Ammonia is a promising hydrogen carrier, yet the development of efficient Ru-free catalysts for ammonia decomposition remains challenging. Here, a simple La-site deficiency strategy is applied to Ba- and Co-modified LaNiO3-derived catalysts to promote Ni exsolution. A series of LBCN-x catalysts (LaxBa0.05Co0.015Ni0.985Oα, x  = 0.75, 0.85, 0.95) was synthesized and systematically investigated. Among them, LBCN-0.85 exhibited the highest NH3 conversion and excellent long-term stability. Structural and physicochemical analyses show that moderate La-site deficiency enhances oxygen vacancy formation and reducibility, facilitating Ni exsolution and maximizing Ni dispersion. In contrast, excessive deficiency leads to partial NiO segregation, suppressing effective exsolution. XPS and activation energy analyses indicate that the intrinsic electronic state of Ni remains largely unchanged. Instead, variations in catalytic performance are associated with differences in the density of exsolved Ni active sites. These findings demonstrate that tuning A-site deficiency in perovskite structures is an effective strategy for designing high-performance Ru-free catalysts.

This study aims to analyze the regeneration of Mo/HZSM-5 catalysts deactivated during shale gas dehydroaromatization, with a focus on the apparent kinetics of coke removal. Thermogravimetric analysis and single--particle kinetic modeling were employed to estimate reaction rate constants under varying O2 concentrations, temperatures, and particle sizes. The model successfully predicted the time required for coke elimination across different pellet diameters. Experimental results showed that coke was completely removed at high O2 concentrations; however, the activity of Mo2C active sites was not restored due to dealumination and the formation of Al2(MoO4)3. To ensure stable regeneration, O2 concentration and flow rate were optimized to control heat release. Long-term cycle tests demonstrated that regeneration at 1.5% O2 provided better catalyst stability than at 10%. Finally, the developed coke-removal model was applied to fixed-bed, moving-bed, and fluidized-bed reactor configurations, revealing differences in allowable O2 concentration, temperature profiles, and coke removal rates depending on gas/solid flow patterns. This work uniquely integrates kinetic modeling with stability evaluation, offering practical guidelines for selecting regeneration strategies across reactor types.

Ammonia is a promising hydrogen carrier for carbon-free energy applications due to its well-established largescale production via the Haber-Bosch process and ease of transportation. Therefore, the development of efficient catalysts for ammonia decomposition is essential for the utilization of ammonia as a hydrogen carrier. Herein, we report a highly active Ru/CeO2 catalyst prepared using triruthenium dodecacarbonyl (Ru3(CO)12) as the Ru precursor. The catalyst exhibited outstanding hydrogen production rates, achieving 3014 mmolH2 gRu-1 min-1 at 400 degrees C and GHSV of 30,000 gcat-1 h-1 with only 0.5 wt% Ru loading, surpassing previously reported Ru/CeO2 catalysts. Comprehensive characterization revealed that Ru3(CO)12 undergoes chemisorption onto CeO2 via reaction with surface hydroxyl groups, and induces the formation of surface oxygen vacancies during the impregnation. This strong interaction enables the formation of highly dispersed Ru species that remain stable under high-temperature reductive conditions. The enhanced performance was attributed to increased Ru-CeO2 interfacial area, stronger metal-support interaction, and a proximity of Ru to oxygen vacancies. These findings demonstrate that Ru3(CO)12 is an effective precursor for constructing highly dispersed and durable Ru/CeO2 catalysts for efficient ammonia decomposition.

Methane dehydroaromatization (MDA) has attracted considerable attention as a promising route for converting methane into high-value aromatics. Despite its potential, this technology has an inherently low single-pass conversion and is characterized by rapid catalyst deactivation. Here, we report a techno-economic analysis and life cycle assessment of the MDA process that systematically considers the performance of the catalyst, including its deactivation dynamics. We experimentally define three catalyst performance parameters—the initial yield, regeneration rate, and deactivation rate—to quantify time-dependent yields. These results were integrated into a surrogate-assisted framework for the estimation of the levelized cost of benzene production. Our analysis quantifies the economic impact of coke formation, demonstrating that the process is not economically viable at current catalyst performance levels due to frequent catalyst replacement and identifying the catalyst performance range required to achieve commercial competitiveness. Environmental assessment reveals that direct contribution of coke formation accounts for approximately 40% of the total carbon footprint and that combined advances in catalyst performance and renewable electricity integration can reduce the environmental impact below conventional production levels. Overall, this study quantifies the catalyst performance gap that must be closed for MDA to become an economically viable and low-carbon route to aromatics.

