Morphological and structural differences between glucose, cellulose and lignocellulosic biomass derived hydrothermal carbons

Chemical, structural and energy properties of hydrochars from microwave-assisted hydrothermal carbonization of glucose

“…Falco et al [6], using conventional hydrothermal carbonization process, reported a maximum mass yield of about 40 % for glucose hydrochar at 200°C for 24 h, which is consistent with the maximum mass yield obtained in this study under microwave heating, despite the shorter time (45 min) in the microwave oven.…”

“…These variations, which increased with reaction time, are consistent with hydrothermal carbonization processes. The gradual increase in carbon content, and the decrease in hydrogen and oxygen contents of the hydrochars, with increase in processing time is due to loss of hydrogen and oxygen in deoxygenating, dehydration and decarboxylation reactions that occurred during the microwave-assisted hydrothermal carbonization process [6,22,26,27]. Despite the shorter time used in this study under microwave heating, the result is similar to previous studies [6,9].…”

“…Hence, processing time above 60 min was not considered. Maximum mass yield for the hydrothermal carbonization of glucose has been reported to be obtained at 200°C [6], while further increase in temperature will lead to a gradual decrease in mass yield; reason being that increase in temperature favors gasification reactions, which results in part of the hydrothermal carbon being lost in form of volatile compounds [22,23].…”

“…The sphere-like microparticles of different sizes (1-10 lm) seen on the SEM image of the hydrochar are in contrast to the block of materials observed in glucose. The mechanism in which these microparticles are generated is based on hydrolysis, dehydration and polymerization of glucose as stated in the mechanism, while the spherical nuclei are formed to minimize the energy of the interface [6,14].…”

“…Due to its simple operation, mild reaction conditions, and ability to exploit renewable biomass with minimal pre-treatment, it is of a particular environmental advantage when compared to other techniques of carbonization [5][6][7]. Among potential precursors used in the preparation of carbonaceous materials, glucose is very promising and its hydrothermal carbonization process has been studied several times using the conventional method of oven heating [6,[8][9][10]. However, the conventional hydrothermal process requires special systems that support pressure and temperature, usually an autoclave with pressure safety device is used.…”