Methane catalytic combustion over Pd/Al 2 O 3 in presence of sulphur dioxide: development of a regeneration procedure
- PDF / 315,909 Bytes
- 8 Pages / 595 x 794 pts Page_size
- 39 Downloads / 209 Views
Catalysis Letters Vol. 100, Nos. 1–2, March 2005 (Ó 2005) DOI: 10.1007/s10562-004-3081-1
Methane catalytic combustion over Pd/Al2O3 in presence of sulphur dioxide: development of a regeneration procedure Salvador Ordo´n˜ez*, Paloma Hurtado, and Fernando V. Dı´ ez Department of Chemical and Environmental Engineering, University of Oviedo, Julia´n Claverı´a s/n, 33006 Oviedo, Spain
Received 01 October 2004; accepted 28 October 2004
Five different procedures (treatments with hydrogen, nitrogen, wet and dry air, and under vacuum) were tested for the regeneration of a partially deactivated alumina-supported Pd catalyst, used for the catalytic incineration of methane in presence of SO2. The efficiency of these processes was evaluated considering the temperatures at which both, the catalysts deactivation, and the regeneration processes, took place. As general trend, hydrogen treatment is the best regeneration procedure, followed by treatment with wet air, whereas high deactivation temperatures lead to less efficient regeneration. The efficiency of the regeneration was observed to increase as regeneration temperature increases. These trends are discussed according to the results obtained in the characterisation of deactivated catalyst samples using TPR, TPO and TPD. KEY WORDS: catalyst regeneration; sulphur poisoning; methane combustion; palladium catalysts.
1. Introduction Catalytic combustion has become a very interesting alternative for the treatment of gaseous emissions containing diluted organic compounds, because of its low energy consumption (especially if compared with thermal oxidation) and the very small formation of noxious by-products, such as thermal NOX [1,2]. Among the organic compounds present in gaseous emissions, methane is receiving increasing attention. This interest is justified by two considerations: on the one hand, methane is an important contributor to the greenhouse effect (its global warming potential is 21 times higher than that of carbon dioxide); on the other hand, the catalytic oxidation of methane is more difficult than for most volatile organic compounds [3]. Thus methane has been chosen by many authors as a model compound for catalytic oxidation studies, as the catalytic combustion of most organic compounds would be ensured if methane is quantitatively abated. In many gaseous emissions (i.e., from carbochemical and petrochemical processes, treatment of solid wastes and wastewaters, motor vehicle exhaust gases, etc.), methane is accompanied by other inorganic (CO, CO2, NO, H2, H2O, NH3, H2S, SO2, etc.) and organic compounds (alkanes, alkenes, aromatics, etc.). Among these compounds, it was demonstrated in previous studies that sulphur compounds (SO2 and H2S) play a key role in the deactivation of the catalysts used for methane combustion [4,5]. Moreover, the conventional sulphur trapping systems are not efficient enough for the total
*To whom correspondence should be addressed. E-mail: [email protected]
removal of sulphur compounds, as pointed out in the literature [6]. The complete catalytic ox
Data Loading...
