Glacial Acetic Acid (Food) - Taiwan

Brief Overview

Glacial acetic acid is the concentrated form of acetic acid, also called ethanoic acid, characterized by the molecular formula CH3COOH. As a weak monoprotic acid, it easily releases a proton from its acid functional group (-COOH), resulting in the formation of the acetate anion as a conjugate base. Acting as a polar protic solvent, acetic acid demonstrates solubility and miscibility in polar solvents like water but remains insoluble and immiscible in non-polar solvents such as octane. When used as a starting reagent, acetic acid readily converts into various organic reagents, including acetyl chloride and ethanol, through substitution and reduction reactions, respectively. Its corrosive nature extends to certain metals like iron, magnesium, and zinc, leading to the production of hydrogen gas and metal acetates. Notably, aluminum, forming a protective layer of aluminum oxide, exhibits resistance to acids, making it suitable for acetic acid transportation. Alternatively, high-density polyethylene (HDPE) drums, known for their resistivity, can also be utilized for transporting acetic acids.

Manufacturing Process

Method 1: Methanol Carbonylation
The manufacturing process for acetic acid involves the carbonylation of methanol. Metal carbonyl is introduced to methanol through either the rhodium-catalyzed Monsanto process or the iridium-catalyzed Cativa process. However, the Cativa process, which benefits from iridium catalysis, has made the Monsanto process obsolete due to its economic and environmentally friendly characteristics. Consequently, the Cativa process has emerged as the predominant method for acetic acid production.

Method 2: Acetaldehyde Oxidation
An alternate approach to acetic acid production encompasses acetaldehyde oxidation. Acetaldehyde is derived by oxidizing butane and hydrating ethylene through the Wacker process. The raw acetaldehyde undergoes purification through extractive distillation, followed by fractional distillation. Subsequently, this acetaldehyde undergoes additional oxidation to result in acetic acid.

Method 3: Oxidative Fermentation and Anaerobic Fermentation
Synthesis of acetic acid can also be achieved through oxidative fermentation using acetic acid bacteria, specifically Acetobacter, in an alcoholic environment. Additionally, anaerobic fermentation utilizing anaerobic bacteria, Acetobacterium, offers an alternative pathway. The Acetobacter method proves to be a more cost-effective means of acetic acid production.

Food Industry

In the food domain, acetic acid functions as both an acidity regulator and a condiment. Its pivotal role extends to being a fundamental element in vinegar production. Additionally, within the food industry, acetic acid is employed as an antimicrobial agent and additive.

Other Applications

Acetic acid plays a vital role in breaking down starches and sugars present in table sugar and milk sugar. It stands as a crucial component in the manufacturing of vinyl acetate monomer, acetic anhydride, acetate ester, and purified terephthalic acid. Moreover, acetic acids have diverse applications in textile processing and printing. They are utilized in the synthesis of acetic anhydride, serving as a significant acetylation agent, primarily applied in the production of cellulose acetate.