Activity For Toluene Combustion Research Articles

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 oxidation of toluene by binary metal oxide Cr2O3/CeO2 from MIL-101 (Cr)

Volatile organic compounds (VOCs) not only pollute the environment, but also seriously damage human health. Studies have shown that CeO2 doped with Cr and other metal elements can significantly improve its catalytic activity. In this paper, MIL-101 (Cr) was selected as the precursor of Cr2O3, and x wt%Cr2O3/CeO2 catalysts (x = 5, 10, 15) with different loadings were prepared by impregnation method. The physicochemical properties of the catalysts were characterized by XRD, SEM, BET, XPS and H2-TPR, and their catalytic performance was evaluated by toluene catalytic combustion. The results show that 10 wt%Cr2O3/CeO2 exhibits the best catalytic activity for toluene combustion, and the conversion of toluene can reach 90% at 263 °C. This can be attributed to the relatively high specific surface area (118 m2 g−1), the highest surface adsorbed oxygen content (Oads/Ototal = 0.251), oxygen vacancy content, more surface Ce3+ species and Cr6+ species, and the best low-temperature reducibility.

Study on the mechanism of sulfur poisoning in toluene catalyzed by Co3O4/γ-Al2O3 sulfur tolerant catalyst containing spinel structure

In this paper, in-situ thermal decomposition of ammonium sulfate method was used to cause sulfur poisoning of Co3O4/γ-Al2O3 catalyst rapidly and quantitatively. The pore structure, valence state of active species, surface morphology and acidity of the catalyst before and after sulfur poisoning were characterized, and its influence on catalytic combustion of toluene was studied. The results showed the crystal shape of the catalyst changed little after sulfur poisoning. As sulfur poisoning gradually deepened, the formation of sulfate blocked the pores, the high-valence cobalt decreased, strong acid sites increased, and its catalytic activity for toluene combustion gradually decreased. Formation of cobalt sulfate was a main reason for the decline in catalyst activity. Spinel phase CoAl2O4 formed outside γ-Al2O3 framework can adsorb a large amount of sulfur species to form sulfate, protecting Co3O4 and delaying the deactivation of catalysts.

Modulating the exposed facets of CeO2 nanorods by MoO42– inducing to promote low-temperature photothermocatalytic toluene combustion

Photothermocatalysis is a synergetic process with the participation of both thermal and light energies, and ceria is a promising candidate as photothermocatalysts for VOCs combustion. Nevertheless, how its exposed facets affect the photothermocatalytic activity remains dubious, since suitable facet control strategies are scarce. Herein, we exploit a “MoO42– inducing” method to modulate the exposed facets of CeO2 nanorods from (111) to (100) facet, and the effect of exposed facets on toluene combustion is systematically investigated. As compared to CeO2 nanorods with only the (111) facet, CeO2 nanorods with the (100) and (111) facets have more reducible Ce4+ and edge/corner defect-derived Ce3+ with stronger ability to capture O2, thereby leading to the higher thermocatalytic activity for toluene combustion; The Ce–O bonds at the (100) facet are more easily photoactivated, which is responsible for the more significant activity enhancement upon participation of both thermal and light energies. Additionally, in situ FTIR analysis shows that photothermocatalytic toluene combustion over ceria probably follows the process: toluene→ benzyl alcohol → benzaldehyde, benzoic acid, aliphatic aldehyde/acid→ anhydride → carbonate →CO2 and H2O. The work supplies new insight into correlation between ceria exposed facets and photothermocatalytic activity.

Promoting Pd/Al2O3 catalysts for toluene combustion by DBD plasma treating in different working gas atmospheres

To investigate the effects of plasma treatment on supported precious metals for VOCs combustion, a series of 1%Pd/Al2O3 catalysts were synthesized by DBD plasma treating in different working gases (H2/Ar, O2, N2, Air) and with reversed calcination sequences. It is revealed that both the working gas and treating sequence can alter the Pd dispersion degree, valence states and the concentration of surface acid sites, which subsequently impacts the catalytic activity. Usually, a Pd/Al2O3 catalyst with a higher active Pd surface area shows higher toluene combustion activity, due to the promoted ability to adsorb and activate toluene molecules. Therefore, Pd dispersion degree is the main factor to determine the reactivity of Pd/Al2O3 catalysts. Moreover, H2/Ar plasma treating can effectively create Pd0 sites, which is favorable to toluene and O2 molecule adsorption and activition. Due to the combination of these two factors, 1%Pd/Al2O3-C-H2P displays the best activity among all the samples.

