| Ethylation is one of the most versatile functionalization procedures as it provides accessto lignocellulose with soulubility and other valuable properties. In this thesis, we focus on theethylation of cotton linters and sugarcane bagasse with ethyl bromide, and we developed anaccurate and rapid headspace gas chromatography (HS-GC) method for the determination ofethoxyl contents of ethylated products.First we demonstrated a HS-GC method to measure the ethoxyl content with toluene asinternal standard. The procedure consists of reaction of ethyl cellulose with57wt%hydriodicacid in headspace sample vials by a modified Zeisel method and neutralizing the remaininghydroiodic acid with sodium hydroxide before the HS-GC performance, which can avoid thedamage of the sample injection system and column. The equilibration time of sample andmatrix additive had effect on determination. Vial equilibration time of30min was enough forthe vapor-liquid equilibrium at80℃. Cellulose was added in the reference standard toeliminate matrix effect. The reference standard curve showed a good linear relationship(R2=0.9994, n=7). Then we improved the HS-GC method by using full evaporation headspacetechnique to inject sample. The date showed that a near-complete mass transfer of samplefrom liquid to the vapor phase (headspace) was achieved within4min at90℃when30μLsample was added to a20mL headspace sample vial. The results showed that the method has agood linear relationship of standard calibration curve (R2=0.9998，n=7) and accuracy(recovery=98.9%). The two methods are simple, rapid, and precise, but we prefer the fullevaporation headspace method which can eliminate the sample matrix effect and reduce thetime for phase-equilibration.The ethylation of cotton linter with ethyl bromide using tetrafuran as solvent afteralkalization was investigated. Compare with ethyl chloride, the reactivity of ethyl bromide ishigher, we found the ethylation can be started at80℃and the reaction completed in a shortertime. The effects of parameters including alkali concentration, solid alkali, alkalization time,ethyl bromide, tetrafuran, reaction temperature, reaction time and sirring on the ethoxylcontent of products were studied. The results showed that high alkali concentration (50%w/w), proper alkaline activation time (1h) and adding solid alkali (NaOH/cellulose=10/16.2) were good for the etherification, the ethoxyl content increased with the increment in reactiontemperature, reaction time,ethyl bromide, tetrafuran and stirring, which preferred to130℃,5h,100mL,100mL and400~500rpm respectivitly. The EC product obtained under the optimumconditions has high ethoxyl content (>49%) and good solubility. Compare with commercialEC, the EC product has close relative molecular mass and narrower mass distribution.The chemical modification of sugarcane bagasse (SCB) was carried out with ethylbromide in tetrahydrofuran as dispersion solvent after alkali pretreated. Sugarcane baggasecan be etherified with ethyl bromide to obtain various ethoxyl contents products, whichwas confirmed by FT-IR and13C-NMR. The alkali concentration for treatment, ethyl bromideconcentration for reaction, reaction time and temperature were optimized in the process. Theextent of the etherification was measured by yield and ethoxyl content in product, whichincreased with an increment of alkali concentration, alkaline activation time, ethyl bromideconcentration, reaction temperature and reaction time. However, a further increment ofalkaline activation time, reaction temperature and reaction time would result in yielddecreasing. Optimum alkali concentration of66.7%, alkaline activation time of40min, ethylbromide/sugarcane bagasse ratio of6:1(v/w), reaction temperature of130℃and reactiontime of5h were determined under the experimental conditions given. The thermal stability ofethylated SCB was higher than unmodified SCB. Ethylated SCB is soluble in a wide varietyof solvents especially in the alcohol/toluene mixed solvents, and the solubility increased withethoxyl content. |
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