Conversion of 1,2-Propylene Glycol on Rutile TiO₂(110)

Abstract

We have studied the reactions of 1,2-propylene glycol (1,2-PG), DOCH(CH3)CH2OD, on partially reduced, hydroxylated, and oxidized TiO2(110) surfaces using temperature-programmed desorption. On reduced TiO2(110), propylene, propanal, and acetone are identified as primary carbon-containing products. While the propylene formation channel dominates at low 1,2-PG coverages, all of the above-mentioned products are observed at high coverages. The carbon-containing products are accompanied by the formation of D2O and D2. The observation of only deuterated products shows that the source of hydrogen (D) is from the 1,2-PG hydroxyls. The role of bridging oxygen vacancy (VO) sites was further investigated by titrating them via hydroxylation and oxidation. The results show that hydroxylation does not change the reactivity because the VO sites are regenerated at 500 K, which is a temperature lower than the 1,2-PG product formation temperature. In contrast, surface oxidation causes significant changes in the product distribution, with increased acetone and propanal formation and decreased propylene formation. Additionally, D2 is completely eliminated as an observed product at the expense of D2O formation.

Adsorption of small hydrocarbons on rutile TiO2(110)

“…All experiments were performed in a UHV molecular beam surface scattering apparatus with a base pressure of < 1 × 10 -10 Torr which has been described in more detail in our previous publications [55,56].…”

Conversion of methanol on rutile TiO2 (110) and tungsten oxide clusters: 1. population of defect-dependent thermal reaction pathways

“…11,12 The chemistry of methanol and other alcohols on stoichiometric rutile TiO 2 (110) was already in the focus of several studies, especially by the groups of Henderson and Dohna ´lek. [13][14][15][16][17][18][19][20][21][22][23] In addition, from reports of the group of Madix and our own work it is known that the chemistry of methanol is sensitive to the presence of defects, such as oxygen vacancies or Ti 3+ interstitials. [24][25][26] Therefore, methanol is a perfect probe molecule for testing the conversion in different reaction pathways involving reduced transition metal oxide centers.…”

Dehydrogenative Oxidation of Alcohols Catalyzed by Highly Dispersed Ruthenium Incorporated Titanium Oxide

“…However, after annealing Ru 0.07 TiO 2 at 700 • C, the catalytic activity decreased dramatically (entry 10), and the Lewis acid catalyzed products (o, m, p-benzyltoluenes and dibenzyl ether) were not produced by A-Ru 0.07 TiO 2 in the same reaction conditions. Based on the previous mechanistic studies using the single crystal of TiO 2 (typically rutile (110) surface) in vacuum conditions, the reactivity of alcohol on TiO 2 is strongly dependent on the surface defects of TiO 2 , such as oxygen vacant sites [35][36][37]. Besides the reduction of surface area and the aggregation of Ru into RuO 2 during annealing process, the decrease of the surface defects after annealing at 700 • C might result in the low reactivity of A-Ru 0.07 TiO 2 .…”