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

Reutilization of Cr-Y zeolite obtained by biosorption in the catalytic oxidation of volatile organic compounds

Space‐confined catalysis can help create unique nanoscale chemical environments partitioned from the surrounding bulk space and has become a feasible strategy for designing high‐efficiency catalysts for various reactions. Confinement effects can affect both the reacting molecules and confined metal/metal‐oxide nanoparticles. This review mainly documents the progress in the design and applications of confined catalysts used in environmental catalysis (selective catalytic reduction (SCR) of NOx with ammonia, catalytic oxidation of CO and volatile organic compounds (VOCs), photocatalytic oxidation of VOCs, and photocatalytic CO2 reduction). Throughout the review, the impact of confinement effects on the activity, selectivity, and stability of catalysts is emphasised. Materials such as carbon nanotubes (CNTs), titanate nanotubes (TNTs), zeolites, mesoporous TiO2, and metal−organic frameworks (MOFs) are common confined hosts. In the NH3‐SCR reaction, confined catalysts, which are non‐noble metals confined in titanate/carbon nanotubes catalysts, have been widely studied. The protection offered by the confined space can shield metal/metal‐oxide nanoparticles from toxic components (e. g., SO2, alkali metals, and heavy metals), while improving the activity of the catalysts. In the field of catalytic oxidation of CO and VOCs, noble metals are always confined in the host without aggregating, sintering, or poisoning and show enhanced activity. In the photocatalytic oxidation of VOCs and photocatalytic reduction of CO2, the application of confined catalysts can prolong the contact time of reactants and improve visible‐light absorption and electron transfer, leading to better catalytic performance.

General study of catalytic oxidation of various VOCs over La0.8Sr0.2MnO3+x perovskite catalyst—influence of mixture

The role of lattice oxygen on the activity of manganese oxides towards the oxidation of volatile organic compounds

Catalytic oxidation of toluene and m-xylene by activated carbon fiber impregnated with transition metals

Developing efficient and stable non-noble metal catalysts for the catalytic oxidation of volatile organic compounds (VOCs) has always been key for controlling air pollution.

With the rapid development of urbanization and industrialization, environmental pollution has become more severe. Volatile organic compounds (VOCs) could be originated from the following sources: domestic, mobile and industrial sources. As important air pollutants, VOCs could cause serious harm to the environment and human health. Therefore, removing VOCs has become a priority research direction of ecological issues. Among the many elimination methods, catalytic oxidation approaches are among the most effective and economical methods which can transform VOCs into CO2 and H2O. MnOx catalysts are among the most active catalysts, which can be further modified by different cations such as Cu2+, Co2+, Cr3+, Ni2+ and Ce4+ to form mixed oxides to improve the catalytic oxidation of VOCs activity. Moreover, MnOx can be loaded on the carrier, improving the redox and oxygen storage capacity and improving its stability and activity. This review explores the structure, preparation and oxidation state of Mn-based catalysts.

ABSTRACTA photocatalytic paint based on carbon‐doped titanium dioxide as a pigment replacement was tested for the oxidation of volatile organic compounds (VOCs) under visible‐light illumination in indoor environments. The photocatalytic paint was characterized by X‐ray photoelectron spectroscopy, scanning and transmission electron microscopy, and diffuse reflectance and transmittance spectral measurements. The effects of environmental conditions, including inlet concentration, relative humidity (RH), incident radiation flux, and residence time, on the degradation of toluene, an aromatic VOC, were investigated. At certain operating conditions, toluene degradation efficiency increased, from 38% to 61%, with the rise in the incident radiation flux from 6.86 to 42.34 W/m2, while it declined with increasing RH from 10% to 70%. A one‐directional heterogeneous model predicted these trends, highlighting the opposing effects of incident radiation flux and humidity on toluene oxidation kinetics. In binary mixtures of toluene and acetaldehyde, representing aromatic and aliphatic VOCs, respectively, the presence of acetaldehyde had a negligible effect on toluene conversion, whereas acetaldehyde degradation was significantly reduced—by 36% and 65%—when co‐fed with 3.5 and 6.5 ppmv of toluene, respectively, indicating a strong competitive effect between pollutants. This study highlights the benefit of using photocatalytic paint for indoor air decontamination and provides new insights into its performance under more realistic environmental conditions, particularly in the presence of mixed VOCs.

