Synergy of boric acid and added salts in the catalytic dehydration of hexoses to 5-hydroxymethylfurfural in water

Abstract

In combination with various salts boric acid, B(OH) 3 , was shown to be an efficient, weak Lewis acid catalyst in the aqueous dehydration of fructose to 5-hydroxymethylfurfural (HMF) due to strong complexation between the boron atom and the hexoses. In the dehydration of a highly concentrated aqueous fructose solution (30 wt%), a HMF yield of 60% was achieved at 92% fructose conversion and a HMF selectivity of 65% with 100 g L -1 B(OH) 3 and 50 g L -1 sodium chloride in the aqueous phase and methyl-isobutylketone (MIBK) as extracting solvent. Furthermore, the dehydration of glucose resulted in a yield of 14% HMF at 41% glucose conversion after 5 h at similar conditions. These results are highly competitive with currently reported aqueous HMF dehydration systems. In combination with the non-corrosive and non-toxic nature of the boric acid, compared to other well known homogeneous catalysts applicable for the dehydration process (e.g., H 2 SO 4 and HCl), clearly, the boric acid-salt mixture is a very attractive catalyst system.

A Simple One‐Pot Dehydration Process to Convert N‐acetyl‐D‐glucosamine into a Nitrogen‐Containing Compound, 3‐acetamido‐5‐acetylfuran

“…Using NaCl and B(OH)3, fructose has been shown to produce 60% yield 5-HMF and glucose produced 14% yield 5-HMF. [20] Therefore, at the present time, we assume that the reaction mechanism is similar to those reported for conventional carbohydrates.…”

“…After studying the impurity levels in the NAG from each supplier using ICP-MS, boron (B) and chloride (Cl) concentrations stood out as being significantly higher in the NAG from TRC, Table 2. [15,17,20] Therefore, different amounts of NaCl were added to reaction mixtures to test the effect of Cl -concentration on 3A5AF production using NAG from AK Scientific and Alfa Aesar. Figure 4 shows that NaCl at 30-50 mol% with respect to NAG produced the highest % yield of 3A5AF.…”

“…[19,20] Yields of up to 42% from glucose and as much as 66% from sucrose have been reported. Figure 5 shows the effect of adding B(OH)3 at a 2:1 B(OH)3:NAG mol ratio on 3A5AF production in the presence and absence of NaCl (30 mol% with respect to NAG), and in the presence and absence of ammonia (24.4 mol% of NAG).…”

Sodium Ion Interactions with Aqueous Glucose: Insights from Quantum Mechanics, Molecular Dynamics, and Experiment

“…This temperature is representative of the moderate temperatures employed in relevant experimental work. 15,16 Relative energies at 298 K are reported in the Supporting Information. The lowest-energy conformations of both α-and β-glucose have the hydroxymethyl group in the gg conformation.…”

Formation of a renewable amide, 3-acetamido-5-acetylfuran, via direct conversion of N-acetyl-d-glucosamine

“…7 Chloride ion concentration has also been shown to increase conversions in aqueous transformations of cellulose and hexoses. 8,9 Alkyl chain length on the cation was found to slightly affect yield. In the case of entries 3 and 6, it was found that [BMim]Br was more able to facilitate the dehydration than the ethyl equivalent.…”