RU2093503C1 - Method of distillation of industrial glycerol - Google Patents

Abstract

FIELD: chemical, processing, food and other industries. SUBSTANCE: distillation of industrial glycerol is carried out in vacuum at cube temperature of 175-183 C during bubbling with live steam in the presence of polymeric organosilicon liquid containing no end functional groups and immiscible with glycerol. Said liquid includes polydimethyl-, polyethyl- and polymethyl phenyl siloxane liquids of various grades. Said liquid is added to the glycerol to be distilled in amount of 2.5-10 wt %. The claimed method makes it possible to carry out distillation when no viscous stillage residue is formed, to increase quality of the product to be distilled, and reduce discharges of toxicants into atmosphere, thus improving economic and ecological process parameters. EFFECT: more efficient distillation method. 2 cl

Description

 The invention relates to the field of chemical technology, and in particular to methods of purification of organic compounds from unwanted impurities by distillation (distillation) in specially constructed plants, and can be used in chemical, processing, food and some other industries.

 Known methods for the distillation of organic (and inorganic) substances by a single evaporation method. The distilled mixture is heated to boiling point to obtain a distillate and a still residue.

At high boiling points, and especially in the case of decomposition of a substance at this temperature (acetoacetic ether, boiling point 181 ^o C with decomposition), distillation under reduced pressure (vacuum) is used. The distillation system is a homogeneous solution.

 By distillation at atmospheric pressure and in vacuum, distillate fractions and up to 40% bottoms are obtained. The bottom residue (coke, resin, tar, semi-tar) in composition differs from the initial mixture, and it is formed due to local overheating, which can hardly ever be avoided.

 The closest technical solution, selected as a prototype, is a method for the distillation of glycerol obtained by the non-reactive cleavage (hydrolysis) of animal and vegetable fats.

Technical 86-88% aqueous solution of glycerol (saponificate) is distilled (distilled) in a vacuum of 15-20 mm RT. Art. at a temperature in the cube of 170-180 ^o C and when bubbling hot steam with a pressure after the washer of 0.2-0.8 ati. The cube is heated with blank steam supplied to the coils. As the water containing traces of glycerol (the so-called “sweet water”) and the glycerol itself are distilled off, new portions of heated saponificate are fed into the cube of the distillation unit, and this continues until a sharp decrease in the unit's performance (from 6 to 2 tons of distilled glycerol per day ) and increase the temperature in the cube to 190 ^o C. The process is stopped to remove the resulting still bottom residue of tar.

 The disadvantages of the existing method of distillation are the formation of still residue of tar and the need for its timely removal from the cube of the installation. The tendency of the tar to harden necessitates timely operations on the inadmissibility of its curing, such as boiling the tar with hot water (condensate) and hot steam. Draining of a tar solution that does not find industrial application is carried out into the sewer system, which complicates the process technology and worsens the environmental situation.

In addition, the need for stopping to remove tar reduces installation performance. During installation, a significant amount of harmful substances, such as acrolein, are emitted into the atmosphere. So, for example, during the operation of two glycerol distillation plants, the total emission of acrolein into the atmosphere is 1.4 mg / m ³ or 0.008 t / year.

Distilled glycerol is selected in 500 kg portions. The maximum number of 90 servings. In the last 30-40 servings, the content of the main product decreases on average to 97.4% and the content of esters increases on average to 0.43%
The aim of the invention is to increase the productivity of the installation for distillation by lengthening the duration of its continuous operation, improving the quality of the distilled product and improving the environmental situation at the enterprise due to the lack of discharge of bottom residue into the sewer and a sharp reduction in emissions of harmful substances into the atmosphere.

R=CH₃, C₂H₅, C₆H₅; n 3-700
Из числа известных кремнийорганических жидкостей были использованы полидиметилсилоксановая ПМС-200 (ГОСТ 13032-67), полидиэтилсилоксановая ПЭС-5 (ГОСТ 13004-67) и полиметилфенилсилоксановая ПФМС-4 жидкости с вязкостью 200-1000 сСт в количестве 2,5-10,0% от массы перегоняемого продукта.These goals are achieved by the implementation of the proposed method of distillation with feeding before the start of the process into the cube of the distillation unit to the chemically inert and heat-resistant polymer organosilicon liquid intended for distillation of the crude (technical) product without end functional groups: polydimethyl-, polydiethyl-, polymethylphenylsiloxane general formula

R = CH ₃ , C ₂ H ₅ , C ₆ H ₅ ; n 3-700
Among the known organosilicon liquids were used polydimethylsiloxane PMS-200 (GOST 13032-67), polydiethylsiloxane PES-5 (GOST 13004-67) and polymethylphenylsiloxane PFMS-4 liquids with a viscosity of 200-1000 cSt in an amount of 2.5-10.0% by weight of the distilled product.

 These liquids are produced in sufficient quantities by the domestic industry and are widely used as the basis for greases and release agents, antifoam agents and foam regulators, in pharmacy and cosmetics, as the basis for ointments and additives that improve the consumer properties of products, in mastics for floors polishing compositions, creams for shoes, in auto cosmetics, as a separation medium in gas-liquid chromatography, as cast dampers in various devices, as additives, improving their quality of coatings and others. We do not know the use of the proposed liquids in the distillation of organic products, which allows us to conclude that the proposed feature is new. The non-obviousness of the use of the proposed feature is proved as follows.

