Catalysts For Combustion Research Articles

Insights into the exceptional support phase effect on Ag/Sm2Ce2O7: Modulating Ag distribution and Ag-support interaction to construct reactive soot oxidation catalysts

Developing efficient, cost-effective and robust catalysts for soot combustion is crucial yet challenging. In this study, we fabricated Ag-loaded Sm2Ce2O7 paramorphs catalysts (C-type and Cubic fluorite) via different methods, aiming to improve the distribution and interaction of Ag by modifying the crystalline structures of the supports to enhance oxygen activation. The oxygen vacancy concentration and redox performance of the rare earth C-type catalysts exceeded those of the cubic fluorite ones. In the case of the Ag-assisted catalysts, the Sm2Ce2O7–Ag interface with oxygen vacancies displayed an increased affinity for oxygen. The distribution state of Ag on the catalysts is closely related to the Ag–support interactions and the active sites on the support. Experimental analyses and density functional theory (DFT) calculations have revealed a more even dispersion of the Ag species on the C-type catalyst; differential charge density and Bader charge analysis have confirmed that the Ag loadings can alter the surface charge arrangement, resulting in stronger electronic interactions between Ag and the Sm2Ce2O7-C support. Uniformly dispersed Ag species can effectively promote the activation of gaseous O2 molecules, which is key in the oxidation of soot particles. This approach provides a promising strategy for developing more applicable catalysts for soot combustion.

The Role of Synthesis Methods of Ceria-Based Catalysts in Soot Combustion.

The removal of soot particles via high-performance catalysts is a critical area of research due to the growing concern regarding air pollution. Among various potential catalysts suitable for soot oxidation, cerium oxide-based materials have shown considerable promise. In this study, CeO2 samples obtained using a range of preparation methods (including hydrothermal synthesis (HT), sonochemical synthesis (SC), and hard template synthesis (TS)) were tested in soot combustion. They were compared to commercially available material (COM). All synthesized ceria catalysts were thoroughly characterized using XRD, RS, UV/Vis-DR, XPS, H2-TPR, SEM, and TEM techniques. As confirmed in the current study, every tested ceria sample can be used as an effective soot oxidation catalyst, with a temperature of 50% soot conversion not exceeding 400 °C in a tight contact mode. A strong correlation was observed between the catalysts' Ce3+ concentration and activity, with higher Ce3+ levels leading to improved performance. These findings underscore the importance of synthesis in optimizing ceria-based catalysts for environmental applications.

Optimizing combustion efficiency and environmental impact: the influence of SUPERTHERM K2R coal catalyst

ABSTRACT In the contemporary energy landscape, coal remains a dominant choice due to its widespread availability and cost efficiency. However, addressing the pressing need to mitigate fuel expenses and emissions demands enhanced operational efficiency. Enter SUPERTHERM K2R, a versatile combustion catalyst meticulously crafted to optimize the combustion process of Coal/Petcoke, the primary fuels across various industries. This innovative solution aims to curtail direct fuel consumption by 10–15%, offering efficacy across diverse coal variants including Indian, Indonesian, Australian, South African, US Coal, and Petcoke. The key advantages of this coal additive encompass reduced coal usage, diminished pollutant emissions, decreased trace metal presence, and mitigated land degradation resulting from mining activities. There are some auxiliary advantages with this product like – reduction in coal crusher power consumption, reduce forced draft (FD) fan power consumption, reduce coal handling cost because of less coal consumption as compare to normal operation of industry. In case of power plant increased consumption of demineralized (DM) water has been observed.

Support effect on methane combustion over iridium catalysts: Unraveling the metal-support interaction mechanism.

