Artigo 16 – Vol. 6 N. 3


ANALYSIS OF THERMO-OXIDATIVE STABILITY OF LUBRICANT OIL CONTAMINATED WITH BIODIESEL

Autores
T.F. Oliveira, M.L.Campello, J.Dweck
Recebido em
 27 de Agosto de 2017
Aceito em
 10 de Setembro de 2017
Publicado em
 30 de Setembro de 2017
DOI
 10.18362/bjta.v6.i3.16
Páginas
Keywords
lubricant oil, biodiesel contamination, thermo-oxidative stability

 

Resumo

The higher is the biodiesel content in diesel, the greater is its remaining fraction in the liquid state, which can migrate to the lubricant reservoir contaminating it. Many field trials using lubricants contaminated with biodiesel indicate changes in their important properties such as anti-wear and anti-rust ones. Thus, considering the thermal condition to which lubricants are submitted in engines, changes in their physical-chemical properties may occur, reducing their lubrication efficiency. The objective of this study was to analyze the thermal behavior and the thermo-oxidative stability of biodiesel and lubricant blends, simulating differently contaminated lubricant states, by thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA). The thermo-oxidative stability temperatures were determined by three different ways, two of which take into account the onset of the liquid phase oxidation identified by the first exothermic DTA peak, which occurs before the lubricant auto-ignition DTA peak. Activation energy determinations, at respective initial degrees of conversion, were also estimated for the various contamination levels, to better evaluate the oxidation process. The results indicate that the lubricant contaminated with biodiesel has a significant decrease in its oxidative stability compared to the non-contaminated one. In the studied case, up to 6.5% biodiesel contamination, the thermo-oxidative stability is determined by the onset temperature of the oxidized light components volatilization. For higher contamination levels, it is determined by the onset temperature of the heavier components oxidation in liquid phase. Thus, the higher is the contamination level, the lower is the lubricant initial oxidation temperature and shorter will be its useful life in diesel engines submitted to much higher temperatures.
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