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Hydrothermal upgrading of wood biomass: Influence of the addition of K2CO3 and cellulose/lignin ratio Thallada Bhaskar a,*, Akira Sera b, Akinori Muto b, Yusaku Sakata b,* a
Catalytic Conversion Process Division (CCPD), Indian Institute of Petroleum (IIP), Dehradun 248 005, India b Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan Received 24 January 2007; received in revised form 18 October 2007; accepted 18 October 2007 Available online 20 November 2007
Abstract The hydrothermal treatment of two different wood biomass samples such as cherry (hard wood) and cypress (soft wood), whose composition is different i.e. lignin, cellulose and hemicellulose were performed at 280 °C for 15 min with aq. K2CO3 with different concentrations (0–1 M). The soft wood biomass contains higher lignin content than hard wood biomass. The cellulose rich cherry wood biomass produced higher proportion of acetic acid than cypress. The lignin rich cypress produced the hydrocarbons with major portion of phenolic hydrocarbons and derivatives than cherry. The total oil yields from both cherry and cypress wood biomass produced 50 wt% of liquid hydrocarbons at 280 °C for 15 min with 0.5 M K2CO3 solution. The volatility distribution of liquid hydrocarbons showed the characteristic features of soft and hard wood biomasses. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Biomass; Hydrothermal process; Lignin; Cellulose; Phenolic hydrocarbons
1. Introduction From the viewpoint of environmentally benign and sustainable chemistry, biomass resources have been attracting much attention as alternatives for traditional petrochemical raw materials [1,2]. Biomass is a promising source for the production of an array of energy-related products including, liquid, solid, and gaseous fuels, heat, chemicals, electricity and other materials. While the 20th century saw the emergence and establishment of an organic chemical manufacturing industry based on petroleum refining, the 21st century will see the development of a new organics industry based on biomass refining [3–5]. Biomass to biorefinery [6] and biofuels [7], a chemical perspective has been reviewed by highlighting the various approaches and technologies for the utilization of biomass resources [6,7]. Bio* Corresponding authors. Tel.: +91 135 2660146; fax: +91 135 2660202/ 203 (T. Bhaskar); tel./fax: +81 86 251 8966 (Y. Sakata). E-mail addresses: [email protected], [email protected] (T. Bhaskar), [email protected] (Y. Sakata).
0016-2361/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2007.10.018
mass conversion process such as liquefaction [8–10], gasification [11–13], and combustion [14,15] have been studied widely. Conversion of biomass to liquid fuel or chemical feedstock has been carried out by pyrolysis [16,17]. In a recent study, Yaman reviewed the pyrolysis of biomass to produce fuels and chemical feedstock [18]. It was concluded that the liquid products from pyrolysis of biomass can be improved using some methods such as catalytic upgrading or steam reforming [18]. Liquid fuels from biomass via hydrothermal [19–21] and fast pyrolysis [22] process was also extensively studied for the production of heavy oils. However, the production of chemicals from biomass is an attractive utilization method due to their much higher benefit compared to fuels and energy production, if they are produced for selective application. A range of chemicals can be produced from biomass such as levoglucosan to commodities such as resins and fertilizers [23]. Selective production of oxygenated hydrocarbons such as phenols and/or sugars from biomass is indeed of importance for use as a chemical for the production of phenolic based
T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
resins and related applications. Wu et al. [24] have developed for production aldehydes (lignin and syringaldehyde) from steam-explosion hardwood lignin. Alkaline oxidation of steam-explosion lignin yielded 14.6% the combined vanillin and syringaldehyde yield. In another study, phenolic compounds from wood tar were recovered by means of methanol-mediated extraction [25]. Besides phenolic compounds, other hydrocarbons such as formic acid, formaldehyde, acetic acid, levoglucosan, cellobiosan etc., can be good candidates as chemicals. From our earlier works, we reported the low temperature hydrothermal treatment of biomass and optimization of reaction parameters [26], effect of alkaline solutions (Na, K, Rb, Cs) hydroxides and carbonates and optimized the for high oil yields and less solid residues [27–29]. Onsagar et al., [30] reported that the hydrogen production from water and CO via alkali metal (Na, K, Cs, Rb) formate salts in the presence of alcohols. Yokoyama et al. [31] have studied the effect of variety of wood on yields and properties of heavy oils. However, they have not reported the detailed investigation on the composition of hydrocarbons with respect to the soft and hard wood biomasses (13 types) as the composition of soft and hard wood biomasses differ in lignin, cellulose and hemicellulose. In addition, the studies on the cypress (soft) and cherry (hard) wood biomass by hydrothermal upgrading were not reported. In the present investigation, we report the hydrothermal upgrading of wood biomass at 280 °C for 15 min to show the effect of cypress (soft) and cherry (hard) wood biomasses on the products distribution, composition of liquid hydrocarbons, effect of K2CO3 concentration on the products distribution and the volatility distribution of hydrocarbons to understand the marked difference between the hydrocarbons from soft and hard wood biomasses. The liquid products were separated using different solvents and analyzed them qualitatively and semi-quantitatively. The investigation focused on the extensive analysis of the liquid hydrocarbons to observe the formation of key compounds from different wood biomasses. 2. Experimental 2.1. Materials Wood biomass i.e. cherry and cypress was obtained from Yonebayashi Milling Co., Ishikawa Prefecture, Japan. The analysis of biomass composition such as lignin, cellulose, hemicellulose of soft and hard wood biomass was performed with the method described by Li et al. [32]. The composition of cherry was 12.5 wt% lignin, hemicellulose 29.6 wt%, cellulose 56.0 wt%, ash 0.8 wt%, extractives 1.1 wt% and cypress was 34.4 wt% lignin, hemicellulose 18.4 wt%, cellulose 46.1 wt%, ash 0.3 wt%, extractives 0.7 wt%. The elemental analysis of Cherry samples has C:43.4, H:5.5, Oxygen: 51.2, Moisture: 9.0 and cypress sample analysis was C:44.5, H:5.7, Oxygen: 49.8, Moisture: 10.6. The elemental analysis was performed by Perkin
