Showing papers on "Partial oxidation published in 2021"
TL;DR: Au@AuIr2 showed 4.6 (5.6) times higher intrinsic (mass) activity toward the oxygen evolution reaction (OER) than a commercial Ir catalyst as discussed by the authors.
Abstract: Developing efficient bifunctional electrocatalysts for overall water splitting in acidic conditions is the essential step for proton exchange membrane water electrolyzers (PEMWEs). We first report the synthesis of core-shell structure nanoparticles (NPs) with an Au core and an AuIr2 alloy shell (Au@AuIr2). Au@AuIr2 displayed 4.6 (5.6) times higher intrinsic (mass) activity toward the oxygen evolution reaction (OER) than a commercial Ir catalyst. Furthermore, it showed hydrogen evolution reaction (HER) catalytic properties comparable to those of commercial Pt/C. Significantly, when Au@AuIr2 was used as both the anode and cathode catalyst, the overall water splitting cell achieved 10 mA/cm2 with a low cell voltage of 1.55 V and maintained this activity for more than 40 h, which greatly outperformed the commercial couples (Ir/C||Pt/C, 1.63 V, activity decreased within minutes) and is among the most efficient bifunctional catalysts reported. Theoretical calculations coupled with X-ray-based structural analyses suggest that partially oxidized surfaces originating from the electronic interaction between Au and Ir provide a balance for different intermediates binding and realize significantly enhanced OER performance.
108 citations
TL;DR: In this paper, a thermally stable metal oxide-supported single-atom Pt catalysts by flame spray pyrolysis was reported. But, the performance of the single atom catalysts in CO oxidation, methane combustion and methane partial oxidation reactions was not evaluated.
Abstract: Obtaining stable single-atom catalysts (SACs) for high-temperature applications remains challenging due to the thermodynamically favourable metal sintering under harsh reaction conditions. Taking advantage of the high-temperature process conditions (> 1000 °C), we hereby report the preparation of thermally stable metal oxide-supported single-atom Pt catalysts by flame spray pyrolysis. Among the four common supports (Al2O3, SiO2, TiO2 and ZrO2) evaluated, single-atom Pt species were identified on Al2O3, TiO2 and ZrO2, among which ZrO2 was the best to stabilize atomically dispersed Pt. Compared to single-atom Pt catalysts prepared through the conventional impregnation method, samples synthesized by flame spray pyrolysis displayed excellent catalytic performance in CO oxidation, methane combustion and methane partial oxidation reactions. Characterization results revealed that flame spray pyrolysis favoured the formation of tetragonal-monoclinic phase of ZrO2 with improved redox property, thus leading to enhanced catalytic activity in high-temperature applications.
77 citations
TL;DR: In this article, a co-axial dielectric barrier discharge (DBD) was used for the partial oxidation of methane (POM) to higher-value liquid fuels and chemicals over supported transition metal catalysts (Ni/γ-Al2O3, Cu/γ−Al 2O3 and Fe/γ −Al 2 O3) at room temperature and atmospheric pressure.
Abstract: Direct conversion of methane into chemicals and fuels under mild conditions has been considered as a ‘holy grail’ of chemistry and catalysis in the 21st century. Plasma-catalytic partial oxidation of methane (POM) to higher-value liquid fuels and chemicals over supported transition metal catalysts (Ni/γ-Al2O3, Cu/γ-Al2O3 and Fe/γ-Al2O3) has been investigated in a co-axial dielectric barrier discharge (DBD) reactor at room temperature and atmospheric pressure. The selectivity of oxygenates was 58.3% in the plasma POM reaction without a catalyst, while the combination of DBD with the catalysts enhanced the selectivity of oxygenates up to 71.5%. Of the three catalysts, Fe/γ-Al2O3 showed the highest methanol selectivity of 36.0% and a significant methanol yield of 4.7%, while the use of Cu/γ-Al2O3 improved the selectivity of C2 oxygenates to 9.4%, which can be attributed to the presence of more acid sites on the surfaces of the Cu catalyst. The possible reaction pathways in the plasma-catalytic POM reaction have been explored by combined means of plasma electrical and optical diagnostics, analysis of gas and liquid products, as well as comprehensive catalyst characterization. The plausible reaction routes for the production of major oxygenate (methanol) on the Fe/γ-Al2O3 surfaces have been proposed. The surface CHx species are found to be critical for methanol synthesis; they can be formed through the direct adsorption of CHx radicals generated in the plasma gas-phase reactions or through the dissociation of adsorbed CH4 on the catalyst surface.
