Performance In Oxidation Of Toluene Research Articles

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.

Efficacious destruction of typical aromatic hydrocarbons over CoMn/Ni foam monolithic catalysts with boosted activity and water resistance

Developing cost-effective monolith catalyst with superior low-temperature activity is critical for oxidative efficacious removal of industrial volatile organic compounds (VOCs). However, the complexity of the industrial flue gas conditions demands the need for high moisture tolerance, which is challenging. Herein, CoMn–Metal Organic Framework (CoMn–MOF) was in situ grown on Ni foam (NiF) at room temperature to synthesize the cost-effective monolith catalyst. The optimized catalyst, Co1Mn1/NiF, exhibited excellent performance in toluene oxidation (T90 = 239 °C) due to the substitution of manganese into the cobalt lattice. This substitution weakened the Co–O bond strength, creating more oxygen vacancies and increasing the active oxygen species content. Additionally, experimentally and computationally evidence revealed that the mutual inhibiting effect of three typical aromatic hydrocarbons (benzene, toluene and m–xylene) over the Co1Mn1/NiF catalyst was attributed to the competitive adsorption occurring on the active site. Furthermore, the Co1Mn1/NiF catalyst also presents outstanding water resistance, particularly at a concentration of 3 vol%, where the activity is even enhanced. This was attributed to the lower water adsorption and dissociation energy derived from the interaction between the bimetals. Results demonstrate that the dissociation of water vapor enables more reactive oxygen species to participate in the reaction which reduces the formation of intermediates and facilitates the reaction. This investigation provides new insights into the preparation of oxygen vacancy–rich monolith catalysts with high water resistance for practical applications.

Single-crystal oxygen-rich bismuth oxybromide nanosheets with highly exposed defective {10–1} facets for the selective oxidation of toluene under blue LED irradiation

Reactive radicals are crucial for activating inert and low-polarity C(sp3)-H bonds for the fabrication of high value-added products. Herein, novel single-crystal oxygen-rich bismuth oxybromide nanosheets (Bi4O5Br2 SCNs) with more than 85 % {10–1} facets exposure and oxygen defects were synthesized via a facile solvothermal route. The Bi4O5Br2 SCNs demonstrated excellent photocatalytic performance in the selective oxidation of toluene under blue light. The yield of benzaldehyde was 1876.66 μmol g−1 h−1, with a selectivity of approximately 90 %. Compared to that of polycrystalline Bi4O5Br2 nanosheets (Bi4O5Br2 PCNs), the activity of Bi4O5Br2 SCNs exhibit a 21-fold increase. Experimental studies and density functional theory (DFT) calculations have demonstrated that the defect Bi4O5Br2 (10–1) facets exhibits exceptional adsorption properties for O2 molecules. In addition, the single-crystal structure in the presence of surface defects significantly increases the separation and transport of photogenerated carriers, resulting in the effective activation of adsorbed O2 into superoxide radicals (•O2–). Subsequently, the positively charged phenylmethyl H is readily linked to the negatively charged superoxide radical anion, thereby activating the CH bond. This study offers a fresh perspective and valuable insights into the development of efficient molecular oxygen-activated photocatalysts and their application in the selective catalytic conversion of aromatic C(sp3)-H bonds.

Tuning the crystallinity of the MnOx catalysts to promote toluene catalytic oxidation

ABSTRACT In this paper, the MnOx catalysts with excellent toluene oxidation performance were prepared by a simple precipitation method. The physicochemical properties of the prepared MnOx catalysts were investigated by XRD, BET, H2-TPR, O2-TPD and XPS. The obtained results revealed that the crystallinity of the prepared MnOx catalysts could be effectively regulated by changing the (NH4)2CO3/Mn(NO3)2 molar ratio, and thus affecting the oxygen vacancy concentration of the prepared MnOx catalysts. The prepared MnOx-4 catalyst with the (NH4)2CO3/Mn(NO3)2 molar ratio of 4.0 had the poor crystallinity and small grain size, which effectively promoted the oxygen defects in the MnOx catalyst to be formed. At the same time, the MnOx-4 catalyst had a large specific surface area, the highest low temperature reducibility and the largest number of oxygen vacancies and surface adsorbed oxygen species, which allowed more surface oxygen species to participate in the redox reaction, and promoted the toluene deep oxidation. Therefore, when the (NH4)2CO3/Mn(NO3)2 molar ratio was 4.0, the prepared MnOx-4 catalyst exhibited an excellent toluene catalytic oxidation performance and robust catalytic stability. What’s more, the toluene oxidation conversion on the MnOx-4 catalyst reached 99% at 230°C, and the MnOx-4 catalyst showed excellent resistance to water vapour.

