Special Issue "Catalysis for the Removal of Gas-Phase Pollutants"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Environmental Catalysis".

Deadline for manuscript submissions: 30 November 2019.

Special Issue Editor

Dr. Antonio Eduardo Palomares
E-Mail Website
Guest Editor
Instituto de Tecnología Química (ITQ), Universitat Politècnica València-CSIC, Valencia, Spain
Interests: Environmental catalysis, environmental technology, air pollution (catalytic removal of NOx, Sox, and Cl–COVs) and water pollution (catalytic removal of nitrates and bromates)

Special Issue Information

Dear Colleagues,

As you know, air pollution is one of the most concerning world issues. According to the World Health Organization (WHO), more than 80% of people living in urban areas that monitor air pollution are exposed to air pollution levels that exceed the WHO recommended limits. While all regions of the world are affected, populations in low- and middle-income countries are the most impacted, and it is estimated that air pollution could cause 6 to 9 million premature deaths per year by 2060. In 2015, WHO and the Organisation for Economic Co-operation and Development (OECD) calculated that the economic cost of premature death and disability from air pollution in Europe is close to USD 1.6 trillion and will reach 1% of the global gross domestic product (GDP) by 2060.

 Although the emissions of the main pollutants have decreased in the last years in developed countries as a result of more stringent emission limits, the global production of air pollutants has increased because of the emissions of newly industrialized countries. New technologies that contribute to the reduction of these emissions are a matter of urgent necessity. In this context, catalysis is playing an important role in the control of pollutants, and many of the technologies used for air pollutants abatement are based on the use of different catalysts. It is expected that the discovery and preparation of new materials and the understanding of the catalytic reaction mechanisms will result in the development of new catalytic technologies for the control of the gas-phase pollutants.

Submissions to this Special Issue on “Catalysis for the Removal of Gas-Phase Pollutants” are welcome in the form of original research papers or short reviews that reflect the state of research on this important subject in the following topics: catalytic control from stationary and mobile sources, catalysis for the reduction of greenhouse gases, catalytic abatement of NOx, VOCs, SOX, Cl-compounds, COx, ozone decomposition, household air pollution, catalytic oxidation  and catalytic reduction of gas-phase pollutants, mechanisms for these reactions, and  catalyst characterization and stability .

Dr. Antonio Eduardo Palomares
Guest Editor

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Keywords

  • NOx
  • VOCs
  • SOx
  • Cl-compounds
  • ozone decomposition
  • COx
  • catalytic oxidation
  • catalytic reduction
  • reaction mechanism
  • catalyst characterization

Published Papers (12 papers)

