Catalytic Combustion Of Toluene Research Articles

Synthesis of a Highly Active and Stable Pt/Co3O4 Catalyst and Its Application for the Catalytic Combustion of Toluene

Catalytic combustion has become one of the most economical, feasible and effective tools for the abatement of VOCs. However, it is difficult to prepare supported Pt catalysts possessing both excellent catalytic activity and stability by traditional preparation methods, such as incipient‐wetness impregnation method and nanoparticle loading method. In this work, we prepared Pt/Co3O4 catalyst with high catalytic activity and stability for the catalytic combustion of toluene by galvanic displacement method. As comparing, additional reference samples were prepared using incipient‐wetness impregnation method and nanoparticle loading method, respectively. All of the samples were characterized by XRD, TEM, H2‐TPR, O2‐TPD and XPS techniques. The catalyst prepared by galvanic displacement method exhibited the best catalytic activity with the temperature of 90 % toluene conversion about 150 °C (T90 = 150 °C) and outstanding stability reflected in a continuous 100 h on‐stream toluene combustion lifetime experiment without catalytic activity decline at the GHSV = 60 000 mL g–1 h–1 compared to which prepared by traditional methods. These results are attributed to the excellent oxygen mobility, the high surface chemisorbed oxygen species concentration and the strong interaction between Pt and support Co3O4. Therefore, our work provided a universal strategy for designing high‐efficiency and stable catalyst for the abatement of VOCs at low temperature.

Direct ink writing of porous cordierite honeycomb ceramic

Abstract Herein, we fabricated honeycomb ceramics with different porosities and pore shapes via the layer-by-layer deposition of cordierite (2MgO·2Al2O3·5SiO2) particle ink, obtaining proper rheological properties using a direct-writing technology. No collapses as well as minimal cracking and bending were observed in the internal structure of the samples after calcination. We measured and compared the internal porosity and specific surface area of honeycomb ceramics with the same pore shape but different pore dimensions, as well as the same pore dimension but different pore shapes. The samples were both loaded with an γ-Al2O3 washcoat and Pd-based catalyst using the same method for the catalytic combustion of toluene. The different porosity and pore shape influenced the catalytic efficiency. This study may provide some useful guidelines for fabrication of honeycomb ceramics by direct writing technology, which could be used to remove volatile organic pollutants(VOCs).

Low temperature catalytic combustion of toluene over three-dimensionally ordered La0.8Ce0.2MnO3/cordierite catalysts

Cordierite-supported three-dimensionally ordered macroporous (3DOM) and nanoparticle La0.8Ce0.2MnO3 catalysts were prepared by PMMA-templating and impregnation methods, respectively, to eliminate toluene in low temperature. The catalysts were characterized by BET, SEM, HRTEM, XRD, H2-TPR, NH3-TPD and XPS. The effects of calcination temperature and morphology on the specific surface area, pore volume and size, crystal phase, reduction ability, surface acid distribution and surface property were investigated, and then toluene removal efficiency and apparent active energy were also studied. The results show that the structure and morphology of the active component have a great influence on the specific surface area of the catalyst. At the same calcination temperature of 600 °C, the specific surface area of 3DOM La0.8Ce0.2MnO3/cordierite is 35.3 m2· g−1, which is much larger than that of the nanoparticle La0.8Ce0.2MnO3/cordierite (11.9 m2· g−1). Calcination temperature also can affect the properties of the catalyst and catalytic combustion performance. With different calcination temperatures of 600, 700 and 800 °C, the 3DOM sample calcinated at 600 °C (T50 = 147 °C, T90 = 217 °C, and Ea = 27.01 kJ·mol−1; SV = 6000 h−1) showed the best performances in reduction property, specific surface area, adsorption oxygen concentration, and catalytic combustion performance.

Revealing the unexpected promotion effect of EuOx on Pt/CeO2 catalysts for catalytic combustion of toluene

Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction, and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed. The characterization results reveal that the presence of EuOx significantly enhances the redox property, lattice O concentration, and Ce3+ ratio of the Pt/CeO2 material, which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene. Among all catalysts, a sample with an Eu content of 2.5 at.% (Pt/EC-2.5) possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 °C under a relatively high GHSV of 50000 h−1. The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS, which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.

