What is molecular sieve material?

Also known as zeolite catalysts, these are catalysts in which molecular sieves serve as the catalytically active component or one of the main active components. The most widely used in industry are molecular sieve cracking catalysts, which belong to the category of solid acid catalysts. In addition, metal-supported molecular sieve catalysts with dual catalytic functions are also commonly used, such as palladium-ultra-stable Y-type molecular sieve hydrocracking catalysts. Catalytic properties Based on the catalytic properties of molecular sieves, they can be classified into three categories: molecular sieve solid acid catalysts, metal-molecular sieve bifunctional catalysts, and molecular sieve selective catalysts. Classified by the type of molecular sieve, the classification of molecular sieve catalysts is the same as that of molecular sieves. 　　①　Molecular sieve catalysts possess excellent acid-catalytic activity, which arises from the decomposition of exchangeable ammonium ions, hydrogen ion exchange, or the hydrolysis of polyvalent cations contained within them during dehydration. ②　Metals such as platinum and palladium can be loaded on molecular sieves to produce bifunctional molecular sieve catalysts that possess both metal catalytic and acid catalytic functions. Generally, metal amino complexes are used for cation exchange with molecular sieves, followed by reductive decomposition. ③　Another feature of molecular sieve catalysts is their shape selectivity. Since the catalytic action of molecular sieves generally occurs within the crystal lattice, the pore size and pore structure of molecular sieves have a significant impact on their catalytic activity and selectivity. Molecular sieves possess regular and uniform intracrystalline pore channels, with pore sizes close to the size of molecules; this causes their catalytic performance to change significantly as the geometric dimensions of the reactant molecules, product molecules, or reaction intermediates vary. 　　The good thermal stability and hydrothermal stability exhibited by molecular sieve catalysts are of great significance for industrial applications. Among different molecular sieves, the stability of Y-type molecular sieves is particularly prominent; this stability can be further enhanced by increasing the silica-alumina ratio or by exchanging it with multivalent ions such as rare earths. 　　Production method The basic type of synthetic molecular sieve is Na molecular sieve. To generate solid acidity, polyvalent cations or hydrogen protons must be introduced into the lattice; therefore, ion exchange is often used first in the preparation of molecular sieve solid acid catalysts. Due to factors such as the ionic radius of cations, the ion exchange rates of different cations can vary considerably, and the ion exchange conditions also differ. The metal to be exchanged must exist in solution in the form of cations; however, the water-soluble compounds of some metals do not readily form cations, in which case complex ions can be used as substitutes. For example, platinum can be represented by the Pt(NH4)6^2+ complex ion. When preparing molecular sieve bifunctional catalysts, in addition to the ion exchange method, the impregnation method can also be used; especially for industrial molecular sieve catalysts, the impregnation method is commonly employed to incorporate precious metals. 　　Molecular sieve catalysts typically contain only 5% to 15% molecular sieve; the remaining portion can be referred to as the matrix, which is usually composed of refractory inorganic oxides or their mixtures along with clays. The role of the matrix is to ensure good dispersion of the molecular sieve, to facilitate its bonding and shaping, and even to improve its thermal stability. During the catalytic process, the matrix also acts as a heat carrier. In the production of catalysts, the molecular sieve powder is typically ground using a colloid mill and then mixed into the colloid of the matrix. It is shaped by spraying, extrusion, or other methods, and after steps such as drying and calcination, the catalyst is finally produced.

A molecular sieve is a filter on the molecular scale; it is used to separate molecules. Some molecules can pass through the pores of the molecular sieve, while others cannot. Thanks to this property, molecular sieves can be used in catalysis to carry out selective catalytic reactions on raw materials. I believe that materials with molecular sieve properties are precisely those that possess the characteristics of molecular sieves.

The straight-run fraction of ordinary paraffin-based crude oil (which is roughly similar to the diesel fraction) can be further processed using a molecular sieve dewaxing unit to produce 200# or 300# liquid paraffin; therefore, this fraction of material is referred to as molecular sieve feed.

Look for the book \"Zeolite Molecular Sieves\" on the forum; once you read it, you’ll understand. The molecular sieve used for dewaxing is 5A molecular sieve. Molecular formula: 0.90CaO•0.10Na2O•Al2O3•2.0SiO2•4.5H2O. Physical properties: Non-toxic, with a pH of around 10.5, and it has strong water absorption. The pore size of its molecular sieve micropores is 5 angstroms. It effectively separates n-alkanes (with a molecular sieve diameter of 4.9 Å) from isoparaffins (with a molecular diameter greater than 5 Å).

The main function of molecular sieves is to be used in the water removal systems of air separation units; they are generally used together with aluminum oxide to absorb moisture and carbon dioxide from the air, thereby purifying it.

Molecular sieves are used to separate straight-chain alkanes (liquid paraffin) from oil, as liquid paraffin is expensive. For the fractions of the corresponding raw materials, Fushun Petroleum Plant No. 3 is equipped with a molecular sieve dewaxing unit.

What everyone has said is all good. Molecular sieves can remove water because the diameter of a water molecule is 2.8 angstroms. Moreover, water has the strongest polarity among all gases and liquids. All various conventional molecular sieves preferentially adsorb water. Molecular sieve dewaxing utilizes the differences in molecular sieve diameter among various components of hydrocarbons to separate substances.

I see; this isn’t a molecular sieve – it’s an organic material that has been treated with a molecular sieve

The molecular sieve feedstock is primarily straight-run diesel fractions in the C9-C20 range, with a boiling range generally between 220 and 300 degrees. It is mainly used to produce 300# heavy liquid wax, while its by-products can be used as components in the formulation of diesel or aviation fuel.

It seems there is no clear explanation for the difference between molecular sieves and molecular sieve materials. Is molecular sieve material the raw material for producing molecular sieves? Could it also be considered a diesel component without making such a distinction?