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Research

Open AccessArticle
Cobalt Oxide Catalysts in the Form of Thin Films Prepared by Magnetron Sputtering on Stainless-Steel Meshes: Performance in Ethanol Oxidation
Catalysts 2019, 9(10), 806; https://doi.org/10.3390/catal9100806 - 26 Sep 2019
Abstract
Catalytic total oxidation is an effective procedure to minimize emissions of volatile organic compounds (VOC) emissions in industrial gases. Catalysts in the form of meshes are remarkable as they minimize the internal diffusion of reactants during the reaction as well as the need [...] Read more.
Catalytic total oxidation is an effective procedure to minimize emissions of volatile organic compounds (VOC) emissions in industrial gases. Catalysts in the form of meshes are remarkable as they minimize the internal diffusion of reactants during the reaction as well as the need of expensive active components. In this paper, various conditions of radio frequency magnetron sputtering of cobalt on stainless-steel meshes was applied during catalyst preparation. Properties of the supported Co3O4 catalysts were characterized by SEM, XRD, temperature programmed reduction (H2-TPR), FTIR, XPS, and Raman spectroscopy. Catalytic activity was examined in deep oxidation of ethanol chosen as a model VOC. Performance of the catalysts depended on the amount of Co3O4 deposited on the supporting meshes. According to specific activities (the amounts of ethanol converted per unit weight of Co3O4), smaller Co3O4 particle size led to increased catalytic activity. The catalyst prepared by sputtering in an Ar+O2 atmosphere without calcination showed the highest catalytic activity, which decreased after calcination due to enlargement of Co3O4 particles. However, specific activity of this catalyst was more than 20 times higher than that of pelletized commercial Co3O4 catalyst used for comparison. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
Effect of Copper Precursors on the Activity and Hydrothermal Stability of CuII−SSZ−13 NH3−SCR Catalysts
Catalysts 2019, 9(9), 781; https://doi.org/10.3390/catal9090781 - 19 Sep 2019
Abstract
A series of CuII−SSZ−13 catalysts are prepared by in-situ hydrothermal method using different copper precursors (CuII(NO3)2, CuIISO4, CuIICl2) for selective catalytic reduction of NO by NH3 [...] Read more.
A series of CuII−SSZ−13 catalysts are prepared by in-situ hydrothermal method using different copper precursors (CuII(NO3)2, CuIISO4, CuIICl2) for selective catalytic reduction of NO by NH3 in a simulated diesel vehicle exhaust. The catalysts were characterized by X−ray diffraction (XRD), scanning electron microscope (SEM), X−ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, hydrogen-temperature-programmed reduction (H2−TPR), ammonia temperature-programmed desorption (NH3−TPD), and 27Al and 29Si solid state Nuclear Magnetic Resonance (NMR). The CuII−SSZ−13 catalyst prepared by CuII(NO3)2 shows excellent catalytic activity and hydrothermal stability. The NO conversion of CuII−SSZ−13 catalyst prepared by CuII(NO3)2 reaches 90% at 180 °C and can remain above 90% at a wide temperature range of 180–700 °C. After aging treatment at 800 °C for 20 h, the CuII−SSZ−13 catalyst prepared by CuII(NO3)2 still exhibits above 90% NO conversion under a temperature range of 240–600 °C. The distribution of Cu species and the Si/Al ratios in the framework of the synthesized CuII−SSZ−13 catalysts, which determine the catalytic activity and the hydrothermal stability of the catalysts, are dependent on the adsorption capacity of anions to the cation during the crystallization process due to the so called Hofmeister anion effects, the NO3 ion has the strongest adsorption capacity among the three kinds of anions (NO3, Cl, and SO42−), followed by Cl and SO42– ions. Therefore, the CuII−SSZ−13 catalyst prepared by CuII(NO3)2 possess the best catalytic ability and hydrothermal stability. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
Recycling of Gas Phase Residual Dichloromethane by Hydrodechlorination: Regeneration of Deactivated Pd/C Catalysts
Catalysts 2019, 9(9), 733; https://doi.org/10.3390/catal9090733 - 29 Aug 2019
Abstract
Dichloromethane (DCM) is an important pollutant with very harmful effects on human health and the environment. Catalytic hydrodechlorination (HDC) is an environmentally friendly technology for its removal from gas streams; it avoids the formation of hazardous pollutants like dioxins and phosgene (produced by [...] Read more.
Dichloromethane (DCM) is an important pollutant with very harmful effects on human health and the environment. Catalytic hydrodechlorination (HDC) is an environmentally friendly technology for its removal from gas streams; it avoids the formation of hazardous pollutants like dioxins and phosgene (produced by other techniques), and the products obtained can be reused in other industries. When compared to other precious metals, Pd/C catalyst exhibited a better catalytic activity. However, the catalyst showed a significant deactivation during the reaction. In this study, the oxidation state and particle size of Pd was monitored with time on stream in order to elucidate the transformations that the catalyst undergoes during HDC. The deactivation can be ascribed to the formation of a new PdCx phase during the first hour of reaction. Carbon atoms incorporated to Pd lattice come from (chloro)-hydrocarbons adsorbed in the metallic species, whose transformation is promoted by the HCl originating in the reaction. Nevertheless, the catalyst was regenerated by air flow treatment at 250 °C, recovering the catalyst more than 80% of initial DCM conversion. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
High Performance of Mn-Doped MgAlOx Mixed Oxides for Low Temperature NOx Storage and Release
Catalysts 2019, 9(8), 677; https://doi.org/10.3390/catal9080677 - 09 Aug 2019
Abstract