The redox properties of iridium (Ir) active component are critically important in methane combustion. Interface engineering is highly effective in modulating the redox properties of active metals via tailoring the metal-support interaction (MSI). Herein, Ir catalysts supported on different carriers (TiO2, CeO2, Al2O3) were synthesized and evaluated for methane combustion. The methane combustion performance varied depending on the support, following the order: Ir/TiO2>Ir/CeO2>Ir/Al2O3 catalysts. Detailed experimental characterizations indicate that, compared with stronger Ir-CeO2 and Ir-Al2O3 interfaces, the unique moderate Ir-TiO2 interface facilitates the generation of an electron-rich Ir structure with a higher Irδ+ ratio. Theoretical simulations further suggest that the initial cleavage of the CH bond in methane molecules is favored at the superior Ir-TiO2 interface. The more reactive Irδ+ species with electron-rich structures in Ir/TiO2 catalysts not only greatly enhance their redox performance but also lower the activation energy barrier for methane activation, ultimately leading to improved catalytic activity in the total oxidation of methane. This work provides valuable insights for the ingenious catalyst design of more efficient Ir-based catalysts for methane combustion through tailoring MSI.

Progress in palladium-based bimetallic catalysts for lean methane combustion: Towards harsh industrial applications

<p>Significant volumes of lean methane (0.1–1.0 vol%) are released untreated into the atmosphere during industrial operations, contributing to the greenhouse effect and energy wastage. Catalytic methane combustion presents a promising avenue to mitigate these emissions. Depending on their active components, catalytic systems are predominantly categorized into noble metal-based and non-noble metal-based catalysts, with palladium (Pd)-based catalysts recognized for their superior low-temperature oxidation activity. Nevertheless, enhancing the thermal stability of Pd remains challenging, complicated by impurities such as H<sub>2</sub>O, SO<sub>2</sub> and H<sub>2</sub>S in the lean methane stream, which can cause catalyst poisoning and deactivation. Recent research has focused on the design of Pd-based bimetallic catalysts, offering improved stability, activity, and resistance to poisoning in harsh industrial conditions. This review examines advancements in improving the deactivation resistance of Pd-based bimetallic catalysts for lean methane combustion, covering active site characterization, dispersion and metal-support interactions, the role of auxiliary metals, and structural modulation strategies. It also investigates the impact of harsh industrial environments on Pd-based catalyst performance, focusing on deactivation mechanisms and mitigation strategies. Ultimately, this review identifies current research trends and challenges for Pd-based catalysts in demanding applications. By providing insights into the design of Pd-based catalysts with enhanced stability, activity, and resistance to poisoning, this review aims to guide the development of catalysts that meet industrial demands.</p>

Invoking the promotional impact of boron-modification on zirconia supported palladium catalysts for methane combustion

Invoking the promotional impact of boron-modification on zirconia supported palladium catalysts for methane combustion

Engineering surface exposed LaCoO3 perovskite nanotubular catalyst for catalytic combustion of toluene through acid etching

The ability to resist SO2 poisoning is a major technical challenge for catalysts in VOCs flue gas. In this study, we prepared a series of nanotubular perovskite-based catalysts using an...

The Effect of H2O2 Pretreatment on TiO2-Supported Ruthenium Catalysts for the Gas Phase Catalytic Combustion of Dichloromethane (CH2Cl2)

In the study presented herein, a series of TiO2-supported Ru catalysts were prepared through over-impregnation with different amounts of H2O2 and applied to the catalytic combustion of dichloromethane (DCM). The experimental results show that the optimal (1 H2O2)-Ru@TiO2 catalyst sample yields 90% DCM conversion at 301 °C, which is 40 °C lower than the temperature required by the (0 H2O2)-Ru@TiO2 catalyst. This good activity is related to its high number of acid sites (especially Brønsted acid sites), an appropriate amount of uniformly dispersed RuO2 particles, and strong interaction between RuO2 and the TiO2 support. In addition, excessive H2O2 leads to the growth and phase segregation of RuO2, which weakens the interaction between RuO2 and the TiO2 support and decreases catalytic activity. Moreover, H2O2 addition also contributes to the stability of catalysts, which possibly results from the re-dispersion of RuO2 on the TiO2 support during the reaction.

