Conversion Routes Research Articles

Production of capsaicinoid nonivamide from plant oil and vanillylamine via whole-cell biotransformation

Capsaicinoids are mostly derived from chili peppers and have widespread applications in food, feed, and pharmacology. Compared with plant extraction, the use of microbial cell factories for capsaicinoids production is considered as a more efficient approach. Here, the biotransformation of renewable plant oil and vanillylamine into capsaicinoid nonivamide was investigated. Nonivamide biosynthesis using nonanoic acid and vanillylamine as substrates was achieved in Escherichia coli by heterologous expression of genes encoding amide-forming N-acyltransferase and CoA-ligase. Through increasing nonanoic acid tolerance of chassis cell, screening key enzymes involved in nonivamide biosynthesis and optimizing biotransformation conditions, the nonivamide titer reached 0.5 g/L. By further integrating a route for conversion of oleic acid to nonanoic acid, nonivamide biosynthesis was finally achieved using olive oil and vanillylamine as substrates, yielding a titer of approximately 10.7 mg/L. Results from this study provide valuable information for constructing highly efficient cell factories for the production of capsaicinoid compounds.

H2SO4 assisted hydrothermal conversion of biomass with solid acid catalysis to produce aviation fuel precursors

With hydrothermal reaction, lignocellulosic biomass can be efficiently converted into furfural (FF) and levulinic acid (LA), both of which are key platform compounds that can be used for the subsequent preparation of aviation fuels. In order to reduce the acid concentration in traditional hydrolysis and provide a reaction system with good catalytic activity, we propose a biomass conversion route as dilute acid hydrolysis coupled with solid acid catalysis. Firstly, at different temperatures, the hemicellulose and cellulose in corn stover were step-hydrolyzed by sulfuric acid solution with a concentration of 0.9 wt.% to produce xylose and glucose, with conversion reaching 100% and 97.3%, respectively. Subsequently, a new resin-derived carbon-based solid acid catalyst was used to catalyze the aforementioned saccharide solutions to obtain FF with yield of 68.7 mol% and LA of 70.3 mol%, respectively. This work provides a promising approach for the efficient production of bio-aviation fuel precursors.

Fuel phase extraction from pyrolytic liquid of Azadirachta indica biomass followed by subsequent characterization of pyrolysis products

Growing concerns over fossil fuel utilization and their impending scarcity have spurred a transition towards renewable energy sources. Among these, biomass has gained remarkable traction due to its widespread availability and adaptability. Pyrolysis, amid various biomass conversion routes, boasts advantages like moderate operating conditions, facile handling and efficient product distribution. Nonetheless, the commercialization of pyrolysis faces hurdles. A key challenge involves extracting the fuel phase from raw bio-oil. While numerous studies focus on biomass pyrolysis, comprehensive examinations of fuel phase extraction and subsequent characterization remain limited. Thus, this research concentrates on extracting the fuel phase from pyrolysis oil generated via the lesser-explored Azadirachta indica biomass followed by subsequent characterization. Dichloromethane and n-hexane were the solvents employed at four different volume percentages (10%, 20%, 30% and 40%) as solvents relative to raw bio-oil. The n-hexane emerged as a superior choice based on density, dynamic viscosity, calorific value and selectivity. The pinnacle achievement lies in the fuel phase extracted using 30 and 40 vol. % n-hexane, exhibiting physiochemical comparability to conventional gasoline. For instance, calorific values ranged between 29.1 and 37.1 MJ/kg for n-hexane-extracted fuel phases, compared to 15.1–19.6 MJ/kg for dichloromethane-extracted ones. Fourier-Transform-Infrared spectroscopy unveiled aliphatic compounds, ketones, aromatics, t-butyl compounds, alcohols, hydrocarbons and carboxylic acids. Gas-Chromatography-Mass-Spectroscopy highlighted furan, 2-methoxy- and ethanol, pentamethyl as principal compounds. Energy density of biochar and non-condensable gases stood at 28.5 MJ/kg and 14.9 MJ/Nm3, respectively. Non-condensable gases comprised of 15.9% H2, 26.7% CO, 23.8% CH4 and 33.6% CO2.

Relay Catalysis for Highly Selective Conversion of Methanol to Ethylene in Syngas.

