Evaluation of the effect of Ni content on Ni/TiO₂ in the carbon dioxide methane reaction

In this work the synthesis of titania nano tubes (TiO₂-Nt) was performed using the hydrothermal synthesis method from commercial TiO₂. The nano materials were thermally stabilized at 500 degrees Celsius for 2 hours and impregnated with 5% Ni, 10% and 20% by weight using nickel nitrate hexahydrate (Aldrich, 99.999%) as the nickel precursor. An aliquot of the 20-Ni / TiO₂-Nt catalyst was impregnated with 1% Pd, additionally another Pd/TiO₂-Nt catalyst was prepared, in both cases palladium acetylacetonate (Aldrich, 99%) was used as a Pd precursor. The catalysts were calcined at 400 degrees Celsius for 1 h, with a heating ramp of 5 degrees Celsius per min and subsequently reduced in 5% H₂ / He flow at 450 degrees Celsius for one hour. The characterization of the nano catalysts was performed using various techniques: nitrogen adsorption-desorption (Bet), scanning electron microscopy, X-ray diffraction and programmed temperature reduction. The catalytic activity tests performed with the synthesized catalysts showed that the 20-Ni/TiO₂-Nt and Pd/TiO₂-Nt catalytic materials have a similar behavior between them in the conversion of CO₂ and is better than that of the rest of catalysts after 250 degrees Celsius, with a maximum conversion of approximately 50% to 325 degrees Celsius. However, the catalyst 10-Ni / TiO₂-Nt at 375 degrees Celsius showed a conversion of CO₂ close to 60% and decreased to 55% at the maximum reaction temperature. The point to highlight in these catalysts is the selectivity towards methane. It was observed in the samples of 20-Ni/TiO₂-Nt and of PdNi/TiO₂-Nt that have a high selectivity compared to the rest of the catalysts synthesized in this work. This behavior can be associated with a better dispersion of Ni as shown by scanning electron microscopy results. (Author)