Synthesis and Decomposition of Formate on a Cu/SiO2 Catalyst: Comparison to Cu(111)

Yatsu, T.; Nishimura, Hirokazu; Fujitani, Tadahiro; Nakamura, Junji

doi:10.1006/jcat.2000.2810

Cited by 29 publications

(42 citation statements)

References 28 publications

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“…These results indicate clearly that reduction in high pressure hydrogen/deuterium does not contribute significantly to the decay rate of bidentate copper formate on Cu/SiO 2 . Previous results have indicated a significant role for a hydrogenation channel in the reaction of surface-adsorbed formate on Cu (100) [11], Cu [111], Cu [110] as well as Cu/SiO 2 catalysts [16][17][18], in contrast to the present results. The presence or absence of the hydrogen effect is discussed further below.…”

Section: Kinetics At Steady Statecontrasting

confidence: 85%

“…Previous studies of formate coverage on Cu/SiO 2 versus temperature have been performed by Nakamura and coworkers [16][17][18] at one atmosphere pressure, wherein the coverages were quantified by desorption of CO 2 product after reaction. Here we extend measurements of formate coverage to 6 bar total pressure conditions in both D 2 / 12 CO 2 and H 2 / 12 CO 2 atmospheres.…”

Section: Ftir Results At Steady Statementioning

confidence: 99%

“…A silica support was chosen because previous IR studies have shown minimal support-bound species on silica and no evidence of copper metal-support interactions [16]. Prior to use, the catalyst was calcined in zero air overnight at 623 K, and then reduced within the reactor with pure H 2 (2.5 bar) at 553 K. XPS analysis of the catalyst before and after use revealed primarily Si, O, Cu features ([98%).…”

Section: Methodsmentioning

confidence: 99%

“…As a result, traditional surface analysis using elementary step by step investigations in ultra high vacuum can provide only limited information. Other studies have addressed surface formate reactivity on supported copper catalysts [16][17][18]. These studies have also observed the presence of surface-bound formate species under reaction conditions [16] and also have measured the stability of these species in inert gas and hydrogen [17,18].…”

Section: Introductionmentioning

confidence: 97%

“…Other studies have addressed surface formate reactivity on supported copper catalysts [16][17][18]. These studies have also observed the presence of surface-bound formate species under reaction conditions [16] and also have measured the stability of these species in inert gas and hydrogen [17,18]. Compared with single crystal copper surfaces, the surface species observed on the oxide supported polycrystalline copper system are more complex because of the multi-faceted copper surfaces presented by the supported particles [14,17,[19][20][21] and the presence of species adsorbed on the support materials (e.g., alumina and ceria) as well as the support-metal interface [22].…”

Section: Introductionmentioning

confidence: 99%

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Isotope Effects in Methanol Synthesis and the Reactivity of Copper Formates on a Cu/SiO2 Catalyst

et al. 2008

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Here we investigate isotope effects on the catalytic methanol synthesis reaction and the reactivity of copper-bound formate species in CO 2 -H 2 atmospheres on Cu/SiO 2 catalysts by simultaneous IR and MS measurements, both steady-state and transient. Studies of isotopic variants (H/D, 12 C/ 13 C) reveal that bidentate formate dominates the copper surface at steady state. The steadystate formate coverages of HCOO (in 6 bar 3:1 H 2 :CO 2 ) and DCOO (in D 2 :CO 2 ) are similar and the steady-state formate coverages in both systems decrease by *80% from 350 K to 550 K. Over the temperature range 413 K-553 K, the steady-state methanol synthesis rate shows a weak H/D isotope effect (1.05 ± 0.05) with somewhat higher activation energies in H 2 :CO 2 (79 kJ/mole) than D 2 :CO 2 (71 kJ/mole) over the range 473 K-553 K. The reverse water gas shift (RWGS) rates are higher than methanol synthesis and also shows a weak positive H/D isotope effect with higher activation energy for H 2 /CO 2 than D 2 /CO 2 (108 vs. and 102 kJ/mole) The reactivity of the resulting formate species in 6 bar H 2 , 6 bar D 2 and 6 bar Ar is strongly dominated by decomposition back to CO 2 and H 2 . H 2 and D 2 exposure compared to Ar do not enhance the formate decomposition rate. The decomposition profiles on the supported catalyst deviate from first order decay, indicating distributed surface reactivity. The average decomposition rates are similar to values previously reported on single crystals. The average activation energies for formate decomposition are 90 ± 17 kJ/mole for HCOO and 119 ± 11 kJ/mole for DCOO. By contrast to the catalytic reaction rates, the formate decomposition rate shows a strong H/D kinetic isotope effect (H/D *8 at 413 K), similar to previously observed values on Cu(110).

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