Characteristics of bio-oil and biochar from cotton stalk pyrolysis: Effects of torrefaction temperature and duration in an ammonia environment

In this study, nitrogen-containing chemicals and nitrogen-rich biochar were prepared using ammonia (NH3) torrefaction pretreatment technology. The effects of temperature and duration of torrefaction on the characteristics of torrefaction and pyrolysis products were evaluated. The results indicated that when the torrefaction temperature was increased to 290 degrees C, the nitrogen content increased significantly from 0.98% to 6.85%. XPS analysis showed that the raw biomass mainly contained amide-N and pyrrole-N. As the torrefaction temperature and duration increased, quaternary-N formation was promoted, while amide-N, pyrrole-N, and pyridine-N were consumed. Potential nitrogen doping and transformation pathways during the ammonia torrefaction process were proposed. GC-MS analysis showed that ammonia torrefaction promoted the formation of pyridines, while reducing the content of oxygen-containing species. In addition, torrefaction duration had positive effects on the yield of nitrogen-containing chemicals.

Automated summary

This study focused on preparing nitrogen-containing chemicals and nitrogen-rich biochar using ammonia torrefaction pretreatment technology, and evaluated the effects of temperature and duration on the characteristics of the products. It was found that higher torrefaction temperature led to increased nitrogen content and promoted the formation of quaternary-N while reducing other nitrogen species. Ammonia torrefaction was also found to promote pyridine formation and decrease oxygen-containing species, with torrefaction duration positively impacting the yield of nitrogen-containing chemicals.