Palladium catalytic combustion

PGM catalyst technology can also be appHed to the control of emissions from stationary internal combustion engines and gas turbines. Catalysts have been designed to treat carbon monoxide, unbumed hydrocarbons, and nitrogen oxides in the exhaust, which arise as a result of incomplete combustion. To reduce or prevent the formation of NO in the first place, catalytic combustion technology based on platinum or palladium has been developed, which is particularly suitable for appHcation in gas turbines. Environmental legislation enacted in many parts of the world has promoted, and is expected to continue to promote, the use of PGMs in these appHcations. 

Thevenin PO, Pettersson AALJ, Jaras SG, Fierro JLG (2003) Catalytic combustion of methane over cerium-doped palladium catalysts. J Catal 215 78-86... 

Pfefferle and Lyubovsky executed types of measurements that yielded critical information between active Pd phases for catalytic combustion using pure ot-alumina plates with zero porosity as a support for the catalyst. This procedure uniformly covers the plate with metal particles on the top surface where they are easily available for the reaction gases and optical analysis. This type of experimental procedure has shown that in high-temperature methane oxidation the reduced form of the supported palladium catalyst is more active than the oxidized form. The temperature at which the PdO Pd... 

R.W. Sidwell, H. Zhu, R.J. Kee, D.T. Wickham, C. Schell, and G. S. Jackson. Catalytic Combustion of Premixed Methane-Air on a Palladium-Substituted Hexalumi-nate Stagnation Surface. Proc. Combust. Inst., 29,2002. 

At present, one catalytic combustion system has been implemented at a full scale the XONON Cool Combustion technology, developed by Catalytica Energy Systems 157,158). The system is operated as follows Fuel from a lean-mix prebumer and the main fuel stream together with compressed air pass through the catalyst module (palladium oxide catalyst deposited on corrugated metal foil) in which the gas reaches a temperature up to 1623 K. The UHC and CO are combusted to essentially full conversion, downstream of the catalyst in the homogenous combustion zone. The guaranteed emission levels are as follows NOj < 3 ppm. 

R.J. Farrauto, M.C. Hobson, T. Kennelly, and E.M. Waterman, Catalytic chemistry of supported palladium for combustion of methane, AppL CataL A. 81 221 (1992). 

Although the process configuration varies widely there are three main steps common to each, they are oxidation of ammonia to nitric oxide (NO), oxidation of NO to nitrogen dioxide (N02), and then absorption of N02 in water to produce nitric acid (Figure 3.11). The first step of the catalytic combustion of ammonia takes place over a catalyst consisting of platinum/rhodium (90 10) or platinum/rhodium/palladium (90 5 5). The reaction is very rapid and goes almost to completion as shown in Reaction 3.11. The reaction is one of the most efficient catalytic processes in industrial chemistry, having an extremely... 

The first innovative systems engineering approach is of Osaka Gas Company in Japan. They developed a multiple monolith catalyst design for the gas-turbine combustion of methane. In this design, different materials are used to fulfil different functions within the catalyst. A palladium catalyst is placed at the entrance of the catalyst system to ignite the catalytic combustion reaction and to raise the temperature. This temperature is then enough... 

Keywords catalytic combustion, palladium, FeCrAlloy fibers, dip-coating... 

Alumina is widely used as a support for palladium oxide which is the most active phase for methane catalytic combustion [1]. Indeed, provided the reaction temperature does not exceed 900°C, alumina phase transformation is not favoured and sintering is limited. However, the active phase PdO decomposes into much less active metallic Pd above ca. 750°C [1]. It is therefore strongly... 

The 9A2B1 sample was used for supporting palladium (2 wt %). The resulting catalyst and the 2 wt % Pd/Al203 reference sample were studied in the methane catalytic combustion. Catalytic tests were performed in the temperature range of 300°C-900°C using 1% CH4, 4 % O2 and N2 balance at total flow rate of 36 L/h. Prior to catalytic activity measurements, samples were treated in the reaction mixture up to 900°C for stabilisation. Catalytic run consisted of heating from 300°C to 900°C at l°C/min. 

These data confirm that the perovskite stabilizes palladium and suggest that the activity in catalytic combustion can be more efficiently recovered, through a regeneration oxidizing process, for these systems than for the usual Pd/y-Al203 supported catalyst, due to the palladium moiety re-incorporated in the perovskite structure at a high oxidation state (Pd" ). 

Palladium is the most often used PGM in catalytic combustion applications for natural gas. Palladium exists in the form PdO at low temperatures, probably at least on the surface of the particle. As the temperature increases there is a reduction of PdOx to metallic Pd, around ca. 800 The reaction is reversible... 

