Combustion Of Volatile Organic Compounds Research Articles

SO2-resistant hollow carbon spheres encapsulated Pt nanoparticles for benzene oxidation

In the catalytic combustion of volatile organic compounds (VOCs) using noble metal catalysts, resistance to SO2 poisoning poses a significant challenge. To tackle this problem, Pt nanoparticle catalysts encapsulated in hollow carbon spheres (Pt@HCS catalysts) are synthesized. The Pt@HCS catalyst exhibits excellent benzene conversion, achieving 100 % conversion at 165 °C under an air velocity of 20,000 mL/(g h). Compared to the conventional supported Pt/HCS catalyst, the Pt@HCS catalyst demonstrates a significantly improved resistance to SO2 poisoning. In the presence of 25 ppm SO2, the Pt@HCS catalyst is capable of maintaining a 100 % benzene conversion rate within 24 h, whereas the conversion rate of Pt/HCS drops substantially to approximately 52 %. It is confirmed that the hollow porous structure provided a larger specific surface area and more adsorption sites, thereby facilitating benzene oxidation. More importantly, in situ DRIFTS reveals that the adsorption and desorption processes of SO2, along with the generation of substances like SO32−, are strictly limited to the surface of the carbon shell, thereby preserving the integrity of the internal reaction environment. Multiple characterizations combined with density functional theory (DFT) have demonstrated a unique separation effect over Pt@HCS, whereby the hydroxyl groups on the carbon shell preferentially capture SO2 while allowing benzene molecules to enter the cavities of the catalyst. In this way, any internal ingress of SO2 and competition with benzene for Pt adsorption is effectively avoided. This study offers a potential solution to enhance the performance of noble metal catalysts in the presence of sulfur compounds.

Efficient catalytic combustion of propane at low temperature based on ignition effect caused by amorphous atomic-layer Pt clusters

Developing highly active catalysts for hydrocarbon combustion at low temperatures is paramount but yet challenging. The crystal form of carrier and the dispersion degree of active species have great influence on propane combustion catalysts, but its internal mechanism is still unclear. In this study, the amorphous atomic-layer Pt clusters (AL) and Pt single atoms (SA) on TiO2 with various crystal phases were prepared and used as propane combustion catalysts, where the as-synthesized Pt/a-TiO2 catalyst with atomic-layer Pt clusters exhibited better catalytic performance. The Pt/a-TiO2-AL could achieve a 90 % propane conversion (T90) at 230 °C, with the highest reaction rate (39.57 × 10−7 mol g−1 s−1) and TOF value (7.72 × 10−2 s−1) at 240 °C. Kinetic studies showed that oxygen had a lower inhibitory effect on Pt/a-TiO2-AL compared to that on the Pt/p-TiO2-AL and Pt/r-TiO2-AL catalysts; simultaneously, the Pt/a-TiO2-AL catalyst presented lower apparent activation energy compared with Pt/a-TiO2-SA. DFT results showed that atomic-layer Pt clusters on TiO2 had the lower formation energy of oxygen vacancy than Pt single atoms due to the synergistic effect between adjacent exposed Pt atoms in the fully exposed atomic-layer Pt clusters, which had a higher activation capacity for oxygen and thus accelerated propane combustion through the ignition effect (rapid activation of oxygen and rapid combustion of propane). Our primary results provide a promising approach for the creation of high-efficiency Pt-based catalysts, specifically tailored for the catalytic combustion of volatile organic compounds (VOCs).

Nanocrystalline FeMnO3 Powder as Catalyst for Combustion of Volatile Organic Compounds.

The paper shows the obtaining of nanocrystalline iron manganite (FeMnO3) powders and their investigation in terms of catalytic properties for a series of volatile organic compounds. The catalyst properties were tested in the catalytic combustion of air-diluted vapors of ethanol, methanol, toluene and xylene at moderate temperatures (50-550 °C). Catalytic combustion of the alcohols starts at temperatures between 180 °C and 230 °C. In the case of ethanol vapors, the conversion starts at 230 °C and increases rapidly reaching a value of around 97% at 300 °C. For temperatures higher than 300 °C, the degree of conversion is kept at the same value. In the case of methanol vapors, the conversion starts at a slightly lower temperature (180 °C), and the degree of conversion reaches the value of 97% at a higher temperature (440 °C) than in the case of ethanol, and it also remains constant as the temperature increases. Catalytic combustion of the hydrocarbons starts at lower temperatures (around 50 °C), the degree of conversion is generally lower, and it increases proportionally with the temperature, with the exception of toluene, which shows an intermediate behavior, reaching values of over 97% at 430 °C. The studied iron manganite can be recommended to achieve catalysts that operate at moderate temperatures for the combustion of some alcohols and, especially, ethanol. The performance of this catalyst with regard to ethanol is close to that of a catalyst that uses noble metals in its composition.

