Continuous recovery of high-purity Kraft lignin from black liquor via simultaneous, liquid-phase acidification and purification
Continuous recovery of high-purity Kraft lignin from black liquor via simultaneous, liquid-phase acidification and purification
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DOI：
10.1016/j.indcrop.2022.115084
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发表时间：
2022-05-25
影响因子：
5.9
通讯作者：
Thies, Mark C.
中科院分区：
文献类型：
--
作者：
Fitzgerald, Carter L.;Thies, Mark C.
从硫酸盐法黑液中回收木质素的连续液相木质素回收与提纯（SLRP）工艺的一个关键优势在于，在二氧化碳酸化步骤中会沉淀出一种溶剂化的 “液相木质素” 相（而非典型的固相）。在此，我们发现，如果将来自热剂水相木质素提纯（ALPHA）工艺的乙酸水溶液加入硫酸溶液中，那么在硫酸酸化步骤中，木质素也能保持溶剂化状态。当液相木质素从pH = 9.5的盐形式转变为pH = 2.5的酸形式时，最初被水溶剂化的木质素会被乙酸 - 水溶液溶剂化，进而液化。将木质素保持在溶剂化的液态有两个好处：（1）从起始黑液到最终木质素产品的整个SLRP + ALPHA工艺可以连续运行；（2）金属杂质从液相木质素相中的传质显著增强，这不仅能得到更纯净的硫酸盐木质素产品（钠含量约2000 ppm，灰分0.5 - 1.0%），还能减少水洗步骤。
A key advantage of the Sequential Liquid-Lignin Recovery and Purification (SLRP) process for the recovery of lignin from Kraft black liquor is the precipitation of a solvated, "liquid-lignin " phase (vs. the typical solid) during the CO2 acidification step. Here, we have discovered that this lignin can also be maintained in a solvated state during the H2SO4 acidification step if aqueous acetic acid from the Aqueous Lignin Purification with Hot Agents (ALPHA) process is incorporated into the H2SO4 solution. As the liquid-lignin is converted from its salt form at pH = 9.5 to its acid form at pH = 2.5, the lignin initially solvated with water becomes solvated and thus liquefied with the acetic acid-water solution. Maintaining the lignin in a solvated liquid state has two advantages: (1) the entire SLRP + ALPHA process, from starting black liquor to final lignin product, can be operated continuously; and (2) mass transfer of metals impurities out of the liquid-lignin phase is significantly enhanced, resulting in both a cleaner Kraft lignin product (~ 2000 ppm Na and 0.5-1.0% ash) and reduced water washing.