NOx storage-reduction (NSR) is a potential approach for the effective removal of NOx under the lean conditions in lean-burn engines. Herein, manganese-doped mixed oxides (Mn/MgAlOx) with high performance for low temperature NOx storage and release were derived from [...] Read more.
NOx storage-reduction (NSR) is a potential approach for the effective removal of NOx under the lean conditions in lean-burn engines. Herein, manganese-doped mixed oxides (Mn/MgAlOx) with high performance for low temperature NOx storage and release were derived from hydrotalcites precursors prepared by a facile coprecipitation method. The catalysts were characterized by X-ray diffraction (XRD), SEM, N2 adsorption-desorption, H2-TPR, FT-IR, and X-ray photoelectron spectroscopy (XPS) techniques. The Mn-doped MgAlOx catalysts exhibited high NOx storage capacity (NSC) at low temperature range (150–300 °C), which was related to their increased surface area, improved reducibility and higher surface Mn3+ content. The largest NSC measured, 426 μmol/g, was observed for NOx adsorption at 200 °C on Mn15 catalyst (the sample containing 15 wt% of Mn). The in situ DRIFTS spectra of NOx adsorption proved that the Mn-doped hydrotalcite catalysts are preferred for low temperature NOx storage and release due to their ability to store NOx mainly in the form of thermally labile nitrites. NSR cycling tests revealed the NOx removal rate of Mn15 sample can reach above 70% within the wide temperature range of 150–250 °C. Besides, the influence of CO2, soot, H2O and SO2 on NOx storage performance of Mn15 catalyst was also studied. In all, owning to their excellent NOx storage capacity, NSR cycling performance, and resistance to CO2, soot, SO2 and H2O, the Mn-doped MgAlOx NSR catalysts have broad application prospects in NOx control at low temperatures. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
A Novel Porous Ceramic Membrane Supported Monolithic Cu-Doped Mn–Ce Catalysts for Benzene Combustion
Catalysts 2019, 9(8), 652; https://doi.org/10.3390/catal9080652 - 30 Jul 2019
Abstract
Porous ceramic membranes (PCMs) are considered as an efficient hot gas filtration material in industrial systems. Functionalization of the PCMs with high-efficiency catalysts for the abatement of volatile organic compounds (VOCs) during dust elimination is a promising way to purify the industrial exhaust [...] Read more.
Porous ceramic membranes (PCMs) are considered as an efficient hot gas filtration material in industrial systems. Functionalization of the PCMs with high-efficiency catalysts for the abatement of volatile organic compounds (VOCs) during dust elimination is a promising way to purify the industrial exhaust gases. In this work, we prepared PCMs (porosity: 70%) in a facile sintering process and integrated Cu-doped Mn–Ce oxides into the PCMs as monolithic catalysts by the sol–gel method for benzene oxidation. Through this method, the catalysts are dispersed evenly throughout the PCMs with excellent adhesion, and the catalytic PCMs provided more active sites for the reactant gases during the catalytic reaction process compared to the powder catalysts. The physicochemical properties of PCMs and catalytic PCMs were characterized systematically, and the catalytic activities were measured in total oxidation of benzene. As a result, all the prepared catalytic PCMs exhibited high catalytic activity for benzene oxidation. Significantly, the monolithic catalyst of Cu0.2Mn0.6Ce0.2/PCMs obtained the lowest temperature for benzene conversion efficiency of 90% (T90) at 212 °C with a high gaseous hourly space velocity of 5000 h−1 and showed strong resistance to high humidity (90 vol.%, 20 °C) with long-term stability in continuous benzene stream, which is caused by abundant active adsorbed oxygen, more surficial oxygen vacancy, and lower-temperature reducibility. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
Effect of Small Molecular Organic Acids on the Structure and Catalytic Performance of Sol–Gel Prepared Cobalt Cerium Oxides towards Toluene Combustion
Catalysts 2019, 9(5), 483; https://doi.org/10.3390/catal9050483 - 24 May 2019
Abstract
Cobalt cerium oxide catalysts with small molecular organic acids (SOAs) as chelating agents were prepared via the sol–gel method and investigated for the complete oxidation of toluene. Four kinds of natural SOAs, i.e. malic acid (MA), citric acid (CA), glycolic acid (GA), and [...] Read more.
Cobalt cerium oxide catalysts with small molecular organic acids (SOAs) as chelating agents were prepared via the sol–gel method and investigated for the complete oxidation of toluene. Four kinds of natural SOAs, i.e. malic acid (MA), citric acid (CA), glycolic acid (GA), and tartaric acid (TA), were selected. The effect of organic acids on the composition, structure, morphology and catalytic performance of metal oxides is discussed in details. The cobalt cerium oxides catalysts were characterized by various techniques, including TG–DSC, XRD, SEM–EDS, N2–adsorption and desorption, XPS, and H2–TPR analyses. The results show that the nature of organic acids influenced the hydrolysis, condensation and calcination processes, as well as strongly affected the textural and physicochemical properties of the metal oxides synthesized. The best catalytic activity was obtained with the CoCe–MA catalyst, and the toluene conversion reached 90% at 242 °C. This outstanding catalytic activity could be related to its textural, redox properties and unique surface compositions and oxidation states. In addition, the CoCe–MA catalyst also showed excellent stability in long–time activity test. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
Self-Templating Synthesis of 3D Hierarchical NiCo2O4@NiO Nanocage from Hydrotalcites for Toluene Oxidation
Catalysts 2019, 9(4), 352; https://doi.org/10.3390/catal9040352 - 11 Apr 2019
Abstract