Methane, the main component of natural gas, is both a promising clean energy carrier and a potent greenhouse gas. Catalytic combustion of methane has therefore attracted significant attention as an efficient strategy to mitigate methane emissions. Among various catalytic systems, Pd/CeO2 has been extensively studied due to the unique Ce3+/Ce4+ redox couple that promotes oxygen mobility. However, the challenge of activating the C-H bond and the high cost of Pd necessitate catalysts that achieve high activity at low Pd loadings. In this study, Pd-CeO2 interactions were easily tuned via facile mechanochemical ball milling. Pd/CeO2 prepared at 5 Hz of milling intensity (Pd/CeO2-5 Hz) exhibited superior methane oxidation activity and stability, outperforming the conventional impregnated Pd/CeO2 catalyst. This enhanced performance is attributed to the abundant surface-dispersed PdOx nanoparticles, which serve as the key active species. Extensive characterization revealed that these Pd species possess enhanced reducibility, a higher fraction of low-valent Pd, and a superior density of coordinatively unsaturated Pd sites. In situ DRIFTS further confirmed that these PdOx nanoparticles effectively activate CHx intermediates with molecular O2, providing a mechanistic rationale for their outstanding catalytic activity. Notably, Pd/CeO2-5 Hz exhibited enhanced catalytic stability and water tolerance, demonstrating its high feasibility for practical applications.

TiO2-supported vanadium oxide catalysts with tungsten oxide promoter (VWTi) are widely used in NH3-SCR reaction, but their performance degradation at low temperatures remains an unresolved issue. Bulk vanadium oxide (VOx) has been proposed as a potential alternative due to its high activity at low temperatures; however, its deactivation behavior in the presence of SO2 has not been thoroughly identified yet. In this work, we systematically compared the catalytic performance of bulk VOx and conventional VWTi catalysts under simulated exhaust conditions containing SO2 and water. Interestingly, bulk VOx catalyst exhibited a much higher initial deactivation rate than VWTi catalyst due to its abundant exposed V sites, which accelerated SO2 oxidation and subsequent ammonium bisulfate (ABS) formation. However, once the surface became saturated with ABS, the deactivation rate stabilized and became comparable to that of VWTi. Furthermore, as previously reported for VWTi, we found that mechanical mixing of bulk VOx with zeolite effectively mitigated ABS deactivation and improved SO2 tolerance. Notably, Y zeolite with a lower Si/Al2 ratio was more effective in enhancing the sulfur resistance of bulk VOx. Additionally, TPD-MS analysis enabled the quantitative observation of sulfate species gradually forming on bulk VOx, offering additional insights into the sulfur deactivation mechanism. This work highlights a strategy to improve the sulfur tolerance of bulk VOx while elucidating its differences from conventional supported vanadia catalysts.

