Partial Oxidation Research Articles

Autothermal hydrogen release from liquid organic hydrogen carrier systems

A typical feature that the LOHC technology shares with other types of chemical hydrogen storage is that the release of hydrogen from the carrier requires an input of heat. In many use cases where waste heat from external sources is not available (e.g. in heavy-duty mobility), this is seen as a major drawback. In this paper, we show that autothermal LOHC dehydrogenation offers a very attractive way to overcome this drawback. In detail, we demonstrate autothermal hydrogen release from dicyclohexylmethane using diphenylmethane oxidation to benzophenone as source of heat. The full storage cycle involves benzophenone hydrodeoxygenation to dicyclohexylmethane, dicyclohexylmethane dehydrogenation to diphenylmethane, and diphenylmethane oxidation to benzophenone. We studied both the individual reaction steps using pure feedstocks and the integral cycle in which the intermediates and by-products of each reaction remain in the system for the subsequent reaction step. Although no efforts have yet been made to develop special catalyst materials for this purpose, the results with the applied commercial hydrodeoxygenation (Pd/C), dehydrogenation (Pt on alumina) and partial oxidation (VOx/TiO2) catalysts are already very promising. The storage cycle can be closed with high selectivity and with only minor total oxidation losses. The proposed concept of autothermal LOHC dehydrogenation offers the potential to increase the amount of useable hydrogen from a given amount of charged hydrogen carrier by up to 30%.

Sulfur-containing cellulose esters for selectively anchoring gold for water catalytic decontamination

The facile preparation of sustainable sulfur-containing polymer functional materials has been obtained great attention due to their chemical reactivity and metal complexing ability. In this study, taking the solution properties advantages of the newly developed cellulose solvent system of DBU/DMSO/CO2, thiol and disulfide bond functionalized cellulose ester (TDSCE) was facilely prepared via in-situ tandem transesterification and oxidation reaction by using methyl 3-mercaptopropionate, without adding any external catalyst. The synthetic protocol was featured by that the DBU not only acted as reagent for the dissolution of cellulose, but also catalysts for the transesterification of cellulose with methyl 3-mercaptopropionate to yield cellulose 3-mercaptopropionate (Cell-MP) with maximum degrees of substitution (DS) of 0.77, and an oxidant for the partial oxidation of Cell-MP to produce a cellulose methyl 3,3′-disulfanediyldipropionate (Cell-MDSP) with maximum DS of 0.36 mixed ester, respectively. With successful introduction of thiol and disulfide bond into the cellulose backbone, the TDSCEs indicated desirable selective absorption of Au3+ from mimic heavy mental ions waste water due to the sulfur-Au chemistry with maximal adsorption capacity for Au3+ of 415.2 mg/g. The subsequent reduction of Au3+ into gold nanoparticles (Au NPs) fabricated a robust TDSCE-2@Au NPs composite catalyst with high catalytic activity for the hydrogenation treatment of water pollutes, such as 4-nitrophenol (4-NP)and azo dyes.

The Switching of the Type of a ROS Signal from Mitochondria: The Role of Respiratory Substrates and Permeability Transition

Flashes of superoxide anion (O2−) in mitochondria are generated spontaneously or during the opening of the permeability transition pore (mPTP) and a sudden change in the metabolic state of a cell. Under certain conditions, O2− can leave the mitochondrial matrix and perform signaling functions beyond mitochondria. In this work, we studied the kinetics of the release of O2− and H2O2 from isolated mitochondria upon mPTP opening and the modulation of the metabolic state of mitochondria by the substrates of respiration and oxidative phosphorylation. It was found that mPTP opening leads to suppression of H2O2 emission and activation of the O2− burst. When the induction of mPTP was blocked by its antagonists (cyclosporine A, ruthenium red, EGTA), the level of substrates of respiration and oxidative phosphorylation and the selective inhibitors of complexes I and V determined the type of reactive oxygen species (ROS) emitted by mitochondria. It was concluded that upon complete and partial reduction and complete oxidation of redox centers of the respiratory chain, mitochondria emit H2O2, O2−, and nothing, respectively. The results indicate that the mPTP- and substrate-dependent switching of the type of ROS leaving mitochondria may be the basis for O2−- and H2O2-selective redox signaling in a cell.