Copper modified manganese oxide with tunnel structure as efficient catalyst for low-temperature catalytic combustion of toluene

Copper-modified manganese oxide catalysts with tunnel, layer, and transitional structure were successfully prepared by a one-step hydrothermal method and investigated for the catalytic oxidation of toluene. The catalysts were characterized by XRD, SEM, TEM, BET, H2-TPR, XPS and ICP-AES techniques. The tunnel-structured catalyst exhibited the best activity among the three Cu-Mn oxide catalysts and excellent water resistance. Abundant surface oxygen species, good low temperature reducibility, low average oxidation state of manganese, and high surface area lead to remarkable catalytic performance of this catalyst. The toluene catalytic combustion over these catalysts was found to follow the Mars-van-Krevelen mechanism and the unique copper states found in the tunnel-structured catalyst play a key role in promoting the cyclic redox process.

Effect of γ-ray irradiation on the catalytic activity of perovskite-type oxides

Perovskite-type oxides, due to their structural stability and special physical and chemical properties, have become important topics in the field of catalytic materials research. This article focuses on the effect of γ-ray irradiation on the catalytic activity of LaCoO3 and BaPbO3. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) were used to analyze the physical and chemical properties of LaCoO3 and BaPbO3. Finally, H2O2 catalytic decomposition and toluene catalytic combustion experiments were performed to verify the activity of LaCoO3 and BaPbO3 before and after irradiation. The results show that after γ-ray irradiation, the activity of LaCoO3 and BaPbO3 on catalytic hydrogen peroxide decomposition was reduced, and the activity of catalytic toluene combustion was enhanced.

Catalytic combustion of VOC on sandwich-structured Pt@ZSM-5 nanosheets prepared by controllable intercalation.

A sandwich-structured Pt@ZSM-5 nanosheets (Pt@PZN-2) was fabricated by controllable intercalating Pt nanoparticles between ZSM-5 single-layer sheets via electrostatic adsorption with ammonium ions in diquaternary ammonium surfactant, and the following calcinations. Pt clusters (ca. 4.3 nm) confined between nanosheet layers (thickness of ca. 2.9 nm) exhibits better dispersion and higher thermal stability even after high-temperature treatment, while the Pt clusters also served as pillars which well protected the inter-layers mesopores. Catalytic combustion of toluene (a model compound of large molecules VOCs) shows catalytic activity of Pt@PZN-2 is significant higher than that of Pt-loaded nanosheet ZSM-5 zeolite prepared by conventional impregnation (Pt/ZN-2). For example, the temperature at 98% toluene conversion of Pt@PZN-2 is only 176 °C which is 24 °C and 34 °C lower than that of Pt/ZN-2 and bulky ZSM-5 supported Pt by impregnation (Pt/CZ-500), respectively. Meanwhile, Pt@PZN-2 also gives 100% toluene conversion for more than 360 h at 230 °C with a higher metal stability. The good performance of Pt@PZN-2 was attributed to the high accessibility and enhanced diffusion of the bulky reactant to active site confined in the stable inter-layer mesopores resulting from the pillar of Pt nanoparticles.

Synthesis of CeaMnOx hollow microsphere with hierarchical structure and its excellent catalytic performance for toluene combustion

