Glycerol is colorless, odorless, sweet, and has a clear, viscous liquid appearance. It is an organic substance. Commonly known as glycerin.

The industrial production methods of glycerin can be divided into two major categories: a method using natural oils and fats as a raw material, glycerin obtained as natural glycerin, and a synthetic method using propylene as a raw material, and the obtained glycerin are called synthetic glycerin.

Natural glycerin

Prior to 1984, all glycerol was recovered from by-products of animal and vegetable fat soaps. So far, natural oils and fats are still the main raw material for the production of glycerin, of which about 42% of natural glycerin is made by-product soap and 58% is derived from fatty acid production. The saponification reaction of oils and fats in the soap making industry. The saponification reaction product is divided into two layers: the upper layer is mainly composed of fatty acid sodium salt (soap) and a small amount of glycerin, and the lower layer is waste alkali liquor, which is a dilute glycerin solution containing salt and sodium hydroxide, generally containing glycerin 9-16%, inorganic salt. 8-20%. Oil reaction. The glycerin water obtained by hydrolysis of oil and fat has a glycerin content higher than that of the soap waste liquid and is about 14-20%, and the inorganic salt is 0-0.2%. In recent years, continuous high-pressure hydrolysis has been widely used. The reaction does not use a catalyst, and the obtained sweet water generally does not contain inorganic acid, and the purification method is simpler than the waste alkali solution. Whether it is soap waste liquid or glycerin water obtained by hydrolysis of oil, the amount of glycerin contained in the oil is not high, and all contain various impurities. The production process of natural glycerin includes purification, concentration to obtain crude glycerin, and distillation and decolorization of crude glycerin. Deodorization process.

Synthesis glycerin

The various routes for the synthesis of glycerol from propylene can be grouped into two broad categories, namely chlorination, and oxidation. Propylene chlorination and propylene non-scheduled acetic acid oxidation are still used in the industry.

Propylene chlorination

This is the most important production method for the synthesis of glycerol. It consists of four steps, namely high-temperature chlorination of propylene, hypochlorochlorination of chloropropene, saponification of dichloropropanol and hydrolysis of epichlorohydrin. The hydrolysis of epichlorohydrin to glycerol is carried out in an aqueous solution of 10% sodium hydroxide and 1% sodium carbonate at 150 ° C and 1.37 MPa carbon dioxide pressure to form a sodium chloride-containing glycerin aqueous solution having a glycerin content of 5-20%. It is concentrated, desalted, and distilled to obtain glycerin having a purity of 98% or more.

Propylene peracetic acid oxidation

Propylene reacts with peracetic acid to synthesize propylene oxide, and propylene oxide isomerized to allyl alcohol. The latter is then reacted with peracetic acid to form glycidol (i.e., glycidol) and finally hydrolyzed to glycerol. The production of peracetic acid does not require a catalyst, and acetaldehyde and oxygen are vapor-phase oxidized. Under normal pressure, 150-160 ° C, and contact time of 24 s, the conversion of acetaldehyde is 11%, and the selectivity of peracetic acid is 83%. The latter two steps are carried out continuously in a reaction column of a specific structure. After the raw material allyl alcohol and the ethyl acetate solution containing peracetic acid are sent to the column, the column is controlled at 60-70 ° C and 13-20 kPa. The ethyl acetate solvent and water were distilled off from the top of the column, and the column was stirred to obtain an aqueous glycerin solution. The method has high selectivity and yield and uses peracetic acid as an oxidant, which can be used without a catalyst, and the reaction speed is fast, which simplifies the process. Production of 1t glycerol consumed 1.001t of allyl alcohol, 1.184t of peracetic acid, and 0.947t of by-product acetic acid. Currently, natural glycerin and synthetic glycerol yield almost 50% each, while propylene chlorination accounts for about 80% of synthetic glycerol production.

Industrial grade glycerin

The amount of industrial grade glycerin is diluted with 1/2 amount of distilled water. After stirring well, activated carbon is added and heated to 60-70 ° C for decolorization, and then vacuum filtered to ensure clear and transparent filtrate. The dropping rate is controlled, and the filtrate is added to a column of a previously prepared 732 type strong acid cation resin and a 717 type strong base yin and yang resin to adsorb and remove the electrolyte and aldehydes, pigments, esters and the like in the glycerin. The glycerin solution after removing impurities is subjected to vacuum distillation to control the degree of vacuum of 93326 Pa or more, the pot temperature is 106 to 108 ° C, and most of the water is distilled off, and then the temperature of the pot is raised to 120 ° C to rapidly dehydrate, and the heating is stopped when no water is produced. The material in the kettle is the finished product.

Use of glycerol

Industrial applications

1. Used to manufacture nitroglycerin, alkyd resin and epoxy resin.
2. In medicine, it is used to prepare various preparations, solvents, hygroscopic agents, antifreezes and sweeteners, and external ointments or suppositories.
3. Used in the coating industry to prepare various alkyd resins, polyester resins, glycidyl ethers, and epoxy resins.
4. In the textile and printing and dyeing industry, it is used to prepare lubricants, moisture absorbents, fabric anti-shrinkage treatment agents, diffusing agents and penetrants.
5. It is used as a moisture absorbent and solvent for sweeteners and tobacco agents in the food industry.
6, has a wide range of uses in the paper, cosmetics, leather, photography, printing, metal processing, electrical materials, and rubber industries.
7. Used as an antifreeze for automotive and aircraft fuels and oil fields.
8. Glycerin can be used as a plasticizer in the new ceramic industry.