Construction of core–shell structured CrOx/NiCoxO4 catalyst for low temperature catalytic oxidation of toluene: Understanding the reactivity promotion mechanism of the core–shell interactions

Bimetallic-based spinels are potential materials for toluene oxidation ascribing to their remarkable stability and oxidation activity. However, the insufficient toluene adsorption capacity and limited reactive oxygen species severely restrict their low-temperature catalytic reactivity. This study reports a facile two-step solvothermal strategy for the synthesis of core–shell structured CrOx/NiCoxO4 catalyst, which exhibits excellent toluene oxidation performance with T50 and T90 values of 187 and 218 °C, respectively, and the toluene conversion remains above 90 % at 218 °C for 20 h. The in-situ DRIFTs indicate that the oxidation of toluene to CO2 and H2O follows Mars-van Krevelen (MvK) mechanism, and the rate limiting step is the oxidation of maleic anhydride. The strong interaction between core NiCo2O4 and shell Cr2O3 regulates the morphology of Cr2O3 from particles to porous flocculent structure, which increases the porosity of catalyst and promotes the adsorption of toluene for further oxidation. Moreover, the interaction promotes the charge transfer from NiCo2O4 to Cr2O3, which increases the adsorbed oxygen species contents and the redox capability of the catalyst. A further density functional theory (DFT) calculation confirms that the core NiCo2O4 is the main active component, where the oxygen vacancy formation energy of NiCo2O4 and Cr2O3 decrease from 2.43 and 3.85 eV to 0.31 and 1.52 eV, while the toluene adsorption energy decrease from −0.04 and −0.94 eV to −5.29, and −4.48 eV, respectively, which evidently demonstrates that the formation of core–shell structured CrOx/NiCoxO4 would significantly promote the adsorption and oxidation of toluene, thereby exhibiting excellent low temperature toluene oxidation reactivity.

Application insights of environmental catalysts: Synergistic effects of cellulose-based porogens and catalytic metal sites in toluene catalytic oxidation

Utilizing environmentally-friendly bacterial cellulose as a scaffold, a highly porous, layered OA-BC catalyst was synthesized through an enhanced sol-gel process. This catalyst demonstrated exceptional performance in the oxidation of toluene, outperforming conventional alternatives that utilize chemical porogens. The OA-BC catalyst efficiently degrades toluene at 220℃ with high stability and hydrophobicity, indicating resistance to deactivation. Its superior activity is due to increased oxygen vacancies, enhanced metal oxide cooperation, and a layered porous structure, which together enhance active oxygen species and oxygen diffusion. Calcination of the OA-BC catalyst results in molecular cleavage and formation of small aggregates, increasing hydroxyl groups that stabilize Cu and Ce centers, enhancing toluene-oxygen reactions. In-situ infrared and X-ray photoelectron spectroscopy confirm stable monodentate Cu+ ligands, contributing to its high catalytic activity. This study introduces a novel approach by employing bacterial cellulose as a template for synthesizing a porous stratified OA-BC catalyst, demonstrating superior performance in toluene oxidation. The efficacy of catalyst results from a tripartite synergy involving the stratified porous architecture, the stabilizing effect of Cu+-coordinating ligands and hydroxyl groups, and the interplay of hydroxyl electron donors and acceptors, shedding light on environmentally benign catalyst development.

A novel CeO2 nanowire catalyst prepared by the freeze-drying method with significantly improved catalytic performance for toluene oxidation

A wire like CeO2 catalyst (CeO2-w) was obtained after the calcination of the precursor at 400 °C, which was prepared by the freeze-drying method for the first time. It shows good performance for catalytic oxidation of toluene with T90 of 220 °C, which is much better than the CeO2 catalysts with other structures prepared by the different methods. The good performance of CeO2-w is due to the bigger pore volume, more active oxygen species, more oxygen vacancies, better low temperature reducibility, higher surface area normalized reaction rates and lower Ea value. Additionally, the CeO2-w catalyst exhibits good water resistance and catalyst stability. In situ DRIFTS indicates the catalytic oxidation of toluene on CeO2-w undergoes the progress of toluene → benzaldehyde → benzoic acid → maleic acid → CO2 and H2O. This work affords a new idea to prepare high active CeO2 nanowire catalysts for catalytic oxidation of toluene, and open an efficient way for the construction of CeO2 based composite catalysts for VOCs 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.

