Department of Biological Systems Engineering, University of Wisconsin - Madison, 460 Henry Mall, Madison, WI 53706, USA.
Biotechnol Biofuels. 2013 Jan 28;6(1):12. doi: 10.1186/1754-6834-6-12.
Lignin is one of the three major components in plant cell walls, and it can be isolated (dissolved) from the cell wall in pretreatment or chemical pulping. However, there is a lack of high-value applications for lignin, and the commonest proposal for lignin is power and steam generation through combustion. Organosolv ethanol process is one of the effective pretreatment methods for woody biomass for cellulosic ethanol production, and kraft process is a dominant chemical pulping method in paper industry. In the present research, the lignins from organosolv pretreatment and kraft pulping were evaluated to replace polyol for producing rigid polyurethane foams (RPFs).
Petroleum-based polyol was replaced with hardwood ethanol organosolv lignin (HEL) or hardwood kraft lignin (HKL) from 25% to 70% (molar percentage) in preparing rigid polyurethane foam. The prepared foams contained 12-36% (w/w) HEL or 9-28% (w/w) HKL. The density, compressive strength, and cellular structure of the prepared foams were investigated and compared. Chain extenders were used to improve the properties of the RPFs.
It was found that lignin was chemically crosslinked not just physically trapped in the rigid polyurethane foams. The lignin-containing foams had comparable structure and strength up to 25-30% (w/w) HEL or 19-23% (w/w) HKL addition. The results indicated that HEL performed much better in RPFs and could replace more polyol at the same strength than HKL because the former had a better miscibility with the polyol than the latter. Chain extender such as butanediol could improve the strength of lignin-containing RPFs.
木质素是植物细胞壁的三大组成成分之一，可在预处理或化学制浆过程中从细胞壁中分离（溶解）出来。然而，木质素的高价值应用却乏善可陈，最常见的提议是通过燃烧将其用于发电和产生蒸汽。有机溶剂乙醇法是木质生物质用于生产纤维素乙醇的有效预处理方法之一，而牛皮纸浆法是造纸工业中占主导地位的化学制浆方法。在本研究中，评估了有机溶剂预处理木质素和牛皮纸浆木质素，以替代多元醇生产硬质聚氨酯泡沫（RPF）。
用硬木乙醇有机溶剂木质素（HEL）或硬木牛皮纸浆木质素（HKL）替代石油基多元醇，在制备硬质聚氨酯泡沫时用量为 25%至 70%（摩尔百分比）。所制备的泡沫中含有 12-36%（w/w）的 HEL 或 9-28%（w/w）的 HKL。研究并比较了所制备泡沫的密度、压缩强度和细胞结构。采用扩链剂来改善 RPF 的性能。
发现木质素不仅是物理上被困在硬质聚氨酯泡沫中，而是通过化学键交联。含有木质素的泡沫在结构和强度方面具有可比性，当 HEL 或 HKL 的添加量达到 25-30%（w/w）或 19-23%（w/w）时。结果表明，HEL 在 RPF 中的性能更好，在相同强度下可以替代更多多元醇，因为与后者相比，前者与多元醇的混溶性更好。扩链剂如丁二醇可以提高含有木质素的 RPF 的强度。
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