Mitigation of hydrogen by oxidation using nitrous oxide and noble metal catalysts

Abstract

This test studied the ability of a blend of nuclear-grade, noble-metal catalysts to catalyze a hydrogen/nitrous oxide reaction in an effort to mitigate a potential hydrogen (H{sub 2}) gas buildup in the Hanford Site Grout Disposal Facility. For gases having H{sub 2} and a stoichiometric excess of either nitrous oxide or oxygen, the catalyst blend can effectively catalyze the H{sub 2} oxidation reaction at a rate exceeding 380 {mu}moles of H{sub 2} per hour per gram of catalyst ({mu}mol/h/g) and leave the gas with less than a 0.15 residual H{sub 2} Concentration. This holds true in gases with up to 2.25% water vapor and 0.1% methane. This should also hold true for gases with up to 0.1% carbon monoxide (CO) but only until the catalyst is exposed to enough CO to block the catalytic sites and stop the reaction. Gases with ammonia up to 1% may be slightly inhibited but can have reaction rates greater than 250 {mu}mol/h/g with less than a 0.20% residual H{sub 2} concentration. The mechanism for CO poisoning of the catalyst is the chemisorption of CO to the active catalyst sites. The CO sorption capacity (SC) of the catalyst is the total amount of CO that the catalyst will chemisorb. The average SC for virgin catalyst was determined to be 19.3 {plus_minus} 2.0 {mu}moles of CO chemisorbed to each gram of catalyst ({mu}mol/g). The average SC for catalyst regenerated with air was 17.3 {plus_minus} 1.9 {mu}mol/g.