As a result of the hydrogenation of liquid fats. Programmable logic controllers - hydrogenation (hydrogenation) of fats
Introduction
Main part
Fats
a) History of discovery and receipt
b) The composition of the molecule, its structure. Types of fats
c) Physical and chemical properties
d) The role of fats in the body
e) Application in technology
Soaps and SMS
a) Definition of soap and SMS, composition, structure
b) History of making soap (soap making)
c) Varieties of soap, the mechanism of the washing action of soap and SMS
d) SMS: advantages and disadvantages
e) Environmental impacts of using VMS
Conclusion
Bibliography
Introduction
Fats or Triglycerides- natural organic compounds, full esters of glycerol and monobasic fatty acids; belong to the class of lipids.
Soap- a liquid or solid product containing surfactants, used in combination with water or as a cosmetic product - for cleansing and skin care (toilet soap); or as a means of household chemicals - detergent (laundry soap).
Synthetic detergents are sodium salts of acid esters of higher alcohols and sulfuric acid:
Soaps, fats and SMS are an integral part of human life, because. they find application in various spheres of life. They have been used by humans for many years. Now our life is hard to imagine without such substances as soaps, fats and SMS.
Main part
Fats
a) History of discovery and receipt
Back in the 17th century. German scientist, one of the first analytical chemists Otto Tachenius(1652-1699) first suggested that fats contain a "hidden acid".
In 1741 a French chemist Claude Joseph Geoffrey(1685-1752) discovered that when soap (which was prepared by boiling fat with alkali) was decomposed with acid, a mass was formed that was greasy to the touch.
The fact that glycerin is included in the composition of fats and oils was first discovered in 1779 by the famous Swedish chemist Carl Wilhelm Scheele.
For the first time, the chemical composition of fats was determined at the beginning of the last century by a French chemist Michel Eugene Chevreul, the founder of the chemistry of fats, the author of numerous studies of their nature, summarized in a six-volume monograph "Chemical studies of bodies of animal origin".
1813 E. Chevreul established the structure of fats, thanks to the reaction of hydrolysis of fats in an alkaline medium. He showed that fats are composed of glycerol and fatty acids, and this is not just a mixture of them, but a compound that, by adding water, decomposes into glycerol and acids.
b) The composition of the molecule, its structure. Types of fats
The main component of fat are glycerol and fatty acids. Fatty acids are divided into saturated and unsaturated. Saturated fatty acids are used by the body as energy material. They can be partially synthesized by the body from carbohydrates and proteins. Among unsaturated fatty acids, polyunsaturated fatty acids are of particular importance. They cannot be synthesized in the human body and therefore are indispensable, as are some amino acids and vitamins. Polyunsaturated fatty acids are found in sunflower, soybean, olive, corn, peach, sesame, mustard and other vegetable oils.
natural fats subdivided into animal and vegetable fats. The consistency of fats and their taste are due to the unequal ratio of saturated and unsaturated fatty acids. The more saturated fatty acids, the higher the melting point of fat (increasing "hardness"), the more difficult it is to be broken down in the body by digestive enzymes. Vegetable fats, as a rule, under normal conditions remain liquid, contain mainly unsaturated fatty acids (linoleic, linolenic, arachidonic), have a low melting point. The source of vegetable fats are vegetable oils, nuts, soybeans, beans, oats, buckwheat and others. Animal fats(mostly dense consistency) is much richer in saturated fatty acids (butyric, palmitic ...). The source of animal fats is lard, lard, butter, sour cream, cream.
Types of fats:
Fats high in saturated fatty acids.
· Fats with a high content of lower unsaturated fatty acids (olive oil, peanut oil).
· Fats with a relatively high content of higher unsaturated fatty acids (burdock, soybean, corn and sunflower oil).
c) Physical and chemical properties
Physical properties of fats:
At room temperature, fats (mixtures of triglycerides) are solid, ointment-like or liquid substances. Like any mixture of substances, they do not have a clear melting point. Only individual triglycerides are characterized by a certain melting point.
The consistency of fats depends on their composition:
- solid fats are dominated by triglycerides with saturated acid residues having relatively high melting points;
- liquid fats (oils), on the contrary, are characterized by a high content of triglycerides of unsaturated acids with low melting points.
