Abstract
2,5-diketopiperazine (DKP) was used as a N-containing model compound to investigate the formation pathway of NOx precursors (HCN, NH3, and HNCO) during biomass pyrolysis. The experiment was carried out using a tube furnace coupled with a Fourier Transform Infrared Spectrometer in an argon atmosphere. The results showed that NH3, HCN, and HNCO were the major N-containing species formed during DKP fast pyrolysis. The largest yield was HCN, followed by NH3 and lastly HNCO. When the pyrolysis temperature was increased, the yield of NH3 increased slowly, but the yield of HCN decreased slightly at 800~950 °C and the change accelerate rapidly above 950 °C. Then NH3 became the main product above 1020 °C. The temperature influence was negligible on the selectivity between HCN and NH3 from pyrolysis of DKP. H radicals played an important role in competitive reactions. It was also noted that the presence of Na+, K+, Ca2+, and Mg2+ exhibited a catalytic effect on nitrogen conversion during the DKP fast pyrolysis process. K+ and Na+ were beneficial to the yield of NH3, but not to the yield of HCN. Ca2+ and Mg2+ could promote the formation of HCN, but prevent the formation of NH3.
Highlights
The combustion of biomass usually produces harmful nitrogen oxides due to the high nitrogen content of the biomass, which threatens the environment
Many amino acids have been selected as model compounds, since protein is one of the major nitrogen-containing materials in biomass, and a large group of organic molecules is formed by amino acid condensation water reaction
Our results showed that the NH3, HCN and HNCO were the primary nitrogenous gases released during DKP pyrolysis, the yield of NH3 was the largest, followed by those of HCN and HNCO
Summary
The combustion of biomass usually produces harmful nitrogen oxides due to the high nitrogen content of the biomass, which threatens the environment. Due to the complex composition and diverse form of the molecules containing nitrogen in biomass, it is difficult to confirm migration mechanisms of the fuel nitrogen by direct pyrolysis of the biomass [6]. Hansson et al [9] investigated the gas release from a fast pyrolysis of the DKP in fluidized bed reactor and demonstrated that the primary pyrolysis gases containing nitrogen were HCN, NH3 , and HNCO. The distribution of nitrogen-containing gases released from DKP pyrolysis was almost the opposite under the two different experiment conditions. It is difficult to confirm the mechanism of DKP pyrolysis, because temperature field difference in the DKP particles results in pyrolysis products that influence each other. This study intends to confirm the migration mechanism of the formation of NOx precursors during rapid pyrolysis of DKP. K+ , Na+ , Ca2+ , and Mg2+ effected the NOx precursors release during DKP pyrolysis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