58 citations
TL;DR: In this article, a review of partial oxidation of methane (POM) using perovskite-based catalysts in fixed-bed reactors was presented, and the material screening of mixed ionic-electronic conducting membranes (MIEC) membrane reactors was introduced.
Abstract: Partial oxidation of methane (POM) offers a promising option to produce syngas for downstream processes such as hydrogen production and Fischer-Tropsch processes. POM in fixed-bed reactors requires an oxygen separation plant with high operation cost and safety risks. On the contrary, membrane reactors can provide an improved process by integrating both oxygen separation and catalytic reaction processes. With many advantages including high purity and efficient oxygen separation from the air at the catalytic reaction conditions, mixed ionic-electronic conducting membranes (MIEC) caught great attention in the scientific research field over the past two decades. In this review, POM using different catalysts in fixed-bed reactors was firstly summarized with emphasizing on perovskite-based catalysts, and then the material screening of MIEC membrane reactors was introduced and linked to the selection of conventional and perovskite catalysts. The catalytic activity, reaction mechanisms, and emerging challenges have been analyzed. Furthermore, future research directions have been outlined by highlighting the effect of electronic properties, continuous reduction-oxidation in the presence of oxygen flux, and chemical reaction mechanism on membrane/catalyst.
55 citations
TL;DR: In this article, the MgO-supported Ca2Fe2O5 redox materials were used as the oxygen carriers for simultaneous syngas production and CO2 utilization through thermochemical CO2 splitting using a two-reactor chemical looping system.
46 citations
TL;DR: In this article, an exceptionally stable cerium metal-organic framework (MOF), Ce-TTCA, which can achieve photocatalytic hydrogen (H2) production in both pH = 2 and 12 aqueous solutions using Pt as a cocatalyst (Pt/Ce-TLCA), with H2 production rates of 60.3 and 348.8 μmol g−1 h−1, respectively.
Abstract: The development of efficient and stable photocatalysts in drastic conditions is highly desirable yet remains challenging. Herein, we report an exceptionally stable cerium metal-organic framework (MOF), Ce-TTCA, which can achieve photocatalytic hydrogen (H2) production in both pH = 2 and 12 aqueous solutions using Pt as a cocatalyst (Pt/Ce-TTCA), with H2 production rates of 60.3 and 348.8 μmol g−1 h−1, respectively. More impressively, partial oxidation of Ce3+ to Ce4+ in Ce-TTCA not only extends the light harvesting ability, but also promotes the effective charge separation, thus greatly improving photocatalytic H2 production activity. The Pt/Ce-TTCA-65 with the content of 65 % Ce4+ shows 6-fold improvement of photocatalytic activity than that of Pt/Ce-TTCA without Ce4+, well highlighting that the crucial role of metal oxidation state in photocatalysis. This work represents the first report on regulating MOF photocatalysis for hydrogen production by manipulating the metal oxidation state.
42 citations
TL;DR: In this paper, the authors showed that partial oxidation of metal-nitrogen-carbon catalysts (Me-N-C, Me-= iron, cobalt and manganese) can modify their ORR mechanisms from a four- to a two-electron pathway.
39 citations
TL;DR: In this article, ZrO2 nanotube powder with a high specific surface area was decorated with Co3O4 nanoparticles and used as the electrochemical anode for the partial oxidation of methane to generate C3 alcohol products.
