5. Quality of wood vinegars

Compound

4-Propyl

2-methoxyphenol

4-Methyl-2-methoxyphenol

4-Ethyl-2-methoxyphenol

Guaiacol

Eugenol Syringol Acetovanillone

∑ ∑ Total phenol derivatives

1,2 Table 2.

Chemical

compositions

 of eight wood vinegars from five wood species [15].

Dihydroxybenzene

Methoxyphenol

 derivatives

 11.74

 18.66

ND

ND

ND

 ND

 0.18

 0.00

 ND

 6.90

 1.51

 1.46 0.40

0.27

1.20

ND

ND 17.75 22.98

12.34

 19.48

 13.83

7.91

 16.22

 10.53

ND

 ND

 ND

 0.02

 2.01

 0.01

 0.93

 0.01 3.15

 0.02 2.62

 0.02

 3.88 ND 12.60 18.58

30.97

0.18

 0.01 ND

 25.65

27.27

 20.62

 0.01

 3.57 0.18

 0.00 ND

 0.02 0.06

 0.00

 0.01

 0.21

 0.02

 ND

 2.41

 0.02 0.06

 0.00

 0.21

 0.01

 5.23

 0.02 2.16

 0.02

 0.00

 0.42

 0.00

 0.66

 0.01 1.17

 0.01 0.51

 0.01

 0.36

 0.01

 1.33

 0.04 4.28

 0.02

 0.02

 3.10

 0.02

 0.20

 0.01 1.85

 0.01 0.91

 0.01

 1.34

 0.02

 2.81

 0.02 2.33

 0.01

 0.01

 3.09

 0.01

 0.24

 0.00 1.51

 0.02 0.89

 0.01

 1.27

 0.01

 2.59

 0.06 2.23

 0.01

 0.05

 8.92

 0.03

 5.88

 0.03 6.43

 0.03 5.54

 0.02

 5.54

 0.02

 11.56

 0.04 9.56

 0.01

170 Tropical Forests - New Edition

Concentration

L.

leucocephala

 1 L.

leucocephala 2 A. indica 1 A. indica 2 E.

camaldulensis

 1 E.

camaldulensis

 2 D. asper

 H. brasiliensis

 (mg.mL1

)

As mentioned earlier, there are wide variations in the property of wood vinegar due to its mixture of many compounds with different concentrations. However, Japan Pyroligneous Liquor Association, an industrial body for pyroligneous liquor trader sets 7 parameters in order to standardize a good quality of the product. These are included pH value of around 3.0, standard specific gravity around 1.010–1.050, color should be a pale yellow, bright brown or reddish brown, has a marked smoky odor, the dissolved tar content should not more than 3%, ignition residue should not more than 0.2%, and exhibit transparency without suspended solid matter [13]. However, Fagernäs et al. [12] stated that the commercialized wood vinegar in European Unions (EU) has not been accepted because quality is widely varies. Accordingly, attention should be paid to obtain knowledge base on the preparation processes and quality control using a practical and cheap procedure.

The quality assessments of wood vinegars in Thailand were determined according to criteria from the Japan standard with slightly modification. Eight wood vinegars from the carbonization of five wood species—Leucaena leucocephala (Katin), Azadirachta indica (Sadao), Eucalyptus camaldulensis, Hevea brasiliensis (rubber wood) and Dendrocalamus asper (bamboo) grown in Thailand, which produced by heating wood samples up to 400C in a Thai-Iwate kiln showed that all wood vinegar samples appeared to be good quality in terms of odor, color and transparency. An acetic acid concentration from the eight samples whose presence was indicated by pKa at 4.7 (Table 1) was mainly responsible for the pH values as shown in the good correlations of plots between pH and acetic acid concentrations (Correlation coefficient, R = 0.92). The specific gravity showed good correlations with total soluble tar and degree Brix (R = 0.87 for both); in turn the degree Brix showed good correlation with the total soluble tar (R = 0.87). Thus, the degree Brix which was easy to determine could be used as a general indicator of total soluble tar. The amount of total soluble tar signified the presence of phenolic compounds, of which previous studies suggested antifungal activity and usefulness as wood preservatives. In addition, phenolic compounds were also confirmed by the ultraviolet absorption maximum (λmax) at 268–274 nm, [15].

from whole bio-oil and a viscous oligomeric lignin-containing fractions setting at the bottom

Physicochemistry and Utilization of Wood Vinegar from Carbonization of Tropical Biomass Waste

http://dx.doi.org/10.5772/intechopen.77380

173

Filter like filter paper is used to remove the precipitated as well as suspended matters. The filtering of freshly recovered bio-oil cannot fully remove unwanted constituents, causing the appearance rely on filtering method. To obtain transparent wood vinegar, combining the filtering with the standing method is necessary. In the filtering process, the oil and suspended matters in wood vinegar gradually clog the filter paper or filter, lengthening the filtering time. In order to prevent this, frequent changes of the filter paper or filter are necessary. The appearance of suspended matter in transparent wood vinegar after future standing means that

The principle of column chromatography is that substances are separate based on their different adsorption capabilities on stationary phase. Large polar compounds are contained in wood vinegar. In general, highly polar molecules are easily adsorbed in the stationary phase, while weak polar molecules are not. Thus, the process of column chromatography involves adsorption, desorption, re-adsorption, and re-desorption. Silica gel is commonly used as the stationary phase, and an eluent is selected based on the polarity of compounds from wood vinegar. Paraffin eluents, such as hexane and pentene, are used to separate aliphatic compounds. Aromatic compounds are usually eluted with benzene or toluene. Some other polar com-

Distillation is a common separation technology in the chemical industry. This method separates the components successively according to their different volatilities, and it is essential for the separation of liquid mixtures. In general, there are two distillation systems i.e. the normal pressure and reduced pressure distillation. In both systems, compounds are separated by

The carbonizing wood vinegar has water content of as high as 80–90% with a rather small difference in boiling point between the remaining 10% of organic matters. Therefore, the boiling of wood vinegar starts below 100C under atmospheric pressure, and then the distilla-

Distillation method is quite effective to concentrate wood vinegar and also to remove substance with particularly low and high boiling points. However the distillation process cannot entirely remove unwanted polymer. It is more practical to use this method after unwanted polymer in crude vinegar removed by standing method., However, it should be carefully because the heating to boil sample may be induce the oxidation and polymerization in which

pounds are obtained by elution with methanol or other polar solvent [17–19].

tion continues up to 250–280C, whereupon 35–50% of residue is left [20].

by standing at least 3 months [12].

6.3. Column chromatography

6.4. Distillation

mean of the deference boiling points

bring to losing bioactivity of any components.

unstable constituent remains requiring further filtering.

6.2. Filtration
