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Abstract: Effect of promoters (Co, Fe, Sn, Zn) on structures, properties and catalytic performance of RuB/γ-Al2O3 catalyst was studied using in situ XRD, TEM, H2-TPD, XPS and liquid-phase hydrogenation of ethyl lactate to 1,2-propanediol (PDO). It was found that incorporation of Sn or Fe improved the dispersion and thermal stability of RuB. The electron density of Ru and the strength and capacity of H2 adsorption on the RuB catalyst were also enhanced by the incorporation of Sn or Fe. The incorporation of Co or Zn led to a significant decrease in H2 adsorption capacity of the RuB catalyst. Both ethyl lactate conversion and selectivity to 1,2-PDO increased with the incorporation of Sn or Fe. The ethyl lactate conversion decreased sharply with the incorporation of Zn or Co accompanied by an increase in selectivity to 1,2-PDO and lactic acid. The effect of promoters on reaction behavior was discussed on the basis of the characterizations. [Copyright &y& Elsevier]

Amorphous Ru-B supported on γ-Al2O3 was prepared by a novel reductant impregnation method for the hydrogenation of ethyl lactate to 1,2-propanediol (PDO). The effects of tin on composition, physicochemical properties, thermal stability and reaction behavior of Ru-B/γ-Al2O3 catalyst were studied by using in situ XRD, TEM, H2-TPD, XPS and liquid phase hydrogenation of ethyl lactate. The Ru-B/γ-Al2O3 catalyst prepared by reductant impregnation showed good activity for hydrogenation of ethyl lactate. Addition of suitable amounts of tin (Sn/Ru atomic ratio of 7%) significantly increased the ethyl lactate conversion and the selectivity to 1,2-PDO; a selectivity to 1,2-PDO of 91.5% was obtained at ethyl lactate conversion of 90.7% under mild reaction conditions. The characterizations showed that addition of tin improved the dispersion and thermal stability of Ru-B significantly. The B/Ru ratio of the catalyst, the electron density of Ru, and the strength of hydrogen adsorption of the catalyst increased with increase of tin content over the range studied. [Copyright &y& Elsevier]

Graphical abstract Highlights • K and/or P-doped carbon nitrides were synthesized from urea and different salts. • They were evaluated in visible light photocatalytic production of H 2 O 2 from O 2. • The K 2 HPO 4 /GCN (CNKP-10) catalyst produced the highest concentration of H 2 O 2. • K and P were identified to be incorporated into the framework of CNKP-10. • They narrowed down the band gap and enhanced the utility of the charge carriers. Abstract Photocatalytic production of hydrogen peroxide (H 2 O 2) from two-electron reduction of molecular oxygen over semiconductor catalysts under visible light irradiation represents a clean and sustainable strategy to transform solar energy to chemicals. Here we synthesized a series of potassium and/or phosphorus-doped carbon nitride photocatalysts by one-pot thermal polymerization of urea and different sylvites and phosphates. Among them, the K 2 HPO 4 /GCN (CNKP-10) catalyst exhibited the best visible light photocatalytic activity for H 2 O 2 production from molecular oxygen. After 10 h visible light (λ ≥ 420 nm) irradiation, the concentration of H 2 O 2 exceeded 5 mmol l–1 on this catalyst, which is more than five folds of that on the catalyst synthesized by thermal polymerization of urea only (GCN). A combination of bulk and surface characterization techniques confirmed the incorporation of potassium and phosphorus into the framework of GCN, which narrowed down the band gap, raised the conduction band, and enhanced the generation, transmission, and lifetime of the photogenerated charge carriers, thus promoting the visible light photocatalytic production of H 2 O 2 from molecular oxygen. [ABSTRACT FROM AUTHOR]

Abstract: Cu/ZnO catalysts with Cu loadings of 44–5 wt% were prepared by coprecipitation and evaluated in temperature-dependant and shut-down/start-up water–gas shift (WGS) reactions using realistic reformate. These catalysts had similar Cu crystallite sizes, and the metallic Cu surface area and surface Cu content increased with the Cu loading. In temperature-dependent reactions, the CO conversion on the 25wt%Cu/ZnO catalyst slightly exceeded that on 44wt%Cu/ZnO. In shut-down/start-up operation, which is imperative for mobile and residential fuel cell applications, the catalysts with Cu loadings higher than 5 wt% suffered slight activity loss. Among them, the 15wt%Cu/ZnO catalyst deactivated the most reluctantly. As a result, after three shut-down/start-up cycles the CO conversion on 15wt%Cu/ZnO, 25wt%Cu/ZnO, and 44wt%Cu/ZnO became comparable. These results demonstrate the feasibility to lower the Cu loading without degrading the WGS performance of the Cu/ZnO catalyst in shut-down/start-up operation, which will guarantee the operation safety when the catalyst will be operated unattended for domestic small-scale fuel cell applications. Unexpectedly, the CO conversion was doubled on 5wt%Cu/ZnO after one shut-down/start-up cycle, which is interpreted as the redispersion of Cu nanoparticles based on transmission electron microscopy (TEM) and temperature-programmed reduction (TPR). [Copyright &y& Elsevier]

