Li Kena, Al-Rudainy Basel, Sun Mingzhe, Wallberg Ola, Hulteberg Christian, Tunå Per
Department of Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Department of Chemistry, Centre for Analysis and Synthesis, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Membranes (Basel). 2019 Aug 16;9(8):102. doi: 10.3390/membranes9080102.
One way of valorizing the lignin waste stream from the pulp and paper industries is depolymerizing it into low-molecular-mass compounds (LMMC). However, a common problem in the depolymerization of Kraft lignin is the low yields of small aromatic molecules obtained. In the present work, the combination of the repeated depolymerization of lignin and the separation of LMMC from depolymerized lignin to upgrade them into value-added chemicals was studied. In so doing, we investigated the possibility of depolymerizing black liquor retentate (BLR). The base-catalyzed depolymerization of BLR was performed using a continuous flow reactor at 170-210 °C, with a 2 min residence time. The results obtained indicate that BLR can be depolymerized effectively under the experimental conditions. Depolymerized lignin LMMC can be successfully separated by a GR95PP membrane, and thus be protected from repolymerization. Through combining membrane filtration with base-catalyzed depolymerization, more than half of the lignin could be depolymerized into LMMC. Around 46 mg/g of lignin monomers (guaiacol, vanillin, acetovanillone, and acetosyringone), which can potentially be upgraded to high-valued chemicals, were produced. On the basis of our results, we suggest use of a recycling Kraft lignin depolymerization and filtration process for maximizing the production of LMMC under mild alkaline conditions.
将制浆造纸工业产生的木质素废物流转化为有价值产品的一种方法是将其解聚为低分子量化合物（LMMC）。然而，硫酸盐木质素解聚过程中一个常见的问题是得到的小分子芳香族化合物产率较低。在本研究中，我们对木质素的重复解聚以及从解聚后的木质素中分离LMMC以将其升级为高附加值化学品的组合方法进行了研究。在此过程中，我们研究了解聚黑液截留物（BLR）的可能性。使用连续流动反应器在170 - 210°C下、停留时间为2分钟的条件下对BLR进行碱催化解聚。所得结果表明，在实验条件下BLR能够有效地解聚。解聚后的木质素LMMC能够通过GR95PP膜成功分离，从而防止其再聚合。通过将膜过滤与碱催化解聚相结合，超过一半的木质素能够解聚为LMMC。产生了约46 mg/g的木质素单体（愈创木酚、香草醛、乙酰香草酮和乙酰丁香酮），这些单体有可能升级为高价值化学品。基于我们的研究结果，我们建议采用循环硫酸盐木质素解聚和过滤工艺，以在温和碱性条件下最大限度地生产LMMC。
