The water-gas shift reaction (WGSR) is essential for hydrogen production and CO removal, yet its low-temperature application is hindered by sluggish kinetics. To address this limitation, a non-thermal plasma-enhanced Cu-Mn catalytic system was developed for low-temperature WGSR. A series of Cu-Mn-Al-Zr composite oxides with varying Cu/Mn ratios were synthesized, and the effects of discharge mode, catalyst composition, steam-to-carbon ratio (S/C), discharge power, and temperature were evaluated. At 170 °C, Cu1Mn2Al0.5Zr0.5 achieved only ∼5% CO conversion under thermocatalytic conditions, whereas plasma activation increased conversion to 75.4%. Control experiments distinguished the contributions of plasma activation, dielectric packing, and catalyst introduction. Characterization results show that varying the Cu/Mn ratio alters the surface chemical states of Cu and Mn species, reducibility, surface basicity, and CuO crystallite characteristics. DFT calculations reveal stronger H2O adsorption and lower dissociation barriers on Cu1Mn2Al0.5Zr0.5 compared to Cu2Mn1Al0.5Zr0.5, indicating improved water activation.
Efficient and stable catalysts are essential for biomass-tar reforming in sustainable biomass gasification systems that utilize low-cost solid waste feedstocks. In this study, coal gasification fine slag (CGFS) was processed by saline flotation to enrich the residual carbon fraction and remove ash content, yielding a support material with enhanced catalyst surface area and pore volume. Low-concentration saline flotation produced supports with greater specific surface areas (SBET), while high-concentration saline flotation yielded catalysts with superior catalytic performance. Catalytic performance was primarily determined by the nature of the metal loading. Ni-loaded catalysts (Ni4) achieved higher tar-conversion rates and CO yields than K-loaded counterparts (K4), with substantially greater H2 production. Conversely, K4 produced higher CH4 yields than Ni4, attributable to enhanced high-temperature methanation leading to higher CH4 selectivity, whereas Ni-based catalysts showed superior overall catalytic performance and anti-coking ability, attributable to their unique FeNi3 alloy active centers. Furthermore, regeneration tests demonstrated that both Ni4 and K4 catalysts retained considerable tar conversion capability after three reaction–regeneration cycles, highlighting their potential for cyclic utilization. These results demonstrate the potential of CGFS as a low-cost tar conversion catalyst.
Ammonia suffers from several inherent combustion limitations, including difficult ignition, a low flame propagation rate, and relatively high nitrogen oxide emissions. These limitations can be effectively mitigated by blending ammonia with combustion-promoting fuels. Existing review studies have generally examined individual auxiliary fuels separately, while systematic comparisons of the distinct regulatory mechanisms associated with single-component addition, binary blending, and multicomponent blending within a unified chemical-kinetic framework remain scarce. To address this gap, this review establishes a progressive analytical framework covering neat ammonia, ammonia-based binary blends, and ammonia-based ternary fuel systems. Systematic comparative analyses are conducted from multiple perspectives, including the evolution of reaction pathways, ignition characteristics, flame propagation and combustion stability, engine performance, and pollutant formation characteristics. The comparison reveals distinct roles of the three principal auxiliary fuels. H2 provides the strongest flame-propagation enhancement by enriching the H/O/OH radical pool and accelerating high temperature chain branching; DME most effectively promotes autoignition through low temperature oxidation; and CH4 offers moderate kinetic enhancement together with thermal stabilization and strong infrastructure compatibility. More importantly, ternary blends exhibit non-additive synergistic effects. In NH3/H2/DME mixtures, low-temperature DME chemistry complements H2 dominated high temperature chain branching, whereas in NH3/H2/CH4 mixtures, H2-derived radicals interact with CH4 derived CHi and C–N chemistry, producing composition-dependent changes in combustion and NOx formation. Consequently, NH3/H2/DME is advantageous for ignition-assisted applications, while NH3/H2/CH4 offers a more balanced combination of reactivity, operability, and infrastructure compatibility. Overall, ternary ammonia fuels derive their principal advantage from coupling complementary kinetic pathways across different temperature and radical regimes, providing a mechanistic basis for multi-objective optimization of ammonia combustion systems.