Ammonia slip from NH3-utilizing processes remains a critical environmental and health concern, driving the need for its removal via selective catalytic oxidation (NH3-SCO). While secondary metal incorporation has emerged as an effective strategy to enhance the performance of Cu-exchanged zeolites, the precise role of the secondary metal in modulating active Cu species and reaction pathways remains unclear. Herein, Ce incorporation into Cu/ZSM-5 markedly improved catalytic performance, achieving 89% NH3 conversion and 97% N2 selectivity at 350 °C, compared with 47% conversion and 90% selectivity over Cu/ZSM-5. Ce incorporation increases the population of active isolated Cu2+ species while suppressing Cu aggregation. Kinetic studies demonstrated a reduction in apparent activation energy and an increase in turnover frequency (TOF) upon Ce addition, suggesting enhanced intrinsic activity of the active sites. Such enhancement is attributed to CuCe interactions, which modify the electronic and redox properties of Cu species and promote efficient turnover of adsorbed NH3 species while suppressing the accumulation of less reactive surface-bound NH3 species. Moreover, the Cu–Ce/ZSM-5 catalyst exhibited improved tolerance to H2O inhibition due to additional adsorption of H2O on Ce species, thereby alleviating the competitive blocking of Cu2+ active sites. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) further revealed that Ce incorporation promotes NH3 migration from Brønsted acid sites to Lewis acid sites, thereby sustaining the supply of reactive NH3 species for the reaction. These findings establish the multifunctional promotional role of Ce in NH3-SCO and provide mechanistic insight into the rational design of high-performance Cu-based zeolite catalysts.

V2O5/WO3-TiO2 (VWTi) catalysts are widely utilized in selective catalytic reduction with NH3 (NH3-SCR) for stationary sources. However, their susceptibility to ammonium bisulfate (ABS) formation due to the presence of SO2 and H2O in flue gases poses a significant challenge. Improving the removal of ABS formed on VWTi catalysts can enhance their SO2 resistance, and zeolites with strong acid sites are promising materials for trapping ABS. To optimize the interaction between VWTi catalysts and zeolites, two sample preparation methods were evaluated in this work: hand-mixing and ball milling. This study investigates the catalytic activity and SO2 resistance of these samples to evaluate the effectiveness of the mixing techniques. The sample mixed using a mixer mill (20 Hz, 10 min) exhibited superior NOx conversion and SO2 resistance compared to the hand-mixed VWTi and zeolite Y sample. This improvement in catalytic performance was attributed to the preservation of the TiO2 particle during the ball milling process, coupled with partial fragmentation of the zeolite that facilitated intimate contact between mixed particles. In contrast, extending this approach to a MnOx + zeolite Y hybrid system revealed no synergistic effect, as the MnOx active material suffered structural damage during the ball milling process. These findings underscore the importance of ensuring that the active material maintains its structural integrity while allowing the ABS-trapping material to undergo controlled fragmentation. Such balance is crucial for maximizing the intimate contact between components and achieving optimal catalytic performance.

To address the growing demand for sustainable plastic lifecycle, hydroconversion of polyolefins is a promising strategy for catalytic recycling of plastic wastes into fuel-range hydrocarbons. Ruthenium (Ru)-based hydrogenolysis catalysts exhibit high activity in the degradation of polyolefins, and bifunctional hydrocracking catalysts are much more beneficial for the selective production of gasoline-range hydrocarbons (C-4-C-12) than monofunctional hydrogenolysis catalysts. Herein, the Ru/CeO2 and BEA zeolite hybrid catalyst demonstrated almost full conversion of low-density polyethylene (LDPE) with 95.4% gasoline selectivity, minimizing the production of low-value methane (<0.8%) in the hydroconversion of LDPE. Addition of BEA into Ru/CeO2 switched the reaction pathway from hydrogenolysis to hydrocracking with a high fraction of branched hydrocarbons and efficient usage of hydrogen. The Ru/CeO2 and BEA hybrid catalyst demonstrated the highest productivity of 3451 g(C5-C12) gRu(-1) h(-1) among the recently reported Ru-based hydroconversion catalysts, and this was even higher than that of Pt- and Ir-based hydrocracking catalysts. The effect of BEA addition on the high gasoline selectivity was validated at a reaction temperature of 250 degrees C, and it was found that among the various physicochemical properties of the zeolite, the three-dimensional pore structure with a sufficient amount of surface acidity in the zeolite is crucial for the selective production of gasoline via LDPE hydroconversion. This work provides fundamental groundwork for designing bifunctional catalysts in polyolefin recycling.

