Catalysts For Decomposition Research Articles

Investigation of catalytic efficiency of nanoparticles of alloys on thermal behavior of AP and AP-based solid propellants

In this article, we present the catalytic proficiency of three different nano metal alloys Cu–Co, Cu–Fe, and Cu–Zn) on thermal behavior of powder ammonium perchlorate (AP) and composite solid propellants (CSPs) samples. A hydrazine reduction method was used for synthesized Cu–Co, Cu–Fe, Cu–Zn alloys nanoparticles and they were characterized by XRD, FTIR, and SEM. The catalytic impact of nano alloys on thermal behavior AP and CSPs is established by implementing through TG-DSC technique. The Kissinger Akahira Sunose (KAS), Flynn wall Ozawa (FWO), and Starink methods were used to determine activation energies of all AP and CSPs samples. The Cu–Zn Nanoalloys acted as good catalyst for thermal decomposition of AP and CSPs and it reduced the decomposition temperature and activation energy of AP and CSPs. It increased the burning rate of CSPs.

Unraveling the O2 resistance of promoters in BaO-Y2O3-based catalyst for NO decomposition

Unraveling the O2 resistance of promoters in BaO-Y2O3-based catalyst for NO decomposition

Catalytic evaluation of microwave-assisted copper cobaltite oxide (CuCo2O4) for propane oxidation.

Attainment of a pristine copper cobaltite (CuCo2O4) phase by a fast and easy microwave (MW) assisted method is presented in this paper. The successful synthesis was supported by a series of characterization techniques, which confirmed the presence of a single phase and a possible inverted spinel crystal structure. Furthermore, catalytic performance evaluation of CuCo2O4 in propane oxidation demonstrated its selectivity towards carbon dioxide (CO2) formation, with negligible propanol production. Heating rate modification has a minimal impact on propane conversion, while catalyst stability tests indicate acceptable performance over multiple reaction cycles. X-ray diffraction analysis of the recycled catalyst suggests the formation of CuO, which seems to affect catalytic activity. Although the catalytic trials at lower temperatures resulted in lower efficiency, they effectively suppressed catalyst decomposition and allowed multiple recycling of the catalyst without any loss of catalytic activity.

Modified Fly Ash: An Eco‐Friendly, Cost‐Free, and Efficient Iron‐Based Catalyst for Ammonia Decomposition to COx‐Free Hydrogen

AbstractFly ash (FA), an industrial waste produced in large amounts, is rich in metal oxides such as Al2O3, SiO2, and Fe2O3, making it an ideal candidate for use as a catalyst in ammonia decomposition. However, FA's surface area is very low (<1.0 m2 g−1), limiting its potential. This study investigates the modification of FA by calcination at various temperatures (550, 700, and 1000 °C), HCl treatment, and HCl treatment followed by calcination at 500 °C to convert FA into a catalyst by utilizing its iron content as active sites. The catalyst obtained by treating FA with HCl at 220 °C, calcining at 500 °C, reducing in H2 at 700 °C, and activating in ammonia at 700 °C achieved 86.0% ammonia conversion at a reaction temperature of 700 °C and a space velocity of 30,000 mL NH3 h−1 gcat−1, remaining stable for 140 h following an induction period of 30 h. Enhanced textural properties (18.5 m2 g−1), elimination of S and Cl impurities, and the formation of relatively small Fe crystallites (23.8 nm determined by Scherrer equation and 24.0 nm measured by transmission electron microscopy (TEM)) when reduced in H2 were responsible for this performance.

Combined Reaction System for NH3 Decomposition and CO2 Methanation Using Hydrogen Permeable Membrane Reactor in 1D Model Analysis.

In a previous study, we developed an integrated reaction system combining NH3 decomposition and CO2 methanation within a membrane reactor, significantly enhancing reactor performance through efficient H2 separation. Ru/Ba/γ-Al2O3 and Ru/ZrO2 were employed as catalysts for each reaction. To ensure the accuracy and reliability of our results, they were validated through 1D models using FlexPDE Professional Version 7.21/W64 software. Key parameters such as reactor arrangement, catalyst bed positioning, overall heat transfer coefficient, rate constants, and H2 permeance were investigated to optimize system efficiency. The study revealed that positioning the NH3 decomposition on the shell side and CO2 methanation on the tube side resulted in a better performance. Additionally, shifting the methanation catalyst bed downward by approximately one-eighth (10 mm from 80 mm) achieves the highest CO2 conversion. A sensitivity analysis identified the rate constant of the NH3 decomposition catalyst and the H2 permeance of the membrane as the most influential factors in enhancing CO2 conversion. This highlights the priority of improving membrane H2 permeance and catalytic activity for NH3 decomposition to maximize system efficiency.