Enhanced Performance of Supported Ternary Metal Catalysts for the Oxidation of Toluene in the Presence of Trichloroethylene

Chlorinated volatile organic compounds (CVOCs), even in small quantities, can cause Pt-based catalyst poisoning. Improving the low-temperature chlorine resistance of catalysts is of vital importance for industrial application, although it remains challenging. Considering actual industrial production, a TiO2-supported ternary metal catalyst was prepared in this work to study the catalytic oxidation of multicomponent VOCs (toluene and trichloroethylene (TCE)). Among all of the samples, PtWRu/TiO2 and PtWCr/TiO2 exhibited the best catalytic performance for toluene oxidation. In the mixed VOC oxidation, the PtWCr/TiO2 sample showed the best catalytic activity for toluene combustion (a toluene conversion of 90% was achieved at 258 °C and a space velocity of 40,000 mL g−1 h−1, and the specific reaction rate and turnover frequency at 215 °C were 44.9 × 10−6 mol gPt−1 s−1 and 26.2 × 10−5 s−1). The PtWRu/TiO2 sample showed the best catalytic activity for TCE combustion (a TCE conversion of 90% was achieved at 305 °C and a space velocity of 40,000 mL g−1 h−1, and the specific reaction rate and turnover frequency at 270 °C were 9.0 × 10−6 mol gPt−1 s−1 and 7.3 × 10–5 s−1). We concluded that the ternary metal catalysts could greatly improve chlorine desorption by increasing the active lattice oxygen mobility and surface acidity, thus reducing chlorinated byproducts and other serious environmental pollutants. This work may serve as a reasonable design reference for solving more practical industrial production emissions of multicomponent VOCs.

Active surface RuOx species originating from size-driving self-dispersion process for toluene catalytic combustion

Catalytic combustion method is an effective way to degrade aromatic volatile organic compounds (VOCs). The size of Ru species significantly affect the catalytic performance, while lack of enough concern for VOCs catalytic oxidation. In this work, we deposited a series of Ru nanoparticles (1.6, 2.9, and 3.6 nm) on CeO2 support for toluene catalytic combustion, and reported a size-dependent performance under oxidizing atmosphere. The catalytic performance was improved with the decrease of Ru size (T90 = 214 °C on 1.6RuCe-SD, compared to 228 °C of 3.6RuCe-SD, and 244 °C of RuCe-IM). The drastic activity improvement may result from the smallest size of Ru and the highest formation degree of coordinatively-unsaturated sites during a self-dispersion (redispersion) process. The active surface RuOx species originating from the smaller Ru contain a higher ratio of active Run+, oxygen vacancy, and stronger ability to facilitate dehydrogenation and aromatic ring breakage, thus eventually boosting the toluene combustion activity. This work brings forward a simple strategy to expose coordinatively-unsaturated sites based on size-driving self-dispersion for catalyst design for the elimination of typical VOCs and other environmental applications.

Effect of oxide-ion conductivity of apatite-type Ln10Si6O27 on catalytic activity for toluene combustion

ABSTRACT By using apatite-type Ln10Si6O27 (Ln = La, Sm, Gd) solids with oxide-ion-conduction properties, the effect of conductivity on the catalytic activity of 1 wt% Pt/Ln10Si6O27 for toluene combustion was clarified. With increasing Ln3+ ion size, the lattice volume of Ln10Si6O27 increased, resulting in the enhancement of the conductivity, likely due to the expansion of the oxide-ion-conducting pathway; that is, the conductivity increased in the order Gd10Si6O27 < Sm10Si6O27 < La10Si6O27. The conductivity of the Ln10Si6O27 promoter affected the oxygen release ability of 1 wt% Pt/Ln10Si6O27, which led to the oxidation of Pt0 to Pt2+/4+. Correspondingly, the Pt/Ln10Si6O27 catalyst facilitated toluene combustion, and the catalytic activity increased in the order 1 wt% Pt/Gd10Si6O27 < 1 wt% Pt/Sm10Si6O27 < 1 wt% Pt/La10Si6O27; this order was not consistent with the surface area, Pt dispersion, or acidity. These results indicate that the catalytic activity was affected by the conductivity of the Ln10Si6O27 promoter.