The precise C-C coupling is a challenging goal in C1 chemistry. The conversion of methanol, a cheap and easily available C1 feedstock, into value-added and largely demanded olefins has been playing a game-changing role in the production of olefins. The current methanol-to-olefin (MTO) process, however, suffers from limited selectivity to a specific olefin. Here, we present a relay-catalysis route for the high-selective conversion of methanol to ethylene in syngas (H2/CO) typically used for methanol synthesis. A bifunctional catalyst composed of selectively dealuminated H-MOR zeolite and ZnO-TiO2, which implemented methanol carbonylation with CO to acetic acid and selective acetic acid hydrogenation to ethylene in tandem, offered ethylene selectivity of 85% at complete methanol conversion at 583 K. The selective removal of Brønsted acid sites in the 12-membered ring channel of H-MOR favors the selectivity of acetic acid in CH3OH carbonylation. The high capabilities of ZnO-TiO2 in the adsorption of acetic acid and the activation of H2 play key roles in selective hydrogenation of acetic acid to ethylene. Our work provides a promising relay-catalysis strategy for precise C-C coupling of C1 to C2 molecules.

A comprehensive review on sewage sludge as sustainable feedstock for bioenergy production

AbstractThe greatly rising amounts of sewage sludge from different sources are causing severe concerns around the globe. Disposal of sewage sludge is exceptionally difficult and poses serious environmental problems due to the significant quantity of toxic heavy metals and organic contaminants in its constituents. This review provides an overview of different conversion methods of sewage sludge into energy, that is, pyrolysis, hydrothermal gasification, hydrothermal liquefaction, hydrothermal carbonization, anaerobic digestion, and transesterification. It also focuses on each conversion route's state‐of‐the‐art research advances, features, and drawbacks to ensure financial and ecological responsibility. The detailed descriptions of the methods and respective energy generation could help scholars and industrialists produce energy from sewage sludge to keep the environment harmless.

Exploring a Ni-N4 Active Site-Based Conjugated Microporous Polymer Z-Scheme Heterojunction Through Covalent Bonding for Visible Light-Driven Photocatalytic CO2 Conversion in Pure Water.

Designing photocatalysts with efficient charge transport and abundant active sites for photocatalytic CO2 reduction in pure water is considered a potential approach. Herein, a nickel-phthalocyanine containing Ni-N4 active sites-based conjugated microporous polymer (NiPc-CMP), offering highly dispersed metal active sites, satisfactory CO2 adsorption capability, and excellent light harvesting properties, is engineered as a photocatalyst. By virtue of the covalently bonded bridge, an atomic-scale interface between the NiPc-CMP/Bi2 WO6 Z-scheme heterojunction withstrong chemical interactions is obtained. The interface creates directional charge transport highways and retains a high redox potential, thereby enhancing the photoexcited charge carrier separation and photocatalytic efficiency. Consequently, the optimal NiPc-CMP/Bi2 WO6 (NCB-3) achieves efficient photocatalytic CO2 reduction performance in pure water under visible-light irradiation without any sacrificial agent or photosensitizer, affording a CO generation rate of 325.9µmol g-1 with CO selectivity of 93% in 8h, outperforming those of Bi2 WO6 and NiPc-CMP, individually. Experimental and theoretical calculations reveal the promotion of interfacial photoinduced electron separation and the role of Ni-N4 active sites in photocatalytic reactions. This study presents a high-performance CMP-based Z-scheme heterojunction with an effective interfacial charge-transfer route and rich metal active sites for photocatalytic CO2 conversion.

Integrated process towards sustainable renewable plastics: Production of 2,5-furandicarboxylic acid from fructose in a base-free environment

We report an integrated approach to produce 2,5-furandicarboxylic acid (FDCA) using fructose as a feedstock in a base-free environment, thus providing a promising alternative to the current protocol. FDCA, an alternative molecule to terephthalic acid (obtained from the petroleum route), is used to synthesize poly(ethylene-2,5-furanoate) (PEF), a renewable plastic. In our approach, we produced 5-hydroxymethylfurfural (HMF; 84% yield) by fructose dehydration in an acetone (Ace)/H2O solvent system. The obtained HMF feed was subsequently oxidized over Ru/MnO2, producing FDCA in 92% yield under base-free conditions. The Ru/MnO2 catalyst outperformed conventional Pt/C and Ru/C catalysts under identical reaction conditions. Our novel approach for FDCA production via an integrated process using an Ace/H2O solvent mixture under base-free conditions is economically feasible and environmentally friendly. To the best of our knowledge, this work is the first to report the production of FDCA via this route. We postulate that the high catalytic efficiency of the sulfonated porous organic polymer and Ru/MnO2 in an Ace/H2O system renders them superior to existing homogeneous catalytic routes for HMF production and conversion into FDCA via a scalable process.

