What are the main types of deoxidants (e.g., by chemical composition)?

Deoxidizers are divided into organic and inorganic functional groups based on their chemical composition, with each group comprising several major subclasses that differ in structure, mechanism of action, and application fields (such as food industry, cosmetics, polymer industry, petroleum processing, etc.). The following is a detailed classification of key representatives and their characteristics:

1. Inorganic deoxidizer

Simple compounds based on inorganic elements (metals, salts, oxides) are mainly used as chemical adsorbents (reacting with O ₂ to form stable compounds) or to inhibit oxidation reactions by forming complexes with catalytic metals (iron, copper, cadmium). Main subclasses:

• Alkaline metals and their alloys (aluminum, zinc, iron powders): react with oxygen (and moisture) to form oxides, which are used as O ₂ absorbents in sealed packaging (such as food).

• Sodium sulfite (sodium sulfite Na ₂ SO Ⅲ, sodium sulfite NaHSO Ⅲ, potassium sulfite K ₂ S ₂ O ₅): the most common inorganic deoxidizer in the food industry. They repair the formed peroxides, block free radicals, and absorb oxygen. Used for canned food, juice, wine, and meat.

• Phosphates and polyphosphates (sodium tripolyphosphate, calcium phosphate): In addition to their antioxidant properties, they also combine with metal catalysts (formed by recombination) to prevent accelerated oxidation processes. Used in the food industry (dairy products, meat) and polymer industry (plastic stabilization).

• Rare earth metal oxides and hydroxides: used in high-temperature processes (such as metallurgy) because they maintain their antioxidant properties at high temperatures.

2. Organic deoxidizer

The most diverse functional groups of carbon compounds based on active groups (hydroxyl, amino, sulfur). They mainly act as inhibitors of free radical reactions (hydrogen or electron donors to stabilize the reaction free radicals generated during oxidation initiation) or synergistically (enhancing the effects of other deoxidizers). Divided into several key subcategories based on functional group structure:

2.1 Phenol Deoxidizer

The most common organic antioxidant - the molecular nucleus is a benzene ring, and the hydroxyl group (- oh) easily transfers the hydrogen atom to the free radical, stabilizing it. The benzene formed from this is essentially stable and does not participate in further chain oxidation reactions. Main representatives:

• Natural: Vitamin E (tocopherol, especially alpha tocopherol), caffeic acid, gallic acid, resveratrol, quercetin (from plant extracts: green tea, grape seeds, rosemary). Used in the food industry and cosmetics.

• Synthesis: Butylhydroxytoluene (BHT), Butylhydroxyphenol (BHA), Propionate, Octyl Gallat, Dodecyl Gallat. Widely used in the food industry (oil, fat, candy), polymer industry (plastic stabilization, rubber), and petroleum processing.

2.2 Amine Deoxidizer (Amine and Its Derivatives)

They act as donors of electrons (rather than hydrogen), effectively stabilizing free radicals. It is particularly active at high temperatures (up to 200-300 ° C), and is therefore mainly used in technical fields such as petroleum processing, plastic production, lubricants, etc., for processing at high temperatures. Main representatives:

• Alkyl diphenylamine (ADPA), aniline (PPD), naphthylamine, and dialkyl dicarboxylate. Used for engine oil, transmission fluid, and polyolefin stabilization (polyethylene, polypropylene).

2.3 Sulfur containing organic deoxidizer

Sulfur groups (- sh, - s -, - sr) act as peroxide disruptors: they decompose the intermediate peroxide (rooh) into stable alcohol or other inactive compounds. It is commonly used as a synergistic enhancer for phenol deoxidizers, enhancing their effectiveness several times. Main representatives:

• Dithiocarbonate, thiopropyl ester (dithiodipropionate, dithiodipropionate), thiothiothiobenzene. Used in the polymer industry, petroleum processing, and cosmetics.

2.4 Organic Nitrifying Deoxidizer

Less common groups include compounds with nitrogen-containing functional groups (imines, hydrazine, triazoles). As a complex forming agent for inhibitors of free radical reactions and metal catalysts. Mainly used in the technical field (rubber stabilization, lubricants).

2.5 Carbonic acid and its derivatives

It includes fatty acids and aromatic carboxylic acids, with several hydroxyl groups, which transfer hydrogen to free radicals and bind with metal catalysts. Mainly used in the food industry and cosmetics. Main representatives: ascorbic acid (vitamin C) and its derivatives (sodium ascorbate, ascorbic acid), citric acid, malic acid, and grape wine acid.

Supplementary classification: Collaborative efficiency enhancement (non independent but important component)

They are not typical deoxidizers, but rather enhance the action of basic antioxidants (usually phenol or sulfur). This includes:

• Fatty acid salts calcium, magnesium, zinc salts (combined with metal catalysts);

• Phospholipids and polysaccharides (forming a protective film on the surface of the product to prevent contact with oxygen);

• Citrate, Malati (metal complex).