Why Tetrabutylphosphonium Hydroxide–Water Mixtures Can Dissolve Cellulose at Extremely High Water Mass Fractions

 In past research work, mixtures of the ionic liquid tetrabutylphosphonium hydroxide (TBPH) and water have shown a unique ability to dissolve a high percentage of cellulose at near-room temperatures.¹ This mixture only showed the high dissolution rate of cellulose for high mole fractions of water, well above the allowed range for other ionic liquids such as the imidazolium series.¹ This makes TBPH a potential solvent of interest to study to for the biofuel extraction process.

In this work we determine the thermodynamic properties of the ionic liquid TBPH in water. The density of the mixtures, over whole range of water percentages, were calculated from the simulation data. The reason for the high cellulose dissolution rate is examined, from the simulations visualized data and the radial distribution functions (RDFs). It appears that the physical location and structure of the water may highly influence the ability of this mixture to dissolve cellulose.

By calculating other thermodynamic properties (heat capacities, excess molar volumes, etc.) from the water/TBPH mixture, as well as including cellulose, we can better compare the performance of TBPH to other cellulose-dissolving ionic liquids.

¹ Mitsuru Abe, Yukinobu Fukaya and Hiroyuki Ohno, 2011, Fast and facile dissolution of cellulose with tetrabutylphosphonium hydroxide containing 40 wt% water