Oxidation Of Volatile Organic Compounds Research Articles

Enhanced selective catalytic oxidation of triethylamine by VOx-modified CuO@TiO2 catalyst through increased amount of Lewis acid sites and adsorbed oxygen species on catalyst surface

The selective catalytic oxidation (SCO) of nitrogenous volatile organic compounds (NVOCs) has recently garnered significant attention. However, the SCO processes for tertiary amines (such as triethylamine) have not been reported. The impact of vanadium doping in CuO@TiO2 and Cu loading on SCO of TEA to N2 was investigated in this study. The surface acidity of the catalyst is primarily influenced by the VOx doping, as indicated by the results of NH3-TPD and pyridine-IR. Additionally, XPS and H2-TPR results reveal that the highly dispersed CuO species is the key oxidative component in the catalyst. SEM and TEM results show that VOx is beneficial to enhance the dispersion of CuO in the catalyst. The adsorbed oxygen content of CuO@TiO2 catalyst is increased by VOx-modification, as indicated by EPR result. An appropriate amount of adsorbed oxygen in the catalyst can improve the oxidation activity of the catalyst and assure high selectivity of N2. Finally, through the in-situ DRIFTs the reaction intermediate NHx is captured, and a reliable SCO reaction pathway of TEA is proposed. This study provides a solution for the disposal of tertiary amines from NVOCs.

Catalytic Oxidation of Volatile Organic Compounds Alone or in Mixture over Mg4Al2−xCex Mixed Oxides

This study investigates Ce-containing MgAl layered double hydroxides (LDH), focusing on its structural and catalytic properties. Mg4Al2−xCex (x = 0; 0.4; 0.8; 2) hydrotalcite-like compounds were prepared using the co-precipitation method. The effects of cerium content and calcination temperature on the structural and catalytic properties of Ce-containing MgAl LDH were investigated. The samples were characterized by XRD, BET, Raman, XPS, and DTA/TGA techniques. The catalytic activity of the resulting compound in n-butanol oxidation was studied. Increasing the calcination temperature (from 280 to 500 °C) caused changes in the structural, textural, and reducibility properties. The Mg4Al2−xCex LDH structure series (calcined at 280 °C) exhibited the highest catalytic activity, especially for x = 2. The material’s properties improved with increased Ce content, allowing complete butanol conversion below 280 °C. The formation of active sites occupied by cerium within the LDH structure, along with its reducibility properties, contributed to the material’s performance. The Ce3+/Ce4+ redox couple in the external layers enhanced O2− diffusion and their activation into nucleophilic species, facilitating butanol transformation. Adding water vapor to the reaction mixture slightly decreased the butanol oxidation, while the presence of ethyl acetate and butanol together exhibited a mutual inhibitory effect, with butanol demonstrating a more prominent influence.

Insights into non-crystalline structure of solid solution Ce-Mn co-oxide nanofibers for efficient low-temperature toluene oxidation.

The controllable preparation of efficient non-crystalline solid solution catalysts is a great challenge in the catalytic oxidation of volatile organic compounds. In this work, series non-crystalline solid solution structured Ce-Mn co-oxide nanofibers were creatively prepared by adjusting Ce/Mn molar ratios using electrospinning. 0.20CeMnOx (the ratio of Ce to Mn was 0.2) displayed an outstanding low-temperature toluene oxidation activity (T90 = 233 °C). The formation of the amorphous solid solution and the unique nanofiber structure both contributed to a large specific surface area (S = 173 m2 g-1) and high adsorbed oxygen content (Oads/O = 41.3%), which enhanced the number of active oxygen vacancies. The synergies between non-crystalline structure and active oxygen species markedly improved oxygen migration rate as well as redox ability of the catalysts. Additionally, in situ diffuse reflectance infrared Fourier transform spectra showed that the absorbed toluene could be completely oxidized to CO2 and H2O with benzyl alcohol, benzaldehyde, benzoic acid, and maleic anhydride as intermediates. In summary, this study provided an alternative route for the synthesis of non-crystalline metal co-oxide nanofibers.