The reason for the decrease in the melting point of triglycerides with residues of unsaturated acids is the presence of double bonds in them with cis- configuration. This leads to a significant bending of the carbon chain, which disrupts the ordered (parallel) packing of long-chain acid radicals.
Fats are practically insoluble in water, but when soap or other surfactants (emulsifiers) are added, they are able to form stable aqueous emulsions. Fats are sparingly soluble in alcohol and highly soluble in many non-polar and low-polar solvents - ether, benzene, chloroform, gasoline.
Chemical properties:
Hydrolysis of fats
Hydrolysis is characteristic of fats, since they are esters. It is carried out under the action of mineral acids and alkalis when heated. Hydrolysis of fats in living organisms occurs under the influence of enzymes. The result of hydrolysis is the formation of glycerol and the corresponding carboxylic acids: C 3 H 5 (COO) 3 -R + 3H 2 O ↔ C 3 H 5 (OH) 3 + 3RCOOH
The splitting of fats into glycerol and salts of higher carboxylic acids is carried out by treating them with alkali - (caustic soda), superheated steam, and sometimes with mineral acids. This process is called saponification of fats.
C 3 H 5 (COO) 3 - (C 17 H 35) 3 + 3NaOH → C 3 H 5 (OH) 3 + 3C 17 H 35 COONa
tristearin (fat) + sodium hydroxide → glycerin + sodium stearate (soap)
Hydrogenation (hydrogenation) of fats
The composition of vegetable oils contains residues of unsaturated carboxylic acids, so they can be subjected to hydrogenation. Hydrogen is passed through a heated mixture of oil with a finely divided nickel catalyst, which is added at the site of double bonds of unsaturated hydrocarbon radicals. As a result of the reaction, liquid oil turns into solid fat. This fat is called lard, or combined fat. CH 2 -O-CO-C 17 H 33 CH 2 -O-CO-C 17 H 35
CH-O-CO-C17H33 + 3H2 → CH-O-CO-C 17 H 35
CH 2 -O-CO-C 17 H 33 CH 2 -O-CO-C 17 H 35
triolein tristearin
d) The role of fats in the body
Fats in living organisms are the main type of reserve substances and the main source of energy. In vertebrates, and in humans, about half of the energy that is consumed by living cells at rest is formed due to the oxidation of fatty acids that make up fats.
1. Fat forms protective layers for internal organs: heart, liver, kidneys, and so on.
2. The membrane shell of all cells in the body is approximately 30% fat.
3. Fats are essential for the production of many hormones. They play an important role in the activity of the immune system, and this, as you know, is the body's internal self-healing system.
4. Fats deliver fat-soluble vitamins A, D, E and K to the body.
Method development
The method of hydrogenation of fats was proposed by Norman and S.A. Fokin in 1902-03; for the first time in industry applied in Russia.
The use of fat hydrogenation
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See what "Hydrogenation of fats" is in other dictionaries:
fat hydrogenation- riebalų hidrinimas statusas T sritis chemija apibrėžtis Skystųjų riebalų pavertimas kietaisiais prijungiant vandenilį prie riebalų molekulės dvigubųjų ryšių. atitikmenys: engl. fat hydrogenation; hardening of fats hydrogenation of fats; ... ... Chemijos terminų aiskinamasis žodynas
It is carried out in order to reduce the unsaturation of fatty acids that make up triglycerides. oils (ch. arr. sunflower, soybean, cottonseed) and fats of marine animals (predominantly whale oil). G. f. heterog. catalytic process (cat. ... ... Chemical Encyclopedia
fat hydrogenation- curing of fats ... Dictionary of chemical synonyms I
Hydrogenation of fats is the catalytic addition of hydrogen to esters of glycerol and unsaturated fatty acids. Development of the method The method of hydrogenation of fats was proposed by Norman and SA Fokin in 1902 03; first used in industry in 1908 ... ... Wikipedia
- (hydrogenation) the reaction of adding hydrogen to a multiple bond, usually in the presence of catalysts: The elimination of hydrogen from compounds is called dehydrogenation. Hydrogenation and dehydrogenation are linked by dynamic equilibrium. Most ... Wikipedia
Catalytic addition of hydrogen to esters of glycerol and unsaturated fatty acids; the method of hydrogenation of fats was proposed by Norman and SA Fokin in 1902-03; first used in industry in 1908 in Russia. Hydrogenation… … Great Soviet Encyclopedia
hydrogenation- 4) hydrogenation is the process of partial or complete saturation with hydrogen of unsaturated bonds of unsaturated fatty acids of triacylglycerides that are part of vegetable oils and (or) fats; ...
