活性炭和活性氧化铝为催化剂载体,该制备方法简单易操作,环保高效低能耗,不使用溶剂,避免了杂质的引入和对催化剂的污染,是一种新型负载型贵金属催化剂的制备方法。同样采取传统浸渍法制备Ru/γ-Al₂O₃-IM。在乙酰丙酸水相催化加氢反应中的催化活性顺序为Ru/AC > Ru/CNT ≈ Ru/FCNT > Ru/γ-Al₂O₃-MW ≈ Ru/γ-Al₂O₃-IM。比较不同反应溶液水、甲醇、乙醇、苯甲醚、环己烷和丙酮等对于乙酰丙酸催化加氢反应的影响,并通过考察反应温度、反应压力和反应物初始浓度等因素对加氢反应的影响,确定最佳实验条件为：反应温度为90℃,反应压力2.0 MPa,适宜反应物浓度为0.10 g/mL,产品GVL收率大于99%。     

Cerium-containing catalysts for converting ethanol into ethylene

Ce/γ-Al₂O₃ and CeLa/γ-Al₂O₃ catalysts are studied via electron microscopy and temperature-programmed desorption of ammonia. Their activity in the dehydration of ethanol is investigated. Doping Ce/γ-Al₂O₃ catalyst with lanthanum is shown to increase its dispersion and the number of active acid sites, thereby improving its activity.     

Catalytic properties of nanostructured Pd–Ag catalysts in the liquid-phase hydrogenation of terminal and internal alkynes

A comparative catalytic study of Pd–Ag bimetallic catalysts and the commercial Lindlar catalyst (Pd–Pb/CaCO₃) has been carried out in the hydrogenation of phenylacetylene (PA) and diphenylacetylene (DPA). The Pd–Ag catalysts have been prepared using the heterobimetallic complex PdAg₂(OAc)₄(HOAc)₄ supported on MgAl₂O₄ and aluminas (α-Al₂O₃ and γ-Al₂O₃). Physicochemical studies have demonstrated that the reduction of supported Pd–Ag complex with hydrogen results in homogeneous Pd–Ag nanoparticles. Equal in selectivity to the Lindlar catalyst, the Pd–Ag catalysts are more active in DPA hydrogenation. The synthesized Pd–Ag catalysts are active and selective in PA hydrogenation as well, but the unfavorable ratio of the rates of the first and second stages of the process makes it difficult to kinetically control the reaction. The most promising results have been obtained for the Pd–Ag₂/α-Al₂O₃ catalyst. Although this catalyst is less active, it is very selective and allows efficient kinetic control of the process to be carried out owing to the fact that, with this catalyst, the rate of hydrogenation of the resulting styrene is much lower than the rate of hydrogenation of the initial PA.     

Intermetallic Pd<Subscript>1</Subscript>–Zn<Subscript>1</Subscript> nanoparticles in the selective liquid-phase hydrogenation of substituted alkynes

A comparative study of the catalytic characteristics of monometallic Pd/α-Al₂O₃ and bimetallic Pd–Zn/α-Al₂O₃catalysts in the liquid-phase hydrogenation of structurally different substituted alkynes (terminal and internal, symmetrical and asymmetrical) was carried out. It was established that an increase in the reduction temperature from 200 to 400 and 600°C led to a primary decrease in the activity of Pd–Zn/α-Al₂O₃ due to the formation and agglomeration of Pd1–Zn1 intermetallic nanoparticles. The Pd–Zn/α-Al₂O₃ catalyst containing Pd1–Zn1 nanoparticles exhibited increased selectivity to the target alkene formation, as compared with that of Pd/α-Al₂O₃. Furthermore, the use of the Pd–Zn/α-Al₂O₃ catalyst made it possible to more effectively perform the kinetic process control of hydrogenation because the rate of an undesirable complete hydrogenation stage decreased on this catalyst.     

Methane conversion under cold plasma over Pd-containing ionic liquids immobilized on γ-Al2O3

