木质素及造纸黑液热解制备酚类化学品基础研究
文献类型：学位论文
| 作者 | 彭翠娜 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 许光文 |
| 关键词 | 木质素 黑液 酚类化学品 碱催化 热解 |
| 其他题名 | Pyrolysis of lignin and black liquor for production of phenolic chemicals |
| 学位专业 | 化学工程 |
| 中文摘要 | 木质素是植物骨架的主要组分，每年通过光合作用可再生大约500亿吨木质素。作为自然界中唯一能提供可再生芳基化合物的可再生非石油资源，木质素是一种非常有潜力和前景的可再生资源。造纸黑液作为一种富含木质素的工业废弃物具有较大的利用价值。为了实现资源的高效利用，本文提出了造纸黑液的分级利用思路，即首先将造纸黑液降解来提取高附加值的含芳环的酚类化学品，再将剩余的残渣进行燃烧/气化回收其中的热量和碱。本论文主要研究热解木质素和造纸黑液生成高附加值酚类化学品的相关基础，包括常规热解和水热降解。 本论文获得的重要结果如下： 1. 碱催化热解木质素在提高酚类化学品收率。木质素在450℃快速热解得到的有机组分收率可达到16 wt.%（无灰基），主要包括2-甲氧酚、苯酚、2-甲氧基-4-烷基酚和烷基酚以及少量的醛酮类，其中酚类化学品含量较多，相对含量（TIC相对峰面积，被证明等价质量分率）达到46 wt.%。加入碱催化剂后热解焦油收率降到12-14 wt.%，而酚类化学品的相对含量增加到60-80 wt.%。强碱（NaOH、KOH）有利于甲氧酚的脱氧，主要促进了不含甲氧基的酚类化学品（烷基酚和苯酚）的生成，相对含量可分别达到66 wt.%和42 wt.%（加入被热解木质素20 wt.%的NaOH、KOH），加入与NaOH相同摩尔的KOH烷基酚相对含量达到78 wt.%，相同摩尔的KOH对烷基酚的促进作用强于NaOH。碳酸盐（Na2CO3、K2CO3）催化剂主要促进了含甲氧基酚类的生成，含甲氧基的酚含量在焦油中的相对含量占50-70 wt.%（加入木质素20 wt.%的碳酸盐）。 2. 黑液热解制备酚类化学品。黑液在450℃快速热解的有机组分收率达到15 wt.% （干燥无灰基），其主要组分为烷基酚、苯酚和2-甲氧酚，在450-500 ℃热解时烷基酚和苯酚相对含量达到60%。黑液热解的焦油中酚和烷基酚的含量高于提纯的黑液木质素在加入NaOH时热解的这两种酚的含量，由于黑液中的碱与木质素结合为酚钠盐，黑液中碱的自催化作用强于木质素与碱的物理混合情形。黑液残留半焦热值高于6300 kJ/kg，可将其燃烧/气化回收利用碱和热量，从而表明黑液的分级利用是可行的。 3. 木质素水热降解制取酚类化学品。木质素水热降解液体产物收率较高，甲醇/水可溶组分（即液体产物）收率达到50 wt.%（干燥无灰基），其中产物主要为儿茶酚、2-甲氧酚、苯酚、甲酚和香草醛等。木质素水热降解的可定量组分的最高收率可达12 wt.%（300℃，水/木质素比为20，120 min）。加入甲酸供氢剂，提高了儿茶酚、2-甲氧酚和甲酚的收率，各组分最大收率分别约6 wt.%、4 wt.%、2 wt.%，可定量组分收率达到18 wt.%（加入0.05 g甲酸）；加入甲酸钙0.05 g时儿茶酚、2-甲氧酚和甲酚的最大收率分别为6 wt.%、3 wt.%和3 wt.%。加入NaOH催化水热降解木质素促进了儿茶酚的生成，儿茶酚的收率增加到8 wt.%（木质素/NaOH比为4）；加入相同摩尔的碱催化降解木质素，强碱（NaOH、KOH）有利于甲酚和苯酚的生成，弱碱（Na2CO3、K2CO3）更有利于儿茶酚和2-甲氧酚的生成。在NaOH催化作用下，加入供氢剂（甲酸钠、甲酸钙、乙酸钠和乙酸钙），可定量组分的总收率在10-22 wt.%之间变化，对于可定量组分收率的影响作用的强弱为甲酸钠>乙酸钠>甲酸钙≈乙酸钙。在供氢剂的作用下，NaOH催化降解木质素各组分收率关系为儿茶酚>甲酚>2-甲氧酚，尤其在甲酸钠的作用下各组分收率最高达到22 wt.%，其中儿茶酚收率约16 wt.%。因此，水热条件下促进了木质素对酚类化学品的转化，碱催化降解有利于儿茶酚的生成。对比木质素在碱性催化剂作用下固定床的常规热解，水热降解具有一定的优势，儿茶酚的收率较高，达到8 wt.%，而进一步加入供氢剂甲酸钠时，儿茶酚收率高达16 wt.%。 4. 黑液水热降解制取酚类化学品。黑液水热降解的产物组分相对于木质素水热降解组分较多，在300℃条件下反应甲醇可溶组分（液体产物）含量约40 wt.%（干燥无灰基）。可定量组分儿茶酚、甲酚、苯酚等收率最高约8 wt.%，三者收率分别约为4 wt.%，2 wt.%、1 wt.%。随着反应时间的增长，儿茶酚收率先增大后减小，反应时间越长，易发生二次反应降低酚类收率。加入供氢剂提高了各组分收率，在甲酸盐的作用下，收率达到10 wt.%。黑液水热降解得到的主要产物为儿茶酚，其残渣干基热值约为7010 kJ/kg，也可将其燃烧利用。对比黑液的固定床常规热解和水热降解发现，黑液的水热降解液体产物中含有其他未定量的酚类，其液体收率较高，而且水热降解更适合高含水的黑液，采用黑液水热降解制备化学品具有一定的优势。 关键词：木质素, 黑液, 酚类化学品, 碱催化, 催化热解, 水热降解 |
| 英文摘要 | Lignin is a major component of biomass, and there are about 50 billion tons lignin on earth annually via photosynthesis. It is also the only renewable non-petroleum nature resource providing aromatic compounds. The pulp black liquor is a kind of industrial waste which is rich in lignin, and the value-added effective use of black liquor is significant and urgent. This work proposes the cascade utilization of pulp black liquor by first degradation to extract the chemicals containing aromatic ring and then combustion or gasification of the remaining residue for heat and alkali recovery. This thesis is devoted to investigating the production of phenolic chemicals from pyrolysis of lignin and black liquor including traditional dry pyrolysis and hydrolysis (or hydrothermal degradation). 1. Pyolysis of lignin with alkali catalyst to improve chemical production. The yield of organic substances or tar from lignin pyrolysis at 450 ℃ was up to 16 wt.