Highly Dispersed Platinum Nanoparticles Catalyst Prepared By Atomic Layer Deposition For Hydrogenation Reaction

Since twenty-first Century, the industry has developed rapidly, the problem of energy and environment has become a great challenge in the development of the economy. The application of the catalyst in the industrial production is becoming more and more important. Improving the performance of the catalyst can reduce energy consumption, improve production efficiency, reduce production costs and reduce the unnecessary by-products generated from the process of reactions which may lead to the pollution of the environment. In general, the particle size of the active component in the catalyst and the particle distribution supported on the carrier are very important factors affecting the catalyst activity, selectivity and stability. Many scientific research have focus on the noble metal platinum due to their excellent catalytic properties.Highly dispersed platinum nanoparticles with a controlled uniform size supported on carbon nanotubes(CNTs) are prepared by atomic layer deposition(ALD). The platinum catalysts supported on carbon nanotubes(Pt/CNTs) show good catalytic properties in hydrogenation reaction, we adopt the hydrogenation reaction of styrene as probe reaction to study the impact of platinum particle size on catalytic activity. The results show that Pt particle size can be tuned in the range of 1 nm by atomic layer deposition method, and the platinum nanoparticle size with about 0.5nm show the highest activity for the hydrogenation of styrene.Pt/CNTs catalyst is also prepared by impregnation method in this paper. They have the same platinum loading with the Pt/CNTs catalyst obtained by atomic layer deposition method. Pt/CNTs catalysts prepared by impregnation method have a larger particle size while the catalyst prepared by atomic layer deposition has a smaller particle size and more uniform distribution. For the hydrogenation reaction of styrene and nitrobenzene, Pt/CNTs catalysts prepared by atomic layer deposition show higher the activity and selectivity. The results show that Pt/CNTs catalyst prepared by atomic layer deposition show higher reaction rate for the transformation of the above two hydrogenation reactions. The Pt/CNTs catalysts obtained by atomic laye r deposition show better selective hydrogenation of nitrobenzene to aniline than that of the catalysts obtained by impregnation method proceeds, and the selectivity of the catalyst obtained by the two methods are 100% for the hydrogenation of styrene to et hylbenzene.Pt particles were deposited on different carriers by ALD method with the same cycle number, the carrier effect on the catalytic reaction was studied. The results show that the styrene hydrogenation activity of Pt particles supported on CNTs was significantly higher than the other carriers. In order to further explore the deposition reaction of ALD on CNTs, Fourier transform infrared spectroscopy(FTIR), Raman(Raman), X-ray photoelectron spectroscopy(XPS) were characterized to study the deposition of Pt particles on CNTs. The functional groups and crystal structure on the surface of CNTs have been obviously changed. With the increasing of ALD cycles, metallic Pt atoms have emerged on the surface of Pt nanoparticles which contributes to the higher activity for hydrogenation reaction.