Preferential CO Oxidation Over Ru/Al₂O₃-Coated Metal Monolith Catalyst for Small-Scale Fuel Processor

Abstract

Ru/Al₂O₃-coated FeCralloy monolith catalyst was applied for the preferential CO oxidation (PrOx) to reduce CO concentration less than 10 ppm in reforming process. FeCralloy monolith was pre-calcined at 900 °C after electrochemical surface treatment which results in the formation of uniform Al₂O₃ layer on the metal substrate. Pre-calcined monolith was coated with 10 wt% Al₂O₃ sol and followed by 1.2 wt% Ru/Al₂O₃ catalyst washcoating. The highly dispersed 1.2 wt% Ru/Al₂O₃ catalyst was prepared by the deposition-precipitation method using 5 wt% NaOH solution as a precipitant. The characterization as to surface area, metal dispersion, and reduction temperature of catalysts were analyzed by BET, CO-chemisorption and H₂-TPR. PrOx test was performed with GHSV of 5,000–30,000 h⁻¹ at 100–200 °C. The λ(2[O₂]/[CO]) was adjusted between 1 and 2 and the effect of H₂O and CO₂ was examined at λ = 2. As a result, the metal dispersion of Ru coated on the FeCralloy monolith is higher than that of commercial pellet catalyst with the shape of sphere. The monolith catalyst shows higher CO conversion and CO₂ selectivity than the commercial catalyst due to the enhancement of thermal conductivity and the maximization of available Ru active site on the metal substrate. In addition, monolith catalyst has a superior tolerance to H₂O and CO₂. From this study, it is found that the Ru/Al₂O₃-coated monolith catalyst shows robust catalytic activity with 100 % CO conversion and 50 % CO₂ selectivity under 0.61 % CO, 0.61 % O₂, 59 % H₂, 19 % H₂O, 16 % CO₂, N₂ balance at GHSV = 5,000 h⁻¹ from 100 to 160 °C in PrOx.