Harmful fats and their negative impact on the human body - this is the topic of our article. We want to note right away that fats are not only harmful - they are an extremely important and necessary component of the diet, they are extremely nutritious and vital for our organs and tissues.
The energy value of fats is twice that of proteins and carbohydrates. Fats improve the taste of food. They contribute to the absorption of a number of food products, are a source of polyunsaturated fatty acids, phospholipids, and fat-soluble vitamins. Fats aid in the absorption and transport of vitamin A, vitamin D, vitamin E, and vitamin K. Of course, if you consume the "right" fats in the appropriate amount. The “correct” fats and oils are natural compounds found in the tissues of animals and plants, in seeds and fruits. The most valuable fats for the body are in unrefined vegetable oils (olive, sunflower, corn, hemp, flaxseed, soy, peanut), nuts, seeds, avocados, fatty fish (mackerel, herring, salmon).
There are approximately 1300 types of fats in nature, but their elemental composition is quite similar: carbon (76–79%), hydrogen (11–13%) and oxygen (10–12%). The fatty acid spectrum is varied. A vegetable or animal fat molecule is a mixed ester of glycerol and various fatty acids. All fatty acids are divided into saturated, the molecules of which do not contain double bonds between carbon atoms (palmitic, stearic), and unsaturated, the molecules of which contain such bonds (linoleic, linolenic, arachidonic). Animal fats are solid and consist mainly of saturated fatty acids. They contain lard (90–92% fat), butter (72–82%), pork (up to 49%), sausages (20–40% depending on the variety), sour cream (20–30%), cheese (15 -thirty%). Vegetable fats are liquid (except for palm oil) and contain a significant amount of polyunsaturated fatty acids, which are not synthesized in the human body, but are necessary for many biochemical processes. That is why they are indispensable food products. The sources of vegetable fats are oils (99.9% fat), nuts (53-60%), oats (6.1%) and buckwheat (3.3%) cereals. Up to 50% of fats accumulate in the seeds of flax, sunflower, rapeseed, pumpkin.
What is fat hydrogenation?
To increase the shelf life and stability, as well as reduce the cost of food products, the industry uses the process of hydrogenation - the conversion of liquid vegetable oils into solid fats.
Hydrogenation is the saturation of oil with hydrogen atoms for several hours at a temperature of 200–300°C in the presence of nickel or platinum catalysts. At the site of double bonds, hydrogen atoms combine with unsaturated fatty acids, turning them into saturated, and liquid fats into solid ones. In the process of hydrogenation, the natural shape of the fatty acid molecule changes, and its spatial configuration is disturbed. Molecules with a cis configuration are converted into molecules with a trans configuration.
Hydrogenation is used to make cooking fats: margarine, butter substitutes (spread), etc. All over the world, the presence of trans fats is necessarily indicated on product packaging (“trans-fat”), and in our country, “hydrogenated” can be written on the label. vegetable fat. Remember: these are trans fats that are extremely harmful to your body!
Cardiovascular disease, diabetes, cancer, immune system disorders and other diseases are often associated with excessive consumption of high-fat foods. These diseases can only be provoked by “wrong”, harmful fats in excessive amounts.
Scientists recommend consuming no more than 2 grams of trans fat per day. By the way, this amount of trans fats contains one serving of french fries. Fat, on which food was fried for 24 hours, is harmful. It contains up to 32.5% trans fatty acids. Beware of street fried foods!
Why are trans fats dangerous?
Molecules of trans fats disrupt the process of secretion of digestive enzymes in the body, which trigger the mechanism of digestion of food. Once in the blood, trans fat molecules are embedded in cell membranes, displacing omega-6 and omega-3 fatty acids valuable for the body. As a result of this process, the structure of the cell membrane changes. It ceases to pass the necessary nutrients into the cell, and waste products - out. Cellular metabolism is disturbed. Cells of vital organs experience energy hunger, accumulate toxins. The perception of signals by nerve cells is disturbed, and this leads to inhibition of the brain. The regular use of such harmful fats affects the aging process, the development of senile bewilderment, low intelligence in children, and hence the decline in intelligence in the whole nation.
