Page 249 - Biosystems Engineering

Biomass Pyr olysis and Bio-Oil Refineries 227

these two oils can be easily appreciated. A detailed description of the
methods used to fit the different chemical families can be found else-
where (Garcia-Pérez et al. 2008).
Family A is formed by very volatile organic compounds (mainly
hydroxylacetaldehyde, formic acid, and methanol), which result from
biomass fragmentation reactions.
Family B consists of water and other volatile compounds with
similar boiling points (acetic acid, acetol, and propionic acid). The
water usually represents between 5 to 30 mass% of the whole bio-oil
and is the single most abundant specie found in these liquids.
Family C consists of compounds with moderate volatility with
boiling points between 100 and 250°C. This family can represent up
to 45 mass% of crude bio-oils and is dominated by furans and mono-
phenols resulting from depolymerization reactions. These compounds
have between 5 and 13 atoms of carbon and are commonly divided into
two subfractions. The hydroxyl, hydroxymethyl, and oxo-substituted
furans, furanones, pyranones, and cyclopentents obtained from the
thermal degradation of cellulose and hemicellulose are commonly
called neutral fractions and can account for between 10 and 30 mass%
of bio-oil. Some of the compounds found in this subfraction are cyclo-
pentanone, 2-furancarboxaldehyde, ethanone-1-(2-furanyl), methyl-
tetrahydrofuran, 2-furanone, furfuryl alcohol, and methyltetrahydro-
furan. The second subfraction is composed of monophenols having
between 6 and 12 atoms of carbon. This fraction is weakly acidic and
includes compounds such as phenol, catechol, 2,3-dimethylphenol,
hydroquinone, 1,2-benzenediol, syringaldehyde, and 3-ethyl-phenol
(Garcia-Pérez et al. 2006a, 2007a, 2008). These compounds can account
for up to 15 mass% of the whole oil.
Species with moderate volatility having a boiling point between
200 and 300°C very similar to the kerosene constitute family D. This
fraction usually accounts for between 5 and 35 mass% of crude bio-
oils. Five major groups of compounds can be found in this family:
(1) polyaromatics, (2) aliphatic hydrocarbons, (3) fatty acids and its methyl
esters, (4) sterols, and (5) sugars. The polyaromatics found in bio-oils
have between 10 and 28 atoms of carbon. Some of the most common
polyaromatics found in bio-oils are naphthalene, 1,2-dihydroxy3-
methylnaphtalene, phenanthrene, 3,6-dimethyl-phenanthrene, and
1-methylanthracene. The aliphatic hydrocarbons found in bio-oils
have between 13 and 32 atoms of carbon. Examples of these com-
pounds are 1-octadecene, nonadecane, eicosane, heneicosane, and
1-docosene. Fatty acids and their methyl esters generally have
between 14 and 27 atoms of carbon. Examples of compounds forming
this group are tetradecanoic acid, hexadecanoic acid, hexadecanoic
and acid methyl ester. Sterols are also obtained from biomass extrac-
tives; some examples are β-sitosterol, 3-ol, and stigmata-4-en-3-one.
Sugars are another important group in family D and usually account
for around 10 mass% of the whole oil. The main sugar found in bio-oils