Session: General Catalysis:

Nanostructured Pd-containing composites are the most widely used catalysts for hydrogenation of organic compounds. The activity of such systems strongly depends on their structure and is governed by the choice of preparation method. The aim of this work was to develop a highly active Pd-based catalyst for hydrogenation of quinoline and its analogues, which is an important step towards the reduction of Pd consumption in large-scale hydrogenation processes. The catalyst was prepared by Pd₂(dba)₃ decomposition in solution on Norite activated carbon; Pd content was 1 or 5 %. In order to compare the prepared catalyst with similar systems, a number of commercially-available Pd/C catalysts were tested in the same reaction.
The prepared composite contained ca. 20 nm Pd nanoparticles as evidenced by TEM, SEM and powder XRD, in contrary to previously reported similar system. The results of CO chemisorption were also consistent with the formation of ca. 20 nm Pd nanoparticles. Hydrogenation of qunoline at the presence of 1 % Pd/Norite in methanol was almost complete after 2 h at 30 °C and P(H₂) = 30 atm at n(Pd)/n(quinoline) ratio 0.0023, while lower catalyst loading (n(Pd)/n(quinoline) = 0.00093) resulted in decrease of the yield to 87 % (reaction time 4 h). The catalytic activity of 1 % Pd/Norite, evaluated as quinoline yield in the same conditions exceeded the activity of many commercially-available Pd/C catalysts. In the processes of 2-, 3- and 4-methylquinolines hydrogenation at presence of 1 % Pd/Norite the yields of respective methyl-1,2,3,4-tetrahydroquinolines at 30 °C and P(H₂) = 30 atm varied from 99 % for 2-methylquinoline to 26 % for 4-methylquinoline (n(Pd)/n(quinoline) = 0.0023). Hydrogenation of 6-chloroquinoline at the presence of 1 % Pd/Norite resulted in the formation of 6-chloro-1,2,3,4-tetrahydroquinoline with 71 % yield.

Sergey Kolotilov

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