Glycerin

What are typical applications for Glycerin?

Glycerin has a wide range of industrial applications, including:

• Food and Beverages Industry: Glycerin (E 422) is used as a sweetener, humectant, and solvent in many food and beverage products.
• Cosmetics and Personal Care Industry: Glycerin is used as a moisturizer, emollient and humectant in many cosmetics and personal care products such as soaps, lotions, and shampoos.
• Pharmaceutical Industry: Glycerin is used as an excipient and solvent in many pharmaceutical products, including tablets, capsules, and syrups.
• Chemical Industry: Glycerin is used as a starting material in the production of other chemicals such as nitroglycerin, epichlorohydrin, and propylene glycol.
• Fuel Industry: Glycerin is also used as a fuel and lubricant additive.
• Other Industries: Glycerin is used as an educt in many manufacturing processes. It is also used as an antifreeze, lubricant and plasticizer.

The quality of glycerin is critical for its intended use, and it must meet certain standards for purity, viscosity, and moisture content.

How is Glycerin obtained?

In nature, Glycerin is mainly found in fats and oils. It also plays an important role as an intermediate product in various metabolic processes in most living organisms.

In the past, Glycerin was either obtained petrochemically from propene with the intermediates ally-chloride and epichlorohydrin, or chemically as a by-product in the saponification of natural fats and oils to produce soaps.

Nowadays, Glycerin is commonly obtained as a by-product of the transesterification reaction that converts fats and oils into biodiesel. During this reaction, the fats or oils are reacted with methanol or ethanol to produce methyl or ethyl esters (biodiesel) and crude glycerin. This crude glycerin contains water, salts and impurities, which must be removed to obtain the pure Glycerin.

Glycerin as a by-product of biodiesel production

Since the mid-1990s, biodiesel (fatty acid methyl ester) has been produced from vegetable oils. The by-product of this process is glycerin, which after processing can be sold either concentrated (at least 80% glycerin content) or distilled (glycerin content 99.7%). The production of one metric ton of biodiesel yields slightly more than 100 kg of glycerin. The glycerin is produced in the biodiesel production process as follows: Vegetable oil triglyceride + 3 x methanol = 3 x vegetable oil methyl ester + glycerin.

In relation to the vegetable oil used, about 10% glycerol is produced. Since glycerol, unlike biodiesel, is polar, all the polar substances formed during the reaction that are naturally present in the oil or enter the oil during oil treatment collect in the glycerol. These are in particular methanol, water, soap, inorganic salts and polar organic compounds.

The soap alone in the biodiesel (approx. 8-35%, depending on process control and procedure) would make distillation of the crude glycerin impossible. For this reason, the glycerol must be prepared for distillation in several steps.

The preparation steps are:

1. Separation of the methanol (possible both here and in step 4, depending on the process)
2. Separation of the catalyst from biodiesel production
3. Separation of the soaps, separation of the fatty acids and other residual organic products in the glycerol and subsequent neutralization
4. Separation of the methanol
5. Concentration (water evaporation) of glycerol
6. Distillation for the production of pharmaceutical glycerol

Principle of the process

The still impure glycerol from step 6 is refined by distillation to 80-85% to so-called „pharmaceutical glycerol“. The settled salt suspension (sodium chloride or potassium chloride) is separated at high temperatures by a special SIEBTECHNIK TEMA decanter for very high temperatures. In other processes, a thin-film evaporator is also used for this purpose, but in recent years separation with a (possibly upstream) SIEBTECHNIK TEMA SHORTBOWL decanter has become established on the market.

The separated salt can later be landfilled or put to another use. The pharmaceutical-grade glycerol has a purity of >99.5% and is later used in the chemical industry, among others.

Why are centrifuges important in the production of pharmaceutical grade glycerin?

Centrifuges are key equipment in the production of pharmaceutical grade glycerin because the purity and quality of the glycerin is critical to its use in the pharmaceutical industry.

They are used to separate the glycerin from the unwanted impurities mentioned above, and to wash and dry the glycerin to achieve the quality required for use in the pharmaceutical industry.