Nickel foam based monolithic catalyst supporting transition metal oxides for toluene combustion: Experimental and theoretical study of interfacial synergistic oxidation and water resistance

Composite oxides obtained by calcining layered double hydroxides (LDHs) were used to construct a functional hydrolysis interface. Using nickel foam (NF) as a carrier, LDH was produced on the surface of this monolithic catalyst. The original morphology was retained after calcination. NF provided better thermal conductivity for catalytic combustion than conventional cordierite carriers. The clear phase interface between the different mixed metal oxides (CuxCo3-xFe-MMO/NF) promoted oxidation and hydrolysis during toluene combustion. Physicochemical investigations were performed using XRD, SEM, TEM, H2-TPR, ESR, and XPS. GC–MS, in situ DRIFT, H2O-TPD, and DFT were also used to explore the deep hydrolysis mechanism. The dissociation of water to form the surface *OH was the main hydrolysis process owing to the existence of the Cu-Co functional interface, with the largest energy emission (0.56 eV from DFT calculations). This hydrolysis process also altered the toluene degradation pathway, as confirmed by the in situ DRIFTS and GC/MS results, which guaranteed significant stability of the Cu1Co2Fe-MMO/NF catalyst in a highly humid environment and the removal efficiency and mineralization of toluene were both >90 % below 270 °C. This monolithic catalyst exhibits excellent water resistance and the toluene conversion rate remained stable at 90 % without any attenuationhas >40 h, which provides potential utility in the combustion of volatile organic compounds in high-humidity industrial streams.

Engineering Co3O4@3DOM LaCoO3 multistage-pore nanoreactor with superior SO2 resistance for toluene catalytic combustion.

Sulfur dioxide poisoning is a significant factor in catalyst deactivation during the catalytic combustion of volatile organic compounds. In this study, we prepared the LaCoO3 and Co3O4 composite catalysts using both the Ship-in-Bottle and Building-Bottle-Around-Ship approaches. Three-dimensionally ordered macropores (3DOM LaCoO3) were utilized as nanoreactors to protect the active sites during the catalytic combustion of toluene, preventing SO2 poisoning. Additionally, we grew ZIF-67 confined in the nanoreactor to create a multistage-pore structure. The Co3O4@3DOM LaCoO3 catalysts exhibited excellent activity in the complete catalytic oxidation of toluene. Various characterization studies confirmed the presence of a significant number of Co3+ species and an abundance of surface weak acid sites in the Co3O4@3DOM LaCoO3 catalysts, which synergistically enhanced the conversion of VOCs at low temperatures. Notably, the multistage pore structure provided a favorable reaction environment, accelerating the adsorption and diffusion of toluene and intermediates, resulting in excellent sulfur resistance of the catalysts. Moreover, XPS analysis confirmed a strong interaction between Co3O4 and LaCoO3, promoting rapid electron transfer and increasing the activation of O2-. In situ DRIFTS experiments verified that toluene mainly follows the MvK mechanism over Co3O4@3DOM LaCoO3 catalysts, indicating the following reaction pathway: toluene adsorption → benzyl alcohol → benzaldehyde → benzoate → anhydride → CO2 and H2O.

