Doubling the life of Cu/ZnO methanol synthesis catalysts via use of Si as a structural promoter to inhibit sintering
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ABSTRACT:
SUBMITTER: Barrow N
PROVIDER: S-EPMC10793955 | biostudies-literature | 2024 Jan
REPOSITORIES: biostudies-literature
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Project description:The synergistic interaction among different components in complex catalysts is one of the crucial factors in determining catalytic performance. Here we report the interactions among the three components in controlling the catalytic performance of Cu-ZnO-ZrO2 (CZZ) catalyst for CO2 hydrogenation to methanol. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements under the activity test pressure (3 MPa) reveal that the CO2 hydrogenation to methanol on the CZZ catalysts follows the formate pathway. Density functional theory (DFT) calculations agree with the in situ DRIFTS measurements, showing that the ZnO-ZrO2 interfaces are the active sites for CO2 adsorption and conversion, while the presence of metallic Cu is also necessary to facilitate H2 dissociation and to provide hydrogen resource. The combined experiment and DFT results reveal that tuning the interaction between ZnO and ZrO2 can be considered as another important factor for designing high performance catalysts for methanol generation from CO2.
| S-EPMC6411953 | biostudies-literature
Project description:Cu/ZnO-based catalysts for methanol synthesis by CO x hydrogenation are widely prepared via co-precipitation of sodium carbonates and nitrate salts, which eventually produces a large amount of wastewater from the washing step to remove sodium (Na+) and/or nitrate (NO3 -) residues. The step is inevitable since the remaining Na+ acts as a catalyst poison whereas leftover NO3 - induces metal agglomeration during the calcination. In this study, sodium- and nitrate-free hydroxy-carbonate precursors were prepared via urea hydrolysis co-precipitation of acetate salt and compared with the case using nitrate salts. The Cu/ZnO catalysts derived from calcination of the washed and unwashed precursors show catalytic performance comparable to the commercial Cu/ZnO/Al2O3 catalyst in CO2 hydrogenation at 240-280 °C and 331 bar. By the combination of urea hydrolysis and the nitrate-free precipitants, the catalyst preparation is simpler with fewer steps, even without the need for a washing step and pH control, rendering the synthesis more sustainable.
| S-EPMC8697775 | biostudies-literature
Project description:The modification of Cu-Zn catalysts with low amount of Al and Ga (Al+Ga = 3%) was investigated and data corresponding to its influence on the decomposition of the calcined precursors and on the nanomorphology and surface concentration of reduced catalysts were presented in this contribution. The data presented here are supplementary material of the catalysts presented in the research article "Structure and activity of Cu/ZnO catalysts co-modified with aluminium and gallium for methanol synthesis" published in Catalysis Today [1].
| S-EPMC6538956 | biostudies-literature
Project description:The heterogeneously catalysed reaction of hydrogen with carbon monoxide and carbon dioxide (syngas) to methanol is nearly 100 years old, and the standard methanol catalyst Cu/ZnO/Al2O3 has been applied for more than 50 years. Still, the nature of the Zn species on the metallic Cu0 particles (interface sites) is heavily debated. Here, we show that these Zn species are not metallic, but have a positively charged nature under industrial methanol synthesis conditions. Our kinetic results are based on a self-built high-pressure pulse unit, which allows us to inject selective reversible poisons into the syngas feed passing through a fixed-bed reactor containing an industrial Cu/ZnO/Al2O3 catalyst under high-pressure conditions. This method allows us to perform surface-sensitive operando investigations as a function of the reaction conditions, demonstrating that the rate of methanol formation is only decreased in CO2-containing syngas mixtures when pulsing NH3 or methylamines as basic probe molecules.
| S-EPMC7403733 | biostudies-literature
Project description:The quest for efficient catalysts based on abundant elements that can promote the selective CO2 hydrogenation to green methanol still continues. Most of the reported catalysts are based on Cu/ZnO supported in inorganic oxides, with not much progress with respect to the benchmark Cu/ZnO/Al2O3 catalyst. The use of carbon supports for Cu/ZnO particles is much less explored in spite of the favorable strong metal support interaction that these doped carbons can establish. This manuscript reports the preparation of a series of Cu-ZnO@(N)C samples consisting of Cu/ZnO particles embedded within a N-doped graphitic carbon with a wide range of Cu/Zn atomic ratio. The preparation procedure relies on the transformation of chitosan, a biomass waste, into N-doped graphitic carbon by pyrolysis, which establishes a strong interaction with Cu nanoparticles (NPs) formed simultaneously by Cu2+ salt reduction during the graphitization. Zn2+ ions are subsequently added to the Cu-graphene material by impregnation. All the Cu/ZnO@(N)C samples promote methanol formation in the CO2 hydrogenation at temperatures from 200 to 300 °C, with the temperature increasing CO2 conversion and decreasing methanol selectivity. The best performing Cu-ZnO@(N)C sample achieves at 300 °C a CO2 conversion of 23% and a methanol selectivity of 21% that is among the highest reported, particularly for a carbon-based support. DFT calculations indicate the role of pyridinic N doping atoms stabilizing the Cu/ZnO NPs and supporting the formate pathway as the most likely reaction mechanism.