A series of CeaMnOx hollow microsphere like arbutus with hierarchical structure are prepared by redox co-precipitation method and applied for catalytic toluene combustion. The Ce0.03MnOx shows a better catalytic performance for toluene combustion with high stability, water resistance, even under the condition of 5vol.% H2O. The results of XRF, XRD, Raman, N2 adsorption-desorption, SEM, TEM prove that the doping of Ce can affect the structure of CeaMnOx such as much smaller particle size and higher specific surface area. The characterizations of H2-TPR, O2-TPD, XPS certify the strong interaction between Ce and Mn oxides that leads to more surface adsorbed oxygen and Mn4+ species due to oxidation reduction cycle of Mn3+ + Ce4+ ↔ Mn4+ + Ce3+ after Ce addition. Meanwhile, the Toluene-TPD in different conditions confirms the introduction of water promoted the catalytic oxidation of toluene. In situ DRIFTS is used to investigate the reaction process of toluene oxidation. And the results reveal that the Ce0.03MnOx catalyst has much stronger ability to adsorb and activate toluene compared with MnOx catalyst, especially under with H2O. That may be the main reason that the Ce0.03MnOx catalyst exhibits the special catalytic activity for toluene combustion.

Co基催化剂上甲苯催化燃烧的研究

Co基催化剂上甲苯催化燃烧的研究

Porous hollow CoInOx nanocubes as a highly efficient catalyst for the catalytic combustion of toluene.

Porous hollow HC-CoInOx nanocubes were synthesized via a SiO2 template strategy involving a cobalt-based metal-organic framework derived from a Prussian Blue analogue. As a heterogeneous catalytic material for the catalytic combustion of toluene, the hollow HC-CoInOx nanocubes displayed superior catalytic performance (T90 = 178 °C) and greatly reduced the activation energy for toluene oxidation due to their large surface area, the formation of surface dangling bands and oxygen vacancies, and increased number of weak acid sites. In comparison, the C-CoInOx sample (without the introduction of a SiO2 template) required a higher reaction temperature to achieve the same conversion of toluene (T90 = 345 °C). Especially, the insertion and coating of SiO2 in CoIn-PBA nanocubes greatly improves their thermal stability, and the nanocubic shape of the porous hollow HC-CoInOx sample can remain intact after roasting at 450 °C, while the nanocubic shape of the C-CoInOx sample without the introduction of SiO2 is partially damaged and suffers from serious aggregation under the same firing conditions. Simultaneously, the porous hollow HC-CoInOx nanocubes also exhibited excellent cycling and thermal stability for the catalytic combustion of toluene to CO2 and H2O.

Catalytic Combustion of Toluene over Cu–Mn Mixed Oxide Catalyst

Catalytic Combustion of Toluene over Cu–Mn Mixed Oxide Catalyst

Enhanced catalytic performances of in situ-assembled LaMnO3/δ-MnO2 hetero-structures for toluene combustion

It is of fundamental significance to rationally design the potent toluene-oxidation nanocatalysts for alleviating the release of toluene, one hazardous volatile organic compound, from industrial processes, oil products and fitments materials. The manganese oxide has been developed as the extremely robust combustion materials for a wide spectra of application involving methane combustion, CO oxidation and so forth, but still has been haunted with the poor behavior for toluene combustion. Herein, we successfully demonstrate a one-step scenario wherein the well-structured LaMnO3 perovskites are in situ assembled over δ-MnO2 for the first time. Various characterizations unravel that the LaMnO3 perovskites interact with δ-MnO2 to result in good catalytic toluene combustion behavior at the Mn/La ratio of 15. Boosted active phase-carrier interplays, improved redox abilities, and tuned Mn4+/Mn3+ couples ultimately result in the decent toluene combustion property with the full toluene oxidation at 275 °C and T90 at 258 °C. The nanostructured scalable MnO2-based materials are promising catalyts that can be extended to degrade alkane, alcohols, aldehydes and benzene series.

Effect of CeO2 morphologies on toluene catalytic combustion

Catalytic combustion is an efficient and economic technology to eliminate toluene, and CeO2 shows very good performance in this kind of reactions. In this work, three kinds of CeO2 catalysts with different morphologies (rod, hollow sphere and cube) have been prepared, and there performances for toluene catalytic combustion were compared. It is found that CeO2-HS shows the best catalytic activities for toluene degradation. Toluene conversion could get 90% at 207 °C. That’s because CeO2-HS catalyst have largest surface area and most oxygen vacancies, which are vital for toluene catalytic oxidation. CeO2-HS also shows very good catalyst stability, reusability and excellent tolerance to water.

