Catalytic Combustion Of Toluene Research Articles

Structured cobalt–manganese oxides on SiC nano-whisker modified SiC foams for catalytic combustion of toluene

This work presents a two-step method for preparing structured Cobalt-Manganese Oxides nano-sheet (CMO) on SiC nano-whisker (SNW) modified SiC foam support (i.e. CMO@SNW@SiC) and its application to catalytic combustion of toluene. Firstly, SiC nano-whiskers were synthesized on the surface of SiC foam via carbothermal reduction to increase the specific surface area of the resulting structured support (SNW@SiC). Then, CMO were grown on SNW@SiC by hydrothermal synthesis. SNW@SiC provide more surface area, and the nano-sized SiO2/SiCxOy layer on the surface of the SNW promotes the redox reaction of the reactants on the surface, thereby ensuring the directional growth of CMO on SNW@SiC. Compared to the bare SiC foam, CMO loading was increased 67.5% on SNW@SiC. Analysis methods such as H2-TPR, O2-TPD and XPS prove that the redox ability of the CMO on SNW is similar to that of the powder CMO. Toluene catalytic combustion was used as a probe reaction to evaluate catalytic activity. The results show that the CMO@SNW@SiC catalyst could lower the light-off temperature compared to the CMO supported on SiC foam catalyst, which was equivalent to the bulk catalyst (CMO-24h). At the same time, in comparison with the bulk CMO catalyst, the CMO@SNW@SiC catalyst possessed a higher geometric external surface area, which promoted complete conversion of toluene at lower temperatures. In addition, the stability test shows that the CMO@SNW@SiC catalyst also had very good thermal stability and hydrothermal stability as well. The work provided not only the highly performed catalytic oxidation catalyst, but also presented a generic strategy for improving the design of structured catalysts.

Synthesis of Rod-Like Co3O4 Catalyst Derived from Co-MOFs with Rich Active Sites for Catalytic Combustion of Toluene

Synthesis of Rod-Like Co3O4 Catalyst Derived from Co-MOFs with Rich Active Sites for Catalytic Combustion of Toluene

Enhancement of catalytic combustion of toluene over CuMnOx hollow spheres prepared by oxidation method

Catalytic oxidation is considered as one of the most potential technologies for complete removal of VOCs. It is generally accepted that the development of catalyst with high and stable activity at low temperature is the key for such a catalytic strategy. The CuMnO x catalyst with a hollow spherical structure (CuMnO x -HS) was successfully prepared by an oxidation strategy and applied to toluene removal. Combined with the results of XRD, SEM, TEM, HRTEM, BET, H 2 -TPR, XPS and O 2 -TPD, the enhanced synergistic effect between Mn and Cu originating from the special oxidation method resulted in the large specific surface area, enhanced reducibility, and oxygen mobility as well as abundant adsorbed oxygen species of CuMnO x -HS, which was responsible for its superior catalytic performance. CuMnO x -HS could achieve a toluene conversion of 90% at 212 °C. Furthermore, CuMnO x -HS showed a stable removal efficiency and excellent water resistance, suggesting a great potential in practical application for the complete removal of toluene. CuMnO x catalyst with a hollow spherical morphology (CuMnO x -HS) was successively synthesized by in-situ oxidation of Cu 2 O nanospheres. The CuMnOx-HS catalyst achieves a toluene conversion of 100% at 220 °C, and shows super-stable removal efficiency and water resistance, indicating a great potential in practical application for the total oxidation of toluene. • CuMnO x hollow spheres (CuMnO x -HS) were prepared by in-situ oxidation of Cu 2 O. • The stepwise oxidation of Cu 2 O spheres facilitated the Cu 2+ -O 2− -Mn 4+ entities. • CuMnO x -HS showed a super-stable removal efficiency and good resistance to water. • The enhanced reducibility and oxygen mobility were responsible for the superior activity of CuMnO x -HS.