Highly Efficient RGO-Supported Pd Catalyst for Low Temperature Hydrocarbon Oxidation

The work presents Pd-containing catalysts for practical application with enhanced low-temperature activity in the complete oxidation of volatile organic compounds (VOCs) using innovative combinations of reduced graphene oxide (RGO) and alumina. The catalysts were characterized by XRD, SEM, TEM, XPS, low-temperature N2-adsorption, and CO chemisorption. The tests on complete catalytic oxidation of different VOC (propane, butane, hexane, dimethyl ether, toluene, propylene) and CO were carried out. The reaction kinetics and the mechanism of the reaction of complete oxidation of toluene are being investigated in detail. The results show that the new catalyst design makes it able to completely oxidize the studied VOCs and CO at low temperatures (100–350 °C) with long-term stability. Using a variety of instrumental methods, it was established that for high activity and long-term stability, the optimal ratio Pd/PdO should be close to 1:1. The most probable mechanism of complete toluene oxidation is the mechanism of Langmuir–Hinshelwood. The high activity and the weak effect of water on the catalyst performance leads to further perspectives for the application of the currently developed approach for the preparation of large-scale monolithic catalytic systems for air pollution control.

Effect of the surface composition of MnOX-CeOX 3D-printed monolithic catalysts toward total oxidation of toluene.

Successful fabrication of Mn-based 3D-printed monoliths by stereolithography (SLA) is reported for the first-time in this work. The catalytic performances, as function of the surface composition, of the developed monoliths were evaluated by the total oxidation of toluene. The monolith with a surface composition of Mn0.7Ce0.3 showed the highest catalytic efficiency (98%) with a T90 value of 322 °C and acceptable catalytic stability after a second reaction cycle. By changing space velocity values, the T90 value can decrease to 311 °C. Microstructural and surface characterizations confirm the formation of Mn2O3 and Ce species on Mn sites and the homogeneous dispersion of Mn and Ce species on the surface of the 3D-printed monoliths. For comparison purposes, a single MnOX and CeOX monoliths were also synthesized and tested by toluene total oxidation, which confirms the cooperative effect between the oxygen storage capacity of Ce and the redox ability of Mn species observed in Mn0.7Ce0.3 monolith catalyst, giving rise to the highest catalytic activity. These results pointed out the promising catalytic properties of the developed Mn-based 3D-printed monolith catalysts for the total oxidation of volatile organic compounds at a low cost, which is an interesting alternative to mitigating atmospheric emissions.

Characterization, Sources, and Chemical Processes of Submicron Aerosols at a Mountain Site in Central China

AbstractA field campaign (29 May to 14 June 2018) was conducted at a mountain site in central China. The chemical composition of non‐refractory submicron particulate matter (NR‐PM1) and the particle number size distribution (PNSD) were measured, respectively. The mean NR‐PM1 mass concentration was 20.94 ± 10.14 μg m−3, among which organics (47%) was the most abundant component, followed by sulfate (37%), ammonium (11%), nitrate (4%), and chloride (1%). Notably, sulfate accounted for more than 70% of the secondary inorganic aerosols. Positive matrix factorization (PMF) analysis of the composition data resulted in three organic aerosol (OA) factors: hydrocarbon‐like OA (HOA), oxygenated OA I (OOA‐I), and oxygenated OA II (OOA‐II). The secondary organic aerosol (SOA) composed of the latter two factors (SOA: OOA‐I + OOA‐II) was dominant in OA (80.7%). The PMF analysis of the PNSD data yielded three factors: new particle formation related mode, growth mode, and accumulation mode, among which the last factor dominated both number and volume ratios. The sulfate formation was characterized by the sulfur oxidation ratio (SOR), heterogeneous sulfate production rate (Phet), and gaseous sulfuric acid concentration, representing secondary sulfate transformation, heterogeneous reactions, and gas phase reactions, respectively. The results showed that Phet was well correlated with both sulfate concentrations and SOR, especially during the polluted periods. Our study demonstrates that photochemically‐driven heterogeneous reactions contribute dominantly to the sulfate formation and SOA is formed predominantly by photochemical oxidation of volatile organic compounds under high temperatures and ultraviolet (UV) intensities, and NOX concentrations on Mt. Wudang during the campaign period.