Effect of coke formation on catalytic activity tests for catalytic combustion of toluene: the difficulty of measuring TOF and T98 accurately

Catalytic combustion is considered as one of the most efficient routes for removing volatile organic compounds. In recent years, the catalytic activities of catalysts have usually been evaluated by the values of TOF and T98. It is difficult, however, to measure the values accurately because the influencing factors are numerous and easy to be overlooked. In this work, the influence of the catalytic test procedure on TOF and T98 values was investigated. Supported Pd or Pt catalysts were prepared via the incipient wetness impregnation method. The catalytic activities of the same catalyst were very different when evaluated in different catalytic test procedures. Indeed, the catalytic test procedures affected the TOF and T98 values remarkably. It was found that the different coking behavior in different catalytic test procedures is the major cause. The influences on coke formation in toluene combustion – such as reaction temperature, reaction time, and catalyst type – were investigated.

The role of graphene coating on cordierite-supported Pd monolithic catalysts for low-temperature combustion of toluene

In the present work, a Pd/graphene/cordierite (Pd/Gr/Cor) composite was prepared as a monolithic catalyst for low-temperature combustion of toluene. We mainly focused on understanding the role of graphene coating through investigation of catalytic performance and adsorption behavior of the composite. Compared with the traditional Pd/Cor catalyst without graphene coating, Pd/Gr/Cor catalyst delivered much higher activity and stability for toluene catalytic combustion in both dry and moist conditions. Transmission electron microscopy (TEM) and hydrophobic characterizations indicated that graphene coating can considerably improve the dispersity of Pd nanoparticles and enhance the hydrophobicity of the cordierite support. The adsorption behavior of the above two catalysts, including adsorption isothermal, adsorption kinetics, and adsorption thermodynamics were carefully investigated. The simulation results indicated that a large amount of toluene was adsorbed on graphene surface through relatively weak interaction, whereas only a relatively small amount of toluene was adsorbed on Pd surface with strong affinity. The adsorption thermal calculation indicated that the adsorption of toluene on graphene was a process with reduced entropy, indicating highly-ordered assembly of toluene molecular on graphene. It is the significant concentration and affinity gap between graphene and Pd that ensures a simultaneously and rapid transfer of toluene during the reaction process.

Promoting Effects of Ni for Toluene Catalytic Combustion Over CoNi/TiO2 Oxide Catalysts

AbstractThe supported CoNi/TiO2composite oxide catalysts were prepared by impregnation method. The physical and chemical properties of the prepared catalysts were studied by XRD, XPS and H2-TPR. The results show that the Co3O4, NiO and NiCo2O4species are formed in the CoNi/TiO2composite oxide catalysts. The interaction between the Co and Ni species can effectively enhance the properties of the CoNi/TiO2oxide catalysts. The introduction of Ni species can effectively enhance the surface hydroxyl oxygen species and adsorbed oxygen species content, and the Co3+species content can be enhanced on the surface of the prepared CoNi/TiO2composite oxide catalysts. The low temperature reducibility and toluene catalytic combustion activity of the CoNi/TiO2composite oxide catalysts can be improved by the Ni species. The toluene catalytic combustion activity of CoNi/TiO2composite catalysts can be obviously affected by the Co/Ni molar ratio. The CoNi/TiO2composite oxide catalyst, which has a Co/Ni molar ratio of 1.0, has the best toluene catalytic combustion activity and wide scope of the concentration of toluene. The toluene catalytic combustion conversion can exceed 99 % at 340 °C. That is to say, the toluene concentration in air can be decreased to 80 ppm from 8000 ppm.

