Adsorption and Reactivity of 2,3-Dihydrofuran and 2,5-Dihydrofuran on Pd(111): Influence of the C═C Position on the Reactivity of Cyclic Ethers

Abstract

High-resolution electron energy loss spectroscopy (HREELS) and temperature-programmed desorption (TPD) were used to study the adsorption and thermal chemistry of 2,3-dihydrofuran (2,3-DHF) and 2,5-dihydrofuran (2,5-DHF) on Pd(111). The results, paired with earlier computational results, indicate that 2,3-DHF and 2,5-DHF both adsorb on Pd(111) primarily via their respective olefin functional groups at low temperature (<170 K). Both molecules undergo dehydrogenation by 248 K to form species that produce furan in a reaction limited process above 300 K. The furan-producing intermediate intermediate can also undergo decomposition to form C(3)H(x) and CO. In addition, benzene resulting from C-C coupling reactions is detected on the surface and as a desorption product from both species, at about 520 K. A key difference between the two species is that 2,3-DHF can be hydrogenated to produce tetrahydrofuran at about 330 K, whereas 2,5-DHF is more likely to dehydrogenate, producing furan in an additional low-temperature channel at approximately 320 K. The results point to the importance of the position of the olefin functional group in relation to the ether function in determining the reactivity of cyclic oxygenates.

Deuterium‐Labeling Study of the Hydrogenation of 2‐Methylfuran and 2,5‐Dimethylfuran over Carbon‐Supported Noble Metal Catalysts

“…At low temperatures, ring opening is slow,w hich makes THF the major product. These theoretical results appear to be in agreement with the experimentalr esults of Horiuchi and Medlin, [16] who investigatedt he adsorption and hydrogenation behavior of 2,3-and 2,5-dihydrofuran on Pd(111). At temperatures below approximately 330 8C, 2,3-dihydrofuranw as hydrogenated to THF,w hereas 2,5-dihydrofuran underwent dehydrogenation to furan.…”

Directing reaction pathways by catalyst active-site selection using self-assembled monolayers

“…The appearance of the broad C-H-stretching peaks between B2,800 and 3,000 cm À 1 on the uncoated catalyst indicated the production of decomposition intermediates bound to the catalyst. Single-crystal and density functional theory studies of furanic species on Pd(111) have attributed stretches in this range to a combination of CH and CH 2 containing fragments from adsorption of the furan ring and decomposition to surface hydrocarbon species 7,30,31 . The appearance of CH 2 stretches, not present in the parent furfural molecule, may be attributed to reaction of the adsorbed furan ring with surface hydrogen atoms produced from decomposition of neighbouring adsorbates.…”

Effects of van der Waals density functional corrections on trends in furfural adsorption and hydrogenation on close-packed transition metal surfaces

“…In this context, a model reaction that has received significant attention is the hydrogenation of furfural to furfuryl alcohol [1][2][3][4][5][6][7][8]. In spite of a substantial amount of study, however, furfural hydrogenation catalysts, most of which are based on transition metals or metal alloys, are still incompletely understood, and the hydrogenation process remains the subject of a significant amount research [2,7,[9][10][11]. As is the case for numerous other hydrogenation chemistries, such as the selective hydrogenation of acetylene [12], the key catalytic imperative is to maintain a balanced reaction activity and selectivity.…”