Influence of surface Sn species and hydrogen interactions on the OH group formation over spherical silica-supported tin oxide catalysts

Abstract

Silica-supported tin oxide catalysts are currently used in chemical processes involving hydrogen. A deeper understanding of the interactions of molecular hydrogen with the catalyst surface is crucial, to gain insights into structure–activity relationships that control the catalytic performance. This work aims to explore the influence of Sn species on silica-supported tin oxide catalysts and in particular the role of OH groups formed during hydrogen exposure. Tin oxide supported on spherical silica nanoparticle (SSP) catalysts was investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The catalysts were synthesized using two different methods, incipient wetness impregnation (IWI-Sn) and incorporation (Inc-Sn) of Sn species to the SSP support with the sol–gel method. In situ DRIFTS showed that new OH groups on the silica surface are formed over SSP-supported tin oxide catalysts during the hydrogen exposure. The Sn–O–Si species play a key role in the formation of new OH groups on the silica surface over the catalysts. These Sn–O–Si species were predominant on the Inc-Sn catalysts, while the IWI-Sn catalyst presented various types of Sn species. Moreover, the Sn–O–Si species increased with the increase of Sn contents in both samples. The analytical results indicate that the newly generated OH groups appeared mostly on the silica surface surrounding the Sn–O–Si species.