Elodie Fourré

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%.

Operando DRIFT Spectroscopy Characterization of Intermediate Species on Catalysts Surface in VOC Removal from Air by Non-thermal Plasma Assisted Catalysis

An innovative plasma discharge reactor was developed to fit an infrared cell and to allow the in situ characterization of isopropanol (IPA) and toluene decomposition at the surface of three metal oxides (γ-Al2O3, TiO2 and CeO2). The impact of the plasma discharge on the conversion of these pollutants, with the material placed in the discharge area, was studied under real time conditions at atmospheric pressure via infrared analysis. The plasma treatment of IPA molecules led to the formation of acetone, propene, acetic acid and/or formic acid. By contrast, the toluene oxidation led to the rapid opening of the aromatic ring, followed by the total oxidation through carboxylic formation of the species arising from the toluene molecules fragmentation.

Fast and solvent free polymerization of carbohydrates induced by non-thermal atmospheric plasma

Non-thermal atmospheric plasma (NTAP) is a physical technology that has been previously employed for surface treatment (cleaning, coating, erosion, etc.) and water or air depollution. We show here that, beyond surface effects, NTAP is capable of enabling the complete and fast polymerization of various mono- and disaccharides in the solid state within only a few minutes and at low temperature (40-80 [degree]C). NTAP-induced polymerization involves a radical mechanism and yields water soluble polysaccharides with a mean molar mass of up to 100 000 g mol-1 and a mean hydrodynamic radius of 3 nm. Although polymerization reactions promoted by NTAP occurs in a random manner, the [small alpha]-1,6 and [small beta]-1,6 linkages are however dominant. Furthermore, we discovered that NTAP is highly selective, strongly favoring glycosylation over other chemical transformations in the bulk. Under our working conditions, glycosyl units are preserved that constitute the repeating units of the polysaccharide product. No chemical degradation (e.g. intramolecular dehydration reactions) was observed, allowing a white powder to be recovered with a yield higher than 93 wt%. From a practical point of view, NTAP has great potential for breakthrough in the production of polysaccharides, notably because it does not require the use of a solvent or catalyst, thus by-passing the traditional post-treatment of aqueous effluents and catalyst recycling characteristic of biotechnological polysaccharide production. Its efficiency at low temperature also prevents carbohydrates from degradation. Finally, NTAP proceeds on an on/off switch basis, allowing the polymerization reaction to be started and stopped quasi instantaneously.

Impact of Nonthermal Atmospheric Plasma on the Structure of Cellulose: Access to Soluble Branched Glucans

We have investigated the effect of non-thermal atmospheric plasma (NTAP) on the structure of microcrystalline cellulose. In particular, by means of different characterization methods, we demonstrate that NTAP promotes the partial cleavage of the β-1,4 glycosidic bond of cellulose leading to the release of short-chain cellodextrins that are reassembled in situ, preferentially at the C6 position, to form branched glucans with either a glucosyl or anhydroglucosyl terminal residue. The ramification of cellulosic chain induced by NTAP yields branched glucans that are soluble in DMSO or in water, thus opening a straightforward access to processable glucans from cellulose. Importantly, the absence of solvent and catalyst considerably facilitates downstream processing as compared to (bio)catalytic processes which typically occur in diluted conditions.

Non Thermal Plasma Functionalized 2D Carbon–Carbon Composites as Supports for Co Nanoparticles

AbstractNovel two-dimensional carbon–carbon composites made of carbon nanofibers (CNFs) supported on a carbon preform were functionalized by non thermal plasma treatment (room temperature, atmospheric pressure, humid air), before being used as supports for metallic cobalt nanoparticles. It was shown that the degree of functionalization of the carbon nanofibers depends on the plasma power input, the treatment time and the CNF loading. The size of the cobalt nanoparticles generated after subsequent reduction of the Co-containing plasma treated CNF/C composites under hydrogen flow seems to be independent of the amount of supported cobalt. Changes in surface characteristics were analyzed using thermogravimetric analyses coupled to a mass spectrometer, X-ray photoelectron spectroscopy analyses and Raman spectroscopy. Transmission electron microscopy was used to complementary characterize the final size, dispersion and location of the so generated Co nanoparticles.