Rational design LDHs (layered double hydroxides) with 3D hierarchical hollow structures have generated widespread interest for catalytic oxidation due to the high complexity in shell architecture and composition. Herein, we reported a handy two-step method to construct a 3D hierarchical NiCo2O [...] Read more.
Rational design LDHs (layered double hydroxides) with 3D hierarchical hollow structures have generated widespread interest for catalytic oxidation due to the high complexity in shell architecture and composition. Herein, we reported a handy two-step method to construct a 3D hierarchical NiCo2O4/NiO nanocage. This synthetic strategy contains a partial in situ transformation of ZIF-67 (zeolitic imidazolate framework-67) into Co-NiLDH yolk-shelled structures following ethanol etching, and a structure-preserved transformation from [email protected] to a biphase nanocage following calcination. CoNi-yh-T (varied reaction time and calcination temperature) nanocages were investigated systematically by Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), H2- temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD) and studied for toluene oxidation. The CoNi-6h-350 sample showed much higher activity with 90% toluene conversion (T90) at 229 °C at a high space velocity (SV = 60,000 mL g−1 h−1) than other catalysts (T90 >240 °C). Abundant surface high valence Co ions caused by the novel hierarchical nanostructures, together with adsorbed oxygen species and abundant medium-strength surface acid sites, played a key role for catalytic activities. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
Selective Catalytic Reduction of Nitric Oxide with Propylene over Fe/Beta Catalysts Under Lean-Burn Conditions
Catalysts 2019, 9(2), 205; https://doi.org/10.3390/catal9020205 - 23 Feb 2019
Abstract
Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with propylene (C3H6-SCR) under lean-burn conditions, which were prepared by liquid ion-exchange (LIE), solid-state ion-exchange (SIE), and incipient wet-impregnation (IWI) methods. The iron species on Fe/Beta were [...] Read more.
Fe/Beta catalysts were used for the selective catalytic reduction of nitric oxide with propylene (C3H6-SCR) under lean-burn conditions, which were prepared by liquid ion-exchange (LIE), solid-state ion-exchange (SIE), and incipient wet-impregnation (IWI) methods. The iron species on Fe/Beta were characterized and identified by a combination of several characterization techniques. The results showed preparation methods had a significant influence on the composition and distribution of iron species, LIE method inclined to produce more isolated Fe3+ ions at ion-exchanged sites than IWI and SIE method. C3H6-SCR activity tests demonstrated Fe/Beta(LIE) possessed remarkable catalytic activity and N2 selectivity at temperature 300–450 °C. Kinetic studies of C3H6-SCR reaction suggested that isolated Fe3+ species were more active for NO reduction, whereas Fe2O3 nanoparticles enhanced the hydrocarbon combustion in excess of oxygen. According to the results of in situ DRIFTS, more isolated Fe3+ sites on Fe/Beta(LIE) would promote the formation of the key intermediates, i.e., NO2 adspecies and formate species, then led to the superior C3H6-SCR activity. The slight decrease of SCR activity after hydrothermal aging of Fe/Beta(LIE) catalyst might be due to the migration of isolated Fe3+ ions into oligomeric clusters and/or Fe2O3 nanoparticles. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
Bimetallic AgFe Systems on Mordenite: Effect of Cation Deposition Order in the NO Reduction with C3H6/CO
Catalysts 2019, 9(1), 58; https://doi.org/10.3390/catal9010058 - 08 Jan 2019
Cited by 1
Abstract
Mono- and bimetallic systems of Ag, Fe, and Ag–Fe exchanged in sodium mordenite zeolite were studied in the reaction of NO reduction. The transition metal cations Ag and Fe were introduced by ion exchange method both at room temperature and 60 °C; modifying [...] Read more.
Mono- and bimetallic systems of Ag, Fe, and Ag–Fe exchanged in sodium mordenite zeolite were studied in the reaction of NO reduction. The transition metal cations Ag and Fe were introduced by ion exchange method both at room temperature and 60 °C; modifying the order of component deposition in bimetallic systems. These materials were characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), ultraviolet-visible spectroscopy (UV-Vis), X-Ray photoelectron Spectroscopy (XPS) and High-resolution transmission electron microscopy (HR-TEM). The XPS and UV–Vis spectra of bimetallic samples revealed that under certain preparation conditions Ag+ is reduced with the participation of the Fe2+/Fe3+ ions transition and is present in the form of a Ag reduced state in different proportions of Agm clusters and Ag0 NPs, influenced by the cation deposition order. The catalytic results in the NO reduction reaction using C3H6/CO under an oxidizing atmosphere show also that the order of exchange of Ag and Fe cations in mordenite has a strong effect on catalytic active sites for the reduction of NO. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
High Selectivity and Stability of Nickel Catalysts for CO2 Methanation: Support Effects
Catalysts 2019, 9(1), 24; https://doi.org/10.3390/catal9010024 - 30 Dec 2018
Cited by 2
Abstract
In this work, we present an investigation concerning the evaluation of the catalytic properties of Ni nanoparticles supported on ZrO2, SiO2, and MgAl2O4 for CO2 hydrogenation to methane. The supports were prepared by coprecipitation and [...] Read more.
In this work, we present an investigation concerning the evaluation of the catalytic properties of Ni nanoparticles supported on ZrO2, SiO2, and MgAl2O4 for CO2 hydrogenation to methane. The supports were prepared by coprecipitation and sol-gel, while Ni was incorporated by impregnation (10–20 wt %). X-ray diffraction, nitrogen physisorption, temperature-programmed reduction, H2 pulse chemisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were the main characterization techniques employed. A laboratory fixed-bed reactor operated at atmospheric pressure, a temperature range of 350–500 °C, and a stoichiometric H2/CO2 molar ratio was used for catalyst evaluation. The most outstanding results were obtained with nickel catalysts supported on ZrO2 with CO2 conversions of close to 60%, and selectivity to methane formation was 100% on a dry basis, with high stability after 250 h of reaction time. The majority presence of tetragonal zirconia, as well as the strong Ni–ZrO2 interaction, were responsible for the high catalytic performance of the Ni/ZrO2 catalysts. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
