Co-pyrolysis of cellulose and urea blend: Nitrogen conversion and effects of parameters on nitrogenous compounds distributions in bio-oil

This paper aimed at investigating the co-pyrolysis behavior of cellulose and urea in a fixed bed reactor under N 2 atmosphere. The effects of the proportions of urea in blend and pyrolysis temperatures on the char and the components of bio-oil were investigated. When the proportion of urea was 20 %, the peak area of anhydro sugars was 28.66 % higher than that when the proportion of urea was 0%. Furans and carbonyls were the key intermediates for the formation of nitrogenous heterocyclic compounds (NHCs) from cellulose. The NHCs in the obtained bio-oil mainly are pyrroles, pyrimidines, pyridines, imidazoles and pyrazines. Higher temperature (600℃) was unfavorable for improving the selectivity of NHCs. Co-pyrolysis of cellulose and urea can introduce abundant nitrogen and nitrogenous functional groups into char. In addition, residuals obtained at different residence times have also been characterized by element analysis and FTIR. The results showed that both the amount and the kind of functional groups in the residuals were reduced with the residence time increasing. High value NHCs and nitrogen-rich char were generated by co-pyrolysis of cellulose and urea. Finally, the possible reactions for the generation of NHCs in the bio-oil were given.