Avaliação de catalisadores de nanotubos de titanato-metálico na conversão de CO2 a CO

Abstract

The reverse gas-water shift reaction (RWGS) can be used as an essential step in the transformation of CO2 into chemicals, which is attractive for CO2 mitigation. However, a major challenge for this process is the rational design of resistant catalysts with desirable CO selectivity. Therefore, this work aims at the synthesis of metal catalysts supported on titanate nanostructures (TNT), in order to evaluate their performance in the conversion of CO2 from RWGS. The TNT were synthesized by the hydrothermal method and, after being impregnated with different percentages of metal. The obtained catalysts were tested for RWGS in the temperature range of 450 to 700 ºC in a continuous fixed bed reactor. Among the metals tested (Cu, Co, Ni and Fe) in the RWGS reaction, copper showed the best performance, which was used for the other tests. Afterwards, an evaluation of different gaseous hourly space velocities (GHSV) 7500, 15000 and 30000 mL h-1 g-1 of catalyst was carried out, where the velocity of 15000 mL h-1 g-1 of catalyst presented the best result. New catalytic tests were carried out using catalysts decorated with different percentages of Cu and the GHSV of 15000 mL h-1 g-1 of catalyst, it was verified that 10% of copper obtained a good percentage of conversion for low temperature (33.6% at 500 ºC). Subsequently, TNT catalysts decorated with 10% copper by impregnation deposition and single atom methods were tested, given the similarity of catalytic performances, both were evaluated in terms of thermal stability, and showed good thermal stability (550 ºC) in the analyzed period (≈12 h). The catalyst obtained by the single atom method showed excellent catalytic behavior with a loss of less than 5% of CO2 conversion in the stability test. It should be noted that the CO selectivities obtained for all the tests carried out in this work were excellent, greater than 90%. Furthermore, the application of this set of catalysts is unprecedented for RWGS.