Abstract
Series catalysts of Ru-SnOx/Al2O3 with varying SnOx loading of 0–3 wt% were prepared, and their catalytic activity and selectivity have been discussed and compared for the selective hydrogenation of m-dinitrobenzene (m-DNB) to m-nitroaniline (m-NAN). The Ru-SnOx/Al2O3 catalysts were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and hydrogen temperature-programmed reduction (H2-TPR) and desorption (H2-TPD). Under the modification of SnOx, the reaction activity increased obviously, and the best selectivity to m-NAN reached above 97% at the complete conversion of m-DNB. With the increasing of the SnOx loading, the amount of active hydrogen adsorption on the surface of the catalyst increased according to the H2-TPD analysis, and the electron transferred from Ru to SnOx species, as determined by XPS, inducing an electron-deficient Ru, which is a benefit for the absorption of the nitro group. Therefore, the reaction rate and product selectivity were greatly enhanced. Moreover, the Ru-SnOx/Al2O3 catalyst presented high stability: it could be recycled four times without any loss in activity and selectivity.
Highlights
Introduction mNitroaniline (m-NAN) is an important intermediate for the preparation of dyes, mechanical and electronic corrosion inhibitors, urethanes and pharmaceuticals
The catalytic performance of the supported Ru catalysts was compared for the hydrogenation of m-DNB to m-NAN, and it was found that the support has a large effect on the reaction rate and product selectivity
Ru/Al2O3 exhibits a high selectivity of >97%, but its activity is much lower compared with the Ru/TiO2
Summary
A series of supported Ru catalysts with different supports were prepared, and their catalytic performances on the hydrogenation of m-DNB were compared. The crystallinity of Ru and the loading of SnOx may have a great influence on the adsorption and desorption of the substrates, intermediates and products, resulting in the higher catalytic activity and the highest selectivity to m-NAN (97.3%) at the complete conversion for the catalyst with. 2% SnOx. In addition, the EDX spectra of Ru-SnOx/Al2O3-2% showed the emission of Ru and Sn, indicating that Sn was certainly doped onto the surface of the catalyst, even though SnOx was not detected by the XRD (Figure 2). The developed Ru-SnO2/Al2O3-2% catalyst is an efficient catalyst for the hydrogenation of m-DNB with satisfactory activity, selectivity and stability; it is expected to have potential industrial applications
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