Abstract: The activation of methane (CH4) gas to produce more valuable liquid hydrocarbons has long been a challenging issue in catalytic research. Electrochemical oxidation is one of the main methods of methane activation and can usually proceed at in ambient temperature. However, the lack of efficient electrocatalysts limits the practical application of this strategy. In this study, ZrO2 nanotube powder with a high specific surface area was decorated with Co3O4 nanoparticles and used as the electrochemical anode for the partial oxidation of methane to generate C3 alcohol products. The Co3O4 nanoparticles formed on outer the surface of the ZrO2 nanotubes offer an accessible diffusion route for methane gas, resulting in a low onset potential for electrochemical methane activation. A high production rate of approximately 2416 μmol gcat−1 h−1 was obtained at 1.6 V (vs RHE) after 12 h of reaction. This nanostructure engineering strategy contributes to the enhancement of catalytic activity for electrochemical methane oxidation with the production of higher alcohols, which could provide a new catalyst synthesis strategy for researchers.
31 citations
TL;DR: In this paper, a chemical looping water splitting (CLWS) coupled with glycerol decomposition to simultaneously produce hydrogen and syngas was proposed using the iron-cerium-nickel (Fe-Ce-Ni) based oxygen carriers (OCs).
31 citations
TL;DR: In this article, the reaction of fuel-rich natural gas/dimethyl ether (DME) mixtures is investigated to support the further development of reaction mechanisms for these little studied reaction conditions.
27 citations
TL;DR: In this article, a small amount of Ti3AlC2 compared with Al was introduced to overcome these problems, and the phase compositions, microstructures, mechanical properties, and oxidation resistance of Al2O3-C containing refractories were investigated.
Abstract: The mechanical properties and oxidation resistance of the Al2O3-C refractories are of critical importance for iron and steel making processes. However, the evaporation of antioxidants related phases such as Al(g), Si(g), and SiO(g) would deteriorate these properties, especially during high-temperature treatment/application. Therefore, in the present work, a small amount of Ti3AlC2 compared with Al was introduced to overcome these problems. The phase compositions, microstructures, mechanical properties, and oxidation resistance of Ti3AlC2 containing refractories were investigated. The partial oxidation of Ti3AlC2 led to inherited lamellar structures such as Ti3Al1-xC2, TiC, and granular Al2TiO5 phases. The controlled oxidation of Ti3AlC2 and its volume expansion contributed to the compact-structure, thereby limiting the escape of Si and SiO vapors at high temperatures. Consequently, the mechanical properties and oxidation resistance of Ti3AlC2 containing Al2O3-C refractories treated at 1600 ℃ were improved.
TL;DR: In this article, microkinetic modeling was used to examine the potential of plasma-catalytic partial oxidation (POX) of CH4 as a promising new approach to produce oxygenates.
Abstract: We use microkinetic modeling to examine the potential of plasma-catalytic partial oxidation (POX) of CH4 as a promising new approach to produce oxygenates We study how different plasma species aff
TL;DR: In this paper, a small A-site cation radius induces severe geometric tilting of FeO6 octahedra, which weakens the FeO orbital hybridization in real space, and thus the Fe-O covalency in k space.
Abstract: Perovskite-type (ABO3) oxygen carriers (OCs) with non-stoichiometric lattice oxygen release have been widely investigated in chemical looping partial oxidation processes (CLPO), and improving the syngas yield depends crucially on tailoring their elemental composition. Nevertheless, how their composition affects the electronic structure and finally the syngas yield remains elusive. Herein, by means of experiments and density functional theory calculations, we report that A-site lanthanide affects the Fe–O covalency in LnFeO3 (Ln = La, Pr, Sm, and Gd), controlling the syngas yield of OCs. Specifically, a small A-site cation radius induces severe geometric tilting of FeO6 octahedra, which weakens the Fe–O orbital hybridization in real space, and thus the Fe–O covalency in k space. The decrease in Fe–O covalency in k space can be gauged by the increasing charge-transfer energy, i.e., GdFeO3 > SmFeO3 > PrFeO3 > LaFeO3. The increase in the charge-transfer energy increases the formation energy of oxygen vacancies and the migration energy of oxygen anions, finally deteriorating oxygen mobility and surface oxygen activity. The activity and stability tests show that the syngas yields decreased in the order of LaFeO3 > PrFeO3 > SmFeO3 > GdFeO3, corresponding to the Fe–O covalency intensity. Our findings unlock a useful tool, i.e., charge-transfer energy, for rationally designing OCs and deepening our understanding of the modulating mechanism of lattice oxygen in chemical looping technologies.
