Toluene Combustion Research Articles

Simplified synthesis of Pt-MnOx supported on three dimensional Co3O4 for catalytic removal of toluene

In this study, a simplified method was developed for synthesizing Pt-(MnOx)/three-dimensional (3D)-Co3O4 catalysts. This approach represents a convenient alternative to the typical procedure of initially synthesizing nanoparticles (NPs) and subsequently depositing them onto supports. The Pt1-(MnOx)1/3D Co3O4 catalyst, with a molar ratio of Pt:Mn=1:1, demonstrated excellent catalytic efficacy at a comparatively low reaction temperature and displayed commendable thermal stability during prolonged operation in the deep oxidation of toluene. The T90 (temperature required for 90% conversion) of Pt1-(MnOx)1/3D Co3O4 was merely 163 °C. Characterization analysis revealed that the catalyst's remarkable catalytic efficiency is attributed to the elevated concentration of oxygen vacancy defects on Pt1-(MnOx)1/3D Co3O4 and its low-temperature reducibility. In situ DRIFTS analysis was conducted to investigate the possible reaction pathway of Pt1-(MnOx)1/3D Co3O4. The results indicated that the rapid dehydrogenation of methyl and the demethylation of toluene facilitate the cleavage of the benzene ring on the Pt1-(MnOx)1/3D Co3O4 catalyst, due to the abundant absorption of oxygen species. This process enhances the catalytic combustion of toluene

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.

Study on the combustion of toluene by acid etching assisted ultrasonic supported low content Pt catalyst

Catalytic combustion technology is an effective method for the treatment of volatile organic compounds (VOCs). However, the catalytic activity of loaded noble metal catalysts is limited by factors such as high noble metal dosage and poor stability. In this study, a method for the preparation of acid etching assisted ultrasonic loaded low-content Pt-cordierite catalysts was proposed. By comparing with the 0.5 % Pt/cordierite catalyst prepared without acid etching, it was found that the catalytic activity of toluene of the 0.5 % Pt/cordierite-HNO3 catalyst was significantly improved, and the T90 of toluene combustion was only 201 ℃, which indicated that the acid etching effectively promoted the interfacial bonding between the active component Pt and the carrier. Finally, it was confirmed by XPS that the active component Pt in the 0.5 % Pt/cordierite-HNO3 catalyst existed in multiple valence states, which effectively promoted the catalytic combustion of toluene.

Tuning the oxygen storage capacity and oxygen release properties of CeO2-based catalysts for catalytic combustion of toluene

CeO2 with varied doping transition metal was investigated to understand the oxygen storage capacity and oxygen release property of CeO2-based catalysts for toluene combustion. The order of catalytic activity was as follows: CuCeOx ≈ CoCeOx > MnCeOx > FeCeOx > NiCeOx > ZrCeOx > CeO2. Kinetic studies showed that the reaction on CuCeOx proceed via an MvK mechanism and the oxygen of catalyst was crucial factor for the toluene combustion. H2-TPR and XPS showed the addition of transition metal to CeO2 could modify the surface lattice oxygen. Moreover, the oxygen storage capacity and oxygen release properties showed the transition metal additive not only change the amount of oxygen, but also affect the oxygen mobility. A linear relationship was observed between the catalytic activity and oxygen storage capacity. Diffuse reflectance infrared fourier transform spectroscopy showed the toluene first adsorbed on the surface of catalyst, and then reacted with oxygen of catalyst to form benzyl, benzoate and benzyl carbonate species. All these results provided a new strategy to develop high performance catalyst.

A Simple Approach to Inducing Oxygen Vacancies in Pt/TiO2 for Efficient Catalytic Combustion of Toluene

A Simple Approach to Inducing Oxygen Vacancies in Pt/TiO2 for Efficient Catalytic Combustion of Toluene

Adjustment mechanism of Co3+ performance in Co3O4-LaOx catalyst for high-efficiency catalytic combustion of toluene

This study employed the sol–gel method to fabricate Co-La catalysts under various calcination temperatures were used to the catalytic oxidation of toluene. The investigation on the impact of calcination temperature on the Co3+ content and the resultant catalytic activity was studied. The CoLa-550 catalyst (calcined at 550 °C) exhibited the highest concentration of Co3+ and optimal catalytic performance for toluene oxidation (T90 = 195 °C). In situ DRIFTS technology confirmed the ring-opening of benzoic acid was the rate-determining step. Comprehensive analyses utilizing XPS, H2-TPR, and O2-TPD revealed the significance of optimizing Co3+ content to enhance catalytic activity. This research provided crucial theoretical and experimental support for the development of efficient non-noble metal catalysts.

