Бурение грунтовых зондов, установка энергетических колодцев

Ionic liquids with built-in acid function is an emerging class of bio­mass processing systems. These Bronsted acidic ionic liquids can behave as the solvent as well as the catalyst; additionally, no neu­tralization and separation of the acid catalyst is required, and there is no waste in acid, as the acid is in the solvent itself. Furthermore, a higher concentration of -SO3H active sites is expected to acceler­ate the reaction and lower the operating temperature, thus saving energy. The first use of this class of Bronsted acidic ionic liquids

was reported by Amarasekara and Owereh in 2009 [67]. In this work they reported that cellulose rapidly dissolves in Bronsted acidic ionic liquids 1-(1-propylsulfonic)-3-methylimidazolium chloride and 1-(1-butylsulfonic)-3-methylimidazolium chloride up to 20g/100g ionic liquid by gentle mixing at room temperature. Optical microscope images (x 400) of dissolution of Sigmacell® cel­lulose (DP ~ 450) is shown in Figure 7.10 [67].

Hydrolysis of cellulose could be carried out in four cellulose-ionic liquid (1a, b, 2, and 3) solutions by the addition of 2.0 equivalents of water per glucose unit of cellulose and heating the solution at 70°C, and at atmospheric pressure with or without pre-heating to give glucose along with other reducing sugars. Average % yields of TRS and glucose produced in a series of cellulose hydrolysis experi­ments using Bronsted acidic ionic liquids are shown in Table 7.2. The hydrolysis of Sigmacell® cellulose (DP ~ 450) in l-(l-propylsulfonic)- 3-methylimidazolium chloride produced the highest total reducing sugar (62%) and glucose (14%) yields, and was attained with 1 hr of preheating at 70°C and 30 min heating at 70°C after adding water.

Later, Liu et al. also reported the use of Bronsted acidic ionic liq­uids for catalysis of cellulose depolymerization under mild condi­tions [68]. However, this approach is somewhat different from the earlier group where Liu et al. first dissolved cellulose in 1-”butyl — 3-methylimidazolium chloride (BMIMCl) to make a 5% solution, and then Bronsted acidic ionic liquid and a controlled amount of water was added to hydrolyze cellulose. Bronsted acidic ionic liq­uids used (IL1 to IL6) as catalysts in the study of Liu et al. are shown in Figure 7.11.

Liu et al. found that all of the Bronsted acidic ionic liquids stud­ied are effective in hydrolysis of cellulose, with the maximum total reducing sugar (TRS) yields over 83% at 100°C. Acidic ionic liq­uids with analogous structures showed similar catalytic activities. Triethyl-(3-sulfo-propyl)-ammonium hydrogen sulfate was the optimum ionic liquid for cellulose hydrolysis. Furthermore, they found that water in BMIMCl had a negative effect on cellulose hydrolysis. Therefore, controlling the water content to a compara­tively low level was quite necessary when BMIMCl was used as the solvent medium under these conditions.

Interestingly, acid group functionalized acidic ionic liquids can be used as catalysts in aqueous media at well under moderately high temperature-pressure conditions. Amarasekara and Wiredu have studied the catalytic activities of dilute aqueous solutions of 1-(1-propylsulfonic)-3-methylimidazolium chloride for the hydro­lysis of pure cellulose by comparison with p-toluenesulfonic acid and sulfuric acid [69]. In this study dilute aqueous solutions of 1-(1-propylsulfonic)-3-methylimidazolium chloride and p-tolu — enesulfonic acid are shown to be better catalysts than aqueous sulfuric acid of the same H+ ion concentration for the degrada­tion of cellulose at moderately high temperatures and pressures.

For example, Sigmacell cellulose (DP ~ 450) in aqueous solutions of 1-(1-propylsulfonic)-3-methylimidazolium chloride, p-toluene — sulfonic acid, and sulfuric acid of the same acid strength (0.0321 mol H+ ion/L) produced total reducing sugar (TRS) yields of 28.5, 32.6, and 22.0%, respectively, after heating at 170°C for 3.0 hr. In the same set of experiments 22.2, 21.0, and 16.2% glucose yields were attained in 1-(1-propylsulfonic)-3-methylimidazolium chloride, p-toluenesulfonic acid, and sulfuric acid mediums, respectively [69]. The variations of TRS and glucose yields with temperature during the hydrolysis of cellulose in aqueous 1-(1-propylsulfonic)- 3-methylimidazolium chloride, p-toluenesulfonic acid, and sulfuric acid mediums are shown in Figures 7.12 and 7.13, respectively.

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