Purpose

The pretreatment of biomass represents a large energy expenditure in the production of sugar alcohols. Current research efforts are focused on integrating catalytic processes to decrease operating time and reduce energy and raw material consumption. In this work, the hydrolysis-hydrogenation of hemicellulose for xylitol production direct from corncob was studied. It was used two strategies of hydrogenation: H₂ gas under pressure, and isopropanol as H₂ donor. The importance of the presence of H₂SO₄ and 5% Ru/C catalyst in the reaction medium was analyzed.

Methods

It was considered the use of H₂ pressure (2 MPa) and employing isopropanol (water-isopropanol 1:3) as a source of hydrogen. The reaction products were determined by HPLC.

Results

The 5% Ru/C catalyst was active and selective for the conversion of xylose to xylitol. To promote the hydrolysis of the hemicellulose fraction of the corncob into xylose, the addition of acid was necessary. Under mild conditions (0.1% H₂SO₄, 413 K), xylose was detected as the main product, indicating the good selectivity of the first hemicellulose conversion step. A xylitol yield was 19% under H₂ pressure while with isopropanol 7% was obtained.

Conclusion

The intermediate purification step was eliminated because as xylose was formed it was simultaneously hydrogenated to produce xylitol in the presence of Ru catalyst. Cellulose remained intact in the solid residue and could be used to obtain other products, such as glucose, sorbitol, ethanol, or charcoal.

Graphic Abstract

中文翻译：

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温和条件下水解加氢制玉米芯以获得木糖醇

目的

生物质的预处理代表了糖醇生产中的大量能量消耗。当前的研究工作集中在集成催化工艺上，以减少操作时间并减少能源和原材料消耗。在这项工作中，研究了半纤维素的水解加氢以直接从玉米芯生产木糖醇。它使用了两种氢化策略：加压的H ₂气体和异丙醇作为H ₂供体。分析了反应介质中存在H ₂ SO ₄和5％Ru / C催化剂的重要性。

方法

认为使用H ₂压力（2 MPa）并使用异丙醇（水-异丙醇1：3）作为氢源。通过HPLC确定反应产物。

结果

5％Ru / C催化剂具有活性，对木糖向木糖醇的转化具有选择性。为了促进玉米芯的半纤维素部分水解为木糖，必须添加酸。在温和条件下（0.1％H ₂ SO ₄，413 K），木糖被检测为主要产物，指示所述第一半纤维素转化步骤的良好的选择性。在H ₂压力下木糖醇产率为19％，而使用异丙醇则获得7％。

结论

消除了中间纯化步骤，因为在形成木糖的同时，在Ru催化剂的存在下将其同时氢化以生产木糖醇。纤维素在固体残渣中保持完整，可用于获得其他产品，例如葡萄糖，山梨糖醇，乙醇或木炭。

图形摘要