Valence State Change And Resistance To Temperature Changes Of CuO/CeO₂Catalysts In CO-PROX

Stable power generation of proton exchange membrane fuel cell (PEMFC) requireshighly pure H2with very low CO contents (＜100ppm). CO preferential oxidation(CO-PROX) is one of the effective methods that can remove CO in industrial hydrogen richgas. The CuO/CeO2system is an effective catalyst for this reaction. In this context, theprincipal aim of this work is to evaluate the performance of CuO/CeO2catalysts preparedby impregnation for the CO-PROX reaction in excess of hydrogen. Atomic ratio of Cu/Ce,sample mass, temperature changes and the presence of CO2will be discussed on thecatalytic activity. The degree of reduction of the catalysts during different reactions will bealso investigated. The main contents are as follows:(1) CuO/CeO2catalysts were prepared by impregnation method. Cu/Ce atomic ratiowere set to5%,10%,15%,30%. Calcination temperature was600oC. Continuouslyascending reaction, continuously descending reaction and one-point reaction of the catalystswere investigated in simulated hydrogen rich gas (without CO2). Experimental results showthat, conversion of CO could reach100%at120oC when the sample mass was200mg. Thecatalyst of Cu/Ce atomic ratio of10%had optimal catalytic performance. Through TPRcharacterization of the sample after CO-PROX reaction we could know that, catalysts werereduced in different degree with the changes of temperature and Cu/Ce atomic ratio.(2) In simulated hydrogen rich gas (with CO2), the catalytic activities of samples withdifferent Cu/Ce atomic ratio in different reactions such as continuously increasing,continuously decreasing, increasing and decreasing in a row were discussed. The resultsshow that, CO conversion at low temperatures was significantly reduced when CO2wasadded in the reaction mixture. In general, at reaction temperature of80-100oC, thecontinuously decreasing reaction had a higher CO conversion than continuously increasingreaction. Analysis of TPR after continuous reaction showed that, the state of catalyst incontinuously decreasing reaction was more complex than that in continuously increasingreaction. TPR peak area shows that, during continuously increasing reaction, copper oxidereduced when CO2was added to the reaction gas was less than that without CO2。...