TL;DR: In this article, a divergent packed bed burner of two-layer was proposed to obtain the characteristics of methane partial oxidation, and the divergent angle, interface location and pellet diameter were used to study the temperature and species distributions.
TL;DR: In this article, the authors demonstrated the efficient electrochemical autothermal reforming of methane over a solid oxide fuel cells (SOFCs) with a catalytic layer on anode surface.
TL;DR: Partial oxidation of methane (POM) is a potential technology to increase the efficiency of synthesizing a mixture of CO and H2 called syngas, in comparison to steam reforming processes as mentioned in this paper.
Abstract: Partial oxidation of methane (POM) is a potential technology to increase the efficiency of synthesizing a mixture of CO and H2 called syngas, in comparison to steam reforming processes. Recently, s...
TL;DR: In this paper, the effects of moisture content, pressure and oxidation coefficient (n) on mole fraction, yield, gasification efficiency and energy recovery of gaseous products from SCWG or SCWPO of municipal sewage sludge, as well as on the carbon and nitrogen contents in liquid products were investigated.
TL;DR: In this article, the physicochemical properties of oxygen carriers were determined by XRD, BET, H2-TPR and CH4-Tpr, and showed that the La1-xMnCuxO3 oxygen carriers exhibited smaller crystal size and cell volume, and better reducibility.
TL;DR: In this paper, the authors consider a process incorporating a supercritical water gasification reactor, syngas reformer, and downstream Fischer-Tropsch liquid fuel synthesis unit, where the feedstock is microalgae and process heat is supplied using a concentrating solar-thermal collector.
TL;DR: In this article, a two-stage approach was used to obtain the best combination of gas hourly space velocity (GHSV), oxygen-tomethane molar ratio (O2/C ratio), and CO2-to-O2 molar ratios (CO2/O2 ratio) for syngas production.
TL;DR: In this paper, a series of cordierite monolith reactors coated with perovskite oxide were prepared for chemical looping steam methane reforming (CL-SMR), and the reaction performance of the monolith oxygen carriers was tested in a fixed bed, and the temperature and the flow field of the reaction process were simulated using the computational fluid dynamics model.
TL;DR: In this article, the reaction kinetics of DRM over high-performance Ni-W/Al2O3-MgO bimetallic catalyst are investigated in a fixed bed reactor.
TL;DR: In this paper, a win-win scheme of partial oxidation of POM to syngas and N2 purification using a high performance ceramic hollow membrane reactor was reported, where the mixed ionic and electronic conducting doped La0.8Ca0.2Fe0.95Ag0.05O3−δ (LCF-Ag) powder enduring harsh environment at high temperatures was synthesized and prepared into hollow fibre membranes.
TL;DR: In this paper, the influence of the support on the cobalt-derived catalysts activity was established, which indicated that the support type not only influenced activity but also selectivity to lactic acid.
Abstract: Co3O4 supported on CeO2, ZrO2 and TiO2, were used as catalysts in glycerol partial oxidation to lactic acid. The aim was to establish the influence of the support on the cobalt-derived catalysts activity. The most active catalyst based on TOF followed the order: Co3O4/CeO2 (1.2 × 10−1 s−1) > Co3O4/ZrO2 (8.3 × 10-2 s−1) > Co3O4/TiO2 (3.0 × 10-2 s−1), with lactic acid selectivity at comparable glycerol conversion (53.5 ± 5.5 %) being higher when using CeO2 support, Co3O4/CeO2 (90 %) > Co3O4/ZrO2 (78 %) > Co3O4/TiO2 (68 %). These results indicated that the support type not only influenced activity but also selectivity to lactic acid. The Co3O4/CeO2 catalyst with less exposed cobalt species at the surface enriched in Co3+ ions, a more homogeneous composition of cobalt species being reduced at low temperatures, with acid sites of middle strength and lower density of acidic sites, is at the origin of a greater selectivity towards lactic acid, in addition this catalyst was active in 4 catalytic cycles.
