USING (CO)-C-13 AND (OO)-O-18-O-18 TRACERS TO STUDY THE REMOVAL OF PARTS-PER-MILLION CO AND O-2 FROM N-2 OVER A NI-AL2O3 CATALYST

The removal of parts per million of CO and O-2 from nitrogen over a co mmercial Ni-Al2O3 catalyst was studied using either (CO)-C-13 or (OO)- O-18-O-18 as a chemical tracer. An atmospheric pressure ionization mas s spectrometer (APIMS) was used to analyze the impurities in nitrogen. This highly sensitive instrument was able to quantify the impurities to concentration levels below parts per billion. The tracer experiment s permitted a determination of the actual performance of the Ni-purifi er since the APIMS distinguished the feed O-2 (i.e., (OO)-O-18-O-18) f rom the background O-2 and quantified CO (i.e., (CO)-C-13) in the pres ence of N-2. The experiments demonstrated that the concentration of th ese impurities in the product nitrogen could be controlled to below 10 0 parts per trillion, a level that is expected to be required for futu re semiconductor manufacturing. The results also provided some insight s on the oxidation mechanism, suggesting the exchange of the O atom be tween the adsorbed CO anti the adsorbed O-2.