Lignocellulosic biomass from wood is a potentially rich source of glucose and xylose, which may be used either directly as monosaccharides or function as monomeric building blocks for a range of bioeconomy processes. In this paper we present a forthright separation of monosaccharides from other compounds present in the liquor after thermal biomass pretreatment. The main focus is on separation of xylose from acetate, formate and furans (hydroxymethyl furfural and furfural) by direct nanofiltration of sulphuric acid-hydrothermally pretreated birch liquor (a process optimized for xylose liberation from the biomass). In the study, the performance of eight commercially available flat-sheet membranes with different molecular weight cut-off was compared at 20 and 40 bars of pressure for efficient separation, focusing mainly on xylose retention. The nanofiltration membranes type TS40 (polypiperazine amide) and NF90 (polyamide) with cut-off of around 200 Da were found to be the most suitable for such direct detoxification of the liquor providing xylose retention over 98% and less than 20% retention of the accompanying thermal carbohydrate degradation compounds. The fouling mechanism during separation of the pretreated birch liquor appeared to be mainly cake-layer fouling on the surface of the membrane. Employment of diananofiltration resulted in particularly high purity (over 90%) and recovery (over 99%) of xylose after three diafiltration rounds. Moreover, the selected membranes exhibited great reusability, as the retention of monosaccharides was almost unaltered after five repeated nanofiltration cycles. The data provide new insight into the factors and mechanisms affecting membrane-separation of complex biomass liquors and are of significance for refining of lignocellulosic biomass.

木材中的木质纤维素生物质可能富含葡萄糖和木糖，可以直接用作单糖，也可以用作一系列生物经济过程的单体结构单元。在本文中，我们提出将单糖与热生物质预处理后的白酒中存在的其他化合物彻底分离。主要重点是通过对硫酸水热预处理的桦木液进行直接纳米过滤（从生物质中释放木糖的最佳工艺），将木糖与乙酸盐，甲酸和呋喃（羟甲基糠醛和糠醛）分离。在这项研究中，比较了八种不同分子量截留值的市售平板膜的性能，分别在20和40巴的压力下进行了有效分离，主要侧重于木糖的保留。发现截留值约为200 Da的TS40型纳米过滤膜（聚哌嗪酰胺）和NF90型聚酰胺膜（聚酰胺）最适合于这种液体的直接解毒，提供木糖保留率超过98％而保留率低于20％。伴有热碳水化合物降解化合物。分离桦树液的过程中的结垢机理似乎主要是膜表面上的饼层结垢。在经过三轮渗滤后，采用二氧化氮过滤可产生特别高的木糖纯度（超过90％）和木糖的回收率（超过99％）。此外，所选的膜表现出了很高的可重复使用性，因为在五个重复的纳滤循环后单糖的保留几乎没有改变。