Showing papers on "Partial oxidation published in 2020"
TL;DR: A heterogeneous catalyst system for enhanced meethanol productivity in methane oxidation by in situ generated hydrogen peroxide at mild temperature (70°C) and methanol selectivity reached 92%, corresponding to methanl productivity up to 91.6 millimoles per gram of AuPd per hour.
Abstract: Selective partial oxidation of methane to methanol suffers from low efficiency. Here, we report a heterogeneous catalyst system for enhanced methanol productivity in methane oxidation by in situ generated hydrogen peroxide at mild temperature (70°C). The catalyst was synthesized by fixation of AuPd alloy nanoparticles within aluminosilicate zeolite crystals, followed by modification of the external surface of the zeolite with organosilanes. The silanes appear to allow diffusion of hydrogen, oxygen, and methane to the catalyst active sites, while confining the generated peroxide there to enhance its reaction probability. At 17.3% conversion of methane, methanol selectivity reached 92%, corresponding to methanol productivity up to 91.6 millimoles per gram of AuPd per hour.
366 citations
TL;DR: With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improve the oxidation of toluene to CO2.
Abstract: Catalytic combustion technology is one of the effective methods to remove VOCs such as toluene from industrial emissions. The decomposition of an aromatic ring via catalyst oxygen vacancies is usually the rate-determining step of toluene oxidation into CO2. Series of CeO2 probe models were synthesized with different ratios of surface-to-bulk oxygen vacancies. Besides the devotion of the surface vacancies, a part of the bulk vacancies promotes the redox property of CeO2 in toluene catalytic combustion: surface vacancies tend to adsorb and activate gaseous O2 to form adsorbed oxygen species, whereas bulk vacancies improve the mobility and activity of lattice oxygen species via their transmission effect. Adsorbed oxygen mainly participates in the chemical adsorption and partial oxidation of toluene (mostly to phenolate). With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improves the oxidation of toluene to CO2.
175 citations
TL;DR: The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO6 in ABO3, which ultimately influences their reaction performance in chemical looping processes.
Abstract: Modulating lattice oxygen in metal oxides that conducts partial oxidation of methane in balancing C-H activation and syngas selectivity remains challenging. This paper describes the discovery of distorting FeO6 octahedra in La1-xCexFeO3 (x = 0, 0.25 0.5, 0.75, 1) orthorhombic perovskites for the promotion of lattice oxygen activation. By combined electrical conductivity relaxation measurements and density functional theory calculations studies, this paper describes the enhancement of FeO6 octahedral distortion in La1-xCexFeO3 promoting their bulk oxygen mobility and surface oxygen exchange capability. Consequently, La0.5Ce0.5FeO3 with the highest FeO6 distortion achieves exceptional syngas productivity of ∼3 and 8 times higher than LaFeO3 and CeFeO3, respectively, in CH4 partial oxidation step with simultaneous high CO2 conversion (92%) in the CO2-splitting step at 850 °C. The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO6 in ABO3, which ultimately influences their reaction performance in chemical looping processes.
152 citations
TL;DR: This work provides a facile and low-cost approach for the synthesis of functional biochar toward environmental remediation and deepens the understanding of biochar-catalyzed PMS activation and nonradical oxidation.
