A new route to improved glucose yields in cellulose hydrolysis

An unusual inverse temperature-dependent pathway was discovered for cellulose decrystallization in trifluoroacetic acid (TFA). Cellulose was completely decrystallized by TFA at 0 °C in less than 2 hours, a result not achieved in 48 hours at 25°C in the same medium. The majority of TFA used in cellulose decrystallization was recycled via a vacuum process. A small remaining amount of TFA was diluted with water to make a 0.5% TFA solution and used as a catalyst for hydrolysis. After one minute at 185 °C under batch conditions, the glucose yield reached 63.5% without production of levulinic acid. In comparison, only 15.0% glucose yield was obtained in the hydrolysis of untreated cellulose by 0.5% H2SO4 under the same conditions. Further improvement of glucose yield is possible by optimizing reaction conditions. Alternatively, the remaining TFA can be completely removed by water while keeping the regenerated cellulose in a highly amorphous state. This regenerated cellulose is much more reactive than untreated cellulose in hydrolysis reactions. The lower temperatures and shorter reaction times with this activated cellulose makes it possible to reduce operating costs and decrease byproduct yields such as HMF and levulinic acid.