Unveiling Tetrafluoromethane Decomposition over Alumina Catalysts.

Tetrafluoromethane (CF4), the simplest perfluorocompound known as a "forever chemical", presents substantial environmental challenges due to its health risks and contribution to the greenhouse effect. Designing efficient catalysts for CF4 decomposition remains difficult, compounded by limited understanding of the mechanisms. Here, we use constrained ab initio molecular dynamics (cAIMD) simulations and in situ experiments to elucidate the mechanism of alumina-catalyzed CF4 decomposition, highlighting the pivotal role of surface hydroxyl groups. The initial C-F bond breaking is the rate-determining step, with surface hydroxyl groups reducing the reaction free energy from 1.69 to 1.34 eV. These hydroxyl groups also facilitate the self-healing of oxygen vacancies generated during the decomposition. Contrary to the belief that CF4 decomposes directly into CO2, our cAIMD simulations, supported by synchrotron vacuum ultraviolet photoionization mass spectrometry data, reveal significant CF2O and CO byproducts. Experimental data in an anhydrous environment indicate that water primarily replenishes surface hydroxyl groups rather than directly participating in decomposition. We conclude that the relatively high efficiency of Al2O3 catalysts stems from three key properties: (1) the presence of active sites with a specific affinity for CF4 adsorption, ensuring efficient substrate interaction; (2) appropriate metal-oxygen bond strength, enabling the participation of lattice oxygen in the reaction; and (3) a high density of surface hydroxyl groups that facilitate the initial C-F bond cleavage and the self-healing of oxygen vacancies.

Study on the Effect and Mechanism of Support and Deposition-Precipitation Method on Ru-Based Catalysts for Ammonia Decomposition

Study on the Effect and Mechanism of Support and Deposition-Precipitation Method on Ru-Based Catalysts for Ammonia Decomposition

Hydrogen Release from Ammonia: Size and Support Effects in Heterogeneous Transition Metal Catalysis

Ammonia can serve as a promising renewable energy carrier based on its high hydrogen content and energy density as well as its full‐fledged transportation infrastructure. Renewable hydrogen can be converted in ammonia synthesis, stored and/or transported bound in ammonia and released on demand by ammonia decomposition. The most active catalysts for this reaction are Ru‐based due to its optimal nitrogen binding energy compared to other transition metals. However, the development of alternative non‐noble transition metal catalysts such as Fe, Ni or Co is attractive. For supported metal catalysts, size and support effects play important roles in many catalytic reactions resulting in a change of geometric and/or electronic properties. In this review, we first discuss existing studies of size and support effects on Ru, Fe, Ni, Co catalysts in ammonia decomposition from an experimental and theoretical viewpoint. Afterwards, we compare the available catalytic data in the form of TOFH2 and reaction rate for each metal catalyst supported on different supports and as a function of particle size, attempting to identify an optimum particle size and a trend for the different supports. Finally, we discuss the challenges and perspectives of future research on the size and support effect in ammonia decomposition.

Knitted Catalyst for Decomposition of Anthraquinone and Acid Dyes in Wastewater

Knitted Catalyst for Decomposition of Anthraquinone and Acid Dyes in Wastewater

Investigation of Nonmetal F‐doped Co3O4 as Catalyst for N2O Catalytic Decomposition