Studies of sulfur poisoning process via ammonium sulfate on MnO2/γ-Al2O3 catalyst for catalytic combustion of toluene

MnO2/γ-Al2O3 catalysts were prepared and then quantitatively sulfur-poisoned by the pre-treatment of (NH4)2SO4 as a simulated sulfur-poisoning species. Catalytic combustion of toluene on fresh and poisoned MnO2/γ-Al2O3 catalysts was comparatively investigated. The characterization results from XRD, FT-IR, HRTEM, N2 adsorption/desorption, XPS, H2-TPR and NH3-TPD confirmed that the structure and natures of MnO2/γ-Al2O3 was stable when (NH4)2SO4 was used as the poisoning species. However, catalytic activity of the poisoned catalysts significantly decreased and quantitatively depended on the amount of (NH4)2SO4. The adsorption and occupation of the sulfur species from the decomposition of (NH4)2SO4 on active sites and the formation of inactive sulfate species via further oxidation of adsorbed sulfur species were responsible for the declined activity. This work exemplified a promising strategy for quantitatively and easily evaluating the sulfur-poisoning deactivation of catalysts for catalytic combustion of VOCs.

Efficient catalytic combustion of toluene at low temperature by tailoring surficial Pt0 and interfacial Pt-Al(OH)x species

SummaryExploring highly efficient and low-cost supported Pt catalysts is attractive for the application of volatile organic compounds (VOCs) combustion. Herein, efficient catalytic combustion of toluene at low temperature over Pt/γ-Al2O3 catalysts has been demonstrated by tailoring active Pt species spatially. Pt/γ-Al2O3 catalyst with low Pt-content (0.26 wt%) containing both interfacial Pt-Al(OH)x and surficial metallic Pt (Pt0) species exhibited super activity and water-resistant stability for toluene oxidation. The strong metal-support interaction located at the Al-OH-Pt interfaces elongated the Pt-O bond and contributed to the oxidation of toluene. Meanwhile, the OH group at the Al-OH-Pt interfaces had the strongest adsorption and activation capability for toluene and the derived intermediate species were subsequently oxidized by oxygen species activated by surficial Pt0 to yield carbon dioxide and water. This work initiated an inspiring sight to the design of active Pt species for the VOCs combustion.

Study on the Performance of Copper‐Manganese Composite Oxide Catalysts for Toluene

AbstractCopper‐manganese (CuMn) composite oxide catalysts were prepared for the catalytic combustion of a common volatile organic compound, namely toluene. The structural properties of the catalysts were analysed by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller (BET) theory, X‐ray photoelectron spectroscopy (XPS) and hydrogen temperature‐programmed reduction (H2‐TPR). The catalytic stability was examined after 100 h. It was found that Cu1Mn1 exhibited the highest catalytic ability when the molar ratio of Cu : Mn was 1 : 1. The removal of toluene reached 90 % at a temperature below 229 °C. It was speculated that the Cu1.5Mn1.5O4 spinel structure and CuO were formed in the catalyst. The catalyst surface area was not the main factor affecting the catalytic activity. The catalysts displayed good stability and maintained high catalytic activity for a long time. Notably, fresh catalysts contained high amounts of high‐valent Mn4+ and Cu2+ cations, which played important roles in the catalytic combustion of toluene. The cations initiated the redox process and led to the conversion of toluene to CO2 and H2O. The reduced lattice oxygen supplied from air was transformed into surface oxygen on the catalyst. The catalytic combustion of toluene in the presence of CuMn composite oxide catalysts followed the Mars‐van Krevelen mechanism.

