Christophe Vallée

The objective of this work was to investigate the ability of supercritical (SC) ethanol conditions to attack preferentially the lignin fraction against the carbohydrate fraction and their effects on the product distribution among gases, light products, bio-oils, and chars. In this study, the conversion of each pinewood component was determined by the analysis of solid residues to quantify cellulose, hemicellulose, lignin, and char contents. It is shown that, by tuning the temperature, hemicellulose and lignin are already transformed in subcritical ethanol conditions, lignin being more reactive than hemicellulose. In contrast, native wood cellulose is recalcitrant to liquefaction in SC ethanol near the critical point ( T _c = 241 °C and P _c = 61 bar), but 20% of native wood cellulose is converted in SC ethanol at 280 °C. Besides, the severity of the conditions, in terms of temperature and treatment time, does not significantly influence the yields of gases, light products, and bio-oils but strongly enhances char formation. Interestingly, the increase in SC ethanol density does not change the conversion of biomass components but has a marked effect on bio-oil yield and prevents char formation. The optimum fractionation conditions to convert the lignin component, while keeping unattacked the cellulose fraction with a minimum formation of char, are dense SC ethanol, at 250 °C for 1 h, in batch conditions. However, although lignin is more reactive than hemicellulose under these conditions, these fractions are converted, in a parallel way, to around 50% and 60%, respectively.

A cold holocellulose treatment (cHolT) was studied on a bleached kraft pulp (BKP) of Eucalyptus to observe the degradation of polysaccharides in pulp by chlorite at room temperature under conditions of slightly acidic pH and high chlorine charge (313% of active chlorine on BKP). Based on literature data, cellulose depolymerization is expectable by chlorite treatments at 70°C and reinforced chlorite charge, while the addition of dissolved lignin could protect cellulose. In the present study, polysaccharide degradation was followed by TAPPI viscosity, size-exclusion chromatography coupled to multidetectors, pulp yield, kappa number, elemental sugar analysis of pulps, and total organic carbon detection in filtrates. cHolTs were repeated several times without significant polysaccharide degradation, but the insertion of a caustic extraction stage at 70°C induced little degradation. This study opens the way to the setup of inert delignification procedures to be applied on raw or processed lignocellulosic samples from biorefinery studies.

Biofuels, which are produced from renewable vegetable sources are considered as a good solution to reduce the European dependence on fossil fuel sources, from a geostrategic and environmental point of view. Because of the high proportion of diesel vehicles in Europe, biodiesel still remains by far the most produced biofuel, far ahead of ethanol. Biodiesel is obtained by transesterification of vegetable oils with an alcohol, usually methanol to produce methyl esters. This paper aims to present the contribution of the French institute IFP Energies nouvelles to this issue, through the development of two processes for biodiesel production by means of homogeneous or heterogeneous catalysis. More recent developments have focused on hydrotreating vegetable oils and are also detailed in this paper. Fuels from this latest technology are drop-in fuels allowing higher incorporation rates and offering excellent qualities for diesel engines and potentially for incorporation in Jet fuel

A novel heterodifunctional phosphinite imidazolium salt was synthesized and reacted with Ag(I) to afford an unusual tetrasilver cubane-type cluster with two P-NHC ligands bridging between the Ag(I) centres of opposite Ag₂I₂ faces.