Structural Effect of Cu-Mn/Al2O3 Catalysts on Enhancing Toluene Combustion Performance: Molecular Structure of Polyols and Hydrothermal Treatment

Structural Effect of Cu-Mn/Al2O3 Catalysts on Enhancing Toluene Combustion Performance: Molecular Structure of Polyols and Hydrothermal Treatment

Introducing attapulgite to prepare manganese-based monolithic catalyst for catalytic combustion of toluene

A series of attapulgite-loaded manganese oxides cordierite monolithic catalysts with different KMnO4/Mn(NO3)2 molar ratios (3:1, 1:1, and 1:3 for KMnO4/Mn(NO3)2, respectively) were prepared by a hydrothermal-ball mill impregnation method. According to the analysis of the characterization findings, the main active species of the catalyst was Mn4+ species. By incorporating acid-treated attapulgite (HATP) and adjusting the molar ratio of KMnO4/Mn(NO3)2, the content of Mn4+ and surface-adsorbed oxygen species on the catalyst surface increased, subsequently enhancing catalytic activity at low temperatures. Experimental results revealed that the Mn/HATP/cordierite catalyst with a KMnO4 to Mn(NO3)2 molar ratio of 3:1, Mn loading amount of 30 wt%, and active coating deposition of 250 g/L exhibited the highest catalytic activity, achieving a 90 % conversion of toluene at 298 °C (T90 = 298 °C, GHSV = 10000 h−1). These findings will provide valuable support for the design of highly efficient monolithic catalysts for toluene removal.

CFD simulation of a laboratory-scale monolithic reactor for the combustion of VOC

This study presents initial findings from simulating a laboratory-scale monolithic reactor for VOC (Volatile Organic Compounds) combustion. The reactor, made of stainless steel, measures 45 cm (height) and 2.3 cm (diameter). It contains a catalyst supported by a ceramic structure, tested for toluene combustion. Using ANSYS CFD simulation software, fluid dynamics inside the reactor were accurately modeled. The simulation then focused on a specific channel within the monolith, based on comprehensive reactor data. The final stage simulated toluene combustion using the Mars-Van Krevelen mechanism. ANSYS CFD results for toluene combustion, measured by CO2 yield, closely matched experimental outcomes. The average CO2 yield of 1.16 showed a strong alignment between the simulation and the experiment. ANSYS CFD not only aids in obtaining hard-to-gather information about fluid dynamics and chemical reactions but also enables simulations of geometry changes and catalyst types once validated. It also supports exploring more complex reactions.

Performance and Reaction Mechanisms of Catalytic Combustion of Toluene and Ethyl Acetate Over Fe‐Mn Oxides

AbstractIn this paper, Fe−Mn oxide catalysts were prepared by the co‐precipitation method. (Fe2O3)‐(Mn3O4)‐3 : 1 showed the best catalytic activity in the degradation of toluene and ethyl acetate, with the removal rate reaching 90 % at 166 °C and 156 °C respectively. The XRD, SEM, TEM, and XPS characterizations revealed that the interaction between Fe and Mn and the higher surface adsorption of oxygen in the (Fe2O3)‐(Mn3O4)‐3 : 1 catalyst may be the main factors promoting the catalytic oxidation. (Fe2O3)‐(Mn3O4)‐3 : 1 exhibited a better removal rate in ethyl acetate than toluene at different space velocities, concentrations and water contents. Under the same conditions, the degradation rate of (Fe2O3)‐(Mn3O4)‐3 : 1 in ethyl acetate was also greater than that in xylene and butyl acetate, which was related to their oxidation processes. FT‐IR and GC‐MS characterizations of fresh and used (Fe2O3)‐(Mn3O4)‐3 : 1 catalysts revealed intermediates in the oxidation of volatile organic compounds, and the reaction mechanisms were analyzed: Firstly, VOCs molecules were adsorbed on the catalyst surface, then decomposed into organic intermediates and oxidized to CO2 and H2O finally.

Mn-Ag bimetals supported on plate-like ZSM-5 as efficient and stable catalysts for the catalytic combustion of toluene: Synergistic effects and catalytic mechanisms

Ag-modified MnO2 loaded on plate-like ZSM-5 (PZ5) with different Ag/Mn ratios were synthesized by an in-situ growth method and used as catalysts for toluene combustion, as a probe molecule of volatile organic compounds (VOCs). The results showed that Ag doping greatly enhanced the toluene combustion activity (Mn50Agy/PZ5). Among them, Mn50Ag0.04/PZ5 showed the highest catalytic activity for toluene combustion with 90 % conversion of toluene at 234 °C (T90), and the reaction rate calculated per unit mass of Mn was 1.22×10−7 at 220 °C, which was 2.7 times higher than that of MnO2. In addition, Mn50Ag0.04/PZ5 exhibited excellent long-term stability and water resistance. Various characterizations indicated that the excellent performance of Mn50Ag0.04/PZ5 was attributed to its higher Mn2++Mn3+/Mn4+ ratios, higher reducibility, and more active surface adsorbed oxygen species. Finally, in-situ DRIFTS studies confirmed that Ag doping did not alter the catalytic combustion pathway of toluene over the Mn50Ag0.04/PZ5 catalyst but could accelerate the rate of conversion of toluene to the final products because the transfer of electrons from Ag+ to lattice oxygen persuaded the weaken of the Mn-O bond, and then made it easier for bulk lattice oxygen to migrate towards the Ag-MnO2 interface or catalysts’ surface, thus showing the better catalytic performance for toluene combustion.

