Doctoral Thesis Cover Page — page 36: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

200 L. H. REYERSON AND L. E. SWEARINGEN This accounts for the strange shape of the curve for the copper catalyst at 400° as shown in Fig. 1. The first measurements were made on a fresh cata- lyst and the first three points are those taken successively at about the same rate of flow. After reaching an equilibrium state of oxidation the catalyst behaved just as the platinum and palladium catalysts. In order to account for the rather large amount of CO» produced initially at 360° in the case of the silver catalyst one has to assume that the silver was acting as an oxidizing catalyst prior to being oxidized itself or else there was some adsorbed CO» in the catalyst. This does not seem reasonable because there was none found at 200° where adsorption should be better than at 360°. The instability of silver oxide at eee cenie tS accounts for the fact that more oxygen was removed at 200° In the case of tae platinized gel no such removal of oxygen was observed in the initial stages of reaction. The reaction seems to quickly reach an equilibrium state. Furthermore, the rate of streaming does not have much effect on the efficiency of the reaction as long as the methane is in excess. The reaction becomes measurable at about 240°. Small increases in oxygen content produce increases in the amount of oxidation. This does not hold over the total range of concentrations because an excess of oxygen does not produce complete oxidation. In fact the catalyst is less sufficient when the oxygen content is high than when it is low. For example a change from twenty to twenty-eight percent in the oxygen content of the gas sample in- creased the amount of methane oxidized from about twelve percent to more than nineteen percent. On the other hand an oxygen content of seventy-three percent only gives an oxidation of eight percent and the efficiency of the cata- lyst falls off rapidly as the rate of gas flow increases. As in other catalytic studies there is apparently a definite concentration ratio of oxygen to methane which will produce the best results. These experiments also indicate that the methane must reach the catalyst surface before it is oxidized. In the case of the palladium catalyst the reaction does not become meas- urable until 330° or nearly 100° above that at which the platinized gel causes oxidation. The same general results were obtained for the palladium catalyst as for the platinum except that the palladium was less efficient at a given temperature Table IV shows that increases in the oxygen content at low con- centrations of oxygen causes more reaction while oxygen in excess leads to lessened reaction. The difference in the efficiency between the platinum and palladium may be due to the fact that the platinized gel is a slightly better adsorbent of oxygen. This is shown in the adsorption studies! on these gels. ‘ Summary 1. With the exception of the silver catalyst the metallized silica gels have been shown to act catalytically in the oxidation of methane. They promote the complete oxidation of methane, yielding carbon dioxide and water. No partial oxidation products were found. * Reyerson and Swearingen: J. Phys. Chem., 31, 88 (1927). (C(O) AN) | 6)(0)(0) @ (C(O)