Preparation of carbon micro-spheres by hydrothermal treatment of methylcellulose sol
Introduction
In light of the problems of the depletion of fossil fuels, biomass resources will be important in the future as alternatives to the fossil resources. A large amount of cellulose, which is a main component of biomass, is produced annually by green plants and some organisms via photosynthesis [1]. One of the important derivatives of cellulose is methylcellulose which is water-soluble and extensively used as a binder or thickener in pharmaceutical, cosmetic, and food applications [2]. The conversion of cellulose and its derivatives to chemical materials has long been a goal for synthetic chemists, and many methods have been demonstrated which include acid catalysis [3], enzymatic saccharification and non-catalytic supercritical water treatment [4].
With the intrinsic characteristics of carbon materials such as light weight high thermal resistance high strength, etc., carbon spheres are expected to be used in composite materials, catalyst supports, lubricants and hydrogen storage media [5]. Most of commercial carbon micro-spheres are produced from the coal tar or petroleum pitch [6]. The synthesis of carbon spheres from the alternative precursors attracted considerable interests from both academic and industrial fields. Esumi et al. prepared carbon micro-beads from water-in-oil emulsion using amphiphilic carbonaceous material and urea [7]. Naka et al. reported that isotropic spherulitic carbon can be made by the pressure pyrolysis of divinylbenzene polymer sealed in a capsule.[8] Wang et al. developed mixed-valent oxide-catalytic carbonization (MVOCC) process to obtain carbon calabashes at 900–1000 °C [9]. Recently, Liu and Lou synthesized carbon spheres by using different metals to reduce carbonate or supercritical carbon dioxide [10], [11]. In this paper, we report a simple way for the preparation of carbon spheres by hydrothermal treatment of methylcellulose sol.
Section snippets
Experimental section
Prior to use, the original methylcellulose (with the trade name M450, provided by Shanghai Chemical Reagent Co., Ltd) in the form of fine white powder were vacuum-dried at 110 °C for 3 h. In a typical run, 1.0 g of powder was dispersed in 99 ml hot distilled water (70 °C) and stirred well, then kept at room temperature for 24 h. About 100 ml clear and transparent sol was obtained after the above procedure. The hydrothermal treatment of the sol was carried out in a stainless steel autoclave with
Results and discussion
The black products were analyzed by XRD on a Philips X'Pert X-ray powder diffractometer using Cu Kα radiation (λ = 1.541874 Å). Fig. 1 shows products prepared at different treating temperature with the sol concentration of 1.0 wt.%. There is no obvious reflection peaks in Fig. 1 (a); while a broad and weak peak at about 26° can be observed in Fig. 1 (b), which indicates the formation of amorphous carbon at 400 °C. The peak at ∼26° in Fig. 1 (c) becomes stronger with increasing temperature,
Conclusions
In summary, amorphous carbon micro-spheres with the diameter of several micrometers were synthesized by hydrothermal treatment of methylcellulose sol at 400 °C. Methylcellulose, as a biomass material, is abundant and non-toxic; the hydrothermal treatment without using organic solvent and surfactant makes our method a “green” process. The carbon spheres synthesized via this method may have potential application in fields such as drug delivery, anode material for Li-ion batteries, adsorbents and
Acknowledgement
This work was supported by the National Natural Science Foundation of China (20125103, 20321101 and 90206034).
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