Ru和Cu协同催化湿式氧化处理氨氮废水

采用化学还原法制备了RuCu/TiO_2双金属催化剂,并探究了Ru和Cu的协同作用对催化湿式氧化(CWAO)无害化处理氨氮废水催化性能的影响。研究结果表明,Cu的添加可有效改善Ru/TiO_2催化剂的N_2选择性,而Ru的存在可有效提高Cu/TiO_2催化剂的催化活性。反应条件为0.5 MPa、150℃、[NH_3]0=1000 mg·L~(-1)、pH=12、模拟废水处理量为33 L·(kg cat)~(-1)·h~(-1)时,1Ru2Cu/TiO_2能使废水的氨氮转化率和N_2选择性分别高达87.7%和85.9%。表征结果表明:Ru和Cu的协同在催化氧化氨氮废水过程中起了关键作用,主要体现在:Ru和Cu的强相互作用导致1Ru2Cu/TiO_2催化剂具有良好的抗流失性能,进而使得催化剂具有良好的稳定性;Ru和Cu的电子转移使得1Ru2Cu/TiO_2具有适中的亲氧性能,有效提高了催化剂的催化活性。     

Ru和Cu协同催化湿式氧化处理氨氮废水

采用化学还原法制备了RuCu/TiO₂双金属催化剂,并探究了Ru和Cu的协同作用对催化湿式氧化（CWAO）无害化处理氨氮废水催化性能的影响。研究结果表明,Cu的添加可有效改善Ru/TiO₂催化剂的N₂选择性,而Ru的存在可有效提高Cu/TiO₂催化剂的催化活性。反应条件为0.5 MPa、150℃、[NH₃]₀=1000 mg·L^-1、pH=12、模拟废水处理量为33 L·（kg cat）^-1·h^-1时,1Ru2Cu/TiO₂能使废水的氨氮转化率和N₂选择性分别高达87.7%和85.9%。表征结果表明：Ru和Cu的协同在催化氧化氨氮废水过程中起了关键作用,主要体现在：Ru和Cu的强相互作用导致1Ru2Cu/TiO₂催化剂具有良好的抗流失性能,进而使得催化剂具有良好的稳定性;Ru和Cu的电子转移使得1Ru2Cu/TiO₂具有适中的亲氧性能,有效提高了催化剂的催化活性。     

Methane coupling at low temperatures on Ru(0001) and Ru(11¯20) catalysts

The conversion of methane to higher hydrocarbons on single crystal Ru catalysts has been investigated using combined elevated-pressure kinetic measurements/surface science studies. The reaction consists of activation of methane on Ru(0001) and Ru(11¯20) surfaces to produce carbonaceous intermediates at temperatures between 350 and 700 K and rehydrogenation of these species to ethane and propane at 370 K. It is found that under the reaction conditions employed, the maximum yield in ethane/propane production occurs at 500 K on both surfaces. Influence of the hydrogenation temperature on the production of ethane and propane is also examined. On Ru(0001), the yields of ethane and propane maximize at = 400 K, whereas no maximum yield was observed on Ru(11 0) in the 300–500 K temperature range. Under optimum reaction conditions, hydrocarbon products consist of 16% ethane and 2% propane. High-resolution electron energy-loss spectroscopy (HREELS) has been used to identify various forms of hydrocarbonaceous intermediates following methane decomposition. An effort is made to relate the hydrocarbon intermediates identified by HREELS to the gas phase products observed in the elevated pressure experiments.     