The influence of alkali metal precursor on Dual-Function Materials (DFMs) for integrated CO2 capture and methanation has not been thoroughly explored. This study systematically investigated the effect of sodium carbonate and sodium nitrate precursors on Na-Ru/Al2O3 DFM performance. The two precursors exhibited markedly different thermal decomposition behaviors. After calcination at 400 degrees C, carbonate precursors retained 3.7 % carbon while nitrate precursors underwent complete decomposition. This difference proved critical for catalyst performance. Catalysts derived from sodium carbonate precursors (Na(C)-Ru/Al) produced 1.9 times less methane than the sodium nitrate-derived catalysts (Na(N)-Ru/Al). They also showed delayed methane formation with substantial CO2 detected upon hydrogen injection for methanation. Even after substantial decomposition of carbonate precursor at 600 degrees C it exhibited low activity. Initial methane formation rates of Na(C)-Ru/Al600 sample reached only 0.56 mu mol/ming(cat) compared to 1.52 mu mol/ming(cat) for the nitrate-based system, Na(N)-Ru/Al600. XRD analysis revealed progressive sodium aluminate formation upon carbonate decomposition, which likely contributed to the low methane productivity by hindering RuOx reduction. This structural transformation elevated RuOx reduction temperature from 148 degrees C (Ru/Al400_600 reference) to 223 degrees C. In contrast, nitrate-derived samples prevented this structural change and maintained optimal reduction of RuOx at 124 degrees C. The impact of calcination atmosphere on catalyst stability was also investigated by calcining Na(C)-Ru/Al samples under static air, CO2, O-2, and N-2 atmospheres. Notably, calcination under CO2 atmosphere prevented Ru volatilization and maintained optimal Na+ dispersion. In contrast, other atmospheres led to detrimental NaAlO2 formation, which is associated with catalytic performance.

Ruthenium catalysts exhibit exceptional C-C bond cleavage activity for polyolefin conversion. However, their strong hydrogenolysis tendency produces excessive methane, limiting practical fuel production. Here, we demonstrate that physical mixing of Ru/TiO2 with BEA zeolite fundamentally redirects this pathway from hydrogenolysis to selective hydrocracking, achieving complete polyethylene conversion with 83% gasoline yield while suppressing methane formation below 0.5% under mild conditions (260-270 degrees C, 3 h). Kinetic analysis reveals a sharp decrease in activation energy around 250 degrees C, establishing that hydrocracking becomes kinetically favored over hydrogenolysis. This confirms that the pathway switching is a fundamental mechanistic transformation, not a transient change. Mechanistic studies reveal that this pathway switching operates from the reaction onset, fundamentally transforming catalytic role of Ru from direct C-C bond cleavage to (de) hydrogenation functions while BEA zeolite governs selective cracking. This transformation requires large-pore zeolites with sufficient Br & Oslash;nsted acidity, and spatial separation through physical mixing prevents Ru confinement within micropores-both critical for suppressing undesired methane formation. The physical mixture strategy demonstrates excellent reusability and broad applicability across diverse polyolefin feedstocks. This mechanistically-guided approach establishes spatial separation as a critical design principle for selective polyolefin-to-fuel conversion.

The direct conversion of methane into valuable aromatics through methane dehydroaromatization (MDA) has gained significant attention for effective methane utilization. In this study, we optimized the preparation and shaping processes of NiO-Mo/HZSM-5 catalysts to enhance their industrial applicability. Silylation of HZSM-5 with 3-aminopropyl trimethoxysilane effectively removed external Br & oslash;nsted acid sites, improving BTX selectivity. We compared three Mo loading methods-impregnation, rotary ball milling, and vibratory ball milling-and found that rotary ball milling resulted in the highest Mo dispersion and the most favorable acidity profile, leading to the best MDA performance. The optimized NiO-Mo(R)/HZSM-5(Si) catalyst was shaped into extrudates and beads using inorganic binders. Although molding slightly reduced surface area and acid sites, both shaped catalysts retained comparable BTX yields. The extrudate-type catalyst demonstrated better regeneration potential due to reduced hard coke formation. This study presents a scalable approach for developing highly active and stable Mo-based MDA catalysts and highlights the importance of external acid control, metal dispersion, and catalyst shaping for commercial application.

