Max-Planck Institute for Colloids, Research Campus Golm, D-14424 Potsdam, Germany.
Langmuir. 2011 Dec 6;27(23):14460-71. doi: 10.1021/la202361p. Epub 2011 Nov 3.
The objective of this paper is to better describe the structure of the hydrothermal carbon (HTC) process and put it in relationship with the more classical pyrolytic carbons. Indeed, despite the low energetic impact and the number of applications described so far for HTC, very little is known about the structure, reaction mechanism, and the way these materials relate to coals. Are HTC and calcination processes equivalent? Are the structures of the processed materials related to each other in any way? Which is the extent of polyaromatic hydrocarbons (PAH) inside HTC? In this work, the effect of hydrothermal treatment and pyrolysis are compared on glucose, a good model carbohydrate; a detailed single-quantum double-quantum (SQ-DQ) solid state (13)C NMR study of the HTC and calcined HTC is used to interpret the spectral region corresponding to the signal of furanic and arene groups. These data are compared to the spectroscopic signatures of calcined glucose, starch, and xylose. A semiquantitative analysis of the (13)C NMR spectra provides an estimation of the furanic-to-arene ratio which varies from 1:1 to 4:1 according to the processing conditions and carbohydrate employed. In addition, we formulate some hypothesis, validated by DFT (density functional theory) modeling associated with (13)C NMR chemical shifts calculations, about the possible furan-rich structural intermediates that occur in the coalification process leading to condensed polyaromatic structures. In combination with a broad parallel study on the HTC processing conditions effect on glucose, cellulose, and raw biomass (Falco, C.; Baccile, N.; Titirici, M.-M. Green Chem., 2011, DOI: 10.1039/C1GC15742F), we propose a broad reaction scheme and in which we show that, through HTC, it is possible to tune the furan-to-arene ratio composing the aromatic core of the produced HTC carbons, which is not possible if calcination is used alone, in the temperature range below 350 °C.
本文旨在更好地描述水热碳（HTC）工艺的结构，并将其与更经典的热解碳联系起来。事实上，尽管 HTC 的能量影响低，而且迄今为止已经描述了许多应用，但对于结构、反应机制以及这些材料与煤之间的关系却知之甚少。HTC 和煅烧过程是等效的吗？加工材料的结构是否以某种方式相互关联？HTC 内部多环芳烃（PAH）的程度是多少？在这项工作中，比较了水热处理和热解对葡萄糖（一种良好的模型碳水化合物）的影响；使用详细的单量子双量子（SQ-DQ）固态（13）C NMR 研究对 HTC 和煅烧 HTC 进行了研究，以解释对应于呋喃和芳族基团信号的光谱区域。将这些数据与煅烧葡萄糖、淀粉和木糖的光谱特征进行了比较。（13）C NMR 光谱的半定量分析提供了呋喃与芳族比值的估计，该比值根据处理条件和所使用的碳水化合物而在 1:1 至 4:1 之间变化。此外，我们提出了一些假设，这些假设通过与（13）C NMR 化学位移计算相关的密度泛函理论（DFT）建模进行了验证，这些假设涉及在导致缩合多芳族结构的煤化过程中可能出现的富含呋喃的结构中间体。结合对 HTC 加工条件对葡萄糖、纤维素和原始生物质（Falco，C.；Baccile，N.；Titirici，M.-M. 绿色化学，2011，DOI：10.1039/C1GC15742F）的广泛平行研究，我们提出了一个广泛的反应方案，并在其中表明，通过 HTC，可以调整组成所生产 HTC 碳的芳香核的呋喃与芳族比率，而如果单独使用煅烧，则在 350°C 以下的温度范围内是不可能的。