Abstract: Biochar is a promising candidate for the adsorptive removal of organic/inorganic pollutants, yet its role in metal-free catalyzed advanced oxidation processes still remains ambiguous. In this work, five biochar samples (PPBKx, where x represents the pyrolysis temperature) were prepared by using metal-enriched phytoremediation plant residue as the feedstock. Notably, PPBK exhibited a high specific surface area (as high as 1090.7 m2 g-1) and outstanding adsorption capacity toward ciprofloxacin (CIP, as much as 1.51 ± 0.19 mmol g-1). By introducing peroxymonosulfate (PMS, 5 mM) as the chemical oxidant, over 2 mmol g-1 CIP was synergistically adsorbed and oxidized within 30 min although PMS itself could not oxidize CIP efficiently, suggesting the formation of reactive oxidative species. Theoretical calculations revealed that PMS anions preferentially adsorbed on the activated C atoms adjacent to the graphitic N dopant, where the carbon matrix served as the electron donor, instead of as an electron mediator. The adsorbed PMS possessed a smaller molecular orbital energy gap, indicating that it was much easier to be activated than free PMS anions. Surface-bound reactive species were elucidated to be the dominant contributor through chemical quenching experiments and electrochemical characterizations. The catalytic activity of PPBK700 could be greatly retained in repeated oxidations because of the stable N species, which serve as the active catalytic sites, while the CIP adsorption was greatly deteriorated because of the diminishing active adsorption sites (carbon matrix edge) caused by the partial oxidation of PMS. This work not only provides a facile and low-cost approach for the synthesis of functional biochar toward environmental remediation but also deepens the understanding of biochar-catalyzed PMS activation and nonradical oxidation.
85 citations
TL;DR: Combined catalyst characterization, kinetic studies, and isotopic labeling experiments unveil that molecular O2 bonded to tri-coordinated BO3 centers on B2O3 surfaces acts as a judicious oxidant for methane activation with mitigated CO2 formation, even at high O2/CH4 ratios of the feed.
Abstract: Direct oxidation of methane to value-added C1 chemicals (e.g. HCHO and CO) provides a promising way to utilize natural gas sources under relatively mild conditions. Such conversions remain, however, a key selectivity challenge, resulting from the facile formation of undesired fully-oxidized CO2. Here we show that B2O3-based catalysts are selective in the direct conversion of methane to HCHO and CO (~94% selectivity with a HCHO/CO ratio of ~1 at 6% conversion) and highly stable (over 100 hour time-on-stream operation) conducted in a fixed-bed reactor (550 °C, 100 kPa, space velocity 4650 mL gcat−1 h−1). Combined catalyst characterization, kinetic studies, and isotopic labeling experiments unveil that molecular O2 bonded to tri-coordinated BO3 centers on B2O3 surfaces acts as a judicious oxidant for methane activation with mitigated CO2 formation, even at high O2/CH4 ratios of the feed. These findings shed light on the great potential of designing innovative catalytic processes for the direct conversion of alkanes to fuels/chemicals. Partial oxidation of methane to value-added C1 products remains challenging due to the favorable formation of fully-oxidized CO2. Here, the authors show supported B2O3 catalysts with tri-coordinated BO3 units as the active site are highly selective in oxidizing methane to HCHO and CO.
82 citations
06 Jan 2020
TL;DR: In this paper, a one-step electrochemical route at ambient temperature and pressure in aqueous media to the selective partial oxidation of ethylene to ethylene glycol was reported.
Abstract: There is significant interest in developing efficient electrochemical processes for commodity chemical manufacturing, all directly powered by renewable electricity. A vital chemical is ethylene glycol, with an annual consumption of around 20 million tonnes due to its use as antifreeze and as a polymer precursor. Here we report a one-step electrochemical route at ambient temperature and pressure in aqueous media to the selective partial oxidation of ethylene to ethylene glycol. Tuning of the catalyst OH binding energy was hypothesized to be crucial for facilitating the transfer of OH to *C2H4OH to form ethylene glycol. Computational studies suggested that a gold-doped palladium catalyst could perform this step efficiently, and experimentally we found it to exhibit an approximate 80% Faradaic efficiency to ethylene glycol, retaining its performance for 100 hours of continuous operation. These findings represent a significant advance in the development of selective anodic partial oxidation reactions in aqueous media under mild conditions. Ethylene glycol is a commodity chemical with an annual consumption of 20 million tonnes. Its production generates 1.6 tonnes of CO2 per tonne of ethylene glycol. To reduce these CO2 emissions, the authors report a one-step electrochemical route to selectively convert ethylene to ethylene glycol at ambient temperature and pressure in aqueous media.