Optimized Synthesis Routes of MnOx-ZrO2 Hybrid Catalysts for Improved Toluene Combustion

In this contribution, the three Mn-Zr catalysts with MnxZr1−xO2 hybrid phase were synthesized by two-step precipitation route (TP), conventional coprecipitation method (CP) and ball milling process (MP). The components, textural and redox properties of the Mn-Zr hybrid catalysts were studied via XRD, BET, XPS, HR-TEM, H2-TPR. Regarding the variation of synthesis routes, the TP and CP routes offer a more obvious advantage in the adjustment of the concentration of MnxZr1−xO2 solid solution compared to the MP process, which directly commands the content of Mn4+ and oxygen vacancy and lattice oxygen, and thereby leads to the enhanced mobility of reactive oxygen species and catalytic activity for toluene combustion. Moreover, the TP-Mn2Zr3 catalyst with the enriched exposure content of 51.4% for the defective (111) lattice plane of MnxZr1−xO2 exhibited higher catalytic activity and thermal stability for toluene oxidation than that of the CP-Mn2Zr3 sample with a value of 49.3%. This new observation will provide a new perspective on the design of bimetal catalysts with a higher VOCs combustion abatement.

A facile preparation of hausmannite as a high-performance catalyst for toluene combustion

Mesoporous transition metal oxide catalysts are well-used in the elimination of volatile organic compounds. In this study, we developed an efficient method for the preparation of mesoporous-Mn 3 O 4 (m-Mn 3 O 4 ) without the use of templates or surfactants. In this method, KCl protects oxygen defects on the surface of fresh Mn 3 O 4 crystallites. m-Mn 3 O 4 shows higher ameliorative catalytic activity than bulk-Mn 3 O 4 (b-Mn 3 O 4 ) and calcined-Mn 3 O 4 (c-Mn 3 O 4 ), achieving toluene catalytic oxidation of T 10 and T 90 (the temperature at a conversion rate of about 10% and 90%) at 191 ℃ and 230 ℃, respectively (WHSV = 40,000 ml·g −1 ·h −1 ). Based on various characterizations, the prepared m-Mn 3 O 4 has large specific surface area and abundant oxygen defects, and thus can provide more surface active sites, which give it superior toluene combustion activity.

Weak sunlight-driven mass toluene combustion through scalable Cu doped CeO2 microspheres

Sunlight-driven toluene elimination system faces the problems of low reaction rate, secondary pollution, and especially tricky to large-scale production. In this work, we used a PVP assisted spray drying method to synthesize Cu doped CeO2 microspheres with the merits of zero waste water and solids discharge, kilogram level yield, uniform dispersion of Cu, and high toluene combustion activity. Further, a new photothermal device was constructed to heat catalysts to 295 °C under one standard sunlight irradiation. As a result, the new photothermal device supported Cu doped CeO2 microspheres showed a full oxidation of toluene at the rate of 59.82 mmol g−1 h−1 under 1 sun irradiation, 150 times higher than the advanced sunlight-driven toluene elimination. An industrial demonstration of this new system was developed, and this system was able to completely deal with 22.2 m3 h−1 of exhaust with the toluene concentration of 1–10,000 ppm under 1 m2 of outdoor sunlight irradiation in the daytime of winter, showing the potential on industrial applications.

Effect of A-site element on the performance of three-dimensionally ordered macroporous manganese-based perovskite catalyst

Three-dimensionally ordered macroporous manganese-based perovskite catalyst (3DOM AMnO3, A = Ce, La, Ni) were synthesized by PMMA hard-templating and impregnation method. Physicochemical properties of the samples were characterized by means of various techniques including XRD, BET, SEM, TEM, XPS and H2-TPR, and their catalytic activities were evaluated by toluene combustion. It was found that the 3DOM AMnO3 in each of the samples was perovskite in crystal structure, and only the samples possessed a good quality 3DOM architecture with a surface area of 48.8 m2/g. Due to the highest adsorbed oxygen species concentration (Oads/Olatt = 2.330), the best low-temperature reducibility (The low-temperature reduction peaks of 3DOM CeMnO3 catalysts occur at 425 °C) and the strong interaction between CeO2 and MnOx formed during calcination. The 3DOM CeMnO3 sample showed lower apparent activation energy (34.51 kJ·mol−1, SV = 15,000 h−1) and the best catalytic activity for toluene combustion, with the reaction temperatures (T50%, and T90%) required for achieving toluene conversions of 50%, and 90% being 100 °C, 172 °C at SV = 15,000 h−1, respectively.