Structure and Composition of Au–Cu and Pd–Cu Bimetallic Catalysts Affecting Acetylene Reactivity

Au–Cu and Pd–Cu bimetallic model catalysts were prepared on native SiO₂/Si(100) substrate under ultra high vacuum (UHV) by employing buffer layer assisted growth procedure with amorphous solid water as the buffer material. The effect of the bimetallic nanoclusters (NCs) surface composition and morphology on their chemical reactivity has been studied with acetylene decomposition and conversion to ethylene and benzene as the chemical probe. It was found that among the Au–Cu NCs compositions, Au_0.5Cu₃ NCs revealed outstanding catalytic selectivity towards ethylene formation. These NCs were further characterized by employing TEM, XPS and HAADF-STEM coupled EDX analysis. With CO molecule as a probe, CO temperature programmed desorption has been used to investigate the distribution of gold on the top-most surface of the supported clusters. Surface segregation at high relative elemental fraction of gold leads to a decreased activity of the Au–Cu NCs towards ethylene formation. In contrast to the Au–Cu NCs, the Pd–Cu bimetallic system reveals reduced sensitivity to the relative elemental composition with respect to selectivity of the acetylene transformation toward ethylene formation. On the other hand, remarkable activity towards benzene formation has been observed at elemental composition of Cu₃Pd, at comparable rates to those for ethylene formation on clean Pd NCs.     

H2 and H2/CO oxidation mechanism on Pt/C, Ru/C and Pt–Ru/C electrocatalysts

The oxidation kinetics of H₂ and H₂ + 100 ppm CO were investigated on Pt, Ru and Pt–Ru electrocatalysts supported on a high-surface area carbon powder. The atomic ratios of Pt to Ru were 3, 1 and 0.33. XRD, TEM, EDS and XPS were used to characterize the electrocatalysts. When alloyed with ruthenium, a decrease in mean particle size and a modification of the platinum electronic structure were identified. Impedance measurements in H₂SO₄, at open circuit potential, indicated different mechanisms for hydrogen oxidation on Pt/C (Tafel–Volmer path) and Pt–Ru/C (Heyrowsky–Volmer path). These mechanisms also occur in the presence of CO. Best performances, both in H₂ and H₂ + CO, were achieved by the catalyst with the ratio Pt/Ru = 1. This is due to a compromise between the number of free sites and the presence of adsorbed water on the catalyst. For CO tolerance, an intrinsic mechanism not involving CO electroxidation was proposed. This mechanism derives from changes in the electronic structure of platinum when alloyed with ruthenium.     

CO2 hydrogenation over micro‐ and mesoporous oxides supported Ru catalysts

We prepared relatively uniform supported Ru catalysts by ion‐exchange and CVD methods, using an NaY zeolite and a mesoporous FSM‐16 as substrates, and carried out CO₂ hydrogenation. They showed high activity for CO₂ hydrogenation. A Ru‐ion‐exchanged catalyst showed high activity for methanol production. Co addition promoted methanol formation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sugar Hydrogenation Over Supported Ru/C—Kinetics and Physical Properties

The hydrogenation kinetics of some natural sugars to corresponding sugar alcohols in aqueous solutions was investigated on Ru/C catalysts in a pressurized slurry reactor. The kinetic data were well described by a Langmuir-Hinshelwood model assuming that the hydrogenation step on the catalyst surface is rate determining. The density, viscosity and hydrogen solubility of the reacting liquid were measured. This information was used to estimate the liquid-phase diffusion coefficients, which were utilized in a reaction-diffusion-catalyst deactivation model for porous catalyst layers. The model indicated that diffusional resistance becomes severe for rather small catalyst particles and the model described the movement of the reactive front inside the particle during the reaction. The simulation results indicate that structured reactors would provide a better approach than the conventional fixed bed technology, if continuous operation is desired.     