AbstractAn effective nonmetal F‐doped Co3O4 (F‐Co3O4) catalyst was prepared using co‐precipitation method, and its catalytic performance was investigated for N2O decomposition comparing with pure Co3O4 catalyst. The catalytic activity test indicates that F‐Co3O4 catalyst exhibits better activity with 100% N2O conversion at a reaction temperature of 380 °C, which is 80 °C lower than that of pure Co3O4. The characterization results show that F is successfully doped into the lattice of Co3O4 and replaces part of O sites, which enlarges the surface area, enhances the surface basicity, and leads to higher basic sites density on the surface of Co3O4. Moreover, F doping promotes the electron donation capacity of Co2+, weakening of Co─O bond and generation of more oxygen vacancies. The synergy of the above factors results in reduction of activation energy over F‐Co3O4 catalyst, thus F‐Co3O4 catalyst exhibits better catalytic performance than pure Co3O4 for N2O decomposition, even in the existence of O2 or H2O as impurity gas. Meanwhile, F‐Co3O4 catalyst also exhibits better stability than pure Co3O4. This work will provide practical reference for constructing efficient nonmetal‐doped Co3O4 catalysts for N2O decomposition.

Hydrotalcite-derived well-dispersed and thermally stable cobalt nanoparticle catalyst for ammonia decomposition

Ammonia is a carbon-free hydrogen carrier, and development of non-noble metal catalyst to decompose ammonia into hydrogen is desirable for practical applications. However, the metal catalyst is challenged by the sintering of metal particles under high-temperature reaction conditions. In this study, a series of Li-, Al-, and Co-containing hydrotalcite-like compounds (HTlc) were synthesized by co-precipitation and used as precursors to prepare well-dispersed and thermally stable Co nanoparticle catalysts for ammonia decomposition. The obtained precursors and catalysts were characterized by means of X-ray powder diffraction (XRD), temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and so on. All of the precursors formed hydrotalcite-like phase, which consisted of Li–Al–(Co) HTlc and/or Co–Al HTlc dependent on the Co content. Upon calcination at 500 °C, HTlc decomposed into an Al-substituted Co3O4 spinel oxide, as confirmed by two distinctly separated reduction steps in H2-TPR. Following reduction at 700 °C, well-dispersed Co metal nanoparticles with an average particle size of ∼9.2–12.4 nm were obtained. It was suggested that the incorporation of Al3+ into Co3O4 led to a strong interaction between cobalt and aluminum, which suppressed the crystal growth of Co3O4 and the sintering of Co metal during the thermal treatments, resulting in good Co dispersion. The optimal LiAlCo(1.5) catalyst showed superior activity than that prepared by impregnation method, giving almost complete conversion of ammonia at 575 °C under a space velocity of 5,000 mL gcat–1 h–1. More importantly, this catalyst maintained stable activity at 625 °C for 100 h, exhibiting high stability and sintering resistance. The good catalytic performance was attributed to the high Co metal dispersion and strong metal–support interaction benefiting from the uniform distribution of cobalt in the HTlc precursor. These results demonstrate the applicability of HTlc to the preparation of metal catalysts with improved dispersion and thermal stability.

Recycling waste tiles and waste catalysts for high-strength eco-porous ceramics in building applications

This study explores an innovative approach to recycling waste tiles and spent catalytic materials from the petrochemical industry, aiming to create ecological porous ceramics (eco-PC) as sustainable building materials. The production process involved high-pressure sintering at 5 MPa and temperatures of 900–1050 °C. Extensive testing revealed that eco-PC meets CNS 9737 standards for flexural strength, with heavy metal concentrations (measured using microwave-assisted acid digestion) within regulatory limits, confirming the materials’ recyclability. The eco-PC samples exhibited water absorption between 7.90% and 35.33%, with higher sintering temperatures reducing absorption due to vitrification, while increased waste catalyst content raised absorption due to retained porosity. Porosity ranged from 16.35% to 47.42%, influenced by sintering temperature and waste catalyst content. Loss on ignition (0.14–1.63%) was affected by the decomposition of waste catalyst and sintering temperature. Flexural strength varied from 3.36 to 179.09 N/mm2, and modulus of rupture from 458 to 16,718 N, all exceeding CNS 9737 requirements. Conversely, higher catalyst content decreased strength due to limited densification of aluminum oxide. X-ray diffraction identified quartz as the primary phase, FTIR analysis showed surface functional groups (Si–O–Si and Si–O–Al), and SEM revealed a dense structure at 1050 °C due to liquid-phase sintering. Optimal eco-PC samples with 30–40% catalyst substitution and sintering temperatures of 900–1000 °C achieved a moisture buffering value (MBV) of 3.69 g/m2·%RH@8h, ideal for humidity regulation due to high surface area and pore volume. This research demonstrates the potential to transform waste into green building resources through an efficient, cost-effective, and eco-friendly process.

