n-butane isomerization on tungsten oxide supported on zirconia Original Research Article

Tungsten oxide supported on zirconia catalysts prepared from ammonium metatungstate as a precursor and using different preparation routes were tested for n-butane isomerization at atmospheric pressure, 300°C, WHSV=1 h−1 and H2/nC4=6. The diffusion of polytungstates through the pores of Zr(OH)4 is sterically hindered due to the size of the anion. As a result of this, low penetration and the agglomeration in pore mouth are possible. The obtention and further utilization of polytungstates with a lower number of W atoms improve the distributions of W on ZrO2 surface and the catalytic activity. After calcination at 800°C, the better WO3/ZrO2 catalyst showed a catalytic performance similar to sulfated zirconia calcined at 620°C and corresponded to a material with well dispersed W. The more dispersed and active catalyst was obtained with an ammonium metatungstate solution stabilized 7 days at pH 6 before Zr(OH)4 impregnation, containing 15% W.