This study investigates the co-pyrolysis of wheat straw (WS) and polyethylene terephthalate (PET) as a potential route for addressing the global energy crisis and environmental pollution. The pyrolysis behaviors and products distributions of WS, PET, and their mixture (WS–PET) were systematically characterized using TGA, FTIR, and Py–GC/MS. FTIR analysis confirmed the presence of characteristic functional groups from both components in the WS–PET mixture. TGA revealed that WS decomposes primarily between 220 and 550 °C, while PET decomposes between 400 and 500 °C via chain scission. Their mixture exhibits a broadened, two-stage weight loss, suggesting a synergistic interaction. The activation energy of the blend was reduced to 40.05 kJ·mol-1, representing a 17.73% decrease compared with pure WS (48.68 kJ·mol-1). The pre-exponential factor decreased by ten orders of magnitude, from 2.51 × 1017 min-1 for pure PET to 1.85 × 107 min-1 for the blend. This concurrent and pronounced reduction in both kinetic parameters indicates a fundamental alteration in the reaction pathway. Py–GC/MS analysis indicated that WS pyrolysis primarily yields oxygenated volatiles (CO2, acids, ketones, and phenols), whereas PET decomposition produces CO2, acids, esters, and aromatic compounds. Free-radical species released by PET decomposition during co-pyrolysis promotes deoxygenation of biomass volatiles, suppressing oxygenate formation and enhancing the production of aromatics including benzene and biphenyl. These findings elucidate the synergistic mechanisms and reaction pathways during biomass–plastic co-pyrolysis, providing a theoretical foundation for optimizing waste-to-energy conversion and products selectivity.
Turbulent non-swirling air jets issued from convergent nozzles have been the subject of this work. The objective was to determine with what accuracy can Computational Fluid Dynamics predict the key jet characteristics, namely the axial velocity decay, the spreading rate, the entrainment and turbulence. The CFD-tools included five RANS models and an LES model which was configured so as to secure spatial and temporal resolutions up to the Kolmogorov scale. Our predictions were compared with key publications where both Direct Numerical Simulations and other LES models were used.The LES resulted in high-quality predictions from the nozzle-exit to the far-field, however, this came at extremely high computational costs which prohibits its application in engineering but encourages further scientific developments. The LES predicted well both jets, at 11,000 and 30,000 Reynolds numbers, without any adjustments to the flow conditions at the nozzle exit. The RANS realizable k-ɛ model predictions were almost of the same quality as the LES results. Differences occurred in the potential-core region, where RANS predicted a laminar core while in LES the effects of coherent structures were already visible in the core. Since the RANS results required no more than two days of computing, we strongly recommend the model for engineering applications.Our predictions were compared with the relevant LES and DNS publications. Useful relationships were derived for estimating the spatial and temporal scales of Kolmogorov eddies in turbulent jets. Both served as the indicators for resolution of LES and DNS considered.
Solvothermal liquefaction (STL) of polypropylene (PP) offers a fundamentally different reaction environment from conventional dry pyrolysis, yet its potential for controlled depolymerization of real plastic waste remains underexplored. In this study, virgin and post-consumer polypropylene were converted in a hydrogen-donor solvent (tetralin) at 400-450 °C and residence times of 0-5 h, without the use of catalysts. Near-complete conversion (99.9 wt%) was achieved at 450 °C within 1 h, yielding up to 99.8 wt% liquid product with negligible solid residue (<0.05 wt%) and minimal gas formation (<0.2 wt%). Product oils were dominated by monoaromatic hydrocarbons (up to 75 wt% under inert conditions and >90 wt% with added hydrogen), with a narrow carbon number distribution centered in the C10-C12 range (68-70 wt% under inert conditions, increasing to roughly 80 wt% with added hydrogen). Systematic variation of plastic-to-solvent ratio revealed an optimal ratio of 1:5, balancing hydrogen availability and reactive fragment interactions to maximize aromatic stabilization. Post-consumer PP exhibited conversion behavior and product distributions comparable to virgin polymer, demonstrating strong tolerance to additives and pigments. Blank-run recovery and compositional trends indicate that tetralin is thermally stable in the absence of PP and functions as a hydrogen-transfer medium during PP conversion, suppressing olefin accumulation, repolymerization, and solid formation. Compared with conventional pyrolysis, this solvothermal route enables rapid, high-yield conversion of PP into a stable aromatic-rich liquid with minimal gas and solid formation, without requiring a catalyst. The resulting monoaromatic rich-oil is heavily dominated by a narrow carbon number distribution centered in the C10-C12 range, demonstrating high compatibility with commercial petroleum refinery streams. This highlights a potential scalable, non-catalytic chemical upcycling pathway for upgrading post-consumer polyolefin waste into a refinery-compatible hydrocarbon feedstock or high-octane fuel blending component.
