Development of copper-on-alumina catalytic materials for the cleanup of flue gas and the disposal of diluted ammonium su
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B.K. Hodnett Department of Chemical and Life Sciences, University of Limerick, Limerick, Ireland
P. Jaeger Rhone-Poulenc, Centre de Recherches d'Aubervilliers, 52 Rue de la Haie Coq, 93308 Aubervilliers Cedex, France
C. Macken Department of Chemical and Life Sciences, University of Limerick, Limerick, Ireland
M. Marella and M. Tomaselli Enirisorse, Centro Ricerche Venezia, via delle Industrie 39, Porto Marghera (VE), Italy
G. Paparatto Enichem, C.R. Bollate, Via S. Pietro 50, 20021 Bollate (MI), Italy
S. Perathoner Dip. Chimica Ind. e dei Materiali, V. le Risorgimento 4, 40136 Bologna, Italy (Received 18 July 1994; accepted 21 October 1994)
Some aspects of the industrial development of copper-on-alumina catalytic materials for the combined removal of SO 2 (DeSO*) and NO* (DeNOJ from flue gas of power plants are discussed. Applications of these catalytic materials for the recovery of sulfuric acid from diluted aqueous solutions of ammonium sulfate are also outlined. In particular, the following specific topics are analyzed: (i) the relationship between textural and reactivity properties, (ii) the problem of the design of samples with improved DeSO* properties in relation to the stability of the samples over extended operations, and (iii) the optimization of the regeneration characteristics of the samples. Details on the flow sheet of the technology are also given.
I. INTRODUCTION Reduction of emission levels for SO2 and NO* continues to be a major technological problem, particularly for developed countries with high population densities. Between 1970 and 1986 total SO 2 emissions in Europe and the USA declined by 40 and 25%, respectively. By contrast, NO* emissions increased by 20% in Europe and by 6% in the USA over the same period. Additional reductions in SO 2 emission levels and a lowering in NO* levels are required according to the latest international directives.1 The principal technological difficulties are those of cost and retrofitting to existing power plants.2 Over the past 15 years a number of systems have been developed in efforts to reduce the emission levels. Initially, efforts were focused on systems for the separate removal of SO2 and NO*. Probably the best-known method for the removal of SO 2 is as calcium sulfate or sulfite by wet or dry contact of the flue gases with calcium oxide. In this approach SO 2 flue gas levels can J. Mater. Res., Vol. 10, No. 3, Mar 1995
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be reduced by up to 90%, but the method is costly and changes the problem to one of disposal of a greater bulk of CaSO 4 . 3 ' 4 Selective catalytic reduction of NO* by NH 3 over V/TiO 2 catalysts is a well-known technology,5 but it is also costly and is prone to deactivation through contact between the catalyst and SO 2 , whereby (NH 4 ) 2 SO 4 poisons the catalytically active surface sites.6"8 This problem can be overcome by operating at temperatures above the sublimation temperature of (NH4)2SO4, but NH 3 is oxidized to NO* in these conditions.6"8 More recent approaches t
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