Karine De Oliveira Vigier

Conversion of fructose and inulin to 5-hydroxymethylfurfural in sustainable betaine hydrochloride-based media

We show here that betaine hydrochloride (BHC), a co-product of the carbohydrate industry, can be used for the design of cheap and safe media capable of promoting the dehydration of fructose and inulin to HMF. In particular, in these BHC-based media, HMF was obtained with up to 84% yield, thus offering a competitive route to the traditional imidazolium-based ionic liquids.

Acid-catalyzed dehydration of fructose and inulin with glycerol or glycerol carbonate as renewably sourced co-solvent.

Ionic liquids (ILs) can be partially substituted by glycerol or glycerol carbonate as cheap, safe, and renewably sourced co-solvents in the acid-catalyzed dehydration of fructose and inulin to 5-hydroxymethylfurfural (HMF). In the particular case of glycerol, we found that HMF can be conveniently extracted from the IL/glycerol (65:35) mixture with methylisobutylketone, limiting the reactivity of glycerol with HMF and allowing the recovery of HMF with a high purity (95 %). Influences of the fructose content, temperature, and the nature of the ionic liquid are also discussed. The possible use of industrial-grade glycerin is also investigated. We demonstrate that by using glycerol carbonate, up to 90 wt % of the IL can be successfully substituted, decreasing the environmental costs of traditional IL-based processes.

Dehydration of Highly Concentrated Solutions of Fructose to 5‐Hydroxymethylfurfural in a Cheap and Sustainable Choline Chloride/Carbon Dioxide System

Fête DES sciences: The dehydration of fructose and inulin to HMF is conveniently performed in a cheap and sustainable choline chloride/CO(2) deep eutectic solvent (DES) system. The medium is capable of converting high contents of fructose (>100 wt %) without affecting the yield of HMF (up to 72 %). The purity of the recovered HMF is >98%, and the reaction medium can be recycled.

Selective Hydrogenation of Furfural to Furfuryl Alcohol in the Presence of a Recyclable Cobalt/SBA‐15 Catalyst

The hydrogenation of furfural to furfuryl alcohol was performed in the presence of a Co/SBA-15 catalyst. High selectivity (96 %) at a conversion higher than 95 % is reported over this catalytic system. As the conversion of furfural to furfuryl alcohol occurs over metallic Co sites, the effect of reduction temperature, H2 pressure, and reaction temperature were studied. Optimum reaction conditions were: 150 °C, 1.5 h, 2.0 MPa of H2 . The catalyst was recyclable, and furfuryl alcohol was recovered with a purity higher than 90 %. The effect of the solvent concentration was also studied. With a minimum of 50 wt % of solvent, the selectivity to furfuryl alcohol and the conversion of furfural remained high (both over 80 %). Likewise, the activity of the catalyst is maintained even in pure furfural, which confirms the real potential of the proposed catalytic system. This catalyst was also used in the hydrogenation of levulinic acid to produce γ-valerolactone selectively.

Contribution of Deep Eutectic Solvents for Biomass Processing: Opportunities, Challenges, and Limitations

Since their introduction in 2004, deep eutectic solvents (DESs) have attracted interest in different fields of chemistry. In the case of biomass, DESs are particularly interesting, not only because of their low cost and biodegradability, but also due to their unique property to interact with hydrogen‐bond donors such as renewably sourced polyols or carboxylic acids. Through selected examples, we report the contribution of DESs for the dissolution of biomass, the extraction/purification of bioderived chemicals, and the conversion of carbohydrates to furanic derivatives. In all examples, we discuss how the DES can impact the selectivity of a chemical process and the limitations associated with the use of DES. In particular, impact of the DES viscosity on extraction, the recovery and recycling of DES, and the stabilization of chemical intermediates in DES are among the key aspects that are discussed.

