Propionic acid

Basic Information

CAS:79-09-4

Appearance: Colorless oily liquid

Melting point: -21.5°C

Boiling point: 141.1°C

Density: 0.99 g/cm³

Flash point: 54°C (CC)

Saturated vapor pressure: 1.33 kPa (39.7°C)

Critical temperature: 339°C

Critical Pressure: 4.53 MPa

Ignition Temperature: 485°C

Refractive Index: 1.3843 (25°C)

Upper Explosive Limit (V/V): 14.9%

Lower Explosive Limit (V/V): 3.0%

Appearance: Colorless oily liquid with pungent odor

Solubility: Miscible with water, ethanol, chloroform, and diethyl ether

Application

1. Used as an organic reagent, esterifying agent, and plasticizer. Since propionic acid dissolves most organic compounds, it is also a commonly used organic solvent.

2. Propionic acid can be used in certain acid pickling and polishing solutions, as a buffer agent in weakly acidic solutions (e.g., zinc plating, electroless nickel plating), as an additive in semi-bright nickel plating electrolytes, and in zinc and cadmium passivation solutions to enhance the adhesion of passivation films. It is also frequently employed to adjust the pH of weakly acidic plating solutions.

3. Synthesis of propionic acid derivatives. Propionic acid is used to produce propionates, such as sodium, aluminum, zinc, and cobalt propionates. These propionates are widely employed as catalysts and as auxiliaries in textile dyeing and leather tanning industries. Additionally, sodium propionate, calcium propionate, and propionic acid serve as food preservatives while supplying trace elements like calcium, sodium, and potassium to food or feed. For instance, adding 0.5% (m/v) calcium propionate to soy sauce enables 90-day mold-free preservation during summer.Propionic acid also serves as an intermediate for synthesizing its esters and derivatives. Propionate esters find broad applications in pesticide herbicides, resin modifiers, sterilants, and plasticizers for cigarette filters. For instance, benzyl propionate functions as an additive in food flavorings and cosmetics, while isopentyl propionate and ethyl propionate are used to blend apple, pineapple, pear, and strawberry flavors, and are also used in artificial floral essential oils. Propionic esters formed from lower alcohols serve as excellent solvents, widely employed in the paint industry [10]. Propionic acid can also be used to synthesize propionic cellulose. Propionic cellulose acetate produced from propionic acid can be used in automotive parts, televisions, and other applications.

4. Determination of aromatic diamines, gas chromatography analysis standards, and also used to inhibit mold growth in insect cell cultures.

5. As a food preservative, propionic acid prevents spoilage caused by microbial activity, extending shelf life. It is particularly suitable for preserving and storing bread and pastries. Propionic acid also preserves poultry feed. Adding 0.5% propionic acid to green fodder prevents mold growth for six months, inhibits protein degradation, and improves digestibility. Sixty percent of China's propionic acid production is used for food preservation and grain storage.

6. As a flavoring intermediate, propionic acid is used alongside acetic acid in butter, milk, and sour milk products. It serves as a raw material for synthetic flavors, imparting a natural sour taste.

7. As a pharmaceutical intermediate, propionic anhydride serves as a propionylating agent in medicine, used to produce antibiotics like propionic acid nystatin. It can also be formulated into dispersants containing 15% calcium propionate, or ointments/solutions containing 12.3% sodium propionate, for treating skin diseases caused by parasitic fungi. It further functions as an intermediate in pharmaceutical synthesis.