SU63479A1 - The method of obtaining the active alumina catalyst - Google Patents

Description

A number of methods for producing active alumina are known. Among them, the most affordable and cheap method is the precipitation of alumina hydrate from aluminate solutions using carbon dioxide.

Obtaining active alumina for catalytic purposes requires special conditions, namely, dilute aluminate races, low precipitation temperatures and high carbon dioxide concentrations are necessary.

The main disadvantage of the process is that alumina is obtained in the form of a powder, while in catalytic processes, as well as during the drying of vapors and gases, it is necessary to have active alumina in the form of pieces.

The production of alumina in the form of pieces by pressing the powder does not give good results, since the obtained pieces have low mechanical strength and, in addition, due to the reduction of the surface, the activity of alumina decreases markedly.

The authors of this invention propose a method for producing active alumina in chunks with high mechanical strength.

This method consists in the precipitation of alumina hydrate from aluminate solutions containing from 60 to 100 g / l of AO3 using carbon dioxide or gases containing it. The precipitation is incomplete, and until the concentration of the radio is at least 20 g / l of AO3 in solution.

The resulting wet cake has TIKCO1 sturdy properties and, upon grinding, turns into a homogeneous creamy mass. This mass, dried at a temperature of 200-300 ° C, loses its ability to disintegrate into water when treated with water or dilute acids.

When treated with water, leaching of the soluble substances in the mass (Na2 CO2, NaHCOs, etc.) occurs, due to which the resulting solid mass acquires a high porosity, reaching 70% of the lumps volume, which makes it possible to use both as a dryer and for catalytic purposes.

To facilitate leaching, it is recommended to dry the alumina hydrate in thin layers. The leaching process can be accelerated by using diluted acids instead of water.

Example. 2l. an aluminate solution with an AUOs content of 63 g / liter is carbonated at a flow rate of 35 l / h per 1 l of the solution to a final concentration of AOOz in the solution of 30 g / l.

The resulting alumina hydrate is aspirated on a suction filter from the mother liquor and grows in a mortar to a creamy consistency. The sludge is dried in steps, first at temperatures of 80-120 ° C and then for three hours at 250 ° C, after which it; crushed into pieces measuring 2-7 mm. The alumina chunks are washed in a flow system with water until slightly alkaline. The obtained alumina, after pre-activation by heating to 350 ° C, has a high porosity of 60% of the volume of the pieces, and, when standing over water in a desiccator, adsorbs it in an amount of 20.5% by weight.

Example 2. A 2 l aluminate solution containing ABOz 80 g / l is precipitated with a gas containing 50i% COa and 50% Na, which is passed at a rate of 80 l / hour to 1 liter of solution. Upon reaching the solution

concentrations of 20 g / l AUOa, the supply of CO2-containing gas is stopped.

The treatment of the precipitate and its substance is carried out analogously to Example 1. The obtained pieces of alumina after batching are subjected to treatment with 10% H2SO4, followed by washing with water until neutral.

After activation of the arpeBaiHweM to 350 ° C, alumina has a high porosity of 70.5% of the volume of the pieces.

When it stands above water in a desiccator, it adsorbs 24.0% of water by weight.

Subject invention

A method of producing an active alumina catalyst using carbon dioxide deposition of alumina from aluminate solutions, characterized in that aluminate solutions containing 60-100 g / l of Ao3 are precipitated with carbon: acid to achieve a concentration not lower than 20 g / l of Ao3 in solution, in order to obtain a catalyst with high mechanical strength.