Thermal transformation of micro-crystalline cellulose in phosphoric acid

Use of crude oil derivatives such as diesel and gasoline is becoming unsuitable due to their detriment to environment and to the increasing worldwide energy demand which is driving crude oil reservoirs towards exhaustion. Replacement of diesel and gasoline with biofuels (i.e. biodiesel and bioethanol, respectively) is very desirable. In fact, biofuels are not only environmentally sustainable, but also potentially inexhaustible due to the large amounts of waste biomasses from which they can be retrieved. In the present study, a model compound (micro-crystalline cellulose) was dissolved in phosphoric acid and converted at 80 °C to glucose, thereby providing the possible substrate for fermentation to bioethanol. Results revealed that after 1 h heating, the reaction had the largest glucose yield as compared to similar studies done by using other acid catalysts. In addition, the temperature applied here was from 40 to 60 °C lower than those already reported in literature for acid-driven cellulose degradations. Phosphoric acid allowed both glucose and levulinic acid achievement. The latter is usually used to synthesize fuel additives, catalysts, solvents and herbicides, thereby enhancing the added value of the conversion of cellulose to glucose in phosphoric acid. Finally, ¹H T₁ NMR relaxometry showed its suitability to monitor cellulose degradation. The advantages of relaxomety are its quickness since only few minutes are needed to obtain relaxograms, and the possibility to use raw mixtures without the needing of sample preparation.