CN111203212A - Load forming method of noble metal catalyst - Google Patents

Abstract

The invention discloses a load forming method of a noble metal catalyst, which comprises the following steps: a. slowly adding the noble metal solution to the powder according to the volume of 1.2-2.0 times of the alumina or the rare earth, directly stirring and mixing to form slurry, and enabling the pH value of the slurry to be 7.0-9.0; b. adding other auxiliary agents, and continuously adding inorganic or organic alkali to adjust the pH value to 7.0-9.0; c. then adding an alkaline binder, wherein the pH value of the final slurry is 7.0-9.0; d. and drying the slurry. According to the load forming method of the noble metal catalyst, an excessive impregnation method is adopted for loading, dust and noble metal loss cannot be caused in the technical process, meanwhile, an alkaline slurry system is kept in the whole technical process, the noble metal can be precipitated and anchored, the migration phenomenon of the noble metal is avoided, the noble metal is dispersed more uniformly, and the catalytic activity is better.

Description

Load forming method of noble metal catalyst

Technical Field

The invention relates to a load forming method of a noble metal catalyst.

Background

In both motor vehicle exhaust purification and industrial VOC exhaust purification processes, a purification carrier is used in which a noble metal catalyst is coated. When in use, the activity of the noble metal catalyst is utilized to lead the harmful gas to be oxidized or reduced and converted into the harmless gas, thereby achieving the purpose of gas purification.

Tests show that different loading technologies of the noble metal catalyst have great influence on the surface composition, the surface structure, the catalytic activity and the high-temperature sintering resistance of the catalyst.

Here, the existing noble metal catalyst loading method generally selects an isochoric impregnation method, and the loading method has the following three processes:

the process 1 is that the noble metal solution is loaded on the powder according to the volume of the alumina or the rare earth and the same volume, then the powder is dried and sintered, and other auxiliary agents and caking agents are added to prepare the acid slurry. The material state obtained after the noble metal solution is loaded on the powder is still acidic powder, so that powder dust emission loss exists in the loading process, noble metal ions are in a free state in an acidic system, the drying and sintering process is complex, noble metal still migrates in the drying process, the noble metal loading is finally uneven, noble metal aggregation is easily caused, and the dispersity of the noble metal is poor.

And 2, loading the noble metal solution on the powder in an equal volume according to the volume of the aluminum oxide or the rare earth, directly adding other auxiliary agents and binders to form acidic slurry, and finally drying the slurry. In the above process, the substance obtained after the noble metal solution is loaded on the powder still has acidic powder, the powder dust emission loss also exists in the loading process, noble metal ions in the acidic slurry system are in a free state, and the noble metal still has a migration phenomenon in the slurry drying process, so that the noble metal loading is uneven, the noble metal is easy to aggregate, and the dispersion degree of the noble metal is poor.

And 3, preparing the alumina, the rare earth, the auxiliary agent and the binder into acidic slurry, adding the noble metal solution, and finally drying. The process has no dust emission loss of the loaded powder, but the loaded powder is still an acidic slurry system finally, noble metal ions in the acidic slurry system are in a free state, and an obvious migration phenomenon still exists in the slurry drying process, so that the noble metal is unevenly loaded, noble metal aggregation is easily caused, and the dispersity of the noble metal is poor.

Disclosure of Invention

Aiming at the problems, the invention designs a load forming method of a noble metal catalyst, which adopts an excessive impregnation method for loading, does not cause dust and noble metal loss in the technical process, simultaneously keeps an alkaline slurry system in the whole technical process, can precipitate and anchor noble metals, avoids the migration phenomenon of the noble metals, and ensures that the noble metals are dispersed more uniformly and have better catalytic activity.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for carrying and forming a noble metal catalyst is characterized by comprising the following steps:

a. slowly adding the noble metal solution to the powder according to the volume of 1.2-2.0 times of the alumina or the rare earth, directly stirring and mixing to form slurry, and then adding inorganic or organic alkali to ensure that the pH value of the slurry is 7.0-9.0;

b. adding other auxiliary agents, and continuously adding inorganic or organic alkali to adjust the pH value to 7.0-9.0;

c. then adding an alkaline binder, wherein the pH value of the final slurry is 7.0-9.0;

d. and drying the slurry.

The method adopts an excess impregnation method for loading, the noble metal solution is slowly added onto the powder according to the volume of 1.2-2.0 times of the volume of the alumina or the rare earth, and slurry is obtained by stirring and mixing.

In addition, the slurry in the steps a, b and c is kept at the pH value of 7.0-9.0, namely, the slurry is always maintained in an alkaline slurry system, so that noble metal ions and OH radicals can be combined to precipitate and anchor, the migration phenomenon of noble metals in the drying process is avoided, the noble metals can be dispersed more uniformly, and the catalytic activity is better.

Detailed Description

A method for carrying and forming a noble metal catalyst comprises the following steps:

a. the noble metal solution is slowly added to the powder according to the volume of 1.2-2.0 times of the volume of the alumina or the rare earth, and the mixture is directly stirred and mixed to form slurry, and compared with the slurry obtained by the existing solution impregnation method, the obtained slurry does not cause dust and noble metal loss in the loading process. Subsequently, an inorganic or organic base is added so that the pH of the slurry is in the range of 7.0 to 9.0, the base acting to perform a neutralization reaction which binds the noble metal ions to OH groups to form a precipitate which is anchored and maintains the slurry in an alkaline environment.

b. Adding other auxiliary agents, and continuously adding inorganic or organic alkali to adjust the pH value to 7.0-9.0. The continuous addition of alkali will maintain the obtained slurry in an alkaline environment to ensure that the precious metals are still maintained in a precipitate state and avoid being converted into a free ionic state again due to acidification.

c. Then adding an alkaline binder, wherein the pH value of the final slurry is 7.0-9.0;

d. and drying the slurry.

In conclusion, the invention adopts an excess impregnation method for loading to eliminate raise dust and noble metal loss, simultaneously, slurry is kept in an alkaline system in the whole process to ensure that noble metal ions are always combined with OH radicals to precipitate, separate and anchor, noble metal migration in the drying process is avoided, the noble metal is dispersed more uniformly, noble metal aggregation is avoided, and the catalytic activity is better.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change or modification made to the above embodiments according to the technical principle of the present invention still falls within the scope of the technical solution of the present invention.

Claims (1)

1. A method for carrying and forming a noble metal catalyst is characterized by comprising the following steps:

a. slowly adding the noble metal solution to the powder according to the volume of 1.2-2.0 times of the alumina or the rare earth, directly stirring and mixing to form slurry, and then adding inorganic or organic alkali to ensure that the pH value of the slurry is 7.0-9.0;

b. adding other auxiliary agents, and continuously adding inorganic or organic alkali to adjust the pH value to 7.0-9.0;

c. then adding an alkaline binder, wherein the pH value of the final slurry is 7.0-9.0;

d. and drying the slurry.