Caracterização e comportamento térmico de gomas de gasolina depositadas em veículos automotivos.

Abstract

The instability of the hydrocarbons and the presence of unsaturated composites, especially in the gasoline, may provoke an oxidation process constituting a product known as gasoline gum. This new product can be defined as a resinous material, formed by extensive carbonic chain molecules which tend to precipitate and to deposit itself in the fuel distribution system, prejudicing the perfect functioning of the vehicle’s engine. This work aimed to characterize and to understand the composition of these materials, beyond studying their thermal behavior. Four samples of gasoline gums generated in parts of different automotives vehicles (G1, G2, G3 and G4) were collected and analyzed through the IV, UV-Vile, XRD, TG/DTG techniques. It was also compared and characterized two types of gasoline of different origins (GASA and GASC). The achieved results of color, text of AEAC and distillation octane number tests were in agreement with the specified limits of the ANP nº 005/2001, constant in Portaria ANP n º 309. However, only the gasoline (GASA) was disapproved by the aspect, due to the impurities presented. The XRD results had disclosed that the gums had presented crystalinity due to the presence of iron and nickel that constitute the parts of where the gums had been removed. It was also observed that the structure of the gums presents several organic functions, as aromatic, peroxides, and products of the oxidation of the gasoline as carboxylic acid, and presence of metals like iron and nickel. Relatively to the thermal behavior, the G2 gum extracted from the combustion chamber generated by the activated gasoline, presented a lower thermal stability in comparison to the another ones. It is important to observe that the gums of the G1 e G4 pistons are thermally more unstable than the extracted gums of the admission valves.