The simultaneous measurement of support, metal, and gas phase temperatures using an in situ IR spectroscopic technique

Abstract

An in situ infrared technique has been developed and used for the simultaneous measurement of gas phase, support, and metal temperatures. This technique yields more realistic and consistent values for reaction temperatures than gas phase or mechanically attached microscopic surface thermocouples. The technique relies on monitoring the temperature-dependent vibrational frequencies of the catalyst support material during reaction. The support vibrational frequencies are calibrated with temperature. This enables one to determine the support temperature during reaction. A 1% Pt SiO 2 catalyst using the oscillatory oxidation of CO as a reaction probe was used to understand the nature of heat transfer between the metal and the support. The results show that surface temperature oscillations are in phase with CO 2 formation. The resolution of the technique has been shown to be ± 7 °C, depending on the absorption frequency selected. Actual metal temperatures for a thin Pt film sample were determined by in situ resistivity measurements. In most cases the metal-surface temperature gradient was found to be less than the resolution of the IR technique.