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.  


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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