Jean-François Devaux

An acrolein production route from ethanol and methanol mixtures over FeMo-based catalysts

Acrolein is the simplest unsaturated aldehyde, which – due to its high reactivity – has found application as an intermediate in the chemical industry. Nowadays, this chemical is commercially obtained by propylene oxidation, which is based on fossil resources. Herein, an alternative production method starting from methanol and ethanol mixtures is presented. The reaction was performed over FeMo-based catalysts synthesized at different Mo/Fe ratios (i.e., 1.5, 2.0 and 2.5) and calcined at different temperatures (i.e., 350, 400 and 450 °C). The operational conditions were found by a Design of Experiments method, which showed that the most important factor influencing the acrolein yield was the reaction temperature. During these studies the best catalytic performance was observed for FeMo2.5 calcined at 400 °C (i.e., 39%). Catalysts were characterised by different methods (e.g., TGA-DSC, XRD, etc.). Advanced quasi in situ XPS studies have shown that the molybdenum present on the catalyst surface performs the redox cycle during the reaction.

Influence of Catalyst Acid/Base Properties in Acrolein Production by Oxidative Coupling of Ethanol and Methanol

Oxidative coupling of methanol and ethanol represents a new route to produce acrolein. In this work, the overall reaction was decoupled in two steps, the oxidation and the aldolization, by using two consecutive reactors to investigate the role of the acid/base properties of silica-supported oxide catalysts. The oxidation of a mixture of methanol and ethanol to formaldehyde and acetaldehyde was performed over a FeMoOx catalyst, and then the product mixture was transferred without intermediate separation to a second reactor, in which the aldol condensation and dehydration to acrolein were performed over the supported oxides. The impact of the acid/base properties on the selectivity towards acrolein was investigated under oxidizing conditions for the first time. The acid/base properties of the catalysts were investigated by NH3 -, SO2 -, and methanol-adsorption microcalorimetry. A MgO/SiO2 catalyst was the most active in acrolein production owing to an appropriate ratio of basic to acidic sites.

A comparative study of basic, amphoteric and acidic catalysts in the oxidative coupling of methanol and ethanol for acrolein production

The impact of acid/base properties (determined by adsorption microcalorimetry) of various catalysts on the cross-aldolization of acetaldehyde and formaldehyde leading to acrolein was methodically studied in oxidizing conditions starting from a mixture of methanol and ethanol. The aldol condensation and further dehydration to acrolein were carried out on catalysts presenting various acid/base properties (MgO, Mg-Al oxides, Mg/SiO2 , NbP, and heteropolyanions on silica, HPA/SiO2 ). Thermodynamic calculations revealed that cross-aldolization is always favored compared with self-aldolization of acetaldehyde, which leads to crotonaldehyde formation. The presence of strong basic sites is shown to be necessary, but a too high amount drastically increases COx production. On strong acid sites, production of acrolein and carbon oxides (COx ) does not increase with temperature. The optimal catalyst for this process should be amphoteric with a balanced acid/base cooperation of medium strength sites and a small amount (<100 μmol g-1 ) of very strong basic sites (Qdiff >150 kJ mol-1 ).