Preparation of rare earth metal ions promoted MnOx@halloysite catalyst for highly efficient catalytic oxidation of toluene

Halloysite with nanotube structure is a potential functional support to prepare high-performance catalysts for the oxidation of volatile organic compounds (VOCs) at low temperatures. In this work, rare earth metal ions promoted MnOx@halloysite system were synthesized and demonstrated improved toluene oxidation. The obtained catalyst exhibits excellent catalytic performance, including toluene conversion efficiency (T90 = 232 °C), CO2 selectivity (100%), super long-term stability and water resistance under the condition of toluene concentration with 1000 ppm. It has been demonstrated that the La-promoted halloysite-supported MnOx catalyst increased the ratio of Mn3+ and the number of surface oxygen vacancies, facilitating the formation of active oxygen species and enhancing low-temperature catalytic activity. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy confirmed the intermediates generated during toluene oxidation. Toluene oxidation occurred via the benzyl alcohol → benzoate → anhydride reaction pathway over the obtained catalysts. This work provides a considerable experimental basis for understanding the catalytic performance and reaction mechanism of rare earth metal ions promoting the manganese oxides supported by clay minerals for toluene oxidation and paves the way for the development of high-performance catalysts toward toluene oxidation.

A Comparative Study of Ground-Gridded and Satellite-Derived Formaldehyde during Ozone Episodes in the Chinese Greater Bay Area

Formaldehyde (HCHO) plays an important role in atmospheric photochemical reactions. Comparative studies between ground-based and satellite observations are necessary to assess and promote the potential use of column HCHO as a proxy for surface HCHO and volatile organic compound (VOC) oxidation. Previous studies have only validated temporal and vertical profile variations at one point, with limited studies comparing horizontal spatial variations due to sparse monitoring sites. The photochemistry-active Chinese Greater Bay Area (GBA) is a typical megacity cluster as well as a large hotspot of HCHO globally, which recorded a high incidence of ozone (O3) pollution. Here, we conducted the first comparative study of ground-gridded (HCHOgg) and satellite-derived (HCHOsd) HCHO during typical O3 episodes in the GBA. Our results revealed a good correlation between HCHOgg and HCHOsd, with a correlation coefficient higher than 0.5. Cloud coverage and ground pixel sizes were found to be the dominant factors affecting the quality of HCHOsd and contributing to the varying satellite pixel density. Daily averages of HCHOsd effectively improved the HCHOsd accuracy, except in areas with low satellite pixel density. Furthermore, a new quality control procedure was established to improve HCHOsd from Level 2 to Level 3, which demonstrated good application performance in O3 sensitivity analysis. Our findings indicate that the correlation between satellite observations and surface air quality can be optimized by spatiotemporal averaging of hourly HCHOsd, given the advent of geostationary satellites. Considering the representative range of sampling sites in this comparative study, we recommend establishing VOC monitoring stations within a 50 km radius in the GBA to further analyze and control photochemical pollution.

TiN nanoparticles/OMS-2 nanorods/carbonized wood composites for simultaneous solar water evaporation and abatement of volatile organic compound from undrinkable water