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Elmer C, H, N analyzer. The oxygen content was estimated from the difference of carbon, hydrogen and nitrogen. 2.2. Experimental Hydrothermal liquefaction experiments were conducted in a 200 ml TaS-02-HC type autoclave at 280 °C for 15 min. In a typical hydrothermal liquefaction experiment, the reactor was loaded with 5 g (dry basis) of biomass and 30 ml of aq. K2CO3 solution. Then the reactor was purged five times with nitrogen to remove the inside air. Reactants were agitated vertically at 60 ffi cycles/min using stirrer as shown in [28–30]. The temperature was then raised up to 280 °C at heating rate of 3 °C/min and kept for 15 min at 280 °C. After the reaction time, the reactor was cooled down to the room temperature by fan. The gaseous products were vented. The solid and liquid products were rinsed from the autoclave with ionexchanged water, then acidified to pH 1–2 with HCl (1.7 M) covered and kept in the refrigerator overnight (12 h). Solid and liquid products were separated by filtration under vacuum for 15 min. During filtration, 100 ml of ion-exchanged water were used for washing solid products. The liquid portion was extracted with equal quantity of diethyl ether (600 ml). The etheral solution thus obtained was dried over anhydrous sodium sulfate, filtered and evaporated in a rotary evaporator at room temperature. Upon removal of diethyl ether, this fraction was weighed and designated as oil 1. The water phase was further extracted with equal quantity of ethyl acetate (200 ml). The ethyl acetate solution thus obtained was dried over anhydrous sodium sulfate. Upon removal of ethyl acetate under reduced pressure, this fraction was weighed and designated as oil 2. After extraction, the remaining water phase contained the water-soluble hydrocarbons. Solid products were extracted with acetone (150 ml) in a Soxhlet extraction apparatus until the solvent in the thimble became colorless (about 20 h). After removal of the acetone under reduced pressure in a rotary evaporator, this fraction was weighed and designated as oil 3. Acetone insoluble fraction was dried at 105 °C then weighed, called as solid residue. All yields were calculated on a dry basis material and details for calculations of yields and separation of hydrothermal products can be found elsewhere [29,30]. The conversion is defined as the amount of solid biomass converted into other forms i.e., liquid, gas. Oils including oil 1, oil 2 and oil 3 obtained from low temperature hydrothermal liquefaction of wood biomass were analyzed by gas chromatograph equipped with a mass selective detector (GC–MS; HP 5973; column, HP-1). 3. Results and discussion The elemental composition of cherry and cypress wood biomasses shows that there are no significant differences in the elemental composition of two different wood biomasses. The elemental analyses of around 10 different
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T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
wood biomass samples in the literature [31] are also showed the similar results. The composition of cherry and soft wood biomasses for lignin, hemicellulose, ash, extractives and cellulose were analyzed and it is clear from the data that the cypress (soft wood) is rich in lignin and cherry (hard wood) is rich in hemicellulose and cellulose. The lignin is ca. 3 times higher in the cypress (soft wood) biomass. The differences in the composition showed the remarkable differences in the composition of liquid hydrocarbons obtained with different solvents. The detailed information will be discussed in the following sections.
3.1. Product distribution Table 1(a) shows the product distributions obtained from hydrothermal treatment of cherry at 280 °C for 15 min with different concentration of aq. K2CO3 solution. The conversion of cherry in the absence of alkali solution showed around 70 wt% and with the increase of alkali solution concentration the conversion increased to 80 wt% at 0.25 M and further up to 96 wt% at 0.5 M. The conversion at 1 M concentration was ca. 99 wt% leaving ca. 1 wt% residue, which is equivalent to the ash content in cypress. It is interesting to see that the differences in the conversion of cypress at 0.5 and 1 M was around 3 wt%, however the total oil yield at 0.5 was 35 wt% and at 1 M was 48 wt%. It shows that the alkali solution increased the conversion and also the increase in the total oil yields with cypress. There are no significant differences in the yields of gaseous products with all experimental runs (run 1 to run 4 in Table 1 (a)) and the analysis gaseous products showed the major portion was carbon dioxide and traces of carbon monoxide, methane, ethane, and ethylene were found. The water soluble hydrocarbons (WSH) were around 30 wt% with and without alkali solutions, except with the 0.5 M concentration showing 43 wt%. Table 1(b) shows the product distribution from hydrothermal treatment of cypress at 280 °C for 15 min at different alkali concentrations. The conversion of cypress in the absence of alkali solution was 56 wt%, which is less than for cherry at the identical conditions. It shows that differences in conversions for
cherry and cypress comes from the differences in the composition of wood biomass and also macromolecular structure of wood biomass. In the absence of alkali solution, the total oil yield for cherry was 15.7 wt% and for cypress was 7.7 wt%. The presence of high hemicellulose and cellulose improved the conversions and total oil yields for cherry than cypress. The cypress conversions were found to increase with the increase of alkali concentration up to 0.5 M and there is no further increase in conversion with the concentration up to 1 M. At this concentration range, the cypress and cherry showed no significant conversion differences showing that the 0.5 M concentration is sufficient for high conversions. However, the total oil yields were increased up to 15 wt% in cherry from 0.5 M to 1 M but the effect could not be observed in cypress. Oil 1 and oil 2 yields were found to increase with the increase of alkali concentration and the oil 3 yields were highest (28.8 wt%) at 0.5 M concentrations for cypress than 1 M (23.3 wt%). It is understood that the decomposition of high cellulose wood biomasses favors the formation of watersoluble hydrocarbons rather than oily (water insoluble) compounds. It can be concluded that the decomposition of lignin or lignin rich wood biomasses in water (280 °C 15 min) is comparatively less than cellulose or cellulose rich samples [33]. Kadangode [34] investigated the lignin conversion in methanol at the temperature range 230–310 °C. It was reported that water/ether soluble hydrocarbons were also produced by decomposition of lignin. The yields of the products from hydrothermal treatment of biomass depends on the experimental conditions which includes, the type of biomass, reaction temperature, reaction time, solvent/biomass ratio, type of reactor and so on. We would like to stress that the pyrolysis process is different and should not be compared with the hydrothermal process as the presence of water or solvent strongly effects the product distribution and composition of each product.
3.2. Composition of oil products The identification of hydrocarbons from cherry oil 1 products was tabulated in Table 2. The formation acetic
Table 1 Products distribution from hydrothermal treatment of wood biomass at 280 °C for 15 min Run no.
(a) Cherry 1 2 3 4
Aq. K2CO3, M
Conv., wt%
Oil, wt% Oil 1
Oil 2
Oil 3
Total oil
Gas, wt%
Residue, wt%
Water solubles, wt%
0 0.25 0.5 1
69.0 80.0 96.0 99.0
7.6 10.4 15.6 17.1
1.0 3.7 2.9 5.6
7.2 10.4 16.4 25.5
15.7 24.5 34.9 43.2
19.9 23.8 17.7 19.7
30.7 20.4 4.3 1.3
33.6 31.3 43.1 30.8
(b) Cypress 1 0 2 0.25 3 0.5 4 1
56.3 80.3 95.7 94.9
20 16.5 17.4 20.0
1.1 3.4 5.7 5.2
4.5 20.2 28.8 23.3
7.7 42.1 52.0 49.5
9.9 12.5 9.8 10.0
43.7 19.7 4.3 5.1
38.8 23.7 34.0 35.4
T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
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Table 2 Identification of compounds by GC–MS in oil 1 from cherry hydrothermal treatment No.
