Selective CO removal in a H2-rich stream over supported Ru catalysts for the polymer electrolyte membrane fuel cell (PEMFC)

We prepared various Ru catalysts supported on different supports such as yttria-stabilized zirconia (YSZ), ZrO₂, TiO₂, SiO₂ and γ-Al₂O₃ with a wet impregnation method. We applied them to the selective CO removal in a hydrogen-rich stream via the preferential CO oxidation (PROX) and the selective CO methanation simultaneously. Among them, Ru/YSZ showed the highest CO conversion especially at low temperatures. Several measurements: the N₂ physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), the CO chemisorptions, the temperature-programmed oxidation (TPO), the temperature-programmed reduction (TPR), the temperature-programmed desorption (TPD) of CO₂ with mass spectroscopy and the transmission electron microscopy (TEM), were conducted to characterize the catalysts. No linear correlation can be found between the amount of CO chemisorbed at 300 K and the PROX activity. On the other hand, the facile activation of O₂ appeared to be closely related to the high PROX activity, judging by the TPO experiment. In addition, the strong adsorption of CO₂ suppressed the low-temperature PROX activity. Ru/YSZ can be easily oxidized and also reduced at low temperatures. It is found that Ru/YSZ uptakes only small amounts of CO₂, which can be desorbed at low temperatures. Ru/YSZ can reduce the high inlet CO concentration to be less than 10 ppm even in the presence of H₂O and CO₂.     

Mesoporous Co-Al oxide nanosheets as highly efficient catalysts for CO oxidation

We report mesoporous Co-Al oxide nanosheets (Co_xAl-Ns, where x denotes the Co/Al ratio in the samples) prepared by calcination of CoAl-hydrotalcite and subsequent alkaline treatment. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy measurements show that the prepared Co-Al oxide nanosheets (Co_xAl-Ns) are very thin (10–15 nm) and exhibit high mesoporosity (3–5 nm). Catalytic CO oxidation tests reveal that the Co_xAl-Ns exhibit excellent catalytic performances at relatively low temperatures: for example, the Co_2.5Al-Ns catalyst could achieve 99% CO conversion at −98°C. Kinetic studies and experimental investigations indicate that the high activity of the Co_2.5Al-Ns sample is strongly related to the abundance of active sites associated with the large Brunauer–Emmett–Teller surface area. The Co_2.5Al-Ns catalyst also achieves full conversion of CO in tests performed with a gas mixture simulating automobile exhaust gas at 200°C. After loading the Co_2.5Al-Ns on a porous ceramic substrate, the obtained Co_2.5Al-Ns/PC shows high activity and stability in CO oxidation process. These features are potentially important for future industrial applications of these catalysts.     

双核金属卟啉仿酶催化剂的合成及催化氧化进展

综述了3类双核金属卟啉的合成方法：以共价柔性单键联接的开放型双卟啉的常用成熟合成方法;以共轭基团键联或直接键联的刚性双卟啉的系列交叉耦合等合成方法;μ-氧代双核金属卟啉的合成方法。主要介绍了μ-氧代双核金属卟啉和以柔韧烷氧链相连的双核金属卟啉作为仿酶催化剂在均相催化烷烃、烯烃等有机底物氧化方面的研究进展,并对这两类双核金属卟啉的催化机理、金属双核的协同催化作用机理作了论述,最后展望了双核金属卟啉仿酶催化剂的研究前景。     

Catalytic wet air oxidation of aqueous solution of 2-chlorophenol over Ru/zirconia catalysts

Ru loaded zirconia catalysts (Ru/ZrO₂) were found to be active in the catalytic wet air oxidation (CWAO) of 2-chlorophenol (2-CP) at relatively mild temperature. To optimize the reaction conditions, the effects of different operating parameters, such as the rotation speed, the reaction temperature, the total pressure, the initial concentration and the pH of the initial 2-CP solution on the catalytic activity of 3 wt.% Ru/ZrO₂ were evaluated. The activation energy for the CWAO of 2-CP over Ru/ZrO₂ was calculated to be 36 kJ mol⁻¹. The 2-CP removal rate is zero order with respect to the initial 2-CP concentration. The CWAO of 2-CP changes from first order (oxygen diffusion control) to zero order (kinetic control) with respect to the oxygen partial pressure when the total pressure is higher than 4 MPa. The conversion of 2-CP increases with the pH of the initial 2-CP solution. The dechlorination reaction is promoted at higher pH. However, too high pH limits the total mineralization of 2-CP because the adsorption of the reaction intermediates is hindered. It was also confirmed that Ru(NO)(NO₃)₃ is better than RuCl₃ to act as a ruthenium precursor.     