Catalytic methanol cracking to hydrogen and formaldehyde over heterogeneous catalysts by radiolysis: Sectoral industrial symbiosis by waste radiation utilisation

In order to create a sustainable, carbon-neutral society, it is of utmost importance to link the energy sector with the chemical industry. Radiation from nuclear power plants proves to be useful for H2 production from water or carriers such as methanol. In our study, we investigated the potential for the production of hydrogen and formaldehyde by endothermic radiolytic cracking of 50 mol% aqueous methanol, which can be produced by direct CO2 hydrogenation without distillation. We developed an elegant experimental setup and performed irradiation tests in the TRIGA reactor with system analysis by GC-MS (gas chromatography with mass spectroscopy), SEM-EDS (scanning electron microscopy with energy dispersive spectroscopy), XRD (X-ray powder diffraction) and Monte Carlo simulations of radiation absorption. Among the different routes tested, a semiconductor-based photocatalytic material (TiO2) increased the H2 yield by 24%. In the critical evaluation of radiation utilisation, spent fuel radiation sources were found to be promising as they require low heat exchange and could produce 3600 kg H2/day in a single spent fuel pool. The advantage of radiolytic methanol cracking lies in its ability to produce formaldehyde and hydrogen (∼53% methanol value increase), whereas conventional partial oxidation of methanol with O2 for formaldehyde production (only ∼31% methanol value increase) inevitably produces water, which reduces the overall energy efficiency.

Improved Catalytic Partial Oxidation of Methane via Lattice Oxygen Modification on Supported Copper Oxide Catalyst System

AbstractThirteen kinds of supported copper oxide catalysts (Cu/MOx, MOx: La2O3, Al2O3, SiO2, TiO2, CeO2, ZrO2, SnO2, SrCO3, BaCO3, Ta2O5, Nb2O5, WO3, and MoO3), which form Cu−O−M sites at the interface between CuOx and MOx or within the complex oxides (CuMOx), were tested for CH4 partial oxidation to find out catalytically active Cu−O−M combinations for production of CH3OH and HCHO. Among the thirteen Cu/MOx tested, Cu/WO3 exhibited the highest total yield of CH3OH and HCHO in a CH4‐O2‐H2O flow reaction at 400 °C. The structural and property analysis of Cu/WO3 revealed the formation of CuWO4, of which the lattice oxygen is active for the partial oxidation of CH4.

Oxygen vacancy induced defect dipoles in BiVO4 for photoelectrocatalytic partial oxidation of methane

A strong driving force for charge separation and transfer in semiconductors is essential for designing effective photoelectrodes for solar energy conversion. While defect engineering and polarization alignment can enhance this process, their potential interference within a photoelectrode remains unclear. Here we show that oxygen vacancies in bismuth vanadate (BiVO4) can create defect dipoles due to a disruption of symmetry. The modified photoelectrodes exhibit a strong correlation between charge separation and transfer capability and external electrical poling, which is not seen in unmodified samples. Applying poling at −150 Volt boosts charge separation and transfer efficiency to over 90%. A photocurrent density of 6.3 mA cm−2 is achieved on the photoelectrode after loading with a nickel-iron oxide-based cocatalyst. Furthermore, using generated holes for methane partial oxidation can produce methanol with a Faradaic efficiency of approximately 6%. These findings provide valuable insights into the photoelectrocatalytic conversion of greenhouse gases into valuable chemical products.

Partial‐Oxidation Enabling Homologous Ru/RuO2 Heterostructures With Proper d‐Dand Center as Efficient and Durable Cathode Catalysts for Ultralong Cycle Life in Li–O2 Batteries

AbstractThe sluggish cycle kinetics is one of the major obstacles to the commercial application of Li–O2 batteries (LOBs), despite their large theoretical energy density. Efficient and long‐term durable cathode catalysts are urgently desired to strengthen their cycle stability and rate performance. Density functional theory calculations reveal that Ru/RuO2 Mott–Schottky heterostructures can manipulate the adsorption capacities of intermediates by modulating the d‐band center and redistribute interfacial charges, enabling efficient redox kinetics, reducing overpotentials, and optimizing the growth pathway of discharge products. Herein, a wet impregnation approach followed by partial oxidization of Ru nanodots to construct homologous Ru/RuO2 heterostructures as advanced cathode catalysts for boosting the electrochemical activities of LOBs is employed. They exhibit superior electrochemical performance, including high discharge specific capacity (17 120 mAh g−1 at 200 mA g−1), small overpotential (0.96 V), and ultralong cycle lifetime of 1209 cycles (>2400 h) at 500 mA g−1. Over 1260‐h stable cycle in air atmosphere at 500 mA g−1 demonstrates the potential application prospects of the Ru/RuO2 heterostructures in Li‐air batteries. Multiple ex/in situ measurements and theoretical calculation are conducted to investigate the optimizing mechanism of electrochemical performances.