RT, min
Name of compound
1 2 3 4 5 6 7 8 9 10
1.0 1.6 2.0 7.0 9.6 12.4 12.6 14.6 17.1 24.5
Acetic acid Propanoic acid 2-Furancarboxaldehyde Phenol 2-Methoxyphenol 2-Methoxy, 4-methylphenol Benzoic acid 1,2-Benzenediol-3-methoxy 2,6-Dimethoxyphenol Butylated hydroxytoluene
acid was found to increase with the addition of alkali up to 0.5 M (17. 43%) and further increase in alkali decreased the formation of acetic acid (7.45%). The results of chromatographic area (% of total area) belong to the identified compounds. The difference to 100% area represents the area of unidentified compounds. The amount of acetic acid was the highest in cellulose-derived oil 1 (ether extract) [33] and the present results are in good agreement with the hydrothermal upgrading of pure cellulose and lignin. The reason is that the cellulose produced mainly 2-furancarboxaldehyde and 5-methyl-2-furancarboxaldehyde. Cherry oil 1 products showed the around 23% of 2-furancarboxaldehyde and the compound could not found in cypress oil 1 (Table 2). The further decomposition of 2-furancarboxaldehyde and 5-methyl-2-furancarboxaldehyde products led to form acetic acid. The improvement in the formation of acetic acid and disappearance of 2-furancarboxaldehyde can be clearly seen in Table 2 for cherry hydrothermal treatment.
Area (%) 0
0.25 M
0.5 M
1.0 M
7.7 4.9 22.5 3.6 12.9 1.2 – 5.0 25.0 3.5
17.8 7.5 – 2.4 17.7 0.5 1.8 – 24.0 3.2
17.4 3.4 0.5 5.0 22.0 3.6 1.3 1.7 8.7 3.4
7.4 1.7 – 6.6 28.7 2.1 1.9 – 4.7 3.6
It can be clearly seen that the transformation of 2,6dimethoxyphenol to 2-methoxyphenol with the increase of alkali concentration (Table 2). Lignin-derived oil 1 predominantly contains 2-methoxyphenol with formation of other hydrocarbons such as 1,2-benzenediol, phenol, 3methyl-1,2-benzenediol. It is considered that initially 2methoxyphenol (as explained above) was formed and further decomposition produced 1,2-benzenediol and phenol derivatives [35]. The identification compounds in oil 2 from cherry were given in Table 3. The major compounds in oil 2 from the hydrothermal treatment in the absence of alkali solutions were 3-methylphenol had 27% and next 2,6-dimethoxy phenol. More than 30% of 1,2-butanediol was appeared at 0.5 and 1.0 M concentrations at oil 2 from cherry and the same compound couldn’t be found for 0.25 M and in the absence of alkali solution. The compounds in the oil 3 from cherry (Table 4) hydrothermal process showed that in the absence of alkali solutions
Table 3 Identification of compounds by GC–MS in oil 2 from cherry hydrothermal treatment No.
1 2 3 4 5 6 7 8 9
RT, min
1.0 7.9 10.1 10.5 10.9 13.0 17.1 19.8 20.9
Name of compound
Acetic acid 3-Methyl-2-cyclopentene-2-ol-one 3-Methylphenol 3-Butanoic acid 1,2-Butanediol 1-Butanol, 4-methoxy 2-6-Dimethoxyphenol 2-Ethoxy, 1-propanol 2,4-Pentanediol
Area (%) 0
0.25 M
0.5 M
1.0 M
10.5 27.5 – – – 17.2 – –
79.0 – – 2.9 – – 3.9 – –
11.3 – – – 37.6 3.3 4.5 5.3 –
16.0 – – – 32.7 2.6 – 11.0 16.0
Table 4 Identification of compounds by GC–MS in oil 3 from cherry hydrothermal treatment No.
RT, min
Name of compound
Area (%) 0
0.25 M
0.5 M
1.0 M
1 2 3 4 5
2.0 9.6 13.1 15.2 17.1
4-Hydroxy-4-methyl-2-pentanone 2-Methoxyphenol 2-Methoxy-4-ethyl-phenol 4-Ethyl, 2-methoxyphenol 2,6-Dimethoxyphenol
19.7 11.4 1.6 5.1 21.8
18.3 8.9 8.0 – 20.0
22.0 11.7 – 4.9 –
36.9 – – – –
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2-methoxyphenol and 2, 6-dimethoxyphenol and 4Hydroxy-4-methyl-2-pentanone was observed and with the increase of alkali solution concentration, the compounds such as phenolic derivatives could not been found. With the use of alkali solutions, these phenolic derivatives were concentrated in oil 1 and oil 2. The 4-hydroxy-4methyl-2-pentanone was found to increase with the increase of alkali concentration and it may be from the cleavage of benzene derivatives. The oil 3 is heavy molecular hydrocarbons portion and major portion of oil 3 hydrocarbons from 0.5 and 1 M cherry hydrothermal treatment could not be analyzed due to the limitation of GC/MS. The mechanism for formation of 2-furancarboxaldehyde and 5-methyl-2furancarboxaldehyde were reported by Jakab et al. [36]. The identification of hydrocarbons in oil 1, oil 2 and oil 3 from cypress hydrothermal treatment and with different alkali concentration were analysed and given in Table 5–7. The major hydrocarbon which was found to increase with
the increase of alkali concentration was found to be 2methoxyphenol and it is around 50 wt% at 0.25 and 0.5 M concentrations. In addition the formation of 1,2-benzenediol and its derivatives were found to increase with the increase of alkali concentration. Klein et al. [35] showed that the formation of 1,2-benzenediol from 2-methoxyphenol. The small decrease in the formation of 2-methoxyphenol from cypress oil 1 at 1 M concentration was substantiated with the formation of 1,2-benzenediol and its derivatives. There was no phenolic and benzenediol derivatives in the cypress oil 2 in all runs (Table 6). But, the 2-methoxyphenol and derivatives were found in oil 3 from cypress and 0.5 M concentration had more than 30% of 2-methoxyphenol. It is clear from the oil 1 and oil 3 that major portion of hydrocarbons from thermal and alkali hydrothermal treatment were found to be 2-methoxyphenol and benzenediol derivatives, the presence of phenolic derivatives were higher due to the presence higher lignin content in cypress than cherry.