People who abuse foods that contain harmful trans fats have an increased risk of severe neuropsychiatric disorders. It has been proven that when trans fats enter the brain, the activity of the enzyme that provides cellular respiration decreases. This leads to a slowdown in metabolic processes in the brain and an increase in nervous tension, anxiety, and serious neuropsychiatric disorders. Often people do not even realize that the cause of their depressed or irritated state, poor health is a violation of metabolic processes at the cellular level due to the consumption of trans fats. Nutritionists call trans fats a “bulldozer” that destroys our cells, causing them to mutate, accelerating aging. Avoid trans fats!
Numerous studies of world clinics have confirmed that the regular consumption of trans fats has a detrimental effect on the body, especially in children and adolescents, which grows and forms. You should read the labels that indicate the composition of the product - this should become the norm. If we regularly consume trans fats, sooner or later the body will fail.
How to remove trans fats from the body?
Cells have the ability to renew themselves and remove harmful trans fats from the body. Eliminate foods containing hydrogenated fats from your diet and increase your intake of healthy omega-3 fatty acids, which are found in large quantities in flaxseed (58%) and pumpkin (1-15%) oils, walnuts (40%). If you are used to sunflower and olive oils, add oils containing omega-3 fatty acids to them. They are also found in marine fish, such as herring, mackerel, salmon, tuna, and caviar. Consuming daily food containing at least a teaspoon of these oils, you can restore the structure of cell membranes, improve the functioning of the body and reduce the risk of various diseases.
To reduce the cost of production, instead of high-quality cocoa beans, palm fat or cocoa bean waste is added to chocolate bars. This deception is sweetened with sugar. The quality of chocolate (or sweets) can be determined by appearance, smell and taste. Smell the chocolate. If it smells like fat, don't eat it. Rub it. If your hands are smeared like plasticine, it's not chocolate. Try real chocolate and you will remember its unique taste.
- Eat an age-appropriate amount of fat. Eat healthy fats: two-thirds of the diet should be unsaturated fats, and a maximum of one-third (and preferably less) should be saturated.
- Eat more vegetable fats, reduce the number of animals.
- Avoid hydrogenated and partially hydrogenated bad fats, fat substitutes.
- Set an example for your children: don't buy food from fast food restaurants. (“If this food is bad for my health, then why are my parents eating it?”) Do not encourage or reward children with junk food. (“If it is harmful, why is it promised as a reward?”)
- To reduce the calorie content of home baking, replace fatty creams with fruit purees (from apples, prunes, pumpkins, etc.) and dried fruit purees diluted with water (dried apricots, apples, peaches).
- Remember: healthy food is the key to your health. Watch your diet, follow the principles of a healthy diet.
What you need to know about the sources of harmful trans fats?
These products contain trans fats: margarine, spread, mayonnaise and mayonnaise-based sauces, ketchups, fast food, french fries, chips.
In confectionery products (waffles, crackers, donuts, cookies, cakes, sweets, ice cream, chocolate icing), the content of harmful trans fats is from a third to a half of the total amount of fat. Dry concentrates of soups, sauces, desserts, creams, powders for "whitening" coffee, semi-finished products, bread baked on margarine are rich in trans fats.
Trans fats are harmful and toxic. Accumulating in the body, they lead to diseases of the cardiovascular system, increase the risk of sudden cardiac arrest, diabetes, obesity, cancer, liver disease, nervous system. The use of trans fats lowers the amount of testosterone (male sex hormone), increases blood viscosity, leads to hormonal disruptions and metabolic disorders.
HYDROGENATION OF FATS, the conversion of liquid oils into solid fats by adding hydrogen to unsaturated glycerides. All fatty substances are chemically glycerides of fatty acids, i.e. esters of glycerol with the mentioned acids. The difference between solid fats and liquid oils is that the former are dominated by glycerides of saturated acids with the general formula C n H 2 n O 2 (stearic C 18 H 36 O 2 and palmitic C 16 H 32 O 2), while in liquid oils are dominated by glycerides of unsaturated acids with the general formulas C n H 2 n-2 O 2, C n H 2 n-4 O 2, C n H 2n-6 O 2, etc. (oleic C 18 H 34 O 2 and etc.). Since, with the growth of population and with the development of technology, the consumption of solid fats has increased greatly and they were no longer enough for soap making, the production of stearin, etc., and since the expansion of the cultivation of oil plants is a task that can be solved sooner than the task of more intensive breeding of livestock, then it is clear that the idea of obtaining solid fats from liquid vegetable oils by hydrogenation has interested quite a few eminent chemists. This idea was brilliantly carried out by the French chemist Sabatier (see Hydrogenation). Hydrogen for the hydrogenation of fats is obtained either from water gas or by electrolysis (see Hydrogen).
