Influência do íon cloreto na produção de hidrogênio por corrosão eletroquímica ácida acelerada utilizando H2SiF6

Abstract

One of the most important green energy technologies is the production of clean hydrogen from renewable resources. It is the most abundant element in the universe and in the process of its combustion a large amount of energy is released and as a by-product, only water. However, to be an efficient and sustainable fuel, it is necessary to develop means for its production, storage and use. As it is not in the free form in nature, to obtain it it is necessary to dissociate it from a primary source of energy such as, for example, hydrocarbons, biomass or water. An alternative method for generating H2 is acid electrochemical corrosion. This work aims to investigate the production of hydrogen using H2SiF6 under the influence of chloride ion and also the optimization of this production by the accelerated acid electrochemical corrosion method. The experiments were carried out using a system that consists of a batch reactor in which the metal and the acid solution are inserted. Experiments were carried out with solutions containing H2SiF6 diluted in H2O and H2SiF6 with NaCl solution (2 mol/L). As a source of iron, steel wool (carbon steel) was used. The reactor, which consisted of an Erlenmeyer flask closed with a stopper, was connected by a hose to the interior of a beaker filled with water immersed in a beaker also with water. As the gas was being produced, it exerted pressure on the water inside the beaker and the volume of gas produced can be obtained from the displaced level of water. The experiments were carried out according to a 23 factorial design, with the independent variables fraction, mass and time, and the volume of gas produced as the response variable, in order to determine which were the most significant variables in production, and an additional planning to determine the optimal production conditions. Thus, it was identified by factorial design 23 that the most significant variables were time, fraction and mass and that when adding NaCl there was an acceleration of production. By additional planning, the significant variables were fraction, mass and the coefficient of the parameter that has the mass squared. A monotonic surface was found, in which the curve only goes up or down, depending on the angle that is observed. For the response and contour surfaces, the highest yields were obtained by increasing the fraction and mass, but there were physical limitations such as the maximum fraction 1 and the maximum mass that could fit in the Erlenmeyer flask. A simple cost analysis was carried out and for fraction 0.3 and mass 1.5 g the solution of H2SiF6/NaCl represents a saving of 26.5% in relation to H2SiF6/H2O and with fraction 0.97 and mass of 2 g for H2SiF6/NaCl, there are savings of 1.91% in relation to a fraction of 0.9 and a mass of 2 g for H2SiF6/H2O. Gas analysis done in previous studies showed that it was 99% hydrogen and 1% air.