Behaviors and interactions during hydrothermal carbonization of protein, cellulose and lignin

Proteins participation will inevitably reconstruct the conversion route of lignocellulosic components and the formation of N-containing hydrochar during hydrothermal carbonization process. Herein, the behaviors and interaction mechanisms of protein, and typical biomass model chemicals (i.e. cellulose and lignin) were in-depth investigated. Results showed that the interaction of the binary mixture led to a reduction of hydrochar yield, but increased nitrogen concentration in hydrochar. Nitrogenous heterocyclic structure of hydrochar increased due to the interaction of protein with cellulose/lignin via forming Schiff bases and melanoids, wherein the content graphitic and pyridine nitrogen in protein-lignin hydrochar substantially increased from 5.4 % and 2.3 % to 9.7 % and 25.8 %, respectively. The increased ID/IG value from 0.81 to 0.91 in cellulose-protein hydrochar indicated the concentration of fused aromatic rings (≥6) based on Raman analysis. Carbon defects and disordered structure in hydrochar dramatically grew with the occurrence of the Maillard reaction and aldol-condensation of the intermediates. The nitrogenous substance in the aqueous phase increased by 30 %, resulted from protein decomposition accelerated by the hydrolysis of cellulose. This study provides a full understanding towards the transformation process of hydrochar from protein-containing biomass.

Design and thermodynamic analysis of a pathway enabling anaerobic production of poly-3-hydroxybutyrate in Escherichia coli

Utilizing anaerobic metabolisms for the production of biotechnologically relevant products presents potential advantages, such as increased yields and reduced energy dissipation. However, lower energy dissipation may indicate that certain reactions are operating closer to their thermodynamic equilibrium. While stoichiometric analyses and genetic modifications are frequently employed in metabolic engineering, the use of thermodynamic tools to evaluate the feasibility of planned interventions is less documented. In this study, we propose a novel metabolic engineering strategy to achieve an efficient anaerobic production of poly-(R)-3-hydroxybutyrate (PHB) in the model organism Escherichia coli. Our approach involves re-routing of two-thirds of the glycolytic flux through non-oxidative glycolysis and coupling PHB synthesis with NADH re-oxidation. We complemented our stoichiometric analysis with various thermodynamic approaches to assess the feasibility and the bottlenecks in the proposed engineered pathway. According to our calculations, the main thermodynamic bottleneck are the reactions catalyzed by the acetoacetyl-CoA β-ketothiolase (EC 2.3.1.9) and the acetoacetyl-CoA reductase (EC 1.1.1.36). Furthermore, we calculated thermodynamically consistent sets of kinetic parameters to determine the enzyme amounts required for sustaining the conversion fluxes. In the case of the engineered conversion route, the protein pool necessary to sustain the desired fluxes could account for 20% of the whole cell dry weight.

Cobaloxime‐Integrated Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution Coupled with Alcohol Oxidation

AbstractWe report an azide‐functionalized cobaloxime proton‐reduction catalyst covalently tethered into the Wurster‐type covalent organic frameworks (COFs). The cobaloxime‐modified COF photocatalysts exhibit enhanced photocatalytic activity for hydrogen evolution reaction (HER) in alcohol‐containing solution with no presence of a typical sacrificial agent. The best performing cobaloxime‐modified COF hybrid catalyzes hydrogen production with an average HER rate up to 38 μmol h−1 in ethanol/phosphate buffer solution under 4 h illumination. Ultrafast transient optical spectroscopy characterizations and charge carrier analysis reveal that the alcohol contents functioning as hole scavengers could be oxidized by the photogenerated holes of COFs to form aldehydes and protons. The consumption of the photogenerated holes thus suppresses exciton recombination of COFs and improves the ratio of free electrons that were effectively utilized to drive catalytic reaction for HER. This work demonstrates a great potential of COF‐catalyzed HER using alcohol solvents as hole scavengers and provides an example toward realizing the accessibility to the scope of reaction conditions and a greener route for energy conversion.

