Influence of alumina addition on structural and catalytic properties of sulphated zirconia in isomerization of n-hexane
2021
New binary catalytic systems based on sulphated zirconia-alumina were
synthesized by controlled hydrolysis of alkoxides using relative molar
ratios of constituents 1:1, 1:2 and 1:3 in favour of zirconia. The obtained
differences in the final catalytic material’s properties may be related to
organic precursor memory effect, the applied calcinations temperatures and
used alumina contents. The addition of alumina to zirconia affected the
structural and surface properties stabilizing bare zirconia by means of
slower phase transformation of tetragonal zirconia crystal phase into
monoclinic one, further resulting in smaller crystallites sizes and higher
surface density of acidic function (sulphates). The best alumina impact on
physico-chemical properties was achieved when the highest amount of alumina
(e.g. 50%) and lower calcination temperature (500°C) were used, causing
relatively high steady-state activity in isomerization of n-hexane at
reaction temperature 250 °C. On the other hand, higher calcination
temperature (600 °C) played a role in the genesis of greater sulphate
density. Catalytic activity and selectivity are expressed as a complex
synergistic function of relative density of acid sites together with
positive status of other optimized physico-chemical properties of the
catalytic material (by activation and calcination temperatures).
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