Brent M. Wedding

Poisoning by SOx of some base metal oxide auto exhaust catalysts

Abstract Many base metal oxide catalysts used for carbon monoxide and hydrocarbon oxidation in automobile exhaust gas are poisoned by sulfur oxides. A study was made of SO x interaction with several catalysts (copper chromite, copper oxide, cobalt oxide, and commercial copper chromite containing copper oxide) to determine its effect on catalytic activity. Various techniques were used in concert and included infrared spectroscopy, thermogravimetric analysis, differential scanning ealorimetry as a measure of catalytic activity, and chemical analysis. The catalytic activity was determined as a function of the amount of SO 2 adsorption at various temperatures, and the specific surface sites were identified. The results indicated that there are at least two different adsorption sites for SO 2 on copper chromite; the SO 2 adsorbs preferentially on the site most important for CO oxidation; the sites necessary for hydrocarbon oxidation being less affected. No sulfate ions form on stoichiometric copper chromite, in contrast to the other catalysts studied. The extent of regeneration of poisoned catalysts depends on the catalyst composition, and several regeneration methods are discussed.

Photometric Study of the Oxygen Diffusivity in an Aluminosilicate Glass

The diffusivity of oxygen in an aluminosilicate glass from 630° to 830°C is derived from optical transmission measurements, wherein the rate of bleaching of Ti3+ color centers by the diffusing oxygen at temperature was measured. The finite‐thickness solution to the heat equation is used to interpret the data; the oxygen diffusivity on this temperature range can be represented by D=28.4 exp (−39.6±3.4 kcal/RT)cm1/sec. It is concluded that the oxygen diffuses interstitially as molecular oxygen, because the activation energy is smaller than the energy to split an Si–O bond: 50 kcal/mole. As a check on the technique and results, penetration measurements were made on a moving color boundary, with identical results.

Optical properties of chemically reduced photochromic glasses

Photochromic glasses subjected to reducing treatments at elevated temperatures develop a colored layer through the reduction of the silver halide phase. The nature of this process is investigated with respect to the temperature and time of the reduction treatment. An explanation of the color development is offered based on the comparison to an alternate way of producing the reduced silver absorption. In addition, the optical bleaching that is observed is discussed and a mechanism is proposed.