Estudo teórico da etapa térmica do processo de Claus utilizando metadinâmica e dinâmica molecular de Car-Parrinello

Abstract

The decline in fossil fuel reserves results in increased use of energy sources with a high content of substances harmful to human health and the environment.

Among these substances is hydrogen sulphide. The use of hydrogen sulphide- containing fuels results in the formation of acid gases, which affect the ozone

layer, and the production of acid precipitation. Exposure to hydrogen sulfide gas can be fatal to animal life: human or not. A suitable and efficient method is necessary for the treatment of fuels containing high concentration of hydrogen sulphide. The most widely used method for the treatment of hydrogen sulphide is the controlled oxidation known as the Claus process. The present work had as objective the study of the chemical reaction that occurs between oxygen and hydrogen sulfide, at molecular level, at temperatures above 1100 K, thus

simulating the thermal phase of the Claus process. For this purpose, Car- Parrinello's ab initio molecular dynamics technique was used along with

metadynamics. During the simulation, which had the approximate time of 7.4 picoseconds, 8 reactions were observed. Among the reactions observed, two differ from the mechanisms proposed in the literature: the formation of HSO and the formation of HO2. The presence of the ozone molecule in the reaction medium, too, was not reported in the researched literature. Through the metadynamics performed for the ozone formation reaction the Arrhenius reaction constant was calculated.