Supported ceria-modified silver catalysts with high activity and stability for toluene removal

Herein we fabricated the supported single-atom silver catalysts using an in situ molten salt method. The Mn2O3 nanowires supported single-atom silver catalyst (i.e., 0.06 wt% Ag/Mn2O3) exhibited excellent catalytic activity for toluene combustion, with the temperatures required for 50 and 90% of toluene conversions being 170 and 205 °C, respectively, at a space velocity of 40,000 mL/(g h). However, the toluene conversion at 205 °C quickly decreased from 90 to 30% within 2.5 h of on-stream reaction. Based on the various characterization results, we found that there were no aggregation of Ag particles, no change in crystal structure of the Mn2O3 nanowire support, and no carbon deposition on the catalyst surface, and the quick deactivation of 0.06 wt% Ag/Mn2O3 was mainly associated with the low oxygen activation ability. The proper CeO2 addition to the 0.06 wt% Ag/Mn2O3 catalyst was found to not only improve the catalytic activity but also significantly enhance the stability of the catalyst. Toluene conversion at 195 °C over 0.63 wt% CeO2-0.06 wt% Ag/Mn2O3 decreased by only 10% in 50 h of on-stream reaction. Because Ag and CeO2 particles were highly dispersed on the Mn2O3 nanowire support, the oxygen species formed at the surface oxygen vacancies of CeO2 could efficiently migrate to the active sites (i.e., the interface of Ag-Mn2O3) and replenish the surface reactive lattice oxygen species. Thus, the present single-atom silver catalyst is an alternative for commercial noble metal catalysts for the removal of VOCs.

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.

Fe-ZSM-5 supported palladium nanoparticles as an efficient catalyst for toluene abatement

Catalytic combustion is considered as an efficient and economic technology to remove VOCs, and Al-ZSM-5 zeolite supported palladium catalysts (Pd/Al-ZSM-5) with good performances in this kind of reactions have been reported. In this work, it is found that Fe-ZSM-5 supported palladium catalyst (Pd/Fe-ZSM-5) exhibit higher catalytic activity in toluene combustion than the Pd/Al-ZSM-5, which is strongly related to more Pd0 active species and higher concentration of absorbed oxygen species of Pd/Fe-ZSM-5 than those of Pd/Al-ZSM-5. More importantly, Pd/Fe-ZSM-5 has a good catalyst life and water-resistant ability, which should be potentially significant for practical applications in environment protection.

CoMnxOy nanosheets with molecular-scale homogeneity: an excellent catalyst for toluene combustion

The redox–precipitation technique yields molecularly dispersed CoMnxOy nanosheets with improved physicochemical properties compared to those obtained by a conventional co-precipitation method, leading to excellent catalytic activity in toluene combustion.

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.

Toluene catalytic combustion over copper modified Mn0.5Ce0.5 Ox solid solution sponge-like structures

Catalytic combustion is a well-established way to remove the pollution of volatile organic compounds (VOCs), and the highly active catalyst is the key issue of this process. Herein, a series of sponge-like ternary mixed oxide were prepared by a facile surfactant modified coprecipitation approach. The structure properties were characterized via BET, XRD, Raman, TEM, EDS, H2-TPR, and XPS techniques. It was found that the Cu content significantly influences the catalytic activity in toluene combustion. The CMC-2 (Cu:Mn:Ce=1:5:5) showed the best catalytic performance under the air atmosphere, and the complete conversion of toluene was achieved at 240°C. The characterization reveals that a proper amount of Cu facilitates the incorporation of highly reducible Mn4+ into ceria lattice to form sponge-like MnCeOx solid solution structures. Such promotion effect of copper can improve the redox behavior, produce large amounts of Oα at the interface of CuOx/MnCeOx, both of which benefit the toluene combustion at low temperature. The findings of this work highlight the importance of Cu in preparation of the active MnOx−CeO2 catalyst for VOCs combustion.

Syntheses of Hierarchical MnO2via H2O2 Selectively Reducing KMnO4 for Catalytic Combustion of Toluene

AbstractMnO2 materials were facilely prepared via the rapid redox reactions of KMnO4 and H2O2 in acidic medium, which exhibit the significant improvement of catalytic activity in the degradation of gaseous toluene compared to commercial MnO2. It was found that the molar ratio of H2O2/KMnO4 has a great influence on the crystalline phase, morphology and average oxidation state of the as‐prepared MnO2. The 3‐MnO2 sample prepared by using three equivalents of stoichiometric H2O2 displays the best catalytic activity for the total combustion of toluene (concentration is up to 1000 ppm) at 300 oC. The mechanism of the influence of different H2O2 addition amount has also been discussed by catalytic performance and nature of materials.

Physicochemical properties of hydrogel template-synthesized copper(ii) oxide-modified clay influencing its catalytic activity in toluene combustion

CuO-modified montmorillonite was synthesized by the template-assisted route.