Influence of NH3 concentration on biomass nitrogen-enriched pyrolysis

Abstract

In this study, nitrogen was used to replace oxygen through biomass N-enriched pyrolysis in a fixed-bed reactor to obtain N-containing chemicals and N-doped biochar. Influence of NH3 concentration on the formation mechanism of N-species and electrochemical performance of N-doped biochar was investigated in depth. Results showed that increasing NH3 concentration promoted bio-oil and gas generation, and increased H2, CH4 and CO yield at the diminishing of CO2. Simultaneously, bio-oil showed lower oxygen content with non-methoxy phenols and N-heterocyclics as the main components, and the maximums were 57.73% and 16.21% at 80 vol% NH3 concentration, respectively. With regard to solid N-doped biochar, nitrogen content (4.85 wt%), N-containing groups and specific surface area (369.59 m2/g) increased greatly, and excellent electrochemical property (120 F/g) was shown with NH3 concentration increasing. However, NH3 conversion efficiency decreased gradually with NH3 increasing, and 40 vol% may be the optimum NH3 concentration for biomass N-enriched pyrolysis.