纤维素水解文献Depolymerization of cellulose by solid catalysts in ionic liquids

Supporting Information ? Wiley-VCH 2008

69451 Weinheim, Germany

Supporting Information

Depolymerization of cellulose by solid catalysts in ionic liquids

Roberto Rinaldi, Regina Palkovits, and Ferdi Schüth*

Max-Planck-Institut für Kohlenforschung, Department of Heterogeneous Catalysis,

Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.

Experimental Details

Materials.Microcrystalline cellulose (cotton linters, 20 μm, Aldrich) and α-cellulose (fibers, Aldrich) was dried for 24 h at 363 K prior to cellulose dissolution. 1-Butyl-3-methylimidazolium chloride (Basionic ST 70, ≥ 95 %, BASF) were purchased from Fluka and used as received. The catalytic materials Amberlyst 15DRY (Aldrich), Nafion NR50 (Aldrich) and p-toluenesulfonic acid monohydrate (≥ 98.5 %, Fluka) were used as received. Amberlyst 35 and Amberlyst 70 were stirred twice in methanol (99.9 %, Aldrich) for 15 min, and then dried at 343 K overnight. γ-Al2O3(99 %, Strem), Al2O3-SiO2 (grade 135, Aldrich), ZSM-5 (NH4-form, SM-27 ALSI-Penta, Zeolithe GmbH)and Zeolite Y (after cation-exchange to NH4+, SiO2/Al2O3 = 6.0, Degussa) were activated at 773 K for 5 h. Sulfated ZrO2 was prepared as described by Y. Sun et al. J. Phys. Chem. B109, 2567 (2005). Table S1 shows the textural properties of the catalytic materials tested.

Depolymerization of cellulose.The solution of cellulose in 1-butyl-3-methylimidazolium chloride (BMIMCl) was prepared by dissolving 5.00 g of microcrystalline cellulose, or other cellulose/wood, (31 mmol, calculated as anhydroglucose, C6H10O5) in 100.00 g of BMIMCl at 373 K using mechanical stirring at 373 K. To the cellulose/BMIMCl solution, 2.00 mL of distilled water (111 mmol) was added under mechanical stirring. The mixture was stirred for 15 min. Subsequently, 1.000 g of Amberlyst 15DRY (equivalent to 4.6 mmol of p-TSA) was added to the mixture containing cellulose. The depolymerization of cellulose was carried out at 373 K for 5 h. The aliquots (5.00 g) were taken at the reaction times indicated. Cellulose from the aliquots was precipitated by addition of water (25.00 mL).

The cellulose was separated from the aqueous solution by centrifugation. The aqueous solutions were collected and stored at 273 K for posterior DNS assay and HPLC analysis. The isolated cellulose was thoroughly washed with water, and recovered by centrifugation. Cellulose samples were dried at 363 K overnight, and reserved for gel permeation chromatographic analysis. The amount of cellulose isolated was determined by weighing.

Catalyst screening. Initially, a solution of cellulose in 1-butyl-3-methylimidazolium chloride (BMIMCl) was prepared by dissolving 5 g of α-cellulose (31 mmol, calculated as anhydroglucose, C6H10O5) in 100 g of BMIMCl at 373 K using mechanical stirring. After the complete dissolution of α-cellulose, 2 mL of distilled water (111 mmol) was added under mechanical stirring at 373 K. The mixture was stirred for 15 min, and then ca. 10 g of cellulose solution were taken and placed in a round-flask. Into this solution, ca.

0.1000 g of catalyst (Amberlyst 15DRY, Amberlyst 35, Amberlyst 70, Nafion, γ-Al2O3, Al2O3-SiO2, ZSM-5, or Zeolite Y) was added. The mixture was kept at 373 K under magnetic stirring for 1 h. Finally, 25 mL of distilled water was added to the reaction mixture. Cellulose was isolated for GPC analysis.

DNS Assay.The amount of total reducing sugars was determined by reaction with 3,5-dinitrosalicylic acid (DNS) at 373 K [ref. 17]. The color formation was monitored at 550 nm using a StellarNet Inc EPP2000 UV-Vis spectrometer. The amount of TRS was determined using a standard curve obtained with glucose.