Table 5 Identification of compounds by GC–MS in oil 1 from cypress hydrothermal treatment No.
1 2 3 4 5 6 7 8 9 10 11
RT, min
1.0 1.6 7.0 9.6 11.7 13.0 14.5 15.4 16.9 21.4 24.5
Name of compound
Area (%)
Acetic acid Propanoic acid Phenol 2-Methoxyphenol 1,2-Dimetioxybenzene 2-Methoxy, 4-methylphenol5l 1,2-Benzenediol 4-Ethyl, 2-methoxyphenol 1,2-Bezenediol, 3-methyl Butylated hydroxytoluene 4-Hydroxy-3-methoxy benezene acetic acid
0
0.25 M
0.5
1.0 M
– – 5.2 15.2 1.0 5.0 2.2 1.3 1.3 21.5 9.1
7.7 2.2 2.4 53.3 0.8 4.7 0.5 3.6 1.0 3.7 –
9.9 – – 48.9 0.7 3.3 – 1.6 0.8 2.8 1.2
2.7 – 1.2 34.9 2.1 5.0 18.3 3.9 12.6 2.3 –
Table 6 Identification of compounds by GC–MS in oil 2 from cypress hydrothermal treatment No.
1 2 4 5 6 7
RT, min
1.0 1.6 2.9 9.4 10.8 11.9
Names of compound
Acetic acid Propanoic acid 2-Methyl-2-cyclopentene-1-one Isopropyl alcohol 2-Butanol Cyclopropanecarboxylic acid
Area (%) 0
0.25 M
0.5 M
1.0M
20.2 3.4 1.0 – 5.4 4.0
54.0 – 2.3 1.3 – –
9.2 1.2 2.6 10.5 3.8 4.4
7.0 – – 7.4 9.7 –
0
0.25 M
0.5 M
1.0 M
7.6 24.0 12.0 – 11.5
44.9 – – – –
15.4 31.5 – 6.7 6.7
46.8 – – – –
Table 7 Identification of compounds by GC–MS in oil 3 from cypress hydrothermal treatment No.
1 2 3 4 5
RT, min
2.0 9.6 12.9 14.0 15.9
Name of compound
4-Hydroxy-4-methyl-2-pentone 2-Methoxyphenol 2-Methoxy, 4-methylphenol 1,2-Dimethoxybenzene 1,4-Dimethoxy-2-methylbenzene
Area (%)
T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
The GC–MS analysis data used for semi-quantitative analysis of hydrocarbons and presented the boiling point distribution of cherry and cypress biomass derived oils (ether extract), in the form of C–NP gram (Figs. 1 and 2) which was proposed to present the plastic derived oil [37]. Fig. 1 shows the composition of the oils (ether extract) obtained from cherry with different concentrations of alkali solution (aq. K2CO3) and Fig. 2 for cypress wood biomass. The carbon numbers in the abscissa represent the equivalent boiling point (B.P.) range of normal paraffin hydrocarbons. The details about C-NP gram can be found in elsewhere [37]. The hydrocarbons were distributed in the boiling point region n-C6 to n-C18 for all oils. The hydro-
2241
carbons in the n-C7 and n-C8 hydrocarbons were decreased with the increase of alkali concentration and hydrocarbons at n-C11 were found to increase with the increase of alkali solution and it is due to the phenolic derivatives (BP. range 200 °C). The hydrocarbons at n-C13 were found to decrease with the alkali and they are due to the decomposition of 2,6-dimethoxy phenol and its derivatives (BP range 235 °C). It can be seen from Fig. 1 (cherry) that there are three major peaks showing that the hydrocarbons were in three boiling point ranges in oil 1. Fig. 2 shows the boiling point distribution of hydrocarbons from oil 1 from cypress. It is clear from Fig. 2 that the more than 60% of hydrocarbons were concentrated at n-C11 which is due to
40 K 2 CO3 aq.
oil 1 compounds area %
35
0M
30 25
0.25 M
20
0.5 M
15
1.0 M
10 5 0 6
5
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Carbon num ber Fig. 1. C-NP gram of oil 1 obtained from cherry hydrothermal treatment at 280 °C for 15 min.
70 K 2 CO3 aq., 60
oil 1 compounds area %
0M 0.25 M
50
0.5 M 40 1.0 M 30
20
10
0 5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Carbon number Fig. 2. C-NP gram of oil 1 obtained from cypress hydrothermal treatment at 280 °C for 15 min.
20
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T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
2-methoxyphenol and derivatives. This is the characteristic feature of the cypress hydrocarbons and presence of lignin higher portion clearly showed the formation of high quantity of phenolic derivatives than cypress, which has less lignin content. 4. Conclusions The hydrothermal upgrading of cherry and cypress wood biomasses whose lignin, hemicellulose and cellulose composition is different. The formation of acetic acid was pronounced in the hemicellulose and cellulose rich cherry than cypress. The formations of phenolic derivatives were higher in lignin rich cypress than cherry biomass. However, the total oil yields from both wood biomasses at 0.5 M concentrations were around 50 wt% and higher conversions (>95 wt%). Acknowledgements We thank Yonebayashi Milling Co., Ishikawa Prefecture, Japan for providing the biomass samples. Partial financial support from the Centre of Excellence Program for the 21st Century – Strategic Solid Waste Management for Sustainable Society at Okayama University to carryout the research work is highly appreciated. References [1] Anastas PT, Warner JC. Green chemistry theory and practice. Oxford: Oxford University Press; 1998. [2] Okkerse C, van Bekkum H. Green Chem 1999;1:107–14. [3] Bozell JJ, Patel MK. Feedstocks for the future. New York: ACS; 2006. [4] Stevens CV, Verhe RV. Renewable resources. Chichester: Wiley; 2004. [5] Ragauskas AJ, Williams CK, Davison BH, Britovsek G, Cairney J, Eckert AC, et al. Science 2006;311:484–9. [6] Clark JH, Budarin V, Deswarte FEI, Hardy JJE, Kerton FM, Hunt AJ, et al. Green Chem 2006;8:853–60. [7] Petrus L, Noordermeer MA. Green Chem 2006;8:861–7. [8] Inoue S, Okigawa K, Minowa T, Ogi T. Biomass Bioenergy 1999;16:377–83. [9] Aguado R, Olazar M, Jose MJS, Aguirre G, Bilbao J. Ind Eng Chem Res 2000;39:1925–33.
