III Oxide Gel

CatalyticaUy active chromium (III) oxide gel has previously been prepared by the slow precipitation of dilute solutions of chromium(III) compounds with dilute ammonia. The resulting highly flocculent precipitate is thoroughly washed, usually by decantation, separated by filtration, and dried. Complete directions are given by Kohlschiitter. The procedure is very tedious (the washing frequently requires a week) and because of the dilute solutions used (0.03 to 0.08 M), the production of catalyst, 

The final, dried product is obtained in the form of shining, vitreous, jet-black particles of the proper size for direct use in experimental -catalytic reactors. The gel exhibits catalytic activity in several diverse reactions, for example, dehydration of silcohols, hydrogenation of olefins, dehydrogenation of paraffins, especially gaseous paraflSns, and aromatization of paraffins containing six or more carbon atoms in a straight chain. The material prepared as described is appreciably more active than that made by 

The normal color of chromivun(III) oxide is green. The observed color of the present preparation probably is due to the presence of a small amount of higher oxide. When employed as a catalyst, this higher oxide can be reduced, prior to adding the charge, by treating the catalyst at reaction temperature with hydrogen for a short time. 

When employed in organic systems at elevated temperatures, all catalysts sooner or later become inactive owing to-the deposition of a carbonaceous residue on the surfaces. The present catalyst is no exception. After exhaustion, it 

Inorganic Syntheses, Volume II Edited by W Conard Femehus 1946 by McGraw-Hill Book Company, Inc. 

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Wet preparation of red iron oxides can involve either a hydrothermal process (see Hydrothermal processing) or a direct precipitation and growth of iron oxide particles on specially prepared nucleating seeds of Fe202- In the hydrothermal process, iron(II) salt is chemically oxidized to iron(III) salt, which is further treated by alkahes to precipitate a hydrated iron(III) oxide gel. The gel can be dehydrated to anhydrous hematite under pressure at a temperature around 150°C. 

Type IV isotherms (e.g. benzene on iron(III) oxide gel at 320 K) level off near the saturation vapour pressure and are considered to reflect capillary condensation in porous solids, the effective pore... 

Carbon tetrafluoride, 1 34 3 178 Carbon tetraiodide, 3 37 Carbonyl azide, formation of, by carbohydrazide, 4 35 Carbonyl fluoride, 6 155 Carbonyls, metal, 2 229 metal, nomenclature of, 2 264 structure of, 2 232 Catalysts, beryllium chloride, 5 25 boron fluoride, 1 23 chromium(III) oxide gel, 2 190... 

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