Conversion of Cellulose into 5-Hydroxymethylfurfural in a Biphasic System Catalyzed by Aluminum Sulfate and Byproduct Characterization

Abstract

The production of 5-hydroxymethylfurfural (HMF) from cellulose is a crucial step in the production of high-value chemicals and fuels from renewable cellulosic biomass. In this study, the influences of the H2O/organic solvent ratio, the type of organic solvents, the addition of NaCl, and the type and concentration of catalysts on the catalytic conversion of cellulose into HMF in biphasic systems were comprehensively studied, and the highest HMF yield of 45.7% was obtained from cellulose in the H2O–tetrahydrofuran (THF) biphasic system with Al2(SO4)3 as the catalyst. Further investigation reveals that the excellent performance of the H2O–THF–Al2(SO4)3 reaction system was ascribed to the high V org/V aque (60/1), high C­[Al2(SO4)3]aque (0.38 g/mL), and low C­[Al2(SO4)3]org (10–4 g/mL) of the reaction system. Moreover, the byproduct formed during the conversion of cellulose in the H2O–THF–Al2(SO4)3 reaction system was characterized by liquid chromatography–mass spectrometry (LC–MS) and LC–MS2 to detect considerable initial polymers. One plausible mechanism of glucose conversion in the H2O–THF biphasic system was proposed based on the detected compounds.

One-Pot Conversion of Cellulose into 2,5-Hexanedione in H2O-Tetrahydrofuran Co-Solvents

“…Figure b shows the reaction temperature (170–200 °C) and time (30–120 min) on the yield of HXD from cellulose. At the low temperature of 170 °C, the yield of HXD was always below 25%, which was ascribed to the fact that the temperature of 170 °C was insufficient for Al 2 (SO 4 ) 3 to catalyze the hydrolysis of cellulose . With the increase of the reaction temperature to 180 °C, the peak yield of HXD significantly increased to 65.0%, which clearly confirmed that the cellulose-to-HXD process is favored at elevated temperature.…”

“…First, we screened the acidic catalyst for conversion of cellulose into HXD, within Pd/C as a hydrogenation catalyst (Table , entry 1–7). As shown, when no acidic catalyst was added, the yield of HXD was only 10.3%, which was ascribed to the fact that the hydrolysis of cellulose could not proceed without an acidic catalyst . In contrast, the addition of the acidic catalysts into the reaction system greatly increased the yields of HXD.…”

“…Inspired by the high yield of HXD from HMF shown above and the previous research advance on the conversion of cellulose into HMF in H 2 O−THF co-solvents, 37 we further studied the one-pot conversion of cellulose into HXD in the H 2 O−THF cosolvents, catalyzed by homogeneous acidic catalysts (Al 2 (SO 4 ) 3 First, we screened the acidic catalyst for conversion of cellulose into HXD, within Pd/C as a hydrogenation catalyst (Table 3, entry 1−7). As shown, when no acidic catalyst was added, the yield of HXD was only 10.3%, which was ascribed to the fact that the hydrolysis of cellulose could not proceed without an acidic catalyst.…”

“…33 Previously, we reported that the Al 2 (SO 4 ) 3 -catalyzed conversion of cellulose in the H 2 O−THF co-solvents could produce HMF with yield of 45.7%. 37 On the other hand, the conversion of the biomass-derived furanics into HXD is also widely studied. The conversion of DMF into HXD could be easily achieved with yield over 90% catalyzed by acids.…”

“…10 They also proposed that NaCl could catalyze the conversion of cellulose into CMF, and the NaCl-treated Pd/C could selectively catalyze the hydrogenolysis of CMF into DMF. Given that the satisfactory yield of HMF could be obtained from cellulose in H 2 O−THF co-solvents, 37 we proposed that direct conversion of cellulose in the H 2 O−THF co-solvents in the presence of homogeneous acidic catalysts and noble metal may provide satisfactory yield of HXD. Herein, we designed one H 2 O−THF reaction system for one-pot conversion of cellulose into HXD, within Al 2 (SO 4 ) 3 and metal Pd/C as catalysts, and high HXD yield of 80.3% was obtained.…”