Durability of VOC catalysts in solvent emission oxidation

Topics in Catalysis, 2016

The ageing conditions were analyzed with gasoline, diesel and natural gas (NG) catalysts to find the simplified, rapid thermal and chemical (sulfur) ageing methods for catalyst development. Rich-stoichiometric conditions prevented the deactivation of TWCs in gasoline and NG applications. Active metals and support are sintered thermally during short lean periods by increasing deactivation as a function of oxygen concentration. Air ageing for 3-10 h is an appropriate rapid ageing method for TWCs. Active regeneration conditions for DPF with a higher carbon concentration deactivated DOCs less than normal diesel exhaust conditions at 700°C. Natural gas oxidation catalysts were sulfated in use conditions but almost complete recovery was possible above 600°C with higher methane feeds at lean. In addition to sulfur, other chemical poisoning was also included in the rapid ageing methods by fittings to the diesel and NG field aged catalysts.

Volatile organic compounds (VOC) are the organic chemical with high vapor pressure at ordinary room temperature. VOC like alkanes, halogenated compounds, aldehydes, alcohols, ketones, olefins, aromatics compounds, and ethers are emitted by different sources, particularly from petroleum refining, chemicals plants, power plants, pharmaceutical plants, solvents processes. VOC are one of the formation of photochemical ozone, consequently they are class of air pollutant that have deleterious effect on community lives and environment. Therefore, it is crucial to minimize the emission of volatile organic compound. Despite the success of adsorption and thermal oxidation of VOC emissions, there is still a need for research on techniques which are both economically more favourable and actually destroy the pollutants rather than merely remove them for recycling elsewhere in the biosphere. The catalytic destruction of VOC to CO2 and H2O using noble metals as catalyst with Al2O3 support on fixed bed catalytic reactor to eliminate VOCs for safety and environmental protection appears most economical, an emerging as a promising alternative technology in controlling VOCs emitted from industrial waste gases due to the great amount of energy saved by the low temperature involved and because of its versatility of handling a range of organic emission under mild operation condition in this context and is the subject of the present design paper.

Catalysis Today, 2000

Mono- and multi-metallic (bi- and tri-) Pt, Pd and Rh supported on cerium-promoted alumina (La Roche, SAS-1/16) catalysts were tested for activity as TWC, both fresh [G.C. Koltsakis, and A.M. Stamatelos, Progr. Energy Combust. Sci. 23 (1997) 1] and after accelerated aging. Aging consisted of a treatment at 900°C for 5 h during which an oxidizing (2.5% O2, 10% H2O, in N2) and a reducing (5.0% CO, 10% H2O, in N2) feedstream were cycled at 0.017 Hz through the catalyst. Activity tests were carried out by increasing temperature from 100 to 600°C at 3°C min−1, while two oxidizing and reducing (±0.5 A/F) feedstreams were alternately (1 Hz) fed through the reactor at 125 000 h−1 (STP). Conversion was continuously analyzed. Light-off temperature, T50, conversion at 500°C (normal running temperature), X500, and the stoichiometric window (A/F from 14.13 to 15.13) for stationary feedstreams, were determined.

Applied Catalysis A-general, 2015

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Catalysis Today, 2008

This paper presents the effect of aging on a series of commercial three way catalysts, of the same supplier, by analyzing their chemical, textural, structural and catalytic properties. The catalysts were aged in a motor bench test, involving runs of 150 or 300 h and using gasoline with two sulfur levels: 400 and 700 ppm. The catalysts were characterized by X-ray diffraction (XRD) and fluorescence (XRF), surface area, pore volume and pore diameter. The catalytic activities were determined based on CO and propane conversions. After aging, a decrease in surface area and pore volume was observed, as well as an increase in mean pore diameter. Evidence of the presence of a-Al 2 O 3 , d-Al 2 O 3 and PdO phases was found according to XRD data, which can be attributed to a severe thermal deactivation of the catalysts. Some crystalline compounds containing fuel contaminants like cerium phosphate were also identified. The activity for CO and C 3 H 8 oxidation presented a slight correlation with the surface area of the aged catalysts.