Molybdenum Disulfide-Based Catalysts in Organic Synthesis: State of the Art, Open Issues, and Future Perspectives.

In the field of heterogeneous organic catalysis, molybdenum disulfide (MoS2) is gaining increasing attention as a catalytically active material due to its low toxicity, earth abundance, and affordability. Interestingly, the catalytic properties of this metal-based material can be improved by several strategies. In this Perspective, through the analysis of some explicative examples, the main approaches used to prepare highly efficient MoS2-based catalysts in relevant organic reactions are summarized and critically discussed, namely: i) increment of the specific surface area, ii) generation of the metallic 1T phase, iii) introduction of vacancies, iv) preparation of nanostructured hybrids/composites, v) doping with transition metal ions, and vi) partial oxidation of MoS2. Finally, emerging trends in MoS2-based materials catalysis leading to a richer organic synthesis are presented.

Dual modification of starch: Synergistic effects of ozonation and pulsed electric fields on structural, rheological, and functional attributes

Study evaluated the influence of ozonization (O3) time combined with pulsed electric fields (PEF) on the modification of bean starch structure. O₃ was used at a concentration of 0.045 g/L for 60 min (Oz1) and 120 min (Oz2) both individually and in combination with 30 kV/cm (P30). Carbonyl content was higher than the carboxyl content, especially with prolonged treatment times (Oz2), indicating partial oxidation. Additionally, higher levels of amylose and degrees of polymerization (DP ≥ 37 and DP 25–36) were observed in the oxidized starches, with significant changes only when combined with PEF. The main morphological and structural modifications included the presence of agglomerates, partial gelatinization, reduced crystallinity, and lower IR1047/1022 in the granules treated with PEF + O3. Oxidized starches exhibited higher solubility, resulting in lower values for rheological parameters, with PEF + 2 h of O3 (Oz2P) standing out. It can be used as prebiotics, controlled release agents and a texturizer for gluten-free foods.

Gas sensing properties of Ti0.2V1.8CTx/V2O5 nanocomposite

A method for the preparation of nanocomposite containing Ti0.2V1.8CTx MXene core and titanium-doped vanadium oxide surface layers as a result of relatively low-temperature partial oxidation of MXene multilayer - two-dimensional vanadium-titanium carbide has been developed. It is shown that during oxidation in air atmosphere of initial Ti0.2V1.8CTx at temperature 250°С, in general, the microstructure of accordion-like aggregates with some increase in porosity of their constituent layers and increase in their thickness due to the formation of V2O5 is preserved. At the same time, preservation of the MXene structure with a decrease in the interplanar spacing from 10.3 (initial powder Ti0.2V1.8CTx) to 7.3 Å was observed. Raman spectroscopy confirmed the formation of vanadium oxide. Kelvin-probe force microscopy data revealed that the formation of Ti0.2V1.8CTx/V2O5 nanocomposite results in a decrease in the work function from 4.88 (Ti0.2V1.8CTx) to 4.68 eV. The chemosensor properties towards a range of gaseous analytes (H2, CO, NH3, NO2, C6H6, C3H6O, CH4, C2H5OH and O2) have been comprehensively studied for Ti0.2V1.8CTx/V2O5 layers coated using the microplotter printing. At increased detection temperatures (125–200°С), high sensitivity to oxygen (10% O2) and NO2 (100 ppm) is observed; there are notable responses to humidity (50% RH) throughout the 25–200°С temperature range. At room temperature, good response to acetone, ethanol and ammonia is observed.

