Influence of the addition of H2 upon the behavior and properties of a Pd(2wt.%)/γ-Al2O3 catalyst and a comparison with the case of the Pt-based catalyst

Combustion of CH4/H2/Air Mixtures in Catalytic Microreactors

“…Ptbased materials are well-known as excellent catalysts for H 2 oxidation, [4,5] whereas Pd-based ones are appropriate for CH 4 combustion. [16][17][18] In this case, the H 2 combustion process shift- ).…”

Investigation of the physico-chemical implications of the hydrogen presence during H2-assisted catalytic combustion of methane using Pd(10wt.%)/γ-Al2O3 catalyst

“…O 2 was evacuated under a flow of N 2 (Indugas 99.996%, 60 ml min À1 ) for 30 min and palladium was reduced by means of a gaseous treatment under H 2 5 vol.% N 2 (Indugas 60 ml min À1 ) for 3 h at 400 8C. The reduced catalyst was calcined for 3 h at 600 8C under air in a muffle furnace [23]. After this treatment, samples were submitted to typical methane combustion conditions in a conventional fixed-bed micro-reactor, as described in [23].…”

“…The Pd(10 wt.%)/g-Al 2 O 3 (65 m 2 g À1 ) material was prepared by the wet impregnation technique, as detailed in [23]. In order to prepare 1 g of sample, 900 mg of g-alumina (AlfaAesar 39,812, 99.97%) and 250 mg of Pd(NH 3 ) 4 Cl 2 ÁH 2 O (Aldrich 32,343-8, 99.99%) were used.…”

“…Unfortunately, information is scarce concerning the effective influence of the hydrogen presence in the CCM feed on the physico-chemical properties of the catalyst. In a previous paper [23], we studied the behaviour of a commonly used 2 wt.% Pd-loaded catalyst in H 2 -assisted CCM; catalytic results were very informative. They indicated that the catalyst progressively activates as the hydrogen concentration increases up to a threshold value (5 vol.% H 2 ), then inhibition occurs.…”

“…To summarize our approach, we might say that, in a first step, we investigated the influence of H 2 in CMM on the catalytic activity, using a 2 wt.%-loaded catalyst [23] and, in a second step, the present work, we focused on the physico-chemical properties of the palladium particles, using a 10 wt.%-loaded catalyst after being submitted to typical methane combustion conditions. Our final goal is to take advantage of the physico-chemical hints gathered in this study to propose tentative explanations concerning the behaviour of the Pd(2 wt.%)/g-Al 2 O 3 catalyst during the H 2 -assisted catalytic combustion of methane observed in the previous study [23]. Further studies concerned with the use of a moderate loading of palladium (4-5 wt.%) could give sufficiently accurate activity and physico-chemical data from one and only set of experiments.…”