Activity For Methanol Decomposition Research Articles

Effect of surface acidity modulation on Pt/Al2O3 single atom catalyst for carbon monoxide oxidation and methanol decomposition

With ideal metal utilization efficiency and homogeneous active sites, single atom catalysts (SACs) have attracted extensive attention in heterogeneous catalysis field. The performance of SACs is highly dependent on the local coordination environment of metal single atoms. However, few works reported the effect of surface acidity modification on the performance of SACs such as Pt SACs which have been widely studied nowadays. In this work, a Pt/Al2O3 SAC has been successfully prepared using a bayerite Al(OH)3 as support through simple IWI method for Pt loading. Through post-modification of Pt/Al2O3 with acidic WO3 and basic MgO, the surface acidity of Pt/Al2O3 was tuned. Activity of CO oxidation and methanol decomposition on the modified catalysts has been evaluated. It was found that the catalytic performance was highly related to the surface acidity of Pt SACs. Basic MgO modified Pt/Al2O3 performed better in CO oxidation under the reaction condition with H2O. Acidic WO3 modified Pt/Al2O3 showed superior activity in methanol decomposition. Detailed characterization and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study suggested that the positive H2O effect on CO oxidation was due to the mitigated formation of bicarbonate species on Pt/Al2O3 and WO3/Pt/Al2O3 catalysts and the promoted desorption of carbonate species from MgO/Pt/Al2O3. The superior methanol decomposition performance on WO3/Pt/Al2O3 was owing to its abundant oxygen vacancies and high resistance to carbonate accumulation. This study highlights the importance of surface acidity modulation of Pt SACs in heterogeneous catalysis and suggests that fine-tuning the surface acidity can be an effective strategy in new SACs development.

Nickel-Decorated Mesoporous Iron–Cerium Mixed Oxides: Microstructure and Catalytic Activity in Methanol Decomposition

Nickel-decorated mesoporous cerium-iron oxide composites were synthesized by a combination of incipient wetness impregnation and template-assisted hydrothermal techniques. The effects of the Fe/Ce ratio and the calcination temperature of cerium-iron oxides on the phase composition, texture, structure, and redox properties of the composites were studied by a combination of N2 physisorption, XRD, high-resolution transmission electron microscopy, SEM, Mössbauer, Raman, XPS, ultraviolet-visible and FTIR spectroscopies, H2-temperature-programmed reduction, and total oxidation of ethyl acetate as a catalytic test. The combined physicochemical characterization and in situ FTIR investigation of methanol decomposition was used for a proper understanding of the microstructure of the Ni/FeCe oxide composites and the mechanism of the reaction occurring on them. The complex role of the FeCe support in the stabilization of highly dispersed Ni particles, the generation of surface intermediates, and the impact of the support phase transformation under the reaction medium are discussed.

A New Method for Synthesizing Co-precipitated Cu–ZnO Catalyst and Its Activity for Methanol Decomposition at High Temperature

A New Method for Synthesizing Co-precipitated Cu–ZnO Catalyst and Its Activity for Methanol Decomposition at High Temperature

Characterization of Ni3Sn intermetallic nanoparticles fabricated by thermal plasma process and catalytic properties for methanol decomposition

ABSTRACT The intermetallic compound Ni3Sn has potential for application in hydrogen production as a catalyst. Herein, we synthesized Ni3Sn nanoparticles through a thermal plasma process. We characterized the nanoparticles by synchrotron radiation X-ray diffraction and transmission electron microscopy analyses, and analyzed their catalytic properties for methanol decomposition in a temperature range of 513 to 793 K. The Ni3Sn nanoparticles showed a higher selectivity to H2 and CO than pure Ni nanoparticles, but a relatively lower catalytic activity for methanol decomposition compared to pure Ni nanoparticles. Density functional theory calculations revealed that the activation energy barrier for CO dissociation on Ni3Sn (001) was 396 kJ/mol, which was higher than that for Ni (111). Moreover, the activation energy barrier for OH formation on Ni3Sn (001) was 229 kJ/mol, which was significantly higher than that for Ni (111). This supported the experimental results and confirmed that the Ni3Sn catalyst suppresses the formation of carbon and H2O, compared to Ni catalyst.

Valorization of coal treatment residues as a host matrix of nanosized nickel, copper and zinc ferrites

High quality activated carbon was prepared using by-products from the pyrolysis of low rank coals as a precursor. The obtained carbon material was applied as a host matrix of nanosized MFe2O4 ferrites (M = Ni, Cu or Zn). XRD, Mossbauer and TPR analyses were performed for samples characterization and their catalytic behavior in methanol decomposition as a source of hydrogen was tested. In contrast to the reference mesoporous KIT-6 silica based analogues, the active phase in the carbon modifications was more accessible for the reactants and represented a complex mixture of metals, alloys, substituted magnetite and finely dispersed ferrites, which ensured their higher catalytic activity in methanol decomposition.

