Catalytic cascade processes for obtaining 5-HMF, levulinic acid and γ-valerolactone from fructose.

MÉNDEZ, LETICIA J.; LEGUIZAMÓN APARICIO, MARÍA S.; MUSCI, JUAN J.; BARBELLI, MARÍA L.; CÁNEPA, ALICIA S.; CASELLA, MÓNICA L.; LICK, ILEANA D.

Buenos Aires

Congreso; WCCE11- 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

There is nowadays much interest in the design of cascade-type processes under mild conditions to produce chemicals and fine chemicals, avoiding intermediate purification steps. Herein, the reactions of dehydration of fructose to 5-hydroxymethylfurfural (5-HMF), rehydration of 5-HMF to levulinic acid (AL) and the subsequent hydrogenation of levulinic acid for the final obtention of -valerolactone (GVL) are presented, using an ionic liquid (IL) [C4SO3Hmim][HSO4] as catalyst/solvent for the two first steps, and a Ru/Z-A catalyst for the hydrogenation reaction.IL was obtained and characterized following previously published protocols [1]. The conversion of fructose to LA and subsequent hydrogenation to GVL was carried out avoiding the step of isolating the 5-HMF formed in the first step. For this, 3.6 g of IL and 3.6 g of fructose were placed in a 50 mL flask. The mixture was heated to 100°C in an oil bath and continuously stirred with a magnetic bar at 500 rpm. The IL fulfilled the functions of solvent and of providing acid sites. The imidazolium cation favors the solubility of the carbohydrate and the breaking of the hydrogen bonds presented by the fructose.After 1 h of reaction, a refrigerant was adapted to the system and 40 mL of distilled water was added. The system was refluxed for 4 h and cooled to room temperature. The humic residues (0.70 g) were filtered and extracted with CH2Cl2. The organic fractions were combined and concentrated to constant weight. The molar yield of crude LA obtained by this procedure was 61%. The obtained compound presented a composition of 93% in LA and the remaining 7% corresponds to unreacted 5-HMF. In a process with intermediate purifications, the final yield would be 25%.The crude LA was taken to an autoclave reactor to submit it to the catalytic hydrogenation test. For the test, an aqueous solution was prepared with the crude AL by dissolving the mass obtained (1.523 g) in 40 mL of water. A mass of 100 mg of the Ru/Z-A catalyst was added. This catalyst was prepared according to references [2]. Aliquots of the reactor solution were taken at different times. The reaction products were analyzed by gas chromatography and the conversion was obtained from the analysis of the decrease in LA. The conversion from LA to GVL was 95%. No other hydrogenation or hydrogenolysis products were detected. Taking into account that initially 20 mmol of fructose were reacted, and 12.5 mmol of GVL were obtained, the molar yield of GVL from fructose was 62.5%.This work shows a novel cascade process that involves a fructose dehydration reaction to obtain 5-HMF and its subsequent rehydration to obtain LA, both reactions catalyzed by a IL. The product obtained was subjected to a catalytic hydrogenation reaction to obtain GVL. The results obtained show that it has been possible to obtain a product with high added value from a sugar from biomass.