Severe air pollution, water pollution, and climate change have led to an increasing shortage of clean water. Solar interface water evaporation is becoming important to obtain distilled water from undrinkable water such as seawater and contaminated water. However, the as-obtained distilled water usually contains excessive volatile organic compounds (VOCs), which are serious harmful to human health. In this article, a novel bi-functional material is prepared by depositing manganese oxide octahedral molecular sieve (OMS-2) nanorods on carbonized wood (CW), which can simultaneously realize solar water evaporation and VOCs abatement. OMS-2 nanorods synthesized at lower hydrothermal temperature possess higher oxygen vacancy defects, which can improve not only the solar absorption and solar water evaporation rate but also solar driven photothermo-catalytic activity for the oxidation of VOCs. Doping TiN nanoparticles into CW/OMS-2 can further enhance the solar water evaporation performances and VOCs removal efficiencies because of its excellent solar absorption ability, which can further increase the temperature of OMS-2 catalyst and accelerate the solar water evaporation and the toluene degradation. The as-designed bifunctional composites possess an outstanding water evaporation rate over 1.436 kg m−2 h−1 and a toluene removal efficiency of 92.96% under 2.5 sun irradiation, indicating exciting prospects for efficiently producing clean water from undrinkable water with VOCs.

Promoting multiple reactive oxygen species generation for deep oxidation of VOCs by UV/persulfate/permanganate

Advanced oxidation processes (AOPs) could effectively remove volatile organic compounds (VOCs) when coupled with wet scrubbing process. However, it still faces challenges in achieving deep oxidation of VOCs due to the limited production of reactive oxygen species (ROS). Herein, we present the utilization of permanganate (KMnO4) as a co-oxidant to enhance VOCs oxidation in UV/persulfate (PDS)/KMnO4 system. The removal efficiency of a targeted VOC, toluene, kept high at above 90% throughout the entire long-term reaction of 4 h, which was much higher than that of UV/PDS and UV/KMnO4. Notably, the in-situ formed manganese oxide (MnOx) acts as a catalyst in UV/MnOx and UV/MnOx/PDS, facilitating the generation of various ROS and thereby enhancing VOCs degradation. Electron paramagnetic resonance (EPR) and quenching experiments indicated that sulfate radical (SO4−), hydroxyl radical (HO), superoxide radical (O2−) and singlet oxygen (1O2) were the main ROS generated in the UV/PDS/KMnO4 system. The overall oxidation process can be divided into three stages: the UV/KMnO4-dominated stage, the UV/MnOx/PDS-dominated stage, and the UV/MnOx-dominated stage. Correspondingly, HO played a major role in toluene oxidation in the UV/KMnO4-dominated and UV/MnOx-dominated stages, with the contributions of 48% and 52%, respectively. Meanwhile, SO4− played a more significant role in the UV/MnOx/PDS-dominated stage, with a contribution of 59%. Three main reaction pathways involving electron abstraction, HO addition and benzene ring opening were proposed based on the intermediates identified by proton-transfer-reaction mass spectrometry (PTR-MS). This study provided a deep understanding of KMnO4 in improving the oxidation capacity of UV-based AOPs for VOCs degradation, emphasizing the importance of in-situ formed MnOx for promoting multiple ROS generation.

Strong ectopic adsorption on single cobalt site accelerates the direct catalytic oxidation of low concentration acetonitrile on CuO nanoparticles embedded in SAPO-34

It is usually inevitable for the usage of zeolite rotor concentrator to increase the level of volatile organic compounds (VOCs) concentration, which in turn enables the regenerative catalytic oxidation of VOCs with large gas flow rate to achieve autothermal operation. Herein, we present a new strategy for the preparation of autothermal oxidation catalyst (AOC) with strong ectopic adsorption ability for VOCs molecules by the on-site doping of single cobalt sites on CuO nanoclusters confined in zeolitic materials SAPO-34, which exhibits a strong enrichment ability for low concentration acetonitrile even at 300 °C. Meanwhile, a distinguished enhancement on the catalytic oxidation activities has also been achieved according to the formation of CoⅡ-oxo and/or Co-Ovac sites on CuO nanoparticles.