Cobaloxime-Integrated Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution Coupled with Alcohol Oxidation.

We report an azide-functionalized cobaloxime proton-reduction catalyst covalently tethered into the Wurster-type covalent organic frameworks (COFs). The cobaloxime-modified COF photocatalysts exhibit enhanced photocatalytic activity for hydrogen evolution reaction (HER) in alcohol-containing solution with no presence of a typical sacrificial agent. The best performing cobaloxime-modified COF hybrid catalyzes hydrogen production with an average HER rate up to 38 μmol h-1 in ethanol/phosphate buffer solution under 4 h illumination. Ultrafast transient optical spectroscopy characterizations and charge carrier analysis reveal that the alcohol contents functioning as hole scavengers could be oxidized by the photogenerated holes of COFs to form aldehydes and protons. The consumption of the photogenerated holes thus suppresses exciton recombination of COFs and improves the ratio of free electrons that were effectively utilized to drive catalytic reaction for HER. This work demonstrates a great potential of COF-catalyzed HER using alcohol solvents as hole scavengers and provides an example toward realizing the accessibility to the scope of reaction conditions and a greener route for energy conversion.

Steaming‐Assisted Conversion: A New Strategy for the Synthesis of Anatase TiO2, Nb, and W‐doped Anatase TiO2 2D Inverse Opal Films

AbstractSteaming‐assisted conversion route, a new strategy, is first adapted for the synthesis of highly crystallized anatase TiO2 2D inverse opal (IO) monolayer films, and then to Nb‐doped TiO2 and W‐doped TiO2 2D IO monolayer films. Pure water, ammonia, or HCl solutions are used as a source of steaming vapor to convert dry films of amorphous TiO2 IO, NbCl5/TiO2, and WCl6/TiO2 composite IOs into anatase TiO2, Nb‐doped TiO2, and W‐doped TiO2 IO films. This new strategy renders possible the doping of metal ions within the framework of the anatase TiO2 IO films under low temperature and liquid‐free conditions. Further, the ordered array structure of the IO films is also effectively retained. The low steaming conversion temperature allows high dopant rates of homogeneously distributed heteroatoms, resulting in Nb doping as high as ≈34%. The thus prepared TiO2, Nb‐doped TiO2, and W‐doped TiO2 anatase IO films are successfully used as active electrodes in the fabrication of electrochromic devices.

Ethylene production by partial oxidation of biogas using lime as catalyst

AbstractBACKGROUNDThe oxidative coupling of methane (OCM) is an interesting route for direct conversion of methane into ethylene and ethane. Nevertheless, COx is a secondary product of this route, which decreases the selectivity of hydrocarbons. In this work it is proposed to overcome this drawback by using biogas as source of methane. In addition to being a renewable source of methane, the presence of CO2 in biogas may shift the balance of the methane combustion. For this purpose, it was evaluated how process conditions such as O2 and CO2 flow rates and temperature affect biogas‐based OCM, in the temperature range of 650–800 °C, using lime as catalyst.RESULTSThe increase in CO2 flow from 0 to 15 mL.min−1 increased the ethylene selectivity from 25.9% to 44.5% at 800 °C. As consequence, CO2 formation dropped from 53.9% to 18.3%. Methane conversion was not affected significantly by CO2 flow rate, remaining in the range of 22–25%. O2 flow was essential to activate the OCM reaction and the presence of higher concentrations of O2 favored the selectivity of ethylene, but also increased the CO2 produced through methane combustion. In the OCM experiments with variable flow of CO2, the highest C2 yield of 18% was obtained for the highest flow of co‐fed CO2, whereas the experiments with biogas and variable O2 flow showed the highest yield of ethylene for the highest flow of air co‐fed.CONCLUSIONThus, biogas‐based OCM was shown to be a promising route to improve C2 selectivity, since the CO2 present in the biogas minimizes the formation of CO2 in the reaction. The use of lime as a low‐cost catalyst proved to be viable for the OCM reaction, presenting results compatible with those obtained for catalysts with more complex composition. © 2023 Society of Chemical Industry.