Synthesis and Mössbauer spectroscopic investigation of copper-manganese ferrite catalysts for water-gas shift reaction and methanol decomposition

Copper-manganese ferrites with nominal compositions Cu1-хMnхFe2O4, where x=0; 0.2; 0.4; 0.6; 0.8 and 1 are synthesized by sol-gel auto-combustion method. Formation of ferrites with cubic spinel structure and crystallite size of 11–26nm was observed. A decrease of iron located in tetrahedral positions with the increase of Mn content in ferrite structure was found. The prepared ferrite materials are tested as catalysts in water-gas shift reaction (WGSR) and methanol decomposition (MD). The samples are arranged according the WGS activity in following order: Cu0.8Mn0.2Fe2O4>Cu0.5Mn0.5Fe2O4>CuFe2O4>Cu0.2Mn0.8Fe2O4>MnFe2O4. All mixed copper-manganese ferrites exhibit higher catalytic activity in methanol decomposition as compared to single CuFe2O4 and MnFe2O4 ones. A significant phase transformation with ferrites under the reduction reaction medium which influences the formation of real catalytic active phase is registered. Formation of magnetite or Mn-substituted magnetite is registered during the WGSR, while iron carbides and Mn-rich oxides are the dominant phases during the MD reaction.

Zinc ferrites hosted in activated carbon from waste precursors as catalysts in methanol decomposition

Activated carbons from peach stones and waste polyolefin wax were prepared and tested as a host matrix of nanodispersed zinc ferrite. Nitrogen physisorption, Boehm method, XRD, TPR with hydrogen, FTIR, UV–Vis and Moessbauer spectroscopy were applied to investigate the activated carbon characteristics and the state of loaded on it metal oxide particles. The higher microporosity and lower surface functionality, typical of activated carbon from waste biomass, facilitated the formation of more finely dispersed, located into the micropores iron and zinc oxide nanoparticles. This promoted formation of Zn rich ferrite phase which ensures high catalytic activity in methanol decomposition.

Catalytic Properties of Ni-Al Intermetallic Nanoparticles Fabricated by Thermal Plasma Process

The catalytic activity of Ni-Al (Ni25Al) nanoparticles fabricated by thermal plasma evaporation was examined for methanol decomposition and CO oxidation. The nanoparticles exhibited high activity for both reactions. Characterization of the nanoparticles revealed that the fabricated nanoparticles were mainly comprised of Ni and Ni3Al phases. During CO oxidation, the Ni phase was oxidized to NiO, while the Ni3Al phase remained unchanged. The NiO phase is supposed to serve as the active sites for CO oxidation. In contrast, during methanol decomposition, no obvious oxidation was observed for both Ni and Ni3Al phases. The Ni and Ni3Al phases are supposed to contribute to the high activity for methanol decomposition.

Effect of mesoporous silica topology on the formation of active sites in copper supported catalysts for methanol decomposition

Modified incipient wetness impregnation procedure was applied for deposition of finely dispersed CuO or metallic copper particles into ordered mesoporous silica host matrix (KIT-6 and SBA-15). This modified procedure consists of number of consecutive impregnation steps with copper nitrate solution with changeable concentration and soft drying under vacuum procedures. Nitrogen physisorption, XRD, UV–vis, TEM–EDXS, FTIR of probe molecules (CO, NO and N2) and TPR were applied for characterization of copper state in the matrix. The obtained materials were tested as catalysts in methanol decomposition. Selected catalytic experiments were carried out under very low coverage of the surface with 11C-radiolabelling methanol. In situ FTIR study of methanol decomposition was also performed. It was found that the catalytic behaviour of copper, supported on mesoporous materials, depends in a complex way on the dispersion and accessibility of copper species within the host matrix. They can be tuned by copper loading and pore topology of the support. The optimal catalytic activity in methanol decomposition is achieved at about 8 and 15wt.% copper content for the SBA-15 and KIT-6 mesoporous supports, respectively.

