Heterogeneous catalysis for fine chemicals: development of sustainable chemical processes
Innovating catalyst design for green reactions
Heterogeneous catalysis has found few applications to the synthesis of fine chemicals and pharmaceuticals relative to its wide use in the petroleum and commodity chemicals sectors. Nevertheless, the substitution of stoichiometric methodologies with catalytic alternatives is receiving increased attention as it is a route to the design of safer, cleaner, and more sustainable processes.
Among the many possibilities for application of heterogeneous catalysts in organic synthesis, the selective catalytic oxidations, hydrogenations and carbonylations are examples of highly atom efficient processes.
Selective oxidation is a green alternative to stoichiometric oxidations with permanganate, manganese dioxide and chromium(VI) reagents, major sources of waste, particularly in fine chemicals and pharmaceuticals manufacture. The selective oxidation of alkanes, alkynes and alcohols to the corresponding carbonyl compounds plays a central role in organic synthesis. Methods should preferably use a clean oxidant (e.g., O2 or H2O2) and be effective with a broad range of substrates. Gold, palladium and gold-palladium bimetallic nanoparticle catalysts have received attention for their excellent catalytic properties and high selectivity in oxidations, however gold has a limited impact on industrial catalysis. We have been studying the preparation of magnetically recoverable gold and gold-palladium catalysts with very interesting properties and reusable in successive reactions (see selected publications).
Selective hydrogenation of organic substrates is an important step in the preparation of various fine chemicals, with palladium being one of the metals most frequently used to catalyze these reactions. Selectivity is one of the main driving forces in heterogeneous catalyst’s design and development because of the multifunctional nature of the target molecules. Selective hydrogenation of nitro, nitriles, alkynes, and alkenes are of special relevance for the production of intermediates and final products. A variety of palladium catalysts promoted by a second metal are available for the conversion of alkynes into alkenes; for example, the Lindlar catalyst, comprised of a Pd catalyst partially poisoned with lead. Catalyst deactivation and the presence of toxic lead are the main drawbacks of this catalyst system. Lead-free Lindlar catalyst replacements are examples of highly desired developments in this field (see selected publications).
Our main goal is to explore the unique properties of metal nanoparticles for the design of heterogeneous catalysts, in special gold and palladium catalysts, for selective oxidations and hydrogenations.
The design of non-noble metal nanoparticle catalysts (Ni, Cu, etc.) to replace the high dependence on palladium for hydrogenation reactions is also under development.
Oliveira, R. L. ; Kiyohara, P. K. ; Rossi, L. M. High performance magnetic separation of gold nanoparticles for catalytic oxidation of alcohols. Green Chemistry, v. 12, p. 144-149, 2010.
Silva, T. A. G. ; Landers, R.; Rossi, L. M. Magnetically recoverable AuPd nanoparticles prepared by a coordination capture method as a reusable catalyst for green oxidation of benzyl alcohol. Catalysis Science & Technology, p. 2993-2999, 2013.
Silva, T. A. G. ; Teixeira-Neto, E.; López, N.; Rossi, L.M. Volcano-like Behavior of Au-Pd Core-shell Nanoparticles in the Selective Oxidation of Alcohols. Scientific Reports, v. 4, p. 5766, 2014.
Guerrero, M.; Costa, N.J. S.; Vono, L. L. R.; Rossi, L. M.; Gusevskaya, E. V.; Philippot, K. Taking advantage of a terpyridine ligand for the deposition of Pd nanoparticles onto a magnetic material for selective hydrogenation reactions. Journal of Materials Chemistry A, v. 1, p. 1441-1449, 2012.
Silva, F. P.; Rossi, L. M. Palladium on magnetite: magnetically recoverable catalyst for selective hydrogenation of acetylenic to olefinic compounds. Tetrahedron, v. 70, p. 3314-3318, 2014.
Uberman, P. M.; Costa, N. J. S. ; Philippot, K.; C. Carmona, R.; Dos Santos, A. A. ; Rossi, L.M. A recoverable Pd nanocatalyst for selective semi-hydrogenation of alkynes: hydrogenation of benzyl-propargylamines as a challenging model. Green Chemistry, v. 16, p. 4566-4574, 2014.
Garcia, M. A. S. ; Oliveira, K. C. B. ; Costa, J. C. S. ; Corio, P.; Gusevskaya, E. V. ; Dos Santos, E. N. ; Rossi, L. M. . Rhodium Nanoparticles as Precursors for the Preparation of an Efficient and Recyclable Hydroformylation Catalyst. ChemCatChem, v. 7, p. 1566-1572, 2015.
Garcia, M. A. S.; Heyder, R. S. ; Oliveira, K. C. B.; Costa, J. C. S.; Corio, P.; Gusevskaya, E. V.; Dos Santos, E. N.; Bazito, R. C.; Rossi, L. M. . Support Functionalization with a Phosphine-Containing Hyperbranched Polymer: A Strategy to Enhance Phosphine Grafting and Metal Loading in a Hydroformylation Catalyst. ChemCatChem, V. 8, P. 1951–1960, 2016.