本文選題：木素模型物 + β-O-醚鍵��； 參考：《催化學報》2017年07期

【摘要】：隨著化石能源的日益減少,從木質生物質獲得能源、燃料和化學品變得至關重要.木素是木質生物質的第二大主要組分,但是目前遠未得到充分利用.隨著對木素結構的充分認識和相關催化科學技術的發(fā)展,由木素制得大宗燃料或精細化學品,特別是芳香類化合物顯示出越來越具有技術和經濟可行性.由于木質素大分子中復雜的C O和C C連接,先研究模型物的斷裂機理并同時考慮從木素模型物小分子遷移到木質素大分子的問題,然后設計出合適的催化材料并開發(fā)出可行的工藝過程,這條技術路線看起來更具有可行性.近年來,幾種均相或非均相多氧金屬鹽(Polyoxometalates(POMs),或稱雜多酸)用于降解木素或者木素模型物,但是β-O-4醚鍵斷裂的氫解還是酸解機理及其競爭合作作用尚不清晰.我們在幾種多氧金屬鹽(POMs)的催化下研究了β-O-4模型物2-phenoxyacetophenone(2-PAP)在以無水乙醇作為供氫溶劑體系下的催化斷裂機理和行為.結果表明,隨著無水乙醇溶劑處理溫度的提高,溶劑的供氫能力增強.酸性催化劑的加入提高了溶劑供氫能力.原因是催化劑的酸性改變了乙醇自氧化還原反應的平衡,使平衡向生成乙醛并釋放出活性氫的方向進行.我們還發(fā)現(xiàn),Cs-PMo的氧化還原性,對促進活性氫的釋放起更大的作用.2-PAP反應底物的加入消耗了活性氫,從而促使乙醇自氧化還原平衡向右移動.在酸性催化劑的作用下,2-PAP的轉化裂解可以按照氫轉移機制或酸催化的氧摀離子機制進行.大部分轉化反應按照哪個機制進行,取決于所采用體系的供氫能力和酸強度/數(shù)量的競爭關系,大部分反應將屈從于占競爭優(yōu)勢的機制.在強供氫及轉移能力占優(yōu)勢,而酸強較低酸量較少時,反應主要按氫轉移機制進行.在酸強很強且數(shù)量較多,反應將主要按酸催化氧摀離子機制進行.Cs-PMo這個擁有酸性和強氧化還原性的雙功能催化劑的使用,既促進了活性氫的釋放,又增強了活性氫的還原能力及轉移能力,因而導致了在極高轉化率(99%)的下極佳的選擇性(98.6%苯酚和91.1%苯乙酮).這些發(fā)現(xiàn)將對理解木質素中醚鍵的斷裂結果和機理提供啟示,為設計開發(fā)出木質素選擇性地催化裂解為芳香小分子的可行的工業(yè)過程打下初步理論基礎.
[Abstract]:With the decrease of fossil energy, it is very important to get energy from wood biomass. Lignin is the second major component of woody biomass, but it is far from being fully utilized. With the full understanding of lignin structure and the development of related catalytic science and technology, the preparation of bulk fuels or fine chemicals from lignin, especially aromatic compounds, shows more and more technical and economic feasibility. Because of the complex C / O and C / C junctions in lignin macromolecules, the fracture mechanism of the model compounds is studied and the problem of migration from small molecules of lignin model compounds to lignin macromolecules is considered at the same time. Then a suitable catalytic material is designed and a feasible process is developed, which seems to be more feasible. In recent years, several homogeneous or heterogeneous polyoxometalates have been used to degrade lignin or lignin models. However, the mechanism of hydrogenolysis or acidolysis of 尾 -O-4 ether bond and its competitive cooperation are not clear. The catalytic fracture mechanism and behavior of 尾 -O-4 model compound 2-phenoxyacetophenoneophenone 2-PAPs in anhydrous ethanol as hydrogen donor solvent were studied under the catalysis of several polyoxometalates (POMs). The results showed that the hydrogen donor capacity of the solvent increased with the increase of the temperature of ethanol solvent treatment. The addition of acid catalyst improved the hydrogen supply ability of solvent. The reason is that the acidity of the catalyst changes the equilibrium of the self-redox reaction of ethanol, which leads to the formation of acetaldehyde and the release of active hydrogen. We also found that the redox property of Cs-PMo plays a more important role in promoting the release of active hydrogen. The addition of substrates of 2-PAP consumes active hydrogen, thus promoting the self-redox equilibrium of ethanol to move to the right. The conversion and cleavage of 2-PAP under the action of acid catalyst can be carried out according to the mechanism of hydrogen transfer or the mechanism of acid catalyzed oxygen masking. The mechanism in which most of the conversion reactions take place depends on the hydrogen supply capacity of the system and the competitive relationship of acid strength / quantity. Most of the reactions will be subservient to the competitive advantage mechanism. In the case of strong hydrogen supply and transfer ability, the reaction was mainly carried out according to the mechanism of hydrogen transfer when the acid content was relatively low. When the acidity is very strong and the quantity is large, the reaction will be carried out mainly according to the mechanism of acid catalyzing oxygen covering ion. Cs-PMo, a bifunctional catalyst with acid and strong redox property, will promote the release of active hydrogen. The reduction ability and transfer ability of active hydrogen were also enhanced, which resulted in excellent selectivity of 98.6% phenol and 91.1% acetophenone at the very high conversion rate of 99%. These findings will provide enlightenment for understanding the fracture results and mechanism of ether bonds in lignin and lay a preliminary theoretical foundation for the design and development of a feasible industrial process for the selective catalytic decomposition of lignin to aromatic small molecules.
【作者單位】： 復旦大學化學系能原材料協(xié)同創(chuàng)新中心先進材料實驗室上海分子催化與創(chuàng)新材料重點實驗室;廣西科學院國家非糧生物質能源工程技術研究中心非糧生物質酶解國家重點實驗室廣西生物質工程技術研究中心廣西生物質產業(yè)化工程院廣西生物煉制重點實驗室;復旦大學化學系;
【基金】：supported by the National Key Basic Research Program of China(973 program,2013CB934101) National Natural Science Foundation of China(21433002,21573046) China Postdoctoral Science Foundation(2016M601492) International Science and Technology Cooperation Projects of Guangxi(15104001-5)~~
【分類號】：O636.2

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