Establishing efficient toluene elimination over cobalt-manganese bimetallic oxides via constructing strong Co–Mn interaction

Doping proves to be an efficacious method of establishing intermetallic interactions for enhancing toluene oxidation performance of bimetallic oxides. However, conventional bimetallic oxide catalysts are yet to overcome their inadequacy in establishing intermetallic interactions. In this work, the dispersion of Mn–Co bimetallic sites was improved by hydrolytic co-precipitation, strengthening the intermetallic interactions which improved the structural and physicochemical properties of the catalysts, thus significantly enhancing its catalytic behavior. MnCo–H catalysts fabricated by the hydrolytic co-precipitation method showed promising catalytic performance (T50 = 223 °C, T90 = 229 °C), robust stability (at least 100 h) and impressive water resistance (under 10 vol.% of water) for toluene elimination. Hydrolytic co-precipitation has been found to improve dispersion of MnCo elements and to enhance interaction between Co and Mn ions (Mn4+ + Co2+ = Mn3+ + Co3+), resulting in a lower reduction temperature (215 °C) and a weaker Mn–O bond strength, creating more lattice defects and oxygen vacancies, which are responsible for superior catalytic properties of MnCo–H samples. Furthermore, in situ DRIFTs showed that gaseous toluene molecules adsorbed on the surface of MnCo–H were continuously oxidized to benzyl alcohol → benzaldehyde → benzoate, followed by a ring-opening reaction with surface-activated oxygen to convert to maleic anhydride as the final intermediate, which further generates water and carbon dioxide. It was also revealed that the ring-opening reaction for the conversion of benzoic acid to maleic anhydride is the rate-controlling step. This study reveals that optimizing active sites and improving reactive oxygen species by altering the dispersion of bimetals to enhance bimetallic interactions is an effective strategy for the improvement of catalytic behavior, while the hydrolytic co-precipitation method fits well with this corollary.

V2O5 modified Mn/SAPO-34 catalyst for the synchronous elimination of NOx and volatile organic compounds

In this work, a new V-Mn bimetallic multifunctional catalyst based on SAPO-34 zeolite was constructed to achieve synchronous elimination of VOCs and NOx in denitrification zone conditions. The V-Mn/SAPO-34 catalyst exhibited excellent catalytic performance for toluene oxidation and NO reduction and remarkable flue gas tolerance compared to Mn/SAPO-34 and V/SAPO-34. The T90 (265 °C) of V-Mn/SAPO-34 for toluene oxidation was 30 °C and 125 °C lower than that of Mn/SAPO-34 (295 °C) and V/SAPO-34, respectively. Moreover, the conversion of NO could reach more than 90% at 138 °C. Excellent catalytic activity of the V-Mn/SAPO-34 was attributed to abundant hierarchical pores, oxygen vacancies and acidic sites owing to ion exchanges of SAPO-34. Meanwhile, the favorable V-Mn synergy effectively facilitated the electron transfer of catalytic reaction. In situ DRIFTS results indicated that the toluene oxidation over it followed the MvK mechanism, while the NH3-SCR followed the E-R mechanism, and the two, proceeding independently, did not interfere with each other during synchronous elimination.

MOF-derived FeOx with highly dispersed active sites as an efficient catalyst for enchaning catalytic oxidation of VOCs

Highly efficient and stable catalysts serve as the crucial factor in VOCs catalytic oxidation technology. Iron-based materials are recognized as potential VOCs catalysts due to their cost-effectiveness and non-toxic nature. However, the limited catalytic performance of traditional iron oxide catalysts hinders their further industrial applications. A series of FeOx catalysts were synthesized via pyrolysis of Fe-based MOFs with diverse morphologies for toluene catalytic oxidation. Characterization results demonstrated that the FeOx-100 catalyst performed optimal characteristics, including the abundant specific surface area and smaller crystallite size, which offered highly dispersed active sites and defects for toluene oxidation. The catalytic activity of FeOx-100 was improved by adjusting the precursors and pyrolysis conditions, achieving a 50% toluene conversion at 223 °C and 90% conversion at 249 °C. The redox abilities of FeOx catalysts were carefully evaluated to assess their impact on catalytic activity. The results confirmed that FeOx-100 exhibited superior low-temperature reducibility, remarkable presence of surface active oxygen and lattice oxygen species, jointly facilitating the toluene oxidation performance at lower temperatures. The results of in situ DRIFTS provided evidence supporting a degradation pathway for toluene, likely proceeding as follows: toluene→ benzaldehyde→ benzoate→ anhydride → …→ CO2 and H2O.

