5a Molecular Sieve

The 5A Molecular Sieve is a chemical with a specific pore size and adsorption capacity. Its molecular formula is 3/4CaO·1/4Na2O·Al2O3·2SiO2·9/2H2O, and its pore size is about 5A (1A=0.1 nm), that is, about 0.48~0.57nm. It is an alkali metal aluminate, belonging to the calcium type of A-type crystal structure. During use, attention should be paid to avoid direct exposure of the molecular sieve to the air, so as not to affect its adsorption performance. The regeneration process of 5A molecular sieves usually involves the removal of adsorbed molecules, such as by heating or using desorption agents. 5A molecular sieve is a kind of chemical substance with excellent adsorption properties and a wide range of applications, which plays an important role in natural gas treatment, gas separation, petroleum processing and other fields.

First, the main characteristics

Adsorption: 5A molecular sieve can adsorb any molecule with a diameter smaller than its pore size, especially with the characteristics of high selective adsorption and fast adsorption speed, especially suitable for pressure swing adsorption.

Stability: Soluble in strong acids or alkalis and decompose, but insoluble in water and organic solvents. It is hygroscopic and needs to avoid direct contact with water, acid and alkali when stored.

Physical form: usually in a strip or ball shape, the diameter range can be adjusted according to different application requirements, such as 1.51.7mm, 3.03.3mm, 2.03.0mm, 3.05.0mm, etc.

Main uses

Natural gas treatment: used for natural gas drying, desulfurization, carbon dioxide removal, improve the purity of natural gas.

Gas separation: It plays an important role in the process of nitrogen oxygen separation and nitrogen hydrogen separation, and can produce high purity oxygen, nitrogen and hydrogen.

Petroleum processing: used for petroleum dewaxing, separation of normal hydrocarbons from branched hydrocarbons and cyclic hydrocarbons, improve the quality of petroleum products.

Pressure swing adsorption: Adapt to various sizes of oxygen, hydrogen, carbon dioxide and other gas pressure swing adsorption device, is an important material in the pressure swing adsorption industry.

Air purification: It can be used for air purification to remove impurities such as water and carbon dioxide.

Iii. Preparation of 5A molecular sieve

There are several main methods for the preparation of 5A molecular sieve:

1. Traditional preparation method

Traditionally, the preparation of 5A molecular sieves involves a series of complex chemical reactions and physical processing steps, as follows:

Raw material mixing: water glass, sodium metaaluminate, sodium hydroxide and other raw materials are mixed according to a certain molar ratio (such as Al2O3:SiO2:Na2O:H2O=1:2:3:185), usually under the condition of temperature control above 40℃ for strong stirring to promote the reaction.

Gel formation and crystallization: The gel generated by the reaction is statically crystallized at a temperature of 102 ° C ±2 ° C, so that the gel is gradually transformed into a crystal with molecular sieve structure.

Ion exchange: After filtration and washing, calcium chloride is added for ion exchange, this step is to replace some sodium ions in the crystal with calcium ions, so as to obtain 5A molecular sieve. The degree of exchange of ion exchange is usually 70%.

Forming and activation: After filtration, washing, drying, adding adhesive kneading, forming, and finally burning activation to prepare 5A molecular sieve. The purpose of burning activation is to further improve the adsorption performance and stability of molecular sieve.

2. Other preparation methods

In addition to traditional preparation methods, there are other methods used to prepare 5A molecular sieves, such as:

In situ synthesis method: molecular sieve 5A was prepared from other chemical substances based on silica-aluminum skeleton. The specific method is to mix the silica-aluminum skeleton with an aqueous solution containing crystal seeds and alkaline substances, heat to the appropriate temperature and stand, and finally place it in the oven to dry. This method can directly synthesize 5A molecular sieves under specific conditions without subsequent complex ion exchange and molding steps.

Hydrothermal conversion method: First prepare a other form of molecular sieve (such as 4A molecular sieve), and then put it in sodium nitrate (NaNO3) aqueous solution, after a certain time of heating reaction, pickling and washing, and finally get molecular sieve 5A. This method takes advantage of the transformation relationship between molecular sieves and achieves the transformation of molecular sieves type through a simple chemical reaction.

Binder free preparation method: A novel 5A molecular sieve adsorbent preparation method, including NaA molecular sieve powder and CaO powder with particle size less than 50μm according to a certain proportion of evenly mixed, mixed with water and formed after drying, roasting, washing and activation steps. The adsorbent prepared by this method does not require the addition of binders, so it has a higher adsorption capacity and mass transfer rate, and has better compressive resistance.