Gold catalysts for the direct oxidation of aminoalcohols to aminoacids

Gold catalysts on different supports, prepared by sol immobilization and deposition–precipitation, were tested in aminoalcohol oxidation for the direct preparation of aminoacids. Nitrogen substitution appeared to be crucial for avoiding parallel reaction pathway, but also the reaction conditions play an important role. Basic conditions and moderate temperature (40 °C) represent a good compromise for enhancing selectivity to aminoacids. TiO₂ represents the most versatile support.     

苯加氢烷基化合成环己基苯催化剂研究

以分子筛为载体,采用等体积浸渍法制备具有双功能的分子筛催化剂.以苯为原料,在双功能催化剂的作用下采用加氢烷基化的方法合成环己基苯(CHB).考察了不同载体酸性、反应温度、氢气压力和催化剂的金属担载量等因素对反应的影响.实验结果表明:Ru/Hβ双功能催化剂为最佳的催化剂,最佳反应条件为:2.5 MPa氢气压力,200℃下反应4h.在此条件下苯的转化率可达67.6％,CHB的选择性可达47.8％.催化剂的金属活性和酸性是苯加氢烷基化的关键.     

合成丙烯酸催化剂研究进展

对用于合成丙烯酸催化剂进行分类总结,综述丙烯氧化制丙烯酸催化剂和丙烷氧化制丙烯酸催化剂研究进展。丙烯两步氧化法制丙烯酸催化剂应用广泛,催化剂主要为Mo-Bi系和Mo-V系复合氧化物。提出扩大丙烯酸下游产品领域对调节产能扩张的重要性,提高国产丙烯酸催化剂性能、增强工业应用能力、降低生产成本、减少污染物排放和开发新型丙烯酸催化剂及其生产技术是下一步的研究重点。     

Mesoporous silica supported cobalt oxide catalysts for catalytic removal of benzene

Two types of mesoporous silica SBA-15 with different pore diameter were synthesized with an ageing temperature of 373 K and an ageing temperature of 308 K, respectively; in addition, mesoporous silica with amorphous structure was synthesized by adding organosiloxane as part of the silica source during the synthesis procedure. Mesoporous silica and conventional alumina supported cobalt oxide catalysts were prepared by incipient wetness impregnation method. These materials were characterized by FT-IR, nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Temperature programmed reduction (TPR) techniques, and the activity of the supported cobalt oxide catalysts for deep oxidation of benzene were evaluated in a fixed-bed reactor. It seems that the pore diameter of the silica increase with the elevation of the ageing temperature. Mesoporous silica supported cobalt oxide catalysts are more active than conventional alumina supported ones. Cobalt oxide can be relatively better dispersed on the surface of mesoporous silica which has larger pore diameter and surface areas. Meanwhile, more silanol groups exist on the surface of amorphous silica, which could induce a strong interaction with the supported cobalt oxide species, leading to poor activity for benzene oxidation.     

Novel dicopper(II)-tetracarboxylates as catalysts for selective oxidation of benzyl alcohols with aqueous TBHP

A few dicopper(II) tetracarboxylate complexes viz. [Cu₂(µ-O₂CC₆H₅)₄(4-Etpy)₂] (1), [Cu₂(µ-O₂CC₆H₅)₄(4-DMAP)₂] (2), [Cu₂(µ-O₂CC₆H₅)₄(4-CNpy)₂] (3) and [Cu₂(µ-O₂CCH₃)₄(4-CNpy)₂] (4) have been utilised as catalysts for oxidation of benzyl alcohols using aqueous tert-butyl hydroperoxide as the oxidant. Complexes 1 and 2 have shown better catalytic activity than the other two. Unlike other catalysts, these dicopper complexes can catalyse oxidation of alcohols at a very low concentration (0.5 mol%).     

杂原子MCM-41分子筛对过氧化氢液相氧化环己烷的研究

分别考察了反应温度、过氧化氢用量及加入方式等因素对Cr、Fe和Ce改性后的杂原子MCM-41分子筛催化剂液相催化氧化环己烷制取环己酮反应的影响。研究结果表明，Cr-MCM-41〖JP〗催化剂具有较好的催化活性。选择适当的反应温度、过氧化氢用量和加入方式可以有效提高环己烷转化率和过氧化氢利用率。在70 ℃和n(C₆ H₁₂)∶n(H₂O₂)=1∶2条件下，采用两次加入过氧化氢的方式，环己烷转化率为33.7％，酮醇总选择性97.2％，n(环己酮)∶n(环己醇）＝1.99，过氧化氢利用率37.1%。     

A new environmental friendly method for the preparation of sugar acids via catalytic oxidation on gold catalysts

A novel and efficient way of producing of aldonic acids is reported. The selective catalytic oxidation of monosaccharides (arabinose, ribose, xylose, lyxose, mannose, rhamnose, glucose, galactose, N-acetyl-glucosamine) and disaccharides (lactose, maltose, cellobiose, melibiose) on Au, Pd and Pt catalysts was investigated. By using the gold catalyst, a total selectivity with respect to aldonic acids and a high catalytic activity for all investigated sugars was found. The reaction conditions for the production of maltobionic and lactobionic acids via oxidation on gold catalysts were optimised. A high long-term stability of two different gold catalysts for the oxidation of maltose and lactose, respectively, was found.     

