Au/TiO 2 (1wt% Au), Cu/TiO 2 (1wt% Cu) and AuCu/TiO 2 (1wt% AuCu) catalysts with different Au:Cu mass ratios were prepared in one-step synthesis using sodium borohydride as reducing agent. The resulting catalysts were characterized by X-ray diffraction (XRD), X-ray Dispersive Energy (EDX), Transmission Electron Microscopy (TEM) and Temperature Programmed Reduction (TPR) and tested for the preferential oxidation of carbon monoxide (CO-PROX reaction) in H 2-rich gases. EDS analysis showed that the Au contents are close to the nominal values whereas for Cu these values are always lower. X-ray diffractograms showed only the peaks of TiO 2 phase; no peaks of metallic Au and Cu species or oxides phases were observed. TPR and high-resolution TEM analysis showed that AuCu/TiO 2 catalysts exhibited most of Au in the metallic form with particles sizes in the range of 3-5 nm and that Cu was found in the form of oxide in close contact with the Au nanoparticles and well spread over the TiO 2 surface. The AuCu/TiO 2 catalysts exhibited good performance in the range of 75-100 °C and presented a better catalytic activity when compared to the monometallic ones. A maximum CO conversion of 98.4% with a CO 2 selectivity of 47% was obtained for Au 0.50 Cu 0.50 /TiO 2 catalyst at 100 o C.

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.

ALENCAR, Catarine. S. L. Preparation of AuCu/TiO2 catalysts by different methodologies for preferential carbon monoxide oxidation. 2020. 97 p. Dissertação (Mestrado em Tecnologia Nuclear)-Instituto de Pesquisas Energéticas e Nucleares-IPEN-CNEN/SP. São Paulo. The preferential oxidation of CO in H2-rich mixtures (CO-PROX reaction) has been considered very promising for H2 purification, reducing CO level below 50 ppm and allowing its use in Proton Exchange Membrane Fuel Cell (PEMFC). 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 ºC and 80 ºC; however, the catalytic activity strongly depends on the preparation method. In addition, the addition of Cu to Au/TiO2 catalyst could increase the activity and selectivity for CO-PROX reaction. In this work, AuCu/TiO2 catalysts were prepared by two methodologies using borohydride as reducing agent and electron beam irradiation. Using the borohydride reduction method AuCu/TiO2 catalysts with different compositions of Au and Cu were prepared in one-step synthesis where Au 3+ and Cu 2+ ions were dissolved in water and reduced using sodium borohydride in the presence of TiO2 support. In a similar way, using electron beam irradiation, Au 3+ and Cu 2+ ions were dissolved in a water/2-propanol solution and irradiated in the presence of TiO2 support at room temperature using different dose rates (kGy s-1) and irradiation time (s). The catalysts prepared by borohydride reduction showed Au nanoparticles with sizes in the range of 3-5 nm and a good dispersion onTiO2 support, resulting in a good catalytic activity. The addition of Cu to Au/TiO2 catalyst in certain proportions increased CO conversion and CO2 selectivity, proving that the addition of a second metal had a promoting effect for CO-PROX reaction. The catalysts prepared by electron beam irradiation showed large Au nanoparticles sizes (> 10 nm) and low dispersion on TiO2 support resulting in low CO conversions and CO2 selectivity.