Quantitative Analysis Of Typical Anhydro-sugars Obtained From Pyrolysis Of Cellulose At Low Temperature Based On Benzoylation

Biomass is a renewable energy and the use of it is of great significance for China’s energy security and economic development.Biomass pyrolysis is a promising technology for liquid products —bio-oil which is expected to replace fossil fuels.However,large-scale biomass pyrolysis processes have been hindered by the poor fuel properties of bio-oil.By controlling the distribution of pyrolysis products,it can effectively improve the quality of bio-oil,but this requires a sound understanding of the mechanism of biomass pyrolysis.Cellulose is the most abundant and simple component of biomass.Its pyrolysis characteristics is of great significance to reveal the whole pyrolysis mechanism of biomass.Anhydro-sugars are the most important components in the products of cellulose pyrolysis.The pathways of their formation are important to reveal the mechanism of cellulose and biomass pyrolysis.Traditional quantification of these compounds is accomplished by GC-MS or HPLC which can’t obtain good performance in the separation and quantification of these compounds.In this paper,the benzoylation derivation method is adapted to determination of the four typical anhydro-sugars obtained from the pyrolysis of cellulose by HPLC-UV for the first time.The experiment studies showed that all the anhydro-sugars were obtained good separations,particularly two isomers-cellobiosan and maltosan were completely separated for the first time by HPLC.The detection limits of the method were 0.009~0.45μg/ml and the recovery of the four anhydrous-sugars were 99.2%~104.9%.Three typical compounds were used for the interference study and the results showed that these compounds have no effect on the quantification of the four anhydro-sugars.All the experiment results show that the benzoylation method is sensitive,accurate and suitable for microanalysis of the anhydrosugars in pyrolysis products of cellulose.A derivation method based on bezoylation was appleied to quantitative analysis of four anhydro-sugars obtained from pyrolysis of cellulose on a fixed bed reactor.The experimental results show that four anhydro-sugars may be produced via random chain cleavage during cellulose pyrolysis rather than secondary polymerization of levoglucosan.In the intial stage(150℃~270℃),the increase of temperature is beneficial to the cleavage of glycosidic bonds,and promote the formation of anhydro-sugars.The anhydro-sugars would stay in char due to the low temperature.However too high temperature is not conducive to the presence of anhydro-sugars in char.The reduction of their yields may result from other competition reactions or producing other compounds(such as decomposition)at higher temerature.The higher DPs anhydro-sugars have less thermal stability and reach the highest yield at lower temperature.The anhydro-sugars are more likely to be released into the vapor phase the tar via evaporation(levoglucosan)or ejection mechanism(cellobisan)as a component of tar above 270℃.In this experiment,maltosan was obtained from the products of cellulose pyrolysis at 150℃ and the yield of it was higher than that of levoglucosan.In char and tar products,the ratio of cellobiosan and maltosan was always maintained at about 2,which means that maltosan may not be only from secondary polymerization of levoglucosan,but also be derived from the isomerization of cellobiosan.