Biomass chemical looping gasification (BCLG) is a promising way for clean hydrogen production, yet its kinetic difference involving multiple Fe-based oxygen carriers remain unexplored. This work provided a comparative study on BCLG using Fe2O3, Fe3O4, and Fe under N2 or H2O atmospheres to explore the kinetic roles of steam and metal valence. Combining the distributed activation energy model (DAEM) with staged kinetic modeling, the kinetic mechanisms were quantitatively evaluated. The results showed that under inert condition, Fe2O3 system exhibited a higher final carbon conversion and CO2 yield, while Fe3O4 and Fe systems enhanced the early-stage release rates of CO and H2. The presence of steam significantly promoted syngas production and overall carbon conversion efficiency across all systems. Especially, Fe system demonstrated the most superior performance, generating up to 54.89 mmol/g-biomass of H2 and facilitating the formation of hydrogen-rich syngas. Furthermore, DAEM analysis indicated that the apparent activation energy evolved dynamically with the carbon conversion rate, and the steam participation effectively lowered the energy barriers in low-medium conversion regions. The whole BCLG process could be divided into three stages: an initial rapid reaction governed by nucleation and growth mechanism, followed by transition stage and slow reaction stage dominated by diffusion models. These findings clarified the kinetic mechanisms and detailed the advantages of different Fe-based oxygen carrier systems, offering a strong theoretical foundation for BCLG process optimization ad syngas improvement.
The management of end-of-life polyamide reverse osmosis membranes (EPAROM) from industrial wastewater treatment and seawater desalination has become a critical environmental and energy challenge. The present study constitutes a systematic investigation of the physicochemical characteristics and thermal conversion mechanisms of EPAROM. The EPAROM possess a high heating value (HHV) of 32.20 MJ/kg at 500°C pyrolysis. However, the hydrogen loss caused by excessive high-temperature (>500°C) pyrolysis offsets the HHV gain brought about by carbon enrichment. The dense and agglomerated microstructure of the raw material gradually evolves into a loose and porous stable carbon-based framework. Higher pyrolysis temperatures enhance the release of small-molecule gases, and the LHV of pyrolysis gas increases from 2.13 MJ/kg at 500°C to 9.71 MJ/kg at 700°C. High-temperature conditions have been demonstrated to offer significant advantages in terms of combustible gas production and the optimal gas quality. However, it should be noted that this process can result in an increase in NO and NO2 emissions. TG analysis indicates that the pyrolysis of the EPAROM mainly includes three stages: the organic impurity degradation stage (250-330°C), the residual volatile matter release stage of EPAROM (330-450°C), and the slow decomposition stage of residual char (>450°C). In accordance with the aforementioned points, three primary gasification reaction stages can be distinguished: the initial light volatile oxidation stage (250-350°C), the subsequent rapid oxidation stage of residual volatile matter (350-470°C), and the oxidation stage of residual char (470-610°C). The present study provides a theoretical basis for the efficient and clean gasification disposal of reverse osmosis membranes.
