Chemo-bio catalyzed synthesis of <Emphasis Type="Italic">R</Emphasis>-1-phenylethyl acetate over bimetallic PdZn catalysts,lipase, and Ru/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>. part I

One-pot synthesis of R-1-phenyethylacetate at 70°C was investigated using three different catalysts simultaneously, namely a bimetallic PdZn/Al₂O₃ as a hydrogenation catalyst, an immobilized lipase as an acylation catalyst and Ru/Al₂O₃ as a racemization catalyst. The most active bimetallic catalyst was PdZn/Al₂O₃ calcined at 300°C and reduced at 400°C, whereas the most selective although less active catalyst was the one being calcined and reduced at 500°C. The highest selectivity to R-1-phenylethyl acetate over this catalyst was 32 at 48% conversion. Ru/Al₂O₃ was confirmed to have a positive effect on the formation of the desired product, although it was not very active in the racemization during one-pot synthesis.     

Effect of the Electric Conductivity of a Catalyst on Methane Activation in a Dielectric Barrier Discharge Reactor

The influence of catalyst electric conductivity on methane activation in a planar-type dielectric barrier discharge reactor is investigated by empirically comparing the degree of methane conversion of bare Al₂O₃ with that of Pt/Al₂O₃; from this, it is determined that the latter catalyst converts less methane owing to the presence of Pt. Calculations and comparisons of electric fields with and without Pt show that the presence of a Pt catalyst results in a lower electric field than does bare Al₂O₃. An analysis of product gases based on the correlation between the fragmentation of radicals and the electric field also indicates that the electric field is decreased by using Pt. From these results, it can be concluded that the synergies between the plasma and the conductive catalysts need to be reassessed for different electric field conditions, and that further studies of non-conductive catalysts that can enhance methane activation and synergistic effects are needed.     

Mechanism of the chemo–bio catalyzed cascade synthesis of <Emphasis Type="Italic">R</Emphasis>-1-phenylethyl acetate over Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>, lipase,and Ru-catalysts

One-pot synthesis of R-1-phenylethyl acetate was investigated starting from acetophenone hydrogenation performed over Pd/Al₂O₃ and PdZn/Al₂O₃ catalysts followed by acylation of the intermediate secondary alcohol, R-1-phenylethanol, over an immobilized lipase. Furthermore, the performance of a third type of catalyst, Ru supported on hydroxyapatite (HAP) was evaluated for racemization of S-1-phenylethanol in one pot together with the two other catalysts. The main objectives of this work were to separate the effects of different catalysts and to reveal the reaction mechanism. For this purpose not only acetophenone, but also (R,S)-1-phenylethanol, S-1-phenylethanol, R-1-phenylethyl acetate, and styrene were used as reactants in combination with Pd/Al₂O₃, lipase and Ru/HAP as catalysts. The results revealed that the main side product, ethylbenzene, was formed in two different ways, via dehydration of (R,S)-1-phenylethanol to styrene, followed by its rapid hydrogenation to ethylbenzene, and via debenzylation of the desired product, R-1-phenylethyl acetate to ethylbenzene. The true one-pot synthesis, however, was demonstrated over Shvo’s catalyst, but Ru/HAP was not sufficiently active in the racemization step. Ru/Al₂O₃ was a promising catalyst for racemization of S-1-phenylethanol and for dynamic kinetic resolution of (R,S)-1-phenylethanol, when using only small amounts of the acyl donor ethyl acetate. The challenge in racemization is that the activity of heterogeneous Ru catalysts was inhibited by esters.     

Selective Hydrogenation of Acetylene and Physicochemical Properties of Pd–Fe/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Bimetallic Catalysts

The selective hydrogenation of acetylene on Pd–Fe/Al₂O₃ catalysts prepared by decomposition of ferrocene on reduced Pd/Al₂O₃ was studied. The effect of the conditions of treatment of the Pd–ferrocene/ Al₂O₃ precursor on the catalyst activity and selectivity was investigated, and the optimum conditions were determined at which the Pd–Fe/Al₂O₃ catalyst has higher selectivity than Pd/Al₂O₃ without any loss of activity.     

Chemo-bio catalyzed synthesis of <Emphasis Type="Italic">R</Emphasis>-1-phenylethyl acetate over bimetallic PdZn catalysts,lipase, and Ru/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>. Part II

One-pot synthesis of R-1-phenyethylacetate at 70°C was investigated using three different catalysts simultaneously, namely a bimetallic PdZn/Al₂O₃ as a hydrogenation catalyst, an immobilized lipase as an acylation catalyst and Ru/Al₂O₃ as a racemization catalyst. The most active bimetallic catalyst was PdZn/Al₂O₃ calcined at 300°C and reduced at 400°C, whereas the most selective although less active catalyst was the one being calcined and reduced at 500°C. The highest selectivity to R-1-phenylethyl acetate over this catalyst was 32 at 48% conversion. Ru/Al₂O₃ was confirmed to have a positive effect on the formation of the desired product, although it was not very active in the racemization during one-pot synthesis.     

