外文翻譯--通過常壓醋酸工藝分餾小麥秸稈（英文）

1、Fractionation of wheat straw by atmospheric acetic acid process Sugwon Kim a,*, Yoshihiro Sano ba Division of Advanced Materials Engineering, RCIT, Chonbuk National University, Jeonju 561-756, Republic of Koreab Faculty

2、 of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, JapanReceived 7 June 2002; received in revised form 22 October 2004; accepted 22 October 2004 Available online 19 December 2004AbstractFra

3、ctionation of wheat straw was investigated using an atmospheric acetic acid process. Under the typical conditions of 90% (v/ v) aqueous AcOH, 4% H2SO4 (w/w, on straw), ratio of liquor to straw (L/S) 10 (v/w), pulping tem

4、perature 105 ?C, and pulping time 3 h, wheat straw was fractionated to pulp (cellulose), lignin and monosaccharides mainly from hemicellulose with yields of approx- imately 50%, 15% and 35%, respectively. Acetic acid pul

5、p from the straw had an acceptable strength for paper and could be bleached to a high brightness over 85% with a short bleaching sequence. Acetic acid pulp was also a potential feedstock for fuels and chem- icals. The ac

6、etic acid process separated pentose and hexose in wheat straw to a large extent. Most of the pentose (xylan) was dis- solved, whereas the hexose (glucan) remained in the pulp. Approximately 30% of carbohydrates in wheat

7、straw were hydrolyzed to monosaccharides during acetic acid pulping, of which xylose accounted for 70% and glucose for 12%. The acetic acid lignin from wheat straw showed relatively lower molecular weight and fusibility,

8、 which made the lignin a promising raw material for many prod- ucts, such as adhesive and molded products. ? 2004 Elsevier Ltd. All rights reserved.Keywords: Wheat straw; Acetic acid; Fractionation; Characterization; Lig

9、nin; Hemicellulose; Cellulose1. IntroductionWheat straw, an agricultural residue, is annually gen- erated in abundance around the world. The average yield of straw is 1.3–1.4 kg per kg of grain. In North America and Euro

10、pe, nearly 300 million tons of wheat straw are produced yearly (Montane ´ et al., 1998). Wheat straw is a lignocellulosic material containing about 35–40% cellulose, 30–35% hemicellulose, 10–15% lignin, 5–10% minera

11、l and small amount of other components. Although tremendous efforts have been attempted to convert it into value-added products, wheat straw has not yet been fully utilized, especially in developed coun-tries. Currently,

12、 besides remaining in the field to be incorporated into soil, wheat straw is mainly used for several applications. Pretreatment is usually needed to improve digestibility when wheat straw is used as livestock feed (Jacks

13、on, 1977; Flachowsky et al., 1996; Karunanandaa and Varga, 1996). In addition, extensive literature has been published concerning bioconversion of lignocellulosic materials to bio-chemicals and bio- fuels (Garde et al.,

14、2002; Berndes et al., 2001; Chum and Overend, 2001; Kaylen et al., 2000; Lee, 1997). Since lignocellulosic materials are only partially digest- ible in their native form, many mechanical, chemical and biological pretreat

15、ment processes have been pro- posed to make the subtracts susceptible to enzymatic and microbial action, such as steam explosion (Montane ´ et al., 1998), dilute acid hydrolysis (Grohmann et al., 1985), wet oxidatio

16、n (Klinke et al., 2002), autohydro- lysis (Lawther et al., 1996; Kubikova et al., 1996) and organosolv (Jime ´nez et al., 1997; Sun et al., 1997).0960-8524/$ - see front matter ? 2004 Elsevier Ltd. All rights reserv

17、ed. doi:10.1016/j.biortech.2004.10.018* Corresponding author. Present address: Department of Wood Science, University of British Columbia, 2424 Main Mall, Vancouver, BC, Canada. Tel.: +1 604 822 6775; fax: +1 604 822 910

18、4. E-mail address: xpan@interchange.ubc.ca (X. Pan).Bioresource Technology 96 (2005) 1256–1263with water, and subsequently lyophilized. The filtrate and washings of the lignin were collected and concen- trated using a ro

19、tary evaporator. The residue obtained was water-solubles, which are sugars mainly from hemi- cellulose degradation.2.3. Bleaching of acetic acid pulpPulp bleaching was performed using a three-stage sequence of E/P–D–P. H

20、ere, E/P, D and P stand for the three bleaching stages of alkaline extraction with peroxide, chlorine dioxide bleaching, and peroxide bleaching, respectively. Bleaching operation was con- ducted in a polyethylene bag in