In situ confined encapsulation strategy for construction of Co3O4@SiO2 catalyst for the efficient elimination of toluene

Abstract In this study, a novel in situ confined encapsulation strategy for construction of Co3O4@SiO2 catalyst by the vacuum self-assembly method was developed. The ordered mesoporous silica with different pore diameters was treated as templates to prepare order mesoporous Co-MOFs@SiO2, and the Co-MOF were anchored and embedded in ordered mesoporous channels of mesoporous SiO2 by the vacuum in-situ self-assembly process. After calcination, two types order mesoporous Co3O4@SiO2 catalysts with different pore diameters (OM-Co3O4@KIT-6 and OM-Co3O4@SBA-15) were obtained for catalytic combustion of toluene. It is discovered that the highly dispersed Co3O4 nanoparticles were limited in the pores of ordered mesoporous silica. The test results for the toluene oxidation reaction confirmed that OM-Co3O4@SBA-15 with 16 nm pore diameter has excellent toluene catalytic oxidation activity and good thermal stability, which are mainly attributed to the content and dispersion of Co3+ species, the effective anchoring of Co-MOF in the pores, more adsorbed oxygen species and strong acid sites.

Catalytic Combustion of Toluene over Highly Dispersed Cu-CeOx Derived from Cu-Ce-MOF by EDTA Grafting Method

In this work, Cu-CeOx-MOF catalysts with well-dispersed Cu in different contents were synthesized via the ethylenediaminetetraacetic acid (EDTA) grafting method. EDTA was grafted in Ce-MOF-808 to anchor Cu and then the metal-organic frameworks (MOFs) were utilized as sacrificial template to form highly performed Cu-CeOx-MOF for toluene catalytic combustion. In this series of samples, Cu-CeOx-MOF-0.2 had a higher ratio of Oα/(Oα+Oβ), more oxygen vacancies and performed better low-temperature reducibility. Cu-CeOx-MOF-0.2 showed outstanding catalytic activity and stability. The T90 (temperature when toluene conversion achieved 90%) of Cu-CeOx-MOF-0.2 was 226 °C at 60,000 mL/(gcat∙h). In situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTS) results revealed that the opening of aromatic ring and the deep oxidation of carboxylate were key steps for toluene catalytic combustion over Cu-CeOx-MOF-0.2.

Hierarchically porous silica supported ceria and platinum nanoparticles for catalytic combustion of toluene

The hierarchically porous silica (NKM-5) was synthesized by the polyelectrolyte-surfactant mesomorphous complex templating method, and the NKM-5 was used as the carrier to load different amounts of ceria to prepare xCe/NKM-5 samples (x represents the CeO2 loading amount) by the impregnation method, and then supported Pt to prepare Pt/xCe/NKM-5 catalyst for toluene catalytic combustion. NKM-5 sample has excellent specific surface area and pore structure, with the increase of CeO2 loading amount, the specific surface area and pore volume of xCe/NKM-5 sample decreased gradually. As the CeO2 loading amount increased, XRD and TEM characterization showed that the Pt dispersion of Pt/xCe/NKM-5 catalyst increased; XPS results showed that the proportion of Pt0 decreased and the proportion of Ce3+ increased; H2-TPR characterization showed that the reducibility increased; and the interaction between Pt and CeO2 increased gradually. The toluene catalytic combustion activity of Pt/xCe/NKM-5 catalyst first increased and then decreased with the increase of CeO2 loading amount. Pt/30Ce/NKM-5 catalyst has the most excellent catalytic activity with 50% toluene conversion at 174 °C and 90% conversion at 195 °C, which is the result of the synergy effect of the hierarchical pore structure of the support and the metal-support interaction between Pt and CeO2.

