Merck, 208574-5KG, Molecular sieves, 3 Å

General description
Molecular sieves are crystalline metal aluminosilicates having a 3-dimensional interconnecting network of silica and alumina tetrahedra. Natural water of hydration is removed from this network by heating to produce uniform cavities which selectively adsorb molecules of a specific size. The 3A form is made by substituting potassium cations for the inherent sodium ions of the 4A structure, reducing the effective pore size to ~3Å, excluding diameter >3Å, e.g., ethane. The 4 to 8-mesh type is normally used in gas-phase applications. Molecular sieves are considered a universal drying agent in polar and nonpolar media.
Application
Molecular sieves, 3 Å may be used in the following processes:
As a general-purpose drying agent in polar and nonpolar media.
Commercial dehydration of unsaturated hydrocarbon streams, including cracked gas, propylene, butadiene, acetylene
Drying polar liquids such as methanol and ethanol.
Adsorption of molecules such as NH₃ and H₂O from a N₂/H₂ flow.

Molecular sieves have been used for the drying of dimethyl sulfoxide.
They may also be used in the following:
Synthesis of ecteinascidin 743 (a potential marine-derived antitumor agent).
Preparation of vanillyl nonanoate (a model capsinoid compound).
Highly enantioselective Friedel-Crafts alkylation of indoles with nitroalkenes.