N-BUTANE ISOMERIZATION ON TUNGSTEN-OXIDE SUPPORTED ON ZIRCONIA

Tungsten oxide supported on zirconia catalysts prepared from ammonium metatungstate as a precursor and using different preparation routes we re tested for n-butane isomerization at atmospheric pressure, 300 degr ees C, WHSV=1 h(-1) and H-2/nC(4)=6. The diffusion of polytungstates t hrough the pores of Zr(OH)(4) is sterically hindered due to the size o f the anion. As a result of this, low penetration and the agglomeratio n in pore mouth are possible. The obtention and further utilization of polytungstates with a lower number of W atoms improve the distributio ns of W on ZrO2 surface and the catalytic activity. After calcination at 800 degrees C, the better WO3/ZrO2 catalyst showed a catalytic perf ormance similar to sulfated zirconia calcined at 620 degrees C and cor responded to a material with well dispersed W. The more dispersed and active catalyst was obtained with an ammonium metatungstate solution s tabilized 7 days at pH 6 before Zr(OH)(4) impregnation, containing 15% W. (C) 1997 Elsevier Science B.V.