【発明の詳細な説明】
本発明は木材の酸糖化、すなわちチツプ状木材
中のセルロースを希硫酸などを用いて糖化し、グ
ルコースなどの糖を製造する方法に関する。
従来、木材糖化法としては種々の方法が提案さ
れているが、この中で希酸を用いる方法としては
ａバツチ抽出式であるシヨーラー法、ｂ連続抽出
式である（チツプは回分にて詰め替え）マジソン
法、ｃ並流連続式である連続押出し法などがあ
る。しかしこれらの方法は糖収率が十分高くな
く、複雑な操作を必要とするなどの欠点があつ
た。例えばシヨーラー法の場合、反応槽に仕込ん
だ木材チツプを希酸によつて20回程度繰り返し抽
出を行い、抽出１回毎に新しい希酸を用いその滞
留時間を短くすることによつて生成グルコースの
分解を防ぎ糖収率を理論値の80％程度まで高めて
いる。しかしこの方法は木材チツプ単位当りに使
用する希酸の量がぼう大となり、したがつてグル
コース濃度が平均３％程度と低くなるため、別の
マイナス結果をもたらすこととなつた。またチツ
プを仕込み１回当りの反応終了時間も６時間以上
を要している。またマジソン法はチツプの仕込み
はバツチで行い、抽出を連続的に行う。マジソン
法の場合、抽出用希酸の供給速度を調節すること
により生成グルコースの滞留時間を調節すること
ができるが、その結果はシヨーラー法と同じ因果
関係となる。さらに連続押出し法は鋸屑などのチ
ツプを希酸と並流で連続供給するのであるが、糖
収率はバツチ式の場合と同様である。
本発明者らはこうした従来法の欠点を克服する
方法として向流法に着目し、向流法の利点を生か
すことのできるプロセスを開発するため検討を重
ねた結果、予め水蒸気処理などによつて、原料の
木材チツプを処理し、見掛け比重を高め、チツプ
を自然沈降可能な状態とすることにより、チツプ
と希酸を簡単に向流接触させることが可能である
ことを見出した。本発明はこの知見に基づきなさ
れるに至つたものである。
すなわち本発明は、木材を予め脱気して見掛け
比重を1.0より大としたのち塔状反応装置の上部
より供給し、下部より導入した希酸と向流式で接
触させることを特徴とする木材の糖化法を提供す
るものである。
本発明方法において予め木材組織内の空気を除
き（脱気し）比重を1.0より大とすることが必要
である。この脱気は好ましくは木材チツプを高温
の水蒸気で処理することにより行うことができ
る。水蒸気は通常約110℃の温度のものを用いて
行う。処理時間は特に制限はない。また脱気は上
記水蒸気処理の外、煮沸処理、減圧処理によつて
も行うことができるが、水蒸気処理が操作上最も
容易である。
木材は組織中に多数の空隙を有するため見掛け
比重は一般には１より小さいが、この脱気処理に
より木材組織中の空気を除き、その見掛けの比重
を1.0より大とする。水蒸気処理の場合は脱気さ
れた空隙中が水で満たされる。脱気した木材は塔
状反応装置の上部から塔内に連続的に供給され
る。
次に塔状反応装置の下部から導入する希酸の酸
濃度は、通常0.1〜〜5.0％の範囲である。酸濃度
が0.1％未満では加水分解反応速度が小さすぎ、
また５％を越えると酸消費量が多くなつて経済的
でない。酸としては硫酸などの不揮発酸が用いら
れる。こうして木材と希酸を連続的に向流式に接
触反応させ、木材の糖化を行う。木材チツプが希
酸液中を降下する間にチツプ中のヘミセルロース
及びセルロース成分は加水分解され、それぞれキ
シロース及びグルコースなどの糖となり、希酸中
に溶解し塔中を上方へ移動する。一方チツプ中の
リグニンは分解されず塔の底部に達し、塔外へ排
出される。塔状反応装置としては各種の縦型反応
管、反応塔が使用できる。
なお、チツプは前処理によつてヘミセルロース
を除いたもの、あるいは前処理を行わないもの、
いずれも用いることができる。
本発明方法において、上記以外は、従来法の糖
化法の条件に準じて行うことができる。処理温度
は160〜230℃で行う。酸液供給量は特に制限はな
い。
本発明方法の一実施態様としてのフローシート
を図面に示す。図中１は水蒸気処理装置、２は反
応塔であり、木材チツプ３は水蒸気処理装置１に
導入されて、水蒸気４が吹き込まれ脱気処理さ
れ、組織中の空隙は水で満たされる。こうして見
掛け比重1.0より大とされた木材チツプ５は反応
塔の塔頂部２ａに連続的に供給される。６は、反
応塔２の下部２ｂに連続的に導入される希酸であ
る。反応塔２内において、上方向に流れる希酸液
７中を木材チツプは降下し、該希酸と向流接触し
て希酸により加水分解が起き、生成した糖は希酸
中に溶解する。８は反応塔２から取り出されたグ
ルコースなどの糖を溶解した希酸液である。９は
塔底から抜出される酸分解されないリグニンであ
る。
本発明方法によれば、従来法では不可能であつ
た木材（セルロース）糖化を塔状反応装置を用い
て向流法で好適に実施でき、向流法の利点である
糖液濃度が高いチツプ詰め換え時間が不要―
単位反応容器当り処理量が大きい糖濃度が常に
一定―チツプバツチ仕込みの場合は変動幅が大き
いチツプ中の生成糖の抽出洗浄効果が良い―な
どを有するばかりでなく、同一条件下（温度、酸
濃度、酸液供給量など）での従来の方法に比較し
糖の分解率を低くして糖収率を約40％向上するこ
とができる。また連続法で実施できるので、単位
装置容積当りの処理量を大きくすることができ、
抽出効率を向上させることができる。さらにま
た、本発明方法は比較的簡単な設備で行えるとい
う利点を有する。
次に本発明方法を実施例に基づきさらに詳細に
説明する。
実施例 １
図面に示すフローシートに従い木材チツプを糖
化処理した。
（木材チツプの水蒸気処理）
耐圧容器にチツプ状木片（サイズ、20×10×７
mm，絶乾比重0.50のシラカバ材）を入れ、容器の
下部から約110℃の水蒸気を導入し、容器中の空
気を除去したのち、２分間110℃に保つた。続い
てチツプを希硫酸中に導入し冷却した。こうして
見掛け比重約1.10のチツプを得た。
（木材チツプの希硫酸加水分解）
縦型の加水分解反応管（断面積100cm2、長さ200
cm、希硫酸液柱高さ150cm）に190℃に調節した
0.5％希硫酸を満たし、さらに所定の給液速度で
反応管の下部より供給し、上部（底部から150cm
の位置）から排出した。