79 citations
TL;DR: It is demonstrated that water, not dioxygen, is the main source of the oxygen present in the methanol produced in the partial oxidation of methane to meethanol over Cu-SSZ-13 in a continuous flow reactor.
Abstract: Direct oxidation of methane to methanol is a long-standing challenge in the heterogeneous catalysis community This Communication demonstrates that water, not dioxygen, is the main source of the oxygen present in the methanol produced in the partial oxidation of methane to methanol over Cu-SSZ-13 in a continuous-flow reactor This is confirmed by experiments performed in the absence of molecular oxygen and with the use of 18O-labeled water These findings should lead to new approaches for improving the partial oxidation properties of copper zeolites
62 citations
57 citations
TL;DR: In this article, a series of CuO/Ca2Fe2O5 with different contents of copper were prepared as the catalytic oxygen carrier (COC) which goes through the reduction → catalytic methanol conversion → re-oxidation.
Abstract: Auto-thermal reforming of methanol is an attractive route for low-temperature methanol conversion for hydrogen production. This paper describes utilization the lattice oxygen of Cu2O/Ca2Fe2O5 participates the partial oxidation of methanol to achieve the efficient auto-thermal reforming of methanol. ASPEN Plus software was adopted to verify the feasibility of auto-thermal conversion of methanol via Cu↔Cu2O looping and provided a comprehensive understanding of the associated process via operating parameter optimization. A series of CuO/Ca2Fe2O5 with different contents of copper were prepared as the catalytic oxygen carrier (COC) which goes through the reduction → catalytic methanol conversion →re-oxidation. The surface and bulk properties of COCs were characterized by XRD, XPS, TEM-EDS mapping, Raman, and H2-TPR; the reaction pathways were investigated using CH3OH-pulse and in situ DRIFTS. Results indicate that 40 % Cu-loaded Cu2O-Ca2Fe2O5 shows the highest catalytic activity of the synthesized COCs, and the presence of Ca2Fe2O5 tunes the redox activity and mobility of the lattice oxygen, obtaining a H2 production rate of 37.6 μmol·H2∙g−1·COC·s−1 at 240 °C. The reaction pathways of chemical looping methanol conversion follow the sequence: CH3OH full oxidation → formaldehyde intermediate → methyl-formate intermediate as the amount of lattice oxygen decreases gradually.
52 citations
TL;DR: In this article, a series of FeOOH/m-WO3 consisting of ordered mesoporous WO3 and highly dispersed amorphous FeOH were synthesized by using KIT-6 silica as hard template.
45 citations
TL;DR: In this article, a perovskite-based oxygen carrier (La0.85Sr0.15Fe0.95Al0.05O3-δ) was developed for the complete conversion of CH4 to a synthesis gas (a mixture of H2 and CO, selectivity > 99 %).
Abstract: Chemical looping can provide attractive alternative process routes in which solid oxygen carriers function as lattice oxygen transfer agents, for example for the partial oxidation of methane. We report on the development of a perovskite-based oxygen carrier (La0.85Sr0.15Fe0.95Al0.05O3-δ) that enables the complete conversion of CH4 to a synthesis gas (a mixture of H2 and CO, selectivity > 99 %) through donation of its lattice oxygen (up to 9 wt%) at temperatures > 900 °C. The thermodynamic properties of the oxygen carrier permit its lattice oxygen to be replenished with CO2 or H2O, of which > 94 % is converted into CO or H2, respectively. The potential of this compositionally and structurally flexible oxygen carrier is demonstrated in a continuous experiment lasting more than 45 days (∼ 4050 redox cycles), in which all CH4 (reductant) and all CO2 (oxidant) is converted into a synthesis gas without CO2 contamination.
TL;DR: In this paper, a 3D Ti3AlC2 MAX/TiO2 composite was designed and fabricated over a monolithic support for hydrogen-rich syngas production, and the performance of structured composite tested in methane steam reforming (MSR), methane dry reforming (MDR) and methane bi-reforming (MBR) reveals 1.2 and 1.6 folds higher activity in MBR than using MDR and MSR, respectively.