Interaction of carbon monoxide with Cu–Pd and Cu–Ni bimetallic clusters

Interaction of CO with Cu–Pd and Cu–Ni bimetallic clusters deposited on a ZnO substrate has been investigated by core-level spectroscopy. The surface reactivity of both these alloy clusters increases with the decrease in cluster size, giving rise to dissociative adsorption at small cluster size. The surface reactivity also increases with the increase in Pd or Ni content and the reactivity of the alloy clusters is unlike that of either component metal. Thus, dissociative adsorption occurs on small Cu–Pd clusters unlike on either Cu or Pd clusters of comparable size. The reactivity of the Cu–Ni clusters, on the other hand, falls somewhere between those of Cu and Ni clusters. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism of CH4 Dry Reforming on Nanocrystalline Doped Ceria-Zirconia with Supported Pt, Ru, Ni, and Ni–Ru

Specificity of CH₄ dry reforming mechanism for Me-supported doped ceria-zirconia catalysts with high oxygen mobility was elucidated using a combination of transient kinetic methods (TAP, SSITKA) with pulse microcalorimetry and in situ FTIRS. Steady-state reaction of CH₄ dry reforming is described by a simple redox scheme with independent stages of CH₄ and CO₂ activation. This is provided by easy CO₂ dissociation on reduced sites of oxide supports followed by a fast oxygen transfer along the surface/domain boundaries to metal sites where CH₄ molecules are transformed to CO and H₂. The rate-limiting stage is irreversible transformation of CH₄ on metal sites, while CO₂ transformation proceeds much faster being reversible for steady-state surface. The oxygen forms responsible for CH₄ selective transformation into syngas correspond to strongly bound bridging oxygen species with heats of desorption ≈600–650 kJ/mol O₂, most probably bound with pairs of Pr and/or Ce cations able to change their oxidation state. Ni + Ru clusters could be involved in CO₂ activation via facilitating C–O bond breaking in the transition state, thus increasing the rate constant of the surface reoxidation by CO₂. Strongly bound carbonates are spectators.     

Effect of Cu strike coating on adhesion between Cu–Sn coated steel and rubber

In order to improve the adhesion between steel and rubber, a novel coating deposition technique has been developed, where steel substrate with orchestrated surface roughness was coated with double-layer coatings consisting of a thin Cu strike layer followed by a Cu–Sn layer with varying Sn compositions by immersion route. Coating surface characteristics studied using scanning electron microscope coupled with energy dispersion spectroscopy analyzer, electron probe micro analyzer, and inductively coupled plasma optical emission spectroscopy showed improvement in surface coverage with coating after employing the strike layer coating attributed to the better coating penetration in the deep roughness troughs. Peel test of the coated samples vulcanized with styrene butadiene rubber (SBR) was carried out which showed improvement in adhesion strength of the double-layer-coated samples inferring more uniform Cu-sulfide layer formation at interface due to more uniform coating coverage in these samples. Highest peel strength with uniform cohesive fracture within rubber was observed for optimum 2–3?wt% Sn content in the coatings. This result was further supported by pull-out test conducted on coated wire samples vulcanized with SBR.     

Oxygen-enhanced water gas shift on ceria-supported Pd–Cu and Pt–Cu bimetallic catalysts

Aiming at enhancing H₂ production in water gas shift (WGS) for fuel cell application, a small amount of oxygen was added to WGS reaction toward oxygen-enhanced water gas shift (OWGS) on ceria-supported bimetallic Pd–Cu and Pt–Cu catalysts. Both CO conversion and H₂ yield were found to increase by the oxygen addition. The remarkable enhancement of H₂ production by O₂ addition in short contact time was attributed to the enhanced shift reaction, rather than the oxidation of CO on catalyst surface. The strong dependence of H₂ production rate on CO concentration in OWGS kinetic study suggested O₂ lowers the CO surface coverage. It was proposed that O₂ breaks down the domain structure of chemisorbed CO into smaller domains to increase the chance for coreactant (H₂O) to participate in the reaction and the heat of exothermic surface reaction helping to enhance WGS kinetics. Pt–Cu and Pd–Cu bimetallic catalysts were found to be superior to monometallic catalysts for both CO conversion and H₂ production for OWGS at 300 °C or lower, while the superiority of bimetallic catalysts was not as pronounced in WGS. These catalytic properties were correlated with the structure of the bimetallic catalysts. EXAFS spectra indicated that Cu forms alloys with Pt and with Pd. TPR demonstrated the strong interaction between the two metals causing the reduction temperature of Cu to decrease upon Pd or Pt addition. The transient pulse desorption rate of CO₂ from Pd–Cu supported on CeO₂ is faster than that of Pd, suggesting the presence of Cu in Pd–Cu facilitate CO₂ desorption from Pd catalyst. The oxygen storage capacity (OSC) of CeO₂ in the bimetallic catalysts indicates that Cu is much less pyrophoric in the bimetallic catalysts due to lower O₂ uptake compared to monometallic Cu. These significant changes in structure and electronic properties of the bimetallic catalysts are the result of highly dispersed Pt or Pd in the Cu nanoparticles.     