Mono (V, Nb) or bimetallic (V–Ti, Nb–Ti) ions modified MCM-41 catalysts: synthesis, characterization and catalysis in oxidation of hydrocarbons (aromatics and alcohols)

Mesoporous MCM-41 molecular sieves modified by single (V and Nb) or bimetal (Nb–Ti and V–Ti) ions with highly ordered hexagonal arrangement of their cylindrical channels were prepared by direct synthesis with two different silica sources (sodium silicate and TEOS) and characterized (as-synthesized samples and those used after reaction) by XRD, N₂ adsorption–desorption, TEM, SEM and FTIR techniques. Niobium and titanium were stabilized in the autoclavized gel by complexation with a ligand (acetylacetone and oxalic acid, respectively). V modified MCM-41 catalysts gave a very high activity in hydroxylation reaction of benzene and toluene and a low conversion in oxidation of styrene while Nb-modified MCM-41 samples showed very high conversion in oxidation of styrene but low oxidation conversion of benzene and toluene. Further introduction of titanium in V- and Nb-modified MCM-41 materials conducted to the less well-ordered hexagonal arrangement and gave very different effect on activity in oxidation of aromatics. Introduction of Ti into V-MCM-41 solids led to an increase in activity in oxidation of styrene and benzene but a decrease in conversion in oxidation of toluene. While the addition of Ti in Nb-MCM-41 resulted in a slight increase in conversion of styrene oxidation but a significant decrease in activity of benzene and toluene oxidation. It reveals that the introduction mode of oxidant in the reactors can also influence the activity and selectivity of reaction. An increase in reaction rate of oxidation, in the first 20 h, was obtained by introduction of H₂O₂ step by step during the reaction. The present paper evidenced that the side chain oxidation is main reaction of styrene oxidation while the hydroxylation is main reaction of benzene and toluene. That is why these two reactions need different catalytic centers as revealed by this paper. The oxidation of alcohols using V-modified MCM-41 as catalysts has also been explored and these catalysts showed a very low catalytic activity which increases in the order: hexanol相似文献   

Gold Nanoparticles Supported on the Periodic Mesoporous Organosilicas as Efficient and Reusable Catalyst for Room Temperature Aerobic Oxidation of Alcohols

Gold nanoparticles supported on the channels of a bifunctional periodic mesoporous organosilica, were found to be a highly efficient catalyst system for the aerobic oxidation of various types of alcohols into their corresponding aldehydes and ketones at room temperature. The catalyst showed no significant loss of efficiency for the aerobic oxidation of benzyl alcohol to give benzaldehyde after 7 reaction cycles.     

Performance of alumina-supported noble metal catalysts for the combustion of trichloroethene at dry and wet conditions

The performance of four different alumina-supported noble metal catalysts (0.5% of Pd, Pt, Rh and Ru, respectively) for the deep oxidation of trichloroethene (1000–2500 ppmV, WHSV = 55 h⁻¹) in air was studied in this work. Experiments were carried out at both dry and wet (20,000 ppm of H₂O) conditions. Catalysts were compared in terms of activity, selectivity for the different reaction products (CO₂, HCl, Cl₂, C₂Cl₄, CCl₄ and CHCl₃), and stability at reaction conditions.

As general trend, the activity of the catalysts decreases in the order Ru  Pd > Rh > Pt. Concerning to the effect of the water addition, no important effect on the catalyst activity was observed, except in the case of Pt, for which an increase of the catalytic activity was observed. Reaction mechanism (and hence product distribution) is very similar for Rh, Pd and Pt, being in these cases C₂Cl₄ the only organochlorinated by-product detected. In the case of Ru, the reaction mechanism seems to be quite different, CCl₄ and CHCl₃ being the main organic by-products.

Simple power-law kinetic expressions (first order on trichloroethene concentration for Pd, Rh and Ru, and zeroth order for Pt) provide fairly good fits for catalytic performance of the studied catalysts.

Finally, deactivation studies show that both formation of active metal chlorides (especially in the case of Rh) and fouling (especially for Pd and Pt) are the main deactivation causes.     