Catalytic performance of mesoporous Mn-Co-Ti for o-xylene degradation: Mechanistic study under practical conditions

Catalytic combustion of volatile organic compounds from industrial flue gases at low temperatures remains a challenge. Herein, we developed a mesoporous Mn-Co-Ti catalyst for o-xylene degradation by a solvothermal strategy. The optimized Mn0.1Co-TiO2 catalyst possessed a nanoflower structures with a surface area of 83.1 m2/g and mesoporous volume of 0.1191 cm3/g. Mn-doping modulated the electronic interactions between Mn and Co, which promoted the formation of MnCo2O4.5 phase and increased Co3+ and Mn4+ content of the catalyst. The Mn0.1Co-TiO2 catalyst had an improved reduction capacity from 170 to 644 °C, with a maximum H2 consumption of 4.56 mmol/g. The Mn0.1Co-TiO2 catalyst achieved 50% o-xylene conversion at 193 °C at a GHSV of 60,000 h−1, whereas the equivalent catalyst prepared by impregnation required 315 °C for 50% o-xylene conversion. In the presence of NO, the generated NO2 accelerated o-xylene conversion because it promoted the generation of more Mn4+-O-Co3+ active sites and accumulation of intermediates such as maleate and acetate species. NH3 and H2O had slight inhibitory effects on o-xylene conversion, which were attenuated by abundant mesopores and redox ability of catalyst. SO2 gas caused inactive sulfates and chemical deactivation on catalyst surface, thus leading to excessive formation of benzoquinone products.

Polymer template assisted construction of spherical Co3O4@meso-SiO2 yolk-shell nanoreactors for catalytic combustion of volatile organic compounds

Co3O4@SiO2 yolk-shell materials containing Co3O4 nanoparticles protected against aggregation and easily accessible for gaseous reactants inside a mesoporous SiO2 shell were developed for the catalytic combustion of volatile organic compounds (VOCs). Spherical polymer templates with an appropriate cation adsorption capacity were used as scaffolding for the construction of these structures by the bottom-up strategy. An application of polystyrene led to accumulation of introduced cobalt phase within the SiO2 layer and favored the formation of catalytically inactive Co silicate species. On the other hand, poly(maleic anhydride-co-divinylbenzene) modified with diethylenetriamine gave improved penetration of the composite interior by Co2+ cations and highly dispersed Co3O4 nanoparticles after calcination. The latter materials appeared excellent nanoreactors for the catalytic combustion of toluene. The real role of the active phase was determined by characterization of the developed catalysts with XRD, N2 adsorption, SEM-EDS, TEM, UV–Vis-DR, FT-IR, H2-TPR, isothermal oxidation-reduction analyses, XPS, XAS and electrochemical measurements.

Effect of pH on mussel shells-originated HAP supported Ag catalysts for catalytic combustion of VOCs

Volatile organic compounds (VOCs) triggered serious air pollution and mussel shell caused the marine environmental issues. Herein, hydroxyapatite (HAP) using mussel shells as calcium source was prepared by hydrothermal method with different pH (pH = 6, 8, 10, 11) controls to support Ag catalyst for removal of VOCs. It was found that the amount of skeletal hydroxyl species and textual properties of HAP were controlled by pH effectively, and the increase of hydroxyl groups in the framework resulted in forming smaller-sized Ag2O particles. When pH was 8, the Ag/HAP-BpH=8 catalyst exhibited 100 % conversion of ethyl acetate and toluene at 260 °C and 300 °C, respectively. Silver species were more likely existed on the surface of HAP-BpH=8 to form large-size Ag particles (6.4 nm) and more Ag2O species. The lower ratio of Ag0/Ag+ were crucial for improving the VOCs oxidation activity at lower temperatures. This work applied waste mussel shells to prepare high value-added Ag/hydroxyapatite catalysts and to promote VOCs catalytic oxidation.

Catalytic Combustion of Volatile Organic Compounds (VOCs) over Perovskite Oxides: A Review

Volatile organic compounds (VOCs) are one of the crucial outdoor as well as indoor air pollutants. Recently, the elimination of volatile organic compounds is become more attractive due to its potentiality of long-term human health effects. Among the different existing methods for the removal of VOCs, the catalytic combustion is the best convenient method due to its operational simplicity, cost effectiveness, high efficiency and industrial acceptability. Various perovskite oxides have been widely studied as suitable catalysts for the removal of VOCs because of their tunable physico-chemical properties, compositional/structural exibility and high thermochemical stability. The morphology, material composition and surface as well as bulk properties of perovskite oxides is the key determining factors for catalytic efficiency. The suitable metal or non-metal doping, controlling morphology (nano-structuring, three-dimensional ordered microporous (3DOM) building) and hybrid construction (perovskite as support for other active catalysts and other oxides as support for active perovskite catalyst) may have a remarkable effect on the surface as well as bulk properties and consequently the catalytic efficiency for ther removal reactions of VOCs are also effected. In this review article, different aspects of the current development in perovskite oxides catalysts for VOCs combustion with a special highlighting on the material designing, like doping, morphology controlling, surface modication and hybrid construction are presented.

