Reducibility of Ni and NiPt supported on zeolite beta investigated by XANES

Nickel and nickel-platinum supported on zeolite beta in proton form (Ni/HBEA and NiPt/HBEA) with Ni loading of 1, 3, 5 wt.% and Pt loading of 1 wt.% were prepared by impregnation. Characterization by ex situ X-ray absorption near edge structure (XANES) showed that the oxidation state of Ni in all calcined samples were +2 and reducibility of nickel by hydrogen flow increased with metal loading. At low loading, nickel had a strong interaction with the zeolite and was difficult to reduce. The interaction became weaker as the Ni loading increased, resulting in more agglomeration to larger cluster size which could be reduced more easily. Dependence of Ni reducibility on temperature and time for the mono- and bimetallic samples with 5 wt.% Ni loading was investigated further by in situ XANES. The reducibility in the bimetallic sample was increased with temperature and time, higher than the monometallic one due to the presence of Pt. In addition, the bimetallic sample was best reduced, when investigated in situ, at 350 °C for 60 min.