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首页> 外文期刊>Separation and Purification Technology >Recovery of aliphatic low-molecular-mass carboxylic acids from hardwood kraft black liquor
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Recovery of aliphatic low-molecular-mass carboxylic acids from hardwood kraft black liquor

机译：从硬木牛皮纸黑液中回收脂肪族低分子羧酸

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摘要

During alkaline pulping of wood, substantial amounts of carbohydrates-derived aliphatic carboxylic acids (formic and acetic acids together with various hydroxy acids) are formed and dissolved into the cooking liquor ("black liquor"). These acids with low heating values are considered to be potential feedstocks for the chemical industry but, due to many factors, their straightforward recovery as free acids from black liquor (pH 13-14) is difficult. In this paper, we outlined the partial recovery of volatile formic and acetic acids from the acidified birch (Betula pendula) kraft black liquor (pH approximately 2.5) by distillation, and the partial recovery of significant low-molecular-mass alpha-hydroxy carboxylic acids (glycolic, lactic, and 2-hydroxybutanoic acids) by means of their volatile methyl esters. We noted that the maximum ester yields vary between 70% and 86% of the theoretical yield during the direct esterification (at 70 degrees C for 16 h) in the presence of a solid catalyst (a strong cation exchanger). Using this approach, we were able to separate the fractions of volatile and low-molecular-mass hydroxy acids from black liquor, while the crude faction of high-molecular-mass hydroxy acids (3,4-dideoxy-pentonic, 3-deoxy-pentonic, xyloisosaccharinic, and glucoisosaccharinic acids) remained as a residue. (C) 2015 Elsevier B.V. All rights reserved.
机译：在木材的碱性制浆过程中，大量的碳水化合物衍生的脂肪族羧酸（甲酸和乙酸以及各种羟基酸）形成并溶解到蒸煮液（“黑液”）中。这些具有低发热量的酸被认为是化学工业的潜在原料，但是由于许多因素，很难直接从黑液（pH 13-14）中将其作为游离酸回收。在本文中，我们概述了通过蒸馏从酸化桦木（Betula pendula）牛皮纸黑液（pH约2.5）中部分回收挥发性甲酸和乙酸的方法，以及部分回收重要的低分子质量α-羟基羧酸的方法。 （乙醇酸，乳酸和2-羟基丁酸）通过它们的挥发性甲酯。我们注意到，在固体催化剂（强阳离子交换剂）存在下，直接酯化（在70摄氏度下持续16小时）期间，最大酯收率在理论收率的70％至86％之间变化。使用这种方法，我们能够从黑液中分离出挥发性和低分子羟基酸的馏分，而粗分子则是高分子量羟基酸（3,4-二脱氧-戊基，3-脱氧-戊酸，木糖异糖酸和葡糖异糖酸保留为残留物。 （C）2015 Elsevier B.V.保留所有权利。

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