Exploring the impact of Nickel on ceria doped Cobalt catalysts for low-temperature catalytic combustion of methane

Reducing methane emissions through complete catalytic oxidation at lower temperatures, using efficient and cost-effective catalysts, holds an importance in various industrial and environmental applications. In this study, we developed a series of bimetallic catalysts by incorporating nickel into ceria-doped cobalt oxide at varying loadings. These catalysts were thoroughly characterized to understand the impact of nickel incorporation on the catalytic performance, and subsequently tested for their efficiency in methane oxidation. To gain a comprehensive understanding of the catalysts' properties, a range of characterization techniques was employed, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), nitrogen adsorption-desorption (BET), Raman spectroscopy, hydrogen temperature-programmed reduction (H2-TPR), and oxygen temperature-programmed desorption (O2-TPD). These methods provided insights into the physicochemical properties of the catalysts and the influence of nickel on their catalytic activity. The catalysts' performance in complete methane oxidation was evaluated in the range of 200–600°C. Water vapour (1.5 vol%) was introduced into the feed stream to study the impact of water vapour on the catalytic performance. Among the catalysts tested, the 15Co15NiCe catalyst exhibited the highest activity, achieving a T50 value at 389°C. The characterization results revealed that the optimal incorporation of nickel led to an increase in active surface oxygen species, the creation of lattice defects, an enlarged surface area, and enhanced reducibility, all of which contributed to an improved catalytic performance. Kinetic analysis showed that the calculated activation energy aligned with the observed methane oxidation activity trends. Furthermore, the best-performing catalyst demonstrated an exceptional stability over extended reaction times, with stability tests conducted over 12 hours revealing minimal variation in conversion efficiency. Post-reaction characterization of the spent catalyst using thermogravimetric analysis (TGA) and temperature-programmed oxidation (TPO) provided insights into the slight variations observed during the stability tests. The findings from this study pave the way for the development of low-temperature catalytic processes pretinent to catalytic oxidation of methane.

Efficient synergistic effect of B-acid and oxygen species on CuCe + ZSM-5 for selective catalytic combustion of DMF

The main indicators in the catalytic combustion of nitrogen-containing volatile organic compounds (NVOCs) are high activity at low temperatures and high N2 yield. In this study, CuCe+ZSM-5 catalyst, formed by preferentially forming the complex oxides of Cu species with Ce species and then grinding it with ZSM-5 support, exhibited optimum activity and the high N2 yield during the catalytic N,N-Dimethylformamide (DMF) combustion. The addition of Ce species allowed Cu species to bind to them, preventing Cu species from agglomeration and improving redox capacity. Therefore, for CuCe+ZSM-5 catalyst, the majority of Cu species were present in combination with Ce species, thereby enhancing the reactivity of the oxygen species. This promoted the cleavage of the amide bond, thereby enhancing the activity at low temperatures. In addition, B-acid site facilitated the preferential dissociation of the N-CH3 bond, resulting in the formation of the N–H bond. This resulted in the N species remaining unoxidized, thereby enhancing N2 yield. CuCe+ZSM-5 catalyst avoided the covering of B-acid sites during the calcination, in comparison to CuCe/ZSM-5 catalyst, promoting the selective oxidation of N species. This work provides a new strategy for designing efficient catalysts for catalytic NVOCs combustion.

Investigation of Combustion Properties Optimizing of Composite Modified Double Base Propellant Containing CL-20

Abstract The effect of combustion catalysts which are several proportions of A-Pb, A-Cu and carbon on the combustion properties of composite modified double base (CMDB) propellant containing hexanitrohexaazaisowurtzitane (CL-20) were investigated by uniform design. The proportion of the three materials is optimized. The result shows that A-Pb, A-Cu and carbon can affect the combustion properties of CL-20-CMDB propellant. The effect of single A-Pb or carbon on the propellant combustion properties is obvious between 2 MPa and 8 MPa. The effect of single A-Cu on the propellant combustion properties is obvious between 14 MPa and 22 MPa. There is positive interactions of carbon with A-Pb or A-Cu between 2 MPa and 4 MPa and A-Pb with A-Cu or carbon are obvious. The calculation shows that the effect on adjusting the combustion properties of CL-20-CMDB propellant when the proportion of A-Pb, A-Cu and carbon is 3/0.8/0.2.