FeCo Alloy-Decorated Proton-Conducting Perovskite Oxide as an Efficient and Low-Cost Ammonia Decomposition Catalyst

Ammonia is known as an alternative hydrogen supplier because of its high hydrogen content and convenient storage and transport. Hydrogen production from ammonia decomposition also provides a source of hydrogen for fuel cells. While catalysts composed of ruthenium metal atop various support materials have proven to be effective for ammonia decomposition, non-precious-metal-based catalysts are attracting more attention due to desires to reduce costs. We prepared a series of Fe, Co, Ni, Mn, and Cu monometallic catalysts and their alloys as catalysts over proton-conducting ceramics via the impregnation method as precious-metal-free ammonia decomposition catalysts. While Co and Ni showed superior performance compared to Fe, Mn, and Cu on a BaZr0.1Ce0.7Y0.1Yb0.1O3−б (BZCYYb) support as an ammonia decomposition catalyst, the cost of Fe is much lower than that of other metals. Alloying Fe with Co can significantly increase the conversion and stability and lower the overall cost of materials. The measured ammonia decomposition rate of FeCo/BZCYYb reached 100% at 600 °C, and the ammonia decomposition rate was almost unchanged during the long-term test of 200 h, which reveals its good catalytic activity for ammonia decomposition and thermal stability. When the metallic catalyst remained unchanged, BZCYYb also exhibited better performance compared to other commonly used oxide supports. Finally, when ammonia cracked using our alloy catalyst was fed to solid oxide fuel cells (SOFCs), the peak power densities were very close to that achieved with a simulated fully cracked gas stream, i.e., 75% H2 + 25% N2, thus proving the effectiveness of this new type of ammonia decomposition catalyst.

Sodium Carbonate-Modified activated carbon catalysts for enhanced hydrogen production via methane decomposition

Hydrogen is a clean and renewable energy source with significant potential for decarbonizing energy systems. Methane decomposition offers a sustainable method for hydrogen production without the emission of COx gases, making it as an attractive alternative to conventional methods like steam reforming. However, the high energy consumption associated with methane decomposition presents a challenge. To address this challenge, this study explores the modification of activated carbon (AC) with sodium carbonate (Na2CO3) to enhance its catalytic efficiency in methane decomposition. Various concentrations of Na2CO3 were used, and the catalysts were thoroughly characterized using XRD, SEM, and N2 adsorption–desorption techniques to evaluate their porosity, surface area, and crystallinity. The results indicate that Na2CO3-modified AC significantly reduced the degree of graphitization, resulting in a disordered carbon structure with enhanced porosity. This structure effectively enhances the catalytic activity of AC, with the optimal catalyst being AC-2Na2CO3. After 150 min of reaction, the methane conversion rates at 850 °C, 900 °C, and 950 °C are 17.18 %, 20.19 %, and 31.33 %, respectively, representing increases of 5.19 %, 5.69 %, and 5.32 % compared to the unmodified catalyst. These improvements are attributed to the creation of more active sites for methane adsorption and dissociation. Overall, the study demonstrates the potential of Na2CO3-modified AC as an efficient catalyst for methane decomposition, offering a viable pathway for sustainable hydrogen production with reduced energy consumption.

Single-atom Barium Promoter Enormously Enhanced Non-noble Metal Catalyst for Ammonia Decomposition.

As a well-established topic, single-atom catalyst has drawn growing interest for its high utilization of metal. However, researchers prefer to develop various active metals with single-atom form, the intrinsic roles of single-atom promoters are usually underrated, which are significant in boosting reaction activity. In this work, Ba single atoms were in situ prepared in the Co-Ba/Y2O3 catalyst with crystallized BaCO3 as the precursor under the ammonia decomposition reaction condition. The optimized Co-Ba/Y2O3 catalyst achieves extremely high H2 production rate of 138.3 mmolH2·gcat-1·min-1 at very low temperature (500 °C, GHSV = 840,000 mL·g-1·h-1) and Co-Ba/Y2O3 exhibits excellent durability during the 350 h test, which realizes the highest activity among all non-noble catalysts, and reaches or even exceeds numerous reported Ru-based catalysts. Both Y2O3 and Co demonstrate positive interactions with Ba, which significantly facilitates the dispersion of Ba species at high temperatures (≥ 600 °C). Ba single atoms significantly enhance the charge density of Co and form additionally active Co-O-Ba-Y2O3 interfacial sites, which alleviates hydrogen poisoning and decreases the reaction barrier of the N-H bond activation of *NH. The exploration of atomically dispersed promoters is groundbreaking in heterogeneous catalysis, which opens up a whole new domain of catalytic material.

