The remarkable activity and stability of a highly dispersive beta-brass Cu-Zn catalyst for the production of ethylene glycol.
TL;DR: It is shown that Cu nano-clusters modified with increasing concentration of Zn, derived from ZnO support doped with Ga3+, can dramatically enhance their stability against metal sintering and show greatly enhanced activity and stability with the CuZn alloy catalysts.
Abstract: Incorporation of Zn atoms into a nanosize Cu lattice is known to alter the electronic properties of Cu, improving catalytic performance in a number of industrially important reactions. However the structural influence of Zn on the Cu phase is not well studied. Here, we show that Cu nano-clusters modified with increasing concentration of Zn, derived from ZnO support doped with Ga3+, can dramatically enhance their stability against metal sintering. As a result, the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol, an important reaction well known for deactivation from copper nanoparticle sintering, can show greatly enhanced activity and stability with the CuZn alloy catalysts due to no noticeable sintering. HRTEM, nano-diffraction and EXAFS characterization reveal the presence of a small beta-brass CuZn alloy phase (body-centred cubic, bcc) which appears to greatly stabilise Cu atoms from aggregation in accelerated deactivation tests. DFT calculations also indicate that the small bcc CuZn phase is more stable against Cu adatom migration than the fcc CuZn phase with the ability to maintain a higher Cu dispersion on its surface.
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TL;DR: In this article, the aqueous miscible organic solvent treated double hydroxide (LDH) nanosheets were synthesized following the AMO-LDH method and applied as catalyst precursors for methanol production from CO2 hydrogenation.
Abstract: Ultrathin (1–3 cationic-layers) (CuZn)1–xGax-CO3 layered double hydroxide (LDH) nanosheets were synthesized following the aqueous miscible organic solvent treatment (AMOST) method and applied as catalyst precursors for methanol production from CO2 hydrogenation. It is found that, upon reduction, the aqueous miscible organic solvent treated LDH (AMO-LDH) samples above a critical Ga3+ composition give consistently and significantly higher Cu surface areas and dispersions than the catalysts prepared from conventional hydroxyl-carbonate phases. Owing to the distinctive local steric and electrostatic stabilization of the ultrathin LDH structure, the newly formed active Cu(Zn) metal atoms can be stably embedded in the cationic layers, exerting an enhancement to the catalytic reaction. The best catalyst in this study displayed methanol productivity with a space-time yield of 0.6 gMeOH·gcat–1 h–1 under typical reaction conditions, which, as far as we are aware, is higher than most reported Cu-based catalysts in t...
100 citations
TL;DR: In this article, a novel CuO/ZnO/Ga2O3 catalyst was synthesized by co-precipitation method and characterized by ICP-AES, N2-physisorption, SEM-EDX and XRD.
Abstract: Highly active catalysts for the methanol steam reforming (MSR) capable of operating efficiently at the same temperature of high temperature polymer electrolyte membrane fuel cells (HTPMFCs) devices are strongly desired. A novel CuO/ZnO/Ga2O3 catalyst was synthesized by co-precipitation method and characterized by ICP-AES, N2-physisorption, SEM-EDX and XRD. This catalyst showed a catalytic activity 2.2 times higher than commercial CuO/ZnO/Al2O3 catalysts at 453 K Two kinetic models one empirical and one mechanistic were applied to describe the methanol steam reforming reaction over one of the most promising catalyst family.
55 citations
TL;DR: In this article , the use of fullerene (C60) as an electron buffer for a copper-silica catalyst (Cu/SiO2) was shown to improve the performance of DMO hydrogenation.
Abstract: Bulk chemicals such as ethylene glycol (EG) can be industrially synthesized from either ethylene or syngas, but the latter undergoes a bottleneck reaction and requires high hydrogen pressures. We show that fullerene (exemplified by C60) can act as an electron buffer for a copper-silica catalyst (Cu/SiO2). Hydrogenation of dimethyl oxalate over a C60-Cu/SiO2 catalyst at ambient pressure and temperatures of 180° to 190°C had an EG yield of up to 98 ± 1%. In a kilogram-scale reaction, no deactivation of the catalyst was seen after 1000 hours. This mild route for the final step toward EG can be combined with the already-industrialized ambient reaction from syngas to the intermediate of dimethyl oxalate. Description Promoting copper catalysts with C60 Ethylene glycol, a commodity chemical used as a feedstock and antifreeze agent, is synthesized industrially from dimethyl oxalate (DMO) by hydrogenation over precious-metal palladium catalysts at high pressures (typically 20 bars). Copper-chromium catalysts supported on silica as an alternative have required even high pressures. Zheng et al. show the addition of fullerene (C60) onto copper-silica allows DMO hydrogenation to be performed at ambient pressures with high yield (98%) and without deactivation after 1000 hours (see the Perspective by Gravel and Doris). The use of C60 to stabilize electron-deficient copper species that enhance hydrogen adsorption could likely be applied to other hydrogenation reactions catalyzed by copper. —PDS Fullerene (C60) acts as an electronic buffer that activates copper-silica heterogeneous hydrogenation catalysts at ambient pressure.
52 citations
TL;DR: An efficient ZrO2-doped Cu/SiO2 catalyst was fabricated through hydrolysis precipitation method (HP) and used to produce ethylene glycol (EG) through dimethyl oxalate (DMO) hydrogenation.