Analysis of the performances of a solid oxide fuel cell fed by biogas in different plant configurations: An integrated experimental and simulative approach

Solid Oxide Fuel Cells (SOFC) are efficient, modular and fuel-flexible high temperature electrochemical devices. SOFC systems can be coupled to biogas from anaerobic digestion plants to obtain efficient and decentralized CHP systems, maximizing the valorization of biogas in virtuous waste-to-energy schemes. The main challenges for biogas-SOFC plants are related to performance stability and degradation at process level. In this work the performance and stability of an electrolyte supported SOFC single cell (100 cm2) fed with biogas mixtures derived from different integrated biogas-SOFC CHP plant configurations (hot/cold recirculation; UFf 65–85% - obtained from previous simulation work) has been analyzed with an integrated experimental and simulative approach. To support the experimental results, a chemical equilibrium model of the gas conversion processes coupled with the electrochemical conversion route is developed in MATLAB in order to simulate the gas composition at the anode outlet, which is compared and validated with experimental data obtained by Gas Chromatography (GC). Results show that suitable and stable cell performances are obtained while feeding the SOFC samples by biogas (720–800 mV; 0.16–0.2 W/cm2 at 0.25 A/cm2) where the main performance losses are related to steam content - as well as other gas species, deriving from the pre-processing of the biogas. The gas composition and UFf simulation results show good correspondence with the GC data (error range <5% for the matrix gases and <10% for water) highlighting that the SOFC processes under clean biogas can be successfully represented - to a certain extent - by a chemical equilibrium model.

The role of electricity-based hydrogen in the emerging power-to-X economy

As energy system research into high shares of renewables has developed, so have the perspectives of the fundamental nature of a highly renewable economy. Early energy system transition research suggested that current fossil fuel energy systems would transition to a ‘Hydrogen Economy’, whereas more recent insights suggest that a ‘Power-to-X Economy’ may be a more appropriate term, as renewable electricity will become both the most important primary and final energy carrier through various Power-to-X conversion routes across the energy system. This paper provides a detailed overview on research insights of recent years on the core elements of the Power-to-X Economy and the role of hydrogen based on latest research results. These results suggest that, by 2050, upwards of 61,737 TWhLHV of hydrogen will be required to fully defossilise the global energy-industry system. Hydrogen, therefore, emerges as a central intermediate energy carrier and its relevance is driven by significant cost reductions in renewable electricity, especially of solar photovoltaics and wind power. Efficiency and cost drivers position direct electrification as the primary solution for defossilisation of the global energy-industry system; however, electron-to-molecule routes are essential for the large subset of remaining energy-related demands including chemical production, marine and aviation fuels, and steelmaking.

Achieving High Pseudocapacitance Anode SnP2O7@C By an in Situ Self-Nanocrystallization Method for Ultrastable Sodium Storage