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Fuel 87 (2008) 2236–2242 www.fuelfirst.com
Hydrothermal upgrading of wood biomass: Influence of the addition of K2CO3 and cellulose/lignin ratio Thallada Bhaskar a,*, Akira Sera b, Akinori Muto b, Yusaku Sakata b,* a
Catalytic Conversion Process Division (CCPD), Indian Institute of Petroleum (IIP), Dehradun 248 005, India b Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan Received 24 January 2007; received in revised form 18 October 2007; accepted 18 October 2007 Available online 20 November 2007
Abstract The hydrothermal treatment of two different wood biomass samples such as cherry (hard wood) and cypress (soft wood), whose composition is different i.e. lignin, cellulose and hemicellulose were performed at 280 °C for 15 min with aq. K2CO3 with different concentrations (0–1 M). The soft wood biomass contains higher lignin content than hard wood biomass. The cellulose rich cherry wood biomass produced higher proportion of acetic acid than cypress. The lignin rich cypress produced the hydrocarbons with major portion of phenolic hydrocarbons and derivatives than cherry. The total oil yields from both cherry and cypress wood biomass produced 50 wt% of liquid hydrocarbons at 280 °C for 15 min with 0.5 M K2CO3 solution. The volatility distribution of liquid hydrocarbons showed the characteristic features of soft and hard wood biomasses. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Biomass; Hydrothermal process; Lignin; Cellulose; Phenolic hydrocarbons
1. Introduction From the viewpoint of environmentally benign and sustainable chemistry, biomass resources have been attracting much attention as alternatives for traditional petrochemical raw materials [1,2]. Biomass is a promising source for the production of an array of energy-related products including, liquid, solid, and gaseous fuels, heat, chemicals, electricity and other materials. While the 20th century saw the emergence and establishment of an organic chemical manufacturing industry based on petroleum refining, the 21st century will see the development of a new organics industry based on biomass refining [3–5]. Biomass to biorefinery [6] and biofuels [7], a chemical perspective has been reviewed by highlighting the various approaches and technologies for the utilization of biomass resources [6,7]. Bio* Corresponding authors. Tel.: +91 135 2660146; fax: +91 135 2660202/ 203 (T. Bhaskar); tel./fax: +81 86 251 8966 (Y. Sakata). E-mail addresses: [email protected], [email protected] (T. Bhaskar), [email protected] (Y. Sakata).
0016-2361/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2007.10.018
mass conversion process such as liquefaction [8–10], gasification [11–13], and combustion [14,15] have been studied widely. Conversion of biomass to liquid fuel or chemical feedstock has been carried out by pyrolysis [16,17]. In a recent study, Yaman reviewed the pyrolysis of biomass to produce fuels and chemical feedstock [18]. It was concluded that the liquid products from pyrolysis of biomass can be improved using some methods such as catalytic upgrading or steam reforming [18]. Liquid fuels from biomass via hydrothermal [19–21] and fast pyrolysis [22] process was also extensively studied for the production of heavy oils. However, the production of chemicals from biomass is an attractive utilization method due to their much higher benefit compared to fuels and energy production, if they are produced for selective application. A range of chemicals can be produced from biomass such as levoglucosan to commodities such as resins and fertilizers [23]. Selective production of oxygenated hydrocarbons such as phenols and/or sugars from biomass is indeed of importance for use as a chemical for the production of phenolic based
T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
resins and related applications. Wu et al. [24] have developed for production aldehydes (lignin and syringaldehyde) from steam-explosion hardwood lignin. Alkaline oxidation of steam-explosion lignin yielded 14.6% the combined vanillin and syringaldehyde yield. In another study, phenolic compounds from wood tar were recovered by means of methanol-mediated extraction [25]. Besides phenolic compounds, other hydrocarbons such as formic acid, formaldehyde, acetic acid, levoglucosan, cellobiosan etc., can be good candidates as chemicals. From our earlier works, we reported the low temperature hydrothermal treatment of biomass and optimization of reaction parameters [26], effect of alkaline solutions (Na, K, Rb, Cs) hydroxides and carbonates and optimized the for high oil yields and less solid residues [27–29]. Onsagar et al., [30] reported that the hydrogen production from water and CO via alkali metal (Na, K, Cs, Rb) formate salts in the presence of alcohols. Yokoyama et al. [31] have studied the effect of variety of wood on yields and properties of heavy oils. However, they have not reported the detailed investigation on the composition of hydrocarbons with respect to the soft and hard wood biomasses (13 types) as the composition of soft and hard wood biomasses differ in lignin, cellulose and hemicellulose. In addition, the studies on the cypress (soft) and cherry (hard) wood biomass by hydrothermal upgrading were not reported. In the present investigation, we report the hydrothermal upgrading of wood biomass at 280 °C for 15 min to show the effect of cypress (soft) and cherry (hard) wood biomasses on the products distribution, composition of liquid hydrocarbons, effect of K2CO3 concentration on the products distribution and the volatility distribution of hydrocarbons to understand the marked difference between the hydrocarbons from soft and hard wood biomasses. The liquid products were separated using different solvents and analyzed them qualitatively and semi-quantitatively. The investigation focused on the extensive analysis of the liquid hydrocarbons to observe the formation of key compounds from different wood biomasses. 2. Experimental 2.1. Materials Wood biomass i.e. cherry and cypress was obtained from Yonebayashi Milling Co., Ishikawa Prefecture, Japan. The analysis of biomass composition such as lignin, cellulose, hemicellulose of soft and hard wood biomass was performed with the method described by Li et al. [32]. The composition of cherry was 12.5 wt% lignin, hemicellulose 29.6 wt%, cellulose 56.0 wt%, ash 0.8 wt%, extractives 1.1 wt% and cypress was 34.4 wt% lignin, hemicellulose 18.4 wt%, cellulose 46.1 wt%, ash 0.3 wt%, extractives 0.7 wt%. The elemental analysis of Cherry samples has C:43.4, H:5.5, Oxygen: 51.2, Moisture: 9.0 and cypress sample analysis was C:44.5, H:5.7, Oxygen: 49.8, Moisture: 10.6. The elemental analysis was performed by Perkin
