The removal of NO and CO from CO2 industrial flue gases is achievable using Selective Catalytic Reduction (SCR) of NO by CO over transition-metal-based catalysts. In this work, CoCuAl mixed oxides were synthesized via the Layered Double Hydroxide (LDH) co-precipitation route with hydrothermal aging at temperatures ranging from 40 to 110 degrees C. The influence of hydrothermal aging temperature on the physicochemical properties was investigated using X-ray diffraction (XRD), N-2 Physisorption, Raman spectroscopy, H-2 Temperature-Programmed reduction (H-2-TPR), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Low to moderate hydrothermal treatment temperatures (40 degrees C-60 degrees C) promote enhanced crystallinity, cation incorporation, and carbonate intercalation within the LDH structure, whereas higher temperatures (> 80 degrees C) induce CuO phase segregation with less anion intercalation. After CO2 treatment at 400 degrees C, the mixed oxides prepared at low-to-moderate temperatures exhibited higher carbonate content and larger surface area (147-132 m(2).g(-1)). Pearson's Correlation analysis reveals the highest positive impact of carbonate content on NO reduction (R = 0.94), whereas CuO shows a strong negative relationship (R = -0.97) with N-2 formation at higher treatment temperatures (> 80 degrees C). These balanced properties, at low-to-moderate hydrothermal treatment temperatures, enhance CO oxidation (100% at 260 degrees C) and promote higher N-2 selectivity (51%-57% at 280 degrees C-300 degrees C).

Manganese-copper (Mn-Cu) mixed oxides are promising catalysts for abatement of incomplete combustion products from domestic wood burning, notably CO and Volatile Organic Compounds (VOCs). In this paper, the influence of the Mn/Cu molar ratio on structure, redox properties, and catalytic performances was investigated. Mixed oxides were synthesized by oxalate co-precipitation and calcined under air at 500 degrees C. Physicochemical characterization (XRD, Raman, N-2-physisorption, XPS, H-2-TPR) revealed strong Mn & horbar;Cu interaction. Catalytic tests for total oxidation of CO, toluene, and their mixture showed that copper-rich oxides, especially Cu1Mn0.25Ox, achieved the best performance at low temperature (T-50 = 49 degrees C and 230 degrees C for the oxidation of CO and toluene respectively). In alternating feeding, the presence of CO promotes the oxidation of toluene at low temperature, while an excess of Cu in the material ensures full CO2 selectivity. For mixed oxides, the linear correlation between Cu2+ -> Cu+ reducibility and T-50 for toluene oxidation in presence of CO demonstrates that the incorporation of Mn into Cu oxides enhances oxidation. Overall, tuning the Mn/Cu ratio enables efficient, selective, and simultaneous removal of CO and VOCs, providing a cost-effective solution for emission control from biomass combustion.

Cu6Al2 mixed oxides derived from layered double hydroxide precursors were synthesized by three methods: co-precipitation, microwave-assisted, and ultrasound-assisted methods. The mixed oxides obtained after calcination were studied by several techniques: XRD, N2-sorption, H2-TPR, and XPS. The catalytic materials were also tested as catalysts in the reaction of total oxidation of toluene, carbon monoxide, and the mixture of both. The physicochemical studies revealed a modification of the structural characteristics (surface area, morphology) as well as the reducibility of the formed mixed oxides. The solid prepared by microwave-assisted synthesis was the most active of the three reactions. Furthermore, relationships between the ratio of Cu/Al on the surface, the Oadsorbed/Obulk ratio of the CuAl mixed oxides surface, and the T50 in toluene oxidation in the presence of CO were demonstrated. These relationships suggest a Mars Van Krevelen mechanism for toluene total oxidation in the presence of CO for these three catalysts.

Toluene is a typical example of aromatic volatile organic compounds (VOCs), and its elimination makes a significant contribution to reducing air pollution. The treatment of gaseous effluents can be achieved by solvent absorption. This work aims to evaluate, for the first time, the removal of toluene from laboratory scale to industrial scale using a new heat and mass exchanger and to elucidate the absorption mechanism at molecular level. The vapor-liquid partition coefficient (K) and the absorption capacity were determined for three industrially available solvents, benzyl alcohol, acetic acid and propylene glycol, and their water mixtures. In addition, several absorption/desorption cycles were also used to regenerate the absorbent on a laboratory scale. An up to 488-fold lower K value was obtained for benzyl alcohol. The effect of water addition to the studied solvents on the partition coefficient confirmed a decreasing VOC absorption with increasing amount of water. However, the overall results show that the water/benzyl alcohol mixture (60:40 wt%) has interesting absorption capacities, close to some organic solvents, and therefore a high potential for the treatment of industrial air polluted with toluene. This phenomenon was further explained by COSMO-RS calculation and molecular dynamics. It was found that magnitude of interaction energy for absorbent-toluene (-63.3 kJ/mol) with 60 wt% water is slightly smaller than that of pure benzyl alcohol (-71.76 kJ/mol). Moreover, benzyl alcohol has the most negative Gibbs free energy of solvation value for toluene compared to other absorbents under study. The reason for the enhanced toluene absorption is the significant 7C-7C interaction between benzyl alcohol and toluene. The results obtained at different scales were in good agreement with each other.

