Pd/Co3O4 catalyst for CH4 emissions abatement: study of SO2 poisoning effect

Abstract

A catalyst with 0.7 wt% Pd load supported over Co 3 O 4 oxide was investigated in the methane oxidation by operating under CH 4 /O 2 stoichiometric conditions. The effect of the noble metal addition on the activity of bare Co 3 O 4 was evaluated. Samples were characterized by BET, XRD, TPR and XPS analyses. The SO 2 poisoning of Pd catalyst and Co 3 O 4 was studied by performing CH 4 oxidation tests under stoichiometric conditions in SO 2 (1 ppm or 10 ppm) . Experiments evidenced that in our conditions the low amount of SO 2 doesn't influence the Pd behaviour, whereas in presence of 10 ppm of SO 2 some deactivation occurs that becomes more evident above 450°C at which the catalyst doesn't reach 100% of methane conversion. Catalytic tests performed over Co 3 O 4 and the Pd supported catalyst, after a treatment at 350°C for 15 h in 10 ppm SO 2 /He, suggest that Co 3 O 4 is a sulphating support, as confirmed by XPS analysis. Therefore, an important role in lowering the sulphur poisoning of Pd may be played by Co 3 O 4 .

Insights into SO2 Interaction with Pd/Co3O4–CeO2 Catalysts for Methane Oxidation

“…Exposure of Pd/Co 3 O 4 to SO 2 at k1 induces complete reduction of PdO x to Pd metallic along with a dramatic agglomeration of the reduced metal. These findings, in line with previous results [17], show a more drastic deactivation likely due to the influence of the palladium precursor, Pd(NO 3 ) 2 instead of Pd(NH 3 ) 4 (NO 3 ) 2 , on the stability of palladium oxide particles towards agglomeration when a support with low surface area, such as Co 3 O 4 is used.…”

“…components and does not change upon addition of SO 2 in the reacting mixture. The S 2p binding energy is typical of sulfate (SO 4 2-) likely present as PdO x ÁSO 3 and Co 3 O 4 ÁSO 3 species [17,18]. The binding energy of Pd 3d 5/2 in all the fresh catalysts is 337.5 eV ± 0.1 eV, which is typical of highly oxidized palladium, PdO x [14].…”

“…The poisoning effect was more drastic upon exposure to SO 2 under lean conditions [18]. Moreover, our previous results indicate Co 3 O 4 -CeO 2 composite oxides promising systems for low-temperature propene and toluene oxidation as well as for methane abatement [19][20][21].…”

“…Co 3 O 4 , CeO 2 and a composite oxide Co 3 O 4 (30 wt%)-CeO 2 (70 wt%), labelled as Co30Ce, were synthesized by precipitation method, with (NH 4 ) 2 CO 3 solution (1 M), from cobalt and cerium nitrates precursors [17]. The precipitate obtained was aged at room temperature for 3 h, filtered and washed with distilled water.…”

“…In a recent work we have reported for Pd/Co 3 O 4 , containing only 0.7 wt% of Pd, high activity in the complete oxidation of CH 4 and a partial deactivation by sulphur poisoning under stoichiometric concentration of oxygen [17]. The poisoning effect was more drastic upon exposure to SO 2 under lean conditions [18].…”