Modification of Fe on hydrophobic ZSM-5 zeolite: Optimization of adsorption and catalytic performance for decomposition of VOCs at low-temperature

The conjugation of high adsorption and excellent catalytic characteristics is desirable for the removal of volatile-organic-compounds (VOCs) at low-temperatures. In this study, ZSM-5 zeolites with varying Si/Al ratios (15, 30, 100, and 200) were synthesized using the hydrothermal-method to assess their adsorption capability for VOCs. Among them, the ZSM-5(30) sample exhibited a well-defined zeolite structure, exceptional hydrophobicity, a high surface area (SBET), and micropores, resulting in a higher toluene adsorption capacity of 135 mg/g compared to other adsorbents. Additionally, the ZSM-5(30) sample demonstrated excellent regenerative stability in both dry and humid environments. Consequently, ZSM-5(30), identified as the most effective adsorbent, was subjected to loading with various amounts of Fe metal for the catalytic-oxidation of toluene at low-temperatures. Due to its abundant oxygen-vacancies, adequate acid-sites, and various active oxygen-species, the Fe0.2/ZSM-5(30) catalyst (Fe/(Si + Al) = 0.2) not only exhibited a high adsorption capacity for toluene with good stability over five successive cycles but also demonstrated excellent performance in the catalytic oxidation of toluene. The complete conversion of toluene was attained at temperatures approximately 200 °C, with a gas hourly space velocity (GHSV) of 20,000 mL/(g∙h), and maintained stability for 40 h. Furthermore, in-situ diffuse-reflectance infrared-Fourier-transform-spectroscopy (DRIFTS) and gas chromatography-mass spectrometry (GC–MS) results, along with the Mars-Van-Krevelen model, were utilized to elucidate the adsorption and oxidation mechanism of toluene. The unique adsorption and oxidation capabilities of Fe0.2/ZSM-5(30) for toluene indicate its promising potential for the removal of VOCs in real industrial-environments. This study provides valuable insights for the design of high-performance bifunctional materials for the adsorption and catalytic-oxidation of VOCs.

Cobalt-doped cerium dioxide enhances interfacial synergistic catalysis for boosting the oxidation of toluene

The CoCeOx nanoparticles (CoCeOx-NP) with different Co/Ce molar ratios were successfully prepared and applied to toluene oxidation. Appropriate Co-doped CeO2 significantly enhanced the interfacial synergistic catalysis to boost toluene oxidation. CoCeOx-2-NP exhibited the highest toluene conversion activity (T50 = 203 °C, T90 = 209 °C) and CO2 selectivity under the high weight hourly space velocity (WHSV). Various characterizations were performed to comprehensively analyze the relationship between the structure and performance of the catalysts. The high Oβ/Otot, good oxygen mobility, and the synergistic effects between cobalt and cerium showed excellent performance for toluene oxidation at lower temperatures. Besides, the CoCeOx-2-NP catalysts exhibited good stability and reusability, making them potential for practical applications in toluene oxidation. Notably, the XPS, DFT, and in situ DRIFTS further investigated the pathway of toluene oxidation, which lays a foundation for an in-depth understanding of the oxidation behavior of toluene and the subsequent development of efficient catalytic materials.

Light-driven photothermocatalytic performance of the Pt/Co3O4 catalyst for toluene oxidation

Light-driven photothermocatalytic oxidation is a promising method for the elimination of volatile organic compounds (VOCs). The Co3O4, 0.46 Pt/Co3O4 and 0.97 Pt/Co3O4 catalysts were fabricated via the simple molten salt and incipient wetness impregnation method. Compared with Co3O4 and 0.46 Pt/Co3O4, the 0.97 Pt/Co3O4 catalyst showed higher photothermocatalytic performance for toluene oxidation under simulated solar irradiation intensity of 900 ​mW ​cm−2, with the toluene conversion and CO2 yield being up to 98.3 % and 96.0 %, respectively. The better activity was ascribed to its outstanding strong light absorption and low temperature reducibility. Meanwhile, 0.97 Pt/Co3O4 also exhibited an excellent photothermocatalytic stability and H2O resistance. The Vis−IR light played a key role in the photothermocatalytic oxidation of toluene in the whole solar spectrum. This work benefited the synthesis of catalysts with good photothermocatalytic activity for environment friendly treatment of VOCs.

