| Phys. Chem. Chem. Phys., 2007, 9 | |
Additions and corrections Silver as acrolein hydrogenation catalyst: intricate effects of catalyst nature and reactant partial pressures |
Michael Bron, Detre Teschner, Axel Knop-Gericke, Friederike C. Jentoft, Jutta Kröhnert, Jens Hohmeyer, Claudia Volckmar, Bernd Steinhauer, Robert Schlögl and Peter Claus
Phys. Chem. Chem. Phys., 2007, 9, 3559–3569, DOI: 10.1039/b701011g. Amendment published 14th October 2008
In the above paper we reported on the adsorption of H2 (or D2) at 77 K on SiO2 and Ag/SiO2. A shift of the Si–OH vibrations from 3749 to 3716 cm−1, shown in Fig. 9 of the paper and observed for both, SiO2 and Ag/SiO2, was inferred to arise from interaction of H2 (or D2, respectively) with the Si–OH groups. The absence of any bands indicative of the vibrations of adsorbed H2 (or D2) was explained with a, presumably, very symmetric adsorbate complex, which would produce too weak an IR band to be detectable.
Fig. 9 IR spectra of H2 adsorption at liquid nitrogen temperature on Ag/SiO2–P, activated at 450 °C in vacuo.
The spectrum shown in Fig. 9 of the paper actually is representative of the adsorption of N2 on Ag/SiO2 which was present as a contaminant and adsorbed preferentially (thus preventing adsorption of significant amounts of H2). The vibration of adsorbed N2 was obscured through noise in the background (atmospheric CO2 contributions). Fig. I shows the effect of adsorbed N2 on the O–H vibration on the surface of SiO2; the free OH groups are observed 3751 cm−1 and the disturbed OH groups at 3717 cm−1.
Fig. I IR spectra of N2 adsorption at liquid nitrogen temperature on SiO2 after activation at 450 °C in vacuo.
New H2 adsorption experiments (Fig. II) show that the shift of the silanol groups through interaction with H2 is in fact, much smaller, only about 15–18 cm−1. This shift is consistent with earlier reports in the literature.1 A band of adsorbed H2 was also observed, at about 4133 cm−1. The shifted OH vibration and the H2 vibration were more difficult to discern in the spectra of silver-containing samples than in those of silica. As postulated in our original paper, H2 adsorbs on the silanol groups of the support, and the interaction is weak, as indicated by the small red-shift of the silanol vibrations. H2 adsorption on silver could not be observed. All further discussion and conclusions in the original paper thus remain valid.
Fig. II Difference IR spectra of H2 adsorption on SiO2 at liquid nitrogen temperature after activation at 450 °C in vacuo.
1. T. E. Huber and C. A. Huber, J. Phys. Chem., 1990, 94, 2505–2511.
The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.