21、a water bath. Bleaching conditions were E/P-stage, 5% NaOH and 1.0% H2O2 on pulp, 12% consistency, 80 ?C and 2 h; D-stage, 0.5% ClO2 on pulp, pH 4.5, 12% consistency, 70 ?C and 2 h; P-stage, 0.5% H2O2 on pulp, 12% consis

22、tency, pH 11, 70 ?C and 2 h, respectively. The pulp was thoroughly washed with water between stages and after bleaching.2.4. Determination of ash and silica in wheat straw and acetic acid pulpThe test specimen (3 g) was

23、weighed in a crucible, car- bonized gently over a Bunsen burner, and then ignited in a muffle furnace at 575 ± 25 ?C. The residue was weighed as ash. Because of the high silica content of wheat straw, ethanol soluti

24、on of magnesium acetate (5 ml), which contained 4.054 g of Mg(AcO)2 Æ 4H2O in 1 l of 95% aqueous ethanol, was added to the test spe- cimen to prevent incomplete incineration caused by fusion of ash and silica. At th

25、e same time, a blank deter- mination was done taking the same volume of the solu- tion of magnesium acetate. To determine the silica content in ash, the ash residue obtained above was trea- ted two times with concentrate

26、d HCl (36%, as received) to remove acid-soluble inorganic salts. The acid-insol- uble residue was filtered, washed with hot water until no chlorides were detectable with AgNO3, ignited, and finally weighed as silicon dio

27、xide.2.5. Estimation of acetyl groups in acetic acid pulp and ligninAcetic acid pulp (60 mg) or acetic acid lignin (50 mg) was suspended or dissolved in 6 ml of 1 M NaOH. Pro- pionic acid (10 mg) was added as an internal

28、 standard. The mixture was saponified at 60 ?C in a water bath with shaking for 2 h. After saponification, the pH of the mixture was adjusted below 2 with hydrochloric acid/water (1:1, v/v). Acetic acid in the supernatan

29、t was determined by gas chromatography (GC conditions: column Gaschropak 55, column temperature 170 ?C, injection temperature 250 ?C, carrier gas N2 at a flow rate of 30 ml/min, FID detector). Acetyl groups in aceticacid

30、 pulp and lignin were calculated from the amount of acetic acid determined above.2.6. Physical properties of acetic acid pulp and chemical analysisThe strength property tests of pulp handsheets were performed according t

31、o TAPPI T220 sp-96. Pulp viscos- ity was examined using TAPPI T230 om-99. Solvent extractives were determined using TAPPI T204 cm-97. Cold and hot water solubles were determined using TAPPI T207 cm-99. Alkali (1% NaOH) s

32、olubles were quantified according to TAPPI T212 om-98. Klason lig- nin was determined according to TAPPI T222. Acid sol- uble lignin was determined by UV spectra as described by Dence (1992). Nitrogen content was determi

33、ned by elementary analysis. Carbohydrate in wheat straw, pulp, and water-solubles was analyzed by gas chromatogra- phy according to alditol-acetates method of Borchardt and Piper (1970).2.7. Estimation of lignin molecula

34、r weightAfter acetylation (to make lignin soluble in mobile phase), the average molecular weight of acetic acid lignin was estimated by size-exclusion chromatography on an HPLC system (625 LC system, Waters Corporation,

35、Milford, Massachusetts, USA) with Shodex KF-G, 802 and 803 columns (Showa Denko, Tokyo, Japan). The columns were calibrated with authentic polystyrene. The lignin acetate (10 mg) was dissolved in 1 ml of tetra- hydrofura

36、n (THF) without stabilizer, and the solution was filtrated through 0.2 lm syringe filter prior to injec- tion. A sample of 10 ll was loaded on columns. THF was used as an eluent at a flow rate of 0.5 ml/min. Column tempe

37、rature was 40 ?C.2.8. Thermomechanical analysis (TMA) of ligninThermomechanical analysis of lignin was performed on a Thermal Analyzer (model 010, MAC SCIENCE, Hachioji, Japan) using a method based on changes in sample v

38、olume after heating, as described by Kubo et al. (1996).2.9. Experimental dataAcetic acid pulping results represent the mean of three replicate batches. Bleaching was performed in duplicate. Physical strength results of

39、pulp handsheets are the average of 10 measurements. Other analyses were conducted in duplicate. All results reported in the present research are mean valve ± standard deviation (SD). Standard deviation was calculate