Synthesis of Layered Lead-Free Perovskite Nanocrystals with Precise Size and Shape Control and Their Photocatalytic Activity.

Halide perovskites have attracted enormous attention due to their potential applications in optoelectronics and photocatalysis. However, concerns over their instability, toxicity, and unsatisfactory efficiency have necessitated the development of lead-free all-inorganic halide perovskites. A major challenge in designing efficient halide perovskites for practical applications is the lack of effective methods for producing nanocrystals with precise size and shape control. In this work, a layered perovskite, Cs4ZnSb2Cl12 (CZS), is found from calculations to exhibit size- and facet-dependent optoelectronic properties in the nanoscale, and thus, a colloidal method is used to synthesize the CZS nanoparticles with size-tunable morphologies: zero- (nanodots), one- (nanowires and nanorods), two- (nanoplates), and three-dimensional (nanopolyhedra). The growth kinetics of the CZS nanostructures, along with the effects of surface ligands, reaction temperature, and time were investigated. The optoelectronic properties of the nanocrystals varied with size due to quantum confinement effects and with shape due to anisotropy within the crystals and the exposure of specific facets. These properties could be modulated to enhance the visible-light photocatalytic performance for toluene oxidation. In particular, the 9.7 nm CZS nanoplates displayed a toluene to benzaldehyde conversion rate of 1893 μmol g-1 h-1 (95% selectivity), 500 times higher than the bulk synthesized CZS, and comparable with the reported photocatalysts. This study demonstrates the integration of theoretical calculations and synthesis, revealing an approach to the design and fabrication of novel, high-performance colloidal perovskite nanocrystals for optoelectronic and photocatalytic applications.

Achieving High Selectivity in Photocatalytic Oxidation of Toluene on Amorphous BiOCl Nanosheets Coupled with TiO2.

The inert C(sp3)-H bond and easy overoxidation of toluene make the selective oxidation of toluene to benzaldehyde a great challenge. Herein, we present that a photocatalyst, constructed with a small amount (1 mol %) of amorphous BiOCl nanosheets assembled on TiO2 (denoted as 0.01BOC/TiO2), shows excellent performance in toluene oxidation to benzaldehyde, with 85% selectivity at 10% conversion, and the benzaldehyde formation rate is up to 1.7 mmol g-1 h-1, which is 5.6 and 3.7 times that of bare TiO2 and BOC, respectively. In addition to the charge separation function of the BOC/TiO2 heterojunction, we found that the amorphous structure of BOC endows its abundant surface oxygen vacancies (Ov), which can further promote the charge separation. Most importantly, the surface Ov of amorphous BOC can efficiently adsorb and activate O2, and amorphous BOC makes the product, benzaldehyde, easily desorb from the catalyst surface, which alleviates the further oxidation of benzaldehyde, and results in the high selectivity. This work highlights the importance of the microstructure based on heterojunctions, which is conducive to the rational design of photocatalysts with high performance in organic synthesis.

Enhanced catalytic activity of toluene oxidation over in-situ prepared Mn3O4-Fe2O3 with acid-etching treatment

Mn3O4-Fe2O3 composite catalysts are in-situ synthesized via advanced oxidation followed by modifying with hydrochloric acid to improve the catalytic toluene oxidation performance. Mn3O4-Fe2O3 modified with 1.0 M HCl (A-1.0) exhibited best activity of toluene oxidation. The temperature of 50% toluene conversion is 245 °C and the temperature of 90% conversion is 279 °C. There are much more abundant surface lattice oxygen species and higher amount of high valence manganese and iron ions on A-1.0 catalyst, which are beneficial for improving catalytic activity. In-situ DRIFTs indicated that benzaldehyde and benzoic acid are main intermediate products on A-1.0 catalyst during toluene oxidation.

