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We investigated the catalytic properties of a CuNi solid solution and Pd for methanol-related reactions and associated valence electronic structures. Calculations and X-ray photoelectron spectroscopy measurements revealed that the CuNi alloy has a similar valence electronic structure to Pd and hence they exhibited similar CO selectivities in steam reforming of methanol and decomposition of methanol. Samples prepared by various processes were found to have similar CO selectivities. We conjecture that alloying of Cu and Ni dramatically alters the valence electronic structures, making it similar to that of Pd so that the alloy exhibits similar catalytic properties to Pd. First-principles slab calculations of surface electronic structures support this conjecture. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic performance of steam reforming of methanol (SRM), cross-sectional microstructure and leaching process of an Al63Cu25Fe12 quasicrystal (QC) catalyst were studied. The QC catalyst was prepared by the NaOH leaching. The leaching of the QC alloy generated a homogeneous leached layer composed of Cu, Fe, Al, and their oxides. The activity and stability of the QC catalyst for the SRM was much superior to those of related crystalline alloy catalysts, because the highly dispersed Fe species in the homogeneous leached layer of the QC catalyst enhances the catalytic activity and suppresses the aggregation of Cu particles. The quasiperiodic structure of the Al-Cu-Fe QC was stable against leaching and had a relatively low dissolution rate of Al among the Al-Cu-Fe alloys, which resulted in the formation of a homogeneous leached layer that was responsible for the high activity and stability for SRM. [ABSTRACT FROM AUTHOR]

Unsupported mesoporous intermetallic (usmpIM) NiZn and PdZn catalysts are successfully prepared by means of a two-step procedure: (1) leaching of Al-based intermetallic compounds (Al3Ni, Al21Pd8) with 20 wt% NaOH aqueous solution and (2) immersion of ZnCl2 aqueous solution into unsupported porous Ni or Pd followed by alloying treatment under H2 flow at 500 °C, i.e., immersion alloying process. Thermal stability of the mesoporous structures is found to be improved by alloying with Zn. The catalytic properties for steam reforming of methanol (SRM) were completely different from the original unsupported porous Ni and Pd, where the decomposition of methanol and the SRM occurred preferentially on usmpIM NiZn and usmpIM PdZn, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The optimum preparation condition of Al–Cu–Fe quasicrystalline (QC) catalyst with excellent catalytic performance for steam reforming of methanol (SRM) has been investigated. The QC alloy is superior to the other crystalline Al–Cu–(Fe) alloys (i.e., beta and theta phase) as a catalyst material because of the brittle nature of QC. The wet milling process (in ethanol) for the QC powders is much better than the dry milling process to obtain fine particles with high surface area. The QC powder prepared by the wet process followed by leaching in Na2CO3 aq. at 323K exhibited the highest catalytic performance (activity and stability) in the present study. From these findings, it is clear that the QC catalyst with the excellent catalytic performance could be obtained by controlling the initial grain size of the QC powder and the leaching temperature. [Copyright &y& Elsevier]

Abstract: The catalytic properties of Ni3Al intermetallics were studied for hydrogen production from methanol. It is found that the alkali-leached Ni3Al powders show a high catalytic activity for the methanol decomposition (CH3OH→2H2+CO). The rate of hydrogen production increases rapidly with increasing reaction temperature. Furthermore, the Ni3Al catalysts suppress the formation of methane and water gas shift reaction, i.e. they show higher selectivity for methanol decomposition than nickel catalysts. These results indicate that the Ni3Al catalysts are highly promising as a catalyst for hydrogen production. [Copyright &y& Elsevier]

Alloy catalysts were prepared by leaching various structures of Al–Cu–(Fe) alloys (quasicrystal (QC), beta- or theta-phase) in NaOH and Na2CO3 aqueous solutions. Comparison of the catalytic properties for steam reforming of methanol (SRM) on different Al–Cu–(Fe) alloy phases (quasicrystalline versus crystalline phase) was made. At high temperatures (e.g., 360 °C), the catalytic activity of the QC catalyst (5% Na2CO3-leached) for the SRM was much higher than that of other phase catalysts. No sintering of highly dispersed copper particles on QC catalyst was observed by XRD measurements even after the SRM reaction at 360 °C. We propose that the high catalytic activity and the excellent thermal stability of copper particles on QC catalyst are due to the immiscibility of Fe with Cu and the interaction with QC surface. [Copyright &y& Elsevier]

Climate change, global warming, and energy crisis have become an important problem due to the environmental impact of fossil fuels. Hence, alternate energy source is needed for environmental remediation. One such source could be hydrogen (H 2). H 2 is used as an alternate energy carrier due to it is non-toxic, clean, and efficient. Steam reforming of methyl alcohol (or) methanol (SRM) is a widely available and low-cost hydrogen production method. In this stream-reforming process, mostly commercial zinc-supported catalyst is used, these have some economic defect. Therefore, we need to find alternate suitable catalysts for the SRM process. In this study, ZnCr X Fe 2-X O 4 (X = 0–2) porous catalyst powders of different ratios were synthesized by the glycine nitrate process (GNP) for hydrogen production by SRM. The specific surface areas of the ZnCr X Fe 2-X O 4 powders ranged from 15.75 m2/g to 45.16 m2/g. The ZnCr 0.4 Fe 1.6 O 4 powder had the highest H 2 production without activation, reaching 6850.33 ml STP min−1 g-cat−1 at a reaction temperature of 450 °C. ZnCr 0.4 Fe 1.6 O 4 porous powders prepared using the GNP method have simple, rapid process steps, low cost, high catalytic activity, and they can be applied to hydrogen fuel cells or other related catalysis applications in the future. The pure hydrogen production performance of these ZnCr X Fe 2-X O 4 catalysts could be of great importance in industry and economic impact. • ZnCr X Fe 2-X O 4 (X = 0–2) catalyst were synthesized by the glycine nitrate process for hydrogen production by SRM. • ZnCr X Fe 2-X O 4 (X = 0–2) porous powders prepared using the GNP with simple, low-cost, high catalytic activity. • The specific surface areas of the ZnCr X Fe 2-X O 4 (X = 0–2) powders ranged from 15.75 m2/g to 45.16 m2/g. • The ZnCr 0.4 Fe 1.6 O 4 powder had the highest H 2 production reaching 6850.33 ml STP min−1 g-cat−1 at 450 °C without activation. [ABSTRACT FROM AUTHOR]

