Molecular sieve catalysts as substitutes for metal chlorides in the chemical industry: Some selected examples
Résumé
The current main concern of global sustainable development pushes toward the substitution of corrosive and highly waste-producing chlorine-containing conventional catalysts (such as the strongly acidic AlCl3-HCl mixture, still widely used in the production of chemicals) by environmentally friendly systems. The outstanding benefits in terms of environmental sustainability as well as of economic advantage related to the use of acid and micro- and/or mesoporous molecular sieves are here depicted, analyzing some selected examples in the field of oil refining, petrochemicals, and fine chemicals production: namely, n-C-5-C-6 alkane isomerization, isobutane/butene (I/B) alkylation, benzene ethylation, aromatic acylation, and Fries rearrangement. In the large-scale processes of refining and petrochemistry, the shift toward this kind of green and efficient solid catalysts is an established reality. In contrast, in fine chemicals synthesis, most of the novelties are still at a lab-scale level, and additional hurdles, related to the large differences between the national legislations about environmental protection, strongly limit this substitution.