Deep oxidation of propane over PtIr/TiO2 bimetallic catalysts: Mechanistic investigation of promoting roles of Ir species

The catalytic deep oxidation of light alkanes is challenging due to the inert nature of the light alkanes. In this work, bimetallic PtIr/TiO2 catalysts with different Pt/Ir ratios were prepared and tested for the deep oxidation of propane. The reaction rate was much improved by the addition of Ir in the catalyst, and the highest turnover frequency (0.031 s−1 at 200 °C) was obtained on a catalyst with a Pt/Ir molar ratio of 3 (3Pt1Ir/TiO2) catalyst, which was 2-fold higher than that on the pristine Pt/TiO2 (0.014 s−1). The addition of Ir in the Pt/TiO2 resulted in stabilized metallic Pt0 under the reaction condition, as well as improved oxygen adsorption capacity, which promoted the adsorption/activation of propane and oxygen molecules. Moreover, detailed kinetics revealed that the reaction pathway switched from competitive adsorption of propane and oxygen on the Pt atoms to non-competitive adsorption of propane on Pt and oxygen on Ir, which thus provided new insights on the design of highly effective catalysts for deep oxidation of volatile organic compounds.

3D snowflake graphene modified α-MnO2 Catalyst: Enhancing the Low-Temperature catalytic activity for VOCs degradation

Manganese oxide is a promising catalyst for volatile organic compounds oxidation with merits of low cost, abundant valence states, diverse crystal forms and morphology, however, its catalytic activity at low temperature (<200 °C) is limited due to the poor dispersion and inferior electron transfer. To solve these problems, a novel 3D snowflake graphene is doped into α-MnO2 to fabricate rGO@α-MnO2 catalyst to enhance the catalytic activity at low temperature. Compared with α-MnO2, the rGO@α-MnO2 catalysts present larger specific surface area and pore volume, which facilitates the adequate contact reaction between active component and VOCs. The unique graphene electronic bridge promotes the electron transfer on rGO@α-MnO2, which results in higher concentration of surface defects and more surface adsorbed oxygen to the catalyst. The performance tests show that the catalyst doped with 4% 3D snowflake graphene has the best activity, which can achieve 90% toluene conversion at 155 °C, and even 100% toluene conversion with 80% CO2 selectivity at 200 °C. In particular, 4%rGO@α-MnO2 demonstrates excellent catalytic stability and moisture resistance, presenting similar catalytic performance after 5 cycles for both the dry and high relative humidity (RH = 85%) conditions. The excellent activity of 4%rGO@α-MnO2 can be attributed to the enhancement of toluene adsorption energy after graphene doping and the defect induced by the interface effect between graphene and (211) facet. In general, 3D snowflake graphene doping provides a convenient and cost-effective method to enhance the low-temperature activity of the α-MnO2 catalyst, presenting great application potential.

Tandem supported Pt and ZSM-5 catalyst with separated catalytic functions for promoting multicomponent VOCs oxidation

The painting and electronics industries simultaneously release aromatic compounds and chlorinated organics. The development of catalysts with synergistic control of these pollutants is of great significance to achieve air purification. However, developing active catalysts while maintaining good chlorine resistance remain a huge challenge due to the difficulty of the trade-off between the redox properties and acidity and the production of polychlorinated byproducts. Herein, we introduce a novel tandem PtSn/CeO2&Mn/ZSM-5 catalyst and investigate its catalytic performance for multicomponent volatile organic compounds (VOCs) oxidation. The two individual catalysts, PtSn/CeO2 and Mn/ZSM-5, were used to catalyze two distinct sequential reactions. PtSn/CeO2 catalyzed toluene oxidation to produce CO2 and H2O. Meanwhile, the introduction of SnOx favored the adsorption of trichloroethylene (TCE) molecules that prevented Pt sites from chlorine poisoning and possibly converted adsorbed TCE into intermediates, which were subsequently oxidized deeply by the nearby Mn/ZSM-5. This approach resulted in a remarkable oxidation efficiency for toluene (T90 = 296 °C) and TCE (T90 = 384 °C), with fewer unexpected toxic byproducts (chlorobenzene and 4-chlorotoluene). Furthermore, the tandem catalyst possessed excellent chlorine and water resistances. In conclusion, the above findings provide new insights into the design and/or syntheses of advanced catalysts for widespread VOCs pollution control.

