本文關(guān)鍵詞： 木質(zhì)素 微波加熱 堿活化 固體堿 酚醛樹脂　出處：《福建農(nóng)林大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：木質(zhì)素做為含量僅次于纖維素的天然高分子化合物,它的高值化利用對于新能源開發(fā)、化工原料替代和環(huán)境保護(hù)等方面都具有非常積極的意義,然而天然木質(zhì)素結(jié)構(gòu)復(fù)雜,分子量一般在幾萬到幾十萬之間,反應(yīng)活性較低,因此長期以來無法對其進(jìn)行充分利用,是一種極大的能源浪費。本論文以禾草類玉米芯木質(zhì)素為研究對象,利用其分子中大量存在的醚鍵在不同堿性催化劑催化下的斷裂反應(yīng),得到低分子量、多羥基官能團的活性降解產(chǎn)物,用以替代酚醇類物質(zhì)制備木質(zhì)素基酚醛樹脂(LPF),實現(xiàn)木質(zhì)素的資源化利用。首先,根據(jù)國內(nèi)禾草類植物產(chǎn)量豐富的特點,選取玉米芯木質(zhì)素為研究對象。采用元素分析、GPC、FT-IR、UV、1H-NMR、TG等分析手段分析了原料玉米芯木質(zhì)素的元素組成、官能團結(jié)構(gòu)、酚羥基數(shù)量、熱分解性能等。研究結(jié)果表明原料木質(zhì)素的分子量較大,分子量分布較為寬泛,難以直接用于酚醛樹脂的合成。木質(zhì)素中有著較高的苯環(huán)含量,同時由于氫、氧元素在木質(zhì)素中所占相對比重較大,因此醚鍵、甲氧基、羥基等特征官能團的相對含量也較高。其次分別以NaOH、KOH傳統(tǒng)堿為催化劑,在微波輔助下水熱活化降解木質(zhì)素。探究了微波與常規(guī)加熱方法,反應(yīng)溫度、反應(yīng)時間、木堿比等因素對木質(zhì)素堿活化降解反應(yīng)的影響規(guī)律。實驗結(jié)果表明,木質(zhì)素的堿活化降解反應(yīng)主要發(fā)生的是醚鍵的水解斷裂,生成了新的酚羥基衍生物,微波加熱可以大幅度提高活化降解反應(yīng)的速度與效率。同時確立了這兩種不同堿微波水熱降解木質(zhì)素的最優(yōu)工藝條件:反應(yīng)溫度160℃,反應(yīng)時間45 min,木堿比1:1,在此條件下木質(zhì)素的重均分子量分別降低到2100和1840,酚羥基含量分別增加58.4%和50.8%。采用浸漬法制備出負(fù)載型CaO/MgO和KOH/SBA-15固體堿催化劑,在微波輔助下采用固體堿活化降解木質(zhì)素。優(yōu)化了固體堿催化劑制備條件,同時考察了兩種固體堿在不同的實驗條件下的降解效率。實驗發(fā)現(xiàn),固體堿的堿度越大,催化效率越大,在最佳制備工藝條件下CaO/MgO固體堿的堿度最高可達(dá)29.2,KOH/SBA-15固體堿的堿度最高可達(dá)18.9。同時降解產(chǎn)物的表征結(jié)果表明,與玉米芯木質(zhì)素相比,降解木質(zhì)素的酚羥基含量明顯升高,增長量最高分別可達(dá)78.2%和70.2%,甲氧基含量降低,分子量及其分布系數(shù)也有一定程度的降低,同時降解反應(yīng)后木質(zhì)素分子更加簡單均一,木質(zhì)素的活性官能團酚羥基數(shù)量提升,反應(yīng)活性得到增強,使其更適用于制備木質(zhì)素基酚醛樹脂膠。最后使用降解改性后的玉米芯木質(zhì)素替代和部分替代苯酚,合成LPF膠,并對LPF膠的基本性能進(jìn)行檢測。實驗結(jié)果表明使用傳統(tǒng)堿活化和固體堿活化的木質(zhì)素合成的LPF膠都具有良好的性能,符合國家標(biāo)準(zhǔn)的要求,當(dāng)改性木質(zhì)素替代苯酚的量達(dá)到50%時,制備出的LPF膠工業(yè)化利用價值最高。
[Abstract]:Lignin, as a natural macromolecule, is second only to cellulose in content. Its high value utilization is of great significance for the development of new energy, the substitution of chemical raw materials and environmental protection. However, the structure of natural lignin is complex, the molecular weight is generally between tens of thousands and hundreds of thousands, the reaction activity is low, so it can not be fully utilized for a long time. It is a great waste of energy. In this paper, the low molecular weight was obtained by using the cleavage reaction of ether bond in gramineous corncob lignin under the catalysis of different basic catalysts. The active degradation products of polyhydroxyl groups are used to replace phenols to prepare lignin-based phenolic resin LPFs to realize the utilization of lignin. First of all. According to the rich yield of grasses in China, corncob lignin was selected as the research object, and the elemental analysis of GPC-FT-IRU UVN 1H-NMR was used. The elemental composition, functional group structure, phenolic hydroxyl content and thermal decomposition properties of the raw corn cob lignin were analyzed by TG and other analytical methods. The results showed that the molecular weight of the raw material lignin was high. The molecular weight distribution is relatively broad, it is difficult to be directly used in the synthesis of phenolic resin. Lignin has a higher benzene ring content, and because of the relatively large proportion of hydrogen and oxygen elements in lignin, so ether bond, methoxyl. The relative content of characteristic functional groups such as hydroxyl groups is also high. Secondly, the traditional NaOHHHOH base is used as catalyst to degrade lignin in water with microwave assisted thermal activation. The microwave and conventional heating methods are explored. The effects of reaction temperature, reaction time and ratio of lignin to alkali on the activation and degradation of lignin were studied. A new phenolic hydroxyl derivative was synthesized. Microwave heating can greatly improve the rate and efficiency of the activated degradation reaction. The optimum conditions of these two kinds of alkali microwave hydrothermal degradation of lignin were established: reaction temperature 160 鈩，

本文編號：1492062