AuPd/3DOM TiO2 Catalysts: Good Activity and Stability for the Oxidation of Trichloroethylene
Catalysts 2018, 8(12), 666; https://doi.org/10.3390/catal8120666 - 18 Dec 2018
Abstract
Three-dimensionally ordered macroporous (3DOM) TiO2-supported AuPd alloy (xAuyPd/3DOM TiO2 (x = 0.87–0.91 wt%; y = 0.51–1.86)) catalysts for trichloroethylene (TCE) oxidation were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods. The as-prepared materials [...] Read more.
Three-dimensionally ordered macroporous (3DOM) TiO2-supported AuPd alloy (xAuyPd/3DOM TiO2 (x = 0.87–0.91 wt%; y = 0.51–1.86)) catalysts for trichloroethylene (TCE) oxidation were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods. The as-prepared materials possessed a good-quality 3DOM structure and a surface area of 49–53 m2/g. The noble metal nanoparticles (NPs) with a size of 3–4 nm were uniformly dispersed on the surface of 3DOM TiO2. The 0.91Au0.51Pd/3DOM TiO2 sample showed the highest catalytic activity with the temperature at a TCE conversion of 90% being 400 °C at a space velocity of 20,000 mL/(g h). Furthermore, the 0.91Au0.51Pd/3DOM TiO2 sample possessed better catalytic stability and moisture-resistant ability than the supported Au or Pd sample. The partial deactivation induced by H2O introduction of 0.91Au0.51Pd/3DOM TiO2 was reversible, while that induced by CO2 addition was irreversible. No significant influence on TCE conversion was observed after introduction of 100 ppm HCl to the reaction system over 0.91Au0.51Pd/3DOM TiO2. The lowest apparent activation energy (51.7 kJ/mol) was obtained over the 0.91Au0.51Pd/3DOM TiO2 sample. The doping of Au to Pd changed the TCE oxidation pathway, thus reducing formation of perchloroethylene. It is concluded that the high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between AuPd NPs and 3DOM TiO2 as well as more amount of strong acid sites were responsible for the good catalytic activity, stability, and water- and HCl-resistant ability of 0.91Au0.51Pd/3DOM TiO2. We believe that 0.91Au0.51Pd/3DOM TiO2 may be a promising catalyst for the oxidative elimination of chlorine-containing volatile organics. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Open AccessArticle
Photocatalytic Oxidation of Toluene on Fluorine Doped TiO2/SiO2 Catalyst Under Simulant Sunlight in a Flat Reactor
Catalysts 2018, 8(12), 596; https://doi.org/10.3390/catal8120596 - 01 Dec 2018
Abstract
Improving the capacity of TiO2 semiconductors for visible light response is a key problem for utilization of solar energy in photo-catalytic degradation of organic pollutants. Both catalyst character and reactor conditions are important for the reaction efficiency. The fluorine ion doped TiO [...] Read more.
Improving the capacity of TiO2 semiconductors for visible light response is a key problem for utilization of solar energy in photo-catalytic degradation of organic pollutants. Both catalyst character and reactor conditions are important for the reaction efficiency. The fluorine ion doped TiO2/SiO2 catalyst was prepared by sol-gel method using HF solution as fluorine source. The activity test and UV–vis results indicated that this catalyst was superior to TiO2 P25 in photocatalytic oxidation of gaseous toluene under simulant sunlight irradiation due to the enhancement of visible and ultraviolet light absorbance. GC-MS results indicated that the main intermediates accumulated on active sites included benzoic acid, benzaldehyde, and phenol. A flat interlaid reactor was designed for continuous treatment of the stream with F-TiO2/SiO2 film. The results showed that coating the catalyst on the surface of both top and bottom glass substrates, through the knife coating method with an optimal reactor height, attained the highest efficiency. In addition, the presence of water and oxygen enhanced the oxidation of toluene due to the generation of hydroxyl radicals and peroxy radicals, respectively. The toluene oxidation rate increased with the increase in water vapor concentration in the range of 0~60 vol.%. Full article
(This article belongs to the Special Issue Catalysis for the Removal of Gas-Phase Pollutants)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Recycling of gas phase residual dichloromethane by hydrodechlorination: Regeneration of deactivated Pd/C catalysts.
Abstract: Dichloromethane (DCM) is an important pollutant, with very harmful effects on human health and the environment. Among the available technologies for its removal from gas streams, the recycling to valuable hydrocarbons like alkanes or olefins of low molecular weight by catalytic hydrodeclorination appears as a very interesting alternative. When compared to other precious metals, the use of Pd on supported catalysts showed the better performance in obtaining hydrocarbons with more than one carbon atom or light olefins (C2-C4). However, the catalyst showed a significant deactivation during the reaction. In this study, the evolution of the oxidation state and particle size of Pd was monitored with time on stream in order to elucidate the causes of the deactivation of the catalyst. These were mainly ascribed to the irreversible chemisorption of reactants and reaction products in the active centers, which led to the formation of new PdCx phases. Nevertheless, the catalyst was regenerated by oxidizing treatment at 250 °C, recovering more than 80 % of initial DCM conversion.