Influence of MnO2 crystal existing form on its catalytic performance for toluene oxidation

A series of MnO2 catalysts with different crystal forms were synthesized by in situ self-doping of Mn induced by bridging interaction between Mn and carboxyl group under moderate medium, and applied to catalytic oxidation of toluene. XRD, SEM and TEM results show that the physical structure of the prepared catalyst is extremely sensitive to the ratio of Mn/CA. Only MnCA-4 catalyst has a special morphology with double crystal and a uniform mixture of rod-like and spherical structures, and some of them are hollow rod-like structures. Due to the interaction between different phase structures, the mixed MnCA-4 catalyst with dual crystal has the best catalytic performance of toluene oxidation, which can oxidize 90 % toluene at 228 °C. The characterization of H2-TPR, O2-TPD, and XPS proved that the strong interaction between different crystalline forms of manganese oxide led to the generation of more oxygen vacancies and Mn3+ species. In situ DRIFTS results show thatMnCA-4 catalyst has stronger ability to adsorb and activate toluene compared with MnCA-12 catalyst, which may be the main reason for its excellent catalytic oxidation performance of toluene. This study provides an effective strategy for designing high efficiency non-noble metal catalysts to construct interface engineering of different crystal types.

Nitrogen-Doped Porous Carbon from Biomass with Efficient Toluene Adsorption and Superior Catalytic Performance.

The chemical composition and surface groups of the carbon support affect the adsorption capacity of toluene. To investigate the effect of catalyst substrate on the catalytic performance, two different plant biomasses, banana peel and sugarcane peel, were used as carbon precursors to prepare porous carbon catalyst supports (Cba, Csu, respectively) by a chemical activation method. After decorating PtCo3 nanoparticles onto both carbon supports (Cba, Csu), the PtCo3-su catalyst demonstrated better catalytic performance for toluene oxidation (T100 = 237 °C) at a high space velocity of 12,000 h-1. The Csu support possessed a stronger adsorption capacity of toluene (542 mg g-1), resulting from the synergistic effect of micropore volume and nitrogen-containing functional groups, which led to the PtCo3-su catalyst exhibiting a better catalytic performance. Moreover, the PtCo3-su catalyst also showed excellent stability, good water resistance properties, and high recyclability, which can be used as a promising candidate for practical toluene catalytic combustion.

PdPty/V2O5-TiO2: Highly Active Catalysts with Good Moisture- and Sulfur Dioxide-Resistant Performance in Toluene Oxidation

Catalytic performance and moisture and sulfur dioxide resistance are important for a catalyst used for the oxidation of volatile organic compounds (VOCs). Supported noble metals are active for VOC oxidation, but they are easily deactivated by water and sulfur dioxide. Hence, it is highly desired to develop a catalyst with high performance and good moisture and sulfur dioxide resistance in the oxidation of VOCs. In this work, we first adopted the hydrothermal method to synthesize a V2O5-TiO2 composite support, and then employed the polyvinyl alcohol (PVA)-protecting NaBH4 reduction strategy to fabricate xPdPty/V2O5-TiO2 catalysts (x and y are the PdPty loading (0.41, 0.46, and 0.49 wt%) and Pt/Pd molar ratio (2.10, 0.85, and 0.44), respectively; the corresponding catalysts are denoted as 0.46PdPt2.10/V2O5-TiO2, 0.41PdPt0.85/V2O5-TiO2, and 0.49PdPt0.44/V2O5-TiO2). Among all the samples, 0.46PdPt2.10/V2O5-TiO2 exhibited the best catalytic activity for toluene oxidation (T50% = 220 °C and T90% = 245 °C at a space velocity of 40,000 mL/(g h), apparent activation energy (Ea) = 45 kJ/mol), specific reaction rate at 230 °C = 98.6 μmol/(gPt s), and turnover frequency (TOFNoble metal) at 230 °C = 142.2 × 10−3 s−1. The good catalytic performance of 0.46PdPt2.10/V2O5-TiO2 was associated with its well-dispersed PdPt2.10 nanoparticles, high adsorbed oxygen species concentration, good redox ability, large toluene adsorption capacity, and strong interaction between PdPty and V2O5-TiO2. No significant changes in toluene conversion were detected when 5.0 vol% H2O or 50 ppm SO2 was introduced to the reaction system. According to the characterization results, we can realize that vanadium is the main site for SO2 adsorption while PdO is the secondary site for SO2 adsorption, which protects the active Pt site from being poisoned by SO2, thus making the 0.46PdPt2.10/V2O5TiO2 catalyst show good sulfur dioxide resistance.