Topics in Catalysis, 2004

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Applied Catalysis B: Environmental, 2010

Oxidation of 20 hydrocarbons (from C10 to C42) representative of soluble organic fraction of Diesel soots were investigated by mixing the hydrocarbon (solid at ambient temperature) with a 0.55 wt%Pt/Al 2 O 3 catalyst (Pt particle size below 1.2 nm). Oxidation rates were characterized by the temperature of halfconversion (T 50 ) and by the quantity of oxygen consumed during the reaction, which allows to determine the amount of the solid hydrocarbon (initially 100 mg of a mixture of 0.133 mmol HC with 2 g of catalyst) actually oxidized during heating in 1%O 2 /He.

Applied Catalysis B-environmental, 2000

Catalytic total oxidation of some selected chlorinated hydrocarbons is studied with several Pt-based catalysts. Chlorinated hydrocarbons used have been ethyl chloride, trichloroethylene and dichloromethane, alone or mixed with some hydrocarbons, such as toluene. Eighteen different catalysts have been tested from eight different manufacturers (Degussa AG, Süd-Chemie AG, Kataleuna GmbH, Chimet, Johnson Matthey, Prototech Co., . . . ) and from three research institutions (Universities of Leiden (NL) and Wroclaw (PL) and Spanish CSIC-ICP). Catalysts both in the form of spheres (particulates) and of monoliths are used. Selection of the best catalyst(s) is made based on their activity, selectivity and life. Apparent energies of activation for these reactions on these catalysts, using an empirical first-order reaction rate, are given. There are interesting or noticeable differences in activity and selectivity among the tested Pt-based catalysts. In overall they are not so active as the chromia and vanadia-based catalysts but they have an high life, reason why they can be recommended for this application.

Topics in Catalysis, 2013

Deactivation of the natural-gas-vehicle-aged Pt/Pd oxidation catalyst supported on g-alumina-based washcoat was studied by electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and catalytic activity measurements. Significant structural changes were detected in the used catalyst compared to the fresh one. Grain size of the washcoat had grown but its structure had remained the same, g-alumina, as in the fresh catalyst. Sintering of the noble metal particles had occurred, particle sizes varied from ~5 nm up to ~100 nm. Decomposition of palladium oxide and platinum oxide to metallic Pd and Pt occurred followed by the formation of the bimetallic Pt/Pd crystals. Also reformation of palladium oxide was detected. In addition, the inlet part of the used catalyst was totally covered by a poisoning layer. Due to these structural changes and poisoning, the activity of the vehicle-aged catalyst had decreased significantly compared to the fresh one. All the changes were stronger in the inlet than in the outlet part of the used catalyst indicating higher operating temperature and more extensive thermal deactivation and poisoning in the inlet than in the outlet part of the converter.

Applied Catalysis B-environmental, 1998

The complete catalytic oxidation of 1,2-dichloroethane (DCE) and trichloroethylene (TCE) over alumina supported noble metal catalysts (Pt and Pd) was evaluated. Experiments were performed at conditions of lean hydrocarbon concentration (around 1000 ppm) in air, between 250°C and 550°C in a conventional fixed bed reactor. The catalysts were prepared in a range of metal contents from 0.1 to 1 wt%. Palladium catalysts resulted to be more active than platinum catalysts in the oxidation of both chlorinated volatile organic compounds. DCE was completely destructed at 375°C, whereas TCE required 550°C. HCl was the only chlorine-containing product in the oxidation of DCE in the range of 250–400°C. Tetrachloroethylene was observed as an intermediate in the oxidation of TCE, being formed to a significant extent between 400°C and 525°C. CO was also detected in the oxidation of both DCE and TCE over Pd catalysts, though at temperatures of complete destruction, CO2 was the only carbon-containing product. The Pt catalysts were selective to CO2 at the studied conditions.