Title: High Pseudocapacitance Anode SnP2O7@C by In Situ Self-Nanocrystallization Method for Ultrastable Sodium StorageThe rich resource and cheap price of Na have attracted attention in energy storage research and the market, becoming an optional choice for Li-ion batteries. The large radius of sodium-ion leads to a high diffusion barrier that restricted the development of sodium-ion batteries. Therefore, anodes with high capacity and stable cyclability are urgently addressed before further utilization.The mechanism of sodium-ion batteries can be classified into three categories: intercalation, alloying and conversion. Anode based on alloying and conversion mechanism became a research hotspot due to superior theoretical capacity. In pursuit of surpassing capacity, recent studies concentrated on anode with mixed mechanism, which had the potential to marriage the benefit of alloying and conversion mechanisms. However, the large volume expansion and short lifetime hindered the application in batteries.Here, we demonstrated an ultrastable sodium battery based on a novel anode, pomegranate-like SnP2O7 nanoparticles with a mixed mechanism homogeneously dispersed in the N-doped carbon matrix. Without the constraint of the grinding method, in situ self-nanocrystallization method has been first used to generate ultra-fine SnP2O7 particles.The results of the Ex-situ transmission electron microscope (TEM) characterization exhibited that the size range of SnP2O7 particles was efficiently decreased by the new fabrication method, from 66 to 20nm. During cycling tests, the nanostructure SnP2O7 particles remained well distributed in the N-doped carbon matrix rather than aggregation under long cycling tests. The self-nanocrystallization SnP2O7 nanoparticles ameliorated the diffusion of sodium-ion, which attained the acceleration of reaction kinetics. The N-doped carbon matrix contributed to the conductivity of composite material and meanwhile form strong adhesion with the carbon matrix to maintain the nanostructure SnP2O7 particles active during charge and discharge cycling. The pomegranate-like SnP2O7@C nanomaterial enhanced the pseudocapacitance to attain higher capacity and fast-charging storage. Under the capacitive-controlled behaviour test at 0.4mVs-1, the calculated capacitive showed a dominant contribution of total capacity, made up 75.7% of all. The participation of capacitive promoted avert the slow diffusion of sodium ion and obviate the destruction of the structure. The SnP2O7 carbon matrix anode exhibited superior specific capacity 403 mAh g-1 at 200 mA g-1 and cycling stability (185 mAh g-1 at 1000 mA g-1). The cycling stability of SnP2O7 nanomaterial has been ameliorated by the protection of N-doped carbon. The coulombic efficiency of SnP2O7@C showed no obvious changes and maintained around 100%, while the CE of SnP2O7 had appreciable variation. A new fabrication route of conversion and alloying anode nanomaterial was introduced in this work and has the potential to be utilized in large-scale manufacture. Figure 1

Simultaneous Operability of Thermocatalytic and Electrocatalytic CO2 Reduction Reactions

The direct electrochemical reduction reaction of carbon dioxide (eCO2RR) captured from the ambient air into base chemicals and fuels holds great potential for an elegant implementation of a net-zero emission carbon cycle. This assumes that the energy used to drive the capturing and conversion process is largely free of carbon dioxide emissions, i.e., from renewables such as wind and photovoltaics. Moreover, high Faradaic efficiency for the desired products at sufficiently high current density in eCO2RR has to be demonstrated to compete with more conventional multi-step Power-to-X conversion schemes both in terms of overall energy efficiency and cost.[1]eCO2RR is known for its wide variety of products.[2] However, hydrogen evolution reaction (HER), which is more thermodynamically reactive, inevitably seizes protons and electrons in the cathode. In addition, the reaction pathway of C2+ products is more complex than that of C1 products because it is strongly dependent on the catalyst surface and electrocatalytic operating conditions. For example, the formation of C-C bonds is interfered with the formation of C-H and C-O bonds on the catalyst surface, resulting in the direct generation of multi-carbon products technically challenging.[3] Due to these kinetic barriers, the C2+ products show much lower the energy efficiency, Faraday efficiency, and partial reduction current density of than those of the C1 products. The mechanistic aspects of the reaction pathways for the various C2+ products have not been fully deciphered, which ultimately limits the commercial application of eCO2RR conversion to C2+ products.[4]Noting that industrial thermocatalytic processes produce and supply long-chain hydrocarbons in a long-term stable manner, we propose the production of C2+ products by combining simultaneous thermocatalysis and electrocatalysis. In the ongoing work, hydrogen from the water electrolysis is further converted to syngas via a reverse water-gas shift reaction (rWGS), followed by an established conversion route to fuels and chemicals such as Fischer-Tropsch or methanol synthesis and methanol to olefins, gasoline or jet fuel.[5] Here, a reactor and test bench capable of operating at 20 bar and 200 degrees Celsius have been fabricated to enable simultaneous thermocatalytic and electrocatalytic production of C2+ products. Furthermore, different catalysts can be employed to explore the catalytic processes on the catalyst surface.

Enhancing durable fire safety and Anti-Corrosion performance of wood through controlled In-Situ Self-Assembly synthesis of Ag-PW nanospheres