Microwave-absorbing property, chemical adsorption, and catalytic activity of monolithic LamMnnOx catalyst in microwave catalytic combustion of toluene

To verify the catalytic activity of LamMnnOx (m,n = 1,2; x = 2.5 ∼ 5.5) catalyst in microwave catalytic combustion of volatile organic compounds (VOCs), monolithic LamMnnOx catalysts were prepared and applied in toluene oxidation in this study. The research demonstrated that the LamMnnOx catalysts had strong microwave-absorbing properties due to first dielectric loss and secondary magnetic loss. The bed temperature rose rapidly due to the formation of hotspots under microwave irradiation. Furthermore, LamMnnOx catalysts chiefly adsorbed toluene by chemical adsorption, and the adsorption capacity of Mn was much stronger than that of La. Based on the activity tests, La1Mn1Ox (x = 2.5 ∼ 3.5) catalyst exhibited the highest catalytic activity among the four catalysts, and toluene was converted and mineralized completely at 259 ℃ and 315 ℃, respectively, under the conditions of an initial toluene concentration of 1000 mg/m3, bed height of 150 mm, and gas velocity of 2.5 L/min. Highly active LaMnO3 perovskite, uniform distribution of active particles, and abundant oxygen vacancies ensured the high activity of the La1Mn1Ox catalyst. Hence, the La1Mn1Ox catalyst was stable after a total of 600 min of activity test. According to electron transfers on the active Mn surface, the adsorption and activation of gaseous oxygen, and the transformation of Oads to Olatt on the oxygen vacancies, toluene oxidation speculates to follow the Langmuir-Hinshelwood and the Mars-van Krevelen mechanisms simultaneously. Therefore, this work provides further technological support for applying LamMnnOx catalysts in microwave catalytic combustion of industrial VOCs waste gas.

Enhanced NOx-assisted soot combustion by cobalt doping to weaken mullite Mn-O bonds for lattice oxygen activation

Catalytic combustion is widely regarded as the most efficient technique for removing soot particulates from diesel engine exhaust, with its efficiency largely dependent on the performance of catalysts. In this study, a series of YMn1−xCoxO5-ζ catalysts were synthesized using a hydrothermal method to investigate their catalytic properties in soot oxidation. Among these catalysts, YMCo-0.2 exhibited the highest catalytic activity, achieving 90 % soot conversion at 392 °C and demonstrating robust tolerance in the presence of water vapor and SO2. Structural characterization revealed that Co doping did not alter the fundamental crystal structure of YMn2O5 mullite. Through some characterization comprehensive analysis, and DFT calculations further supported the experimental findings, indicate that Co substitution significantly increased the lattice oxygen mobility and surface active oxygen content. Compared to the surface lattice oxygens at other positions, the weakening of the Mn-O bond results in the lattice oxygens in the Co-O-Mn4+ sites in the catalysts exhibiting higher reactivity. Additionally, the catalyst displayed strong NO and O2 adsorption and activation capabilities, indicating its potential for efficient NOx-assisted soot combustion. This study provides insights for designing and optimizing mullite catalysts for soot combustion.