Carbon Dioxide Reforming of Methane over Ni Catalysts Supported on Al2O3 Modified with La2O3, MgO, and CaO

The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present review mainly focuses on CDR to produce synthesis gas over Ni/MO_x/Al₂O₃ (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La₂O₃, MgO, and CaO have been found. The addition of promoters to Al₂O₃-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent on the loading amount of promoters. For example, the highest CH₄ and CO₂ conversion were obtained when the ratios of metal M to Al were in the range of 0.04–0.06. In the case of Ni/La₂O₃/Al₂O₃ catalyst, the highest CH₄ conversion (96%) and CO₂ conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al₂O₃ catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH₄ conversion (91%) and CO₂ conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al₂O₃ catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH₄ conversion (89%) and CO₂ conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic performance of Al₂O₃-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization of metal oxide on Al₂O₃ and the basic property of metal oxide to prevent carbon formation.     

Fischer–Tropsch synthesis: evaluation of Gd and Ru promoters effect on Co/<Emphasis Type="Italic">γ</Emphasis>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst at different conditions

In this study, the effect of Ru and Gd promoters on 15Co/\(\gamma\)-Al₂O₃ catalyst in the Fischer–Tropsch synthesis is investigated. The catalysts were synthesized by dry impregnation method and characterized by XRD, adsorption/desorption of nitrogen, TPR, TEM, ICP and XPS analyses. Activity and selectivity of the catalysts were examined in a fixed bed reactor at 210–230 °C with a H₂/CO ratio of 2 and atmospheric pressure. The results showed that the Ru-promoted catalyst has the highest activity and methane selectivity which reduce the chain growth probability. The Gd-promoted catalyst was shown smaller particle size and higher dispersion of cobalt particles in compared with unpromoted catalyst. The smaller particles have more interaction and thus show the lower catalyst reducibility. The presence of Gd in the catalyst cause higher chain growth probability compared to the unpromoted one. The Ru–Gd-promoted catalysts were shown a synergic effect in the catalyst reducibility. Based on the screening of the catalysts in the atmospheric pressure; the unpromoted, 0.1Ru/15Co/Al₂O₃, and 0.1Ru1Gd/15Co/Al₂O₃ catalysts were selected to test at high pressure conditions, which the 0.1Ru1Gd/15Co catalyst showed the highest C₅ ⁺ selectivity (75%) compared with the 0.1Ru/15Co/Al₂O₃ and the unpromoted one.     

Hydrogen Production by Steam Reforming of Ethanol Over Mesoporous Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZrO<Subscript>2</Subscript> Catalysts

This review paper reports the recent progress concerning the application of nickel–alumina–zirconia based catalysts to the ethanol steam reforming for hydrogen production. Several series of mesoporous nickel–alumina–zirconia based catalysts were prepared by an epoxide-initiated sol–gel method. The first series comprised Ni–Al₂O₃–ZrO₂ xerogel catalysts with diverse Zr/Al molar ratios. Chemical species maintained a well-dispersed state, while catalyst acidity decreased with increasing Zr/Al molar ratio. An optimal amount of Zr (Zr/Al molar ratio of 0.2) was required to achieve the highest hydrogen yield. In the second series, Ni–Al₂O₃–ZrO₂ xerogel catalysts with different Ni content were examined. Reducibility and nickel surface area of the catalysts could be modulated by changing nickel content. Ni–Al₂O₃–ZrO₂ catalyst with 15 wt% of nickel content showed the highest nickel surface area and the best catalytic performance. In the catalysts where copper was introduced as an additive (Cu–Ni–Al₂O₃–ZrO₂), it was found that nickel dispersion, nickel surface area, and ethanol adsorption capacity were enhanced at an appropriate amount of copper introduction, leading to a promising catalytic activity. Ni–Sr–Al₂O₃–ZrO₂ catalysts prepared by changing drying method were tested as well. Textural properties of Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst produced from supercritical drying were enhanced when compared to those of xerogel catalyst produced from conventional drying. Nickel dispersion and nickel surface area were higher on Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst, which led to higher hydrogen yield and catalyst stability over Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst.     

