Preparation And Properties Research Of Bio-based Hydrochar

Due to the advantages of less restriction for moisture content of raw material, low energy consumption and low CO2 release, hydrothermal carbonization has become an efficient pre-treatment and all-components conversion method for biomass. In China, the production yield of biomassis huge. However, their effective utilization is poor evev produce environment impact. Therefore, applied hydrothermal carbonization to the biomass treatment processing has great significance for our environment and economy.In this work, rice straw, larch and poplar wood hydrochar were prepared via hydrothermal carbonization. The morphology structure, microcrystalline structure or surface chemical property were detected by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy(XRD), infrared spectroscopy or thermal analysis(TG). For rice straw and larch hydrochar, adsorption capacity and slow-release property were tested. N-doping porous carbon was prepared with larch wood hydrochar as substrate, KOH as activating agent, and melamine as nitrogen source. And electrochemical performance of N-doping porous carbon was tested. Poplar wood hydrochar were activated with CO2 as activated gas, and the textural parameters of prepared activated carbon were analyzed by N2 adsorption-desorption. The following is the main content of this work.Rice straw hydrochar samples were prepared by hydrothermal carbonization with rice straw as raw materials. Hydroxyl, carbonyl, carboxyl, ester and ether groups were detected. The crystallization peak strength of rice straw hydrochar increased with the increase of the hydrothermal temperature. The result of the adsorption test for heavy metal showed that:the adsorption ability of hydrochar for Cd2+ and Pb2+ is different. Meanwhile, for Cd2+, hydrochar has stronger adsorption ability. The sample prepared under 220℃(RS22o) has the highest adsorption ability for Cd2+,287.606mg/g. The sample prepared under 260℃ (RS260) has the highest adsorption ability for Pb2+,213.3 mg/g.Larch hydrochar samples were prepared by hydrothermal carbonization with larch chips as raw materials. Carbon spheres were generated on the surface of larch hydrochar, and all had good shape and smooth outer surface. When the hydrothermal temperature increased to 260℃, surface oxygen-contained groups of hydrochar decreased, and the microcrystalline structure of hydrochar transferred into amorphous structure. The result of fertilizer slow-release showed that the fertilize(1-3) synthesized with 3:1 ratio by urea and hydrochar prepared under 200℃ (La2oo) has the best slow-release effect. After leaching 5 times, the slow-release ratio of the 1-3 is 68.94%. And the 1-3 still has 36%of the urea can be released.N-doping porous carbon samples were prepared with larch wood hydrochar as substrate, KOH as activating agent, and melamine as nitrogen source. The result showed that N-doping porous carbon samples are amorphous structure, and they have some surface oxygen-contained functional groups, including hydroxyl, carbonyl and carboxyl, and nitrogen-contained functionalities, including pyridinic N(N-6) and pyrrolic/pyridonic N(N-5). The electrochemical test showed that the specific capacitance of porous carbon calculated by constant current charge-discharge is in turn:PC26o>PC24o ( ∽PC22o)>PC2oo. The specific capacitance of PC260 remain can reach 205F·g-1 and the specific capacitance of PC200 also can reach 143.4F·g-1 at the current density of 5.0 A·g-1. It’s worth mentioning that PC200 has the best electrochemical stability in the current density range of 0.1-10.0 A·g-1 and charge-discharge curves all have a good symmetry isosceles triangle shape.Poplar wood hydrochar with abundant oxygen-containd functional groups were prepared from poplar wood via hydrothermal carbonization. Its properties are influenced by hydrothermal carbonization temperature. The surface morphology, crystal form and surface oxygen-containd groups all transferes when hydrothermal carbonization temperature is higher than 240 ℃. N2 adsorption-desorption test showed that the prepared activated carbon that activated 60 minites at 900 ℃ with poplar wood hydrochar as substrate, CO2 as activated gas under N2 atmosphere has the highest BET specific surface area (2030 m2/g), mesoporous specific surface area(1066.77 m2/g) and mesoporous ratio(52.53%).