Harnessing in-situ oxidation of nanostructured mxene to modulate the electronic structure for improved selectivity for electrochemical carbon dioxide reduction

The electrochemical CO2 reduction reaction (CO2RR) is a promising approach to valorizing CO2. Ti3C2TX as a support material has received significant interest in enhancing CO2RR performance for tuning the electronic structure. However, there has been relatively less focus on changes to the Ti3C2TX electronic structure induced by loading catalysts onto the Ti3C2TX. Because Ti3C2TX has an intrinsic activity for both CO2RR and the competitive hydrogen evolution reaction (HER), electronic structure changes can affect the balance between CO2RR and HER selectivity. Therefore, tuning the electronic structure of Ti3C2TX can control the competition between CO2RR and HER and tune the selectivity and activity. Herein, we report that Ti3C2TX’s electronic structure can be tuned by the Ag+ loading method via redox interactions, tuning the reaction selectivity and activity for CO2RR. To illustrate this effect, we compare the CO2RR performance of in-situ formed Ag nanoparticles (NPs) on Ti3C2TX (0.9Ag-IS-Ti3C2TX) with physically mixed Ag NPs and Ti3C2TX (0.9Ag/P/Ti3C2TX). Here, ‘0.9’ refers to the molar ratio between Ag precursor and Ti3C2Tx, and ‘IS’ vs. ‘P’ refers to in-situ formed vs. physically mixed Ag NPs. 0.9Ag-IS-Ti3C2TX demonstrates a higher oxidation state for Ti and a higher proportion of Ti-O bonds than 0.9Ag/P/Ti3C2TX. Compared to 0.9Ag/P/Ti3C2TX, 0.9Ag-IS-Ti3C2TX exhibits higher CO Faradaic efficiency (FE), rising from 8.1 % with a partial current density of −2.0 mA cm−2 to 49.6 % with a partial current density of −20.1 mA cm−2 at −1.4 V vs. RHE (reversible hydrogen electrode). To harness this effect, we demonstrate control over the CO: H2 ratio of syngas formed from CO2RR over our Ti3C2TX-supported catalysts. Further electrochemical anodic oxidation experiments reveal the critical oxidation potential of Ti3C2TX (0.8 V vs. RHE) and show that HER can be partially suppressed by partial oxidation of Ti3C2TX. This work highlights the importance of considering the changes in Ti3C2TX (and other) supports when supporting catalysts for CO2RR and other electrochemical reactions.

Experimental Investigation on Compact Current Non Thermal Plasma Assisted Hydrocarbon Reforming Hydrogen Rich Gas

On-board vehicle hydrogen-rich gas extraction of gasoline reforming utilizing for fuel cells and GDI-engine lean burn combustion enhancement NOx trap applications. A non-thermal plasma discharge electrode that produces a reduce current, increased voltage 15kV source arc plasma fuel reformer is designed to operate at an arc frequency of 50 Hz. The operating factors gasoline equivalence ratio between 4 and 6.and electronically control by the fuel injector and eliminating ground spark plug plasma arc generation. The plasma arc non-thermal reformer gasoline converted into gas that contains partial oxidation contains combustible gases like hydrogen (H2), CO, non-combustible gases like CO2, N2, and a small quantity of H2O. The nonthermal plasma technology alternative for on-board hydrogen vehicle applications.

Polydopamine‐Mediated Contact‐Electro‐Catalysis for Efficient Partial Oxidation of Methane

The direct conversion and efficient utilization of methane pose a critical scientific challenge. Indirect activation via reactive oxygen species (ROS) offers a high probability of contact with methane and conversion efficiency under mild conditions. However, reported product yields are suboptimal due to challenges in activating oxygen and facilitating mass transfer in suspension systems. We propose the use of contact‐electro‐catalysis (CEC), employing polydopamine (PDA) as a catalyst that undergoes electron transfer with oxygen under ultrasound, generating ROS that drives the partial oxidation of methane (POM). Corresponding experimental results indicate that CH3OH and most HCHO are produced directly from CH4. Furthermore, through in situ characterizations, we have shown that light pretreatment of the catalysts in an oxygenated atmosphere facilitates the forming of more C=O functional groups with strong electron‐withdrawing properties, thereby significantly enhancing overall product yields, particularly for CH3OH. Within two hours, product yields reach 1.5 mmol·gcat−1 for HCHO and 0.9 mmol·gcat−1 for CH3OH. This work introduces a novel approach for efficient POM, while highlighting the distinctive catalytic properties of PDA.

