Butyric Acid (n-Butyric Acid /酪酸) — High-Purity Short-Chain Fatty Acid Core Industrial Raw Material

I. Product Overview: Basic Industrial Attributes

n-Butyric acid (CH₃CH₂CH₂COOH), molecular weight 88.11, is a straight-chain saturated short-chain fatty acid (SCFA). At room temperature, it appears as a colorless to pale yellow oily liquid with a strong, unpleasant, rancid odor (at high concentrations). However, this odor completely transforms into a pleasant fruity aroma upon esterification. Its key industrial characteristics include:

• Miscible with water; readily soluble in ethanol, diethyl ether, and most organic solvents

• Weak acidity (pKa 4.82) with moderate reactivity, facilitating targeted synthesis

• Volatile with steam; forms an azeotrope with water

• The solubility of its calcium salt decreases with increasing temperature (useful for separation and purification)

Core Industrial Value: n-Butyric acid is not a consumer end-product but rather a high-value chemical synthesis bridge, transforming into a range of functional derivatives through carboxyl group reactions (esterification, acyl chlorination, amidation, etc.).

II. Industrial Production Routes and Quality Comparison

Currently, the direct oxidation of n-butyraldehyde absolutely dominates global industrial production:

Process characteristics: Propylene oxo synthesis to produce n-butyraldehyde → Liquid-phase air/oxygen oxidation → Purification by distillation

Technical advantages: Single raw material, short process flow, high degree of automation, good atom economy

Output specifications: High purity ≥99% (imported/advanced processes), whereas products from early-stage domestic small-scale plants are only around 98%, with impurities affecting downstream esterification reaction yields and fragrance purity

Production capacity pattern: Global annual output is approximately 30,000 tons, concentrated in Central Europe and the United States; high-end domestic demand (pharmaceutical-grade, fragrance-grade) has long relied on imports

III. Industrial Functions and Chemical Mechanisms

The industrial "function" of n-butyric acid is not direct application, but rather the transformation efficiency achieved through its molecular structure:

1. Esterification Reaction — Production of Butyrate Esters as Fragrances and Solvents

General reaction: C₃H₇COOH + ROH → C₃H₇COOR + H₂O

Functional outputs:

• Ethyl butyrate (pineapple aroma) — Food flavors, wine flavoring

• Amyl butyrate (apricot/pear aroma) — Cosmetic fragrances, food additives

• Benzyl butyrate (jasmine aroma) — Fixative for premium perfumes

Industrial role: n-Butyric acid provides the butyryl group (C₃H₇CO–), imparting characteristic fruity aromas and good volatility to the esters.

2. Cellulose Modification — Cellulose Butyrate Esters

n-Butyric acid esterifies with cellulose, partially substituting the hydroxyl groups of cellulose to produce Cellulose Acetate Butyrate (CAB)

Functional performance:

• Outstanding heat resistance, light resistance, and moisture resistance

• Excellent film-forming properties and leveling characteristics

• Good compatibility with various resins and plasticizers

Industrial role: Used in high-grade coatings (automotive paints, wood finishes), plastic molding, printing inks, etc., solving the problems of yellowing and brittleness associated with traditional nitrocellulose.

3. Other Fine Chemical Transformations

• Preparation of butyric anhydride (acylating agent) and butyryl chloride (highly reactive intermediate)

• Synthesis of sodium/calcium butyrate (although involving pharmaceutical/feed applications, the core remains the capability to produce industrial salts)

IV. Direct Impact of Purity on Industrial Functionality

In industrial applications, the purity difference between 98% vs. 99%+ directly determines:

• Esterification reaction rate: Impurities (especially water and isobutyric acid) inhibit acid-catalyzed esterification

• Odor of downstream products: Residual n-butyric acid's rancid smell can ruin the purity of fragrance formulations

• Transparency of cellulose esters: Metal ions or oxidative by-products cause yellowing in CAB

Therefore, high-purity n-butyric acid is a prerequisite for achieving stable industrial functionality.

Safety Information:

• Flammability: Burns when exposed to open flame or oxidizing agents; combustion products are CO and CO₂

• Irritancy: High concentrations are moderately irritating to skin and mucous membranes; enclosed operation and local exhaust ventilation are required

• Toxicity: Low toxicity (LD50 2000 mg/kg, oral, rat), but direct contact should be avoided.

Summary (Industrial Procurement Oriented)

The core industrial functionality of n-butyric acid lies in its irreplaceable role as a butyryl group donor for butyrate ester fragrances, cellulose acetate butyrate (CAB), and fine chemical intermediates. The realization of its industrial value is highly dependent on purity (≥99%) and a stable aldehyde oxidation process. Selecting n-butyric acid is essentially choosing downstream product yield, fragrance purity, and material performance.