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Elmer C, H, N analyzer. The oxygen content was estimated from the difference of carbon, hydrogen and nitrogen. 2.2. Experimental Hydrothermal liquefaction experiments were conducted in a 200 ml TaS-02-HC type autoclave at 280 °C for 15 min. In a typical hydrothermal liquefaction experiment, the reactor was loaded with 5 g (dry basis) of biomass and 30 ml of aq. K2CO3 solution. Then the reactor was purged five times with nitrogen to remove the inside air. Reactants were agitated vertically at 60 ffi cycles/min using stirrer as shown in [28–30]. The temperature was then raised up to 280 °C at heating rate of 3 °C/min and kept for 15 min at 280 °C. After the reaction time, the reactor was cooled down to the room temperature by fan. The gaseous products were vented. The solid and liquid products were rinsed from the autoclave with ionexchanged water, then acidified to pH 1–2 with HCl (1.7 M) covered and kept in the refrigerator overnight (12 h). Solid and liquid products were separated by filtration under vacuum for 15 min. During filtration, 100 ml of ion-exchanged water were used for washing solid products. The liquid portion was extracted with equal quantity of diethyl ether (600 ml). The etheral solution thus obtained was dried over anhydrous sodium sulfate, filtered and evaporated in a rotary evaporator at room temperature. Upon removal of diethyl ether, this fraction was weighed and designated as oil 1. The water phase was further extracted with equal quantity of ethyl acetate (200 ml). The ethyl acetate solution thus obtained was dried over anhydrous sodium sulfate. Upon removal of ethyl acetate under reduced pressure, this fraction was weighed and designated as oil 2. After extraction, the remaining water phase contained the water-soluble hydrocarbons. Solid products were extracted with acetone (150 ml) in a Soxhlet extraction apparatus until the solvent in the thimble became colorless (about 20 h). After removal of the acetone under reduced pressure in a rotary evaporator, this fraction was weighed and designated as oil 3. Acetone insoluble fraction was dried at 105 °C then weighed, called as solid residue. All yields were calculated on a dry basis material and details for calculations of yields and separation of hydrothermal products can be found elsewhere [29,30]. The conversion is defined as the amount of solid biomass converted into other forms i.e., liquid, gas. Oils including oil 1, oil 2 and oil 3 obtained from low temperature hydrothermal liquefaction of wood biomass were analyzed by gas chromatograph equipped with a mass selective detector (GC–MS; HP 5973; column, HP-1). 3. Results and discussion The elemental composition of cherry and cypress wood biomasses shows that there are no significant differences in the elemental composition of two different wood biomasses. The elemental analyses of around 10 different
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wood biomass samples in the literature [31] are also showed the similar results. The composition of cherry and soft wood biomasses for lignin, hemicellulose, ash, extractives and cellulose were analyzed and it is clear from the data that the cypress (soft wood) is rich in lignin and cherry (hard wood) is rich in hemicellulose and cellulose. The lignin is ca. 3 times higher in the cypress (soft wood) biomass. The differences in the composition showed the remarkable differences in the composition of liquid hydrocarbons obtained with different solvents. The detailed information will be discussed in the following sections.
3.1. Product distribution Table 1(a) shows the product distributions obtained from hydrothermal treatment of cherry at 280 °C for 15 min with different concentration of aq. K2CO3 solution. The conversion of cherry in the absence of alkali solution showed around 70 wt% and with the increase of alkali solution concentration the conversion increased to 80 wt% at 0.25 M and further up to 96 wt% at 0.5 M. The conversion at 1 M concentration was ca. 99 wt% leaving ca. 1 wt% residue, which is equivalent to the ash content in cypress. It is interesting to see that the differences in the conversion of cypress at 0.5 and 1 M was around 3 wt%, however the total oil yield at 0.5 was 35 wt% and at 1 M was 48 wt%. It shows that the alkali solution increased the conversion and also the increase in the total oil yields with cypress. There are no significant differences in the yields of gaseous products with all experimental runs (run 1 to run 4 in Table 1 (a)) and the analysis gaseous products showed the major portion was carbon dioxide and traces of carbon monoxide, methane, ethane, and ethylene were found. The water soluble hydrocarbons (WSH) were around 30 wt% with and without alkali solutions, except with the 0.5 M concentration showing 43 wt%. Table 1(b) shows the product distribution from hydrothermal treatment of cypress at 280 °C for 15 min at different alkali concentrations. The conversion of cypress in the absence of alkali solution was 56 wt%, which is less than for cherry at the identical conditions. It shows that differences in conversions for
cherry and cypress comes from the differences in the composition of wood biomass and also macromolecular structure of wood biomass. In the absence of alkali solution, the total oil yield for cherry was 15.7 wt% and for cypress was 7.7 wt%. The presence of high hemicellulose and cellulose improved the conversions and total oil yields for cherry than cypress. The cypress conversions were found to increase with the increase of alkali concentration up to 0.5 M and there is no further increase in conversion with the concentration up to 1 M. At this concentration range, the cypress and cherry showed no significant conversion differences showing that the 0.5 M concentration is sufficient for high conversions. However, the total oil yields were increased up to 15 wt% in cherry from 0.5 M to 1 M but the effect could not be observed in cypress. Oil 1 and oil 2 yields were found to increase with the increase of alkali concentration and the oil 3 yields were highest (28.8 wt%) at 0.5 M concentrations for cypress than 1 M (23.3 wt%). It is understood that the decomposition of high cellulose wood biomasses favors the formation of watersoluble hydrocarbons rather than oily (water insoluble) compounds. It can be concluded that the decomposition of lignin or lignin rich wood biomasses in water (280 °C 15 min) is comparatively less than cellulose or cellulose rich samples [33]. Kadangode [34] investigated the lignin conversion in methanol at the temperature range 230–310 °C. It was reported that water/ether soluble hydrocarbons were also produced by decomposition of lignin. The yields of the products from hydrothermal treatment of biomass depends on the experimental conditions which includes, the type of biomass, reaction temperature, reaction time, solvent/biomass ratio, type of reactor and so on. We would like to stress that the pyrolysis process is different and should not be compared with the hydrothermal process as the presence of water or solvent strongly effects the product distribution and composition of each product.
3.2. Composition of oil products The identification of hydrocarbons from cherry oil 1 products was tabulated in Table 2. The formation acetic
Table 1 Products distribution from hydrothermal treatment of wood biomass at 280 °C for 15 min Run no.
(a) Cherry 1 2 3 4
Aq. K2CO3, M
Conv., wt%
Oil, wt% Oil 1
Oil 2
Oil 3
Total oil
Gas, wt%
Residue, wt%
Water solubles, wt%
0 0.25 0.5 1
69.0 80.0 96.0 99.0
7.6 10.4 15.6 17.1
1.0 3.7 2.9 5.6
7.2 10.4 16.4 25.5
15.7 24.5 34.9 43.2
19.9 23.8 17.7 19.7
30.7 20.4 4.3 1.3
33.6 31.3 43.1 30.8
(b) Cypress 1 0 2 0.25 3 0.5 4 1
56.3 80.3 95.7 94.9
20 16.5 17.4 20.0
1.1 3.4 5.7 5.2
4.5 20.2 28.8 23.3
7.7 42.1 52.0 49.5
9.9 12.5 9.8 10.0
43.7 19.7 4.3 5.1
38.8 23.7 34.0 35.4
T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
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Table 2 Identification of compounds by GC–MS in oil 1 from cherry hydrothermal treatment No.
