Formation of nanocarbon spheres by thermal treatment of woody char from fast pyrolysis process

Abstract

Influences of thermal treatment conditions of temperature, reaction cycle and time, and purge gas type on nanocarbon formation over bio-chars from fast pyrolysis and effects of thermal reaction cycle and purge gas type on bio-char surface functional groups were investigated by temperature-programmed desorption (TPD) and temperature programmed reduction methods. Nanospheres occurred on bio-chars under the activation temperature of 700ºC; more nanospheres occurred when temperature increased to 900ºC. Further increase of temperature to 1100ºC yielded bio-char surfaces covered with a layer of nanospheres between 20 and 50 nm. More carbon nanospheres formed by increasing thermal cycles and reaction time. Scanning electron microscope images of char surfaces showed there were fewer or no nanoparticles produced using H₂ as the purge gas and they were porous. TPD results indicated that H₂, H₂O, CH₄, CO, and CO₂ in gas phases evolved from chars heated to 1000ºC during the first heating cycle. H₂ and CH₄ peaked at 750 and 651ºC, respectively. Both H₂O and CO had two peaks and CO₂ had a broad peak. Only trace amounts of H₂ and CO were detected in the second cycle. There was no detection for CH₄, H₂O, and CO₂ after the second cycle.

Citation

Yan, Qiangu; Toghiani, Hossein; Cai, Zhiyong; Zhang, Jilei. 2014. Formation of nanocarbon spheres by thermal treatment of woody char from fast pyrolysis process. Wood and Fiber Science. 46(4): 437-450.