Aging of Premixed Metal Fiber Burners for Natural Gas Combustion Catalyzed with Pd/LaMnO₃·2ZrO₂

Abstract

The aim of this work is the study of the aging effect induced by S-compounds added as odorants in the natural gas network over a previously developed catalysts now deposited on a FeCrAl alloy fiber mat (NIT 200/S by ACOTECH BV). A novel generation of catalytic premixed fiber burners for low-environmentalimpact natural gas combustion are based on Pd/LaMnO 3 ‚2ZrO 2 catalyst, where ZrO 2 acts as a structural promoter and the noble metal/perovskite synergism is effectively exploited, leading to enhanced performances with respect to noncatalyzed burners. The catalytic premixed fiber burners were characterized by means of field emission scanning electron microscope/energy dispersive spectrometer (FESEM/EDS), temperature programmed desorption/reduction/oxidation (TPD/R/O), and thermogravimetric/mass spectroscopy (TG/MS) techniques. The combustion runs were accomplished in a domestic boiler pilot plant under realistic operating conditions. An unexpected improvement was found in the overall performance of catalyzed burners after sulfur aging carried out up to 3 weeks (the catalyzed burners were kept in an electric oven at 800 °C under a N 2 flow containing 200 ppmv of SO 2 ). Despite the effect of catalyst thermal stress and aging, the overall performance, in terms of pollutant emissions, was preserved after accelerated lifetime utilization. This is probably due to the presence of microfractures on the aged burners, accomplished by an increase of active sites for β-type oxygen desorption, able to improve methane combustion.

Surface chemistry and reactivity of Pd/BaCeO3∙2ZrO2 catalyst upon sulphur hydrothermal treatment for the total oxidation of methane

“…After water evaporation, the heat released in the fast reaction allowed the formation of the catalytic powder. Subsequently, the as-prepared powder was calcined in oven at 800 °C for 2 h in still air [12], so as to favour the decomposition of eventually unreacted nitrate precursors, and to promote the formation of the perovskite structure. After that, 2 wt.% Pd was added in a stoichiometric amount by adding Pd(NO 3 ) 2 in its initial aqueous solution.…”

“…After that, 2 wt.% Pd was added in a stoichiometric amount by adding Pd(NO 3 ) 2 in its initial aqueous solution. A further calcination in still air at 600 °C followed, in order to promote the full decomposition of Pd(NO 3 ) 2 into the oxidized form PdO [12].…”

“…The selected temperature, 800 °C, is the typical average flame temperature at which the burner in domestic boilers normally works [12,14]. 200 ppmv of SO 2 was also added [12,14,18,20,62].…”

“…The selected temperature, 800 °C, is the typical average flame temperature at which the burner in domestic boilers normally works [12,14]. 200 ppmv of SO 2 was also added [12,14,18,20,62]. The SO 2 concentration was chosen several times higher than the odorant supplementary concentration in commercial natural gas (about 8 ppmv, in Italy, according to Italian regulations, as tetrahydrotiophene, C 4 H 8 S) so as to accelerate any possible poisoning effect [12,14,[16][17][18].…”

“…200 ppmv of SO 2 was also added [12,14,18,20,62]. The SO 2 concentration was chosen several times higher than the odorant supplementary concentration in commercial natural gas (about 8 ppmv, in Italy, according to Italian regulations, as tetrahydrotiophene, C 4 H 8 S) so as to accelerate any possible poisoning effect [12,14,[16][17][18]. SO 2 /SO 3 species, in fact, resulted from the total oxidation of S-containing organics during the combustion process [16].…”