resumo: Este artigo estuda o emprego da composição probabilística para avaliar o desempenho de catalisadores automotivos com diferentes composições de materiais. Foram comparados catalisadores à base de óxidos mistos de cério e zircônio impregnados ou não com paládio, e aditivados ou não com alumina impregnada com lantânio. Cada catalisador foi analisado quanto à desativação térmica segundo diferentes condições de envelhecimento. A comparação foi baseada em sete critérios, nos quais cada um dos catalisadores recebeu uma pontuação em escala de Likert de cinco níveis. Para cada catalisador foi calculada a probabilidade de ser o preferido segundo cada critério. Os catalisadores foram, a seguir, ordenados segundo probabilidades de preferência conjunta segundo todos os critérios. palavras-chave: Catalisadores. Escala de Likert. Composição probabilística.Abstract: This paper studies the use of probabilistic composition to evaluate the performance of automotive catalysts with different compositions. The catalysts compared were formed of mixed oxides of cerium and zirconium impregnated or not with palladium, and with no additives or alumina impregnated with lanthanum. Each catalyst was examined for the thermal deactivation under different aging conditions. The comparison was based on seven criteria, in which each of the catalysts received a score in a Likert scale of five levels. For each catalyst was calculated the probability of being the most preferred according to each criterion. The catalysts were then ranked according to the joint probabilistic preference according to all the criteria.

Recebido em 2/2/11; aceito em 22/7/11; publicado na web em 30/9/11 THERMAL AGING EFFECT IN OXI-REDUCTION PROPERTIES AND CATALYTIC ACTIVITY OF CZ AND PD-CZ CATALYST. Automotive catalyst, using in Brazil since 1992, is a essential technology for vehicular emissions control. Noble metals are the active phase of these catalysts, and cerium zirconium mixed oxides (CZ), responsibles for the oxygen storage capacity (OSC), one of the most important aspect for the operational performance of the catalyst. In this context, the oxireduction properties analysis of CZ and Pd/CZ (palladium supported in CZ) system are the objective of this study, as well as, the impact of the thermal aging in the OSC. Aging consisted of treatments at 900 or 1200 °C, for 12 or 36 h, in oxidizing condition.