The catalytic aromatization of light alkanes presents a promising route for producing benzene, toluene, and xylene (BTX) along with hydrogen. However, catalyst deactivation and carbon deposition remain major challenges for practical application and sustainable operation. In this study, the effect of zeolite topology on the performance of Mo-based catalysts during CO2- and CH4-assisted n-butane aromatization was systematically investigated using Mo/ZSM-5 and Mo/MCM-22 catalysts. While CO2 co-feeding effectively suppressed coke formation, excessive CO2 promoted partial oxidation of the active phase, Mo(Ox)Cy, resulting in a loss of activity. To overcome this trade-off, CH4 was co-fed alongside CO2 to serve as a reductive and carburizing agent, stabilizing the active phase under oxidizing conditions. Compared to Mo/ZSM-5, the Mo/MCM-22 catalyst exhibited significantly enhanced stability and BTX productivity under various CO2 and CH4 co-feeding conditions. The superior performance of Mo/MCM-22 is attributed to its improved Mo dispersion, leading to lower C9+ aromatic formation and promote soft coke accumulation. These findings highlight the synergistic role of CO2 and CH4 in enhancing catalyst stability and also emphasize the importance of zeolite framework selection in optimizing catalytic performance for sustainable aromatization of n-butane.

Methane (CH4) is a high-energy-density fuel with abundant global reserves, making it a valuable energy resource. However, its global warming potential is approximately 21 times that of carbon dioxide (CO2), highlighting the urgent need for effective CH4 emission control. Catalytic oxidation of CH4 into CO2 using Pd-based catalysts is a promising strategy due to their high activity. However, their practical application is hindered by rapid deactivation in humid environments, primarily caused by active site transformations and hydroxyl accumulation. Given the high cost of Pd, enhancing catalyst stability is essential for industrial viability. In this study, we demonstrate that gamma-Al2O3 mixed with 0.5 wt% m-ZrO2 significantly improves the stability of Pd-based catalysts under humid conditions. While conventional Pd/gamma-Al2O3 suffered a significant decline in CH4 conversion, dropping from 70% to 39% over 20 h in a 10% H2O atmosphere, the Zr-doped Pd/gamma-Al2O3 maintained its catalytic performance. This enhancement is primarily attributed to the inhibition of Pd sintering and suppression of inactive Pd site formation, facilitated by strong Pd-Zr interactions. The Zr were uniformly dispersed onto the Al2O3 surface via a solvent-free ball-milling method, stabilizing Pd active sites and restricting their mobility. Additionally, the hydrophobic nature of m-ZrO2 mitigated hydroxyl accumulation, promoting the effective reoxidation of Pd active sites. These findings highlight that oxide support physically mixed with secondary oxides is a simple yet effective approach for enhancing the durability of Pd-based catalysts, advancing the development of more sustainable catalytic technologies for industrial applications.

Lignocellulose or lignin present significant potential as sustainable feedstocks to replace petroleum-derived resources through catalytic upgrading. Hydrodeoxygenation of phenolic molecules derived from lignocellulose or lignin can produce cycloalkanes, but often forms low-carbon-number hydrocarbons, which are more suitable for gasoline rather than high-carbon-number diesel or aviation fuels. This study investigates the production of high-carbon-number hydrocarbons in the aviation fuel range from lignin-derived compounds, using vanillin as a model. A two-step process was performed to achieve this: selective hydrogenation of vanillin to vanillyl alcohol and creosol using 1 wt% ruthenium on carbon, followed by non-catalytic condensation and subsequent hydrodeoxygenation of the condensates to cycloalkanes using 3 wt% ruthenium on HZSM-5. This process yielded C14 aviation fuel precursor (19%) and C14 deoxygenated hydrocarbon (5%) whereas the one-step process without the condensation step did not yield any C14 compounds. The reaction pathway was elucidated through density functional theory calculations and control experiments with intermediates, providing insights into the mechanisms of upgrading lignin-derived compounds for sustainable aviation fuel production.