The proposed study is devoted to highlighting the importance of mixed oxides preparation through the layered double hydroxide route for undesirable gas pollutants abatement. Different series of Cu/Al/Ce mixed oxides with similar or different stoichiometrics were prepared and compared for toluene and/or CO oxidation. Catalyst synthesis methods influence material properties and activity for oxidation reactions. The high activity for the oxidation reactions of mixed oxides derived from LDH is explained by the Cu/Ce synergy. The presence of CO in the CO/toluene mixture does not affect the total toluene oxidation, and the toluene does not affect the total oxidation of CO conversion at low temperatures. The most effective catalytic material (Cu6Al1.2Ce0.8) presents a long lifetime stability for total toluene oxidation and resistance to CO poisoning in mixtures.

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The aim of this work is to deposit gold nanoparticles on CoAl mixed oxide issued from layered double hydroxide (LDH) precursor by using the deposition precipitation (DP) method, which is applied with two modifications, labeled method (A) and method (B), in order to enhance the interaction of the HAuCl4 precursor with the support. Method (A) involves the hydrolysis of the HAuCl4 precursor after addition of the support, while in method (B), the gold precursor is hydrolyzed before adding the support. The two methods were applied using as support the CoAl mixed oxide and the LDH precursor. Samples were characterized by several physical chemical techniques and evaluated for ethanol total oxidation. Method (B) allowed the ethanol oxidation activity to be enhanced for the resulting Au/CoAlOx catalysts thanks to the high surface concentration of Co2+ and improved reducibility at low temperature. The presence of gold permits to minimize the formation of by-products, notably, methanol, allowed for a total oxidation of ethanol at lower temperature than the corresponding support.

A series of mixed oxides (Mn-Mg-Al) is prepared by coprecipitation via a hydrotalcite route with different manganese ratios. Structural, textural, and redox properties are studied by XRD, N-2-sorption, H-2-TPR, and XPS techniques. MnxMg6-xAl2-O mixed oxides (with 0 <= x <= 6) are tested in the total oxidation of ethanol and toluene, two probe molecules representing respectively oxygenated and aromatic VOCs. Catalysts with higher manganese contents have shown the best catalytic performance for the oxidation of both ethanol and toluene. The surface activity of the materials is mainly related to the presence of manganese species in three different oxidation states (+II, +III, and +IV) in the bulk and on the material's surface. Since high Mn-content catalysts showed similar physicochemical properties and catalytic activity, Mn4Mg2-O is selected as the optimal composition of these materials. Furthermore, its aging test is compared to that of noble metal-based commercial catalysts (Pd/?-Al2O3).

We are currently witnessing an increase in biogas production in the context of fossil fuel decline and the future circular economy. However, raw biogas contains undesirable compounds such as hydrogen sulfide, volatile organic compounds (VOCs) and carbon dioxide that should be removed to upgrade biogas to biomethane. Absorption is an effective method to capture undesirable compounds from biogas. In this work, we evaluated and compared the efficiency of hydrophobic deep eutectic solvents (DESs) based on fatty acids and conventional absorbents for the absorption of three major VOCs found as impurities in biogas (toluene, limonene and octamethylcyclotetrasiloxane). The vapor-liquid partition coefficient (K) of the VOCs in the studied solvents were determined using static headspace-gas chromatography. The effect of temperature and water content was assessed. Results show a decrease of K value in all solvents compared to water, hydrophobic DESs being the most effective solvents with an up to 20000-fold lower K value in the case of limonene. Interestingly, lowering temperature allows the conventional solvents to reach absorption efficiency close to DESs. Negative values of Delta G (from 6.95 to 22.89 kJ.mol(-1)) were obtained showing that all VOCs are favorably solubilized in absorbents. Obtained negative Delta H values (from 34.86 to 51.17 kJ.mol(-1)) indicate that the dissolution of VOCs is an exothermic process. For all studied absorbent the vertical bar Delta H vertical bar of VOC absorption is always higher than vertical bar T Delta S vertical bar, showing an enthalpically driven process. The obtained results indicate that efficient VOC absorption can be achieved by the proposed hydrophobic DESs and conventional solvent also providing easy recycling, and recovering process.

