Preparation Of Acid-functionalized Silica-gel And The Application Of Catalytic Hydrolysis Of Cellulose In [BMIM]Cl

Lignocellulose is the most abundant biomass on the earth, and the conversion oflignocellulose into biofuels is of great significance to cope with the fossil fuels crisisand to improve the quality of environment. The hydrolysis of lignocellulose intosugars is the key step to produce biofuels. Currently, the solid acid-catalyzedhydrolysis process has attracted much more attention for the easy separation ofcatalyst. Meanwhile, the combination of ionic liquid and solid acid makes thehydrolysis process more competitive, which can produce higher yield of sugars undermild conditions. The process is effective to improve the defects of high loading ofcatalyst and harsh reaction conditionsIn the study, two kinds of acidic silica materials (silica-IL-1, silca-IL-2) wereprepared by immobilization of acidic ionic liquids(IL-1, IL-2) on the silica gelaccording to the methods of sol-gel and chemical bonding, respectively. Meanwhile,another kind of acid-functionalized silica with different acidities was preparedaccording to a simple two-step routine. The function group-SH grafted on the surfaceof silica was oxidized into SO3H group by H2O2. The main hydrolysis factors,involving reaction temperature, dosage of catalyst, H2O added in system as well asreaction time, were investigated in detail.When silcia-IL-1was used as acid catalyst,81%of TRS was obtained in2h at100℃once the catalyst dosage was0.10g and the H2O added was0.04ml. Whenpropyl sulfonic acid silica was applied as catalyst, with the increasing of the catalystdosage, the maximum TRS yield had a slight increase and the hydrolysis timerequired was shortened largely. In the range of0.05-0.10g, the maximum TRS yieldhad a slight variation within78%-81%. In addition, reaction temperature had greateffect on the hydrolysis rate，and80%of TRS yield was reached after reaction of30min under120℃. In general, it was found that both of the acidic silica materialswere excellent catalysts to promote the hydrolysis of cellulose in [BMIM]Cl.Through comparison testing, propyl sulfonic acid silica was verified to have themost excellent catalytic performance. A fve-level, four-factor factorial centralcomposite design (CCD) was designed by Design-Expert8.0.6under the responsesurface methodology (RSM). The optimal conditions for TRS production were asfollows: reaction temperature112℃, catalyst dosage0.05g, H2O added0.08ml, reaction time99min. Under these conditions，the average experimental value was82.86%. In addition, the hydrolysis of cellulose can be described as apseudo-frst-order homogeneous sequential reaction followed by degradation ofmonosaccharide. Experimental data were ft well according to Saeman model.