What Is Propyl Alcohol?
Propyl alcohol refers to aliphatic alcohols with the molecular formula C3H8O, including two isomers: n-propyl alcohol (1-propanol) and isopropyl alcohol (2-propanol).
n-propyl alcohol, or 1-propanol, is a primary alcohol with its hydroxyl group on the terminal carbon (CH3CH2CH2OH). Isopropyl alcohol, or 2-propanol, is a secondary alcohol with the hydroxyl group on the middle carbon (CH3CH(OH)CH3).
Uses of Propyl Alcohol
n-propyl alcohol serves as an industrial solvent in applications such as printing inks, textiles, cosmetics, window cleaners, polishing agents, and antiseptics. Isopropyl alcohol is utilized in the synthesis of acetone, disinfectants, solvents for eyeglasses and electronic devices, and as a fuel tank drying agent.
Properties of Propyl Alcohol
1. N-Propyl Alcohol
A colorless liquid with an ethanol-like aroma, n-propyl alcohol has a melting point of -126.5°C, a boiling point of 97.2°C, and is flammable with a flash point of 24°C. It is soluble in water, ethanol, and diethyl ether and requires careful handling due to its classification under hazardous substance regulations.
2. Isopropyl Alcohol
Isopropyl alcohol, a volatile, flammable liquid, has a melting point of -89.5°C, a boiling point of 82.4°C, and a flash point of 11.7°C. It reacts with oxidizers to form methyl ketone and is subject to similar safety regulations as n-propyl alcohol.
Production Methods of Propyl Alcohol
1. N-Propyl Alcohol
n-propyl alcohol is industrially obtained by hydrogenating propionaldehyde, derived from ethylene hydroformylation, using a rhodium complex catalyst.
C2H4+CO+H2 → CH3CH2CHO
CH3CH2CHO+H2 → CH3CH2CH2OH
2. Isopropyl Alcohol
Isopropyl alcohol is produced from propylene via direct or indirect hydration. The direct method involves reacting water vapor with propylene at high temperature and pressure, while the indirect method involves sulfation followed by hydrolysis.
- Direct Hydration Method: CH3CH=CH2+H2O → CH3CH(OH)CH3
- Indirect Hydration Method: CH3CH=CH2+H2SO4 → CH3CH(OSO3H)CH3
CH3CH(OSO3H)CH3+H2O → CH3CH(OH)CH3+H2SO4