Highly active selective hydrogenation catalysts with a single-atom alloy structure were obtained at the Zelinsky Institute

The selective hydrogenation of alkynes is one of the key and most important reactions in modern catalysis. An illustrative example of its industrial use is the large-tonnage processes of selective hydrogenation of acetylenic hydrocarbons in pyrolysis of ethylene or styrene before they are sent to polymerization. In fine organic synthesis, the use of selective hydrogenation of alkynes makes it possible to obtain cis- and trans-olefins with high regio- and stereoselectivity — feedstock for the food, pharmaceutical (for example, synthesis of vitamins A, E and K) industries, as well as for the production of solvents, detergents etc. One of the promising directions in the development of highly selective catalysts, which has been actively studied in the past few years, is associated with the concept of “Single-Atom-Alloy (SAA) catalysts”. In these systems, active catalytic sites are Pd1 atoms isolated from each other by atoms of the second metal (M = Ag, Au, Zn, In), whose activity in hydrogenation is negligible. The use of monoatomic alloy catalysts provides an extremely high selectivity for the target product; however, their activity is, as a rule, insignificant due to the small number of isolated sites on the surface of PdM nanoparticles; therefore, an urgent task is to increase it.

The Laboratory of Catalysis by Supported Metals and Their Oxides of the Zelinsky Institute continues active research of the efficiency of catalysts for the selective hydrogenation of alkynes. In their recent work, the scientists used the support effect to increase the activity of the PdAg-SAA catalyst for the liquid-phase hydrogenation of diphenylacetylene. For the synthesis of catalysts, cerium-containing carriers CeO2–ZrO2 and CeO2–Al2O3 were applied. The results obtained by the authors indicate that the use of Ce-containing supports can significantly increase the activity of monoatomic PdAg-SAA catalysts in the selective hydrogenation of substituted alkynes. Thus, for PdAg/CeO2–ZrO2, a fivefold increase in the reaction rate was shown compared to the PdAg catalyst prepared on the basis of traditional Al2O3. It is extremely important that the increase in activity is not accompanied by a decrease in the selectivity of the formation of the target product. The increase in the activity of Ce-containing catalysts can be partially explained by a more than twofold increase in fineness, which leads to an increase in the surface area of bimetallic nanoparticles. In addition, according to the data of IR spectroscopy of adsorbed CO, the metal–carrier interaction, which leads to a change in the electronic state of PdAg nanoparticles, can play a role in increasing the activity. In turn, the retention of high selectivity of the synthesized catalysts indicates the stability of the structure of Pd1 monoatomic centers in the catalysts prepared by deposition on Ce-containing supports. The results obtained demonstrate that it is promising to use Ce-containing supports for the synthesis of catalysts for the selective hydrogenation of substituted alkynes.

The work was published in the special issue Single Atom Alloys: Modern Trends in Preparation and Application of the international journal Inorganics.

Currently, the Laboratory of Catalysis with Supported Metals and Their Oxides of the ZIOC continues to study the properties of SAA catalysts in selective hydrogenation reactions during the implementation of the Russian Science Foundation grant No. 23-13-00301.

Source:

Pavel V. Markov, Galina O. Bragina, Nadezhda S. Smirnova, Galina N. Baeva, Igor S. Mashkovsky, Evgeny Y. Gerasimov, Andrey V. Bukhtiyarov, Yan. V. Zubavichus, Alexander Y. Stakheev Single-Atom Alloy Pd1Ag10/CeO2–ZrO2 as a Promising Catalyst for Selective Alkyne Hydrogenation // Inorganics, 2023, 11, 150. DOI: 10.3390/inorganics11040150.