Combustion of volatile organic compounds in a domestic microwave oven using regenerable sorbent-catalyst combinations

Volatile Organic Compounds (VOCs) traps that could easily be regenerated while simultaneously destroying the desorbed VOCs would represent a major breakthrough. A domestic microwave (MW) oven was used here at a power of 800 W to regenerate sorbents loaded with toluene, n-decane or formaldehyde and then combust the released VOCs on a MW-absorbing catalyst. Porous polymer Tenax and various zeolites were tested as sorbents and base metal oxides were employed as combustion catalysts. The locations of the sorbent and catalyst beds were chosen to allow for a strong MW absorption by the catalysts, some of which glowed red within 3 s after turning on the MW, allowing essentially full combustion (above 98 % conversion) of the VOCs to CO2 and H2O. Water (0.6 vol%) neither affected the sorption of toluene and n-decane in Tenax and that of formaldehyde in silicalite-1 nor the combustion of these VOCS over a La-Ce-Mn-O catalyst.

Surface oxygen vacancy-dependent molecular oxygen activation for propane combustion over α-MnO2

Oxygen vacancies (OV), as the sites of molecular oxygen adsorption and activation, play an important role in the catalytic combustion process of volatile organic compounds (VOCs). Revealing the relationship between OV concentration and molecular oxygen activation behavior is of significance to construct the efficient catalysts. Herein, α-MnO2 with different OV concentrations was prepared to investigate the molecular oxygen activation for C3H8 combustion. It is disclosed that the enhanced OV concentration in α-MnO2 induced the reconfiguration of surface metal atoms, resulting in the transformation of oxygen activation configuration from end-on mode to side-on mode. Oxygen molecules in side-on mode possessed more localized electron density and weaker coordination bond strength with surrounding Mn atoms, which were more favorable to adsorb C3H8 molecules and activate C-H bond for the improved combustion performance. This work provides a new understanding to reveal that the increased OV concentration contributes to more efficient VOCs combustion.

Catalytic combustion of volatile organic compounds using perovskite oxides catalysts—a review

Catalytic combustion of volatile organic compounds using perovskite oxides catalysts—a review

Engineering Ag-O-Mn bridges with enhanced oxygen mobility over Ag substituted LaMnO3 perovskite catalyst for robustly boosting toluene combustion

Perovskite oxide, as a promising candidate for volatile organic compounds combustion, is incapable in practical application at present due to its low intrinsic activity resulting from inadequate active oxygen species. However, balancing the concentration of active oxygen species and robust structure for perovskite oxide is still challenging. Herein, an efficient perovskite-based catalyst (denoted as TA-La0.9Ag0.1MnO3) was constructed through Ag substitution and subsequently tartaric acid etching of LaMnO3, which exhibits robustly boosted catalytic performance for toluene combustion compared with pristine LaMnO3, causing a ∼100 °C lower T90. In this study, Ag substitution could weaken the La-O hybridization, which effectively facilitates La cations removal by subsequent acid etching, thus sufficiently exposing active Ag and Mn species and generating more surface lattice oxygen, but also constructs Ag-Mn-O bridges within the matrix of Ag substituted LaMnO3. Acid etching enables the activation of Ag-O-Mn bridges with strong electron transfer ability from O to Ag atom, promoting the mobility of lattice oxygen, and consequently the low-temperature oxidation ability. Additionally, the exposed Ag and Mn as Lewis acid sites can effectively improve the adsorption capacity toward toluene molecules, which synergistically facilitates the toluene abatement. Notably, TA-La0.9Ag0.1MnO3 also exhibits superb long-term stability, water-resistance, and high thermal stability up to 650 °C.

