Hydrothermal carbonisation (HTC) of biomass (aqueous treatment of aqueous solutions at temperatures between 150°C and 250°C under autogenous pressure) has been proposed as an alternative solution to pyrolysis for producing functional carbons with controlled texture. Parameters such as the size and shape of the hydrothermal carbon particle and the surface area have strong importance in applications such as stationary phases for HPLC or supports for heterogeneous catalysts. As HTC involves very complex chemical mechanisms, it is possible that the reaction conditions and the presence of salts also influence the shape and format of particles obtained by HTC. In this work, we describe the effects of different parameters (reagents concentration, reaction time, temperature and different salts) on the morphology of hydrothermal carbon obtained from simple sugars (glucose and xylose) and their correspondent biomass polymers (cellulose and xylan). The simple addition of NaCl, resulted in a tremendous increase of the average diameter of the carbon spheres obtained from glucose (0.44 ± 0.2 µm) compared to the ones obtained with water (5.1 ±1.7 µm) for a reaction time of 24 h at 180°C. The particle size distribution, in water, had a low polydispersity, while with NaCl, it is multidisperse. In the case of NaF, the effect is even stronger: the spherical morphology is completely lost in favour of the formation of very large slabs (see Figure 1). The effect of temperature is different depending on the media (water, NaCl or NaF solutions). Different techniques were used to characterized both liquid and hydrochars (SEM-EDX, TOC, FT-IR, solid 13C NMR, GC-MS, BET and elemental analysis) and will be presented in detail. Different cations (H+, Li+, Na+ and Cs+) and anions (F-, Cl-, I-, and OH-) were also and the corresponding results will also be presented.

Effects of hydrothermal carbonisation (HTC) conditions on the morphology of hydrocarbon particles obtained from biomass mono/polysaccharides

251st National Meeting (2016)

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