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At present the denoxing of waste gases from fossil fuel combustion is performed at about 95% of the reported applications by the SCR (selective catalytic reduction) process, which utilises NH(3) as the reducing agent. The present study investigates an alternative process which uses hydrogen instead of ammonia. The process development work conducted during the study concentrated on the investigation of the basic chemistry of the overall H(2)+NO+O(2)+SO(2)/Pd-Al(2)O(3) catalytic system. The main results led to the proposal of a reaction mechanism based on the intermediate formation of N(2)O, and an explanation of several selectivity effects (NH(3) formation and hydrogen reaction selectivity) by the influence of special adsorption states of NO on the Pd surface. In addition, several potential SO(2) poisoning mechanisms were screened. These include SO(2) interactions with Pd, Al(2)O(3) and the reactants H(2), NO and O(2). It was found that SO(2)-H(2)-NO-interactions prevail and lead to the deposition of atomic sulphur on the catalytic surface. Based on these results a novel catalyst regeneration method was developed, consisting of a combined oxidative/reductive treatment under conditions of pulsing oxygen feed.

Additional information

Authors: PAPAMELETIOU D ET AL., JRC Ispra (IT);MATIS K A ET AL., Aristotelian University of Thessaloniki, Department of Chemistry (GR)
Bibliographic Reference: Paper presented: 6th International Symposium on Environmental Pollution and its Impact on Life in the Mediterranean, Como (IT), Oct. 6-9, 1991
Availability: Available from (1) as Paper EN 36542 ORA
Record Number: 199210057 / Last updated on: 1994-12-02
Original language: en
Available languages: en