The study of the deactivation of water-pretreated Pt/γ-Al_2O_3 for low-temperature selective CO oxidation in hydrogen

摘要

The selective oxidation of carbon monoxide in a hydrogen-rich stream is an important reaction in fuel cell technology. Fuel cells that use hydrogen produced from a combustion source contain small amounts of CO that must be removed to extremely low levels (< 10 ppm), otherwise, it will poison the anode of the polymer electrolyte fuel cells (PEFC). Our research group has developed an improved Pt catalyst on alumina using a water-pretreatment method. However, at temperatures below 100℃, water from the hydrogen-oxidation side reaction accumulates on the catalyst causing it to deactivate. To better understand the deactivation, the water-pretreated catalyst was characterized at room temperature (28℃) and at 50℃ with various reaction conditions (O_2 and H_2O concentration) by analyzing the activity of the catalyst and by measuring the reactor temperature profile using an infrared (IR) camera. The IR images clearly showed a decrease in the reactor temperature over time indicating the deactivation of the catalyst. As the catalyst became more deactivated, the reactor temperature decreased, the H2 and CO conversions decreased, while the CO selectivity increased to nearly 100%.