Pyrolysis Bio-Oil Upgrading to Renewable Liquid Fuels by Catalytic Hydrocracking: Effect of Operating Conditions on the Process

Abstract

This work analyses the influence of operating conditions during the catalytic hydrocracking of a bio-oil obtained from the fast pyrolysis of pinewood. The original liquid has a 39 wt.% of water and the following elemental composition in dry basis: 54 wt.% C, 3.3 wt.% H, 41.3 wt.% O, 0.8 wt.% N and 0.6 wt.% S.

Experiments were carried out in a batch microbomb reactor employing a co-precipitated Ni–Co/Al–Mg catalyst. They were planned according to a full factorial design of experiments with a statistical analysis of the results in order to analyse the effects of temperature (350–450 °C), hydrogen pressure (70–150 bar), catalyst/bio-oil mass ratio (0–0.25 g catalyst/g organics), reaction time (0–60 min) and all interactions between these operating variables on the process. Statistical analysis of the results indicates that the operating conditions have a statistically significant effect on the results. Specifically, the yields to upgraded bio-oil (liquid), gas and solid vary in ranges of 3–97 %, 0–86 % and 3–41 % respectively. Depending on the operating conditions, the amount of C, H and O (wt.%) in the upgraded bio-oil varies in ranges of 50–82, 3.5–8.3 and 9–44 respectively. This represents an increase of up to 52 and 150 % in the proportion of C and H respectively, as well as a decrease of up to 78 % in the proportion of O. The higher heating value of the treated bio-oil varies from 19 to 37 MJ/kg, which is considerably higher than that of the original bio-oil.