Extrato fenólico renovável a partir da carbonização da Jurema Preta (Mimosa tenuiflora)

Abstract

Carbonization is a thermochemical process of converting biomass into energy, with neutral CO2 emissions. However, one of the biggest challenges of this process is to make it sustainable, since two products other than charcoal are produced: gas and liquid. The gas, mostly CH4, CO, CO2 and H2, is easy to reuse considering it can be used to heat the system itself. The liquid, also called pyroligneous acid, has high chemical instability due to the complex composition, including toxic organic compounds, and cannot be used immediately after collection or dumped into the environment without prior treatment. This work aims to characterize a distilled fraction obtained from the carbonization of Jurema Preta (Mimosa tenuiflora), and to evaluate its commercial potential according to the results obtained for the valorization of this by-product. Solid biomass was characterized by proximate analysis (moisture, volatiles, ash and fixed carbon content), thermogravimetric analysis (TGA), and analytical pyrolysis coupled to a gas chromatograph (Py-GC/MS) to identify the pyrolysis products in different temperatures. The fractions of pyroligneous extract obtained in the commercial carbonization process in the region of Acari (RN) at 300 and 400 °C were rotoevaporated at 75 °C under vacuum, then extracted with dichloromethane and methanol for further analysis by gas chromatography coupled with a spectrometer mass analysis (GC-MS), and nuclear magnetic resonance (NMR) spectroscopy. The results show that Mimosa tenuiflora's pyroligneous extract is rich in acetic acid and phenolic compounds. The solvents used, dichloromethane and methanol, were able to separate and concentrate a phase rich in phenolic compounds and a phase containing organic acids, respectively. The highest yield of phenolic compounds was reached at a temperature of 300 °C with 70% purity after extraction with dichloromethane. An extract containing approximately 92% acetic acid was obtained at the same temperature of 300 °C after extraction with methanol of the non-dichloromethanerelated phase. The extraction method used was efficient in the separation of extracts containing important chemicals for industry and from a renewable origin, obtained from a byproduct of the carbonization process, characterizing it as a green product.