Plant-scale hydrogenation of vegetable oils was first carried out in 1905 by Norman at the Joseph Crossfield a. Sons in Warrington. In Germany, according to Norman's patent, in 1908 the Germania plant in Emmerich began to operate. In the same year, under the leadership of Vilbushevich, a hydrogenation plant was launched at the Persitsa oil mill in Nizhny Novgorod, expanded in 1909 to produce 50 tons of finished product per month. Numerous modifications of fat hydrogenation methods that appeared later, according to Ubbelohde, are reduced to three types: 1) the catalyst is suspended in oil, and hydrogen is passed through this suspension in the form of small bubbles (Norman's method); 2) the catalyst, distributed over a very large surface in an atmosphere saturated with hydrogen, is doused with oil (Erdmann's method); 3) the catalyst is in the form of an oil suspension, and this suspension in the form of tiny droplets passes through a hydrogen atmosphere. At most factories, including Russian ones, they work in such a way that molecular metal Ni, deposited on the surface of infusor earth, is triturated in a paint grinder with a small amount of oil; this mixture is placed in an autoclave, in which the oil to be hydrogenated is located, heated to a certain temperature (190-220 °), and a stream of hydrogen is passed through the autoclave. Thus, the production is divided into two stages: the preparation of the catalyst and the actual hydrogenation.
Catalyst preparation. The starting material is nickel sulfate NiSO 4 7H 2 O. It is dissolved in water up to 14 ° Vè and a double amount of finely ground diatomaceous earth is added to the solution; the mixture is placed in a lead-lined vat and nickel carbonate is precipitated with soda, which is formed according to the following equation:
NiSO 4 + Na 2 CO 3 \u003d NiCO 3 + Na 2 SO 4.
The diatomaceous earth with nickel carbonate deposited on it is filtered using a filter press, thoroughly washed with water until the reaction to sulfuric acid disappears, then dried, calcined, and the resulting nickel oxide is reduced in a hydrogen jet to metallic nickel:
NiCO 3 \u003d NiO + CO 2 And NiO + H 2 \u003d Ni + H 2 O.
Drying, calcination and reduction are carried out in the Vilbushevich apparatus (Fig. 1), which is a cylindrical horizontal retort B, slowly rotating on rollers M.
The retort is surrounded by casing O; oil nozzles Y are placed in the space between the retort and the casing, heating the retort to 500°. Hydrogen enters the retort through tube A; excess hydrogen with water vapor formed during the reaction leaves the retort through the dust collector C, refrigerator F, vessels: G with H 2 SO 4 and NaOH, and finally, through the pump H, hydrogen enters the retort again. Nickel reduction in the Vilbushevich retort lasts 8-12 hours, then the retort is cooled and, in order to avoid nickel oxidation, which is sometimes accompanied by an explosion, it is passed through the retort for 5 minutes. a stream of carbon dioxide. After that, the catalyst is well preserved.
Preparation of oil for hydrogenation. In order for the process of hydrogenation of fats to proceed quickly and completely, it is necessary that the oil to be processed be as free as possible from both mechanical impurities and proteins dissolved in it, resinous, mucous and coloring substances, as well as free fatty acids. The most polluted are linseed oil and camelina oil (Camelina sativa), which have to be cleaned by shaking with H 2 SO 4 (1 1/4 - 1/2%) and NaOH (1.5-2% at 17 ° Vè); the remaining oils are usually refined with diatomaceous earth and various clays (floridin, kaolin).
Hydrogenation process. The purified oil is heated in boilers up to 190-220 ° and transferred to an autoclave; the latter (Fig. 2) is a vertical cylindrical riveted or welded iron boiler with a cone-shaped bottom, equipped with valves for filling and emptying, a cleaning manhole, a pressure gauge with a safety valve, a thermometer and pipes for the inflow of hydrogen H and for removing its excess H 1.
