Cobalt Based Catalysts for CO Preferential Oxidation

**53**

**Chapter 4**

**Abstract**

contact between elements.

**1. Introduction**

CeO2 support, XPS, laser-Raman spectroscopy

Cobalt-Based Catalysts for CO

In this work, catalysts based on cobalt supported on ZrO2 and CeO2 and CoCeMnOx were studied for the CO preferential oxidation (COPrOx) in hydrogenrich stream able to feed fuel cells. Among them, the CoCeMnOx formulation showed the highest CO conversion at low temperatures, while the cobalt oxide supported on ceria presented the best selectivity toward CO2. The Co3O4 spinel was the active phase for the CO preferential oxidation detected in all catalysts. However, the CoOx-CeO2 and CoCeMnOx catalysts resulted more active than cobalt oxide supported on zirconia. The presence of ceria close to cobalt species promotes the redox properties and enhances the catalytic activity. In the CoCeMnOx catalyst prepared by coprecipitation, the incorporation of Mn represented an additional positive effect. The presence of Mn promoted the reoxidation of Co2+ to Co3+ and, consequently, the activity increased at low temperature. By X-ray diffraction (XRD) of CoOx-ZrO2 and the CoOx-CeO2 catalysts, the Co3O4 spinel and ZrO2 or CeO2 were identified in agreement with laser-Raman spectra. At the same time, the CoCeMnOx catalyst, prepared by coprecipitation of precursor salts, showed an incipient development of a new phase (Mn,Co)3O4 mixed spinel, due to the intimate

**Keywords:** COPrOx, (Mn,Co)3O4 mixed spinel, redox couple, CoCeMnOx,

this could contribute to the depletion of greenhouse gases [1–3].

The global demand for energy has been inexorably growing in the last decades. The increasing use of fossil fuels in order to generate energy causes serious problems to the environment due to the gaseous emissions. This fact has produced a global movement toward trying to remove the contaminants from combustion effluents. Besides, the exploration for alternatives to fossil fuels, biofuels or hydrogen as an energy vector, has gained an immediate and future significance because

Fuel cells are devices that are being actively developed, because they are power generation systems that can produce energy with significantly less impact on the environment. Among several types of fuel cells, proton exchange membrane fuel cells (H2-PEMC) are considered to be the most technically advanced for such application [4]. Hydrogen produced by means of the steam reforming or autothermal process of hydrocarbons or alcohols should contain less than 10 ppm of carbon monoxide before entering the cell since CO poisons the Pt anode of the fuel cells (**Figure 1**) [5, 6]. After the reforming step, the hydrogen production process

Preferential Oxidation

*Leticia E. Gómez and Alicia V. Boix*
