Abstract
Fast pyrolysis bio-oil oil is a promising alternative to
fossil fuels and is currently entering the heating oil
market. However, there is a lack of available information
about the phase stability of bio-oil. The water-soluble
and water-insoluble compounds in bio-oil can either be in
one homogeneous phase or form two individual phases, to
which we refer to as phase separation. Phase separation
can occur immediately after condensation of the pyrolysis
vapors to bio-oil because of certain pyrolysis conditions
or type of raw material or after years of aging because
of changes in composition caused by repolymerization
reactions. We present how the phase separation of
bio-oils is related to the chemical composition and show
that the probability of phase separation can be predicted
with a numerical stability index based on the chemical
composition. The chemical composition of the bio-oils
studied was characterized using a solvent extraction
scheme that describes the composition of bio-oil as a
blend of three macro fractions: C1-C6 oxygenated
molecules (named co-solvents), water-insoluble molecules,
and water-soluble polar molecules (including water but
excluding the co-solvents), e.g., anhydrosugars. The
results show that the required amount of co-solvent to
dissolve both fractions and keep the bio-oil homogeneous
varies depending upon the chemical composition. The
minimum amount of co-solvent for homogeneous bio-oils was
observed to be from 15 to 30 wt %. The correlation
between the chemical composition and homogeneity of fresh
and aged bio-oils is shown in ternary-phase diagrams.
Addition experiments were made with model compounds to
cover a larger part of the phase diagram.
| Original language | English |
|---|---|
| Pages (from-to) | 4373-4381 |
| Journal | Energy & Fuels |
| Volume | 29 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - 2015 |
| MoE publication type | A1 Journal article-refereed |