RT, min
Name of compound
1 2 3 4 5 6 7 8 9 10
1.0 1.6 2.0 7.0 9.6 12.4 12.6 14.6 17.1 24.5
Acetic acid Propanoic acid 2-Furancarboxaldehyde Phenol 2-Methoxyphenol 2-Methoxy, 4-methylphenol Benzoic acid 1,2-Benzenediol-3-methoxy 2,6-Dimethoxyphenol Butylated hydroxytoluene
acid was found to increase with the addition of alkali up to 0.5 M (17. 43%) and further increase in alkali decreased the formation of acetic acid (7.45%). The results of chromatographic area (% of total area) belong to the identified compounds. The difference to 100% area represents the area of unidentified compounds. The amount of acetic acid was the highest in cellulose-derived oil 1 (ether extract) [33] and the present results are in good agreement with the hydrothermal upgrading of pure cellulose and lignin. The reason is that the cellulose produced mainly 2-furancarboxaldehyde and 5-methyl-2-furancarboxaldehyde. Cherry oil 1 products showed the around 23% of 2-furancarboxaldehyde and the compound could not found in cypress oil 1 (Table 2). The further decomposition of 2-furancarboxaldehyde and 5-methyl-2-furancarboxaldehyde products led to form acetic acid. The improvement in the formation of acetic acid and disappearance of 2-furancarboxaldehyde can be clearly seen in Table 2 for cherry hydrothermal treatment.
Area (%) 0
0.25 M
0.5 M
1.0 M
7.7 4.9 22.5 3.6 12.9 1.2 – 5.0 25.0 3.5
17.8 7.5 – 2.4 17.7 0.5 1.8 – 24.0 3.2
17.4 3.4 0.5 5.0 22.0 3.6 1.3 1.7 8.7 3.4
7.4 1.7 – 6.6 28.7 2.1 1.9 – 4.7 3.6
It can be clearly seen that the transformation of 2,6dimethoxyphenol to 2-methoxyphenol with the increase of alkali concentration (Table 2). Lignin-derived oil 1 predominantly contains 2-methoxyphenol with formation of other hydrocarbons such as 1,2-benzenediol, phenol, 3methyl-1,2-benzenediol. It is considered that initially 2methoxyphenol (as explained above) was formed and further decomposition produced 1,2-benzenediol and phenol derivatives [35]. The identification compounds in oil 2 from cherry were given in Table 3. The major compounds in oil 2 from the hydrothermal treatment in the absence of alkali solutions were 3-methylphenol had 27% and next 2,6-dimethoxy phenol. More than 30% of 1,2-butanediol was appeared at 0.5 and 1.0 M concentrations at oil 2 from cherry and the same compound couldn’t be found for 0.25 M and in the absence of alkali solution. The compounds in the oil 3 from cherry (Table 4) hydrothermal process showed that in the absence of alkali solutions
Table 3 Identification of compounds by GC–MS in oil 2 from cherry hydrothermal treatment No.
1 2 3 4 5 6 7 8 9
RT, min
1.0 7.9 10.1 10.5 10.9 13.0 17.1 19.8 20.9
Name of compound
Acetic acid 3-Methyl-2-cyclopentene-2-ol-one 3-Methylphenol 3-Butanoic acid 1,2-Butanediol 1-Butanol, 4-methoxy 2-6-Dimethoxyphenol 2-Ethoxy, 1-propanol 2,4-Pentanediol
Area (%) 0
0.25 M
0.5 M
1.0 M
10.5 27.5 – – – 17.2 – –
79.0 – – 2.9 – – 3.9 – –
11.3 – – – 37.6 3.3 4.5 5.3 –
16.0 – – – 32.7 2.6 – 11.0 16.0
Table 4 Identification of compounds by GC–MS in oil 3 from cherry hydrothermal treatment No.
RT, min
Name of compound
Area (%) 0
0.25 M
0.5 M
1.0 M
1 2 3 4 5
2.0 9.6 13.1 15.2 17.1
4-Hydroxy-4-methyl-2-pentanone 2-Methoxyphenol 2-Methoxy-4-ethyl-phenol 4-Ethyl, 2-methoxyphenol 2,6-Dimethoxyphenol
19.7 11.4 1.6 5.1 21.8
18.3 8.9 8.0 – 20.0
22.0 11.7 – 4.9 –
36.9 – – – –
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2-methoxyphenol and 2, 6-dimethoxyphenol and 4Hydroxy-4-methyl-2-pentanone was observed and with the increase of alkali solution concentration, the compounds such as phenolic derivatives could not been found. With the use of alkali solutions, these phenolic derivatives were concentrated in oil 1 and oil 2. The 4-hydroxy-4methyl-2-pentanone was found to increase with the increase of alkali concentration and it may be from the cleavage of benzene derivatives. The oil 3 is heavy molecular hydrocarbons portion and major portion of oil 3 hydrocarbons from 0.5 and 1 M cherry hydrothermal treatment could not be analyzed due to the limitation of GC/MS. The mechanism for formation of 2-furancarboxaldehyde and 5-methyl-2furancarboxaldehyde were reported by Jakab et al. [36]. The identification of hydrocarbons in oil 1, oil 2 and oil 3 from cypress hydrothermal treatment and with different alkali concentration were analysed and given in Table 5–7. The major hydrocarbon which was found to increase with
the increase of alkali concentration was found to be 2methoxyphenol and it is around 50 wt% at 0.25 and 0.5 M concentrations. In addition the formation of 1,2-benzenediol and its derivatives were found to increase with the increase of alkali concentration. Klein et al. [35] showed that the formation of 1,2-benzenediol from 2-methoxyphenol. The small decrease in the formation of 2-methoxyphenol from cypress oil 1 at 1 M concentration was substantiated with the formation of 1,2-benzenediol and its derivatives. There was no phenolic and benzenediol derivatives in the cypress oil 2 in all runs (Table 6). But, the 2-methoxyphenol and derivatives were found in oil 3 from cypress and 0.5 M concentration had more than 30% of 2-methoxyphenol. It is clear from the oil 1 and oil 3 that major portion of hydrocarbons from thermal and alkali hydrothermal treatment were found to be 2-methoxyphenol and benzenediol derivatives, the presence of phenolic derivatives were higher due to the presence higher lignin content in cypress than cherry.
