75. Byrd, Adam J.; Gupta, Ram B.. Stability of cerium-modified .gamma.-alumina catalyst support in supercritical
water. Applied Catalysis, A: General (2010), 381(1-2),
177-182.
Abstract
Supercritical water (above 374.1 oC
and 220.6 bar) is emerging as a promising medium to
carry out a variety of catalytic reactions, including reforming to produce
hydrogen. However, when using a
heterogeneous catalyst the support material can undergo transformations in the
hydrothermal environment. In this work
the stability of .gamma.-Al2O3 modified with 1-10 wt% Ce
in supercrit. water is examd., specifically in the temp. range
of 500-700 C at 246 bar. Transformations
of the .gamma.-phase were slowed but not prevented. Based on X-ray anal., the transformation of
.gamma.-Al2O3 proceeded through the .kappa. phase
toward the stable .alpha. phase. Reduced cerium species were seen to be
oxidized in the supercrit. water
environment, and low Ce-loading supports maintained
the highest BET surface areas. The
stabilization was greatest at 700 C, where Ce-modified
aluminas retained significantly higher sp. surface
areas than unmodified alumina.
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