36 citations
TL;DR: In this paper, a CuO-ZnO/SiO2 catalysts with various Zn/Cu molar ratios were prepared by precipitation and characterized by XRD, H2-TPR, TEM, XAES and catalytic performance for hydrogenation of dimethyl oxalate.
35 citations
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TL;DR: This work shows how to identify the crucial atomic structure motif for the industrial Cu/ZnO/Al2O3 methanol synthesis catalyst by using a combination of experimental evidence from bulk, surface-sensitive, and imaging methods collected on real high-performance catalytic systems in combination with density functional theory calculations.
Abstract: Unlike homogeneous catalysts, heterogeneous catalysts that have been optimized through decades are typically so complex and hard to characterize that the nature of the catalytically active site is not known. This is one of the main stumbling blocks in developing rational catalyst design strategies in heterogeneous catalysis. We show here how to identify the crucial atomic structure motif for the industrial Cu/ZnO/Al{sub 2}O{sub 3} methanol synthesis catalyst. Using a combination of experimental evidence from bulk-, surface-sensitive and imaging methods collected on real high-performance catalytic systems in combination with DFT calculations. We show that the active site consists of Cu steps peppered with Zn atoms, all stabilized by a series of well defined bulk defects and surface species that need jointly to be present for the system to work.
1,888 citations
TL;DR: Improved new methods for the efficient reductive conversion of CO(2) to methanol and/or DME that the authors have developed include bireforming with methane and ways of catalytic or electrochemical conversions.
Abstract: Nature’s photosynthesis uses the sun’s energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time can new fossil fuels be formed naturally. In contrast, chemical recycling of carbon dioxide from natural and industrial sources as well as varied human activities or even from the air itself to methanol or dimethyl ether (DME) and their varied products can be achieved via its capture and subsequent reductive hydrogenative conversion. The present Perspective reviews this new approach and our research in the field over the last 15 years. Carbon recycling represents a significant aspect of our proposed Methanol Economy. Any available energy source (alternative energies such as solar, wind, geothermal, and atomic energy) can be used for the production of needed hydrogen and chemical conversion of CO2. Improved new methods for the efficient reductive conversion of CO2 to methanol and/or DME that we have developed include bireformin...
1,236 citations
TL;DR: Analyses of developments in methanol steam reforming in the context of PEM fuel cell power systems and reactor and system development and demonstration.
Abstract: Review article covering developments in methanol steam reforming in the context of PEM fuel cell power systems. Subjects covered include methanol background, use, and production, comparison to other fuels, power system considerations, militrary requirements, competing technologies, catalyst development, and reactor and system development and demonstration.
874 citations
TL;DR: In this paper, the authors report on the activity of Cu-and Ni-containing cerium oxide catalysts for low-temperature water-gas shift (WGS) in nanocrystalline form by urea co-precipitation-gelation method.
Abstract: In this paper we report on the activity of Cu- and Ni-containing cerium oxide catalysts for low-temperature water-gas shift (WGS). Bulk catalysts were prepared in nanocrystalline form by the urea co-precipitation–gelation method. Lanthanum dopant (10 at.%) was used as a structural stabilizer of ceria, while the content of Cu or Ni was in the range of 5–15 at.% (2–8 wt.%). At low metal loadings, Cu or Ni were present in the form of highly dispersed oxide clusters, while at high loadings, clusters as well as particles of CuO or NiO (>10 nm in size) were present on ceria. Both Cu and Ni increased the reducibility of ceria, as evidenced by H2-TPR experiments. The WGS reaction activity of Ce(La)Ox was increased significantly by addition of a small amount (2 wt.%) of Cu or Ni. The catalysts were not activated prior to testing. Steady-state WGS kinetics were measured over the temperature range of 175–300 and 250–300°C, respectively, for Cu- and Ni–Ce(La)Ox. The activation energy of the reaction over Ce(La)Ox was 58.5 kJ/mol, while it was 38.2 and 30.4 kJ/mol, respectively, over the 5 at.% Ni–Ce(La)Ox and 5 at.% Cu–Ce(La)Ox catalysts in CO-rich conditions. A co-operative redox reaction mechanism, involving oxidation of CO adsorbed on the metal cluster by oxygen supplied to the metal interface by ceria, followed by H2O capping the oxygen vacancy on ceria, was used to fit the kinetics. Parametric studies were mainly performed with the 5 at.% Cu–(La)Ox catalyst. Notably, this material requires no activation and retains high WGS activity and stability at temperatures up to 600°C.
800 citations
TL;DR: A broad spectrum of properties of EG and significant advances in the prevalent synthesis and applications of EG are described, with emphases on the catalytic reactivity and reaction mechanisms of the main synthetic methodologies and applied strategies.
Abstract: Ethylene glycol (EG) is an important organic compound and chemical intermediate used in a large number of industrial processes (e.g. energy, plastics, automobiles, and chemicals). Indeed, owing to its unique properties and versatile commercial applications, a variety of chemical systems (e.g., catalytic and non-catalytic) have been explored for the synthesis of EG, particularly via reaction processes derived from fossil fuels (e.g., petroleum, natural gas, and coal) and biomass-based resources. This critical review describes a broad spectrum of properties of EG and significant advances in the prevalent synthesis and applications of EG, with emphases on the catalytic reactivity and reaction mechanisms of the main synthetic methodologies and applied strategies. We also provide an overview regarding the challenges and opportunities for future research associated with EG.
746 citations