Experimental and mechanistic modeling of fast pyrolysis of neat glucose-based carbohydrates. 2. Validation and evaluation of the mechanistic model

A computational framework based on continuous distribution kinetics was constructed to solve the mechanistic model that was developed for fast pyrolysis of glucose-based carbohydrates in the first part of this study [ Zhou et al. Ind. Eng. Chem. Res. 2014, 53. DOI 10.1021/ie502259w ]. Comparing modeling results with experimental yields from fast pyrolysis over a wide range of reaction conditions validates the model. Agreement between model yields of final pyrolysis products with experimental data of fast pyrolysis of cellulose at temperatures ranging from 400 to 600 °C and maltohexaose, cellobiose, and glucose at 500 °C showed that the mechanistic model was robust and extendable. In comparison to our previous model [ Vinu, R.; Broadbelt, L. J. Energy Environ. Sci. 2012, 5, 9808-9826 ], the mechanistic model presented in this work incorporating new findings from experiments and theoretical calculations showed enhanced performance in capturing experimental yields of major products such as levoglucosan-pyranose, char, H₂O, CO ₂, CO, and especially glycolaldehyde and 5-hydroxymethylfurfural. The model was also able to well match the yields of pyrolysis products that our previous model did not include, such as levoglucosan-furanose, methyl glyoxal, and minor products with yields of less than 1 wt % like levoglucosenone, acetone, dihydroxyacetone, and propenal. The mechanistic model showed its versatility in providing insights that were difficult to obtain from experiments, including a time scale of 4-5 s for complete thermoconversion of cellulose at 500 °C. Analysis of the contributions of competing reaction pathways showed that decomposition of cellulosic chains played a more important role in the formation of levoglucosan and glycolaldehyde than in that of other pyrolysis products.