One of the main goals of catalysis research is to improve the reaction efficiency by using platinum-group metals (PGMs) more effectively, given their high cost. PGMs are typically dispersed on oxide supports to maximize their surface area, under the assumption that catalytic activity arises primarily from the PGMs and their immediate oxide surroundings, while oxide surfaces located further away from PGMs are often considered catalytically irrelevant. However, a growing body of research on spillover phenomena suggests that PGMs can influence the catalytic properties of oxide surface sites located several nanometers away from PGMs, prompting the question of whether distant oxide surfaces can play a more active, or even dominant, role in catalytic kinetics. A shift in understanding, from viewing the oxide surface as merely a passive support to recognizing it as an active promoter of the rate-limiting step (RLS), would offer an alternative framework for optimizing PGM utilization. In this contribution, we investigated the role of distant oxide surfaces in CO oxidation, using Pt/CeO2 as a model system. Our findings show that distant CeO2 surfaces are not inert but can promote the CO oxidation reaction via oxygen spillover. Interestingly, when the CeO2 content in Pt/CeO2 is high, the catalytic activity across catalysts with varying distributions of Pt single atoms and clusters is identical. Kinetic analysis reveals that, in CeO2-rich Pt/CeO2 catalysts, the RLS is the activation of oxygen on the distant CeO2 surface. Further investigation indicated that the alignment of CeO2 grains during reductive treatment facilitates the oxygen supply to Pt, boosting catalytic activity. This study suggests that leveraging the catalytic function of the distant oxide surface offers a promising strategy to enhance the efficiency of PGMs, providing an alternative perspective on catalyst development.

The role of TiO2, ZnO, and ZnTiO3 as supports for rhodium has been investigated for the CO2 hydrogenation. Rh/TiO2 demonstrated a high selectivity for CH4, which is typical for Rh catalysts; however, Rh/ZnO and Rh/ZnTiO3 shifted the product selectivity to CO almost exclusively. The difference in behavior is attributed to the modulation of strong metal-support interactions (SMSIs) by the supports. Detailed characterization revealed the formation of a distinct metallic Zn overlayer covering the RhZnx alloyed nanoparticle in Rh/ZnO, altering the electronic states of Rh, and a RhTix overlayer in Rh/ZnTiO3, suppressing the CO adsorption on Rh in bridged and tilted geometry and polarizing the CO bond. These structural features significantly modify the CO adsorption strength and mode, together with the intermediate hydrogenation behavior, influencing product formation. The study highlights the potential of tailoring SMSI states by modifying the support composition and interfacial coupling with metal nanoparticles, enabling improved CO-selective hydrogenation. These findings offer deeper insights into engineering metal-support interactions, with broad implications for advancing industrial processes involving CO, including Fischer-Tropsch synthesis, the water-gas shift reaction, and methanol synthesis.

Ammonia decomposition is a promising route for carbon-free hydrogen production, although the development of non-noble metal catalysts with high activity remains a critical challenge. We report the rational design of LaNiO3-based perovskite-derived catalysts for efficient ammonia decomposition via systematic La-and Ni-site substitution and thermal treatment optimization. Incorporation of Ba into the La site significantly enhanced the electronic density of Ni by increasing surface basicity and facilitating electron donation. Subsequent Co substitution at the B-site further improved Ni dispersion by destabilizing the perovskite structure, promoting exsolution of metallic Ni. Thermal treatment parameters-including calcination temperature, reduction temperature, and ramping rate-were optimized to facilitate the exsolution of surface-accessible Ni nanoparticles with high dispersion. Comprehensive characterization using XRD, H2-TPR, N2-physisorption, H2-chemisorption, CO2-TPD, XANES, and XPS revealed correlation among Ni dispersion, electronic properties, and catalytic reactivity. The catalyst with optimized Ba/Co content and thermal treatment (denoted optimal LBCN) exhibited the highest NH3 conversion (85.9 % at 550 degrees C, 30,000 mL/gcat center dot h) and demonstrated outstanding thermal stability over 100 h. This study highlights the synergistic role of structural and electronic tuning in designing costeffective perovskite-derived catalysts for ammonia-based hydrogen production.