Catalytic combustion of toluene over highly dispersed Pt NPs embedded in porous TiO2 via in situ pyrolysis of MOFs

In this work, a series of x wt% Pt@TiO2 (x = 0.18, 0.42, and 0.84) catalysts with highly dispersed Pt nanoparticles (NPs) are synthesized via pyrolysis method using Ti-based metal-organic frameworks (MOFs) as precursors. Physicochemical properties of the catalysts are characterized by a number of analytical techniques. It is shown that all samples possess mesoporous structure with surface area of 59–75.6 m2/g, thus can suppress the aggregation of Pt NPs, and enhance toluene adsorption and diffusion. The 0.84 wt% Pt@TiO2 catalyst exhibits the best catalytic performance for toluene oxidation (T90% =150 °C at space velocity = 20,000 mL/ (g h)), which is attributed to the higher surface area, abundant adsorbed oxygen and Pt0 species, and strong interaction between Pt NPs and TiO2. In addition, the possible reaction mechanism of toluene oxidation is proposed based on in situ DRIFTS technique.

Ammonia and toluene oxidation: Mutual activating effect of copper and cerium on catalytic efficiency

Copper and cerium containing hydrotalcite-like precursors Cux-Cey-Mg-Al were synthesized by mutual co-precipitation followed by calcination at 800 °C. The obtained mixed metal oxides were studied as catalysts for selective ammonia oxidation (NH3-SCO) and toluene combustion. Various techniques, such as temperature-programmed reduction with hydrogen, temperature-programmed desorption of toluene, scanning electron microscopy and reactive frontal chromatography were used to characterize the catalysts. Series 800-Cux-Ce2.5 showed the highest catalytic efficiency in both reactions, allowing complete NH3 and C7H8 conversion below 350 °C and 500 °C, respectively. CeO2 crystallites (12–18 nm), as well as dispersed CuO oxide forms were found in the most active samples. Both phases affect pollutants conversion, however, for ammonia oxidation the occurrence of Cu2+ is essential, while for toluene oxidation, the formation of Ce4+ is sufficient. Over the most active sample (800-Cu5-Ce2.5) the complete conversion in mutual oxidation of NH3 and toluene was achieved below 450 °C.

Promote the efficient co-combustion of toluene & CO in Pt/CeO2 catalyst: Orientally adjusting the oxidized SMSI to optimize acid site and oxygen vacancy

By effectively controlling the strong metal-support interaction (SMSI), the formation of acid sites and oxygen vacancies (Ov) on the Pt/CeO2 catalyst was optimized. The efficient co-combustion of toluene and CO on Pt/CeO2-450 was achieved. In the dual-pollutant system, when the conversion rate was 90 %, the corresponding conversion temperatures of toluene and CO were 165 °C and 173 °C, respectively. With the increase of SMSI, the catalytic activity of Pt/CeO2 showed a trend of first increase and then decrease. This was proportional to the content of weak acid sites, medium acid sites, and Ov generated on their surfaces. Compared with the combustion of a single pollutant, the result displays that toluene and CO had significant competitive adsorption on Pt/CeO2. The inhibition of toluene on CO also showed the same trend as the catalytic activity with the increase of SMSI. Under the double inhibition, Pt/CeO2 exhibited preferential selectivity for toluene combustion. However, the in situ DRIFTS results showed that this competitive adsorption phenomenon did not interfere with the combustion reaction path. The co-combustion of toluene and CO follows independent reaction paths. This work provides valuable insights and ideas for realizing the development of efficient and environmentally friendly catalysts through SMSI regulation.

Facet effect on nanosheet Co3O4 catalysts for toluene oxidation: Decisive role of Co3+ and reaction-induced oxygen vacancy

Co3O4 is recognized as an advantageous material for harmful VOC abatement. In this paper, three types of Co3O4 catalysts exhibiting either nanosheet morphology or nanosheet tissue structure were synthesized and applied in the combustion of toluene. The characterization results highlight the significance of Co3+ species over surface oxygen. Moreover, the oxygen vacancies of the catalyst formed during the reaction process were found to play a more critical role in influencing the catalytic performance than the oxygen vacancies present in the original catalyst. Through this study, we gained valuable insights into the facets, Co3+ species, and oxygen vacancies, which hold promising potential for enhancing the development of Co3O4 catalytic material for practical applications in toluene degradation.