Methane is the most difficult hydrocarbon to oxidize since it contains no C-C bond, but only C-H bonds, which are more difficult to break [4]. Palladium is reported to be the most active species in catalytic combustion of methane, when operating under oxidizing atmosphere [5]. Several studies have focused on complete oxidation of methane over palladium catalysts supported on alumina [6-8]. The catalytic combustion of methane over supported palladium catalysts is reported to be stmcture sensitive the activity of the catalyst is directly influenced by the size of the metallic particles [9]. 

The objective with the present work was to study catalytic combustion and the poisoning effect of sulfur in the catalytic combustion of gasified industrial waste over palladium and platinum catalysts on different support materials. 

Baldwin, T. R. Burch, R. Remarkable activity enhancement in the catalytic combustion of methane on supported palladium catalysts. Catalysis Letters 6,131 (1990). 

Bimetallic catalyst formulations of palladium and platinum have been applied for the catalytic combustion of light hydrocarbons, which showed higher stability compared with monometallic samples. 

Sidwell RW, Zhu H, Kee RJ, Wickham DT, Schell C, Jackson GS Catalytic combustion of premixed methane/air on a palladium-substituted hexaluminate stagnation surface, Proc Combust Inst 29 1013—1020, 2002. 

Garbowski, E., Feumi-Jantou, C., Mouaddib, N. et al (1994). Catalytic combustion of methane over palladium supported on alumina catalysts evidence for reconstruction of particles, Appl. Catal., 109, pp. 277-291. 

It has been published that hydrophobic-activated carbons can be suitable supports for noble metal species active for total oxidation. The catalytic behaviour of platinum and palladium supported on carbon-based monoUths was studied in the low temperature catalytic combustion of benzene, toluene and m-xylene, and compared with the corresponding behaviour of Pt-supported on y-Al203 coated monoliths. Carbon-based monoliths showed much better catalytic performance, which was ascribed to the fact that the carbon surface is more hydrophobic than the y-Al203, and the poisoning effect of water molecules produced during the combustion was... 

Ciuparu, D., Lyubovsky, M., Altman, E., et al (2002) Catalytic Combustion of Methane Over Palladium-based Catalysts, Catal. Rev., 44, pp. 593-649. 

Baldwin, T. and Burch, R. (1990). Catalytic Combustion of Methane over Supported Palladium Catalysts I. Alumina Supported Catalysts, Appl. Catal B Environ., 66, pp. 337-358. Yamamoto, H. and Uchida, H. (1998). Oxidation of Methane over Pt and Pd Supported on Alumina in Lean-bum Natural-gas Engine Exhaust, Catal. Today, 45, pp. 147-151. 

Ryoo, M., Chung, S., Kim, J., et al (2003). The Effect Of Mass Transfer on the Catalytic Combustion of Benzene and Methane over Palladium Catalysts Supported on Porous Materials, Catal Today, 83, pp. 131-139. 

Lingyun, J., Mai, H., Jiqing, L., etal (2008). Palladium Catalysts Supported on Novel CexYl-xO Washcoats for Toluene Catalytic Combustion, J. Rare Earths, 26, pp. 614-619. 

In a more interesting process, all of the fuel/air mixture is added to a combustor with three sections. The first section contains an active palladium oxide catalyst that can operate up to about 800°C before being reduced to palladium metal which is less active. The palladium oxide catalyst is regenerated by reoxidation of the metal as temperature falls. A more stable catalyst in the second section continues the catalytic combustion. In the third section, combnstion is completed by thermal reaction and the gas temperature increases to 1300°-1400 C. Overall, less than 1 ppm NOX is formed. Palladium oxide is supported on a monolith coated with temperature resistant barium hexaaluminate. ... 

Catalytic Oxidation. Catalytic oxidation is used only for gaseous streams because combustion reactions take place on the surface of the catalyst which otherwise would be covered by soHd material. Common catalysts are palladium [7440-05-3] and platinum [7440-06-4]. Because of the catalytic boost, operating temperatures and residence times are much lower which reduce operating costs. Catalysts in any treatment system are susceptible to poisoning (masking of or interference with the active sites). Catalysts can be poisoned or deactivated by sulfur, bismuth [7440-69-9] phosphoms [7723-14-0] arsenic, antimony, mercury, lead, zinc, tin [7440-31-5] or halogens (notably chlorine) platinum catalysts can tolerate sulfur compounds, but can be poisoned by chlorine. 

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