Abstract
The major part of the world production of hydrogen (H2) is originated from a combination of methane steam reforming and water-gas shift reaction resulting in an H2-rich mixture known as reformate gas, which contains about 1% vol (10,000 ppm) of carbon monoxide (CO). The preferential oxidation reaction of CO in H2-rich mixtures (CO-PROX) has been considered a very promising process for H2 purification, reducing CO for values below 50 ppm allowing its use in PEMFC Fuel Cells. Au nanoparticles supported on TiO2 (Au/TiO2) catalysts have been shown good activity and selectivity for CO-PROX reaction in the temperature range between 20-80 ºC; however, the catalytic activity strongly depends on the preparation method. Also, the addition of Cu to the Au/TiO2 catalyst could increase the activity and selectivity for CO-PROX reaction. In this work, AuCu/TiO2 catalysts with composition 0.5%Au0.5%Cu/TiO2 were prepared in a single step using electron beam irradiation, where the Au3+ and Cu2+ ions were dissolved in water/2-propanol solution, the TiO2 support was dispersed and the obtained mixture was irradiated under stirring at room temperature using different dose rates (8 – 64 kGy s-1) and total doses (144 – 576 kGy). The catalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction transmission electron microscopy, temperature-programmed reduction and tested for CO-PROX reaction. The best result was obtained with a catalyst prepared with a dose rate of 64 kGy s-1 and a total dose of 576 kGy showed a CO conversion of 45% and a CO2 selectivity of 30% at 150 oC.
Highlights
Hydrogen gas is mainly produced by methane steam reforming and water-gas-shift processes representing 48% of world production [1]
Among the catalysts used for the carbon monoxide (CO)-PROX reaction, the Au/TiO2 (Au nanoparticles supported on TiO2) catalysts have been shown good activity and selectivity for CO-PROX reaction at low temperatures
The chemical composition of the catalysts was determined by X-ray dispersive energy (EDX) using a JEOL analytical scanning microscope, model JSM-6010LA with a 20 kV electron beam equipped with a multi-channel analyzer localized in Centro de células a combustível e hidrogênio (CCCH)
Summary
Hydrogen gas is mainly produced by methane steam reforming and water-gas-shift processes representing 48% of world production [1]. Among the catalysts used for the CO-PROX reaction, the Au/TiO2 (Au nanoparticles supported on TiO2) catalysts have been shown good activity and selectivity for CO-PROX reaction at low temperatures (in the range of 20 oC to 100 oC). Kugai et al [12] prepared Pt and PtCu bimetallic catalyst supported on CeO2 using electron beam irradiation for CO-PROX reaction and observed that Pt-Cu showed activity in low temperatures compared to monometallic Pt catalyst while keeping high CO2 selectivity. AuCu/TiO2 catalysts were prepared in a single step by simultaneous reduction of Au(III) and Cu(II) ions in the presence of the TiO2 support using the water/2-propanol solution as reaction medium. The dose rate and total dose were varied and the obtained AuCu/TiO2 catalysts were tested for CO-PROX reaction
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