Tuning The Acidity Of Task-specific Ionic Liquids For High-value Utilization Of Biomass Resources

Faced with energy exhausting and severe environmental problems,high value utilization of renewable biomass resources such as terpentine,cellulose and hemicellulose is attracted increasingly attention.However,the traditional technologies often employ inorganic acid catalysts and suffer from many problems such as low efficiency,waste gas,waste water,waste residues,and serious environmental pollution.Therefore,there is an urgent need to develop highly efficient and novel catalysts for high value utilization of biomass resources.As a representative of Green Chem,ionic liquids own many unique characteristics,and show a great potential for the high-value utilization of biomass.Herein,the present work aims at the design and synthesis of various ionic liquids catalysts with high activities by turning the acidity of ionic liquids,and these ionic liquids are thus used to replace traditional acid catalysts for the green synthesis of terpene esters and efficient hydrolysis of hemicellulose.Therefore,several important results have been obtained in two research sections and summarized as follows:The fist part of the thesis concerns the design of sulfonic functionalized ionic liquids(SFILs).Six SFILs possessing different acidities were synthesized and applied to the synthesis of terpene esters.The effect of acidity of SFILs on their performance was investigated systematically.It is found that tuning the acidity of SFILs to an appropriate value(pH = 1~2)results in not only high conversion of terpenols but also superior selectivity of terpene esters.After reaction,[Ps2TMEDA][BF4]2 can be easily separated from products by filtration under room temperature,and can be recycled for five times without significant loss of activity,thus showing good reusability.Furthermore,the kinetics for SFILs in the esterification of terpenol were determined in detail as the basis for future process design.The second part of the thesis concerns choline-based ionic liquids.Three choline-based ionic liquids with super acidities were designed,prepared,and applied to the hydrolysis of hemicellulose.It is shown that the catalytic performance of choline-based ionic liquids depends on its acidity.The ionic liquids afford the higher acidity and have the better catalytic activity.Ionic liquid [N1112-OSO3H][CF3SO3]shows the best catalytic performance with furfural yield of 82% in the hydrolysis of hemicellulose.The optimal conditions are: temperature of 120 °C,catalyst loading of0.1 g and 1,4-dioxane solvent.[N1112-OSO3H][CF3SO3] can also catalyze the dehydration of xylose to obtain both the conversion of xylose and the yield of furfural more than 95%.It can be recovered easily and used repetitively at least five times with no obvious losses of activity and quantity.