Effect of preparation methods on the structure and catalytic performance of CeO2 for toluene combustion

CeO2 aerogel (CeO2-A), nanorod (CeO2-R) and nanoflake (CeO2-F) were prepared via sol-gel, hydrothermal and coprecipitation methods, respectively. The effect of morphology and structure of CeO2 on the catalytic performance in toluene combustion reaction was investigated based on structure analysis provided by characterization. The results revealed that the activity of both CeO2-R and CeO2-F was inferior to that of CeO2-A, due to smaller specific surface area and only exposure of (111) crystal plane dominantly detected from their TEM images for CeO2-R and CeO2-F. While, the CeO2-A had a larger specific surface area and more exposed (111) and (100) facet, which contributed to exposure and formation of more oxygen vacancies and further to the adsorption of more gaseous oxygen. In addition, highly mobile lattice oxygen was another critical factor for influencing the catalytic performance of CeO2, which was beneficial to the redox cycle of Ce3+/Ce4+ and could further accelerate the toluene combustion. As a result, the CeO2-A catalyst exhibited the superior performance in toluene catalytic combustion with t50 of 223°C and t90 of 239°C, respectively, owing to the larger specific surface area, higher exposure of reactive crystal plane and stronger mobility of lattice oxygen.

Ultra-Low Temperature Catalytic Combustion of Toluene in Wood Micro-Channel Reactor with Enhanced Oxygen Activation Via in Situ Growth Nano-Thick Graphited Carbon Coated Pd Catalyst

Ultra-Low Temperature Catalytic Combustion of Toluene in Wood Micro-Channel Reactor with Enhanced Oxygen Activation Via in Situ Growth Nano-Thick Graphited Carbon Coated Pd Catalyst

Study on anti-sulfur dioxide poisoning of palladium-based catalyst for toluene catalytic combustion

The sulfur-containing volatile organic compounds (VOCs) in the storage tank VOCs will produce SOX during the catalytic combustion process, SOX can easily react with Pd species in palladium-based catalysts to form stable sulfates (PdSO3 and PdSO4), resulting in permanently deactivating the palladium-based catalysts. In this paper, the Pt/γ-Al2O3, Pd/γ-Al2O3, Pd–Pt/γ-Al2O3 and Pd–Pt/MgO/γ-Al2O3 mesoporous catalysts were prepared using an incipient wetness impregnation method. The anti-sulfur dioxide poisoning performance of the catalysts and the mechanism of anti-sulfur dioxide poisoning of Pd–Pt/γ-Al2O3 and Pd–Pt/MgO/γ-Al2O3 catalysts were investigated. The SOX competitive adsorbent is highly dispersed on the catalyst surface, which makes the formed sulfate highly dispersed on the catalyst surface, thereby reducing the thermal decomposition temperature of the sulfate. The results show that the Pd species in Pd/γ-Al2O3 catalyst can easily react with SOX to form stable palladium sulfate species, causing permanent deactivation of the catalyst. The electronic modulation effect between Pd and Pt can reduce the adsorption performance of Pd–Pt active components on sulfur dioxide, and also can prevent the reaction of Pd species with SOX. The added MgO can form MgAl2O4 spinel with the γ-Al2O3 support, and the MgAl2O4 spinel can compete with Pd–Pt active components for SOX adsorption, further protecting Pd–Pt active components from SOX. After catalyst regeneration, the sulfur content of Pd–Pt/MgO/γ-Al2O3 catalyst was greatly reduced, and the regenerated catalyst maintained the catalytic performance of pre-reaction catalyst.

