Virginie Belliere-Baca

Glycerol dehydration to acrolein in the context of new uses of glycerol

Catalytic dehydration of glycerol to acrolein has the potential to valorise the glut of crude glycerol issuing from biodiesel production. This reaction requires catalysts with appropriate acidity, and intensive research activities have been focused on the application of families of catalysts including zeolites, heteropolyacids, mixed metal oxides and (oxo)-pyrophosphates, as their acidic properties are well-known. Nevertheless, their deactivation by coking remains the main obstacle in the way of large-scale industrial applications. Considering this important issue, various technologies have been proposed for regenerating the catalysts. This review shows that a well-balanced combination of an appropriate catalytic system together with an adapted regeneration process could put large-scale industrial applications within reach.

A long-life catalyst for glycerol dehydration to acrolein

While the initial catalytic performances of silica-supported silicotungstic acid are high in the glycerol dehydration reaction, they rapidly decrease with time on stream and the acrolein yield quickly decreases.

Regeneration of silica-supported silicotungstic acid as a catalyst for the dehydration of glycerol.

The dehydration reaction of glycerol to acrolein is catalyzed by acid catalysts. These catalysts tend to suffer from the formation of carbonaceous species on their surface (coking), which leads to substantial degradation of their performances (deactivation). To regenerate the as-deactivated catalysts, various techniques have been proposed so far, such as the co-feeding of oxygen, continuous regeneration by using a moving catalytic bed, or alternating between reaction and regeneration. Herein, we study the regeneration of supported heteropolyacid catalysts. We show that the support has a strong impact on the thermal stability of the active phase. In particular, zirconia has been found to stabilize silicotungstic acid, thus enabling the nondestructive regeneration of the catalyst. Furthermore, the addition of steam to the regeneration feed has a positive impact by hindering the degradation reaction by equilibrium displacement. The catalysts are further used in a periodic reaction/regeneration process, whereby the possibility of maintaining long-term catalytic performances is evidenced.

Synthesis and characterization of zirconia-grafted SBA-15 nanocomposites

The preparation of highly ordered mesoporous zirconia is of special interest when targeting applications in catalysis. Nevertheless, most of the previously reported attempts led to materials with a low hydrothermal stability. Herein, we accordingly report about the benefit of using mesoporous silica as a host support in which accessible zirconia crystallites are stabilized on the surface. The zirconia surface coverage could be tuned and optimized by playing on the most sensitive synthesis parameters, namely the quantity of zirconia, the calcination temperature and the pore diameter of the host support. The acid properties of the so-obtained materials were determined, showing a remarkable linear relationship between the amount of introduced zirconia and the number of acid sites, which evidenced a high accessibility of the acid sites in the nano-composite, due to a homogeneous dispersion of the zirconia phase in the pores of the silica host support.