Combination of Pd/C and Amberlyst-15 in a single reactor for the acid/hydrogenating catalytic conversion of carbohydrates to 5-hydroxy-2,5-hexanedione

Here we show that combination of Pd/C and Amberlyst-15 in a single reactor allowed fructose and inulin to be converted to 5-hydroxy-2-5-hexanedione, a valuable chemical platform, in a one-pot process.

Palladium/Carbon Dioxide Cooperative Catalysis for the Production of Diketone Derivatives from Carbohydrates

The one-pot production of industrially valuable diketone derivatives from carbohydrates is achieved through a bifunctional catalytic process. In particular, Pd/C-catalyzed hydrogenation of HMF in water and under CO2 affords 1-hydroxypentane-2,5-dione with up to 77% yield. The process is also eligible starting from fructose and inulin, affording 1-hydroxyhexane-2,5-dione with 36% and 15% yield, respectively. The key of the process is reversible in situ formation of carbonic acid, which is capable of assisting Pd/C during the hydrogenation reaction by promoting the dehydration of carbohydrates and the ring-opening of furanic intermediates. Interestingly, by changing the reaction medium from H2 O to a H2 O/THF mixture (1:9), it is possible to switch the selectivity of the reaction and to produce 2,5-hexanadione with 83% yield. Within the framework of sustainable chemistry, reactions presented in this report show 100% carbon economy, involve CO2 to generate acidity, require water as a solvent, and are conducted under rather low hydrogen pressures (10 bar).

Pretreatment of microcrystalline cellulose by ultrasounds: effect of particle size in the heterogeneously-catalyzed hydrolysis of cellulose to glucose

In this paper, we show that ultrasound technology is a powerful tool for enhancing the reactivity of microcrystalline cellulose (MCC) in the presence of a solid acid catalyst. The effects of sonication on the MCC structure were studied using different characterization methods. In particular we found that pretreatment of cellulose by ultrasounds resulted in a drastic decrease of MCC particle size (<0.4 μm), leading to a better interaction with solid catalyst surfaces. As a result, the subsequent hydrolysis of sonicated MCC over a recyclable sulfonated carbon solid catalyst was found to be highly selective in producing water-soluble reducing sugars. Using such a pretreatment, glucose was produced with similar yields (up to 42%) to those obtained using conventional pretreatment methods such as ball-milling or ionic liquids, thus showing the efficiency of such a method. From the viewpoint of green chemistry, the pretreatment by ultrasound has noticeable advantages such as (1) the use of water as a unique solvent, (2) short reaction time (<3 h), (3) no need of external source of heating (ensured by dissipated energy from sonication) and (4) no polluting effluent involved or produced.

Heterogeneously-catalyzed conversion of carbohydrates.

Polyfunctionality of carbohydrates and their low solubility in conventional organic solvents make rather complex their conversion to higher value added chemicals. Therefore, innovative processes are now strongly needed in order to increase the selectivity of these reactions. Here, we report an overview of the different heterogeneously-catalyzed processes described in the literature. In particular, hydrolysis, dehydration, oxidation, esterification, and etherification of carbohydrates are presented. We shall discuss the main structural parameters that need to be controlled and that permit the conversion of carbohydrates to bioproducts with good selectivity. The conversion of monosaccharides and disaccharides over solid catalysts, as well as recent advances in the heterogeneously-catalyzed conversion of cellulose, will be presented.

Combination of ball-milling and non-thermal atmospheric plasma as physical treatments for the saccharification of microcrystalline cellulose

Here we report that non-thermal atmospheric plasma (NTAP) can be used as a physical treatment for the extensive depolymerization of amorphous cellulose to low molecular weight cello-oligomers (DP = 36). Such NTAP treatment does not require addition of any solvent and catalyst, thus facilitating the recovery of cello-oligomers. Additionally, the NTAP treatment was found to be highly selective since degradation/oxidation of glucose units occurs to a rather small extent (purity of cello-oligomers >90%). These low molecular weight cello-oligomers recovered after NTAP treatment were then more prone to hydrolysis than native cellulose and were easily hydrolyzed to glucose over a cation exchange resin with an unprecedented yield of 58%.