Perovskite oxides have attracted increasing attention for catalytic coal combustion due to their flexible structural tunability and excellent oxygen transfer capability. In this study, a series of LaMn0.6B0.4O3 (B = Fe, Co, Ni, Cu, and Zn) perovskite catalysts were synthesized by a sol-gel method, and the effects of B-site transition metal doping on coal combustion behavior and pollutant emission characteristics were systematically investigated. The results demonstrate that Fe, Co, and Ni doping effectively improved the structural properties of LaMnO3, while Cu and Zn doping caused unfavorable particle growth and pore structure deterioration. Among the investigated catalysts, Fe doping exhibited the most pronounced promotion effect on combustion performance, increasing the comprehensive combustion index by 33.3% and reducing the apparent activation energy by 13.90% compared with raw coal, owing to enhanced lattice oxygen mobility and redox cycling. In contrast, Co doping showed superior sulfur fixation capability, reducing SO2 emission by 46.2%, while Ni doping achieved the highest NOx reduction efficiency of 66.0% by regulating fuel-nitrogen conversion pathways. TG-FTIR and XPS analyses revealed that B-site doping modified the valence states, oxygen species distribution, and oxygen migration properties of the perovskite catalysts, thereby promoting the oxidation of carbonaceous intermediates and regulating sulfur- and nitrogen-containing species conversion. These findings highlight the functional differentiation of B-site transition metals and provide new insights into the rational design of multifunctional perovskite catalysts for efficient and cleaner coal combustion.
Sorption-enhanced reforming (SER) is a promising route for low-carbon hydrogen production because it integrates catalytic reforming with in-situ CO2 capture, but its practical application is limited by the energy penalty of sorbent regeneration, structural instability during cyclic operation, and the lack of efficient routes for utilizing captured CO2. Coupling SER with dry reforming of methane (DRM) offers an intensified strategy to directly convert captured CO2 into syngas, thereby linking hydrogen production, carbon capture, and carbon utilization within a single process. The success of SER-DRM coupling, however, depends on the rational design of multifunctional materials capable of synchronizing catalytic activity, CO2 sorption, interfacial mass transfer, coke resistance, and structural durability within a shared temperature and kinetic window. This review summarizes recent advances in such materials, with emphasis on functional component integration, catalyst-sorbent interface engineering, and structural regulation, including perovskite, spinel, and fluorite-derived systems as well as core-shell and hollow architectures. Particular attention is given to insights from density functional theory for understanding adsorption behavior, reaction pathways, and interfacial cooperative effects. Finally, the key challenges and future opportunities for developing durable multifunctional materials toward integrated low-carbon hydrogen and syngas production are discussed.
Proton exchange membrane fuel cells (PEMFCs) are promising for distributed energy applications. However, their large-scale deployment is hindered by challenges in hydrogen storage and transport. Methanol steam reforming (MSR) offers an attractive on-site hydrogen supply route, yet conventional reforming systems remain limited by insufficient CO removal, inadequate hydrogen purity, and suboptimal energy efficiency. Moreover, existing studies typically focus on either reaction enhancement or membrane separation in isolation, lacking integrated reactor designs and predictive models that simultaneously account for reaction kinetics, hydrogen permeation, and CO inhibition effects. To address these gaps, this study develops and experimentally validates a comprehensive integrated framework that combines MSR with alternative CO removal routes—either water-gas shift (WGS) or CO selective methanation (CSM)—and a Pd-based membrane separation unit. This integrated configuration enables intensified reaction–separation coupling and efficient CO conversion, significantly enhancing hydrogen permeation. Compared with conventional MSR–membrane system, the incorporation of WGS and CSM increases hydrogen permeation yield by 12.40% and 14.19%, respectively. A dual-rate kinetic model for methanol reforming and a Sieverts–Langmuir-based hydrogen permeation model incorporating CO inhibition are developed and validated through dedicated experiments. These models are coupled within a system-level simulation framework to enable parameter sensitivity analysis and operating condition optimization. The optimal configuration (LHSV = 3.26 h−1, S/C = 0.88, TMSR = 224°C, TCSM = 227°C, P = 6 atm, TM = 450°C) yields a maximum permeated hydrogen molar flow rate of 3.1182 × 10−6 kmol/s. This work provides a comprehensive reaction for permeated hydrogen production, offering new insights into the design and optimization of on-site hydrogen supply systems for PEMFC applications.
