(539d) Kinetics, Self-Similar Crystallite Size Distributions, and the Mechanism of Catalyst Sintering

Sintering of supported metal catalysts
is a primary cause for deactivation at high temperatures. The study of its kinetics
and of the changes in crystallite size distribution has been the subject of
different studies in our group [1,2], and we have been able to show that
apparent inconsistencies between leading models and experimental data were caused
by limitations implicit to the models. We have developed improved models and equations
both for the analysis of global kinetics and for the analysis of the
experimental crystallite size distributions that provide not only an excellent
match of the experimental data, but that have sound physical foundations.

In this work we analyze the sintering of
supported Pt, Pd and Ni catalysts, and discuss the conditions needed for the
observed crystallite size distributions to be a truly self ? similar solution
within the context of the Ostwald-ripening model. The implications for the
mechanism of sintering are also discussed in the light of the resulting fits.

Significance

We provide guidelines for the analysis
of sintering phenomena that can be useful in the design of more stable
catalysts.

References

1.      
Fuentes, G.A. and Gamas,
E.D., in ?Catalyst Deactivation 1991?, (C.H. Bartholomew and J.B. Butt, eds.),
Stud. Surf. Sci. Catal., vol. 68,  p. 637, Elsevier, Amsterdam, 1991.

2.      
Fuentes, G.A. and Salinas-Rodríguez,
E., in ?Catalyst Deactivation 2001?, (J.J. Spivey, G.W. Roberts and B.H. Davis,
eds.), Stud. Surf. Sci. Catal., vol. 139, pp. 503, Elsevier, Amsterdam, 2001.