Are Solid Catalysts Successfully Emulating Enzymes?

In many aspects, situ it exists between man-made catalysts and enzymes Can scientific insight into this similitude stimulate new research directions in catalysis? More precisely, can the understanding of the mechanisms of activity control in enzymes suggest new advances for man-made catalysis? Indeed, it is already possible to design catalysts with (i) new structures (e g presence of several phases) and (ii) a better balance between the toles of the different components The ambition is to keep the essential advantages of solids as catalysts, in particular robustness. easy separation from products. and tolerance to high temperatures. while adding the advantages typical of enzymes. like more activity. allostery, and more precise control of selectivity. in particular enantioselectivity The ambition is to build a bridge between robust man-made functional solids and fragile but extremely selective enzymes For that, results from a line of the work in out group will be use

Albert Szent-Györgyi von Nagyrapolt 1893-1986

Delmon Bernard. Albert Szent-Györgyi von Nagyrapolt 1893-1986 . In: Bulletin de la Classe des sciences, tome 1, 1990. pp. 33-40

Selectivity in Hds, Hdn, Hdo and Hydrocracking Contribution of Remote-control and Other New Concepts

This paper reviews some recent results in the field of hydrotreatment by sulfide catalysts. It comes in complement to a former review on the subject (1), by focusing more on new insights into the structure of the conventional CoMo (or NiMo) catalysts and the way they catalyze the various reactions involved. A first part constitutes an attempt to make an inventory of the types of catalytic sites : hydrogenation sites, sites active for the hydrogenolysis of carbon-heteroatom bonds, acidic sites either on the sulfide phase (probably -SH groups) or situated on the support. A second part discusses the influence of the morphology of the MoS2 crystallites, in particular the possibility that different catalytic functions be located on the rims and on the lateral edges. The variation in selectivity of the hydrotreatment catalysts as a function of the reaction conditions and their relative stability when the catalysts ages point to factors which are independent of initial morphology. The role of spillover hydrogen will be illustrated by new examples of our laboratory concerning hydrodenitrogenation, on the one hand, and the dramatic increase of acidity of silica alumina (by a factor of more than 10) under the influence of spillover hydrogen emitted by a sulfided CoMo/SiO2 catalyst, on the other hand. In the latter experiment, the hydrocracking of diphenyl methane served as a test reaction and the role of spillover was substantiated by H-D exchange experiments. In a last part, some prospects offered by the new advances will be outlined with a special emphasis on the controlled interconversion of sites due to remote control by spillover hydrogen. The new concepts can very likely be extended to many areas of hydrotreatment