Zr- and Li-Modified Ru/Sio2 Catalysts for Fischer–Tropsch Synthesis

We have found that Zr- and Li-modified Ru/SiO₂ catalysts (Q-15) are extremely stable and can be used in FT synthesis to maintain the conversion rate of CO constant even after 33 h. Modification of Ru/SiO₂ by Zr (5 wt%) and Li (0.1 wt%) resulted in a remarkable increase in the stability of the catalyst. Taking into account surface acidity and reducibility, we assumed that this remarkable stability is due to the cooperative effects of Ru, Zr, Li, and the SiO₂ support.     

High energy ball-milled Pt and Pt–Ru catalysts for polymer electrolyte fuel cells and their tolerance to CO

High energy ball milling, an industrially amenable technique, has been used to produce CO tolerant unsupported Pt–Ru based catalysts for the oxidation of hydrogen in polymer electrolyte fuel cells. Nanocrystalline Pt_0.5–Ru_0.5 alloys are easily obtained by ball-milling but their performances as anode catalysts are poor because nanocrystals composing the material aggregate during milling into larger particles. The result is a low specific area material. Improved specific areas were obtained by milling together Pt, Ru and a metal leacheable after the milling step. The best results were obtained by milling Pt, Ru, and Al in a 1:1:8 atomic ratio. After leaching Al, this catalyst (Pt_0.5–Ru_0.5 (Al₄)) displays a specific area of 38 m²g^–1. Pt_0.5–Ru_0.5 (Al₄) is a composite catalyst. It consists of two components: (i) small crystallites (4 nm) of a Pt–Al solid solution (1–3 Al wt%) of low Ru content, and (ii) larger Ru crystallites. It shows hydrogen oxidation performance and CO tolerance equivalent to those of Pt_0.5–Ru_0.5 Black from Johnson Matthey, the commercial catalyst which was found to be the most CO tolerant one in this study.     

Supported Pt and Pt–Ru catalysts prepared by potentiostatic electrodeposition for methanol electrooxidation

Methanol electrooxidation was investigated on Pt–Ru electrocatalysts supported on glassy carbon. The catalysts were prepared by electrodeposition from solutions containing chloroplatinic acid and ruthenium chloride. Bulk composition analysis of the Pt–Ru catalyst was performed using an X-ray detector for energy dispersive spectroscopy analysis (EDX). Three different compositions were analyzed in the range 0–20 at.% Ru content. Tafel plots for the oxidation of methanol in solutions containing 0.1–2 M CH₃OH, and in the temperature range 23–50 °C showed a reasonably well-defined linear region. The slope of the Tafel plots was found to depend on the ruthenium composition. The lower slope was determined for the Pt catalyst, varying between 100 and 120 mV dec⁻¹. The values calculated for the alloys were higher, ranging from 120 to 140 mV dec⁻¹. The reaction order for methanol varies from 0.5 to 0.8, increasing with the ruthenium content. The activation energy calculated from Arrhenius plots was found to change with the catalyst composition, showing a lower value around 30 kJ mol⁻¹ for the alloys, and a higher value, of 58.8 kJ mol⁻¹, for platinum. The effect of ruthenium content is explained by the bifunctional reaction mechanism.     