Highly sensitive and selective detection of benzene, toluene, xylene, and formaldehyde using Au-coated SnO2 nanorod arrays for indoor air quality monitoring

We report the high performance of Au-coated SnO2 nanorod gas sensors for the detection of hazardous indoor volatile organic compounds (VOCs), such as benzene, toluene, xylene, and formaldehyde (BTXF) gases. Densely ordered SnO2 nanorod arrays were prepared via glancing angle deposition with an electron beam evaporator. The Au layer coating was used as a heterogeneous catalyst to promote the oxidation of VOCs, such as hydrocarbons. After optimizing the Au thickness, the sensor exhibited an excellent sensing response and a rapid response time of < 2.5 s for 10 ppm of BTXF gases. The maximum response was ∼662 for formaldehyde at 400 °C, ∼328 for toluene at 450 °C, ∼170 for xylene at 400 °C, and ∼139 for benzene at 500 °C, which are significantly higher than those of previously reported metal-oxide-semiconductor-based sensors. Each gas was selectively detected by integrating the sensor into a miniaturized gas chromatography (GC) system. The sensors detected ppb-level gas concentrations. Significantly, GC analysis revealed that four types of gases could be separately detected in a mixed gas within 5 min. Our study shows that Au-coated SnO2 nanorod gas sensors integrated with GC can be used as a facile indoor pollutant monitoring system.

Efficient selective combustion of n-butylamine on hierarchical Cu-Mn/SAPO-34 catalysts: The effect of mesoporosity and acidity

The efficient catalytic oxidation of nitrogen-containing volatile organic compounds remains a big challenge due to unmanaged production of harmful byproducts. Herein, a series of Cu-Mn modified hierarchical SAPO-34 zeolite catalysts with different pore structures were synthesized for n-butylamine oxidation. The physicochemical properties and catalytic performance of catalysts were investigated and analyzed in detail. Among them, CuMn/S-1 shows the highest activity (T90 = 279 °C, GHSV = 12,000 h−1), which is attributed to its higher porosity, higher surface acidity and superior reducibility. Meanwhile, it is found that the hierarchical structure and mesopore play an important role in improvement of N2 selectivity. Meanwhile, CuMn/S-1 also exhibits high stability and water resistance. The catalytic mechanism of n-butylamine on CuMn/SAPO-34 was investigated by in situ DRIFTS, showing that propanol, methanol and acetate are the main intermediates.

Variation and trend of nitrate radical reactivity towards volatile organic compounds in Beijing, China

Abstract. Nitrate radical (NO3) is an important nocturnal atmospheric oxidant in the troposphere that significantly affects the lifetime of pollutants emitted by anthropogenic and biogenic activities, especially volatile organic compounds (VOCs). Here, we used 1 year of VOC observation data obtained in urban Beijing in 2019 to look into the level, composition, and seasonal variation in NO3 reactivity (kNO3). We show that hourly kNO3 towards measured VOC varied widely from &lt; 10−4 to 0.083 s−1 with a campaign-average value (± standard deviation) of 0.0032 ± 0.0042 s−1. There was large seasonal difference in NO3 reactivity towards VOC with averaged values (± standard deviation) of 0.0024±0.0026 s−1 (spring), 0.0067±0.0066 s−1 (summer), 0.0042±0.0037 s−1 (autumn), and 0.0027±0.0028 s−1 (winter). Alkenes such as isoprene and styrene accounted for the majority. Isoprene was the dominant species in spring, summer, and autumn, accounting for 40.0 %, 77.2 %, and 43.2 %, respectively. Styrene only played a leading role in winter, with a percentage of 39.8 %. A sensitivity study shows monoterpenes, the species we did not measure, may account for a large fraction of kNO3. Based on the correlation between the calculated kNO3 and VOC concentrations in 2019, we established localized parameterization schemes for predicting the reactivity by only using a part of VOC species. The historically published VOC data were collected using the parameterization method to reconstruct the long-term kNO3 in Beijing. The lower kNO3 during 2014–2021 compared with that during 2005–2013 may be attributed to anthropogenic VOC emission reduction. Finally, we revealed that NO3 dominated the nocturnal VOC oxidation, with 83 % of the annual average in Beijing in 2019, which varied seasonally and was strongly regulated by the level of kNO3, nitrogen oxide, and ozone. Our results improve the understanding of nocturnal atmospheric oxidation in urban regions and contribute to our knowledge of nocturnal VOC oxidation and secondary organic pollution.

