Preparation and Characterization of Hydrochars Produced from Date Pits via Hydrothermal Carbonization
K. Irem Er, Ademi Kinayatova, Selhan Karagoz, Koray Alper, Kubilay Tekin
article (Uluslararası, Hakemli) | Yazar(lar): K. Irem Er, Ademi Kinayatova, Selhan Karagoz, Koray Alper, Kubilay Tekin | Yıl: 2027 | Dergi/Kurum: JOURNAL OF MOLECULAR STRUCTURE | İndeks: WOS.SCI | DOI: 10.1016/j.molstruc.2026.147524 | Anahtar Kelimeler: Hydrothermal carbonization, hydrochar, date pits, agro-industrial
This study systematically investigated the hydrothermal carbonization of date pits (Phoenix dactylifera L.) to evaluate the effects of reaction temperature (200-275 degrees C), residence time (4-24 h), biomass-to-water ratio (1:10-3:10), and process water recirculation on the yield and physicochemical properties of the resulting hydrochars. Reaction temperature was identified as the dominant parameter governing hydrochar properties. Increasing temperature from 200 to 275 degrees C progressively enhanced the carbon content (60.69 to 74.25 wt%, dry ash-free basis), fixed carbon content (26.24 to 47.57 wt%), and higher heating value (23.32 to 29.25 MJ kg-1), while reducing volatile matter content, hydrogen-to-carbon and oxygen-to-carbon atomic ratios. Van Krevelen diagram analysis confirmed the progressive coalification of date pit-derived hydrochars toward the lignite region with increasing hydrothermal carbonization severity. Thermogravimetric analysis demonstrated a marked improvement in thermal stability with increasing temperature, as evidenced by the shift of the maximum degradation temperature from 368 to 447 degrees C and the increase in residual mass from 31 to 55 wt% at 850 degrees C. Fourier transform infrared spectroscopy and X-ray diffraction analyses confirmed the progressive decomposition of polysaccharide structures and increasing aromatization of the hydrochar matrix. Residence time and biomass-to-water ratio exerted comparatively minor effects on hydrochar properties. Process water recirculation over three successive cycles did not compromise hydrochar quality, demonstrating its feasibility as a strategy for improving the industrial applicability of the hydrothermal carbonization process. These findings demonstrate that date pits represent a promising lignocellulosic feedstock for the sustainable production of energy-dense solid biofuels.