Eucalyptus cellulose is usually pre-treated by oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), NaBr and NaClO at pH 10.5 and 25 °C before the mechanical process required to obtain cellulose nanofibers (CNFs). In this study, different aspects to improve the effectiveness and sustainability of the TEMPO-mediated oxidation are analyzed. The optimization was carried out at different reaction times by modifying both the concentration of the NaClO and the amount of the catalysts (TEMPO and NaBr). Results show that the carboxyl groups increased up to 1.1 mmol/g with 5 mmol NaClO/g after 50 min, and that the catalyst concentration can be reduced to 0.025 mmol TEMPO/g and 0.5 mmol NaBr/g to minimize costs while maintaining the high fibrillation degree of the CNFs. The kinetic of the reaction can be considered as zero-order with respect to NaClO, and as first order with respect to cellulose. As a result of this work, the catalyst doses are reduced up to 75% compared to the most widely used catalyst doses (0.1 mmol/g TEMPO and 1 mmol/g NaBr), obtaining highly fibrillated CNFs with a lower environmental impact. This reduction of catalyst doses will reduce the costs and facilitate the implementation of CNF production at industrial scale.

Graphical abstract

中文翻译：

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TEMPO介导的桉树纤维素氧化获得纤维素纳米纤维的试剂消耗优化

在获得纤维素纳米纤维 (CNF) 所需的机械工艺之前，桉树纤维素通常在 pH 10.5 和 25°C 下用 2,2,6,6-四甲基哌啶-1-氧基 (TEMPO)、NaBr 和 NaClO 进行氧化预处理。在这项研究中，分析了提高 TEMPO 介导氧化的有效性和可持续性的不同方面。通过修改 NaClO 的浓度和催化剂（TEMPO 和 NaBr）的量，在不同的反应时间进行优化。结果表明，5 mmol NaClO/g 50 min 后羧基增加至 1.1 mmol/g，催化剂浓度可降低至 0.025 mmol TEMPO/g 和 0.5 mmol NaBr/g，以最大限度地降低成本，同时保持高CNFs 的纤颤程度。反应的动力学可以被认为是相对于 NaClO 的零级，以及相对于纤维素的一级。这项工作的结果是，与最广泛使用的催化剂剂量（0.1 mmol/g TEMPO 和 1 mmol/g NaBr）相比，催化剂剂量减少了 75%，从而获得了对环境影响较低的高度原纤化的 CNF。这种催化剂剂量的减少将降低成本并促进工业规模的 CNF 生产的实施。

图形概要