Three‐dimensional modeling studies have been performed to investigate the short‐timescale photochemical generation of carbon monoxide (CO) on a regional basis in two very distinct areas of the United States: New England (mixed biogenic and anthropogenic influence) and the South Coast Air Basin (SoCAB, dominated by anthropogenic influence) of California. For the New England study, the Caltech Atmospheric Chemistry Mechanism (CACM) was incorporated into the Community Multiscale Air Quality model and applied to 3–4 August 2004. For the SoCAB, CACM was applied to 8–9 September 1993 using the California Institute of Technology three‐dimensional regional atmospheric model. Results indicate that in each location, on a relative scale, the photochemical generation of CO is responsible for less than 10% (3–9% for the eastern United States and approximately 1% in the SoCAB) of the total simulated mixing ratio for the respective dates based on domain‐wide, calendar‐based 24‐hour averages. In the eastern United States, simulations indicate that isoprene is the major volatile organic compound (VOC) source for CO and that VOC oxidation can lead to up to approximately 20 parts per billion by volume (ppb) of CO in New England. In the SoCAB, anthropogenic short‐chain alkenes lead to the greatest amount of photochemical CO generation; VOC oxidation in its entirety can lead to up to approximately 45 ppb of photochemically generated CO in the SoCAB. Therefore studies on the regional scale that use CO as a marker of primary combustion emissions may overestimate the importance of primary emissions, depending on location and time.

VOCs catalytic removal over hierarchical porous zeolite NaY supporting Pt or Pd nanoparticles

Cobalt catalysts supported on metal oxides (CeO2, TiO2 and Al2O3) were prepared to investigate the effects of the support for the complete oxidation of propene, a model volatile organic compound of hydrocarbon type. The presence of ethylenediamine during the preparation of Co/metal oxides was also studied and compared with a conventionally prepared catalyst. Addition of an aqueous solution of ethylenediamine to a cobalt nitrate solution had a promotional effect on the catalytic performance of the solids. More activated oxygen species are available for propene oxidation due to the highest cobalt dispersion obtained when ethylenediamine is used during the synthesis. But the activation of oxygen species and the reducibility of the catalyst depend on the support used. The Co/CeO2 catalysts, synthesized by two protocols, presented the highest propene oxidation activity from the series due to the highest synergistic coupling of the redox properties of CeO2 and Co3O4.

Based on previous Computational Fluid Dynamics (CFD) design results, an 11 channel microreactor of dimensions (0.5 mm × 0.5 mm × 100 mm) (width × depth × length) and optimal manifold geometry was fabricated, coated with a newly-developed Au/SBA-15 catalyst and then integrated in an experimental rig specifically built for this research. Propane (as model volatile organic compound) oxidation experiments were conducted at three different flow velocities, 12.5, 15.4 and 17.5 m/min, respectively, at six temperatures, 150, 200, 225, 250, 275, and 300 °C, respectively. The catalyst was prepared by one-pot sol-gel synthesis of SBA-15 with MPTMS (3-mercaptopropyl-trimethoxy-silane) before loading with HAuCl4 gold precursor and then characterized by SEM/EDX, TEM and wide angle XRD. A novel catalyst coating technique was developed, using airbrush (0.3 nozzle) to spray a catalyst slurry into the microchannels that produced a thin, firm and uniform layer of Au/SBA-15 catalyst coating inside the microreactor. The experimental measurements revealed that propane conversion increased as the flow feed rates decreased and increased with increasing temperatures in the reactor. For the built microreactor and for the flows and temperatures set, the combustion of propane was possible with measurable conversions and reasonable reactor stability, the performance of the catalyst appeared to be central to the satisfactory operation of the reactor.

Inter-comparisons of VOC oxidation mechanisms based on box model: A focus on OH reactivity

Influence of the exchanged cation in Pd/BEA and Pd/FAU zeolites for catalytic oxidation of VOCs

Photocatalytic oxidation of volatile organic compounds for indoor environment applications: Three different scaled setups