Polydopamine-Mediated Contact-Electro-Catalysis for Efficient Partial Oxidation of Methane.

The direct conversion and efficient utilization of methane pose a critical scientific challenge. Indirect activation via reactive oxygen species (ROS) offers a high probability of contact with methane and conversion efficiency under mild conditions. However, reported product yields are suboptimal due to challenges in activating oxygen and facilitating mass transfer in suspension systems. We propose the use of contact-electro-catalysis (CEC), employing polydopamine (PDA) as a catalyst that undergoes electron transfer with oxygen under ultrasound, generating ROS that drives the partial oxidation of methane (POM). Corresponding experimental results indicate that CH3OH and most HCHO are produced directly from CH4. Furthermore, through in situ characterizations, we have shown that light pretreatment of the catalysts in an oxygenated atmosphere facilitates the forming of more C=O functional groups with strong electron-withdrawing properties, thereby significantly enhancing overall product yields, particularly for CH3OH. Within two hours, product yields reach 1.5 mmol·gcat-1 for HCHO and 0.9 mmol·gcat-1 for CH3OH. This work introduces a novel approach for efficient POM, while highlighting the distinctive catalytic properties of PDA.

Investigating the Effect of Ammonia Addition on the Performance of a Heavy-Duty Natural Gas Spark Ignition Engine Operated at Stoichiometric Conditions

Abstract Due to the pressing issue of global warming, there has been a significant focus on zero- and low-carbon fuels globally. Among hydrocarbon fuels, methane is widely used in spark ignition engines due to its abundance and relatively low carbon footprint. However, to further reduce carbon emissions, interest is growing in the use of ammonia, a zero-carbon fuel, as a partial replacement for methane. Consequently, it is crucial to investigate the impact of ammonia addition on the performance of natural gas spark ignition engines. A key challenge in studying ammonia-methane engines is that the introduction of ammonia alters the formation mechanisms of nitrogen-based pollutants, resulting in the coupling of fuel-borne and air-borne nitrogen pollutants. As a result, research on the nitrogen-based emissions of ammonia-methane engines has been limited. This study addresses this issue by differentiating between atmospheric nitrogen and fuel nitrogen elements, effectively decoupling fuel-borne and air-borne nitrogen pollutants. This approach provides valuable insights into the effects of ammonia addition on the nitrogen-based pollutant characteristics of natural gas engines. The results indicate that ammonia addition introduces N2O, a species absent in pure methane engines. The N2O primarily originates from cold wall regions and the partial oxidation of ammonia released from engine crevices during the late oxidation process. Although NO remains the dominant nitrogen-based pollutant and the amount of N2O is small, the significant greenhouse gas potential of N2O warrants further attention. Furthermore, while ammonia addition increases the NO concentration in the burning zone, it slightly reduces the NO concentration at chemical equilibrium under stoichiometric conditions. As a result, engines operating with an ammonia energy substitution ratio of 0.4 exhibit lower NOx emissions compared to those fueled solely by methane. These findings underscore the need for further research into the combustion and emission characteristics of ammonia-methane spark ignition engines.

A New Life for Tionite Industrial Waste: Regeneration Strategy towards Photocatalytic Applications.

Industrial waste management is an urgent problem to solve possibly by recycling, reuse and recovery of resources. In this framework, the sludge of the TiO2manufacturing, called tionite, is of certain interest because it contains metallic oxide-bearing impurities, dangerous to the environment. Hence, we propose a strategy to recover TiO2from tionite, towards its effective re-use as a photocatalyst. In detail, tionite was treated under acidic or alkaline conditions to remove impurities and improve the TiO2accessibility, and each single purification step was monitored by a thorough multi-technique characterization. The photocatalytic activity of the modified tionite materials was tested for the partial oxidation of ferulic acid to vanillin, a relevant sustainable green reaction, being vanillin an industrially relevant high added value compound and ferulic acid an abundant component of lignin present in industrial waste. All the tionite catalysts have shown significant efficiency in terms of vanillin selectivity respect to the benchmark TiO2P25. In particular, the sample treated under acidic conditions showed the best performances, due to specific interaction between the organic substrates and the catalyst. Results demonstrated that an industrial waste such as tionite can be valorized by proposing a tailored regeneration strategy.

