Gas phase selective hydrogenation over oxide supported Ni-Au.
Fernando Cárdenas-Lizana1, Mark A Keane
1Chemical Engineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, Scotland. M.A.Keane@hw.ac.uk.
Gold and nickel-gold catalysts were used for the continuous gas phase hydrogenation of nitroarenes. Nickel-promoted gold catalysts enhanced the reduction rate, demonstrating efficient production of functionalized anilines.
Area of Science:
- Catalysis
- Materials Science
- Organic Chemistry
Background:
- Nitroarene hydrogenation is crucial for producing anilines, key intermediates in pharmaceuticals and dyes.
- Developing selective and efficient catalysts for gas-phase hydrogenation remains a significant challenge.
Purpose of the Study:
- To investigate the chemoselective continuous gas phase hydrogenation of nitroarenes using supported gold (Au) and nickel-gold (Ni-Au) catalysts.
- To evaluate the effect of catalyst composition, particle size, and support material on hydrogenation performance.
Main Methods:
- Gas phase hydrogenation of p-chloronitrobenzene (p-CNB) and m-dinitrobenzene (m-DNB) at 573 K and 1 atm.
- Characterization of catalysts using Transmission Electron Microscopy (TEM), Temperature Programmed Desorption (TPD), Temperature Programmed Reduction (TPR), and Energy-Dispersive X-ray (EDX) spectroscopy.
- Analysis of product selectivity and conversion rates.
Main Results:
- Monometallic Au catalysts selectively produced p-chloroaniline (p-CAN) and m-nitroaniline (m-NAN), with higher rates over smaller Au particles.
- Ni-Au bimetallic catalysts showed enhanced -NO2 group reduction rates due to increased spillover hydrogen.
- Full selectivity to p-CAN was maintained with Ni-Au catalysts; m-DNB conversion yielded m-NAN or m-phenylenediamine depending on Ni content and support (Al2O3 or TiO2).
Conclusions:
- Ni-promotion of Au significantly enhances the hydrogenation rate of nitroarenes.
- Supported Ni-Au catalysts are viable for the continuous production of functionalized anilines.
- Catalyst design, including Ni content and support choice, allows tuning of selectivity for aniline derivatives.
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