The understanding and quantification of the CO adsorption modes and strength on ultradispersed platinum catalysts supported on gamma-Al2O3 is of prominent importance for analytic and catalytic purposes. We report a multiscale experimental (AEIR, CO-TPD) and theoretical approach to provide vibrational properties, adsorption enthalpies, and desorption behaviors. First principles calculations on Pt-13(CO)(m)/gamma-Al2O3 and Pt(111) surface models (using various exchange-correlation functionals) provide a complementary view to experimental approches. Adsorption enthalpies computed with the RPBE functional appear to be the most compatible with the AEIR results. The occupation of top sites by CO dominates the behavior of supported Pt clusters. CO coverage reaches higher values in comparison to Pt(111) for similar operating conditions, and considerable cluster reconstruction is observed at high coverage. First principles calculations also confirm the IR assignment related to the various adsorption modes on top and bridge sites and demonstrate a particle size effect, lowering the frequency of linear adsorption at top sites with respect to extended Pt(111) surfaces. Finally, first principles-based microkinetic modeling of CO-TPD experiments shows that the adsorption strengths predicted on the small-size cluster by DFT are compatible with the experimental values. We discuss possible reasons for the experimental desorption pattern to be much broader than the computed pattern.

Contaminated methanol has very good potential for being utilized in formaldehyde production instead of its destructive abatement. The activities, selectivities and stabilities of cobalt–alumina and cobalt–alumina–ceria catalysts prepared by the hydrotalcite-method were investigated in formaldehyde production from emissions of methanol and methanethiol. Catalysts were thoroughly characterized and the relationships between the characterization results and the catalytic performances were drawn. The preparation method used led to the formation of spinel-type structures in the form of Co2AlO4 based on x-ray diffraction (XRD) and Raman spectroscopy. Ceria seems to be present as CeO2, even though interaction with alumina is possible in the fresh catalyst. The same structure is maintained after pelletizing the cobalt–alumina–ceria catalyst. The cobalt–alumina–ceria catalyst was slightly better in formaldehyde production, probably due to lower redox temperatures and higher amounts of acidity and basicity. Methanol conversion is negatively affected by the presence of methanethiol; however, formaldehyde yields are improved. The stability of the pelletized catalyst was promising based on a 16 h experiment. During the experiment, cobalt was oxidized (Co2+ → Co3+), cerium was reduced (Ce4+ → Ce3+) and sulfates were formed, especially on the outer surface of the pellet. These changes affected the low temperature performance of the catalyst; however, the formaldehyde yield was unchanged.

Oxidation processes, as part of the catalysis field, play a significant role in both industrial chemistry and environmental protection [...]

Hydrotalcite like compounds containing Co, Al and Ce are synthesized by co-precipitation method. The mixed oxides issued from calcination step, have been characterized and tested for the toluene total oxidation with various concentrations of toluene and oxygen. The toluene conversion curves have been modelled in this paper with eight models. The Mars Van Krevelen mechanism shows the best accordance with the experimental data. Moreover, the determination of the Co3O4-CeO2 interface as the active center has been performed with the experimental observations. The Co3O4 allows obtaining high catalytic activity, and the CeO2 permits increasing the reoxidation of the Co3O4 to perform a new catalytic cycle.

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs. This emission is generally accompanied by the presence of other products like CO, NOx or other VOC. In this paper, the development of catalysts for the total oxidation of CO and toluene mixture is performed. For this study, Mg6Al₂HT hydrotalcites precursors were synthesized by three different methods: co-precipitation, microwaves and ultrasound assisted method. Hydrotalcite precursors have been used in order to develop mixed oxides after calcination for the catalytic oxidation test. Hydrotalcite structure as well as the mixed oxides obtained after calcination was studied, by several techniques: XRD, TEM, DTA/TG, BET, N₂ sorption, H₂-TPR. The physico chemical studies revealed modification in the structural characteristics (surface area, porosity) as well as in reducibility properties of the formed mixed oxides. The nanocatalyst issued from microwaves synthesis was the most active in these studied reactions for the total oxidation of the mixture. Moreover, addition of CO on the reaction mixture allows obtaining a beneficial effect on the toluene oxidation.

VOC and CO constitute the principal emission during cold-start of vehicles. In order to decrease this emission at low temperature, this study focuses on the development of new catalysts: MgAlCe mixed oxides issued from the calcination of hydrotalcite precursors. Addition of cerium on the MgAl solid increase the reducibility of catalysts inducing a better catalytic reactivity for the CO and toluene total oxidation. Moreover, toluene oxidation is facilitated at low temperature due to a beneficial effect of CO in the reaction mixture.

Hydrotalcite like compounds containing Co, Al and Ce were synthesized by co-precipitation. The mixed oxides obtained after calcination were characterized by several techniques: XRD, BET, H-2-TPR and XPS. Activities of mixed oxides were evaluated in toluene total oxidation in presence or in absence of carbon monoxide. The benzene, benzyl alcohol and benzaldehyde are principal by-products observed during toluene oxidation in presence of CoAl(Ce) mixed oxides. Moreover, presence of carbon monoxide improves toluene total oxidation over CoAlCe mixed oxides. Stability of the two best catalytic materials has been tested in the two conditions and show no deactivation.