碳纳米纤维负载Ni催化剂纤维素水解加氢工艺条件优化,Catalysis Today

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碳纳米纤维负载Ni催化剂纤维素水解加氢工艺条件优化
Catalysis Today ( IF 5.2 ) Pub Date : 2023-01-13 , DOI: 10.1016/j.cattod.2023.01.009
E. Frecha , J. Remón , D. Torres , I. Suelves , J.L. Pinilla

利用相对简单的制备方法和地球上丰富的金属，通过镍催化剂从纤维素合成山梨醇是生物炼制方案中一种有前途的增值途径。然而，总体选择性取决于复杂反应网络的动力学控制，包括纤维素通过纤维低聚物水解为单糖、葡萄糖氢化为山梨醇以及糖和山梨醇氢解为低分子量多元醇的副反应。其中，催化剂组成和工艺条件的细微变化可能会对最终产品的分布产生重大影响。在这些挑战的推动下，这项工作首次为碳纳米纤维支撑的镍催化剂（Ni/CNF）上纤维素的水热氢化提供了新的见解。首先，深入分析了球磨预处理步骤持续时间的影响以及水热时间和温度的影响。获得的实验结果强调了过程控制的重要性，以促进纤维素首次转化为葡萄糖以及随后氢化为山梨糖醇，以最大限度地减少副反应的扩展。最后，进行了另一项研究，通过将传质限制降至最低程度来缓解纤维素的顽固性质。这是通过对第一次预处理中产生的无定形纤维素与催化剂进行额外的混合研磨并增加水热氢化过程的氢气压力来实现的。这使得在 190 ℃ 下使用 8 MPa 的初始 H 压力持续 26 小时可以获得高达 62% 的山梨醇产率，这是文献中报道的最佳结果之一。

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Optimisation of the processing conditions of hydrolytic hydrogenation of cellulose using carbon nanofiber supported Ni catalysts

The synthesis of sorbitol from cellulose over Ni catalysts is a promising valorisation route in the biorefinery scenario, applying relatively simple preparation methods and earth-abundant metals. The overall selectivity, however, depends on the kinetic control of a complex reaction network, involving the hydrolysis of cellulose to monosaccharides via cello-oligomers, glucose hydrogenation into sorbitol and hydrogenolysis side-reactions of sugars and sorbitol to low molecular weight polyols. Therein, subtle changes in the catalyst composition and process conditions might have a strong impact on the final product distribution. Driven by these challenges, this work first-time provides novel insights into the hydrothermal hydrogenation of cellulose over a carbon nanofibre supported Ni catalyst (Ni/CNF). Firstly, the impact of the duration of a ball-milling pre-treatment step and the influences of the hydrothermal time and temperature were thoroughly analysed. The experimental results obtained highlighted the importance of process control to promote the first transformation of cellulose to glucose and its subsequent hydrogenation to sorbitol to minimise the extension of side reactions. Finally, an additional study was conducted to palliate the recalcitrant nature of cellulose by decreasing mass transfer limitations to a minimum extent. This was achieved by including an additional mix-milling of the amorphous cellulose produced in the first pre-treatment with the catalyst and increasing the H pressure of the hydrothermal hydrogenation process. This allowed attaining a sorbitol yield as high as 62% at 190 ºC using an initial H pressure of 8 MPa for 26 h, which is one of the best results reported in the literature.

更新日期：2023-01-13

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