TL;DR: In this paper, a single-atom catalysts with nitrogen and oxygen dual-coordination (Cu1-N3O1 moiety) was proposed for direct catalytic oxidation of benzene to phenol.
Abstract: Single atom catalysts (SACs) with metal1-Nx sites have shown promising activity and selectivity in direct catalytic oxidation of benzene to phenol. The reaction pathway is considered to be involving two steps, including a H2O2 molecule dissociated on the metal single site to form the (metal1-Nx)=O active site, and followed by the dissociation of another H2O2 on the other side of metal atom to form O=(metal1-Nx)=O intermediate center, which is active for the adsorption of benzene molecule via the formation of a C-O bond to form phenol. In this manuscript, we report a Cu SAC with nitrogen and oxygen dual-coordination (Cu1-N3O1 moiety) that doesn’t need the first H2O2 activation process, as verified by both experimental and density function theory (DFT) calculations results. Compared with the counterpart nitrogen-coordinated Cu SAC (denoted as Cu1/NC), Cu SAC with nitrogen and oxygen dual-coordination (denoted as Cu1/NOC) exhibits 2.5 times higher turnover frequency (TOF) and 1.6 times higher utilization efficiency of H2O2. Particularly, the coordination number (CN) of Cu atom in Cu1/NOC maintains four even after H2O2 treatment and reaction. Combining DFT calculations, the dynamic evolution of single atomic Cu with nitrogen and oxygen dual-coordination in hydroxylation of benzene is proposed. These findings provide an efficient route to improve the catalytic performance through regulating the coordination environments of SACs and demonstrate a new reaction mechanism in hydroxylation of benzene to phenol reaction.
TL;DR: In this article, the surface composition of clean metallic and oxidized chromium exposed to atmospheric conditions was carried out employing X-ray photoelectron spectroscopy (XPS), and advanced tools were used for the fitting process and surface composition analysis.
TL;DR: In this paper, a gold particle with an average size of dAu ~ 4nm was dispersed on ZnO by the deposition precipitation method, and the fabricated Au/ZnO catalyst was used to produce hydrogen from reforming of methanol.
TL;DR: In this paper, a one-pot in situ synthesis of Cu-SAPO-34(D)/SiC catalytic membrane with enhanced binding strength and chemical resistance was presented.
TL;DR: In this article, a nanoscale catalytic Schottky diode from Pt nanowire arrays on TiO2 was used to determine the influence of the metal-oxide interface on catalytic selectivity, thereby affecting hot electron excitation.
Abstract: Interaction between metal and oxides is an important molecular-level factor that influences the selectivity of a desirable reaction. Therefore, designing a heterogeneous catalyst where metal-oxide interfaces are well-formed is important for understanding selectivity and surface electronic excitation at the interface. Here, we utilized a nanoscale catalytic Schottky diode from Pt nanowire arrays on TiO2 that forms a nanoscale Pt-TiO2 interface to determine the influence of the metal-oxide interface on catalytic selectivity, thereby affecting hot electron excitation; this demonstrated the real-time detection of hot electron flow generated under an exothermic methanol oxidation reaction. The selectivity to methyl formate and hot electron generation was obtained on nanoscale Pt nanowires/TiO2, which exhibited ~2 times higher partial oxidation selectivity and ~3 times higher chemicurrent yield compared to a diode based on Pt film. By utilizing various Pt/TiO2 nanostructures, we found that the ratio of interface to metal sites significantly affects the selectivity, thereby enhancing chemicurrent yield in methanol oxidation. Density function theory (DFT) calculations show that formation of the Pt-TiO2 interface showed that selectivity to methyl formate formation was much larger in Pt nanowire arrays than in Pt films because of the different reaction mechanism. Chemical interaction between metal and oxide supports is an important molecular-level factor that influences the catalytic selectivity of a desirable reaction. Here, using Pt nanowires/TiO2 catalytic nanodiodes, the authors investigate an enhancement of both selectivity and hot electron generation on metal-oxide interfacial sites.