Ammonia, with a hydrogen content of 17.6 wt%, is a promising carbon-free hydrogen carrier, yet its decomposition is kinetically limited by the recombinative desorption of surface nitrogen species. Herein, a series of Cs and Ce promoted Ru/γ-Al2O3 catalysts (Ru, RuCs, RuCe, and RuCsCe) were employed for efficient NH3 decomposition in a packed-bed dielectric barrier discharge (DBD) plasma reactor. The structure-activity relationship was established through systematic characterization (XRD, SEM, TEM, XPS, H2-TPR, NH3-TPD, CO2-TPD, and N2-TPD) combined with DFT calculations of adsorption energies, reaction barriers, Bader charges, and density of states. Among these catalysts, the co-promoted RuCsCe delivered the best performance over 150-400 °C, gas hourly space velocities of 12,000–48,000 h−1, and discharge powers of 10-80 W, achieving over 95% NH3 conversion at 300 °C and 80 W and a GHSV of 12,000 h−1, retaining 68.6% conversion even at 150 °C, and maintaining approximately 96% conversion over 50 h of continuous operation. Its superiority originates from the complementary functions of the two promoters: Cs donates electrons to Ru and moderates the adsorption of N* (−0.58 eV) and N2 (−0.71 eV), whereas interfacial CeOx traps H atoms and stabilizes dehydrogenation transition states. This electronic-interfacial synergy flattens the reaction energy landscape and reduces the rate-limiting reaction barrier from 1.31 eV on Ru to 1.03 eV on RuCsCe. Electrical diagnostics based on Q-U Lissajous plots and voltage-current waveforms further confirmed that the catalyst packings retain surface-discharge-dominated DBD behavior while intensifying filamentary micro-discharges. This work provides a practical promoter-design strategy for efficient plasma-catalytic hydrogen production from ammonia.
In this study, the laminar burning velocity (LBV) of ammonia/methanol premixture was measured under the equivalence ratios of 0.7-1.4, initial temperatures of 348-408 K, initial pressures of 1-4 bar, and methanol fractions of 20-40% using experimental and theoretical investigations. The results indicate that increasing the methanol content promotes ammonia combustion, leading to enhanced LBV and burning flux. Increasing the initial temperature increases the adiabatic flame temperature, thermal diffusivity, and LBV. In contrast, increasing the initial pressure decreases the LBV, whereas the substantial increase in the unburned-mixture density results in a marked increase in the burning flux. Flame instability analysis indicates that thermal-diffusive instability is effectively suppressed by the addition of methanol, whereas hydrodynamic instability is intensified. At an equivalence ratio of ϕ = 0.7, buoyancy-driven instability becomes pronounced due to the relatively low LBV. Increasing the methanol content and initial temperature can effectively suppress buoyancy instability, whereas increasing the initial pressure aggravates it. Chemical kinetic analysis shows that the addition of methanol significantly increases the concentrations of key radicals in the radical pool (H, OH, and HO2). Among them, H and OH radicals enhance the LBV, while HO2-related reactions inhibit the LBV. The variation in NO mole fraction is highly consistent with the evolution of OH mole fraction, and H radicals also play a critical role in NO formation pathways. This study provides a theoretical basis for optimizing engine combustion strategies and achieving efficient and clean combustion, thereby contributing to the advancement of zero-carbon energy technologies.
