Production of aliphatic carboxylic acids during the alkali catalysed decomposition of cellulose

The degradation of cellulosic materials under alkaline condition (sodium hydroxide) using High performance ion exclusion chromatography (HPIEC) Dionex ICS‐3000 to analyse the samples at different temperatures (at room, at 50 °C, at 90 °C), under atmosphere of N2 during 188 hours, by using acrylic acid as internal standard, resulted in complex mixture of compounds, including isosaccharinic acid.

The retention time of aliphatic organic acids measured under the conditions outlined in experiment 1.was pyruvic (6.70),gluconic (7.90), glyceric (9.10),lactic (9.70), formic (10.50), glycolic (11.20), acetic (13.80), propionic (14.30), and acrylic acid (16.20).

As the pKa of the aliphatic organic acid increases the retention times increases and it can also be seen in table 4.1 that as the number of carbon numbers in the compounds increase the retention time increases.

The identification of aliphatic acids formed during the alkali catalysed decomposition of cellulose in the experiments following at least six different acids are being produced in significant amounts and these are saccharinic acids, glycolic acid, lactic acid, formic acid and the final peak is that of the internal standard acrylic acid.

It is very clear that at room temperature the lactic acid is the most abundant decomposition product followed by glycolic acid with formic acid being present in much smaller amount. As the temperature is raised to be 50 oC, the amount of formic acid generated is significantly higher: Lactic acid glycolic acid formic acid. On a weight by weight base there is approximately the same amount of lactic acid and formic acid produced after 100 hours. In comparison, at 90 oC formic acid is now by far the most abundant of the small aliphatic acids, the amount of lactic acid has also increased significantly whilst there is a more modest rise in the amount of glycolic acid that is generated: Lactic acid, glycolic acid, formic acid. From these result sit is clear that the different fragmentation reactions, leading to the partitioning of the intermediate to the different small acids have different activation energies.