Institute of Wood Science, Chemical Wood Technology, Universität Hamburg, Haidkrugsweg 1, 22885 Barsbüttel, Germany.
Molecules. 2020 May 5;25(9):2165. doi: 10.3390/molecules25092165.
In view of the expected increase in available waste medium-density fiberboard (MDF) and the current insufficient and unsatisfactory disposal capacities, efficient ways of recycling the waste material need to be developed. In this study, the potential of steam refining as a method to hydrolyze the resins, isolate fibers, and obtain a hemicellulose-rich extract available for further utilization in the context of a biorefinery was assessed. Two different MDF waste samples, as well as poplar () and spruce () wood chips for benchmarking, were treated over a severity range from 2.47 to 3.95. The separated fiber and extract fractions were analyzed with regard to yield, content of carbohydrates, acids, degradation products, and nitrogen. A fiber fraction of more than 70% yield and an extract containing up to 30% of carbohydrates for further processing can be gained by steam-refining waste MDF. At low severities, most of the nitrogen-based compounds are solubilized. Increasing the severity leads to a decrease in nitrogen in the extract as the nitrogen compounds are converted into volatiles. A non-hydrolysable resin residue remains on the fibers, independent of the treatment severity. In comparison to the benchmark samples, the extract fraction of waste MDF shows a high pH of 8 and high amounts of acetic and formic acid. The generation of furfural and 5-hydroxymethylfurfural (5-HMF) on the other hand is suppressed. Distinct differences in carbohydrate hydrolysis behavior between waste MDF and conventional wood can be observed. Especially, the mannose-containing constituents seem to be resistant to hydrolysis reactions in the milieu created in MDF fractionation.
鉴于可用废中密度纤维板（MDF）预计会增加，而目前的处理能力不足且不令人满意，因此需要开发有效的回收废料方法。在这项研究中，评估了蒸汽精炼作为一种水解树脂、分离纤维并获得富含半纤维素的提取物的方法的潜力，这些提取物可在生物精炼厂的背景下进一步利用。用苛刻度范围从 2.47 到 3.95 对两种不同的 MDF 废料样品以及作为基准的杨木（）和云杉（）木屑进行了处理。对分离出的纤维和提取物部分进行了产率、碳水化合物含量、酸、降解产物和氮的分析。通过蒸汽精炼废 MDF 可以获得产率超过 70%的纤维部分和含有高达 30%碳水化合物的提取物，可用于进一步加工。在低苛刻度下，大部分含氮化合物都溶解了。随着苛刻度的增加，由于氮化合物转化为挥发性物质，提取物中的氮含量会降低。无论处理苛刻度如何，纤维上都会残留不可水解的树脂残留物。与基准样品相比，废 MDF 的提取物部分具有 8 的高 pH 值和大量的乙酸和甲酸。另一方面，糠醛和 5-羟甲基糠醛（5-HMF）的生成受到抑制。可以观察到废 MDF 和常规木材之间在碳水化合物水解行为上存在明显差异。特别是，含甘露糖的成分似乎对 MDF 分馏中产生的水解反应具有抗性。