Ti3C2Tx-MXene based 2D/3D Ti3C2–TiO2–CuTiO3 heterostructure for enhanced pseudocapacitive performance

Ti3C2Tx MXene family is a promising electrode material for electrochemical energy storage, but it suffers from insufficient pseudocapacitive charge storage because of self-aggregation and oxidation degradation. To resolve the issue, this paper proposes a two-step process for synthesizing oxidation-controlled MXene-derived 2D/3D heterostructures that beneficially utilize oxidation and simultaneously improve conductivity. The first step generates in-situ 3D floral Ti3C2– TiO2 nanoribbons under partial oxidation of MXene. As the second step, further controlled oxidation with Cu ions transforms the 3D floral Ti3C2–TiO2 nanoribbons into 2D/3D Ti3C2–TiO2–CuTiO3 heterostructure. Leveraging the synergistic effects of MXene, TiO2, and CuTiO3, this 2D/3D heterostructure enhances the interlayered spacing, redox-active site concentration and alleviates low conductivity issue associated with TiO2 nanoribbons. At 2 mA/cm2, the proposed 2D/3D Ti3C2–TiO2–CuTiO3 heterostructure achieved a significantly higher capacitance of 599.2 mF/cm2, compared to MXene with a capacitance of 249.16 mF/cm2 and 3D floral Ti3C2–TiO2 nanoribbons with 498.5 mF/cm2. For practical evaluation, an asymmetric supercapacitor (ASC) device (Ti3C2–TiO2–CuTiO3//AC) was fabricated, which exhibited an energy density of 31.1 Wh/kg, power density of 1041.7 W/kg and capacitance retention of 83.7 % after 5000 continuous charging/discharging cycles. It opens new avenues for utilizing controlled oxidation to enhance pseudocapacitive properties.

Iron Oxide Clusters as Electron Donors Under Light Enhance Oxygen Reduction Kinetics at Atomically Dispersed Fe for Photocatalytic CH4 Partial Oxidation.

Photocatalytic CH4 oxidation to CH3OH emerges as a promising strategy to sustainably utilize natural gas and mitigate the greenhouse effect. However, there remains a significant challenge for the synthesis of methanol by using O2 at low temperature. Inspired by the catalytic structure in soluble methane monooxygenase (MMO) and the corresponding reaction mechanism, we prepared a biomimetic photocatalysts with the decoration of Fe2O3 nanocluster and satellite Fe single atom immobilized on carbon nitride. The catalyst demonstrates an excellent CH3OH productivity of 5.02 mmol·gcat-1·h-1 with methanol selectivity of 98.5%. Mechanism studies reveal that the synergy between Fe2O3 nanocluster and Fe single atom establishes a dual-Fe site as MMO for O2 activation and subsequent CH4 partial oxidation. Moreover, the light excitation of Fe2O3nanoclusters with a relative narrow bandgap could deliver the electrons and protons to atomic Fe that facilitating the oxygen reduction kinetics for the robust of methanol synthesis.

Iron Oxide Clusters as Electron Donors Under Light Enhance Oxygen Reduction Kinetics at Atomically Dispersed Fe for Photocatalytic CH4 Partial Oxidation

Iron Oxide Clusters as Electron Donors Under Light Enhance Oxygen Reduction Kinetics at Atomically Dispersed Fe for Photocatalytic CH4 Partial Oxidation

The Performance of Ethylene Partial Oxidation on Group IB Metal Stepped Surfaces

Group IB metal catalysts, particularly Ag, Au, and Cu, exhibit particular selectivity for ethylene oxide (EO) formation, while Ag demonstrating the highest performance so far. Previous studies have explored the EO formation mechanism on (100) and (111) surfaces of group IB metals, but the reaction mechanism on the (211) facet (analogous to the edge sites of a catalyst particle) remains poorly understood. Herein, we fill in the knowledge gap by analyzing ethylene partial oxidation to EO on the (211) surfaces of Ag, Au, and Cu through density functional theory (DFT) calculations, scaling relationship analysis, and microkinetic modeling. Our study demonstrates that the (211) surface decreases the energy barrier for the dissociation of oxygen molecules into oxygen atoms, while unfavorable for the production of EO. Therefore, we should preserve an appropriate concentration of (211) surface on the nanoparticles when designing catalysts for the ethylene epoxidation reaction.