HPLC analysis of sugars and dehydration products. The chromatographic separations were carried out using a Nucleogel OA HY (300 ×7.8 mm, 10μm) column, and an aqueous solution of sulfuric acid (5 mmol L-1) as mobile phase. The samples were analyzed in the isocratic mode at a flow rate of 0.5 mL min-1 at 353 K, using a Perkin-Elmer HPLC 200. The sugars (glucose, xylose, arabinose, and cellobiose) were analyzed using a refractive index detector. The dehydration products (levulinic acid, furfural, 5-hydroxy-methylfurfural, furan, and furan-2-carboxylic acid) were analyzed using a diode-array UV-Vis

detector at 254 nm. The identification of the components was done by comparison of retention times with authentic samples. The amounts of products were quantified using external calibration curves. Fig. S1 shows the main products and by products formed in the process of hydrolysis of cellulose. Tables S2 and S3 show the amount of sugars and dehydration products found.

Determination of the apparent degree of polymerization.Dried cellulose samples were derivatized with phenylisocyanate in DMSO, resulting in cellulose tricarbanilates, which are readily soluble in THF [ref. 14]. The analysis of gel permeation chromatography was carried out at 308 K in a Shimadzu HPLC LC10 instrument using a series of LiChrogel columns (300 6.5 mm; PS4000, 400, 40 and 1) and stabilized THF as eluent (1.0 ml min-1). The detection was made utilizing a UV-Vis detector at 236 nm. The system was calibrated with polystyrene standards. The apparent number-average and weight-average degree of polymerization, DP n and DP w, respectively, were calculated dividing the respective average molecular weight values by molar mass of the anhydroglucose tricarbanilate (519 g mol-1). Polydispersity was calculated as the ratio of DP w to DP n.Fig. 2 shows the evolution of the degree of polymerization of cellulose in a control experiment (no catalyst addition).

Table S1. Textural properties of the catalytic materials tested.

Material S A (m2 g-1)d(nm)V (cm3 g-1)

Amberlyst 15DRY36360.30

Amberlyst 35 dried40280.32

Amberlyst 70 dried a< 1--

Nafion a< 1--

γ-Al2O352012.50.78

Sulfated ZrO21108.20.24

Zeolite Y8270.70.36

SiO2-Al2O3532 4.50.75

ZSM-5380 1.20.15

a These materials showed no N

adsorptive properties at 77 K due to their extremely low surface areas.

2

Amberlyst 15DRY.

Reaction time (h)Cellobiose

(%)

Glucose

(%)

Xylose

(%)

Arabinose

(%)

5-HMF

(%)

Furfural

(%)

TRS

(%)

Cellulose

isolated

(%)

0.25000000098 0.5000.0590000099

0.7500.08700000.599

1.000.0890.07400.08600.599

1.500.100.0920.160.08600.799

2.00.060.140.170.290.0990.011 2.683

3.00.200.280.430.260.100.014 5.183

4.00.360.520.870.170.130.0268.672

5.00.630.94 1.470.190.170.05312.771

time (h)(%)(%)(%)(%)(%)(%)(%)isolated

(%) 0.250000.23000.895 0.500.060.070.210.2600 1.769

0.750.150.130.320.2900 3.365

1.00.170.220.470.250.020.01 4.970

1.50.340.390.810.200.030.018.269

2.00.490.61 1.20.160.050.0210.963

3.00.91 1.2 2.10.150.120.0716.866

4.0 1.6 2.1 3.40.080.220.1223.057

5.0 2.3 3.0 4.400.330.1628.052

Fig. S1. Main products and byproducts found in acid-catalyzed hydrolysis of cellulose.

Fig. S2.Control experiment (no addition of acid catalyst).Distribution of apparent degree of polymerization of the cellulose isolated from the α-cellulose/BMIMCl solution. Experiment conditions: α-cellulose (5 g, 31 mmol, calculated as anhydroglucose, C6H10O5) dissolved in BMIMCl, water (2 mL, 111 mmol), 373 K. The percent values between parentheses represent the amount of cellulose isolated by

precipitation.