Finely Controlled Platinum Nanoparticles over ZnO Nanorods for Selective Hydrogenation of 3‐Nitrostyrene to 3‐Vinylaniline

Abstract

Metallic platinum nanocatalysts play a key role in the liquid‐phase selective hydrogenation of substrates with more than one unsaturated bond. However, the commonly applied explanation for the effects of different electronic and geometric properties of catalysts on reactions remains of a heuristic nature due to the difficulties involved in preparing catalysts with precise structure. In this work, we have directly loaded pre‐synthesized metallic platinum nanoparticles onto well‐structured ZnO nanorods and then subjected them to thermal treatment in a reductive atmosphere for different temperatures. The effects of the different electronic and geometric properties of the catalysts on the selective reduction of 3‐nitrostyrene to 3‐vinylaniline as a model reaction have been rigorously explored through an analysis of the catalyst structures and the activity and selectivity profiles. Both the electron transfer from zinc to platinum and the decreased platinum surface density as a result of the formation of PtZn intermetallic compounds are key factors for improving the selectivity for the desired 3‐vinylaniline. Azobenzene was detected in the reaction with all the Pt/ZnO catalysts after 10–90 min, which indicates that the reaction follows a condensation mechanism.

Structural Regulation of PtCo/Y Zeolite Catalysts for the Selective Hydrogenation of 3-Nitrostyrene to 3-Vinylaniline

“…The hydrogenation of the CC bond in the reactant 3-NS yields 3-ethylnitrobenzene (3-ENB); the hydrogenation of nitro NO yields 3-VA, the target product; the successive hydrogenation of 3-ENB and 3-VA yields the byproduct 3-ethylaniline (3-EA; Figure ). The catalytic performance of the catalysts was assessed under the same reaction conditions, and the results are presented in Figure b–d. The PtCo/Y catalyst (calcined at 300 °C with 3.0 wt % Pt) had the most excellent selective hydrogenation performance of 3-NS with 99.75% conversion and 74.43% selectivity.…”

“…The hydrogenation of the C�C bond in the reactant 3-NS yields 3ethylnitrobenzene (3-ENB); the hydrogenation of nitro N�O yields 3-VA, the target product; the successive hydrogenation of 3-ENB and 3-VA yields the byproduct 3-ethylaniline (3-EA; Figure 4). 32 The catalytic performance of the catalysts was assessed under the same reaction conditions, and the results are presented in Figure 4b− VA, which is derived from the fact that introducing Co regulates the electronic state of Pt, making it more favorable for the adsorption of N�O than C�C bonds. 33,34 In addition, the smaller particle size and excellent dispersion of PtCo NPs are also conducive to improving the activity of the catalyst and the selectivity to 3-VA. 35 Moreover, the product distribution and the 3-NS conversion and selectivity of different products with time were investigated, and the results are shown in Figure S9.…”