木素的化學(xué)反應(yīng)ppt課件(編輯修改稿)
2025-05-29 18:02 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 HNO3+H2SO4， HNO3水溶液，濃HNO3 HNO3+CH3COOH， HNO3+（ CH3CO）2O等216。 硝酸與硫酸按下式作用，形成硝基陽(yáng)離子 NO2＋216。幾種硝化劑對(duì)木素反應(yīng)性的先后順序：216。反應(yīng)部位161。對(duì)具有酚羥基的木素模型物，硝化反應(yīng)發(fā)生在酚羥基的鄰位和對(duì)位161。對(duì)于酚羥基被醚化的化合物在間位，接著在對(duì)位亦起反應(yīng)161。木素單元側(cè)鏈脫除之后在對(duì)位導(dǎo)入硝基的同時(shí)，被氧化生成對(duì)醌樺木二氧六環(huán)木素樺木二氧六環(huán)木素木素及模型物的硝化反應(yīng) 五、木素的氧化反應(yīng)Oxidizing reactions of lignin167。 Reaction of hypochlorite with lignin167。 Reaction of chlorine dioxide with lignin167。 Reaction of hydrogen peroxide with lignin167。 Reaction of oxygen with lignin167。 Reaction of ozone with ligninThe main reaction types for bleaching！Introduction of bleaching167。 The existence of residual lignin after cooking167。 In order to obtain acceptable brightness167。 Two bleaching methods:216。 ligninremoving bleaching216。 ligninpreserving bleaching216。Delignifying bleaching chemicals: chlorine, chlorine dioxide, oxygen216。Ligninretaining bleaching chemicals: hydrogen peroxide, sodium dithioniteDevelopments of bleaching167。 Element Chlorine Free bleaching (ECF) —— 無(wú)元素氯漂白 Main bleaching agents are chlorine dioxide167。 Total Chlorine Free bleaching (TCF) —— 全無(wú)氯漂白 Main bleaching agents are hydrogen peroxide , oxygen and ozone（一） Reaction of hypochlorite with lignin167。 A mon bleaching chemical used for chemical pulp167。 Sodium hypochlorite solution is prepared by introducing chlorite gas to an aqueous solution of sodium hydroxide167。 Hypochlorite ion is a nucleophile attacking positively charged sites, it is also a strong oxidant and it can cleave carboncarbon bonds167。 Reactions during bleaching216。Oxidization is the dominate， there are also chlorination and radical reaction次氯酸鹽與木素發(fā)色基團(tuán)的降解反應(yīng) 167。 次氯酸鹽主要是攻擊苯環(huán)的 苯醌結(jié)構(gòu) (benzene quinone)和 側(cè)鍵的共軛雙鍵 (conjugated double bonds) 或縮合型木素 （ condensed lignin structure）216。與木素發(fā)色基團(tuán)發(fā)生親核加成反應(yīng)，形成環(huán)氧乙烷中間體，最后進(jìn)行堿性氧化降解，最終產(chǎn)物為 carboxylic acid pounds and carbon dioxide。216。如果木素結(jié)構(gòu)單元間尚存在 酚型 α 芳基醚 或β 芳基醚 連接，則這些連接將會(huì)斷裂并進(jìn)一步降解為有機(jī)羧酸和 CO2 木素與次氯酸鹽的反應(yīng) 鄰苯醌鄰苯二酚oxidizingBrief summary167。 Reactions of lignin with hypochlorite216。酚型結(jié)構(gòu)單元首先在苯環(huán)上發(fā)生親電取代反應(yīng)，生成氯化木素216。在次氯酸鹽作用下，脫去甲基，形成鄰苯二酚，繼而被氧化成鄰苯醌216。在堿性介質(zhì)中氯醌轉(zhuǎn)變成羥醌，并進(jìn)一步被次氯酸鹽所氧化，最終芳香環(huán)破裂，生成低分子的羧酸和二氧化碳。216。這種氧化降解作用，使木素大分子的 α 芳基醚或 β 芳基醚斷開(kāi)，并導(dǎo)致在結(jié)構(gòu)單元相連接的位置形成新的酚羥基，從而能再重復(fù)上述反應(yīng) （二） Reaction of chlorine dioxide with lignin167。 Chlorine dioxide is a new type efficient bleaching agent167。 It is made from sodium chlorate in the presence of reducing agents, ., sulfur dioxide167。 Characteristics：216。 It is difficult for chlorine dioxide to react with saturated aliphatic pound, for example, the alcohol, the amine and carboxylic acids216。 It is easy for ClO2 to react with unsaturated aliphatic pound167。 An electrophile and a rather selective oxidant216。Lignin and coloring matters were oxidized selectively and removed.216。Carbohydrates were not destroyed 愈創(chuàng)木基型木素結(jié)構(gòu)單元的二氧化氯氧化 紫丁香型木素結(jié)構(gòu)單元的二氧化氯氧化 Brief summary 167。 ClO2 attacks the phenolic hydroxyl group of lignin easily as a radical , and a series of oxidizing reactions continues216。 木素直接被氧化成鄰 苯醌和對(duì) 苯醌的反應(yīng)，使芳香環(huán)氧化裂開(kāi)生成己二烯二酸（粘康酸）衍生物的反應(yīng)216。 苯核上脫甲基并游離出新的酚羥基的反應(yīng)以及氯的取代反應(yīng)。216。 苯核和側(cè)鏈進(jìn)一步氧化碎解能生成草酸、氯乙酸、反丁烯二酸等。167。 Chlorine dioxide has almost pletely replaced sodium hypochlorite in the modern bleaching technique because of its superior deligninfication selectivity（三） Reaction of hydrogen peroxide with lig
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