| S-EPMC10934795 | biostudies-literature
Project description:Noble metals such as Au, Ag, and Cu supported over semiconducting ZnO are well-known heterogeneous oxidation catalysts. All of them have been utilized for the oxidation of diesel soot with varied success. However, Au-supported ZnO is seen to be superior among them. Here, we present a comparative study of all these three catalysts for diesel soot oxidation to explain why Au/ZnO is the best among them, demonstrating the contribution of electronic states of metals in composite catalysts. The electronic states of Cu, Ag, and Au determined by X-ray photoelectron spectroscopy on 1 wt % Cu/ZnO, 1 wt % Ag/ZnO, and 1 wt % Au/ZnO catalysts were correlated with their diesel soot oxidation activities. Although all three catalysts present reasonable diesel soot oxidation activities at relatively low temperature, 1% Cu/ZnO and 1% Ag/ZnO oxidize only about 60% of the deposited diesel soot around 250 °C and 1% Au/ZnO oxidizes 100% of the deposited diesel soot, at a temperature as low as 230 °C. The activity of the catalysts is attributed to the formation of stable M0-Mδ+ bifunctional catalytic sites at the metal-ZnO interface, which enhances the contact efficiency of solid diesel soot on Mδ+ and generates the superoxide species on M0 moieties. The stability of the bifunctional M0-Mδ+ sites is controlled by the electronic interactions between the metal (M) and n-type semiconductor ZnO at their interface. Very high activity of 1% Au/ZnO is attributed to the presence of Au3+ at the catalyst surface, which generates a stronger Coulombic force with diesel soot electrons. We demonstrate a direct relation between the diesel soot oxidation activity of these three metals and their electronic states at the catalyst surface.
| S-EPMC6648296 | biostudies-literature
Project description:The nature of the Cu-Zn interaction and especially the role of Zn in Cu/ZnO catalysts used for methanol synthesis from CO2 hydrogenation are still debated. Migration of Zn onto the Cu surface during reaction results in a Cu-ZnO interface, which is crucial for the catalytic activity. However, whether a Cu-Zn alloy or a Cu-ZnO structure is formed and the transformation of this interface under working conditions demand further investigation. Here, ZnO/Cu2O core-shell cubic nanoparticles with various ZnO shell thicknesses, supported on SiO2 or ZrO2 were prepared to create an intimate contact between Cu and ZnO. The evolution of the catalyst's structure and composition during and after the CO2 hydrogenation reaction were investigated by means of operando spectroscopy, diffraction, and ex situ microscopy methods. The Zn loading has a direct effect on the oxidation state of Zn, which, in turn, affects the catalytic performance. High Zn loadings, resulting in a stable ZnO catalyst shell, lead to increased methanol production when compared to Zn-free particles. Low Zn loadings, in contrast, leading to the presence of metallic Zn species during reaction, showed no significant improvement over the bare Cu particles. Therefore, our work highlights that there is a minimum content of Zn (or optimum ZnO shell thickness) needed to activate the Cu catalyst. Furthermore, in order to minimize catalyst deactivation, the Zn species must be present as ZnOx and not metallic Zn or Cu-Zn alloy, which is undesirably formed during the reaction when the precatalyst ZnO overlayer is too thin.
| S-EPMC10979448 | biostudies-literature
Project description:For decades it has been debated whether the conversion of synthesis gas to methanol over copper catalysts is sensitive or insensitive to the structure of the copper surface. Here we have systematically investigated the effect of the copper particle size in the range where changes in surface structure occur, that is, below 10 nm, for catalysts with and without zinc promotor at industrially relevant conditions for methanol synthesis. Regardless of the presence or absence of a zinc promotor in the form of zinc oxide or zinc silicate, the surface-specific activity decreases significantly for copper particles smaller than 8 nm, thus revealing structure sensitivity. In view of recent theoretical studies we propose that the methanol synthesis reaction takes place at copper surface sites with a unique configuration of atoms such as step-edge sites, which smaller particles cannot accommodate.
| S-EPMC5476790 | biostudies-literature
Project description:Ni, Pt and a mixture of Ni and Pt supported on ZnO-rods were evaluated in autothermal steam reforming of methanol (ASRM) for hydrogen production as a function of the reaction temperature. The catalytic materials were characterized by SEM-EDS, XRD, TEM, HRTEM, TPR and BET. Analysis by SEM and TEM showed structural modifications on the surface of the ZnO rods after Ni impregnation. The reactivity of the catalytic materials in the range of 200-500 °C showed that the bimetallic sample had better catalytic activity among all the catalysts studied. This finding could be associated to PtZn and NiZn alloys present in this catalyst, which were identified by XRD and HRTEM analyses. Catalyst characterization by XRD after the catalytic testing showed that the intermetallic PtZn phase was stable during the reaction in the Pt/ZnO-rod sample. The cubic Ni0.75-Zn0.25 structure identified in the Ni/ZnO-rod sample was transformed to Zn0.1-Ni0.9-O and metallic Ni phases, respectively. On the bimetallic PtNi/ZnO-rod sample, the cubic Ni0.75-Zn0.25 structure remained, although the tetragonal NiZn structure is unstable and was destroyed during the ASRM reaction and then a new phase of Ni0.7Pt0.3 emerged. The promotion effect of Pt and/or Ni on the ZnO-rod was clearly shown.
| S-EPMC9057812 | biostudies-literature
Project description:Metal-support interaction has been one of the main topics of research on supported catalysts all the time. However, many other factors including the particle size, shape and chemical composition can have significant influences on the catalytic performance when considering the role of metal-support interaction. Herein, we have designed a series of CuxO/ZnO catalysts as examples to quantitatively investigate how the metal-support interaction influences the catalytic performance. The electronic metal-support interactions between CuxO and ZnO were regulated successfully without altering the structure of CuxO/ZnO catalyst. Due to the lower work function of ZnO, electrons would transfer from ZnO to CuO, which is favorable for the formation of higher active Cu species. Combined experimental and theoretical calculations revealed that electron-rich interface result from interaction was favorable for the adsorption of oxygen and CO oxidation reaction. Such strategy represents a new direction to boost the catalytic activity of supported catalysts in various applications.
| S-EPMC9136224 | biostudies-literature