Often there are installations from 2, 3 or 4 autoclaves. In this case, the hydrogen that did not enter into the reaction in the first autoclave enters the 2nd autoclave, from the 2nd to the 3rd, etc. The hydrogen supply pipe in the autoclave usually branches; the branches are provided with a number of small holes, due to which the incoming hydrogen stirs the hydrogenated oil, and the use of a mechanical stirrer is unnecessary. After filling the autoclave (through pipe A) with heated oil, the catalyst prepared as mentioned above is lowered into it (pumps B 1, B 2, B 3 pump the mass from one autoclave to another) and begin to pass hydrogen. The hydrogenation reaction is exothermic, and the oil temperature can rise above 300°, which, however, is eliminated (to avoid dehydrogenation and decomposition of glycerides) by passing steam heated to a temperature of 120-150° into the surrounding autoclave casing. Usually the autoclave is made 1 meter in diameter and about 4.5 m high; oils gain about 2000 kg, and catalyst (nickel + diatomaceous earth) about 30-35 kg, i.e. 1.5%, - therefore, nickel is about 0.5% by weight of oil.
The duration of hydrogenation and the consumption of the catalyst depend on the activity of the catalyst, on the degree of purity of the oil and the degree of saturation of the fatty acids included in its composition. Active catalyst is sufficient 0.2% by weight of oil. Pure cottonseed and sunflower oils are hydrogenated for 2-2.5 hours; it takes 5-6 hours to hydrogenate flaxseed. In addition, the duration of the hydrogenation depends on the degree of saturation to which the oil is desired to be brought. If hydrogenation is carried out to the end, then all unsaturated acids will turn into stearic acid, but it is possible (for example, for fats used in food preparation) to hydrogenate incompletely and obtain fats that are close in their properties to natural animal fats. The degree of hydrogenation is controlled by determining the titer, i.e., the curing temperature of fatty acids isolated from fat, and its iodine number. As hydrogenation proceeds, the titer rises and the iodine number decreases. The table below shows the data on the hydrogenation of sunflower oil with an initial titer of 17.6 and an iodine value of 123, taken from the practice of one of the Russian factories.
Sunflower oil, hydrogenated to a titer of 60°, becomes brittle, easily pounded into powder. Fats with a titer of up to 35° have a greasy consistency, with a titer of up to 45° they are similar to lard. Various factories produce hydrogenated fats under a variety of names and in various consistencies. For example, the German plant in Emmerich produces the following products:
From these figures it can be seen that talgol is close to animal edible fats in terms of melting point, and candelite is suitable for technical purposes. Russian factories also produce hydrogenated fats under various names (salolin, lard, cotton fat), which have different properties.
As for the chemical processes that take place during hydrogenation, according to recent studies, they are not as simple as previously thought: here, not only the conversion of unsaturated acids into stearic acid occurs, but other acids also arise, for example, oleic isomers - elaidic and isooleic acids; they are formed, probably, due to acids with a greater unsaturation; Apparently, there are also processes associated with the movement of double bonds.
Catalyst regeneration. As the catalyst works, it inevitably "poisons", loses its activity, and it has to be regenerated. Poisons that are especially dangerous for the catalyst are: H 2 S, Cl, SO 2, HCN, CS 2, CO and protein substances. These compounds can get into the medium being hydrogenated in the form of impurities to oil and hydrogen. During the regeneration of the catalyst, after filtering on a filter press, it is extracted with gasoline in a Mertz extractor in order to free it from oil; then the defatted catalyst is dissolved in H 2 SO 4 heated with steam to boiling; the NiSO 4 solution is filtered, mixed with a new portion of diatomaceous earth and precipitated with soda, as described above.
The consumption of hydrogen for the hydrogenation of fats depends on the degree of unsaturation of the fatty acids, on the titer to which the fat is to be brought, and on the expediency of devices for mixing hydrogen with oil. If J denotes the iodine number, i.e. % of iodine added, M is the partial weight of the fatty acid, m is the number of carbon atoms and n is the number of hydrogen atoms, then, taking the atomic weight of iodine as 127, we get that
2m-n is equal to the number of iodine atoms attached via double bonds. Hence, the amount of hydrogen
Calculating according to these formulas, Barnitz found that 1.5-2.5 m 3 of hydrogen is required to saturate 100 kg of coconut oil, 12-12.5 m 3 for cotton oil, and 12-15 m 3 for blubber.
properties of hydrogenated fats. During hydrogenation, the saponification coefficient decreases slightly, the acidity hardly changes (increases when heated), the refractive index decreases, the specific gravity increases, and the solubility in solvents (gasoline, ether, benzene) decreases. The smell characteristic of some fats, for example, blubber, disappears during hydrogenation, which is explained by the easy reducibility of clupanodonic acid C 18 H 28 O 2 with five double bonds, the presence of which causes the smell of blubber.