Effect of calcination process on performance of 3DOM CeMnO3 catalysts

A series of 3DOM CeMnO3 perovskite catalysts were prepared by poly(methyl methacrylate) hard-templating-excessive impregnation method at calcination temperature of x °C (x = 600, 700, 800) and the heating rate of y °C/min (y = 1, 2, 5, 10). The samples were characterized by Brunauer-Emmett‐Teller method, scanning electron microscopy, transmission electron microscopy, H2‐temperature programmed reduction, X‐ray photoelectron spectroscopy, X‐ray diffraction, moreover, the effect of the calcination process on the catalytic activity of the samples were discussed by the catalytic combustion of toluene. The results show that the 3DOM CeMnO3 catalysts calcined at 600 °C promote the formation of a perovskite structure, inhibit the reduction of the Mn4+ species in the catalyst with high temperature. The catalyst expresses the complete macroporous structure, large specific surface area (38.8 m2/g), higher adsorption oxygen concentration and Mn4+ substance concentration, with a low T90%=172 °C. By preparing the catalysts at different calcination heating rates, it can be concluded that the catalyst possesses a high concentration of adsorbed oxygen and a low reduction temperature and a large specific surface area (40.42 m2/g) greatly promotes adsorption stage catalytic oxidation reaction and catalytic combustion of toluene at low temperature under the heating rate of 5 °C/min. When the heating rate is 1 °C/min, the catalyst has a complete macroporous structure (>250 nm), which is beneficial to the exchange of macromolecular substances during the catalytic reaction and the catalyst has a high concentration of lattice oxygen suitable for the catalysis of toluene in high temperature flue gas combustion.

Roles of Oxygen Vacancies in the Bulk and Surface of CeO2 for Toluene Catalytic Combustion.

Catalytic combustion technology is one of the effective methods to remove VOCs such as toluene from industrial emissions. The decomposition of an aromatic ring via catalyst oxygen vacancies is usually the rate-determining step of toluene oxidation into CO2. Series of CeO2 probe models were synthesized with different ratios of surface-to-bulk oxygen vacancies. Besides the devotion of the surface vacancies, a part of the bulk vacancies promotes the redox property of CeO2 in toluene catalytic combustion: surface vacancies tend to adsorb and activate gaseous O2 to form adsorbed oxygen species, whereas bulk vacancies improve the mobility and activity of lattice oxygen species via their transmission effect. Adsorbed oxygen mainly participates in the chemical adsorption and partial oxidation of toluene (mostly to phenolate). With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improves the oxidation of toluene to CO2.

Controllable construction of Ce‐Mn‐Ox with tunable oxygen vacancies and active species for toluene catalytic combustion

A series of Ce‐Mn‐Ox catalysts synthesized under different hydrothermal conditions were evaluated by catalytic removal of toluene. The results of characterization showed that the contents of oxygen vacancies and active species in catalysts were crucial for the catalytic oxidation process. The concentration of Ce3+, Mn3+, and adsorbed oxygen associated with structural defects in Ce‐Mn‐Ox catalysts could be controlled by hydrothermal conditions, which were considered to promote redox capacity and improve catalytic oxidation performance. In addition, suitable synthetic conditions could increase the SBET and Vp of catalysts. Among the prepared catalysts, CM‐100 showed the best catalytic performance due to the generation of more defective oxygen and active species (Ce3+, Mn3+, and surface‐adsorbed oxygen). In addition, the CM‐100 catalyst showed satisfactory water resistance and stability.

Rationally Designed Synthesis of Metal–Organic Framework-Derived Cobalt Oxide with Abundant Surface Active Sites for Efficient Catalytic Oxidation Performance

In this paper, Co3O4 was synthesized using pyrolysis of Co-L3, which was prepared by a solvothermal method at different temperatures using a naphthalimide derivative (L3) and cobaltous acetate. The L3 ligands were synthesized using a precursor of naphthalene-1,4,5,8-tetracarboxylic acid and p-aminobenzoic acid. Co-L3-120, Co-L3-160, and Co-L3-200 displayed respectively a one-dimensional (1D) rod structure, a two-dimensional sheet structure, and a 1D spindle structure due to the different structure units. After pyrolysis, the Co3O4 catalysts maintained the same morphologies of the corresponding Co-L3, which was made up of granulum. The Co3O4-160 catalyst presented superior catalytic performance for catalytic combustion of toluene due to the higher redox properties, abundant surface active sites and active oxygen species, higher oxygen vacancies, and higher surface acidities. Further, Co3O4-160 had excellent repetitiveness in three cycling tests and outstanding stability of thermal and moisture resistance.