Novel Control System Strategy for the Catalytic Oxidation of VOCs with Heat Recovery

A theoretical study of the dynamic closed-loop behaviour of a reactor/feed-effluent heat exchanger (FEHE)/furnace system for the catalytic combustion of volatile organic compounds (VOCs) is presented. A 1D pseudohomogeneous plug-flow model is proposed to simulate the non-steady-state operation of the monolith reactor and the FEHE, while the furnace behaviour is described by means of a heterogeneous model of lumped parameters. Positive energy feedback is a source of instability that leads to strong thermal oscillations (limit cycles) and may cause damage to the equipment and sintering of the catalyst. The design of a robust and flexible control system and an efficient control strategy are, therefore, required to ensure safe and stable operation. The response of the system under three different control strategies to the most frequent disturbance variables—the feed flowrate (FV0) and feed concentration of VOCs (C0Et)—was evaluated. One of the control strategies consisted of a single-loop feedback system with servomechanism changes in the reactor inlet temperature (T0) that manipulated the bypass valve and, sequentially, the natural gas flowrate in the furnace (FNG). This approach made it possible to meet the control objective (reducing VOCs) without losing controllability and while minimizing the use of external fuel.

Insights into enhancing SO2 tolerance for catalytic combustion of toluene over sulfated CeZrOx supported platinum catalysts

Supported platinum catalysts are widely used in the catalytic combustion of volatile organic compounds due to their excellent catalytic activity, but SO2 poisoning is one of the critical problems for the industrial application. In this work, a series of sulfated ceria-zirconia composite oxides (CeZrOx) supported platinum catalysts (Pt/CeZr-S) were prepared through the support sulfation strategy. In the catalytic combustion of toluene, the Pt/CeZr-S catalyst with 0.5 wt% Pt and 15 wt% sulfuric acid loading amounts exhibited the significantly increased activity compared with the reference Pt/CeZr catalyst. Moreover, the tolerance to SO2 poisoning of Pt/CeZr-S catalyst was greatly improved in the presence of 50 ppm SO2. Various characterization methods including XPS, NH3-TPD and in-situ DRIFTS were performed to reveal the structure-activity relationship and SO2 tolerance mechanism. The higher concentration of metallic Pt0 species resulting from the interaction of Pt species and acidic CeZr-S support contributed to the enhanced catalytic activity. Meanwhile, the increased acidity strength and total acidity amounts over Pt/CeZr-S catalysts could affect the sulfation process, resulting in significant inhibition of the adsorption and further accumulation of sulfur species.

Heterointerface engineering regulating the energy-level configuration of α-MnO2/δ-MnO2 for enhancing toluene catalytic combustion performance

This work offers a novel approach to prepare manganese oxides with heterointerface structure as a superior catalyst for the catalytic combustion of Volatile Organic Compounds (VOCs). The α-MnO2/δ-MnO2 with heterointerfaces were prepared via annealing δ-MnO2 precursors which were obtained from the redox precipitation between HCl and KMnO4. The characterization results indicate that the heterointerface structure of α-MnO2/δ-MnO2 optimizes energy level structure and provides abundant surface defects, showing superior low-temperature reducibility and preferable mobility of oxygen species. Such features significantly enhance the catalytic activity of the α-MnO2/δ-MnO2 with heterointerfaces catalysts for the complete oxidation of toluene (the toluene conversion rates of 10 % and 90 % are 191 °C and 213 °C, respectively). Moreover, the catalysts show high stability for 50 h. The presented catalysts disclose an avenue to address current obstacles in the catalytic oxidation of VOCs.

Research Progress on Catalytic Combustion of Volatile Organic Compounds in Industrial Waste Gas

Volatile organic compounds (VOCs) emitted from industrial processes have high stability, low activity, and toxicity which cause continuous harm to human health and the atmospheric environment. Catalytic combustion has the advantages of low energy consumption and low cost and is expected to be one of the most effective methods to remove VOCs. At present, the selection of low cost, high activity, and durability catalysts are still a difficult problem. Industrial emissions of VOCs contain a certain amount of aromatic hydrocarbons; these substances are highly toxic substances, and, once inhaled by the human body, will cause serious harm to health. In this paper, the principle, advantages, and disadvantages of VOCs processing technology are analyzed in detail, and the catalytic combustion of aromatic hydrocarbons in VOCs is reviewed, including catalyst, reaction conditions, catalyst selection, inactivation reasons, and structure use. In addition, the deactivation effects of chlorine and sulfur on catalysts during the catalytic combustion of VOCs are discussed in detail. Finally, on the basis of literature research, the prospect of catalytic combustion of VOCs is presented, which provides influential information for further research on VOCs processing technology.