Title: Model studies of catalytic CO abatement: single crystals, structure libraries, supported particles
Authors: Suchorski, G. Rupprechter
Affiliation: Institute of Materials Chemistry, Technische Universität Wien, 1060 Vienna, Austria
Abstract: The surfaces of noble metal single crystals have served for long as successful model systems enabling studies of catalytic CO abatement from combustion engines exhausts. However, the materials gap between single crystals and supported nanoparticles of technological catalysts calls for more realistic model systems. In recent years, new types of model systems have been established, exhibiting regions of different crystallographic orientations or different particle sizes within one sample: polycrystalline foils of precious metals, consisting of many µm-sized domains of different structures, differently sized curved crystals with differently oriented facets and metal powder aggregates supported on thin oxide films. The signature property of such model systems is the possibility to examine the inherent catalytic properties of different crystallographic orientations/particle sizes simultaneously under identical reaction conditions by spatially-resolved kinetic experiments (photoelectron and field ion/electron microscopy). Such heterogeneous model systems can be considered as surface structure libraries from which the desired surface structure can be chosen from dozens or even hundreds present on the specimen. In the present contribution we discuss some new insights into catalytic ignition, reaction front propagation, and long-ranging metal/oxide interface effects in catalytic CO oxidation, obtained using these model systems and the novel kinetics by imaging approach.

