Steam reforming of phenol–ethanol mixture over 5% Ni/Al2O3

The steam reforming of 1:2 phenol–ethanol mixture (ca. 80 gph + eth/N m3 in He) as a model of biomass gasification tar, has been investigated over Ni/Al2O3, Ni/MgO-Al2O3 and Ni/ZnO-Al2O3 catalysts. In this paper interest is focused over a 5% Ni-Al2O3 catalyst, that has been characterized in the unreduced and reduced states by IR of CO adsorbed at low temperature. The steam reforming reaction of ethanol and phenol has also been studied, separately, by IR spectroscopy. In spite of its low Ni content and the absence of alkali and alkali earth ions, this catalyst is actually active in the steam reforming of both ethanol and phenol. The reaction is, however, shifted to higher temperature than with catalysts containing higher Ni-loadings and also Mg and/or Zn ions. Ethanol steam reforming occurs at lower temperature than phenol steam reforming and does not seem to be much hindered by the presence of phenol. Phenol steam reforming in the presence of ethanol starts after, but is highly selective to COx and H2. At low temperature, however, alkylation of phenol mainly occurs over the 5% Ni-Al2O3 catalyst to give mostly o-ethylphenol. Active ethoxide, acetate and phenate species are observed on the surface.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlight► Steam reforming of ethanol–phenol mixture is studied as model of biomass tar SR. ► Ethanol–phenol mixture is completely steam reformed over Ni–alumina at 800–900 K. ► Phenol SR occurs at higher T than ethanol SR but is very selective to COx + H2. ► Over low loading Ni–alumina phenol alkylation by ethanol occurs at T < 800 K. ► Ethoxide and phenate species appear to act as active intermediates.