Interaction of Petroleum-Relevant Organosulfur Compounds with TiO₂(110)

Abstract

The interaction of two sets of structurally related molecules, thiophenol/thioanisole, and thiophene/tetrahydrothiophene, with vacuum-annealed and ion-bombarded TiO(2)(110) surfaces has been studied using a combination of temperature-programmed reaction spectroscopy (TPRS) and X-ray photoelectron spectroscopy (XPS). All thioethers studied were observed to adsorb and desorb from both surfaces without producing reaction products, while thiophenol, the only species studied containing a S-H bond, reacted with both surfaces. Approximately 25% of surface bound thiophenol decomposed over the vacuum-annealed surface. On the bombarded surface, thiophenol both decomposed into surface-bound C(x)H(y)/S fragments, and reacted to form benzene, which desorbed from the surface at 400 K. We propose that phenylthiolate formation on the bombarded surface leads to the observed production of benzene. These results highlight the importance of defects in the reactivity of titania, and lay the foundation for the study of larger, refractory sulfur compounds present in fuel.

In Situ Measurement of CO2 and H2O Adsorption by ZIF-8 Films

“…We infer by analogy to single crystal adsorption studies that this shift is indicative of strengthened interactions between molecules due to decreased intermolecular spacing, increased intermolecular forces, and resulting weakened interactions with the film. 23,24 Such a shift was also observed in other gas adsorption studies involving porous materials. 25,26 The small but broad α 2 desorption peak (∼175 K) was observed at larger exposures with a peak maximum that shifted to higher temperatures with increased exposure.…”

Low-Temperature Adsorption and Diffusion of Methanol in ZIF-8 Nanoparticle Films

“…At higher exposures the peak shifts to 160 K, which is likely due to nucleation in the pores (governed by weaker van der Waals forces) as well as multilayers on the surface. It is likely that the energies of desorption are similar and therefore difficult to distinguish with TPD alone, although as previously mentioned the width of the 160 K peak is slightly broader than that observed on pure Au (S2) and also broader than the previously observed pure surface multilayer peaks of other small molecules on dense surfaces using this experimental setup and identical heating ramp parameters . Finally, we dosed MeOH at 130 K, then collected XPS at 90 K. We cooled the sample to 90 K following exposure at 130 K to minimize any potential differences in the XPS data caused by differences in diffusion.…”

“…It is likely that the energies of desorption are similar and therefore difficult to distinguish with TPD alone, although as previously mentioned the width of the 160 K peak is slightly broader than that observed on pure Au (S2) and also broader than the previously observed pure surface multilayer peaks of other small molecules on dense surfaces using this experimental setup and identical heating ramp parameters. 67 Finally, we dosed MeOH at 130 K, then collected XPS at 90 K. We cooled the sample to 90 K following exposure at 130 K to minimize any potential differences in the XPS data caused by differences in diffusion. The slope of the correlation plot at 130 K (filled red triangles, Figure 4) is greater than that at 90 K, suggesting a greater degree of pore penetration at higher exposure temperature, likely caused by enhanced diffusion into the pores upon exposure.…”

X-ray Photoemission Spectroscopy Investigation of the Interaction between 4-Mercaptopyridine and the Anatase TiO2 Surface

“…The “excess” S atoms detected in sample A can probably be related to the decomposition of sulfide impurities, which can also form in purified 4-MPy solutions , and could therefore be responsible for the higher intensity recorded for doublet i. , Other possible sources of S are either the sulfidization of 4-MPy molecules, which can be promoted, e.g., on the Au(111) surface under particular growth conditions or the cleavage of C–S bonds, observed, e.g., after the UHV adsorption of organosulfur compounds on a strongly defective rutile TiO 2 (110) surface. , Given, respectively, the different substrate reactivity toward sulfur, and the negligible defect density, testified by the absence of reduced Ti species at the surface, it is likely that those mechanisms are not active in our case, and we might expect a negligible degradation of 4-MPy molecules on the surface.…”