Preparation Method Of Catalyst

Every method of making a catalyst is actually a combination of a series of operating units. For convenience, the name of the key and characteristic operating unit is set as the name of the manufacturing method. The traditional methods include mechanical mixing method, precipitation method, impregnation method, solution evaporation method, hot melting method, soaking method (leaching method), ion exchange method, etc. The new methods developed now include chemical bonding method, fibrillation method, etc. .

1. Mechanical mixing method

Add two or more substances into the mixing device and mix. This method is simple and easy to implement, such as the manufacture of conversion-absorption type desulfurizer, which is to measure the powder of active components (such as manganese dioxide, zinc oxide, zinc carbonate) and a small amount of binder (such as magnesium oxide, calcium oxide). Continuously add it to a turntable with adjustable rotation speed and inclination, and at the same time spray a metered amount of water and powder to roll, mix and bond to form a sphere with a uniform diameter.

2. Precipitation

This method is used to make catalysts that require a high degree of dispersion and contain one or more metal oxides. In the manufacture of multi-component catalysts, suitable precipitation conditions are very important to ensure the uniformity of product composition and to manufacture high-quality catalysts. The usual method is to add a precipitant (such as sodium carbonate, calcium hydroxide) to one or more metal salt solutions, and to obtain the final product after precipitation, washing, filtration, drying, molding, roasting (or activation).

3. Dipping method

A carrier with high porosity (such as diatomaceous earth, alumina, activated carbon, etc.) is immersed in a solution containing one or more metal ions, and the solution is kept at a certain temperature, and the solution enters the pores of the carrier. The carrier is drained, dried and calcined, and a layer of desired solid metal oxide or its salts is attached to the inner surface of the carrier.

4. spray drying

It is used to make catalysts for fluidized beds with particle diameters ranging from tens of microns to hundreds of microns. For example, in the production of meta-xylene fluidized bed ammoxidation to meta-dicarbonitrile catalyst, firstly, a given concentration and volume of metavanadate and chromium salt aqueous solution are fully mixed, and then mixed with quantitatively freshly prepared silica gel, pumped into In the spray dryer, after being atomized by the nozzle, the water evaporates to dryness under the action of the hot air flow, and the material forms a microsphere catalyst, which is continuously drawn from the bottom of the spray dryer.

5. hot melt method

The hot-melting method is a special method for preparing certain catalysts, which is suitable for a small number of catalysts that have to go through the smelting process. The purpose is to smelt the components under high temperature conditions and call it a uniformly distributed mixture. With the necessary subsequent processing, it can be obtained. Excellent catalyst.

6. Immersion method

From the multi-component system, a suitable liquid agent (or water) is used to extract part of the substance to make a catalyst with a porous structure. For example, in the manufacture of skeleton nickel catalyst, a certain amount of nickel and aluminum are melted in an electric furnace, and the molten material is cooled to form an alloy. The alloy is broken into small particles, soaked in sodium hydroxide aqueous solution, and most of the aluminum is dissolved (to generate sodium metaaluminate). ), i.e. the formation of a porous highly active framework nickel.

7. ion exchange method

The metal cations (eg Na) of certain crystalline substances (eg synthetic zeolite molecular sieves) can be exchanged with other cations. Put it into a solution containing ions of other metals (such as rare earth elements and some noble metals), and exchange other metal ions with Na under controlled concentration, temperature, and pH conditions.