次に、190℃に予熱した上記水蒸気処理済みの
木材チツプをチツプ供給槽よりチツプ供給バルブ
を得て所定の速度で反応管上部から連続的に供給
したところ、チツプは反応管内を自然沈降によつ
て降下し反応管内を満たした。チツプが反応管内
に満たされたのち、反応管下部から反応を終了し
たチツプを所定の速度で残渣受槽へ排出バルブを
経て連続的に排出し、チツプの供給と排出をバラ
ンスさせた。反応器内におけるチツプの降下速度
は主にチツプ排出速度によつて調節した。また希
硫酸の供給量はチツプの排出に伴つて排出される
部分を考慮して調節した。
（実験結果）
加水分解反応が定常状態にある時の反応の結果
の一例を下記表に示した。
下記表から分るように、チツプを１時間当り
5000cm3、希硫酸液を１時間当り10の割合で供給
し、チツプ及び希硫酸液が反応管内を通過する時
間を共に140分としたとき、この発明の方法によ
るときはセルロースの加水分解率90％、グルコー
ス収率48％、グルコース液の濃度5.9％であつ
た。
一方チツプ供給量、希硫酸液供給量、反応時間
を同じ条件としてバツチ式及びマジソン法を行つ
た場合のグルコース収率及びグルコース液濃度は
それぞれ、バツチ式で33％，4.1％、マジソン法
で34％，4.2％であつた。
さらに条件を変えて同様の誌験を行つた結果を
下記表に併せて示した。
【表】DETAILED DESCRIPTION OF THE INVENTION The present invention relates to acid saccharification of wood, that is, a method for producing sugars such as glucose by saccharifying cellulose in wood chips using dilute sulfuric acid or the like. Conventionally, various methods have been proposed for wood saccharification, among which methods that use dilute acid are the Scholler method, which is a batch extraction method, and the continuous extraction method (b) (chips are refilled in batches). Examples include the Madison method and the continuous extrusion method, which is a cocurrent continuous method. However, these methods have drawbacks such as insufficient sugar yield and the need for complicated operations. For example, in the Schöller method, wood chips placed in a reaction tank are repeatedly extracted with dilute acid about 20 times, and by using new dilute acid for each extraction and shortening the residence time, the produced glucose is removed. It prevents decomposition and increases sugar yield to around 80% of the theoretical value. However, this method resulted in another negative result, as the amount of dilute acid used per unit of wood chips was large, resulting in a low glucose concentration of about 3% on average. In addition, it takes more than 6 hours to complete the reaction after preparing the chips. In addition, in the Madison method, chips are prepared in batches and extraction is performed continuously. In the case of the Madison method, the residence time of the produced glucose can be adjusted by adjusting the feed rate of the dilute extraction acid, but the result is the same causal relationship as in the Scholler method. Furthermore, in the continuous extrusion method, chips such as sawdust are continuously fed in parallel with the dilute acid, but the sugar yield is the same as in the batch method. The present inventors focused on the countercurrent method as a way to overcome the drawbacks of these conventional methods, and as a result of repeated studies to develop a process that can take advantage of the advantages of the countercurrent method, they found that