Differences between atomically-dispersed and particulate Pt supported catalysts on synergistic photothermocatalytic oxidation of VOCs from cooking oil fumes

The control of volatile organic compounds (VOCs) from cooking oil fumes via synergic photothermocatalytic oxidation not only saves energy, but also helps to reduce carbon emissions. Differences between the copper oxide−ceria (CC) supported atomically-dispersed (Pt1/CC) and particulate Pt (PtNPs/CC) on photothermocatalytic heptane oxidation were investigated. The conversion efficiency at 170 oC of heptane oxidation over the Pt1/CC catalyst was 55% higher than that over the PtNPs/CC catalyst. PtNPs/CC showed a larger capacity of heptane adsorption, but limited amounts of the adsorbed oxygen and active surface lattice oxygen species were difficult to completely oxidize the over-adsorbed heptane. Heptane and its intermediates gradually accumulated at the active sites, resulting in poor catalytic activity and stability. However, Pt1/CC possessed a strong electron donating ability due to its unique coordination unsaturated sites and electron structure, which was conducive to oxygen activation. This allowed rapid conversion of heptane and intermediates, accelerating oxidation of the adsorbed heptane to CO2 and H2O. The complete oxidation of 500 ppm heptane was basically achieved at 190 oC and an optical power density of 300 mW/cm2.

Rapid supplement of active oxygen by constructing Pt-Fe alloy structure to improve catalytic stability for furniture paints industry VOCs removal

To improve the air quality, volatile organic compounds (VOCs) elimination via a stable catalytic oxidation is important. The enhancement in the catalytic stability of toluene and iso-hexane removal is investigated by constructing the Pt-Fe alloy structure. The Pt-Fe alloy structure not only weakens the toluene adsorption, but also improves the lattice oxygen mobility. The Mars-van Krevelen mechanism is presented over the Pt1Fe1.5/M during toluene oxidation, instead of the initial Langmuir-Hinshelwood mechanism. For Pt1Fe1.5/M, the strong ability of O2 activation and the fast migration of lattice oxygen will provide sufficient surface lattice oxygen to ensure a continuous toluene oxidation. An excellent catalytic stability is detected over the catalysts with the high activity of lattice oxygen, which are accelerated by the weaker adsorption and higher temperature during iso-hexane oxidation. Generally, the crucial role of the replenishment speed of active oxygen species is clarified in a stable process of VOCs oxidation. It is valuable for the up-to-standard emission of VOCs from the furniture paints industry.

Copper-manganese oxide catalysts prepared by solution combustion synthesis for total oxidation of VOCs

A set of Cu-Mn oxides was prepared through the simple and effective solution combustion synthesis method by varying the relative amount of copper and manganese. The physico-chemical properties of the samples were investigated through complementary techniques such as N2 physisorption at − 196 °C, XRD, HR-TEM, Raman spectroscopy, temperature programmed analyses (H2-TPR, O2-TPD, and NH3-TPD), and XPS. The prepared catalysts were tested for the total oxidation of volatile organic compounds (ethylene, propylene, and toluene). The best performances, in terms of total VOC oxidation, were achieved with a copper content ranging from 15 at% to 45 at%. The catalytic test outcomes demonstrate the beneficial effect of acidic sites, oxygen mobility, and redox ability. In particular, ethylene oxidation is mainly favored by oxygen vacancies and redox properties, while propylene and toluene oxidation is mostly enhanced by acidic sites. All the catalysts prepared can totally oxidize the examined pollutants examined below 310 °C. Moreover, the binary oxides exhibit good catalytic stability over a time-on-stream of 7 h and low water vapor inhibition (5 vol% H2O in the gas stream).