J. Phys. Chem. 1983, 87, 1529-1534
duced active sites, although the latter sites are acidic. The evacuation changed the color of TiOz from white to gray, indicating the formation of F centers according to the defect of lattice oxygen." However, oxygen treatment at room temperature hardly influenced the activity, ruling this out as a major contribution. The reaction scheme of the reduction with hydrogen and decomposition of nitric oxide on CoTPP/Ti02 evacuated at 200 OC can be illustrated as shown in Figure 5. The reduction scheme essentially shows the activations of both nitric oxide and hydrogen which are performed on the central metal ion and the porphyrin ring, respectively. The reaction kinetics suggest the dissociative adsorption of hydrogen%and Rideal-type participation of a second nitric oxide, although one nitric oxide was firmly adsorbed on the catalyst. The decomposition scheme illustrates the oxidation of the complex by nitric oxide. However, the spillover of the oxygen atom left on the central metal ion onto the supporting titanium dioxide which eventually provides the (23) Peri, J. B. J . Phys. Chem. 1965, 69, 211, 220. (24) Meyer, W. 2. Tech. Phys. 1935, 16, 355. (25) Mochida, I.; Fujitau, H.; Takeshita, K.; Tsuji, K. R o c . Int. Congr. Catal., 7th 1980, F16.
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adsorption site for oxygen may allow the extra extent of the reaction beyond the stoichiometry of the cobalt ions. When the support is saturated by oxygen, the decomposition reaction may stop. It is another interesting feature of the complex-upport interaction. Removing the oxygen left a t 200 "C can regenerate the decomposition activity of CoTPP/Ti02. The reaction scheme of the reaction with carbon monoxide appears different from that with hydrogen in terms of their activation. The reaction orders and adsorption amounts suggest that nitric oxide and carbon monoxide are adsorbed commonly on the central metal ion of the complex, but the former much more strongly. The very great reactivity of carbon monoxide in comparison with hydrogen indicates that the adsorbed species is very much activated to attract the oxygen atom from nitric oxide which has itself been adsorbed in the activated bent form. The partially reduced cobalt ion on Ti02 may enrich the valence electrons of the carbon atom of the carbon monoxide through the back-donation to its K* orbital.
Acknowledgment. We are grateful to Dr. Yokoyama, Mitsubishi Heavy Industry, for his ESCA measurement. Registry No. CoTPP, 14172-90-8; TiOz, 13463-67-7; NO, 10102-43-9; Hz,1333-74-0; CO, 630-08-0; N20, 10024-97-2.
Preferentlal Physisorptlon of Orthohydrogen over Parahydrogen by Sodium Mordenite at 77 and 90 K. The Role of Molecular Quadrupole-Field Gradient Interaction for the Hindered Rotation of Sorbed Hydrogen Shoro Furuyama' and Hitoshl Inoue Department of Chemlstw Facuw of Science, Okayama Univers/!y, Okayama 700, Japan (Received: July 9, 1982; I n Final Form: November 23, 1982)
The sorption of H2by iron-free (
