Produção de hidrogênio a partir da fração aquosa do bio-óleo utilizando óxidos mistos a base de lantânio e níquel

• Autor(a) principal: Resende, Karen Abreu
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFU
• Texto Completo: https://repositorio.ufu.br/handle/123456789/15218
• topic: Análise termodinâmica; Fração-aquosa; Perovskita; Reforma; Hidrogênio; Lantânio; Níquel; Thermodynamic analysis; Aqueous fraction; Perovskite; Reform; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA

The condensation of gases from the pyrolysis of biomass leads to a liquid compound called bio-oil. This oil can be divided into two fractions: one aqueous and another non-aqueous. The aqueous fraction does not have a high market value and it is usually discarded. But, this mixture has an immense amount of organic compounds, which causes it to be a potential renewable source of hydrogen. Due to the diversity of organic compounds founds in this aqueous fraction, model compounds have usually been used in the studies about this subject. Among the compounds used to represent the aqueous fraction of bio-oil, the acetic acid is the most popular. The reaction most cited in the literature for the production hydrogen from the aqueous fraction of bio-oil is steam reforming. Therefore, the objective of this dissertation is to investigate the production of hydrogen form the aqueous fraction of bio-oil. Initially the thermodynamic behavior of the reaction of steam reforming of the aqueous fraction of bio-oil was analyzed, in order to determine the best operating conditions. In this study two model compounds were used to represent this mixture: acetic acid and acetol. The aqueous fraction of a very specific type of bio-oil also was studied. The mole fractions on a dry basis were calculated at equilibrium using the Lagrangian approach. The data were obtained at different temperatures (400-1300K) and for various steam (S)/fuel(F) (S/F = 1-9) ratios. It was observed that the best operating condition to conduct a steam reforming reaction of these compounds is at high temperatures (above 850K) and a high S/F. After studying the thermodynamic behavior of this process, experimental tests were performed using acetic acid as a model compound. Nickel-based catalysts are traditionally studied for reforming reactions. An alternative to combine the high Ni content employed in catalysts for reforming reactions with desirable values of dispersion is to use perovskite-type precursors (LaNiO3) or pyrochlore (La2Zr2O7). In this work the following catalysts were tested: LaNiO3, La0.90Sm0.10NiO3, La0.90Pr0.10NiO3, La2Zr1.5Ni0.5O7 and La2Zr1.0Ni1.0O7 in the reaction of steam reforming of acetic acid. During the reaction the catalysts showed the formation of the same products: H2, CO, CH4, CO2, C3H6O, but with different values of selectivities. The three perovskite-type oxides presented the best selectivity for hydrogen, and the presence of Pr and Sm affected the catalytic performance just slightly. Due to the large accumulations of coke observed during the reaction of steam reforming, a small amount of O2 was added to the misture. The presence of this oxidant improved catalytic activity without reducing the amount of hydrogen produced. Furthermore, it helped to reduce the deposits of coke. The pyrochlore showed high degrees of deactivation and low selectivity for hydrogen in the two reactions studied.