Hydroisomerization of saturated hydrocarbons with novel MCM-41 immobilized Re(V) complex catalysts

The hetero-functionalized phosphines HPN2, H2PNO and HPN-Pip containing tricarbonyl Re(V) complexes, i.e. [Re(CO)3(κ3-PN2)] (I), [Re(CO)3Br(κ2-H2PNO)] (II) and [Re(CO)3Br(κ2-HPN-Pip)] (III) were covalently bonded to modified and MCM-41 to obtain novel supported hybrid catalysts. Remarkable high catalytic effects were observed with these catalysts in the hydroisomerization of n-alkanes at low temperature. The catalyst II/MCM-41 provided the highest TONs 3.32 × 103 with 37% yield for n-hexane and 3.18 × 103 with 30% yield for n-heptane. Under optimized condition, good selectivities for n-hexane (85%) and for n-heptane (91%) were obtained. The TGA was used to evaluate the stability of catalysts and reusable for several cycles. A possible carbenium-based mechanism been used to explain product formation.

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► Single site anchored tricarbonyl Re(V) complexes into modified MCM-41 as supported hybrid catalysts.
► Application in n-alkanes hydro-reformation.
► High TONs from 2100 to 3300 with selectivity 85% for n-hexane and 91% for n-heptane.
► Thermally stable (up to 200 °C) and recyclable.