Aplicação de catalisadores bifuncionais Ni/Nb2O5 para obtenção de hidrocarbonetos renováveis a partir dos processos de pirólise e hidrodesoxigenação/hidroisomerização de óleo de vegetais

Abstract

The replacement of fossil fuels with renewable fuels is the most viable option for the sustainable growth of the aviation sector. Therefore, it is necessary to investigate conversion processes, sustainable raw materials, and catalysts that enable large-scale production at a competitive cost. This study aims to obtain renewable hydrocarbons for aviation through hydrodeoxygenation/hydroisomerization and thermal/thermocatalytic pyrolysis of vegetable oils using the Ni/Nb2O5 catalyst. The catalysts were prepared via wet impregnation. Characterization indicated that these materials exhibit a crystalline and mesoporous structure, with weak to moderate acidity, making them promising for application in these thermochemical processes. Initially, the activity of the catalysts for the hydroisomerization of n-hexadecane was verified. The catalysts showed conversion rates of 57.6% and 68%, and selectivity of 61.9% and 58.2% for the 10%Ni/Nb2O5 and 20%Ni/Nb2O5 catalysts, respectively. Subsequently, the performance of the catalysts in the hydrodeoxygenation process of hexadecanoic acid was evaluated, in which they also showed excellent activity, with a conversion rate of 100% and selectivity of 93% and 87.8% for hydrodeoxygenation products. At this stage, the formation of isoparaffins was also observed, demonstrating the activity of the catalysts for simultaneous deoxygenation and isomerization. Pupunha proved to be a promising raw material source for the production of aviation biofuel, as it showed an oil content of 25.56%, a fatty acid composition within the aviation kerosene range, as well as high thermal and oxidative stability. In the hydrodeoxygenation tests of hydrolyzed pupunha oil, the 10%Ni/Nb2O5 and 20%Ni/Nb2O5 catalysts achieved conversion rates of 91.4% and 99.9%, respectively, with selectivity of 77.0% and 87.7%, presenting a final product with 37.4% and 43.8% paraffins within the carbon range of aviation biofuel in its composition. The performance of the catalysts in the pyrolysis process was also evaluated. The tests were conducted at 500°C under a nitrogen flow. The Ni/Nb2O5 catalysts demonstrated deoxygenation activity, producing a bio-oil with up to 80.8% hydrocarbons and liquid product yields exceeding 74%.