What Is Pure Glycerin?

Check out this answer from Consensus:

Pure glycerin is a crucial compound with diverse applications across multiple industries. Its production from biodiesel by-products and subsequent purification processes ensure that high-quality glycerin is available for various uses. As technologies advance, the role of glycerin in sustainable and renewable applications is expected to grow, further highlighting its importance in modern biorefineries and beyond.

Pure glycerin, also known as glycerol, is a simple polyol compound that plays a significant role in various industrial and pharmaceutical applications. It is characterized by its three carbon atoms, each bonded to a hydroxyl group, making it a versatile and valuable substance in numerous fields.

Chemical Structure and Properties

Glycerin is a trihydroxy alcohol with the chemical formula C3H8O3. Its structure consists of three carbon atoms, each attached to a hydroxyl group (-OH), which contributes to its hygroscopic nature and solubility in water. This molecular arrangement allows glycerin to form hydrogen bonds, making it an excellent solvent and humectant.

Production of Glycerin

Glycerin is primarily produced as a by-product during the biodiesel production process. The transesterification of triglycerides, such as animal fats, vegetable oils, or used cooking oils, results in the formation of crude glycerin. This crude form contains various impurities, including water, methanol, and soap residues, which necessitate further purification to obtain pure glycerin2.

Purification Processes

The purification of crude glycerin involves several steps to remove impurities and achieve high purity levels. Common methods include:

1. Distillation: This process involves heating the crude glycerin to separate it from impurities based on their boiling points. Distilled glycerin typically contains at least 99.5% glycerol and is used in high-quality applications such as food, pharmaceuticals, and cosmetics2.
2. Sequential Extraction: This method uses organic solvents like petroleum ether and toluene to extract impurities from crude glycerin. The process is followed by discoloration with activated carbon, resulting in glycerin with a purity of 99.2%3.
3. Ion Exchange Resins: These resins are used to remove trace amounts of sulfur and nitrogen compounds from crude and distilled glycerin. While ion exchange resins are not effective at the preliminary purification stage, they are useful for purifying distilled glycerin produced from waste materials2.

Applications of Pure Glycerin

Pure glycerin’s versatility makes it valuable in various industries:

• Food Industry: It is used as a sweetener, humectant, and preservative in food products.
• Pharmaceuticals: Glycerin serves as a solvent, sweetening agent, and preservative in medicinal formulations.
• Cosmetics: Its moisturizing properties make it a common ingredient in skincare products.
• Biochemical Production: Glycerin is a promising renewable raw material for synthesizing biofuels, chemicals, and bioenergy2.