Table 5 Identification of compounds by GC–MS in oil 1 from cypress hydrothermal treatment No.
1 2 3 4 5 6 7 8 9 10 11
RT, min
1.0 1.6 7.0 9.6 11.7 13.0 14.5 15.4 16.9 21.4 24.5
Name of compound
Area (%)
Acetic acid Propanoic acid Phenol 2-Methoxyphenol 1,2-Dimetioxybenzene 2-Methoxy, 4-methylphenol5l 1,2-Benzenediol 4-Ethyl, 2-methoxyphenol 1,2-Bezenediol, 3-methyl Butylated hydroxytoluene 4-Hydroxy-3-methoxy benezene acetic acid
0
0.25 M
0.5
1.0 M
– – 5.2 15.2 1.0 5.0 2.2 1.3 1.3 21.5 9.1
7.7 2.2 2.4 53.3 0.8 4.7 0.5 3.6 1.0 3.7 –
9.9 – – 48.9 0.7 3.3 – 1.6 0.8 2.8 1.2
2.7 – 1.2 34.9 2.1 5.0 18.3 3.9 12.6 2.3 –
Table 6 Identification of compounds by GC–MS in oil 2 from cypress hydrothermal treatment No.
1 2 4 5 6 7
RT, min
1.0 1.6 2.9 9.4 10.8 11.9
Names of compound
Acetic acid Propanoic acid 2-Methyl-2-cyclopentene-1-one Isopropyl alcohol 2-Butanol Cyclopropanecarboxylic acid
Area (%) 0
0.25 M
0.5 M
1.0M
20.2 3.4 1.0 – 5.4 4.0
54.0 – 2.3 1.3 – –
9.2 1.2 2.6 10.5 3.8 4.4
7.0 – – 7.4 9.7 –
0
0.25 M
0.5 M
1.0 M
7.6 24.0 12.0 – 11.5
44.9 – – – –
15.4 31.5 – 6.7 6.7
46.8 – – – –
Table 7 Identification of compounds by GC–MS in oil 3 from cypress hydrothermal treatment No.
1 2 3 4 5
RT, min
2.0 9.6 12.9 14.0 15.9
Name of compound
4-Hydroxy-4-methyl-2-pentone 2-Methoxyphenol 2-Methoxy, 4-methylphenol 1,2-Dimethoxybenzene 1,4-Dimethoxy-2-methylbenzene
Area (%)
T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
The GC–MS analysis data used for semi-quantitative analysis of hydrocarbons and presented the boiling point distribution of cherry and cypress biomass derived oils (ether extract), in the form of C–NP gram (Figs. 1 and 2) which was proposed to present the plastic derived oil [37]. Fig. 1 shows the composition of the oils (ether extract) obtained from cherry with different concentrations of alkali solution (aq. K2CO3) and Fig. 2 for cypress wood biomass. The carbon numbers in the abscissa represent the equivalent boiling point (B.P.) range of normal paraffin hydrocarbons. The details about C-NP gram can be found in elsewhere [37]. The hydrocarbons were distributed in the boiling point region n-C6 to n-C18 for all oils. The hydro-
2241
carbons in the n-C7 and n-C8 hydrocarbons were decreased with the increase of alkali concentration and hydrocarbons at n-C11 were found to increase with the increase of alkali solution and it is due to the phenolic derivatives (BP. range 200 °C). The hydrocarbons at n-C13 were found to decrease with the alkali and they are due to the decomposition of 2,6-dimethoxy phenol and its derivatives (BP range 235 °C). It can be seen from Fig. 1 (cherry) that there are three major peaks showing that the hydrocarbons were in three boiling point ranges in oil 1. Fig. 2 shows the boiling point distribution of hydrocarbons from oil 1 from cypress. It is clear from Fig. 2 that the more than 60% of hydrocarbons were concentrated at n-C11 which is due to
40 K 2 CO3 aq.
oil 1 compounds area %
35
0M
30 25
0.25 M
20
0.5 M
15
1.0 M
10 5 0 6
5
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Carbon num ber Fig. 1. C-NP gram of oil 1 obtained from cherry hydrothermal treatment at 280 °C for 15 min.
70 K 2 CO3 aq., 60
oil 1 compounds area %
0M 0.25 M
50
0.5 M 40 1.0 M 30
20
10
0 5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Carbon number Fig. 2. C-NP gram of oil 1 obtained from cypress hydrothermal treatment at 280 °C for 15 min.
20
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T. Bhaskar et al. / Fuel 87 (2008) 2236–2242
2-methoxyphenol and derivatives. This is the characteristic feature of the cypress hydrocarbons and presence of lignin higher portion clearly showed the formation of high quantity of phenolic derivatives than cypress, which has less lignin content. 4. Conclusions The hydrothermal upgrading of cherry and cypress wood biomasses whose lignin, hemicellulose and cellulose composition is different. The formation of acetic acid was pronounced in the hemicellulose and cellulose rich cherry than cypress. The formations of phenolic derivatives were higher in lignin rich cypress than cherry biomass. However, the total oil yields from both wood biomasses at 0.5 M concentrations were around 50 wt% and higher conversions (>95 wt%). Acknowledgements We thank Yonebayashi Milling Co., Ishikawa Prefecture, Japan for providing the biomass samples. Partial financial support from the Centre of Excellence Program for the 21st Century – Strategic Solid Waste Management for Sustainable Society at Okayama University to carryout the research work is highly appreciated. References [1] Anastas PT, Warner JC. Green chemistry theory and practice. Oxford: Oxford University Press; 1998. [2] Okkerse C, van Bekkum H. Green Chem 1999;1:107–14. [3] Bozell JJ, Patel MK. Feedstocks for the future. New York: ACS; 2006. [4] Stevens CV, Verhe RV. Renewable resources. Chichester: Wiley; 2004. [5] Ragauskas AJ, Williams CK, Davison BH, Britovsek G, Cairney J, Eckert AC, et al. Science 2006;311:484–9. [6] Clark JH, Budarin V, Deswarte FEI, Hardy JJE, Kerton FM, Hunt AJ, et al. Green Chem 2006;8:853–60. [7] Petrus L, Noordermeer MA. Green Chem 2006;8:861–7. [8] Inoue S, Okigawa K, Minowa T, Ogi T. Biomass Bioenergy 1999;16:377–83. [9] Aguado R, Olazar M, Jose MJS, Aguirre G, Bilbao J. Ind Eng Chem Res 2000;39:1925–33.
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