Pretreatment of bio-oil with ion exchange resin to improve fuel quality and reduce char during hydrodeoxygenation upgrading with Pt/C

Abstract

ABSTRACT To obtain high-quality biofuel, bio-oil obtained from fast pyrolysis of woody biomass was pretreated with ion exchange resin (amberlyst 36) at 50°C, 100°C, and 150°C, and then the recovered liquid product was upgraded using hydrodeoxygenation (HDO) with Pt/C at 300°C. After the two-stage upgrading, 4 types of products (gas, light oil, heavy oil, and char) were obtained. Two-immiscible liquid products were consisted of organic heavy oil, derived from bio-oil, and aqueous light oil, based on the ethanol. The mass balances of the HDO products were influenced by the pretreatment temperature. Ion exchange pretreatment of bio-oil was effective in reducing the char formation during the hydrodeoxygenation (HDO) process. The pretreatment also improved the following heavy oil properties: the water content, heating value, viscosity, acidity, and oxygen level. As a parameter used to indicate the biofuel acidity, the total acid number (TAN) value, was clearly reduced from 114.5 (bio-oil) to 34.1–78.2 (heavy oils). Furthermore, the water and oxygen contents of bio-oil (21.1 and 52.6 wt%, respectively) declined after the pretreatment followed by HDO (ranged 5.1–6.9 and 19.0–25.5 wt%, respectively), thereby improving its higher heating value (HHV) from 17.2 MJ/kg (bio-oil) to 26.2–28.1 MJ/kg (heavy oils). The degree of deoxygenation (DOD) increased as the pretreatment temperature decreased, and the highest energy efficiency (79.8%) was observed after pretreatment at 100°C. In terms of catalyst deactivation during the reaction, both carbon deposition and surface cracking intensified with increasing pretreatment temperatures.