-High temperature CO oxidation kinetics-

Figure 1: Conversion (a) and corresponding Turnover Frequency (b) plots
for monolithic catalysts consisting of Pd on two types of alumina
(Sasol TH100-150 and TH500) at various washcoat and Pd loadings

CO oxidation over supported noble catalysts – despite being one of the most highly studied catalytic reactions – is fraught with contradictory kinetic data in the literature, largely owing to the difficulty of obtaining intrinsic kinetics in the absence of both washcoat and external phase heat and mass transfer effects. For automotive catalysts, where CO oxidation controls catalyst light-off, it is important to enhance kinetics while minimizing pore diffusion effects in the monolith washcoat. We investigate kinetics of CO oxidation over a model automotive monolith catalyst free of pore-diffusion effects. Data were obtained on a single-channel monolithic catalyst coated with Pd/Al2O3. Pure chemical kinetics were obtained by operating with low CO concentrations at volumetric space velocities of ca 1.5x106 h-1 (STP), and by utilizing a small channel diameter, thin washcoat layer of wide-pore alumina, and low Pd loading. Fig. 1 displays the light-off data for samples with varying quantities of catalyst, presented both as conversion and turnover frequency data. Results of this work point to advantages of the single-channel monolith reactor for obtaining kinetics of fast, highly-exothermic catalytic reactions under conditions of negligible heat and mass transfer influence, and also provide guidance for designing fast light-off automotive exhaust catalysts