Hydrothermal carbonization (HTC) a thermochemical process, where biomass is treated with high-pressure high-temperature water. Hydrochar is a carbon-dense solid product from HTC with various oxygen functional groups on the surface. Among other process parameters, HTC temperature is one of the most dominant for hydrochar functional properties.  The surface functional groups on the surface of chars play a vital role to use them as an adsorbent. We have performed acidic and basic functional groups analysis for hydrochar at different HTC temperatures. Now, many of the functional groups could be submerged by the volatile material. Therefore, thermal activation or pyrolysis might be useful to further increase the concentration of functional group. However, dehydration is one of the major reactions for pyrolysis. As a result, there could be a competition between oxygen functional groups increase with dehydration.  Therefore, the objectives of this study was to quantify of oxygen functional groups and electron exchange capacities on activated hydrochars from model compounds (cellulose and wood). The hydrochars were pyrolyzed in a muffle furnace at three different temperatures (400, 500, and 600°C) for 1 hour. The change in functional groups on activated hydrochar surface was evaluated by surface morphology analysis, pH, Boehm titration, PZC, and FTIR. As prepared hydrochar shows relatively low surface area, mostly because of the lack of pores/ clogged pores with volatiles. An increase of surface area was observed but the oxygen functional groups were decreased with the increase of activation temperature as evident by the increase of pH, pKa, PZC.

Effect of pyrolysis temperature on various acidic and basic functional groups on hydrochar

2019 Fall National Meeting

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