柠檬酸添加方式对Mo-Ni-P/Al_2O_3催化剂加氢活性的影响

以Mo、Ni为活性组分,Al_2O_3为载体,采用不同柠檬酸添加方法制备了Mo-Ni-P/Al_2O_3催化剂.通过氢气程序升温还原(H2-TPR)、X射线衍射(XRD),透射扫描电镜(TEM)、XPS等表征方法研究催化剂的物化性质.结果表明:催化剂经柠檬酸的后处理,改善了载体氧化铝表面羟基基团的分布,促使Mo物种以八面体配位多核聚钼酸的形态存在,有效地减弱了载体与活性金属之间的强相互作用,提高了Mo物种的分散度与硫化度,使得催化剂形成更多"Mo-Ni-S"加氢活性相,提高了催化剂的加氢活性.与其他处理方法相比,柠檬酸后处理的催化剂对VGO具有更高的加氢脱硫、脱氮与芳烃饱和性能.     

Co-K and Mo-K edges Quick-XAS study of the sulphidation properties of Mo/Al2O3 and CoMo/Al2O3 catalysts

The sulphidation process of two catalysts (Mo/Al₂O₃ and CoMo/Al₂O₃) has been investigated by time-resolved X-ray Absorption Spectroscopy. With the unique edge jumping capability available at the SOLEIL synchrotron, studies of cobalt and molybdenum species have been conducted simultaneously on the same bimetallic catalyst. A methodology combining Principal Component Analysis and Multivariate Curve Resolution with Alternating Least Squares methods unravels a 3-stepped or 4-stepped sulphidation process for the bimetallic and monometallic catalysts, respectively. An oxysulphide-based molybdenum species has been identified as an intermediate for Mo/Al₂O₃ and a MoS₃-like species has been observed for both catalysts.     

Effect of preparation method on structural characteristics and propane steam reforming performance of Ni–Al2O3 catalysts

Propane steam reforming was studied over Ni–Al₂O₃ catalysts that were prepared by a conventional impregnation (IM) method and a one-step sol–gel (SG) technique. Both Ni–Al₂O₃ catalysts showed similar initial activity. However, IM-Ni–Al₂O₃ deactivated severely with time-on-stream of propane steam reforming. The catalyst prepared using a SG technique demonstrated stable catalytic performance. The two catalysts also showed major differences in product distribution, with SG catalyst giving much higher yields of hydrogen. Catalysts were characterized with temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), temperature-programmed oxidation (TPO), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. It was revealed that, with sol–gel preparation, highly dispersed small Ni crystallites are formed with a strong interaction with the support. This is shown to be important for coke suppression and catalyst stability.     

Gold catalysts supported on ZnO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for low-temperature CO oxidation

Gold catalysts with loadings ranging from 0.5 to 7.0 wt% on a ZnO/Al₂O₃ support were prepared by the deposition–precipitation method (Au/ZnO/Al₂O₃) with ammonium bicarbonate as the precipitation agent and were evaluated for performance in CO oxidation. These catalysts were characterized by inductively coupled plasma-atom emission spectrometry, temperature programmed reduction, and scanning transmission electron microscopy. The catalytic activity for CO oxidation was measured using a flow reactor under atmospheric pressure. Catalytic activity was found to be strongly dependent on the reduction property of oxygen adsorbed on the gold surface, which related to gold particle size. Higher catalytic activity was found when the gold particles had an average diameter of 3–5 nm; in this range, gold catalysts were more active than the Pt/ZnO/Al₂O₃ catalyst in CO oxidation. Au/ZnO/Al₂O₃ catalyst with small amount of ZnO is more active than Au/Al₂O₃ catalyst due to higher dispersion of gold particles.     

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.     

Steam reforming of ethylene glycol over Ni-based catalysts: the effect of K

The effect of K on the activities of Ni/Al₂O₃ catalysts in steam reforming of ethylene glycol was investigated. Ni/Al₂O₃ catalysts were prepared by incipient wetness impregnation and co-precipitation methods. The addition of K was achieved using an incipient wetness impregnation method. The prepared catalysts were characterized by N₂ physisorption, inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. Irrespective of the preparation method, the promotional effect of K was observed and the optimum K content (~5 wt%) was verified for K-promoted Ni/Al₂O₃ catalysts. The addition of K to the Ni–Al₂O₃ catalyst prepared by co-precipitation led to higher catalytic activity than addition of K to the Ni/Al₂O₃ catalyst prepared by incipient wetness impregnation.     