Herein, focusing on the N2O formation pathways to gain a deeper understanding into the influence of SO2 on N2 selectivity in the low-temperature selective catalytic reduction (NH3-SCR) over MnV composite oxide catalysts. The NOx conversion rates of the catalysts exhibited a volcano-shaped relationship with the Mn/V molar ratio. The 2.0MnV catalyst with the best redox performance and the strongest surface acidity corresponded to the optimal NH3-SCR performance and the poorest N2 selectivity. The MnV catalyst consisted of Mn2O3 and MnV2O6 phases. The redox performance and NOx adsorption capacity of the SO2-poisoned 2.0MnV catalyst were significantly impaired, while the surface acidity and the Oads ratio decreased, corresponding to the inhibitions of NH3 oxidation and N2O formation. Transient reaction and TPSR experiments revealed that N2O formation on the 2.0MnV catalyst primarily followed via NH3 oxidation and NOx-involved NH3 oxidation pathways. NO partially counteracted the inhibitory effect of SO2 on the NH3 oxidation. Spectroscopic analysis revealed that the 2.0MnV catalyst did not significantly form N2O when undergoing the NH3-SCR reaction via the E-R and L-H mechanisms with SO2 presence at 180 °C. DFT calculations indicated that SO2 significantly increased the energy barriers required for the N2O formation via the “NH2NO pathway” at Lewis acid sites and the “NH4NO3 pathway” at Brønsted acid sites in Mn2O3(222) and MnV2O6(110) supercells. SO2 hindered the occurrence of key steps in the N2O formation, such as the dehydration of the NH4NO3 intermediate and the successive dehydrogenation of the NH2NO and NH2NO2 intermediates.
In this study, iron-cerium bimetallic catalysts was positioned in the fuel-pyrolysis zone, which is characterized by a fuel-rich and where fuel cracking, PAH formation, and primary soot nucleation mainly occur. This study aimed to explore how catalytic regulation non-linearly intervene in the core-shell agglomeration and morphological evolution of soot. The micro-nanostructures of soot were characterized by energy-dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The results showed that the doping of iron oxide induced an increase in soot mean fringe length and a decrease in mean fringe tortuosity, shifting the microstructure toward a highly ordered graphitic structure. The doping of a small amount of cerium activated the dynamic oxygen storage and release (OSC) mechanism, which accelerated the migration and release rate of lattice oxygen, thereby suppressing the side effects induced by iron. Notably, excessive cerium doping reduced the oxygen release capacity, which in turn led to an increase in the graphitization degree of soot.
To achieve the directed conversion and high-value utilization of volatiles from the catalytic co-pyrolysis of low-rank coal and biomass, tungsten was introduced into the Silicalite-1 zeolite framework via a hydrothermal method to prepare W-MFI catalysts with different Si/W ratios. These catalysts were applied to the in-situ catalytic reforming of volatiles from low-rank coal and corn stover co-pyrolysis. The results showed that W-MFI significantly altered the conversion pathways of oxygenated volatiles, promoting their selective transformation into light aromatics and oxygenated monocyclic compounds. At a corn stover blending ratio of 30 wt%, the W-MFI catalyst notably improved tar quality and composition distribution. Among the catalysts tested, Si/W-20 showed the best performance, increasing the light oil yield by 135.90% compared with the uncatalyzed sample. In addition, the contents of light phenolics and monocyclic aromatics increased by 129.58%. These findings suggest that W-MFI facilitates the formation of light aromatics and oxygenated monocyclic compounds, providing a promising strategy for selective volatile upgrading and tar quality improvement in low-rank coal-biomass co-pyrolysis.
Chemical looping hydrogen generation (CLHG) enables the integrated production of high-purity hydrogen and inherent CO2 separation. Compared with conventional hydrogen production technologies, CLHG offers significant advantages in energy efficiency, environmental performance and hydrogen purity, making it a promising pathway for low-carbon hydrogen production. This review systematically summarizes recent advances in CLHG from three perspectives: oxygen carriers (OCs), reactor configurations and fuel utilization. Particular attention is paid to the modification strategies of iron-based OCs, as well as the development prospects of composite oxides and high-entropy OCs. The lattice oxygen migration behaviors of different OCs and the regulatory roles of A- and B-site in perovskites on oxygen migration mechanisms are comprehensively discussed. In addition, the characteristics of various reactor configurations for CLHG are compared, and the key technical challenges associated with direct hydrogen production from solid fuels are identified. To address industrial challenges associated with insufficient long-term OC cycling stability and continuous system operation, this review proposes future development pathways, including targeted synthesis of high-entropy OCs, construction of three-reactor moving-bed coupled systems, and innovative co-utilization of diverse solid, gaseous, and liquid wastes for hydrogen production, providing new insights and strategies for the high-performance application of CLHG technology.