Abstract: Design and fabrication of three dimensional Ti3AlC2 MAX/TiO2 composite immobilized over monolithic support was obtained through sol-gel approach. With partial oxidation and incorporation of Ti3AlC2 essentially promotes light absorption, charge transfer and extends photo-induced charge carrier lifetime. The highest CO yield of 1566 μmol g-cat−1 was obtained over Ti3AlC2 MAX/TiO2, being 6.8 folds higher than pure TiO2 NPs. Performance of structured composite tested in methane steam reforming (MSR), methane dry reforming (MDR) and methane bi-reforming (MBR) reveals 1.2 and 1.6 folds higher activity in MBR than using MDR and MSR, respectively. Similarly, quantum yield in a monolith photoreactor was 3.5 folds higher than using a fixed-bed system. This divulges that MBR gave proficient oxidation and reduction reactions in electron-rich 3D MAX structure, whereas, monolith photoreactor provides larger photon-energy consumption with improved sorption process to boost production of CO and H2 with enhanced stability. Thus, this work demonstrated 3D Ti3AlC2 MAX/TiO2 a promising catalyst and monolith photoreactor an efficient photon flux harvesting system for boosting hydrogen rich syngas production.
TL;DR: Observations are important for understanding the methane partial oxidation mechanism and for the rational design of the active materials for this reaction.
Abstract: The reaction of methane with copper-exchanged mordenite with two different Si/Al ratios was studied by means of in situ NMR and infrared spectroscopies. The detection of NMR signals was shown to be possible with high sensitivity and resolution, despite the presence of a considerable number of paramagnetic CuII species. Several types of surface-bonded compounds were found after reaction, namely molecular methanol, methoxy species, dimethyl ether, mono- and bidentate formates, CuI monocarbonyl as well as carbon monoxide and dioxide, which were present in the gas phase. The relative fractions of these species are strongly influenced by the reaction temperature and the structure of the copper sites and is governed by the Si/Al ratio. While methoxy species bonded to Bronsted acid sites, dimethyl ether and bidentate formate species are the main products over copper-exchange mordenite with a Si/Al ratio of 6; molecular methanol and monodentate formate species were observed mainly over the material with a Si/Al ratio of 46. These observations are important for understanding the methane partial oxidation mechanism and for the rational design of the active materials for this reaction.
TL;DR: The opportunity to tune the catalytic activity of MOFs for redox reactions by changing their metal node composition is demonstrated by changing the composition of the trimetallic node.
Abstract: Density functional theory is used to study the tunability of trigonal prismatic SBUs found in metal–organic frameworks (MOFs) such as MIL-100, MIL-101, and PCN-250/MIL-127 of chemical composition M...
TL;DR: In this paper, a direct conversion of methane to methanol has been a long-sought objective and partial oxidation by thermal catalysis is possible but suffers from a rapid loss in methanoline selectivity with increasing temperature.
Abstract: Direct conversion of methane to methanol has been a long-sought objective. Partial oxidation by thermal catalysis is possible but suffers from a rapid loss in methanol selectivity with increasing m...
TL;DR: In this article, the promoting effects of Ce3+ substitution into LaFeO3 redox catalysts on thermochemical H2O splitting as well as partial oxidation of methane are presented.
TL;DR: In this paper, an extended chemical kinetics mechanism was developed that also covers extremely fuel-rich conditions of methane/dimethyl ether mixtures, which is shown to predict well the ignition delay time and species concentration evolution measurements presented in this paper.
TL;DR: In this paper, a new Ni-based catalyst (Ni/MoO2@Mo2CTx) with extraordinary catalytic performance in the HDO of palmitic acid was designed.
TL;DR: In this article, a novel asymmetric membrane reactor incorporated with a catalyst layer of enriched oxygen vacancy was designed for direct partial oxidation (DPO) of methane to syngas.
