Catalyst combustion, catalytic

Catalytic combustion is a process in which a combustible compound and oxygen react on the surface of a catalyst, leading to complete oxidation of the compound. This process takes place without a flame and at much lower temperatures than those associated with conventional flame combustion. Due partly to the lower operating temperature, catalytic combustion produces lower emissions of nitrogen oxides (NOx) than conventional combustion. Catalytic combustion is now widely used to remove pollutants from... 

Catalytic combustion of diesel soot particulates over LaMnOs perovskite-type oxides prepared by malic acid method has been studied. In the LaMn03 catalyst, the partial substitution of alkali metal ions into A site enhanced the catalytic activity in the combustion of diesel soot particulates and the activity was shown in following order Cs>K>Na. In the LarxCs MnOj catalyst, the catalytic activity increased with an increase of X value and showed constant activity at the substitution of x>0.3... 

Fig. 15.11 (a),(b) Fraction of CNT catalysts combusted after 24 h time on stream in a 02/He gas mixture (a) CNTs, (b) 5 wt% P205/CNTs. (a),(b) Reprinted with permission from [25]. Copyright (2011) American Chemical Society, (c) Catalytic performance of B203-modified CNT catalysts in the ODH of propane. Propene selectivity at 5 % propane conversion ( ) and reaction rate (o) as a function of B203 loading, (d) Reaction scheme of CNT-cataiyzed ODH. (c),(d) Reprinted with permission from [61]. Copyright (2009) Wiley VCH. 

In propylene epoxidation catalyzed by trimethylsilylated Au-Ba(N03)2/Ti-Si02, the introduction of the gas promoter trimethylamine (13-15 ppm) to the reactant gas stream appreciably improved catalytic performance [149] (Figure 3.20). Surprisingly, trimethylamine made the used catalysts better than fresh catalysts in catalytic performance. Possible reasons are (i) trimethylamine might destroy the mobile acid sites that appear and disappear intermittently, suppressing by-product formation from PO (ii) trimethylamine can also adsorb on the surfaces of Au and depress the combustion of H2 to form H20, thus leading to improved H2 utilization efficiency. 

The commonly practiced method of regenerating coked catalysts or catalytic membranes is by combustion with air, air/stcam mixtures, air/nitrogen mixtures, or dilute oxygen streams with another carrier gas. 

Figure 13.6. Temperature range of ceha based catalysts in catalytic combustion...

H. Arai, K. Eguchi, M. Machida, and T Shiomitsu, Heat resistance of hexaaluminate catalyst for high-temperature catalytic combustion. Catalytic Science and Technology 7 195 (1991). 

The approach of controlling morphology to control sintering offers several interesting possibilities, and these are actively under consideration. At least one involves heat resistant hexa-aluminate catalysts for catalytic combustion [46). 

Transient experiments were performed on a 12 1 heavy duty diesel engine, with a 24 1 monolithie catalytic converter connected to the exhaust pipe. The eatalytic converter contained two different catalysts, both supplied by Johnson Matthey. These were an 18 1 high temperature active (HT) catalyst placed upstream and a 6 1 low temperature active (LT) catalyst placed downstream. The HT catalyst provides the main capacity for NOx reduction. The LT catalyst combusts unreacted hydrocarbon from the HT catalyst and contributes with some NOx reduction at lower temperatures. As this study only concerns the performance of the HT catalyst, the LT catalyst will not be discussed further, and the HT catalyst will be referred to simply as the catalyst. 

Pt/(3-SiC Catalyst for Catalytic Combustion of Carbon Particles in Diesel Engines... 

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. 

Takahashi, T., Jotani, F., Metal Catalysts for Catalytic Combustion, Fuel... 

SYNTHESIS AND STUDY OF HONEYCOMB MONOLITHIC CATALYSTS FOR CATALYTIC COMBUSTION... 

Ceramic catalyst burner for catalytic combustion Catalytic combustion device... 

As a preventive solution to the problem of NOx emissions, catalytic combustion has come to the forefront during the last two decades. The focus of major interest here is its application in gas turbines for power generation and for transportation by road, water or air. Any catalyst for catalytic combustion, however, has to face extreme demands above 1000°C in the presence of oxygen and steam, in uninterrupted operation for at least one year also, resistance to impurities or poisons in the fuel and to severe thermal and mechanical shocks. Promising developments in catalytic supports, washcoats and active materials are reviewed briefly. 

XaYfcZcSn207 Pyrochlore-type catalyst for catalytic combustion of methane... 

The purpose of the present paper is to investigate the behavior of high temperature stable support in complete oxidation of methane, when sulfur species are present in the feed. Various characterization methods have been employed here in order to give a general picture of the deactivation of supported Pd catalysts in catalytic combustion of methane. This work will examine the reactivity of supported Pd catalysts, when the metal particles are dispersed over a thermally stable material, containing rare earth elements. Moreover, we will focus on the behavior of the catalysts when sulfur species are added to the feed, as sulfur can be present in significant amounts in natural gas. 

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