Estudo da despolimerização da lignina obtida da fibra prensada do mesocarpo do dendê através da técnica de irradiação por micro-ondas

Abstract

Palm oil is currently the most widely grown oilseed in the world, with the highest productivity of oil per planted hectare (3-6 ton oil / ha) and accounting for approximately 22% of world production of vegetable oils. In its extraction process several coproducts are produced. Some of them go directly to a specific market, while others still need to be submitted to evaluation processes to increase their market values . One of these coproducts is pressed fiber pith of palm oil, used primarily as fuel for heating boilers. However this fiber is an important source of lignocellulosic biomass, consisting of 30% lignin. Lignin is the second most abundant natural polymer in the planet and its polyphenolic structure gives it the potential to be used as a promising and economically viable source of aromatic compounds in the oil replacement, the main source of these compounds nowadays. The search for renewable sources of aromatic raw materials has been a major focus within the green chemistry. In this sense to add value and maximize the potential of that biomass, this paper obtained lignin from the fiber pith of palm oil through the pulping method acetosolv followed by extraction of fatty acids by washing with hexane. The obtained lignin was fully characterized physically and chemically and it showed high level of purity (90.28%), glass transition temperature of 133,79ºC and initial degradation temperature around 350 ° C. The absorption bands in FTIR spectra were consistent with the proposed structure of lignin and the obtained signals in the NMR spectrum. The recovered lignin was heated by microwave irradiation under different temperature conditions, solvents and catalysts in order to evaluate the potential of the technique in acid-catalyzed depolymerization. For this we used ethylene glycol solution with 10% w/v H2SO4 or HCl (T = 120 ° C) and aqueous solutions with 10% w/v H2SO4 or HCl (T=100°C). The depolymerization products were extracted with ethyl acetate and characterized by the techniques of GC / MS and FTIR, showing yields between 3-15% and being formed predominantly of monophenols originating cleavages Cα-Cβ. Therefore the irradiation of microwave technique under acidic conditions has shown promise in the depolymerization of lignin and in the monophenols obtainment through selective breakages.