Conversion of fructose into 5-HMF: a study on the behaviour of heterogeneous cerium-based catalysts and their stability in aqueous media under mild conditions

Abstract

In this paper, we present the results of a study on 5-HMF production from fructose by means of heterogeneous catalysts in aqueous media. Mild conditions were used, setting the temperature between 393 K and 443 K. Cerium(IV) phosphates, different from other metal(IV)-phosphates, such as titanium and zirconium, have been characterized only recently. Ce-phosphates are quite complex structures as they show several arrangements. They undergo leaching of the phosphate group as phosphoric acid with consequent slow de-activation of the catalysts. The leaching rate depends on the nature and on the temperature of the calcination of the original phosphates. This opened the question whether the conversion was driven by the heterogeneous catalysts or by the soluble phosphoric acid. A specific test has demonstrated that the solid catalysts are responsible for the conversion of fructose into 5-HMF, more than the liquid phase. We have also demonstrated that the leached phosphate is substituted by fructose on the solid catalyst. A best yield of 52% with selectivity of 93% in batch and 24% in a flow reactor at 443 K (single pass) with a selectivity also >95% were obtained.

Organic Carbonates: Efficient Extraction Solvents for the Synthesis of HMF in Aqueous Media with Cerium Phosphates as Catalysts

“…As we have shown elsewhere, [10] the deactivation of the catalyst is mainly caused by the adsorption of the organic polyol on the surface of the catalyst and, to al ower extent, to the loss of phosphate. With the use of the biphasic system, the de-activation of the catalyst is much lower than in water.P hosphoric acidi sn ot formed extensively in solution;o therwisei t would have affected the OC significantly and converted it back to alcohol andC O 2 .H owever,i ft he catalyst is calcined at 823 K after the fifth cyclei ti sa ble to produce 5-HMF with the same yield and selectivity as in the first run.…”

“…[10] Here we summarize the synthetic aspects briefly for the reader's convenience. [10] Here we summarize the synthetic aspects briefly for the reader's convenience.…”

“…[10] from Ce(NO 3 ) 6 (NH 4 ) 2 and K 3 PO 4 in stoichiometric amount (P/Ce = 3m olar www.chemsuschem.org ratio). [10] from Ce(NO 3 ) 6 (NH 4 ) 2 and K 3 PO 4 in stoichiometric amount (P/Ce = 3m olar www.chemsuschem.org ratio).…”

“…[10] from CeO 2 and H 3 PO 4 (PO 4 /Ce = 2.4 molar ratio). [10] from CeO 2 and H 3 PO 4 (PO 4 /Ce = 2.4 molar ratio).…”

An Easy Scalable Approach to HMF Employing DMC as Reaction Media: Reaction Optimization and Comparative Environmental Assessment

“…Recently organic carbonates have been used as co‐solvents for the synthesis of HMF in aqueous media employing cerium phosphates as catalysts . This process is very appealing although it still requires high temperature (150 °C), an opportune preparation of the catalyst and, under the best reaction conditions, the HMF yield was 43–52% with 93% selectivity.…”