Mesoporous catalysts for the synthesis of clean diesel fuels by oligomerisation of olefins

Si/Al MCM-41 type mesoporous compounds, as such or containing small amounts of metal (Ni, Rh or Pt), were investigated in the synthesis of clean diesel fuels by oligomerisation of orphan olefin streams. Very good catalytic performances were obtained with C₄ and C₅ olefins, while almost no conversion occurred with ethylene. The activity increased with increasing reaction pressure, temperature and contact time, while high Si/Al ratios had a negative effect on both activity and catalyst stability. The presence of small amount of metal inside the mesoporous structure did not significantly modify the catalytic activity, although specific effects were detected for each element. Since the evaluation of the cetane number by H-NMR gave rise to values about 20% lower than the actual value, a new and more complex algorithm is proposed to calculate the cetane number. Using the proposed algorithm, a good correlation index was found between calculated and motor values for pure compounds. Further study is necessary to move from pure compounds to experimental mixtures.     

Trace Ru-doped anodic alumina-supported Ni catalysts for steam reforming of kerosene: Activity performance and electrical-heating possibility

A plate-type Ru-doped anodic alumina-supported Ni catalyst was synthesized to investigate its activity and electrical-heating possibility in steam reforming of kerosene (SRK). The catalyst showed a favorable SRK durability, which was associated with a synergistic effect between Ru and Ni, referring to the formation of Ru–Ni alloy. Under an electrical-heating pattern, the SRK system could reach stability within ca. 15 min, and no deactivation was observed during the 10 h test. Therefore, this plate-type catalyst is very promising, because it is a multipurpose reforming catalyst for SRK as well as SRM and has a swift startup.     

Comparative study of support effects in ruthenium catalysts applied for wet air oxidation of aromatic compounds

Catalytic wet air oxidation (CWAO) reactions of aniline and phenol were conducted over supported ruthenium catalysts. Three support materials were employed: ZrO₂ and graphite, which exhibit medium adsorption capacities for pollutants and present mesopores in their texture, and an activated carbon. This latter has higher adsorption capacity for pollutants because of the large capability of the micropores for contaminant retention from water. The Ru catalysts supported on the activated carbon material showed the higher values of conversion in the oxidation of aniline and of conversion and mineralization in the reaction of phenol. Under our experimental conditions the role of micropores present on the support material seems to be relevant for improving catalytic performances. The incorporation of Ru nanoparticles from different precursors has been also evaluated. Even if the final Ru particle size is a key parameter for the catalytic mineralization, a cooperative effect with the activated carbon support has been established.     

The promoting effect of Pb on carbon supported Pt and Pt/Ru catalysts for electro-oxidation of ethanol

Carbon supported Pt/Pb and Pt/Ru/Pb catalysts were prepared by deposition of Pb on commercial Pt and Pt/Ru catalysts, respectively. It was found that after addition of Pb, the catalytic activity of Pt and Pt/Ru for ethanol oxidation increased greatly, especially at high potentials. It has been shown that decorating commercial Pt and Pt/Ru catalysts with Pb is a simple and effective way to prepare carbon supported Pt/Pb and Pt/Ru/Pb catalysts for ethanol oxidation. The physical properties of the catalysts were characterized by XRD, EDX and TEM, and it was found that no Pt/Pb and Pt/Ru/Pb alloys were formed.     

Catalytic Oxidation of Alkylaromatics over Mesoporous (Cr)MCM-41

Liquid-phase catalytic oxidation of certain alkylaromatics over mesoporous (Cr)MCM-41 molecular sieves in the presence of chlorobenzene and tertiary butylhydroperoxide showed high substrate conversion and excellent product selectivity. The high catalytic activity of the materials is attributed to the complete oxidation of chromium ions to hexavalent chromium and the absence of pentavalent chromium in the mesoporous matrix.     

Effect of different catalysts on urea–formaldehyde resin synthesis

Four catalysts (H₂SO₄, HCl, H₃PO₄, and NaOH/NH₄OH) were studied in the preparation of melamine modified urea–formaldehyde (UFM) resins. ¹³C‐nuclear magnetic resonance spectroscopic analysis of the UFM resins at different synthesis stages revealed the polymer structure and detailed reaction mechanism. Three acidic catalysts (H₂SO₄, HCl, and H₃PO₄) enhanced the resin polymerization through the formation of various contents of methylene, ether linkages, and urons. H₃PO₄ yielded the most terminal ether linkages at the first stage and enhanced polycondensation by depleting all free urea and glycols to form the most linear methylene linkages NHCH₂NH in the end. However, at the initial synthesis stage, NaOH/NH₄OH catalyzed the formation of UFM prepolymer to a limited extent with a large amount of free urea left, and therefore produced the final polymer with relatively more substituted methylolureas and linear ether linkages. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40644.