Coordination and reaction mechanism of furan on Ru(001)

Abstract

The surface chemistry of furan adsorbed on Ru(001) at 80 K has been explored using thermal desorption spectroscopy, x-ray and ultraviolet photoelectron spectroscopies and high resolution electron energy loss spectroscopy (HREELS). Furan adsorption follows a three-dimensional island growth mode. Three desorption peaks, corresponding to multilayer, second layer, and monolayer were identified at 117, 142 and 220 K, respectively. Monolayer species strongly bind to the surface, showing a much lower O(1s) binding energy (532.9 eV) as compared to the physisorbed furan (534.8 eV). HREELS reveals that within the monolayer, there are two different chemisorbed species with molecular rings oriented either tilted or parallel to the surface. By annealing the surface to 180 K, the parallel furan π complex undergoes α-C electrophilic addition and H elimination, forming the tilted α-furyl species and Ru–H. The α-furyl can either recombine with hydrogen to form furan desorbing between 180 and 250 K, or decompose to give adsorbed oxygen atoms and a metallocyclelike intermediate through a direct oxygen abstraction mechanism. Further thermal annealing leads to the formation of carbon monoxide and hydrogen desorbing from the surface.

Selective conversion of furfuryl alcohol to 1,2-pentanediol over a Ru/MnOx catalyst in aqueous phase

“…This parallel adsorbed FFA on a Pd surface may be rapidly undergoing the hydrogenation of the CvC bond to generate THFA in the presence of active hydrogen species. However, the results from high resolution electron energy loss spectroscopy (HREELS) 39 revealed that, besides the parallel adsorbed species, there is also a tilted adsorbed species from furan bonding with one of its α-C to the surface of Ru(001). Similar tilted species might relate to the generation of 1,2-PeD.…”

“…On the other side, the initial adsorption structure of FFA may be changed with the temperature and modify the production selectivity. Xu et al 39 have found that the parallel adsorbed species of furan over the Ru(001) surface can be transformed to the tilted species with the increasing of the temperature. The tilted species of furan ring of FFA are probably undergoing partial hydrogenation to generate A1 (Scheme 2), which might be an intermediate in the production of 1,2-PeD.…”

Acetaldehyde reactions over the uranium oxide system

“…We preferred to study acetaldehyde for two reasons. First, it reacts to give a high yield of furan on β-UO 3 [21]; furan is a desired product that enters into a wide variety of chemical compounds [24,25]. Second, acetaldehyde is an intermediate molecule that can be easily oxidized or reduced depending on the environment; this is one of the main reasons why acetaldehyde has been studied by several workers over a large number of surfaces including Ru (001) [26], Ag (111) [27], Pt(S)-[6(111) × (100)] [28], Pd (111) [29], Rh (111) [30], SrTiO 3 (100) [31] and TiO 2 (001) [32] single crystals, and SiO 2 [33,34], TiO 2 [32,35], and CeO 2 [36] powders.…”

Mechanisms of hydrocarbon conversion reactions on heterogeneous catalysts: analogies with organometallic chemistry

“…For instance, benzylic hydrogens are typically removed first in substituted benzenes [103,104]. In the case of heterocyclic aromatic molecules such as thiophene [105][106][107] and furan [108], the alpha positions (the carbon adjacent to the heteroatom) are typically the most reactive. This latter regioselectivity may explain the origin of some of the main products obtained during the hydrodesulfurization (HDS) and hydrotreating of crude oil [109].…”