Olive pomace waste conversion to bio-fuel by application of integrated configuration of pyrolysis/hydrodeoxygenation process

Abstract

Bio-oil obtained from non-catalytic pyrolysis of biomass, consists of a large number of oxygenated compounds. Hence, it is essential for the bio-oil to go through upgrading processes such as hydrodeoxygenation (HDO) to reform these compounds to aliphatic and aromatic hydrocarbons. This study works towards this purpose by initially deriving raw bio-oil from olive pomace waste biomass in a non-catalytic pyrolysis process at temperature of 400–700 ºC. Then for reducing the oxygen content of derived bio-oil, HDO of the raw bio-oil over NiMo/Al₂O₃ catalyst was performed in a batch reactor, in varying operational parameters: temperature of 200–250 °C, reaction time of 1–3 h, hydrogen pressure of 2–6 bar and catalyst: bio-oil ratio of 1:20, 1:10, 1:5. The results revealed that the catalytic HDO is an appropriate procedure, as fatty acids as the main oxygenated components in bio-oil were reduced from 81.8 % to 56.7 %, aldehydes and ketones were entirely removed, and there was a noticeable rise in aliphatic hydrocarbons from 2.8 % to 33.9 % at temperature of 250 ºC, hydrogen pressure of 6 bar and reaction duration of 3 h. In addition, by raising the catalyst to bio-oil ratio to 1:5, the content of fatty acids reached 47.6 %. Furthermore, a comparison was made between the O/C and H/C ratios of the obtained biofuels and the raw bio-oil, which results exhibited that this method worked successfully in substituting oxygen atoms of the raw bio-oil with hydrogen atoms.