Abstract: The Cu/ZnO/Al2O3 catalysts were prepared by the coprecipitation method, and were evaluated in the water–gas shift (WGS) reaction. The effects of the calcination temperature on the BET surface area and crystallite size were characterized. In WGS reaction, the Cu/ZnO/Al2O3 catalysts suffered from continuous deactivation in shut-down/start-up operation – the daily requirement for mobile and residential fuel cell systems. Among them, the Cu/ZnO/Al2O3 catalyst prepared at the calcination temperature of 450°C showed the best activity and stability, with the decrement of the CO conversion of only 12.8% after three shut-down/start-up cycles. Deactivation of the Cu/ZnO/Al2O3 catalysts is attributed to the blocking or deterioration of the active sites by Zn6Al2(OH)16CO3·4H2O resulting from the degeneration of the oxides under cyclic operations. Removal of the hydroxycarbonate species by calcination in air followed by re-reduction could restore the steady-state WGS activity; however, the regenerated catalyst underwent much severe deactivation in subsequent shut-down/start-up operation. [Copyright &y& Elsevier]

A colloidal RuB/Al2O3·xH2O catalyst has been synthesized through a combined coprecipitation–crystallization–reduction strategy and characterized in detail with techniques including ICP-AES, N2 physisorption, XRD, TG/DTA, PSD and TEM. The catalytic behavior in liquid phase selective hydrogenation of benzene to cyclohexene was studied and compared with that of the RuB/γ-Al2O3 catalyst prepared by the incipient-wetness impregnation method. The RuB/Al2O3·xH2O catalyst is found more reactive than the RuB/γ-Al2O3 catalyst, and the maximum yield of cyclohexene is about four times as high as that over the latter. The better activity of the colloidal catalyst is assigned to the higher dispersion of the smaller RuB particles, whereas its superior selectivity is attributed to the improved hydrophilicity due to higher content of structural water and surface hydroxyl groups. [Copyright &y& Elsevier]

A Ru–Zn/m-ZrO2 nanocomposite catalyst for benzene partial hydrogenation to cyclohexene was prepared by coprecipitation of ruthenium trichloride and zirconium oxychloride with ammonia, followed by hydrogen reduction in an aqueous zinc sulfate solution. By use of transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), the reduction of zinc cation to metallic zinc and the transformation of zirconium hydroxide to monoclinic zirconia were proposed and explained. The hydrogenation parameters, such as the amount of zinc sulfate in the pretreatment process, the hydrogenation temperature, the stirring rate, and the hydrogen pressure, influenced the yield of cyclohexene. The pronounced positive effect of metallic zinc in enhancing the cyclohexene yield was discussed. [Copyright &y& Elsevier]

The La-doped Co-B/SiO2 amorphous catalyst (Co-La-B/SiO2) was prepared by chemical reduction of mixed Co2+ and La3+ ions deposited on a silica support with KBH4 aqueous solution at room temperature. The catalyst was employed in the liquid phase hydrogenation of cinnamaldehyde (CMA) to cinnamyl alcohol (CMO). At suitable content, the La-additives exhibited promoting effects on both the activity and the selectivity to CMO. The optimum La-content (χLa) was determined as 0.014 (molar fraction), over which the CMO yield could reach 80%. Based on various characterizations, the promoting effect of the La-dopant on the selectivity to CMO was mainly attributed to the presence of La2+ and La3+. These La-species were favorable for both the activation of the C&z.dbnd6;O bond and the formation of H− species and thus, promoted the hydrogenation of C&z.dbnd6;O bond. These roles also promoted the hydrogenation activity. Besides, the promoting effect of the La-dopant might also attributed to the presence of the La oxides which increased the surface Co active sites. At high χLa, the activity decreased again due to the coverage of the Co active sites by the inactive La-additives and also due to the too strong adsorption of carbonyl group induced by La3+ and La2+. Such strong adsorption might hinder the competitive adsorption of hydrogen. [Copyright &y& Elsevier]