Decalin Ring Opening on Heterogeneous Me/Saponite Nanocatalysts (Me = Rh, Ru, and Ir)

Abstract

Heterogeneous nanocatalysts containing metal nanoparticles (Me = Ir, Rh, and Ru) deposited on mesoporous saponite (magnesium aluminosilicate) were prepared from metal chlorides by the incipient wetness impregnation method and tested in the ring-opening reaction at high pressures using decalin as a substrate. The elemental composition of the catalysts and the carrier, the surface area, pore size and pore volume, the charge state, the size of metal nanoparticles, and the acidity were characterized by the following methods: scanning electron microscopy with energy-dispersive X-ray analysis, nitrogen adsorption–desorption analysis, Fourier-transform infrared spectroscopy, diffuse-reflectance Fourier-transform infrared spectroscopy, transmission electron microscopy, CO chemisorption, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. It was shown that the structure of the carrier and the mesopore system were preserved after metal deposition. Metal particles have an extremely small size and high dispersion. The carrier has a small number of Brønsted acid sites (BAS), which decreases when the metal is supported. The highest BAS/LAS (Lewis acid sites) ratio is determined for the Rh/saponite catalyst. It was found that the activity, selectivity, and product composition were mostly affected by the metal nature. The Ir/saponite catalyst provides a selectivity of about 90% for the ring-opening products, both full and partial ring opening, at the total decalin conversion of about 80%. Over the Rh/saponite catalyst, up to 30% of the bicyclic products of the skeletal isomerization of decalin are formed along with the ring-opening products (mainly partial). The formation of a large number of C1–C9 hydrocracking products is observed over the Ru/saponite catalyst, besides the ring-opening products. Changes in the activity and selectivity of the catalysts with the variation of the main reaction parameters (T, P, WHSV, H2/C10 M ratio, and decalin partial pressure) were also determined.