Daily use

The highest quality one of the food grade glycerin – bio-refined glycerin, in addition to glycerol, as well as reducing sugars such as esters and glucose, is a polyhydric alcohol glycerin; in addition to moisturizing and moisturizing functions, it also has high activity. Special effects such as anti-oxidation and alcohol-promoting.
Complete oxidation of gram of glycerol produces 4 kilocalories, which does not change blood sugar and insulin levels after absorption by the body. Glycerin is a sweetener and moisturizer commonly used in the food processing industry, and is mostly found in sports foods and formulas.

Daily use example

Application in beverages such as fruit juice and fruit vinegar

Different quality fruits contain different degrees of tannins, and tannins are a source of bitterness and astringency in fruits.
Function: Quickly break down the bitterness and odor of fruit juice and fruit vinegar beverage, and enhance the thick taste and aroma of the juice itself. The appearance is bright, sweet and sour.
Add amount: 0.8%~1%

Fruit wine industry application

Wine made from fruit or other dried fruits is only made in different ways. It is called fruit wine (dry red, dry white). There are tannins in fruit wine. Tannin is the source of bitterness and astringency.
Function: Decompose the tannins in the wine, improve the quality and taste of the wine, and remove the bitterness and astringency.
Add amount: 1%

Use of dried meat, sausage and bacon industry

Usage of salted products, dried meat, and sausage:
At the time of processing, the plant refined glycerin is diluted with pure wine of 50 degrees or more, and evenly sprayed on the meat or the cut meat, fully kneaded or stirred.
Function: lock water, moisturize, achieve weight gain effect, extend shelf life.
Add amount: 1.2%~1.5%

Use of the fruit industry

When the fruit is processed, the product is easy to lose water due to storage problems. It is hard and dry, and the fruit also contains tannin.
Function: lock water, moisturize, inhibit tannic hyperplasia, achieve color protection, preservation, weight gain effect, extend shelf life.
Add amount: 0.8%~1%

Use in the wild

In the wild, glycerin can not only serve as an energy-supplying substance but also meet the needs of the human body. It can also be used as an igniting agent by stacking 5-10 g of potassium permanganate solid under combustibles and then pouring glycerin onto potassium permanganate. The flames emerge in about half a minute. Since glycerin is viscous, it can be diluted with a flammable organic solvent such as anhydrous ethanol, but the solvent should not be too much.

Use in medicine

Stabilize blood sugar and insulin

A study was published in the European Journal of Applied Physiology. The researchers divided six healthy young men into three groups, giving glucose, glycerin, and placebo, respectively, and then letting them do the same exercise on the exercise machine. People who took glucose 45 minutes before exercise (0.5 g glucose per pound of body weight), their blood sugar levels increased by 50% at the start of exercise, and insulin levels in the blood increased three-fold. People who took glycerol 45 minutes before exercise (0.5 g glycerol per pound of body weight) had a 340-fold increase in blood glycerol levels at the start of exercise, but there was no change in blood glucose and insulin levels.
Therefore, if you use glycerin instead of high-calorie carbohydrates, you can avoid the negative consequences of eating a lot of biscuits or cakes. It can be said that high doses of glycerin have little effect on blood sugar and insulin levels. A lot of evidence suggests that if your goal is to reduce your carbohydrate intake, glycerin may be ideal glycogen.

As an energy acid

Some scientists also emphasize that glycerin is a good supplement if you want to perform better on the sports field. The reason is that when you have enough water in your body, your body will be stronger and longer lasting. Especially in high-temperature environments, the strong water retention of glycerin helps the body store more water.
A study published in the journal International Journal of Sports Medicine showed that glycerin may contain an acidic substance that produces energy. The researchers compared glycerin with a nutritive sweetener called aspartame by taking glycerin and aspartame separately at a dose of 1.2 g of glycerol per kg of body weight (20% in water). ) or 26ml aspartame. The results show that under sub-extreme exercise load, glycerin can not only reduce the heart rate of the athletes but also extend the exercise time by 20%.
For people with high-intensity physical training, glycerin may give them better performance. For bodybuilders, glycerin may help them transfer body and subcutaneous water to the blood and muscles.

Significance for plant survival

According to new research, some plants have a layer of glycerin on their surface that allows plants to survive in saline soils.

Method for storing glycerol

1. Store in a clean and dry place, and pay attention to sealed storage. Pay attention to moisture, water, and heat. Do not mix with the strong oxidizer. It can be stored in tin or stainless steel containers.
2. Packed in aluminum drums or galvanized iron drums or in tanks lined with phenolic resin. It should be protected from moisture, heat, and water during storage and transportation. It is forbidden to put glycerin together with strong oxidants (such as nitric acid, potassium permanganate, etc.). Store and transport according to the general flammable chemicals regulations.