Page 259 - Biosystems Engineering

Biomass Pyr olysis and Bio-Oil Refineries 237

(Chum and Kreibich 1993) involves dissolving bio-oils in ethyl acetate
followed by vacuum filtration to remove the char. Upon standing, the
ethyl acetate/pyrolysis oil separate into two phases: organic-rich, ethyl
acetate soluble (top) and ethyl acetate insoluble (bottom). The ethyl
acetate soluble fraction was extracted with aqueous NaHCO . The
3
phenols and neutrals remained (mostly family B) remained in the
ethyl acetate solution. The resulting oil after the ethyl acetate is
removed is used successfully to replace part of the phenol in the pro-
duction of phenol-formaldehyde resins (Chum and Kreibich 1993).
Excellent reviews of other strategies for bio-oil separation can be found
elsewhere (Fagernäs 1995; Oasmaa et al. 1997; Mohan et al. 2006).
Specialty Chemicals
The production of specialty chemicals using pyrolysis seems more
attractive if especially selected feedstocks are used; for example, cel-
lulose, hemicellulose, or lignin-rich material, as opposed to wood or
waste residues. In that case, the liquid contains a higher concentra-
tion of the desired product, and isolation is easier and cheaper
(Czernik and Bridgwater 2004).
Bridgwater (2005) presented a list of compounds that are economic
to recover and listed the maximum concentration reported in the litera-
ture after carefully controlling the biomass composition and the pyrol-
ysis conditions used. The compounds identified were: levoglucosan
(30 mass%), hydroxyacateldehyde (15 mass%), acetic acid (10 mass%),
formic acid (9 mass%), acetaldehyde (8 mass%), furfuryl alcohol
(5 mass%), catechol (5 mass%), methyl glyoxal (4 mass%), ethanol
(3 mass%), cellobiosan (3 mass%), 1,6 anhydroglucofuranose (3 mass%),
fructuose (2 mass%), glyoxal (3 mass%), formaldehyde (2 mass%),
phenol (2 mass%), propionic acid (2 mass%), acetone (2 mass%), methyl-
cyclopentene-oil-one (2 mass%), methyl formeate (2 mass%), hydro-
quinone (2 mass%), acetol (2 mass%), angelica lactone (2 mass%),
syringaldehyde (1 mass%), methanol (1 mass%), and 1-hydroxy-
2-butanone (1 mass%).
Hydroxyacetaldehyde is the only of these chemicals that is cur-
rently produced from bio-oils. It is the most active meat-browning
agent in liquid smoke. Red Arrow Products (Stradal and Underwood
1995) and Resource Transforms International (RTI) (Majerski et al.
2001) patented methods for isolating this compound based on crys-
tallization. Levoglucosan and levoglucosenone are not typical com-
ponents of bio-oil produced for fuel applications but can be gener-
ated in high yields by similar pyrolysis processes from demineralized
cellulose or biomass (Czernik and Bridgwater 2004). Levoglucose-
none can be produced at high yields (24 mass%) using fluidized-bed
pyrolysis of phosphoric acid–impregnated cellulose (Radlein 1999;
Czernik and Bridgwater 2004).
The recovery of methanol, acetic acid, and acetone from the water-
soluble fractions of bio-oils and the production of turpentine and tars