Selective 1,3-Butadiene hydrogenation by gold nanoparticles deposed&precipitated onto nanocarbon materials

Abstract

Graphene Oxide (GO) and carbon nanotubes (CNT) have been scarcely used as support for Au catalysts if compared to oxidic supports such as Al2O3, CeO2 or TiO2 [1]. However, they can decisively determine the morphology of gold nanoparticles supported on them, and therefore can address the selectivity and catalytic activity of the Au-carbon catalysts. These unique nanostructures were chemically modified and used as support for gold nanoparticles achieving an efficient control of the distribution of Au particle size. In this communication we report comparatively the selectivity and catalytic activity for the hydrogenation 1,3-butadiene of gold nanoparticles deposited on different nanocarbon structures. Our aim is to confirm that the nanostructures of carbon play a decisive role in the catalytic performance for 1,3-butadiene hydrogenation. In order to favor an improved dispersion of Au on nanocarbon supports, CNT [2] and GO were doped with nitrogen, whereas another GO was treated by diazotation. We have used a simple codecomposition method for generating gold nanoparticles (AuNPs) in the presence of suitable nanocarbon structure. The AuNPs were prepared from HAuCl4 precursor. TEM, XRD, TGA, TPD-MS, IR and XPS were used in order to characterize supports and catalysts. The synthesis, structural properties, surface analysis, and results of catalytic activities and selectivities of the catalysts in the hydrogenation have been studied. The presence of nitrogen groups modifies the gold precipitation-deposition process producing different loadings and sizes of gold nanoparticles on these supports. The morphology and size of the Au NPs, as well as of the nanostructured support, seem to affect the selectivity and catalytic activity. The results of 1,3- butadiene hydrogenation clearly indicated that the deposition of Au nanoparticles on carbon surfaces enhances the selectivity towards butenes although butane (fully hydrogenated product) formation is favored thermodynamically.