Catalytic activity and CO2 selectivity over carbon black-supported Pd with the addition of Zn (Zn–Pd/C) was comparable to those of Pd/ZnO in methanol steam reforming. From the characterization of fresh Zn–Pd/C after H2 reduction pretreatment by means of BET surface area, XRD, TEM and the measurement of CO adsorption, Pd–Zn alloy particles were detected on Zn–Pd/C. This is also supported by high CO2 selectivity in methanol steam reforming over Zn–Pd/C as well as Pd/ZnO. In addition, Zn–Pd/C exhibited higher stability than Pd/ZnO in methanol steam reforming. After the reaction for the life test, the formation of zinc carbonate hydroxide such as Zn4CO3(OH)6·H2O was clearly observed on Pd/ZnO. It is expected that the deactivation is caused by covering active Pd–Zn alloy particles with zinc carbonate hydroxide. Although this phenomenon can also occur on Zn–Pd/C, the deactivation rate was much lower than Pd/ZnO because the amount of free ZnO is much smaller on Zn–Pd/C. [Copyright &y& Elsevier]

In this study, Fe 3 O 4 -supported Cu and Ni catalysts are prepared through reduction of Cu–Ni (Ni 1−x Cu x Fe 2 O 4 ) ferrites. The Cu–Ni ferrites, synthesized using a solid–state reaction method, are reduced at temperatures from 240 °C to 500 °C in a H 2 atmosphere. All ferrites are characterized with granular morphology and a smooth particle surface before reduction. For the CuFe 2 O 4 , Ni 0.5 Cu 0.5 Fe 2 O 4 and NiFe 2 O 4 ferrites reduced at 240, 300, and 400 °C, respectively, nanosized Cu and/or Ni particles (5–32 nm) and mesopores (5–30 nm) are distributed and adhered on the surfaces of Fe 3 O 4 supports. After increasing the reduction temperature of NiFe 2 O 4 ferrite to 500 °C, the Ni particles and mesopores disappear from the Fe 3 O 4 surfaces, which is due to the formation of a Fe–Ni alloy covering on the Fe 3 O 4 surfaces. The CuFe 2 O 4 ferrite after H 2 reduction at 240 °C exhibits the highest H 2 production rate of 149 ml STP/min g-cat at 360 °C. The existence of Ni content in the Cu–Ni ferrites enhances the reverse water gas shift reaction, and raises the CO selectivity while reducing the CO 2 selectivity. Formation of a Fe–Ni alloy exaggerates the trend and poisons the H 2 production rate. [ABSTRACT FROM AUTHOR]

In this study, various Cu-based spinel compounds, i.e., CuFe2O4, CuMn2O4, CuAl2O4 and CuLa2O4, were fabricated by a solid-state reaction method. Reduction behaviors and morphological changes of these materials have been characterized by H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Moreover, the catalytic properties for steam reforming of methanol (SRM) of these Cu-based spinel compounds were investigated. H2-TPR results indicated that the reducibility of Cu-based spinel compounds was strongly dependent on the B-site component while the CuFe2O4 catalyst revealed the lowest reduction temperature (190°C), followed respectively by CuAl2O4 (267°C), CuMn2O4 (270°C), and CuLa2O4 (326°C). The reduced CuAl2O4 catalyst demonstrated the best performance in terms of catalytic activity. Based on the SEM and XRD results, pulverization of the CuAl2O4 particles due to gas evolution and a high concentration of nanosized Cu particles (≈50.9nm) precipitated on the surfaces of the Al2O3 support were observed after reduction at 360°C in H2. The BET surface area of the CuAl2O4 catalyst escalated from 5.5 to 13.2m2/g. Reduction of Cu-based spinel ferrites appear to be a potential synthesis route for preparing a catalyst with high catalytic activity and thermal stability. The catalytic performance of these copper-oxide composites was superior to those of conventional copper catalysts. [ABSTRACT FROM AUTHOR]

Steam reforming of methanol over Zn-promoted Pt catalyst supported on an electrically conductive carbon black has been investigated after H2 reduction at 873 K. X-ray diffraction measurement showed that Pt–Zn alloy was formed on the carbon black (C). The Zn-promoted Pt/C catalyst showed higher activity and selectivity to CO2 compared with unpromoted Pt/C catalyst. Methyl formate was formed over the Zn-promoted Pt/C catalyst in decomposition of methanol (without water). This suggests that steam reforming of methanol over the Zn-promoted Pt/C catalyst can proceed via methyl formate, which is different from that of the unpromoted Pt/C catalyst. [Copyright &y& Elsevier]