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The dissolution and recovery of cellulose from pine wood bits with two types of ionic liquids and co-solvents were explored. The results revealed that 1-ethyl-3-methylimidazolium diethylphosphonate ionic liquid/dimethylsulfoxide (mass ratio 1:0.5) could dissolve pine cellulose within 8 min at 105°C. Moreover, the degree of polymerization of the regenerated cellulose reached 244. The dissolved cellulose could be regenerated from the component solution when water was added. Then, the regenerated cellulose was characterized by X-ray powder diffraction, Fouriertransform infrared spectroscopy, and thermal gravimetric analysis measurements. The results revealed that there was no derivatization of the reaction in the process of dissolution and that dissolving the pine cellulose was a direct process. The crystalline structure of the cellulose was converted from cellulose I to cellulose II after regeneration. The regenerated cellulose was also found to have good thermal stability.

A novel polyionic liquid for esterification was synthesized by phenolic condensation. Different characterization techniques were applied, and the result showed that the catalyst had high acidity amount (4.5 mmol/g) and good thermal stability. The decomposition temperature of the polyionic liquid catalyst (PIL-S) was 240 °C, which was fitted to the product of ester. Owing to these good properties, the PIL-S exhibited excellent catalytic activity in esterification. The optimized condition was the 6 wt % catalyst amount, and the ratio of acetic acid to n-butanol was 0.8:1 at 95 °C for 3 h. In the optimized condition, the yield of ester was 97.1%. The PIL-S also has a good catalytic effect in other esterification systems. Compared with commercial resins (Amberlyst 15) and other catalysts, PIL-S showed better catalytic activity. After eight times use, the yield of ester did not decrease obviously (over 94%). The structure of PIL-S remained stable after eight times use.

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