Estudo termodinâmico e experimental da produção de hidrogênio a partir das reações de reforma a vapor e oxidativa do gás liquefeito de petróleo usando precursores do tipo Perovskita

Abstract

The transformation of liquefied petroleum gas (LPG) in hydrogen has gained importance due to the interest in the viability of the fuel cell system. However, operating conditions and the specific use of active and resistant catalysts is a challenge. Thus, one aim of this thesis was to evaluate thermodynamically conditions such as temperature, feed ratio, energy demand, excess water and oxygen in the feed in order to obtain operational data that maximize hydrogen production and minimize the coke amount. The thermodynamic results showed that independent feeding, hydrogen production is favored with increasing temperature and that the use of lower temperatures favors the coke production (C (s)). The addition of unsaturated compounds in the feed of LPG did not cause significant differences in the composition of the gas phase, so the LPG can experimentally be considered only as a mixture containing C3H8 and C4H10. The addition of excess water and oxygen to the system was required in order to produce low coke levels and higher conversion to H2 in equilibrium. In addition, was evaluated experimentally with catalysts precursors with perovkite like La1-x CexNiO3 (x = 0, 0.05, 0.1) and La1-xSrxNiO3 (x = 0, 0.05, 0.1) prepared by the methods of precipitation in the reactions of steam and oxidative reforming LPG. The set of characterization techniques showed that the perovskite structure is the main phase obtained after calcination for all samples. In addition, cerium-doped samples showed lower particle diameter of nickel and metal dispersion values larger compared to the samples containing strontium. The results of temperature-programmed reduction and the ability to storage oxygen showed that the samples containing cerium showed higher storage capacity and reduction of oxygen. All characterization results are in agreement with the catalytic tests, because samples containing cerium showed higher activity and stability during the steam and oxidative reactions reforming of LPG. Among the catalysts, the most promising was the composition with La0,95Ce0,05NiO3 which was more active and resistant, due to small substitution of lanthanum cerium which contributed significantly in the activity and stability of this material. The oxidative reforming of LPG showed a better activity and hydrogen formation compared to steam reforming. The addition of a small amount of oxygen to the reactive power provided greater resistance to deactivation which contributed to the better performance of the samples.