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 FeMoO 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 NH -, SO -, and methanol-adsorption microcalorimetry. A MgO/SiO catalyst was the most active in acrolein production owing to an appropriate ratio of basic to acidic sites.

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/SiO , NbP, and heteropolyanions on silica, HPA/SiO ). 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 CO production. On strong acid sites, production of acrolein and carbon oxides (CO ) 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 ) of very strong basic sites (Q >150 kJ mol ).

Molybdenum carbides supported on TiO2 or ZrO2 were prepared by temperature programmed reduction carburization method using mixtures of hydrogen and hydrocarbon (methane or ethane). All the materials exhibited molybdenum carbide with cubic crystallographic structure. The carbon content and MoC lattice parameter increased with the increase of hydrocarbon percentage (5-40%) and temperature (600-800°C) during carburization. All catalysts were significantly active in the hydrogenation of succinic acid to butyric acid and γ-butyrolactone. For the first time, a correlation between the degree of carburization and the catalytic activity for succinic acid hydrogenation was established. The selectivity depends strongly on the support. MoC/TiO2 favored the formation of butyric acid while MoC/ZrO2 and bulk MoC generated primarily γ-butyrolactone. The stability of MoC/TiO2 up to 50 h on stream in continuous reactor was demonstrated, showing the interest of carbide catalysts for future biorefinery processes.

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The Inside Cover picture shows the magic of acrolein direct synthesis by oxidative coupling of alcohols (OCA). The process starts by methanol and ethanol oxidation to formaldehyde and acetaldehyde, respectively, on a FeMoOx redox catalyst followed by the cross‐aldolization of aldehydes and dehydration to acrolein taking place on the acid/base catalyst. The alcohols involved in this process can be biosourced; therefore, this new route to produce acrolein is even more interesting as it can replace current fossil‐based production of acrolein (oxidation of propylene). In their Full Paper (DOI: 10.1002/cssc.201700230), Lilić et al. on page 1916 in Issue 9, 2017, discuss the influence of the acid/base sites on the acrolein yield.