% (dry ash-free basis), and the major chemicals in the tar were 2-methoxy-phenol, phenol, 2-methoxy-4-alkyl phenol, alkyl-phenols and small amounts of aldehydes and ketones. The content of phenols reached 46 wt.% (relative peak area of TIC but shown to be equivalent to the mass percent) of the total liquid. The yield of organics was reduced to 12-14 wt.% for the lignin pyrolysis with a kind of alkaline catalysts, and the content of phenolic chemicals in the produced organics (tar) increased to 60-80 wt.%. The formation of phenols free of -OCH3 group (alkyl-phenols and phenol) was promoted by using hydroxide catalysts (NaOH, KOH), and the resulting content of phenols in their tars was up to 66 wt.% and 42 wt.% (with 20 wt.% NaOH and KOH addition), respectively. For the same moles of alkaline catalyst, the deoxygenation effect of KOH was stronger than NaOH did to cause its content of alkyl-phenols to be 78 wt.% of the produced tar. The carbonates (Na2CO3、K2CO3) catalyst mainly improved the formation of methoxy-phenols, and the content of methoxy-phenols in the tar was 50-70 wt.% when the carbonate was 20 wt.% of the pyrolyzed lignin. 2. Pyrolysis of black liquor solids (BLS) for phenolic chemicals. The yield of organics from BLS pyrolysis at 450 ℃ reached 15 wt.% (dry ash basis), and the main phenolic chemicals included alkyl-phenols, 2-methoxy-phenol and phenol. The tar relative content of phenol and alkyl-phenols was 60 wt.% for BLS pyrolysis at 450-500 ℃ which was higher than NaOH-catalyzed pyrolysis of the purified lignin (PL) from black liquor. It is because the alkali existsing in the black liquor is in the form of phenolates and carboxylates, whose catalytic effect on the pyrolysis is better than the physically mixed (into lignin) alkali does. The heating values of the solid residue or char from pyrolyzing the dried black liquor was over 6300 kJ/kg, which can be combusted or gasified to recover energy and alkali to implement the cascade utilization of BLS. 3. Hydrothermal degradation of lignin for phenolic chemicals. From hydrothermal degradation of lignin the yield of methanol-soluable chemicals (produced liquid) was about 50 wt.% (dry ash-free basis), and the main products were catechol, 2-methoxy phenol, phenol, cresol and vanillin. The yield of quantifiable components can be up to 12 wt.% of the treated dry base lignin under conditions of 300 ℃, water/lignin=20 and reacting for 120 min. The yield of the quantifiable components can reach 18 wt.% with 0.05 g formic acid, and the yield of catechol, 2-methoxy-phenol and cresol were about 6 wt.%, 4 wt.%, 2 wt.%, respectively. Lignin hydrothermal degradation with 0.05 g calcium formate, the yield of catechol, 2-methoxy-phenol and cresol were about 6 wt.%, 3 wt.%, 3 wt.%, respectively. The alkaline catalysts (NaOH, KOH, Na2CO3, K2CO3) promoted the formation of catechol and its yield was about 8 wt.% with the same molar catalysts (Lignin/NaOH=4), hydroxides promoted cresol and phenol formation (NaOH, KOH), while carbonates (Na2CO3, K2CO3) |
| 语种 | 中文 |
| 公开日期 | 2015-07-08 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/15531]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 彭翠娜. 木质素及造纸黑液热解制备酚类化学品基础研究[D]. 中国科学院研究生院. 2014. |
入库方式： OAI收割
来源：过程工程研究所
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