Rhodium exchanged ETS-10 and ETS-4: Efficient heterogeneous catalyst for hydroaminomethylation

• Rhodium exchanged ETS-4 and ETS-10 for effective and fast hydroaminomethylation.
• A confined homogenous–heterogeneous dual nature of the catalyst is investigated.
• Low reaction time of 4 h with 100% conversion.
• Catalyst recycled successfully up to three cycles.

Rhodium exchanged titanosilicates (ETS-10 and ETS-4) were synthesized and found to be efficient and stable catalysts for hydroaminomethylation reaction. The catalyst was highly active and selective towards amine product within lower reaction time of 4 h. 1-Hexene and pyrrolidine were taken as representative substrates for parametric variations using Rh-ETS-10. The increase in pyrrolidine ratio gave some significant information showing a decrease in conversion with increased selectivity. The reason may be the competition between pyrrolidine and 1-hexene for coordination sites in rhodium and which prevents the beta-hydride elimination. The ratios of H2 and CO have influenced hydroaminomethylation and the best performance was in the CO:H2 ratio of 1:4 under the studied conditions. The initial rate of formation of amine was double than that of isomerization of 1-hexene. The Rh cluster like complex was formed on treating the catalyst with syn gas. A homogenous–heterogeneous dual nature of Rh was found during hydroaminomethylation. The catalyst was effectively recycled for three times without much loss in its activity and selectivity.

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