| 摘要 |
An amorphous mesoporous alumina with a median mesopore diameter by volume of 16 nm or more, a mesopore volume of 0.5 mL/g or more, and a total pore volume of more than 0.75 mL/g. A process for preparing said alumina, comprising:;a) precipitating a basic precursor and an acidic precursor, at least one of which comprises aluminium, at a pH of 8.5 to 10.5, a temperature of 20° C. to 90° C. and for 2 minutes to 30 minutes, with a state of advance of 5% to 13%; b) heating the suspension; c) a second precipitating by adding another basic precursor and acidic precursor, at least one of which comprises aluminium, at a pH of 8.5 to 10.5, a temperature of 40° C. to 90° C. and for 2 to 50 minutes, with a state of advance of 87% to 95%; d) filtration; e) drying; f) shaping; g) heat treatment. |
| 主权项 |
1. A process for preparing an amorphous mesoporous alumina, said process comprising at least the following steps:
a) a first step for precipitating, in an aqueous reaction medium, at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and at least one acidic precursor selected from aluminium sulphate, aluminium chloride, aluminium nitrate, sulphuric acid, hydrochloric acid and nitric acid, in which at least one of the basic or acidic precursors comprises aluminium, the relative flow rate of the acidic and basic precursors being selected so as to obtain a pH of the reaction medium in the range 8.5 to 10.5 and the flow rate of the acidic and basic precursor or precursors containing aluminium being adjusted in order to obtain a state of advance for the first step in the range 5% to 13%, the state of advance being defined as being the proportion of alumina formed, in Al2O3 equivalents, during said first precipitation step with respect to the total quantity of alumina formed at the end of step c) of the preparation process, said step being operated at a temperature in the range 20° C. to 90° C. and for a period in the range 2 minutes to 30 minutes; b) a step for heating the suspension to a temperature in the range 40° C. to 90° C. for a period in the range 7 minutes to 45 minutes; c) a second step for precipitating the suspension obtained at the end of the heating step b) by adding to the suspension at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and at least one acidic precursor selected from aluminium sulphate, aluminium chloride, aluminium nitrate, sulphuric acid, hydrochloric acid and nitric acid, in which at least one of the basic or acidic precursors comprises aluminium, the relative flow rate of the acidic and basic precursors being selected so as to obtain a pH of the reaction medium in the range 8.5 to 10.5 and the flow rate of the acidic and basic precursors containing aluminium being adjusted in order to obtain a state of advance for the second step in the range 87% to 95%, the state of advance being defined as the proportion of alumina formed, in Al2O3 equivalents, during said second precipitation step with respect to the total quantity of alumina formed at the end of step c) of the preparation process, said step being operated at a temperature in the range 40° C. to 90° C. and for a period in the range 2 minutes to 50 minutes; d) a step for filtering the suspension obtained at the end of the second precipitation step c) in order to obtain an alumina gel; e) a step for drying said alumina gel obtained in step d) in order to obtain a powder; f) a step for shaping the powder obtained at the end of step e) in order to obtain a green material; g) a step for heat treating the green material obtained at the end of step f) at a temperature in the range 500° C. to 1000° C., in the presence or otherwise of a stream of air containing up to 60% by volume of water. |
