Transmission μ-FT-IR Cell for Boundary Layer Studies

Abstract

Recently the present authors described a novel reflectance μ-FT-IR cell for the study of catalyst surfaces (and adsorbates thereon) with spatial resolution. Here, details are given of a transmission μ-FT-IR cell for on-line spatially resolved studies of boundary layers (and oscillatory behavior) produced around a Pt wire during its catalysis of CO oxidation. The CO–O₂ reaction has been followed in terms of absorption at 2180 cm_-1 and energy emission over the IR range and may (1) involve a boundary layer at 1–2 mm out from the Pt wire surface at a Reynolds number of 1064; (2) vary in rate with the microchemistry (or surface temperature) of the Pt wire surface along its length; and (3) show oscillations in rate, which depend upon position in the reactant flow relative to the catalyst surface but which are far more substantial in amplitude than previously suspected, possibly because the wire is not averaging over unsynchronized reaction domains but is partially resolving these spatially. Some restructuring of the Pt wire is seen as a result of the reaction, in line with expectation.