Promoting effect of the alloy formation over Ni-Fe/Al 2 O 3 catalysts for the steam reforming of biomass tar to synthesi
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Promoting effect of the alloy formation over Ni-Fe/Al2O3 catalysts for the steam reforming of biomass tar to synthesis gas Lei Wang1, Dalin Li1, 2, Mitsuru Koike1, Yoshinao Nakagawa1, 2 and Keiichi Tomishige1, 2* 1 School of Engineering, Tohoku University, 6-6-07, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan 2 Japan Science and Technology Agency, CREST, 6-6-07, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan ABSTRACT The addition of Fe addition with suitable amount to Ni /Al2O3 catalyst showed higher catalytic performance than corresponding monometallic Ni and Fe catalysts in the steam reforming of tar from the pyrolysis of cedar wood. Characterization of the catalysts indicates the formation of the Ni-Fe alloys and the surface segregation of Fe atoms on the alloys, and it was also suggested that the structure was almost maintained during the reaction. The surface Fe atoms accept oxygen atom from steam and subsequently supply oxygen species to adsorbed carbonaceous species on neighboring surface Ni atoms, which is connected to the promotion of the steam reforming reaction of tar and the suppression of the coke formation.
INTRODUCTION One of the important processes for the production of renewable liquid fuels and chemicals is the conversion of biomass to synthesis gas because the synthesis gas can be converted to fuels and chemicals by using the various catalytic reactions [1]. In the biomass gasification, which has been usually carried out in a non-catalytic system, the residual tar causes serious problems in the equipment downstream. Here, it is expected that catalysts contribute to the decrease of tar concentration in the produced gas, for example, by the steam reforming reaction of tar. Development of catalysts with high activity and stability enables the tar removal at lower reaction temperature and the decrease of the catalyst cost. In the reforming reaction, high resistance to coke deposition is an important property in terms of the catalyst stability. It has been known that Ni is an excellent element for the steam reforming reaction, additives oxides and other metals has been investigated. It has been recently reported that the addition of CeO2 to Ni catalysts enhance the catalytic performance, and that, the formation of the Ni-CeO2 nanocomposite and large interface between Ni metal and Ce oxide surface was related to high catalytic activity and high resistance to coke formation [2-5]. In the present article, we investigated the performance of Ni-Fe/Al2O3 catalysts prepared by co-impregnation method in the steam reforming of tar derived from the pyrolysis of cedar [6]. It is expected that the interaction of Ni with Fe is stronger than that with CeO2 because of the formation of Ni-Fe alloys,
which can connected to remarkable promoting effect of Fe by its redox property.
EXPERIMENTAL DETAILS The support material of α-Al2O3 was prepared by the calcination of γ-Al2O3 (JRC-ALO-1, Catalysis Society of Japan, 143 m2g-1, grain size 2-3 mm) in air at 1423 K. After the calcination, it was crushed and sieved to par
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