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This paper deals with the adsorption and temperature-programmed reaction spectroscopy of (i) formaldehyde on polycrystalline copper, polycrystalline zinc oxide and (ii) methanol on a copper/zinc oxide/alumina (60:30:10) catalyst. It shows that the energetics of formate hydrogenation/ hydrogenolysis on the copper component of the catalyst, which is the rate-determining step in methanol synthesis on the copper/zinc oxide/alumina catalyst, is unaffected by the intimate mixing of copper and zinc oxide in the catalyst. The coverages of the individual components of the copper/zinc oxide/alumina catalyst which had been producing methanol at a rate of 1.9 x 10−9 mol−1 s−1 g−1 from a carbon dioxide/hydrogen feed (10% CO2, 1 bar, 500 K, 36 liters h−1) by oxygen, hydrogen, and formate species was determined by carbon monoxide titration and by temperatureprogrammed desorption. The copper component of the catalyst was covered with oxygen to between 3.5 x 1014 and 3.9 x 1014 atoms cm−2 (i.e., between 70 and 78% of saturation). Coexisting with this on the copper component of the catalyst was a formate species, the upper limit of its coverage being 2.6 x 1014 molecules cm−2. The zinc oxide component of the catalyst appeared to be hydrided or to contain interstitial hydrogen to a value greater than monolayer coverage during Steady-state reaction. |
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