Mass balance and characterization of bio-oil from sludge pyrolysis generated in the treatment of effluent from the biodiesel industry

The present work produced bio-oil from the pyrolysis of sludge from the biodiesel processing industry in a fixed bed reactor, aiming at industrial application. The biomass was characterized by immediate and instrumental analysis [thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC/MS)]. The pyrolysis plant consists of a stainless steel fixed bed reactor heated by a reclining split furnace using heated water steam as carrier gas. In the pyrolysis tests, the following parameters were studied: reaction temperature (270 to 830 °C) and heating rate (23 to 37 °C/min). The bio-oil obtained was characterized using classical and instrumental analytical techniques (density, pH, gas chromatography coupled with mass spectrometry and solubility testing). The maximum yield of pyrolytic liquid was around 61.15%, being obtained under the following conditions: (a) temperature of 550 °C and (b) heating rate equal to 30 °C/min. The lowest bio-oil yield observed was 39.89% obtained at 350 °C and reactor heating rate of 25 °C/min. The bio-oil had an acidic pH and density varying between 1 and 1.3 g/mL, being totally soluble in chloroform and dichloromethane solvents. The following chemical functions were identified in the constitution of the bio-oil of this research: (a) phenols, (b) C19 alcohol, (c) carboxylic acids with short and long chains (C6, C8, C16 and C18) and (d) esters (C11, C17, C19 and C23). Sulfur compounds were not found in the samples of the pyrolytic liquid, which points to the possibility of applying this product as a biofuel or even used as an input in the chemical industry.