Advances in the preparation of highly selective nanocatalysts for the semi-hydrogenation of alkynes using colloidal approaches

Abstract

In the last decade, the semi-hydrogenation of alkynes has experienced significant advances in terms of fine control of alkene selectivity and prevention of the over-hydrogenation reaction. Such advances have been possible to a large extent through the progress in colloidal methods for the preparation of metallic nanoparticles. The present review describes the contributions in the field of the selective hydrogenation of alkynes involving the utilization of colloidal methodologies. These approaches permit the fine modulation of several parameters affecting the catalytic performance of the active phase such as the particle size, the bulk and the surface structure and composition. For the transformation of liquid substrates, the nature of the stabilizers, the reducing agents and the metal precursors employed for the synthesis of the catalysts can be tuned to enhance the alkene selectivity. In contrast, in catalytic transformations of gaseous substrates, the presence of adsorbed species at the metal surface usually gives detrimental results while the interplay between the support and the active phase appears to be a more convincing alternative for catalyst tuning.

Design of Single Gold Atoms on Nitrogen‐Doped Carbon for Molecular Recognition in Alkyne Semi‐Hydrogenation

“…Thep erformance of the nanostructured gold catalysts (Au/NC-T and Au/AC-T)w as evaluated in the continuous flow three-phase semi-hydrogenation of 1-hexyne and 2methyl-3-butyn-2-ol (Figure 3a and Figure S9), two relevant reactions in the production of a-olefins and synthesis of intermediate for vitamins. [13] Thesingle-atom catalyst Au/AC-413 shows approximately three-fold higher activity than the rest Au/ACs amples containing mainly Au nanoparticles.O n the other hand, the two substrates display strikingly different catalytic responses on the Au/NC-T series.W hile the 1hexyne hydrogenation activity is independent on the activation temperature and consequent Au speciation, av olcanolike curve is observed in the case of 2-methyl-3-butyn-2-ol. In accordance with the literature reports, [14] all these gold systems give essentially full selectivity to the aimed alkenes.…”

An Active Palladium Colloidal Catalyst for the Selective Oxidative Heterocoupling of (Hetero)Aryl Boronic Acids

“…In comparison to commonly employed homogeneous or heterogeneous catalysts, nano or colloidal metal catalysts are ever more clearly evidencing enhanced reactivity and selectivity. [21] Several factorss uch as surface compositiona nd surface stabilizationo ft he nanoparticles/colloidal particles, morphology of the nanoparticles as well as their sizes are key contributors to their unparalleled reactivity. [22] Fine tuning these factors shoulda llow the development of superior, more efficient catalytic technologies for CÀCb ond formation processes.O ne contribution to the development of novel CÀC bond forming technologies by using activep alladium colloidal catalysts from our group was published recently covering the efficient homocoupling of aryl boronic acids.…”

Pd‐Colloids‐Catalyzed/Ag2O‐Oxidized General and Selective Esterification of Benzylic Alcohols

“…In comparison to commonly employed homogeneous or heterogeneousc atalysts, nano-or colloidal-metal catalysts are ever more clearly evidencing enhanced reactivity and selectivity. [40][41][42] Several factors such as surface composition and surface stabilizationo ft he nanoparticles/colloidal particles, morphology of the nanoparticles as well as their sizes are key contributors to their unparalleled reactivity. [44][45][46] Fine tuningt hese factors should allow the development of superior,m ore efficient catalytic technologies for CÀCb ond formation processes.O ne contribution to the development of novel CÀCbond forming technologies using active palladium colloidal catalysts from our group was published covering the efficient homocoupling and heterocouplingo fa rylboronic acids.T he isolation and the complete characterization of the synthesized palladium colloidal catalystw as possible by utilizing techniques such as TEM, HRTEM, XRD, XPS, EDS and EXAFS.…”