This study reports on a comparative study of acid hydrotropic fractionation (AHF) of birch wood using maleic acid (MA) and p‐toluenesulfonic acid (p‐TsOH). Under the same level of delignification, lignin dissolved by MA is much less condensed with a higher content of ether aryl β‐O‐4 linkages. Lignin depolymerization dominated in MA hydrotropic fractionation (MAHF) and resulted in a single lower molecular weight peak, in contrast to the competitive depolymerization and repolymerization in p‐TsOH AHF with a bimodal distribution. The less condensed MA‐dissolved lignin facilitated catalytic conversion to monophenols. Carboxylation of residual lignin in fractionated cellulosic water‐insoluble solids (WISs) enhanced enzymatic saccharification by decreasing nonproductive cellulase binding to lignin. At a low cellulase loading of 10 FPU g⁻¹ glucan, saccharification of WIS‐M_T120 from MAHF at 120 °C was 95 % compared with 48 % for WIS‐P_T85 from p‐TsOH AHF at 85 °C under the same level of delignification of 63 %. Residual lignin carboxylation also facilitated nanofibrillation of WIS for producing lignin‐containing cellulose nanofibrils (LCNFs) through an enhanced lignin lubrication effect, which substantially decreases fibrillation energy. LCNFs from only one pass of microfluidization of WIS‐M_T120 have the same morphology as those from WIS‐P_T85 after three passes. MA also has a lower solubility and higher minimal hydrotropic concentration, which facilitated acid recovery. MA is U.S. Food and Drug Administration (FDA)‐approved as an indirect food additive, affording significant advantages compared with p‐TsOH for biorefinery applications.

中文翻译：

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桦木可持续分馏的两种酸性水溶助长剂的比较。

这项研究报告了使用马来酸（MA）和对甲苯磺酸（p- TsOH）对桦木进行酸加氢分馏（AHF）的比较研究。在相同的去木质素水平下，MA溶解的木质素的凝结少得多，而醚芳基β-O-4键的含量更高。木质素解聚反应主要在MA水溶分馏（MAHF）中进行，并导致一个较低的分子量峰，这与p中竞争性的解聚和再聚合反应相反-具有双峰分布的TsOH AHF。溶解度较低的MA溶解的木质素有助于催化转化为单酚。分离的纤维素水不溶性固体（WIS）中残留木质素的羧基化通过减少非生产性纤维素酶与木质素的结合来增强酶促糖化作用。在10 FPU g的低的纤维素酶负荷^-1葡聚糖，糖化WIS-M的_T120在120从MAHF°与WIS-P 48％相比，C为95％_T85从p‐TsOH AHF在85°C的相同去木质素水平下为63％。残留的木质素羧化还通过增强的木质素润滑作用促进了WIS的纳米原纤化，以生产含木质素的纤维素纳米原纤维（LCNF），从而大大降低了原纤化能量。仅经过一遍WIS-M _T120微流化处理的LCNF与经过三遍经过的WIS-P _T85微流化处理具有相同的形态。MA还具有较低的溶解度和较高的最小水溶助长剂浓度，这有助于酸的回收。MA是美国食品药品监督管理局（FDA）批准的间接食品添加剂，与p- TsOH相比，在生物精炼应用中具有明显的优势。