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把含纖維素之廢木料直接經由液化反應變作合成油或石化原料，於1977年曾被美國能
源部擴大至試驗工場操作，結果試車不順，試驗停止。顯示有關整個液化機構，如觸
媒、還原氣等效應及何為變成油的中間物等，尚等探討。本研究選用純α─纖維素、
葡萄糖、乙二醇等作為基質，在水相下，用小型批式和部份連續式反應系統進行試驗
。由所得衍生物之組成與分佈，深討纖維素液化反應之過程，尤其著重於與石化原料
替代利用有關之含二個碳數有機物之衍生機構。
根據本研究所得結果推論：纖維素於300℃，20㎏/cm2 氮氣起始壓力下之液化反應，
產生有Ｃ2 脂肪族、Ｃ5 雜環有機物、水和碳渣等之反應機構包括如下：
(圖表省略)
其中葡萄糖產率，隨反應時間變化，先增而後減，糖化(saccarification) 或解聚
(depolymerization) 顯為起始液化重要步驟。以氣相層析一質譜儀分析液化反應之
衍生液，除水以外，結果檢出其產物以含二個碳數之Ｃ2脂肪族有機物與五個碳數之
Ｃ5 雜環有機物等二類為主。Ｃ2 主要成分為環氧乙烷(ethylene OXIDE)、
乙醛、乙二醇、醋酸和乙醇等。Ｃ5 主要成分為羥甲基糠醛(hydroxy methyl
furfural)、 糠醛、艀等。當以葡萄糖替代纖維素，在相同液化條件下，所得衍生
液組成分佈亦與以纖維素所得者相似。當續以乙二醇代替Ｃ2 產物，結果所得含二個
碳數有機物分佈與以纖維素液化所得者相似。顯示乙二醇對纖維素液化過程中Ｃ2 有
機物之衍生機構具有相當高度之模擬性。
另由Ｃ2 各主要成份當基質，並比照纖維素液化反應之條件進行反應，根據所得試驗
結果推測在纖維素或其葡萄糖單體之液化反應中，裂解生成之環氧乙烷應為關鍵性中
間產物，其可經由異構化(isomerization)轉變成乙醛，水合(hydration)轉變成乙二
醇，與不均化反應(disproportionation)轉變成醋酸和乙醇。以上反應經自由能變化
之分析，均屬可自然發生。因此對於Ｃ2 有機物之衍生過程可予以合理解說Ｃ2 有機
物可繼續分解成氣體產物，如醋酸分解為ＣＯ2 和ＣＨ4 等。
Appell對纖維素液化反應之機構，曾認為反應液中所添加之甲酸鈉具有可將羰基衍生
物還原成醇類之觸媒效應。但依本研究所得結果顯示甲酸鈉觸媒之添加，主要是中和
衍生液中酸性產物之酸性強度，以降低葡萄糖之脫山碳化速率；並可相對地增加Ｃ2
有機物之產率、降低Ｃ5 有機液體碳渣和水份等之產率之效應。Ｃ2 有機物中和乙醛
之產率，有隨甲酸鈉濃度增加而增加之趨勢，但無被還原成乙醇之現象。纖維素之液
化反應中改用苛性鈉或磷酸三鈉替代甲酸鈉亦得相似之結果。顯示纖維素等碳水化合
物在Appell之液化條件下Ｃ2 有機物如乙醛，或環氧乙烷等之衍生，與葡萄糖還原基
部份在鹼性之分解有關。推想該Ｃ2有機物之衍生係由1，2─脫水葡萄糖，斷裂出1，
2 環氧乙烷基部份，再經開環、異構化等反應衍生而成。另外通一氧化碳或氫氣等還
原氣體以還原Ｃ2 有機物之羰基變成醇類之效應不顯著。顯示添加甲酸鈉和一氧化碳
等並無如Appell所主張係作為還原劑之功能。由本研究所得結果希冀可供作為熱化學
處理纖維素材料，回收Ｃ2 有機物之參考。
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Studies on the Liquefaction of Cellulose-
Reaction Mechanism in Aqueous Condition
Abstract
The liquefaction of cellulosic wastes to oil and organic chemicals was
initiated by Appell and adopted by the Department of Energy of USA. In
1977, a pilot plant was constructed and tested by feeding wood chip, but
it was shut down later on account of the difficulties of operation. Some
basic data such as the reaction mechanism, the roles of alkali catalyst
and the effect of reducing gases etc. are being reviewed. The goal of this
research is to elucidate the above arguments especially for the derivation
of C2 organic chemicals and its significance. The experimental systems
include choosing pure polyhydroxyl substrates such as α-cellulose,
D-glucose and ethylene glycol as the model compound to compare the product
distribution. The substrate is dispersed in 90 wt% water content to
dissolve the intermediate and its derivatives. The bench scale reactors
which including batch and continuous type are being used.
Based on the products distribution data, the liquefaction pathways of
α-cellulose in 10 wt% content aqueous condition, at temperature 300℃ and
under pressure 20 ㎏/cm★ N2 are proposed as follows:
(圖表省略)
The yield of the intermediate, glucose, increases and then decreases with
the reaction time. It indicates saccarification or depolymerizaton is the
first reaction step. From GC/MS data, the disssolved liquid products,
except water, can be classified into two main groups. One is C2 aliphatic
oxygenated compounds such as ethylene oxide (EO), acetaldehyde, ethylene
glycol (EG), acetic acid (HOAC) and ethanol etc. The other is C5
heterocyclic compounds such as hydroxymethyl furfural (HMF), furfural,
furan etc. When D-glucose was used as the model intermediate compound for
reaction at the same liquefaction conditions, liquid products of similar
C2 and C5 compound pattern were obtained. These products are formed
through parallel reactions.
By using EG as the model compound of C2 products from cellulose, similar
C2 product distribution is observed. It shows EG possesing special
characteristics to trace the derivation of C2 products from cellulose.
When choosing other C2 products as the model compound, EO is shown to be
the key intermediates for C2 compounds. Through EO, acetaldehyde, EG,
HOAC, ethanol are formed via isomerization, hydration, and
disproportionation respectively. Further decomposition of C2 compound,
leads to gaseous products. CO2 is formed from decomposition of HOAC. All
the reactions proposed are thermodynamically favorable.
The catalyst effect of HCOONa which is proposed by Appell tto reduce the
carbonyl compound to alcohol derivatives is being compared with other
based such as NaOH and Na3PO4. They only neutralixe the acidity of the
derivatives, decrease the dehydration and carbonization rate of glucose,
and increase the yield of C2 compounds. The evidence of carbonyl reduction
as proposed by Appell could not be found. However, the yield of C5
compounds, char and water are decreased with the addition of the above
bases. The derivation of Cw compounds under base condition shows the
alkaline degradation of polysaccarides beginning at the reducing end of
the molecule and proceed in a stepwise manner through the anhydroglucose
unit. The C2 compounds seem to originate from the epoxy fragment of
1,2-anhydroglucopyranose which is cleaved after the dehydration of
glucose. For the addition of rducing gases such as CO and H2, no evidence
exists to convert the C2 carbonyl compound to ethanol. The above results
can supply useful data for the further utilization of cellulosic material
especially for C2 chemical production.
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