Chromia-alumina catalyst isotherms

Chromia-alumina catalysts are often prepared by procedures other than the method of impregnation. A precipitated chromia was prepared as follows y-alumina was suspended in 25 per cent ammonium hydroxide solution. The mixture was stirred rapidly while chromic nitrate solution was added from a buret. The resulting mixture was then dried, ignited, and reduced in the same manner as for impregnated samples. A total of four samples was prepared. The susceptibility isotherm for this series is of the same general form as for the impregnation series except that point I is virtually absent. But the most striking... 

Experiments have also been made on alumina samples of different areas. For instance, an impregnated chromia catalyst on a sample of boehmite, the specific area of which as 170 square meters per gram gave a susceptibility isotherm almost identical in form with that on high-area 7-alumina. Point I occurred at the same concentration, namely 6 per cent chromium by weight. This surprising result is understandable... 

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