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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 ).

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Acrolein is the simplest unsaturated aldehyde, which – due to its high reactivity – has found application as an intermediate in the chemical industry.

A cerium‐doped FePO4 catalyst dehydrates glycerol to acrolein in the gas phase but carbon accumulation reduces the reaction rate with time. Reaction rates may be maintained for longer times by co‐feeding low concentrations of oxygen together with the glycerol, but the acrolein yield drops proportionally to the oxygen concentration. The catalyst is easily regenerated by air and the reaction rate is proportional to both the oxygen concentration and quantity of carbon. The carbonaceous deposits may be due to both glycerol and acrolein: when either is fed to the catalyst, the CO2/CO ratio is close to 1; during the regeneration step, the CO2/CO ratio is near 4. A kinetic model of first order in both oxygen concentration and adsorbed sites characterizes the transient data very well.

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