Hemilabile and Redox-Active Quinone Ligands Unlock sp3-Rich Couplings in Nickel-Catalyzed Olefin Carbosulfenylation.

A three-component coupling approach toward structurally complex dialkylsulfides is described via the nickel-catalyzed 1,2-carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N-S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N-S electrophile containing an N-methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol %. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox-active ligands that tune the steric and electronic properties of the metal throughout the catalytic cycle. Density functional theory (DFT) results show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni-catalyzed 1,2-carbosulfenylation-binding as an η6 capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X-type redox-active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, and binding as an L-type ligand to promote N-S oxidative addition at a relatively more electron-rich Ni(I) center.

Hemilabile and Redox‐Active Quinone Ligands Unlock sp3‐Rich Couplings in Nickel‐Catalyzed Olefin Carbosulfenylation

AbstractA three‐component coupling approach toward structurally complex dialkylsulfides is described via the nickel‐catalyzed 1,2‐carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N−S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N−S electrophile containing an N‐methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol %. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox‐active ligands that tune the steric and electronic properties of the metal throughout the catalytic cycle. Density functional theory (DFT) results show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni‐catalyzed 1,2‐carbosulfenylation‐binding as an η6 capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X‐type redox‐active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, and binding as an L‐type ligand to promote N−S oxidative addition at a relatively more electron‐rich Ni(I) center.

Discovery of Alloy Catalysts for Ammonia Decomposition by Machine Learning-Based Prediction of Adsorption Energies

Ammonia decomposition has gained significant attention as an eco-friendly method for hydrogen production because it creates no carbon dioxide emissions. While Ru catalysts are known for their high activity in ammonia decomposition, their high cost makes them uneconomical for commercial use. Therefore, it is essential to explore novel alloy catalysts composed of inexpensive elements with high catalytic performance. Nitrogen adsorption energies serve as key descriptors indicating the catalytic performance for ammonia decomposition, and first-principle calculations can compute these energies. However, the screening of numerous alloy catalyst candidates through extensive first-principle calculations and experimental validations remains time-consuming due to the vast number of potential candidates. To address this, artificial intelligence and machine learning models are being developed to quickly predict catalyst performance, efficiently searching for promising catalyst candidates. In this study, we developed a machine-learning-based method to rapidly predict nitrogen adsorption energies using a graph-based artificial neural network, thereby efficiently searching for novel catalysts for ammonia decomposition. Our training dataset included the nitrogen adsorption energies of 30 pure transition metal catalyst candidates, as well as binary alloy catalyst candidates, including core-shell and intermetallic compounds. As a result, we successfully identified 12 catalyst candidates composed of inexpensive elements that are likely to exhibit catalytic performance comparable to Ru catalysts.

Разложение аммиака на Co-Al2O3 /SiO2 катализаторах: влияние способов восстановления кобальта

The focus on "green" energy requires the search for environmentally friendly energy storage systems. The reason for choosing ammonia as a potential storage for hydrogen is its high energy capacity and the absence of carbon and nitrogen oxide emissions during decomposition. Herein, we tested Co-Al2O3/SiO2 ammonia decomposition catalysts that had been pre-activated via cyclic hydrogenation-carburization-hydrogenation (RCR) and reduction-oxidation-reduction (ROR) procedures versus the conventional cobalt oxides reduction with hydrogen (R). The samples were characterized by H2-TPR, TEM and synchrotron X-ray diffraction techniques, which revealed that the structural properties of the catalysts were not modified by the reaction. Since the activities of the tested catalysts and the effective reaction barriers appeared to be close, the easiest-to-prepare catalyst R was chosen for the long-term catalytic trial (500 h), and it showed excellent performance stability.

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon

Fe–Ce–Al Catalysts for Decomposition of Methane to High Purity Hydrogen and High-Value Carbon