Nothing can be objected against the use of hydrogenated fats in food, since their constants approach those of dietary fats: the fears associated with the presence of Ni in them have no basis: a number of studies carried out on hydrogenated oils showed that the Ni content in them reaches 0.02-0.675 mg per 1 kg of fat, while in 1 kg of vegetables, when they are cooked in a nickel pan, there is up to 127.4 mg of Ni. The economic importance of hydrogenated fats is very high. In Europe there are now up to 80 hydrogenation plants with a capacity of up to 1.5 million tons (there are 7 plants in the USSR). Further, in America, rich in animal fats, there are 15 factories, with a capacity of up to 142,000 tons.
Lesha's method. The described methods of hydrogenation of fats have the following significant disadvantages: 1) the high cost of preparation, 2) the duration of regeneration operations (filtering oil, etc.), 3) the discontinuity of the process, 4) oil hydrolysis caused by diatomaceous earth. All these shortcomings are eliminated by the Lesch method proposed in 1923 and which attracted general attention. This method has not yet been used on a large scale, but a significant plant is already in place at Loders & Nucoline Ltd. Silvertown, London, 2. The method consists in passing oil in a continuous stream through a series of cylinders filled with activated nickel in the form of shavings; A current of hydrogen flows towards the movement of the oil. The peculiarity of the method is the activation of nickel chips. The latter are placed in wire baskets in cylinders. To activate the basket is removed from the cylinders and immersed in a 5% Na 2 SO 4 solution, through which an electric current is passed (Ni - anode, solution - cathode). The anodic oxidation of Ni occurs, the latter being covered with a thin layer of peroxide; the latter is easily reduced by hydrogen at low temperature to a very active surface of metallic Ni. Hydrogenation in the Lesch apparatus can be carried out continuously for three weeks; regeneration of the catalyst requires two days.
This important branch of the fat processing industry has been widely developed in our time due to the fact that the production of margarine and cooking fats, as well as some other technical products, mainly requires solid fats. The growing demand for the latter is mostly met by the use of hardened liquid fats obtained by hydrogenation.
In industry, for hydrogenation, cottonseed, sunflower, soybean and other vegetable oils are used, which contain oleic, linoleic, linolenic and other unsaturated fatty acids in the form of glycerides and saturated acids in small amounts. Of the fats of marine animals, whale oil containing glycerides of fatty acids with four and five double bonds is most hydrogenated. The cured product of hydrogenation is called tallow.
The preparation of fats for hydrogenation is reduced to refining to free them from free fatty acids and various natural impurities that adversely affect the activity of the catalyst and violate the technological mode of hydrogenation.
Nickel and copper-nickel salts in the form of highly dispersed powders are used as a catalyst to accelerate the saturation process in industry, increasing the contact surface of fat with hydrogen. The process of saturation of fat with hydrogen occurs at a temperature of 190-220 ° C to obtain edible lard. The essence of the fat hardening process is that the glycerides of unsaturated fatty acids, which are part of liquid fats, are saturated with hydrogen and turn into solid glycerides of saturated acids. The reaction proceeds in such a way that one hydrogen molecule is attached to each double bond.
The nature of the hydrogen addition reaction in the presence of catalysts determines its reversibility, i.e., along with the hydrogenation process, the reverse process, dehydrogenation, can occur.
The hydrogen addition reaction proceeds in a heterogeneous medium, where the reactants are in three states of aggregation (liquid - oil, solid - catalyst and gaseous - hydrogen). Saturation occurs in places where these three substances collide simultaneously. The reaction can go in the opposite direction if there is no hydrogen at the points of contact between the fat and the catalyst. Under these conditions, dehydrogenation occurs.