Title: Cobalt oxide catalysts in the form of thin films prepared by magnetron sputtering on stainless steel meshes: performance in ethanol oxidation
Authors: Květa Jirátová 1,*, Roman Perekrestov 2 , Michaela Dvořáková 3, Jana Balabánová 1, Pavel Topka 1, Martin Koštejn 1, Jiří Olejníček 2, Martin Čada 2, Zdeněk Hubička 2, and František Kovanda 3
Affiliation: 1   Institute of Chemical Process Fundamentals of the CAS, v.v.i., Rozvojová 135, 165 02 Prague, Czech Republic;
2   Institute of Physics of the CAS, v.v.i., Na Slovance 2, 182 21 Prague, Czech Republic
3    Department of Solid State Chemistry, University of Chemistry and Technology, Technická 5, 166 28 Prague, Czech Republic
Abstract: Emissions of volatile organic compounds (VOC) in industrial gases can be reduced applying the catalytic total oxidation. Catalysts in the form of meshes are interesting as they minimize the effect of internal diffusion of reactants during the reaction and as well as the need of expensive active components. In this paper, various conditions of radio frequency magnetron sputtering of cobalt on stainless steel meshes was applied during catalyst preparation. Properties of the supported Co3O4 catalysts were characterized by SEM, XRD, TPR, FTIR, XPS, and Raman spectroscopy. Catalytic activity was examined in deep oxidation of ethanol chosen as a model VOC. Performance of the catalysts depended on the amount of Co3O4 deposited on the supporting meshes. According to specific activities (the amounts of ethanol converted per unit weight of Co3O4) smaller Co3O4 particle size led to increased catalytic activity. The catalyst prepared by sputtering in an Ar+O2 atmosphere without calcination showed the highest catalytic activity, which decreased after calcination due to enlargement of Co3O4 particles. However, specific activity of this catalyst was more than 20 times higher than that of pelletized commercial Co3O4 catalyst used for comparison.

Title: VOC Removal from Manure Gaseous Emissions with UV Light
Abstract: Control of gaseous emissions from livestock operations is needed to assure compliance with environmental regulations and sustainability of the industry. The focus of this research was to mitigate livestock odor emissions with UV light. Effects of the UV dose, wavelength, TiO2 catalyst, air temperature and relative humidity were tested at lab scale on a synthetic mixture of 9 odorous volatile organic compounds (VOCs) and real poultry manure offgas. Results show that it was feasible to control odorous VOCs with both photolysis and photocatalysis (synthetic VOCs mixture) and with photocatalysis (manure offgas). The treatment effectiveness R (defined as % conversion), was proportional to the light intensity for synthetic VOCs mixtures and followed an order of UV185+254 + TiO2 > UV254+TiO2 > UV185+254; no catalyst > UV254; no catalyst. VOC conversion R>80% was achieved when light energy was > 10 J. The use of deep UV (UV185+254) improved the R particularly when photolysis was the primary treatment. Odor removal up to ~80% was also observed for synthetic VOCs mixture, and actual poultry manure offgas. R from ~80 to nearly 100% at a treatment time of at least ~5 s. Scale-up studies are warranted.

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