Pirólise de torta de macaúba: influência dos parâmetros experimentais e caracterização dos produtos

Abstract

In the process of macauba oil extraction, great amounts of waste are generated. In order for the biodiesel production from macauba oil to be an economical and sustainable process, it is fundamental to add value to said waste. Pyrolysis is an alternative that can be used to convert lignocellulosic biomass into biofuels and compounds with high added value. In this sense, the aim of this work was to study the process of macauba cake pyrolysis through biomass characterization, investigation of the kinetic parameters of macauba cake thermal decomposition, analysis of vapors produced from analytical pyrolysis of biomass, analysis of the effects of parameters such as biomass granulometry, reaction temperature and N 2 flow rate in the products yield, and bio-oil and biochar characterization. Global reaction models (Friedman, FWO, KAS and Starink) and the independent parallel reactions model were used to stimulate the kinetic parameters. The vapors produced from analytical pyrolysis were analyzed in the temperatures of 400°C, 500°C and 600°C. The effects of the parameters such as biomass granulometry, reaction temperature and N 2 flow rate in the yield of bio-oil, biochar and gases (obtained by difference) were assessed using complete factorial planning. The minimum, medium and maximum reaction temperature, biomass granulometry and N2 flow rate were 400°C, 500°C and 600°C, 0,106 – 0,250 mm, 0,250 – 0,355 mm and 0,355 – 0,425 mm, and 500 mL min -1 , 800 mL min -1 and 1100 mL min -1 , respectively. The bio-oil was characterized by Gas Chromatography Mass Spectrometry (GC/MS) and the biochar by Fourier transform infrared spectroscopy (FTIR), scanning electronic microscopy (SEM) and proximate analysis. The activation energy obtained for the global reaction models presented values between 161,4 kJ mol -1 and 223,1 kJ mol -1 . The independent parallel reactions model indicated that the macauba cake decomposition consists of three different reactions corresponding to the decomposition of cellulose, hemicelluloses and lignin. The activation energy and pre-exponential factor values for the cellulose decomposition were 120,600 kJ mol -1 and 7,960x10 7 s -1 , respectively. For the hemicelluloses, the activation value was 72,863 kJ mol -1 and the pre-exponential factor ranged from 8,955x10 3 s -1 to 16,915x10 3 s -1 . The activation energy for the lignin ranged from 28,140 kJ mol -1 to 44,220 kJ mol -1 and the preexponential factor from 0,458 mol -1 L s -1 to 0,896 mol -1 L s -1 . The compounds that presented greatest peak areas in the analytical pyrolysis chromatograms were acetic acid, 2-propanone-1-hydroxy and fatty acids. The best condition for the macauba cake pyrolysis was determined in order to obtain the greatest bio-oil yield. Such condition was obtained in the assay with 400°C temperature, 0,106 – 0,250 mm granulometry and 500 mL min -1 N2 flow rate. The compounds identified in the bio-oil were, mainly, ketones, furans and phenols. The macauba cake proved to be adequate for the pyrolysis process and the products obtained present important industrial applications.