discovered that it is possible to easily bring the chips and dilute acid into countercurrent contact by treating the raw wood chips to increase their apparent specific gravity and making the chips capable of natural sedimentation. The present invention has been made based on this knowledge. That is, the present invention is characterized in that the wood is deaerated in advance to have an apparent specific gravity greater than 1.0, and then the wood is supplied from the upper part of a tower reactor and brought into contact with dilute acid introduced from the lower part in a countercurrent manner. This method provides a saccharification method. In the method of the present invention, it is necessary to remove air from the wood structure (deaeration) in advance to make the specific gravity greater than 1.0. This deaeration can preferably be carried out by treating the wood chips with hot steam. Steam is usually used at a temperature of about 110°C. There is no particular limit to the processing time. In addition to the steam treatment described above, deaeration can also be carried out by boiling treatment or depressurization treatment, but steam treatment is the easiest in terms of operation. Since wood has many voids in its structure, its apparent specific gravity is generally less than 1, but this deaeration treatment removes air from the wood structure, making its apparent specific gravity greater than 1.0. In the case of steam treatment, the deaerated voids are filled with water. Degassed wood is continuously fed into the column from the top of the column reactor. Next, the acid concentration of the dilute acid introduced from the lower part of the tower reactor is usually in the range of 0.1 to 5.0%. If the acid concentration is less than 0.1%, the hydrolysis reaction rate is too low;
Moreover, if it exceeds 5%, the amount of acid consumed increases and is not economical. As the acid, a nonvolatile acid such as sulfuric acid is used. In this way, the wood and dilute acid are brought into continuous contact reaction in a countercurrent manner, and the wood is saccharified. As the wood chips descend through the dilute acid solution, the hemicellulose and cellulose components in the chips are hydrolyzed into sugars such as xylose and glucose, respectively, which dissolve in the dilute acid and move upward through the column. On the other hand, the lignin in the chips is not decomposed and reaches the bottom of the tower, where it is discharged outside the tower. As the columnar reactor, various types of vertical reaction tubes and reaction towers can be used. In addition, chips are those with hemicellulose removed through pretreatment, or chips that are not pretreated.