In this work, we present a simple and effective approach to enhance the fire safety and anti-corrosion performance of wood by forming in-situ self-assembled amphiphilic Ag-PW nanospheres (NSP) at room temperature. The morphology and acid capacity of the NSP were optimized by changing the ratio of phosphotungstic acid (HPW) and silver nitrate. The Ag-PW NSP were successfully integrated into the bulk of the wood, resulting in a durable treatment with minimal leaching. Comprehensive characterization techniques, including FTIR, XPS, XRD, SEM, TEM, and nitrogen adsorption–desorption analysis, confirmed the in-situ formation of Ag-PW NSP in the wood. The treatment exhibited low-leaching properties with only 5.89% of Ag-PW1a leaching out. The treated wood demonstrated excellent flame-retardant (FR) properties, as evidenced by a limiting oxygen index value > 28% and easy passage of the UL-94 test, with the formation of a high-density char layer. The flammable pyrolysis products released during combustion were found to be significantly altered, with a change in the depolymerization route of conversion of LGO under acid conditions to HMF, which was verified by DFT calculations. The treated wood also exhibited outstanding anti-corrosion properties, with a mass loss rate of less than 1%, compared to at least 32.3% for bare wood after the anti-white or brown-rot fungus tests. Moreover, the treated wood samples maintained their excellent FR properties even after leaching. Our study provides valuable insights for the rational design of nano-material additives for wood protection, thereby improving the usage of wood resources while mitigating health and environmental hazards.

Intra-catalyst CH4 oxidation pathways on a Pd/Al2O3/CeZrOx-based commercial catalyst and implications on NOx conversion profiles for a natural gas vehicle exhaust under lambda modulation

The performance of a three-way catalyst (TWC) in natural gas-powered vehicles is enhanced by periodic changes in air-to-fuel ratio (λ-modulation). The reaction networks and sequences inside the catalyst that facilitate such enhanced performance have not been extensively investigated. This work applied intra-catalyst measurements (SpaciMS) to analyze the transient spatiotemporal gas concentrations inside a Pd-based TWC to establish relationships between CH4, NOx, CO and H2 conversion pathways. Steam reforming and partial oxidation were revealed to be the main CH4 conversion routes. The cyclic rich-lean conditions combined with the oxygen storage capacity (OSC) of the TWC generate reduced and oxidized zones that are constantly moving within the catalyst, changing the dominant chemical reactions occurring on the surface. In the reduced zones, OSC is depleted while CH4 is converted through steam reforming and NOx is converted through reactions with H2, CO, and other surface-bound reducing fragments formed by CH4 conversion. In the oxidized zones, OSC is replenished, CH4 is converted by partial oxidation, and H2, CO, and NH3 are oxidized. The length of lean-rich phases impacts the catalyst performance significantly; too short or too long of a rich or lean phase can lower the overall conversion of reactive species. An inhibition of CH4 conversion was observed during the rich phase possibly due to CO-poisoning of active sites. The intra-catalyst measurements revealed that the catalyst consists of three distinct reaction zones and their lengths vary with modulation conditions. Various modulation frequencies, amplitudes, λ-centers, and temperatures were investigated which allowed an understanding of how these parameters affect the reaction zones and catalyst utilization. Understandings from this work can enable adaptive λ-control strategies to optimize the overall TWC performance over a range of vehicle operating conditions.

Numerical Study to Define Initial Thermal Integration Window for Methane Oxidative Coupling with Dehydroaromatization Reactors

Oxidative coupling of methane and methane dehydroaromatization are attractive one-step conversion routes to make valuable platform chemicals more sustainable. Both processes require elevated temperatures above 600°C, good heat management, and the use of heterogeneous catalysts. None of these reactions are yet commercial due to many technical challenges. This work explores the potential of combining these two processes under one umbrella to overcome some of the technical challenges and make these processes more attractive. It focuses on the recuperative autothermal reactor coupling as one of the possible integration options. A tube-in-tube reactor design is proposed in which OCM is in the inner tube and MDA is in the outside. A numerical study is carried out using pseudohomogenous ideal fixed bed reactor models with literature kinetics. A systematic tabulated approach is used to simplify, visualize, and structure the design process and view the design options. Practical constraints such as reactor sizing, pressure drop, reaction performance, and axial temperature profile are investigated. The effect of heat transfer coefficient, diluents, catalyst profiling, and flow direction have been investigated to alter the axial temperature profile, avoid thermal run away, and improve the performance. Multiple thermally coupled OCM-MDA reactor design candidates are identified. This is the first time that the thermal coupling of OCM and MDA has been identified and quantified. These candidates are merely a starting point toward exploring the full coupling opportunities between OCM and MDA toward reaching the ultimate and more attractive option of full mass and heat integration in the same reactor.