Avaliação dos parâmetros da técnica de redução a temperatura programada (RPT) para catalisadores do tipo metal suportado

Abstract

The methods of monitoring a reaction with the programmed temperature form a class of techniques in which the reaction behavior of the catalyst can be observed while the temperature is linearly increased over time. Temperature programed reduction (TPR) has been used to obtain qualitative information on the reducibility of oxidized species, such as metal oxides dispersed in a support. In the area of catalysis, one of the main applications of the TPR technique is to monitor the consumption of hydrogen present in a gas stream, which passes through a solid catalyst, subjected to a linear increase in temperature. This technique has been used for having several applications, among them: to determine the temperature range in which the reduction of metallic precursors and metallic sites occurs, to reveal the possible interactions between the metalsupport. This interaction is generally observed in catalysts in which the metal is present in low concentrations and with high dispersion. Several parameters affect the programmed temperature reduction measures, with emphasis on flow and concentration of gas passing through the reactor, heating rate, sample mass and amount of reducible metal. The control of these parameters allows to obtain reproducible profiles and adequate to the quantitative treatment. Therefore, the objective of this work is to evaluate the ideal values of the main experimental variables associated with TPR techniques. Therefore, it becomes evident that the characterization of catalysts by TPR techniques is easy to be carried out from an experimental point of view, but requires an optimization of several experimental variables. The control of these parameters allows to obtain reproducible profiles and adequate to the quantitative treatment. Therefore, the objective of this work is to evaluate the ideal values of the main experimental variables associated with TPR techniques, using catalysts of the metal-supported type