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Combination of supported bimetallic rhodium – molybdenum catalyst and cerium oxide for hydrogenation of amide

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ABSTRACT

Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6–7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh–MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2–8 MPa and 393–433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh–MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh–MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh–MoOx/SiO2, i.e. reducing the ratio of Mo–OH/Mo–O− sites.

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Effect of H2 pressure on hydrogenation of cyclohexanecarboxamide (CyCONH2) over Rh–MoOx catalyst + CeO2. Reaction conditions: Rh–MoOx/SiO2 (Rh 4 wt%, Mo/Rh = 1) 100 mg, CeO2 (uncalcined) 100 mg, 1,2-dimethoxyethane 20 g, H2 2–8 MPa, 413 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis.
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Figure 5: Effect of H2 pressure on hydrogenation of cyclohexanecarboxamide (CyCONH2) over Rh–MoOx catalyst + CeO2. Reaction conditions: Rh–MoOx/SiO2 (Rh 4 wt%, Mo/Rh = 1) 100 mg, CeO2 (uncalcined) 100 mg, 1,2-dimethoxyethane 20 g, H2 2–8 MPa, 413 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis.

Mentions: The effect of hydrogen pressure on the catalysis of Rh–MoOx/SiO2 + CeO2 was examined (figure 5). It should be noted that comparison of selectivities at different conversion level is possible because selectivities are hardly changed on reaction time until complete conversion (figure 1). Higher activity was observed under higher hydrogen pressure. The selectivity to CyCH2NH2 was also slightly increased with increasing hydrogen pressure, and instead the formation of unknown by-products was suppressed.


Combination of supported bimetallic rhodium – molybdenum catalyst and cerium oxide for hydrogenation of amide
Effect of H2 pressure on hydrogenation of cyclohexanecarboxamide (CyCONH2) over Rh–MoOx catalyst + CeO2. Reaction conditions: Rh–MoOx/SiO2 (Rh 4 wt%, Mo/Rh = 1) 100 mg, CeO2 (uncalcined) 100 mg, 1,2-dimethoxyethane 20 g, H2 2–8 MPa, 413 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036504&req=5

Figure 5: Effect of H2 pressure on hydrogenation of cyclohexanecarboxamide (CyCONH2) over Rh–MoOx catalyst + CeO2. Reaction conditions: Rh–MoOx/SiO2 (Rh 4 wt%, Mo/Rh = 1) 100 mg, CeO2 (uncalcined) 100 mg, 1,2-dimethoxyethane 20 g, H2 2–8 MPa, 413 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis.
Mentions: The effect of hydrogen pressure on the catalysis of Rh–MoOx/SiO2 + CeO2 was examined (figure 5). It should be noted that comparison of selectivities at different conversion level is possible because selectivities are hardly changed on reaction time until complete conversion (figure 1). Higher activity was observed under higher hydrogen pressure. The selectivity to CyCH2NH2 was also slightly increased with increasing hydrogen pressure, and instead the formation of unknown by-products was suppressed.

View Article: PubMed Central - PubMed

ABSTRACT

Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6–7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh–MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2–8 MPa and 393–433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh–MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh–MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh–MoOx/SiO2, i.e. reducing the ratio of Mo–OH/Mo–O− sites.

No MeSH data available.


Related in: MedlinePlus