Either can be used. In the method of the present invention, the conditions other than those described above can be carried out according to the conditions of conventional saccharification methods. The treatment temperature is 160-230°C. There is no particular restriction on the amount of acid solution supplied. A flow sheet as an embodiment of the method of the present invention is shown in the drawings. In the figure, 1 is a steam treatment device, and 2 is a reaction tower. Wood chips 3 are introduced into the steam treatment device 1, and steam 4 is blown into them for deaeration treatment, and the voids in the structure are filled with water. The wood chips 5 whose apparent specific gravity is thus made larger than 1.0 are continuously supplied to the top 2a of the reaction tower. 6 is a dilute acid that is continuously introduced into the lower part 2b of the reaction tower 2. In the reaction tower 2, the wood chips fall through the dilute acid solution 7 flowing upward, come into countercurrent contact with the dilute acid, and are hydrolyzed by the dilute acid, and the produced sugars are dissolved in the dilute acid. 8 is a dilute acid solution taken out from the reaction tower 2 and in which sugar such as glucose is dissolved. 9 is lignin that is extracted from the bottom of the column and is not decomposed by acid. According to the method of the present invention, wood (cellulose) saccharification, which was impossible with conventional methods, can be suitably carried out using a countercurrent method using a tower reactor. No need for refilling time
Not only does it have a constant sugar concentration with a large throughput per unit reaction vessel (in the case of chip batch preparation, it has a good extraction and cleaning effect for the sugar produced in the chips, which fluctuates widely), but also under the same conditions (temperature, acid concentration). Compared to the conventional method, in which the decomposition rate of sugar is lowered and the sugar yield can be improved by about 40%, the sugar yield can be improved by about 40%. In addition, since it can be carried out in a continuous manner, the throughput per unit volume of equipment can be increased.
Extraction efficiency can be improved. Furthermore, the method according to the invention has the advantage that it can be carried out with relatively simple equipment. Next, the method of the present invention will be explained in more detail based on examples. Example 1 Wood chips were saccharified according to the flow sheet shown in the drawings. (Steam treatment of wood chips) Chip-shaped wood chips (size, 20 x 10 x 7
After introducing water vapor at about 110°C from the bottom of the container to remove the air in the container, the container was kept at 110°C for 2 minutes. Subsequently, the chips were introduced into dilute sulfuric acid and cooled. In this way, chips with an apparent specific gravity of approximately 1.10 were obtained. (Dilute sulfuric acid hydrolysis of wood chips) Vertical hydrolysis reaction tube (cross-sectional area 100cm 2 , length 200cm)
cm, dilute sulfuric acid column height 150 cm) and adjusted to 190℃.
Fill the reaction tube with 0.5% dilute sulfuric acid, and then supply from the bottom of the reaction tube at the specified liquid supply rate.
position). Next, the steam-treated wood chips preheated to 190°C were continuously fed from the top of the reaction tube at a predetermined rate using a chip supply valve from the chip supply tank. It then fell down and filled the reaction tube. After the chips were filled in the reaction tube, the chips that had completed the reaction were continuously discharged from the bottom of the reaction tube at a predetermined speed to the residue receiving tank via the discharge valve, thereby balancing the supply and discharge of chips. The rate of descent of the chips in the reactor was mainly controlled by the rate of chip discharge. Furthermore, the amount of dilute sulfuric acid supplied was adjusted in consideration of the amount of diluted sulfuric acid that would be discharged as chips were discharged. (Experimental Results) An example of the reaction results when the hydrolysis reaction is in a steady state is shown in the table below. As you can see from the table below, chips per hour.
5000cm 3 , dilute sulfuric acid solution is supplied at a rate of 10 parts per hour, and the time for both chips and dilute sulfuric acid solution to pass through the reaction tube is 140 minutes. When the method of this invention is used, the hydrolysis rate of cellulose is 90%. %, glucose yield was 48%, and concentration of glucose solution was 5.9%. On the other hand, when the batch method and Madison method are performed under the same chip supply amount, dilute sulfuric acid solution supply amount, and reaction time, the glucose yield and glucose solution concentration are 33% and 4.1% for the batch method, and 34% for the Madison method, respectively. %, 4.2%. Further, the results of a similar experiment conducted under different conditions are shown in the table below. 【table】
【図面の簡単な説明】[Brief explanation of the drawing]
図面は本発明方法の一実施態様を示すフローシ
ートである。
符号の説明、１……水蒸気処理装置、２……縦
型反応塔、３……原料木材チツプ、４……水蒸
気、５……脱気木材チツプ、６……希酸、７……
希酸液、８……糖溶解希酸液。
The drawing is a flow sheet showing one embodiment of the method of the present invention. Explanation of symbols, 1...Steam treatment device, 2...Vertical reaction tower, 3...Raw material wood chips, 4...Steam, 5...Degassed wood chips, 6...Dilute acid, 7...
Dilute acid solution, 8... Sugar dissolving dilute acid solution.