FIGURE 4.2 Formation of levulinic acid from 5-hydroxymethylfurfural.


y-Valerolactone y-Valerolactone

Levulinic acid Formic acid Polyol +


Levulinic acid Formic acid Polyol +

40 30 20 10

FIGURE 4.3 Catalytic conversion of sucrose.

catalyst (RuCl3, 0.006 mol/l; tris(3-sulfonatophenyl)phosphane trisodium salt (TPPTS), 0.02 mol/l; Nal, 0.008 mol/l), the formation of levulinic acid, formic acid, Y-valerolactone, and a polyol was observed by high-pressure nuclear magnetic resonance (NMR) (Figure 4.3). We have confirmed that the formation of levulinic acid is due to sulfuric acid-catalyzed dehydration of sucrose. It should be noted that numerous homogeneous and heterogeneous catalytic systems have been reported for the hydrogenation of levulinic acid to Y-valerolactone.8 We have also observed that levulinic acid could be converted to Y-valerolactone completely under similar conditions using the same catalyst. The final product Y-valerolactone can be readily extracted from the aqueous phase with ethyl acetate.

Only a few catalytic systems are known for the reduction of Y-valerolactone.9 Its hydrogenation to 2-methyltetrahydrofuran (2-Me-THF) was achieved using a ruthenium catalyst that has previously been used to hydrogenate several other lac-tones to their corresponding diols.10 Complete reduction was observed when y-valerolactone (12.6 mmol) was treated with 70 bar H2 at 200°C in the presence of Ruacetylacetonato(acac)3 (0.03 mmol), PBu3 (1.0 mmol) as catalyst, and NH4PF6 (0.53 mmol) as cocatalyst for 46 h. It is probable that 1,4-pentanediol is an intermediate, as it has been shown to give 2-Me-THF via its dehydration in acidic media at elevated temperatures. It should be noted that the conversion of 2-Me-THF to hydrocarbons was achieved when it (2.32 mmol) was dissolved in CF3SO3H (9.30 mmol) and reacted with hydrogen (70 bar) in the presence of Cl2Pt(2,2'-bipyrimi-dine)11 (0.023 mmol) at 150°C. In situ high-pressure nuclear magnetic resonance (NMR) experiments have shown that the completely protonated 2-methyltetrahydro-furan (Figure 4.4) was converted to oxygen-containing carbocations and alkanes in 15 h. Additional heating of the reaction mixture for 5 h resulted in the formation of a biphasic system. NMR, gas chromatography (GC), and GC-mass spectrometry (GC-MS) measurements have shown that the colorless upper phase consists of a mixture of hydrocarbons, mainly butane, isobutane, pentane, and isopentane.

We have shown that carbohydrates can be converted to different C5-oxygenates (including Y-valerolactone and 2-methyltetrahydrofuran) and a mixture of hydrocar-





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