Understanding the mechanisms of catalytic enhancement of La-Sr-Co-Fe-O perovskite-type oxides for efficient toluene combustion

The merits of ABO3-type perovskite oxides as catalysts for volatile organic compounds (VOCs) combustion are that the redox capability of transition metal elements in their lattice structure can be well tailored through a facile doping strategy. In particular, La-Sr-Co-Fe-O perovskite-type oxides possess excellent tunable physicochemical properties, making them an ideal platform for promising prospects in VOCs combustion. This work synthesized a series of La1-xSrxCo1-yFeyO3 (x = 0, 0.3, 0.5, 0.8; y = 0, 0.2, 0.5) perovskites and analyzed their reaction kinetics on toluene combustion. Among all the catalysts, La0.5Sr0.5Co0.8Fe0.2O3-δ (LSCF) showed a remarkable catalytic activity towards the toluene oxidation with T90 of 270 °C at a weight hourly space velocity (WSHV) of 30000 mL·g−1·h−1 and apparent activation energy (Ea) of 44.76 kJ·mol−1 and obtained the superior stability. Based on the characterizations and analysis of in-situ DRIFTS, the outstanding catalytic activity of LSCF perovskite is mainly induced by the improvement of the redox ability, the enriched generation of oxygen vacancies, and the activation of the lattice oxygen species. The catalytic mechanism of toluene conversion over the LSCF perovskite was revealed to be consistent with Mars-van Krevelen (MVK) models. The knowledge obtained in this study provides helpful guidance for designing efficient heterogeneous catalysts of La-Sr-Co-Fe-O perovskite-type oxides toward efficient catalytic combustion for VOCs elimination.

Pd/δ-MnO2 nanoflower arrays cordierite monolithic catalyst toward toluene and o-xylene combustion.

Exploring high-efficiency and stable monolithic structured catalysts is vital for catalytic combustion of volatile organic compounds. Herein, we prepared a series of Pd/δ-MnO2 nanoflower arrays monolithic integrated catalysts (0.01–0.07 wt% theoretical Pd loading) via the hydrothermal growth of δ-MnO2 nanoflowers onto the honeycomb cordierite, which subsequently served as the carrier for loading the Pd nanoparticles (NPs) through the electroless plating route. Moreover, we characterized the resulting monolithic integrated catalysts in detail and evaluated their catalytic activities for toluene combustion, in comparison to the controlled samples including only Pd NPs loading and the δ-MnO2 nanoflower arrays. Amongst all the monolithic samples, the Pd/δ-MnO2 nanoflower arrays monolithic catalyst with 0.05 wt% theoretical Pd loading delivered the best catalytic performance, reaching 90% toluene conversion at 221°C at a gas hourly space velocity (GHSV) of 10,000 h−1. Moreover, this sample displayed superior catalytic activity for o-xylene combustion under a GHSV of 10,000 h−1. The monolithic sample with optimal catalytic activity also displayed excellent catalytic stability after 30 h constant reaction at 210 and 221°C.

Water Enables Lattice Oxygen Activation of Transition Metal Oxides for Volatile Organic Compound Oxidation

A small amount of water can enhance the catalytic combustion activity of volatile organic compounds (VOCs) on transition metal oxides (TMOs), but its intrinsic mechanism is still controversial. Herein, we systematically demonstrate that water molecules can constantly activate lattice oxygen of transition metal oxides to form hydroxyl species theoretically and experimentally. The oxygen atoms of the generated hydroxyl species possess a weak bonding strength with circumjacent metal atoms to easily escape from the surface and attack electron-deficient carbon atoms of VOCs due to their comparatively stronger nucleophilicity, leaving abundant oxygen vacancies as the active sites for subsequent molecular oxygen activation. This work helps us deeply understand the role of water in lattice oxygen activation of transition metal oxides and provides direction for water-related catalysis, such as catalytic VOC combustion, water splitting, water–gas shift reactions, and corrosion.