Formation of catalytic active sites in copper and manganese modified SBA-15 mesoporous silica

A series of copper and manganese oxides modified SBA-15 mesoporous silicas with different composition was prepared by incipient wetness impregnation with the corresponding nitrate precursors and compared with the analogous materials supported on conventional SiO2. Nitrogen physisorption, XDR, FTIR, UV–Vis and temperature programmed reduction with hydrogen were used for samples characterization. Their catalytic activity was tested in ethyl acetate oxidation and methanol decomposition. The ordered porous structure of the support facilitates the interaction between different metal oxide nanoparticles and increases their dispersion due to the formation of mixed oxide phase. The ethyl acetate oxidation on SBA-15 binary materials is suppressed due to the lower accessibility of the metal oxide particles, located deeply into the micro-meso pores of the support. The reaction medium which forms during the methanol decomposition provides the reduction/decomposition transformations with the mixed oxide phase. The final phase composition of finely dispersed Cu/CuO and MnOx particles stabilizes in a highly dispersed state into the porous matrix of SBA-15 support and increases the catalytic activity in methanol decomposition due to the appearance of synergistic effect between them.

Nanostructured copper, chromium, and tin oxide multicomponent materials as catalysts for methanol decomposition: 11C-radiolabeling study

Copper and chromium modified tin oxide nanocomposites were obtained via incipient wetness impregnation of high surface area nanosized SnO2 with the corresponding metal acetylacetonates and their further decomposition in air. Powder X-ray diffraction (XRD), Nitrogen physisorption, UV–Vis, and Temperature-programmed reduction (TPR) with hydrogen were applied for the samples characterization. The catalytic activity of the obtained materials was tested in methanol conversion. A new approach based on the selective coverage of the surface with 11C-methanol was used for the characterization of the catalytic sites. It was demonstrated that the products distribution could be controlled by the surface coverage with methanol and the role of different active sites was discussed. The modification of SnO2 with copper oxide increased the activity in methanol decomposition to CO2via dioxymethylene intermediates, but the catalyst suffered considerable loss of activity due to the reduction transformations by the reaction medium and formation of an inactive intermetallic alloy. The modification with chromium changed the acid-basic properties of SnO2 by the formation of Cr2O3 nanoparticles as well as anchored to the support chromate species. The former particles facilitated the formation of dimethyl ether (DME), while the latter species converted methanol predominantly to hydrocarbons. The fraction of chromate species increased in Cu–Cr–Sn oxide multicomponent nanocomposites and promoted the formation of hydrocarbons over DME at low temperatures, while at higher temperatures, the activity of the copper species leading to CO2 formation was more pronounced.

Spark plasma sintering synthesis of Ni1−xZnxFe2O4 ferrites: Mössbauer and catalytic study

Nickel-zinc ferrite nanoparticles, Ni1−xZnxFe2O4 (x = 0, 0.2, 0.5, 0.8, 1.0) were prepared by combination of chemical precipitation and spark plasma sintering (SPS) techniques and conventional thermal treatment of the obtained precursors. The phase composition and structural properties of the obtained materials were investigated by X-ray diffraction and Mössbauer spectroscopy and their catalytic activity in methanol decomposition was tested. A strong effect of reaction medium leading to the transformation of ferrites to a complex mixture of different iron containing phases was detected. A tendency of formation of Fe-carbide was found for the samples synthesized by SPS, while predominantly iron-nickel alloys ware registered in TS obtained samples. The catalytic activity and selectivity in methanol decomposition to CO and methane depended on the current phase composition of the obtained ferrites, which was formed by the influence of the reaction medium.

Catalytic Properties of Ni<sub>3</sub>Fe Foil for Hydrogen Production from Methanol

The objective of this study is to investigate the catalytic properties of intermetallic Ni3Fe foil. We fabricated Ni3Fe foil of 30 µm in thickness by a metallurgical process, and examined the catalytic activity of the Ni3Fe foil for methanol decomposition from 513 to 973 K. The Ni3Fe foil showed activity for methanol decomposition above 623 K. The activity increased with the increase of reaction temperature. Surface analysis revealed that a surface structure of fine Ni-Fe particles dispersed on carbon nanofibers was formed on the foil during the reaction. The activity is attributed to the formation of this fine structure.

Catalytic Properties of TiNi Foils for Methanol Decomposition

The catalytic properties of the cold-rolled foils of intermetallic compound TiNi were studied for hydrogen production from methanol in a temperature range of 513-793 K. The catalytic activity for methanol decomposition increased with a reaction temperature, especially above 673 K. The SEM and EDS analyses revealed the formation of numerous Ni-enriched particles dispersed in the layer of carbon fibers during the reaction. The catalytic activity of TiNi foils is attributed to those Ni-enriched particles.

