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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 reaction temperature 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 8 MPa, 393–433 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis. ∗: half amount of catalyst and CeO2 was used (50 mg each).
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Figure 6: Effect of reaction temperature 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 8 MPa, 393–433 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis. ∗: half amount of catalyst and CeO2 was used (50 mg each).

Mentions: Figure 6 shows the effect of reaction temperature. Higher temperature increased the activity. The selectivity to CyCH2NH2 became slightly higher with increasing the temperature, as clearly seen up to 423 K. At 433 K, the conversion level was too high to compare selectivity in the standard reaction conditions. Therefore we further conducted reaction tests at 433 K (and 413 K for comparison) with smaller amount of Rh–MoOx/SiO2 catalyst and CeO2. The selectivity to aminomethylcyclohexane was higher at 433 K than 413 K. After all, higher hydrogen pressure and higher reaction temperature are favorable in this reaction.


Combination of supported bimetallic rhodium – molybdenum catalyst and cerium oxide for hydrogenation of amide
Effect of reaction temperature 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 8 MPa, 393–433 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis. ∗: half amount of catalyst and CeO2 was used (50 mg each).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Effect of reaction temperature 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 8 MPa, 393–433 K, 4 h. Cy = cyclohexyl. ‘Others’ comprise unknown solid products leading to loss of carbon balance during catalysis. ∗: half amount of catalyst and CeO2 was used (50 mg each).
Mentions: Figure 6 shows the effect of reaction temperature. Higher temperature increased the activity. The selectivity to CyCH2NH2 became slightly higher with increasing the temperature, as clearly seen up to 423 K. At 433 K, the conversion level was too high to compare selectivity in the standard reaction conditions. Therefore we further conducted reaction tests at 433 K (and 413 K for comparison) with smaller amount of Rh–MoOx/SiO2 catalyst and CeO2. The selectivity to aminomethylcyclohexane was higher at 433 K than 413 K. After all, higher hydrogen pressure and higher reaction temperature are favorable in this reaction.

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