Enhancing performance of Co/CeO2 catalyst by Sr doping for catalytic combustion of toluene

Cobalt-based catalyst supported on strontium-doped ceria was prepared by impregnation method. The physical and chemical properties were investigated by various technologies and the catalytic combustion of toluene was evaluated at fixed-bed. The possible reaction process of toluene oxidation on Co/Sr-CeO2 was also investigated. The results showed that Sr doping enlarges the specific surface area of CeO2, accompanied by strong interaction between Co and Ce and high dispersion of Co oxides. Sr doping increases the lattice defects of CeO2, which creates oxygen vacancies and enhances the oxygen mobility in Co/Sr-CeO2. Sr doping also changes the electronic characteristics of Co on CeO2 and improves the redox properties of Co/CeO2. The introduction of Sr to Co/CeO2 catalyst may improve the catalytic performance in total oxidation of toluene. In addition, Co/Sr-CeO2 catalyst shows lower light-off temperature than Co/CeO2 catalyst and has good thermal stability in the long-term testing. Toluene is degraded into phenyl and methyl groups at 235 °C for Co/Sr-CeO2 and 255 °C for Co/CeO2 because of the cleavage of C–C between the benzene ring and methyl, and it is completely oxidized into CO2 and H2O at 330 °C for Co/Sr-CeO2 and 380 °C for Co/CeO2.

Effects of Ce in the catalytic combustion of toluene on CuxCe1-xFe2O4

CuxCe1-xFe2O4 (x = 0, 0.2, 0.5, 0.8, 1) catalysts were synthesized by a sol-gel auto-combustion method, and the catalysts were characterized by differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), H2-temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The activity of CuxCe1-xFe2O4 was evaluated in the catalytic combustion of toluene in a fixed-bed reactor. The results indicated that the Cu0.8Ce0.2Fe2O4 expressed the highest catalytic combustion activity of toluene, the ignition temperature (T50) and the complete conversion temperature (T90) were 180 °C and 215 °C, respectively. The Ce doping of CuFe2O4 could increase the oxygen storage capacity and improve the catalytic combustion activity of toluene. The CuFe2O4 spinel crystal structure gradually disappeared with the increase in Ce doping; at the same time, the catalytic combustion activity of the samples was obviously affected.

Morphology-controlled synthesis of 3D, mesoporous, rosette-like CeCoOx catalysts by pyrolysis of Ce[Co(CN)6] and application for the catalytic combustion of toluene.

We synthesized one-dimensional (1D) nanoparticles, 2D hexagonal nanosheets and 3D rosettes of Ce[Co(CN)6] by a hydrothermal process at different temperatures, and CeCoOx catalysts with similar shapes were obtained by the pyrolysis of Ce[Co(CN)6]. T90 of 1D nanoparticles, 2D hexagonal nanosheets and 3D rosette-like CeCoOx catalysts was 306, 275 and 168 °C, respectively. The 3D ordered mesoporous rosettes of CeCoOx had superior catalytic activity for toluene combustion, superior thermal stability and moisture resistance, and curves for three consecutive catalytic runs showed overlapping due to more oxygen vacancies, larger pore sizes, more surface Ce3+ species, more surface Co3+ species, and chemically adsorbed oxygen on the surface.

Preparation of 3D micro/nanostructured CeO2: Influence of organic/inorganic acids

CeO2 is an important porous material with a wide range of applications in the abatement of volatile organic compounds (VOCs). In this paper, we prepared a series of novel three-dimensional (3D) micro/nanostructured CeO2 materials via a solvothermal method. Organic acid-assisted synthesis and inorganic acid post-treatment were used to adjust the CeO2 microstructures. The size of the 3D micro/nanostructures could be controlled in the range from 180nm to 1.5μm and the surface morphology changed from rough to smooth with the use of different organic acids. The CeO2 synthesized with acetic acid featured a hierarchical porosity and showed good performance for toluene catalytic combustion: a T50 of 187°C and a T90 of 195°C. Moreover, the crystallite size, textural properties, and surface chemical states could be tuned by inorganic acid modification. After treatment with HNO3, the modified CeO2 materials exhibited improved catalytic activity, with a T50 of ∼175°C and a T90 of ∼187°C. We concluded that the toluene combustion activity is related to the porosity and the amount of surface active oxygen of the CeO2. Both these features can be tuned by the co-work of organic and inorganic acids.