High‐Throughput Screening of Dual‐Atom Catalysts for Methane Combustion: A Combined Density Functional Theory and Machine‐Learning Study

AbstractCeria‐supported precious metal catalysts have undergone extensive investigation for the catalytic methane combustion. However, it remains a significant challenge to achieve both highly synergistic oxidation activity and efficient atom utilization remains a challenge for commonly used supported nanoparticles and single‐atom catalysts. Dual‐atom catalysts (DACs) emerges as a frontier of advanced catalysts, presenting unique catalytic properties that benefit from the synergy of neighboring metal sites. In this study, 361 ceria‐supported DACs (M1M2/CeO2) encompassing combinations of 19 transition metals are systematically explored. Using high‐throughput density functional theory calculations, the structures, stability as well as activity of M1M2/CeO2 are assessed. Notably, Au1Ga1/CeO2 is identified as a promising DAC exhibiting high activity for methane total oxidation, substantiated by comprehensive DFT‐calculated reaction pathways. Furthermore, employing six machine‐learning algorithms, the structure‐properties relationship is explored within ceria‐based DACs and highlight the importance of oxidation states and atomic radii of doped metals as the descriptors. The trained model by computational dataset exhibits high accuracy and predict a more active Mn1Au1/CeO2 than those screened using only DFT datasets. The high‐throughput strategy demonstrated in this work not only provides insights into the rational design of methane oxidation catalysts, but also paves the way for exploring DACs for diverse applications.

Electrochemical synthesized copper mesh catalysts for catalytic combustion: A comprehensive study of Mn doping and atmospheric conditions during calcination

Metal-based monolithic catalysts offer significant advantages in heterogeneous catalysis attributed to their exceptional thermal conductivity and mechanical strength. However, controlling the loading of active components on metallic substrates remains a major challenge. Here, we synthesized a Mn-doped Cu mesh catalyst using a facile electrochemical method, allowing the active components to grow directly on Cu mesh without extra pretreatments or binding agents. The synthesized catalyst exhibits approximately a 30 % increase in carbon monoxide oxidation activity at 100 °C and a 60 % increase in toluene oxidation activity at 240 °C compared to the Mn-free Cu mesh catalyst. We found that calcination in inert gases enhances interactions between Cu and Mn species, leading to more oxygen vacancies and adsorption sites for reactants. This investigation paves the way for fabricating multi-metal monolithic catalysts on metallic substrates.

Boosting catalytic activity of Pd/LaxCe1-xMnO3 catalysts in methane combustion by a plasma-treated strategy

An innovative plasma-treated strategy was employed to prepare LaxCe1-xMnO3 (LCMO) perovskite oxides. Pd nanoparticles were loaded onto plasma-treated (P) and air-calcined (T) LCMO respectively, forming the corresponding Pd/LCMO catalysts. The results indicated that the introduction of Pd and plasma treatment largely boost the catalytic activity in methane combustion. Among these catalysts, the Pd/LCMO-P catalyst shows the best performance in CH4 oxidation, giving T90 of 425 °C. It was revealed that the morphology structure and surface defects were strongly affected by plasma treatment, further affecting the dispersion and chemical state of Pd species via surface interaction. The superior performance should be ascribed to the good redox properties (high Mn4+/Mn3+ ratio), rich surface-active oxygen species, and enhanced oxygen mobility (weakened Pd-O and Mn-O chemical bonds). Besides, the distributions of cerium in the surface and crystal lattice of LMO also improved metal-support interaction and the oxygen mobility, that boosted CH4 oxidation. This plasma-treated strategy provided an effective path to develop the efficient combustion catalyst for superior performance.

Captivating Combustion Traits of Bio-Oil Droplets Enriched with Bio-Additives from the Areca Shell Waste