Enabling the activation of lattice oxygen and high distribution of Co3+ on LaCoO3 surface through fluorine incorporation to promote toluene combustion

Limited by the sluggish oxygen mobility, perovskite catalysts are still unsatisfactory in real application. Herein, an effective strategy concerning the activation of surface lattice oxygen in LaCoO3 via fluorine incorporation was proposed to improve its toluene oxidation performance. The constructed LCO-2 F reveals more outstanding catalytic activity than that of bare LCO, and excellent long-term run along with water-resistance. Concretely, the F incorporation results in the reduced electronic density around surface lattice oxygen together with the weakened Co–O bond strength, and thus the enhanced surface lattice oxygen activity. Moreover, the F incorporation promotes the exposure of more electron-deficient Co3+ species accompanying with abundant surface lattice oxygen as well, which contribute to the adsorption and activation of toluene. In situ DRIFTS results indicate that LCO-2 F also possesses superior O2 replenishing capacity for fast degradation regarding the tough intermediate species of benzoate, and thus speeding the catalytic cycle.

Catalytic combustion of toluene performance over MnOx catalysts: Effect of KMnO4 content

MnOx samples were prepared and applied to the catalytic combustion of toluene. The results indicated that the KMnO4 content was important to the catalytic performance. Cat‐0.2 (0.2 g KMnO4) possessed the best catalytic performance, and more than 90% of toluene conversion was 255°C. Moderate amounts of KMnO4 facilitated the generation of mixed crystalline phases and structural defects, which led to the generation of more oxygen vacancies. In addition, the Cat‐0.2 possessed high contents of Oads/(Oads + Olatt) and Mn3+/(Mn3+ + Mn4+), which promoted the emergence‐annihilation cycle of oxygen vacancies and facilitated the reaction process of toluene. The reaction pathway of toluene was investigated via in situ DRIFTS, in which the by‐products included benzyl alcohol, benzaldehyde, benzoate, maleic anhydride, and short‐chain carbonate. Among them, benzoate was the main intermediate in the catalytic oxidation process of toluene.

Constructing surface oxygen defects at CuO–Co3O4 interface to boost toluene oxidation over CuO/Co3O4 catalysts

As a typical heterogeneous catalytic process, the catalytic combustion of toluene over Co3O4-based catalysts is strongly depends on the surface properties of catalysts, especially the concentration of surface oxygen defects. Here, a novel way was proposed to construct chemically bonded CuO–Co3O4 interface by chemical deposition of CuO onto Co3O4 nanoflowers. The interfacial refinement effect between CuO and Co3O4 support disrupted the ordered atomic arrangement and created countless unsaturated coordination sites at CuO–Co3O4 interface, inducing a significant generation of surface oxygen defects. Surface-rich oxygen vacancies enhanced the capacity of 20%CuO/Co3O4–R to adsorb and activate oxygen species. Benefiting from this, 90 % toluene conversion was reached at 228 °C over 20%CuO/Co3O4–R, which was much lower than that over 20%CuO/Co3O4–S prepared by impregnation method and CuO/Co3O4-mix obtained by mechanically mixing way. In-situ DRIFTS analysis revealed that toluene could be directly decomposed into benzaldehyde at the highly defective CuO–Co3O4 interface, leading to toluene oxidation following the path of toluene → benzaldehyde → benzoate → maleic anhydride → water and carbon dioxide over 20%CuO/Co3O4–R, which was significantly different from decomposition mechanism over 20%CuO/Co3O4–S. Additionally, 20%CuO/Co3O4–R displayed terrific recyclability and outstanding stability, showing good application potential.

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.

Mesoporous Silica MCM-41 from Fly Ash as a Support of Bimetallic Cu/Mn Catalysts for Toluene Combustion.

The main outcome of this research was to demonstrate the opportunity to obtain a stable and well-ordered structure of MCM-41 synthesized from fly ash. A series of bimetallic (Cu/Mn) catalysts supported at MCM-41 were prepared via grinding method and investigated in catalytic toluene combustion reaction to show the material's potential application. It was proved, that the Cu/Mn ratio had a crucial effect on the catalytic activity of prepared materials. The best catalytic performance was achieved with sample Cu/Mn(2.5/2.5), for which the temperature of 50% toluene conversion was found to be 300 °C. This value remains in line with the literature reports, for which comparable catalytic activity was attained for 3-fold higher metal loadings. Time-on-stream experiment proved the thermal stability of the investigated catalyst Cu/Mn(2.5/2.5). The obtained results bring a valuable background in the field of fly ash utilization, where fly ash-derived MCM-41 can be considered as efficient and stable support for dispersion of active phase for catalyst preparation.