Synthesis of Ni-Al Intermetallic Nanoparticle Catalysts by Vacuum Arc Plasma Evaporation

In order to pursue high catalytic performance of Ni-Al intermetallic compounds for hydrogen production, we synthesized Ni-Al intermetallic nanoparticles from Ni-Al alloy ingots by vacuum arc plasma evaporation technique for the first time. The characterization of the synthesized nanoparticles was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy. The catalytic properties of the Ni-Al nanoparticles for methanol decomposition were evaluated. It is found that the nanoparticles had a large surface area above 70 m2/g, and showed very high catalytic activity for methanol decomposition.

Properties of alkali-promoted Cu–MgO catalysts and their activity for methanol decomposition and C 2-oxygenate formation

The decomposition of CH 3OH in the presence of CO has been investigated over high surface area MgO, Cu–MgO, K–Cu–MgO and Cs–Cu–MgO catalysts. The catalysts were prepared by thermal decomposition of metal salts mixed with palmitic acid. The reduced catalysts had surface areas of 18–74 m 2 g −1 and intrinsic basicities of 4–17 μmol CO 2 m −2. Results revealed that methyl formate was a primary product of CH 3OH decomposition, whereas CO was a secondary product. Although selectivity to C 2 species (ethanol and acetic acid) was low (<5 C-atom %) at the low pressure (101 kPa) conditions of the present study, there was an optimum intrinsic basicity (9.5 μmol CO 2 m −2) at which the selectivity to C 2 species and methyl formate reached a maximum. The role of catalyst basic properties in the formation of C 2 species from CH 3OH is discussed.

Size-selected Pt Nanoparticles Synthesized via Micelle Encapsulation: Effect of Pretreatment and Oxidation State on the Activity for Methanol Decomposition and Oxidation

The effect of pretreatment conditions on the oxidation state and activity of micelle-synthesized Pt nanoparticles supported on ZrO2 was studied for methanol decomposition and oxidation reactions. An O2-pretreatment is observed to be effective for producing clean, stable, and active nanoparticles. Pt-oxide species formed during such pretreatments were found to have little influence in methanol decomposition reactions due to their tendency to reduce. However, these same species are stable during methanol oxidation and appear to take part in a Mars-van Krevelen-type of process, in which bound-oxygen (nanoparticle shell) may be replenished with oxygen from the gas phase.

Cobalt-modified mesoporous MgO, ZrO 2, and CeO 2 oxides as catalysts for methanol decomposition

Cobalt oxide-modified mesoporous CeO 2, ZrO 2, and MgO oxides and their SBA-15 silica analogues were prepared and characterized by XRD, TEM, N 2 physisorption, FTIR, and TPR–TG analysis. Their catalytic activity in methanol decomposition to CO and hydrogen was tested. The support effect on the state and catalytic behavior of the loaded cobalt oxide nanoparticles is discussed. The best catalytic activity and selectivity of methanol decomposition to CO and hydrogen are registered for Co/CeO 2.

Catalytic Properties of Ni3Al Foils for Hydrogen Production

AbstractWe have successfully developed thin foils of boron-free Ni3Al (below 100 μm in thickness) by cold rolling, and recently found that the foils exhibit high catalytic activity for methanol decomposition. A little has been known about catalytic activity in Ni3Al. Even more interestingly, the high catalytic activity appears on flat foils whose surface area is very low. This paper provides a review of the characteristic features of the catalytic properties investigated in my group. Methanol was effectively decomposed into H2 and CO over the foils above 713 K. The production rates of H2 and CO increased with an increase of time during the initial period of reaction, indicating that the Ni3Al foils were spontaneously activated under the reaction conditions. Surface analyses revealed that fine Ni particles dispersed on carbon nanofibers formed on the foils during the reaction. The high catalytic performance of the foils can be attributed to the spontaneous formation of this nanostructure during the reaction.

Catalytic Properties of Ni&lt;sub&gt;3&lt;/sub&gt;Al for Hydrogen Production Reactions

Ni3Al has attractive high temperature properties, such as high strength and good oxidation/corrosion resistance, and is possible to be used for high temperature chemical processing and manufacture. Until now, the catalytic properties of Ni3Al were rarely investigated since the leaching of aluminum from Ni3Al is difficult to obtain a porous Raney-Ni compared to NiAl3 and Ni2Al3. In the present work, the catalytic properties of Ni3Al were examined for hydrogen production reactions from methanol. It was found that alkali-leached Ni3Al showed high activity for methanol decomposition (CH3OH→ 2H2+CO). Furthermore, Ni3Al catalysts suppress the formation of methane, i.e. they show higher selectivity for the methanol decomposition reaction than Ni catalyst. These results indicate a possibility for Ni3Al used as a catalyst for hydrogen production reaction.