TL;DR: In this paper, the effect of metal nitrate/urea ratio on the structure phase, crystallinity and morphology of the synthesized materials was investigated in catalytic partial oxidation of methane (CPOM).
TL;DR: In this paper, the Gibbs free energy minimization approach was employed to study the tuning of syngas H2/CO ratio appropriate for downstream Fischer-Tropsch synthesis (FTS).
TL;DR: Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 ¾wt% Ni and 20 ¾% CeO2 were prepared by microwave assisted (co) precipitation method as discussed by the authors.
TL;DR: In this paper, a single atom alloy configuration of a Pd atom adsorbed on Cu (1.1) surface is proposed (A-Pd/Cu(1.5) ).
TL;DR: In this paper, a CO-assisted direct conversion of methane into C1 and C2 oxygenates was demonstrated over ZSM-5 supported transition and platinum group metal catalysts.
Abstract: Conversion of methane towards chemical feedstocks such as oxygenates and hydrocarbons has been studied along with the development of natural gas technology. In this study, CO‐assisted direct conversion of methane into C1 and C2 oxygenates was demonstrated over ZSM‐5 supported transition and platinum group metal catalysts. Besides previously investigated Rh, other platinum group metals (e. g., Ru and Ir) were found to be a potential element as the catalyst. Presence of CO was critical for the reaction, which would work as a ligand, a reductant, and a reactant. On the other hand, the competing undesired CO oxidation toward CO2 was found to be the major issue. Partial oxidation toward methanol or formic acid (C1 oxygenates formation) was parallel to oxidative carbonylation to acetic acid (C2 oxygenate formation).
TL;DR: The fibrous M/KCC-1 (M = Ru, Pd, Rh) catalysts prepared by microwave-assisted hydrothermal approach were investigated for methane partial oxidation (MPO) reaction at stoichiometric CH4/O2 feed ratio and temperature of 500-800°C as mentioned in this paper.
TL;DR: In this article, a Ni-Fe alloy composite catalyst was prepared by reducing perovskite La0.7Sr0.3Fe0.8Ni0.2O3-δ (LSFN) and then evaluated its catalytic activity in the partial oxidation of CH4.
TL;DR: In this article, a multi-stage downdraft gasifier with three air inlets in the zone of pyrolysis, oxidation, and reduction was used to suppress tar.
TL;DR: In this paper, a comprehensive study was conducted on the application of various MeAl2O4 spinels as the catalyst support for the preparation of nickel-based catalysts in the combined dry reforming and partial oxidation.
TL;DR: The catalytic supercritical water partial oxidation of phenol using H2O2 as oxidant in the presence of NaOH was explored to enhance hydrogen production and inhibit phenol polymerization and indicated that H2 production was enhanced when phenol super critical water oxidation was controlled at a lower O/C ratio.
TL;DR: In this article, Fe ions with different amount were incorporated into a novel garnet structure (Y3FexAl5-xO12), which exhibited drastically increased CH4 conversion with reduction time.
Abstract: Fe-based oxygen carries (OCs) have attracted wide attention due to the low cost and environmental compatibility for chemical looping methane partial oxidation. However, they usually suffer from low CH4 reactivity mainly due to insufficient synergy between catalytic CH4 activation and lattice oxygen mobility. In this work, Fe ions with different amount were incorporated into a novel garnet structure (Y3FexAl5-xO12), which exhibited drastically increased CH4 conversion with reduction time. This resulted from in-situ formed Fe0 sites at the early stage of reduction, which led to a more efficient reaction route involving methane catalytic decomposition on Fe0 and the resulted carbon oxidation easier by lattice oxygen, compared with methane directly oxidized by OCs. Moreover, the amount of Fe ions in garnet influenced surface exposed Fe0 sites and oxygen mobility, inducing Y3Fe2Al3O12 performed the best with almost 94 % methane conversion thanks to the combined advantages of larger surface exposed Fe0 and higher lattice oxygen mobility.