The effect of hydrothermal pretreatment on the thermal decomposition of lignocellulosic biomass

ABSTRACT The Effect of Hydrothermal Pretreatment on the Thermal Decomposition of Lignocellulosic Biomass EMİNE GÖZDE VURAL Programme in Chemical Engineering Eskisehir Technical University, Graduate School of Sciences, March 2019 Supervisor: Assoc. Prof. Dr. Esin Apaydın Varol The conversion of biomass into valuable materials plays an important role for the renewable and sustainable environment. Converting lignocellulosic biomass into usable energy and chemicals is one way of promoting society to achieve a sustainable economy. Biomass conversion technologies can be listed as physical, thermochemical and biological, and among them the most widely used method is thermochemical conversion technologies. In this study, pyrolysis process which is one of the thermochemical conversion processes is applied. Biomass pretreatment prior to pyrolysis change the structure and chemical composition of the obtained product. The hydrothermal pretreatment applied at high pressure and temperature allows the structure of the biomass components to be decomposed and is an effective way to convert raw material into valuable products. Therefore, it is one of the suitable methods that can be applied before pyrolysis, specifically when it is aimed to produce valuable chemicals. In this study, hydrothermal pretreatment was applied at 180 oC by adding 0.5%, 1.0% and 1.5% sulfuric acid to rice husk and olive pomace samples. In the second step, the pyrolysis of the raw and pretreated biomass samples was carried out at 500 oC in the fixed bed pyrolysis reactor. Then, the solid and liquid products were characterized by real and bulk density, N2 adsorption-desorption isoterms (BET surface area), Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), Gas chromatography–mass spectrometry (GC-MS). After the hydrothermal pretreatment, the ash content of the olive pomace reduced by 90 %. The highest bio-oil yield was obtained as 32.1 % from olive pomace, whereas rice husk gave the highest solid product (char) yield as 29.6 %. The highest surface area of 284,76 m2/g was obtained from the 1.5 % asit pretreated char sample. In the last part of the study, fixed bed column adsorption experiments were performed using rice husk based solid product. The data were applied to Thomas, Bohart- Adams and Yoon-Nelson models. Keywords: Biomass, Hydrothermal pretreatment, Pyrolysis, Porous carbonaceous materials, Adsorption