Pd-containing ionic liquid (IL) l-hexyl-3-methylimidazolium tetrafluoroborate (C₆MIMBF₄) immobilized on γ-Al₂O₃ (Pd-IL/γ-Al₂O₃) was prepared and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The influences of C₆MIMBF₄ loading and Pd on methane conversion to C₂ hydrocarbons under cold plasma were investigated. FTIR and SEM analyses indicated that C₆MIMBF₄ had been successfully immobilized on γ-Al₂O₃ and the C₆MIMBF₄ showed excellent stability under cold plasma. The results of BET and methane conversion showed that with the increase in immobilization amount of C₆MIMBF₄ onto γ-Al₂O₃, the specific surface area and pore volume of IL/γ-Al₂O₃ decreased, while the selectivity and yield of C₂ hydrocarbons increased. The selectivity of C₂ hydrocarbons was 94.6% when the loading of C₆MIMBF₄ was 40%, and the percentage of C₂H₄ in C₂ hydrocarbons was as high as 64% when using Pd-IL/γ-Al₂O₃ as a catalyst with no conventional thermal reduction treatment. Optical emission spectra (OES) from the cold plasma reactor during methane conversion were also studied. The results indicated that the intensity of the C₂, CH, H, and C active species from methane and hydrogen decomposition increased when IL/γ-Al₂O₃ or Pd-IL/γ-Al₂O₃ was introduced into the plasma system. Based on the analyses of the gas product and OES spectra, it can be concluded that the surface catalyzed reactions between plasma and ionic liquid were very important for the reduction of Pd²⁺ and the formation of C₂H₄     

Study on biomass catalytic pyrolysis for production of bio-gasoline by on-line FTIR

The pyrolysis of biomass is a promising way for production of bio-gasoline if the stability and quality problems of the bio-crude-oil can be solved by catalytic cracking and reforming.In this paper,an on-line infrared spectrum was used to study thecharacteristics of catalytic pyrolysis with the following preliminary results.The removal of C O of organic acid is more difficultthan that of aldehydes and ketones.HUSY/γ-Al_2O_3 and REY/γ-Al_2O_3 catalysts exhibited better deoxygenating activities whileHZSM-5/γ-Al_2O_3 catalyst exhibited preferred selectivities for production of iso-alkanes and aromatics.Finally,possiblemechanisms of biomass catalytic pyrolysis are discussed as well.     

Enhancement of the catalytic performances and lifetime of Ni/γ-Al2O3 catalysts for the steam toluene reforming via the combination of dopants: inspection of Cu,Co, Fe,Mn, and Mo species addition

In this work, the influence of metallic dopant addition in 10 wt % Ni/γ-Al₂O₃ catalyst on the material physico-chemical properties and catalytic activity for the toluene steam reforming was studied. Seventeen doped Ni/γ-Al₂O₃ catalysts were synthesized by the sol–gel process. The aim of this study was to determine which elements were the most suitable for the doping of 10 wt % Ni/γ-Al₂O₃ catalysts. The influence of the dopants was studied through different physico-chemical techniques. It appeared that some dopants showed lower catalytic performances due to high carbon deactivation. On the contrary, some dopants increased the resistance to coking while also improving the catalytic activity. Different mechanisms were proposed to explain these modifications of catalytic behavior. Among all doped Ni/γ-Al₂O₃ catalysts, the samples that combined Mn + Mo or Co + Mo dopants showed the best catalytic performances at 650 °C. Both samples showed high toluene reforming activity and low amounts of carbon deposit.     

La2O3 promotional effect to Co3O4/γ-Al2O3 catalyst in the oxidative dehydrogenation of ethylbenzene with CO2 as soft oxidant

Co₃O₄/γ-Al₂O₃ catalysts with variable Co₃O₄ loadings (5–20 wt%) and deposition of 15% Co₃O₄ on La₂O₃/γ-Al₂O₃ were prepared by wet impregnation method. La₂O₃-γ-Al₂O₃ support with variable composition of La₂O₃ (2–6 wt%) were prepared by co-precipitation method. All the catalysts were tested for oxidative dehydrogenation of ethylbenzene with CO₂ as soft oxidant. Among the Co₃O₄/γ-Al₂O₃ catalysts, 15% Co₃O₄/γ-Al₂O₃ has shown good performance and hence this catalyst has been chosen to investigate the effect of La₂O₃ species. CO₂ pulse chemisorption data indicate more amount of CO₂ uptake over 15% Co₃O₄/4%La₂O₃/γ-Al₂O₃ catalyst which clearly indicates that this catalyst exhibits good performance in ethylbenzene dehydrogenation with CO₂ as soft oxidant because of reverse water gas shift reaction. Temperature programmed reduction studies indicate that the Co₃O₄ catalysts follow two step reduction mechanism from Co₃O₄ to CoO and then to Co and La₂O₃ promotional effect is visible through facile reduction of Co₃O₄ species. La₂O₃ doping has a vital influence in getting enhanced ethylbenzene conversion, styrene yield and alleviates catalyst deactivation compared to that of unpromoted Co₃O₄/γ-Al₂O₃ catalyst. TGA studies indicate the presence low amount coke deposition during time-on-stream over 15% Co₃O₄/4%La₂O₃/γ-Al₂O₃ catalyst compared to 15% Co₃O₄/γ-Al₂O₃ catalyst.