Fuel derived from crude vegetable oil, such as coconut oil, holds promise as an alternative energy source to mitigate the increasing reliance on fossil fuels driven by population growth and industrial activities. The experiment involved suspending a single droplet of crude coconut oil mixed with activated carbon from areca shell waste and placed at the junction on R-type thermocouple (Pt/Pt-Rh13%). The droplets were ignited using a hot wire and subjected to atmospheric pressure and room temperature. Coconut oil comprises a saturated triglyceride carbon chain compound of approximately 91%, and areca shell waste possesses a porous structure that fosters favorable interactions between fuel molecules. The droplet combustion method was selected to streamline the process and enhance the contact area between air and fuel, thereby boosting the reactivity of fuel molecules. The research found that adding activated carbon shortens the carbon chain, making it more reactive and easier for the fuel to ignite. Specifically, activated carbon significantly enhances fuel performance at a concentration of two parts per million (ppm). At this level, the fuel absorbs heat more effectively and ignites faster compared to one ppm and three ppm levels. Moreover, the results show that heat absorption occurs slowly at one ppm, while at three ppm, the increased molecular mass of the fuel can strengthen carbon-bonding forces. These factors contribute to a longer ignition time for the fuel. The findings suggest that the activated carbon from areca shell waste can play a good role as a combustion catalyst, where overall, fuel performance increases.

Synergistic effect as a function of preparation method in CeO2-ZrO2-SnO2 catalysts for CO oxidation and soot combustion

The development of catalysts based on environmentally desirable components is a topical challenge. In the present work, we consider the effects of the preparation method on phase composition, porous structure, nature and distribution of active sites as well as synergistic behavior of components in two series of CeO2-ZrO2-SnO2 catalysts for soot combustion and CO oxidation. The catalysts prepared by the citrate method feature rather large SnO2 aggregates distributed on CeO2 and/or ZrO2 oxides. On the contrary, the catalysts prepared by the CTAB-templated approach feature a uniform distribution of oxide species and usually show higher activity in both CO oxidation and soot combustion. In both series, the activity and characteristics of catalysts are enhanced due to the synergistic effects arising when two or more oxide components coexist in their composition, and the degree of synergy is a function of the preparation method. The features of the most active catalysts combine (1) high specific surface area and pore volume, (2) high microstrain values, (3) coexisting oxygen vacancies of different nature, (4) high H2 consumption at low temperatures, and (5) high fraction of adsorbed active oxygen species.

Ceria-zirconia solid solution supported platinum catalysts for toluene oxidation: Studying the improved catalytic activity by tungsten addition

The catalytic oxidation of toluene at low temperatures is still an urgent issue to be solved. The key to addressing this issue is the preparation of a high-efficiency catalyst. Herein, ceria-zirconia (CZ) solid solution supported platinum (Pt) catalysts were prepared by citric acid (C)-assisted impregnation method. Surprisingly, the catalytic oxidation activity of the catalyst for toluene combustion significantly improved after introducing W into Pt-C/CZ. In addition, introducing W improved the redox property of the Pt-based catalyst, optimized the distribution of the oxygen vacancies, increased the average particle size of the catalyst particle, modulated the valence state and electronic structure of Pt, elevated the surface lattice oxygen activity, increased the number of surface moderate acidic sites and enhanced toluene adsorption capacity. In this study, the electronic structure of the Pt active site is modulated by introducing a W promoter, providing valuable guidance for the rational design of efficient noble metal catalysts.

Surface in situ Co-Mn modification over LaMnO3 perovskite with enhanced activity for ethane combustion

Catalytic combustion is one of effective ways to remove short-chain alkanes. In this study, we elaborately designed a novel catalyst of in situ Co-Mn decorated LaMnO3 perovskite for ethane catalytic combustion, in which extra Mn and Co species were introduced via acidic KMnO4 and Co(NO3)2 solution precipitation method. The addition of Mn and Co could not only slightly etch LaMnO3, thereby increasing specific surface area and redox property, but also generate new active phase CoMn2O4, thus accelerating reaction. Among all the as-prepared catalysts, CMO/LMO-0.5 exhibited admirable ethane removal efficiency with a T90 of 365 °C, a reaction rate of 0.46 mmol·g−1·h−1, a TOF value of 0.64 mmol·g−1·h−1, and excellent hydrothermal stability and reusability. Moreover, according to in situ DRIFTS, a possible pathway was proposed. This work can rationalize an alternative approach to develop an active catalyst for short-chain alkanes catalytic combustion or other catalytic systems.