Platinum Nanoparticles Supported on Hierarchically Porous Aluminosilicate Nanospheres for Low-Temperature Catalytic Combustion of Volatile Organic Compounds

The hierarchically porous silica (NKM-5) and aluminosilicate (Al-NKM-5) supported platinum nanoparticles catalysts were prepared and investigated for the catalytic combustion of toluene and ethanol...

Effect of Na+ on catalytic performance of CoCe/ZSM-5 catalysts for oxidation of toluene

A CoCe/ZSM-5 catalyst was prepared by ultrasonic-assisted impregnation for the catalytic combustion of toluene. To study the effect of Na+ on catalytic performance of CoCe/ZSM-5 catalysts, a series of different Si/Al ZSM-5 zeolites and catalysts doped with Na were synthesized. The experimental results show that 0.71 wt% Na+ can inhibit active growth, generate more active small crystal grains, and promote improvement of the catalytic activity by the grain boundary segregation block mechanism, and the catalyst with 0.71 wt% of Na shows toluene conversion of 90 vol% at 250 °C. Over 0.71 wt% of Na+ content will neutralize the acid centre of the catalyst, lowering the specific surface area of the catalyst and resulting in a gradual decrease in the catalytic activity.

Layered δ-MnO2 as an active catalyst for toluene catalytic combustion

Layered δ-MnO2 was successfully synthesized by redox reaction precipitation between KMnO4 and n-butanol. Then, the as-synthesized layered δ-MnO2 was used as catalyst for toluene catalytic combustion and showed excellent catalytic performance. The T10 and T90 (the temperatures corresponded to the toluene conversion of 10 % and 90 %) were just 160 °C and 199 °C, respectively (1000 ppm toluene, GHSV = 60,000 mL/(g h, 20 vol.%O2/N2). In addition, the layered δ-MnO2 showed well catalytic stability and humid resistance. The as-prepared catalysts were characterized by XRD, N2 sorption, SEM, TEM, XPS, H2-TPR, O2-TPD and so on. Compared with the referenced ε-MnO2 and γ-MnO2, the higher catalytic activity of layered δ-MnO2 was ascribed to its higher specific surface area, stronger low-temperature reducibility and richer oxygen vacancy. Finally, the toluene catalytic oxidation mechanism over δ-MnO2 was also proposed based on the results of in-situ DRIFTs. And the key successively intermediate species for toluene oxidation over δ-MnO2 were benzyl alcohol, benzoic acid, maleic anhydride and acetate.

Structured hierarchical Mn–Co mixed oxides supported on silicalite-1 foam catalyst for catalytic combustion

Silicalite-1 (S1) foam was functionalized by supporting manganese–cobalt (Mn–Co) mixed oxides to develop the structured hierarchical catalyst (Mn–[email protected]) for catalytic combustion for the first time. The self-supporting S1 foam with hierarchical porosity was prepared via hydrothermal synthesis with polyurethane (PU) foam as the template. Subsequently, Mn–Co oxide nano sheets were uniformly grown on the surface of S1 foams under hydrothermal conditions to prepare the structured hierarchical catalyst with specific surface area of 354 m2·g−1, micropore volume of 0.141 cm3·g−1 and total pore volume of 0.217 cm3·g−1, as well as a good capacity to adsorb toluene (1.7 mmol·g−1 at p/p0 = 0.99). Comparative catalytic combustion of toluene of over developed structured catalyst Mn–[email protected] was performed against the control catalysts of bulk Mn–[email protected] (i.e., the crushed Mn–[email protected]) and unsupported Mn–Co oxides (i.e., Mn–Co). Mn–[email protected] exhibited comparatively the best catalytic performance, that is, complete and stable toluene conversion at 248 °C over 65 h due to the synergy between Mn–Co oxides and S1 foam, which provided a large number of oxygen vacancies, high redox capacity. In addition, the hierarchical porous structure also improved the accessibility of active sites and facilitated the global mass transfer across the catalyst bed, being beneficial to the catalysis and catalyst longevity.