Ethylcyclopentane ring opening reaction over PtGe/Al2O3 catalysts prepared by controlled surface reaction

Platinum-germanium catalysts supported on a non-acidic Al₂O₃ have been prepared by adding Ge in amounts corresponding nominally to 1/8 (PtGe1/8/Al₂O₃); 1/2 (PtGe1/2/Al₂O₃); 1 (PtGe1/Al₂O₃) and 2 (PtGe2/Al₂O₃) monolayers by controlled surface reaction of Ge(n-C₄H₉)₄ to Pt/Al₂O₃. These catalysts were characterized by electron microscopy (TEM), FTIR of CO adsorption and H₂ chemisorption. The ring opening of ethylcyclopentane (ECP) was studied as a test reaction between 543 and 633 K. PtGe1/8/Al₂O₃ catalyst produced the most ring opening products (ROP) in the whole temperature range. A good agreement with statistical values of ROP was observed at low temperature, but at higher temperature, the opening became selective, producing mostly heptane. Bimetallic catalysts PtGe1/Al₂O₃ and PtGe2/Al₂O₃ led to a nonselective hydrogenolysis, similar to the monometallic platinum catalyst Pt/Al₂O₃. The catalysts PtGe1/Al₂O₃ and PtGe2/Al₂O₃ produced ROP with the lowest selectivity; instead, much aromatics and fragments were formed, in increasing amounts above 600 K.     

不同载体Ni基负载型催化剂对甲烷部分氧化制合成气催化行为研究

采用浸渍法制备了单一载体(Al₂O₃、ZrO₂、CeO₂)和ZrO₂、CeO₂改性的Al₂O₃复合载体的Ni催化剂,考察了在甲烷部分氧化制备合成气反应中的催化性能。通过N₂-物理吸附、H₂程序升温还原、X射线衍射、NH₃程序升温脱附和程序升温氧化等技术对催化剂进行了表征。结果表明,在单一载体催化剂中,Ni/Al₂O₃具有较大的比表面积,其初始反应活性较高,但该催化剂表面易形成大量的积炭而快速失活。Ni/ZrO₂和Ni/CeO₂催化剂比表面积较小,活性金属Ni在其表面分散性差,催化剂具有较低的CH₄转化率。而CeO₂和ZrO₂改性的Al₂O₃复合载体催化剂,具有较大的比表面积,反应活性明显高于单一载体催化剂。CeO₂-Al₂O₃复合载体催化剂具有最高的反应活性和较好的反应稳定性。同时表明,含CeO₂催化剂反应后表面积炭较少,CeO₂的储放氧功能增强了催化剂对O₂的活化,提高催化剂活性的同时,可以抑制积炭的生成。     

Plasma treatment of Ni and Pt catalysts for partial oxidation of methane

Summary In this work DBD (dielectric barrier discharge) plasma treatments of 10%Ni/Al₂O₃and 1%Pt/Al₂O₃catalysts have been conducted to study the principles of plasma treatment of supported catalysts. It was found that 10%Ni/Al₂O₃and 1%Pt/Al₂O₃catalysts treated by plasma exhibit a higher catalytic activity and a better stability than the catalysts prepared without plasma treatment. Methane conversion over the plasma treated catalyst is 3-5% higher than on untreated catalysts. The metal species dispersion also increased after plasma treatment, which leads to improvement of the interaction between active species and supports, the catalytic activities and the resistance to carbon deposition.</o:p>     

Direct Oxidation of Methane to Methanol Over Cu-Based Catalyst in an AC Dielectric Barrier Discharge

In this paper, the conversion of methane to methanol on CuO/Al₂O₃ and Mo–CuO/Al₂O₃ catalysts in a plasma reactor was tested. A comparison between catalytic and plasma-catalytic systems had been made in tested temperature range of 50–300°C. Experimental results showed that plasma-catalytic system demonstrated a much better methane conversion than catalytic system in tested temperature range and Mo–CuO/Al₂O₃ revealed a higher catalytic activity than CuO/Al₂O₃ for methanol synthesis. Furthermore, an Arrhenius plot was made in order to deduce the mechanism of plasma activation, which revealed that the presence of plasma decreased the activation energy for both catalysts. In the case of Mo-CuO/Al₂O₃ catalyst, the enhanced activity for methanol synthesis was assumed due to the oxygen vacancies on Mo–CuO/Al₂O₃ catalyst, which can utilize plasma-induced species to improve the catalytic efficiency.     

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.     

Effect of ultra-fine gold particle addition to metal oxides in ethylene oxidation

Oxidation of ethylene was carried out over alumina-supported metal oxide catalysts and highly dispersed gold catalysts, respectively, under atmospheric pressure. The ethylene was completely oxidized to produce carbon dioxide and water with both metal oxide and gold catalysts. The activity of gold catalyst prepared by deposition method was much higher than that of supported metal oxide catalysts. Ultra-fine gold particles on Co₃O₄ were more active than on Al₂O₃. Fe₂O₃/Al₂O₃ and MnO₂/Al₂O₃ catalysts were more active than MoO₃/Al₂O₃ catalyst. The activity of the supported metal oxide catalysts was greatly enhanced by addition of gold particles. It was therefore considered that gold particles promote dissociative adsorption of oxygen and the adsorbed oxygen reacts with adsorbed ethylene on support adjacent to the active site.