How To Dry Organic Solvents
How to dry organic solvents? Most of such solvents are toxic or flammable, and this increases risks in their drying process. But there are still many ways for the dehydration of organic solvents like using drying agents or specially-designed equipment. What we are focusing today is the drying agents for organic solvents.
Drying agents for organic solvents — choosing principle
The properties of the agents are different. When choosing them, the characteristics and nature of the drying agents for organic solvents must be fully considered to achieve the purpose of drying effectively.
1. Firstly, make sure that the substance to be dried does not react with the agents.
2. Secondly, drying speed, drying effect and water absorption of the agents must be taken into consideration.
3. Thirdly, it is best to use acidic agents for drying acidic materials, alkaline agents for alkaline materials, and neutral agents for neutral materials.
4. The last choosing principle of drying agents for organic solvents is that if there is a large amount of water in the solvent, avoid using an agent that catches fire in contact with water (such as sodium metal) or produces violent heat. A mild agent such as calcium chloride can be used for drying and dehydration to reduce the moisture. When the moisture is reduced to certain content, then you can use sodium metal.
Drying agents for organic solvents — metal, metal hydride
Al, Ca, Mg: commonly used in the drying of alcohol solvents;
Na, K: suitable for drying solvents such as hydrocarbons, ethers, cyclohexylamine, and liquid ammonia.
CaH2: suitable for the drying of solvents such as hydrocarbons, halogenated hydrocarbons, alcohols, amines, ethers, etc., especially cyclic ethers such as tetrahydrofuran, dimethyl sulfoxide, and hexamethylphosphoramide. The polar aprotic solvents commonly used in organic reactions are also dried by this method;
LiAlH4: drying of commonly used solvents such as ethers.
Drying agents for organic solvents — neutral agents
CaSO4, NaSO4, MgSO4: suitable for the drying of hydrocarbons, halogenated hydrocarbons, ethers, esters, nitromethane, amides, nitriles and other solvents;
CuSO4: suitable for the dehydration of alcohols, ethers, esters, and lower fatty acids.
CaC2: suitable for alcohol drying.
CaCl2: suitable for drying hydrocarbons, halogenated hydrocarbons, ether nitro compounds, cyclohexylamine, nitrile, carbon disulfide, etc.
Activated alumina: suitable for drying hydrocarbons, amines, esters, and formamide.
Drying agents for organic solvents — alkaline agents
KOH, NaOH: suitable for drying basic substances such as amines and cyclic ethers like tetrahydrofuran.
K2CO3: suitable for the drying of alkaline substances, halogenated hydrocarbons, alcohols, ketones, esters, nitriles, cellosolves and other solvents. Not suitable for acidic substances;
BaO, CaO: suitable for drying alcohol, alkaline substance, nitrile, amide. Not suitable for ketones, acidic substances and esters.
Drying agents for organic solvents — acid agents
H2SO4: suitable for drying saturated hydrocarbons, halogenated hydrocarbons, nitric acid, bromine, etc. Alcohol, phenol, ketone, unsaturated hydrocarbon, etc. are not applicable;
P2O5: suitable for the drying of hydrocarbons, halogenated hydrocarbons, esters, acetic acid, nitrile, carbon disulfide, and liquid sulfur dioxide. Ether, ketone, alcohol, amine, etc. are not applicable.
Not only drying agents, but some machines can also be used in the drying of organic solvents, like Hawach’s closed loop spray dryer. Now you should have a basic idea on how to dry organic solvents. There are also other ways that waited to be discovered.