Evaluation of the use of Gossypium hirsutum oil and supercritical ethanol for the production of ethyl esters in non‐catalytic process

Abstract

The search for new sources of energy requires more and more interaction between the economical and technological viabilities associated with social development, increasing, in this manner, the interest in raw materials that generate regional development. Thus, this work analyzed the viability of ethyl esters production (biodiesel) from Gossypium hirsutum L. (cottonseed oil) without the use of a catalyst, in a continuous supercritical reactor. The reactions occurred at a tubular reactor, under 15 MPa and 20 MPa of pressure, reaction time (3.75–50 min), molar ratio of oil:alcohol (1:30–1:50), and temperature (250–400 °C). The maximum yield obtained was 75.05 % at 375 °C, under 20 or 15 MPa of pressure, molar ratio of oil:ethanol 1:40, and reaction times 30 and 40 min, respectively. A significant influence of the temperature on yield in esters was verified, but there was also thermal degradation under high temperatures, which caused a decrease in the ester's yield. The high content of polyunsaturated acids present in cotton oil possibly hampered the process of transesterification in long periods of reaction time and high temperatures.