An improved method for the hydrolysis of hardwood carbohydrates to monomers

The range of xylan content reported for sugar maple (Acer saccharum) is wider than for most hardwoods. Credible values have been reported that range from less than 16 wt% to more than 19 wt% based on extractive-free wood. Carbohydrate composition of biomass is normally determined by a two stage H₂SO₄ hydrolysis followed by quantification of the sugar monomers. Acetic and uronic acids are also quantified for xylan-rich materials. In this research, the H₂SO₄ hydrolysis conditions were modified and an average xylan content of 18.7% was obtained for sugar maple with a standard deviation (SD) of 0.41% for eight analyses. Minor refinements were made and an average of 18.6% (SD = 0.29%) was obtained for another eight analyses. On this occasion the acetyl to xylose mole ratio was 0.71 with a standard deviation of only 0.008. Proton NMR was utilized in quantifying sugar monomers and acetic acid. The modified hydrolysis procedure gave all the expected results for Betula papyrifera, a species without much controversy regarding its carbohydrate composition. A high percentage of glucan plus xylan was also obtained for an experimentally grown poplar with a low lignin content of 17.7%. The summative analyses varied from 99.7% to 101.5% for the three species.