Technical hydrogenation is basically a selective process, since its rate is different and depends on the number of double bonds and their position in the glycerides of the hydrogenated fat. There is a selective hydrogen saturation of the radicals of the most unsaturated fatty acids contained in this fat. The more unsaturated fatty acids are hydrogenated first, compared to the less unsaturated ones. Thus, linoleic acid containing two double bonds is hydrogenated to oleic acid faster than oleic acid to saturated stearic acid. In linolenic acid, the double bond in position 15-16 is hydrogenated faster than in position 12-13, and the double bond 9-10 is hydrogenated most slowly. In the fats of marine animals and fish, unsaturated acids with four and five double bonds are first saturated with hydrogen without noticeable formation of saturated acids. Palmitic and stearic acids begin to form only after the iodine number of fat reaches 84-85. Fatty acid glycerides with a higher molecular weight and the same degree of unsaturation are hydrogenated more slowly than glycerides with a lower molecular weight.
When hydrogenating natural fats, there is an interesting pattern in the order of saturation of acids in glycerides with different acids. For example, in cottonseed oil, complete substitution to tristearin occurs only after saturation of glycerides containing palmitic acid. This indicates that stearic acid, compared with palmitic and other lower molecular weight acids, reduces the saturation rate of oleic acid. The slow process of hydrogenation of rapeseed oil is explained, along with some other reasons, by the inhibitory effect of high-molecular-weight erucic acid on the hydrogenation of linoleic acid, which is contained in this oil in the form of multi-acid glycerides.
The selectivity (selectivity) of hydrogenation of fats depends on the nature of the fat and the conditions of the process. In this case, absolute selectivity is practically not observed. The selectivity of fat hydrogenation increases with increasing temperature, which is reflected in an increase in the rate of saturation of linoleic acid glycerides and a decrease in oleic acid glycerides.
An increase in pressure during hydrogenation is accompanied by an acceleration of the reaction in proportion to the hydrogen pressure. With increasing pressure, the selectivity of hydrogenation decreases and the saturation of linoleic acid glycerides increases to a lesser extent than that of oleic acid glycerides.
An increase in catalyst activity accelerates the hydrogenation reaction, but reduces its selectivity. This primarily affects the decrease in the rate of saturation of linoleic acid glycerides and the increase in the rate of saturation of oleic acid glycerides.
At a high rate of hydrogen supply to the catalyst, especially under pressure, hydrogenation proceeds with a significant deviation from absolute selectivity.
During the hydrogenation of fats, along with the process of saturation of double bonds, the formation of positional and geometric isomers of unsaturated acids occurs simultaneously both due to elaidation and due to the migration of double bonds.
Basically, migration occurs with a shift of double bonds by one place and, to a much lesser extent, two places to the right or left of their original position. Isomerization of fatty acid radicals during hydrogenation leads to the formation of isooleic, isoelaidic, conjugated and non-conjugated dienoic acids of cis-, trans-, trans-cis- and trans-trans configurations. The amount of trans acids increases with an increase in the hydrogenation temperature, while the amount of conjugated dienoic acids decreases. The higher the hydrogenation temperature, the more isooleic acids are formed. An increase in pressure leads to a decrease in the accumulation of isooleic acids due to the supply of more hydrogen to the catalyst surface. For this reason, the same effect is also observed with an increase in the intensity of mixing of the reaction components.
During hydrogenation, in addition to the main processes of fat hardening, side reactions also occur, causing some production losses. So, during the thermal breakdown of fat, free fatty acids, acrolein and ketones can be formed. Acrolein readily reacts with water to form hydracrylic aldehyde. At a high hydrogenation temperature, the latter, interacting with water, gives acetaldehyde, formaldehyde, formic acid and methanol. The ingress of moisture makes possible the hydrolytic breakdown of fat with the formation of free fatty acids and glycerol. Hydrogen admixtures supplied for hydrogenation, CO 2 and CO are reduced to methane and water in the presence of a catalyst.
In the process of technical hydrogenation, due to the addition of hydrogen to unsaturated fatty acid radicals, there is a slight increase in fat mass by 0.05-0.20%. However, the total amount of oil loss during refining and hydrogenation overlaps the weight gain from the hydrogen addition reaction. At the same time, during the hydrogenation of fats, the following losses occur: with volatile substances resulting from the thermal and hydrolytic breakdown of fat; with water leaving the grease traps; with filter press cloths; during catalyst regeneration; mechanical.
