| 摘要 |
The present invention is related to a novel procedure for preparing a highly crystalline aluminum hydroxide in a bohemite phase by an aqueous-sol and cold dry method. In the alumina synthesis using the aqueous-sol method, there were used compounds such as: aluminum tri-sec-butoxid, nitric acid and demineralized water. The novel characteristic of the disclosure is that the alkoxy used is dissolved in water at a temperature of 88 degree C, reflux and atmospheric pressure conditions, and the alcohol generated during the reaction is eliminated by evaporation, i.e., alcohol is not used as a solvent in comparison with the sol-gel method, where usually alkoxys are dissolved in ethyl alcohol, propyl alcohol, butyl alcohol and so on. The hydroxide that was obtained by the sol method is cooled at temperatures of -15 degree C and dried with a freeze drying, using the sublimation principle of the solvent upon passing from the solid state to steam without passing by the liquid state. Said hydroxide is calcined under an air stream from about 2 and 6 l/h, at temperatures from about 400 and 600 degree C, thereby generating an alumina crystalline gamma phase. The aforesaid alumina is useful as a support or catalyst in different processes of oil and petrochemical refining. The incorporation of the alumina allows catalysts to substantially raise the activity due to the intrinsic acidity of said materials. Said activity is reflected in an increment of conversion and selectivity of the desired products such as obtaining a higher gasoline yield. Highly crystalline, and homogeneous hydroxides are obtained, having adequate textural properties within the range of mesopores that are suitable for using in any desired process according to the properties of the same.
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