Biodiesel has been growing as an economic and environmentally advantageous fuel, as it has
lower production costs and lower emission of greenhouse gases. However, biodiesel shows
problems related to oxidation, due to its chemical composition. This affects its long-term
storage and fuel quality, making antioxidant additives indispensable for inhibiting the
oxidative process. These antioxidants can be of synthetic origin (petroleum derivatives) or
natural (vegetable biomass). Therefore, the present work aims to extract and test antioxidants
from cashew nut shell liquid (LCC) in the oxidative stabilization of biodiesel. Therefore,
determinations of the ideal time of soxhlet and thermal extractions, FTIR analyzes and
evaluation of the oxidative stability by Rancimat were carried out. Through FTIR analyses, it
was found that the 3rd cycle of extraction was sufficient to extract all the liquid, with an
average yield of 30.0%. For the thermal extraction of the laboratory technical LCC,
statistically the best extraction time was 60 minutes with 20.0% yield. The qualitative FTIR
analyzes of the extracted LCCs showed characteristic peaks of phenolic groups and organic
acids, showing differences in the intensities of the spectrum's absorption bands. The analysis
of oxidative stability showed an induction period (PI) of the press LCC of 8h40min, the
Soxhlet LCC of 10h35min and the Industrial technical LCC of 10h65min, all below the limit
established by the ANP (12h). The technical LCC extracted in the laboratory obtained
11h12min of PI, close to that recommended by the ANP, proving to be a promising natural
antioxidant. Cardanol showed satisfactory results with 25h22min, twice what the ANP
recommends. In this way, the cashew nut shell liquid showed important and promising results
as a natural antioxidant for biodiesel.
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