Water-gas shift reaction over Cu–Zn,Cu–Fe,and Cu–Zn–Fe composite-oxide catalysts prepared by urea-nitrate combustion

Water-gas shift reaction was investigated over Cu–Zn, Cu–Fe and Cu–Zn–Fe composite-oxide catalysts at atmospheric pressure from 200 to 375 °C in terms of reducing the CO content with maximal H₂ yield. The Cu_0.15ZnFe₂ spinel catalyst expressed a higher CO conversion level and H₂ yield at a lower temperature compared to the Cu_0.15Zn and Cu_0.15Fe catalysts. Adding H₂O to the feed up to 30% (v/v), but not above, increased the CO reduction level, presumably by increasing the hydroxyl species to react with the adsorbed CO. Increasing the W/F ratio to 0.24 g s cm^?3 increased the CO conversion level to 0.76 at 275 °C with the Cu_0.15ZnFe₂ catalyst, and could be further increased to 0.86 at 350 °C by increasing the Cu molar ratio to 0.30 (Cu_0.30ZnFe₂). Nevertheless, increasing the Cu molar content to 0.50 reduced the CO conversion level. No requirement for adding O₂ when using the Cu_0.30ZnFe₂ catalyst at >260 °C was observed. Increasing the CO content in the reactant decreased its conversion level. The performance of the Cu_0.30ZnFe₂ catalyst was stable over a test period in a CO-rich condition. No undesired product was detected, suggesting a higher selectivity for hydrogen production with a low CO content.     

Cu掺杂Ru/Al2O3催化剂催化环己醇空气氧化合成环己酮的研究

环己酮作为一种重要的有机化工原料，常用于制造己二酸和己内酰胺，并且广泛应用于纤维、合成橡胶、工业涂料、医药、农药和有机溶剂等工业领域。以H₂O₂做氧化剂，通过相转移催化剂催化或杂多酸为催化剂可实现环己醇氧化制备环己酮。然而，高浓度H₂O₂的强腐蚀性和易爆危险性，以及制备工艺的繁琐性使其应用受到限制。因此，寻求安全且成本低廉的催化工艺成为研究重点。本文以Cu掺杂Ru/Al₂O₃作为催化剂，空气为氧化剂，在釜式工艺下研究环己醇的氧化反应，考察了反应溶剂、温度、压力、催化剂组分等对反应的影响。     

Catalysts Ru–CeO2/Sibunit for catalytic wet air oxidation of aniline and phenol

Catalytic properties of carbon materials Sibunit (commercial samples) and ceria-promoted precious metals (Ru, Pt, Pd) supported on carbon were studied in the processes of catalytic wet air oxidation (CWAO) of aniline and phenol at elevated pressures and temperatures (T =433–473 K, P_O2 = 0.3–1.0 MPa). It was found that the activity increases when the catalyst is pretreated with hydrogen peroxide. An efficiency of Ru–CeO₂/Sibunit catalyst with a low ruthenium content (~0.6 Ru) for deep cleaning of polluted waters is demonstrated.     

Preparation and electrochemical characterization of Ti/Ru x Mn1−x O2 electrodes

DSA^® type electrodes of ruthenium–manganese mixed oxides (30 at % Ru < 100) supported on titanium were prepared by the spray-pyrolysis technique, using Ru(NO)(OH) _x (NO₃)_3–x and Mn(NO₃)₂ as precursors. Electrodes were characterized by SEM, XRD and cyclic voltammetry. Their behaviour as anode for the chlorine and oxygen evolution reactions was also evaluated by polarization curves. The stability of the mixed oxides was determined through accelerated tests of service life. It has been verified that the best performance on the apparent electrocatalytic activity of both reactions as well as on stability is achieved at a composition of about 70% Ru.