 Typically, the mixture intended for distillation is a homogeneous (homogeneous) solution; in the proposed method, the organosilicon liquid does not mix with the distilled substance or mixture of substances, forming a second layer. Depending on the specific gravity, a layer of organosilicon liquid is either above or below. During distillation through a distilled liquid, air, inert gas or sharp vapor is bubbled, and an unstable emulsion is formed in which the organosilicon liquid acts as a dispersed phase and is a regulator of the thermal regime. The possibility of local overheating is sharply reduced or absent altogether, the casing is not gummed.

 After distillation of the entire contents, the organosilicon liquid remains in the cube of the distillation unit unchanged and in the same amount. A new portion of the product intended for distillation is added to it, and so on ad infinitum.

 The inventive method was implemented in both industrial plants for the distillation of glycerol at the enterprise of the St. Petersburg joint-stock company "Nevskaya Cosmetics".

 The effectiveness of the proposed method for the distillation of organic compounds is confirmed by the following examples.

Example 1. 3200 kg of technical 88% solution of glycerol (saponificate) heated to 175 ^o C and 80 kg (2.5% by weight of saponificate) of PES-5 organosilicon liquid (GOST 13004-67) are fed into the cube of the distillation unit . The distillation is carried out in a vacuum of 15-20 mm RT. Art. and at a temperature in the cube of 175-180 ^o C, while mixing the contents of the cube with injected steam with a pressure of 0.8 MPa. The cube is heated with blank steam supplied to the coils. The continuous process lasts 10-15 days, as the water containing traces of glycerol (the so-called "sweet water") is distilled off, and glycerol itself is periodically fed into the cube of the plant, new portions of heated saponificate of 1000-2500 kg each. Distilled glycerin is selected in portions of 500 kg.

 During the processing of 77800 kg of a technical 88% glycerol solution, 125 portions of distilled glycerol of 500 kg (129 • 500 64500 kg) and 49400 kg of “sweet” water containing 49400 • 0.015 740 kg of glycerin are taken (according to the factory laboratory, the average glycerol content in "sweet" water 1.5%).

 During the operation of the installation for six months, tar in the cube of the installation is not formed. In the last 30 servings of distilled glycerin, its average concentration was 93.6%; the content of disputable esters was 0.35%. There is no acrolein in air emissions.

Example 2. To 200 g of an 88% solution of glycerol (saponificate), add 20 g (10%) of the PMS-200 polydimethylsiloxane liquid (GOST 13032-67), as sweet water and glycerol are distilled off at a temperature of 183 ^o C (14 mm RT) Art.) in a cube of the distillation unit periodically add 11 servings of 150 g of saponificate heated to 150 ^o C. A total of 1574 g of glycerol with a specific gravity d $\genfrac{}{}{0ex}{}{\text{twenty}}{\text{4}}$ 1.2602. VAT residue is not formed.

By distillation under similar conditions, but without the addition of PMS-200 liquid, 293 g (18% by weight of 100% glycerol) of tar residue are obtained, as well as 1240 g of glycerol with a specific gravity of d $\genfrac{}{}{0ex}{}{\text{twenty}}{\text{4}}$ 1.2516.

Example 3. To 500 g heated to 105 ^o With a mixture of fatty acids obtained by splitting (hydrolysis) of animal fat of the highest grade by a non-reactive method, dropwise add 25 g (5%) of polymethylphenylsiloxane liquid PMFS-4 with d $\genfrac{}{}{0ex}{}{\text{twenty}}{\text{4}}$ 1.1, which forms the bottom layer in the cube of the distillation unit, as it is distilled off at a temperature of 220-230 ^o C (10-15 mm Hg), 13 portions of 150 g of fatty heated to 160 ^o C are periodically added to the cube of the distillation unit acids. A total of 2380 g of the final product of distilled fatty acids (a mixture of them) was taken; no oak residue was formed. PMFS-4 silicone fluid remains unchanged.

 According to a similar scheme for the distillation of fatty acids in an amount of 500 + (150 • 13) 2450 g, but without the addition of organosilicon liquid, 1940 g of distilled fatty acids are selected; 390 g (15.9%) of the bottom residue of tar is formed in the cube of the plant.

 Example 4 (control, without the addition of organosilicon liquid).

от массы глицерина, взятого для дистилляции.In the cube of the distillation unit serves 2000 kg of technical 88% solution of glycerol heated to 175 ^o C. The distillation is carried out in a vacuum of 15-20 mm RT. Art. and at a temperature in the cube 175-180 ^o C. In total, 61,000 kg of 88% glycerol solution were processed per cycle. Selected (500 • 32) +300 46300 kg of distilled glycerol and 25800 kg of sweet water, which contained 25800 • 0.015 400 kg of glycerin. VAT residue in the amount of (61000 • 0.88) - 46300 400 6980 kg, or

by weight of glycerol taken for distillation.

 The proposed method of distillation can be implemented on any other industrial and laboratory installations for fractional distillation of mixtures or distillation of organic compounds.

Using the proposed method for the distillation of organic compounds in the presence of an organosilicon liquid provides the following advantages compared to existing methods:
The absence of bottom residue of tar, coke, resin, semi-tar during the operation of the unit for six months improves the environmental situation in the village, because reduces the discharge of harmful substances into a reservoir or sewer.

 The process technology is simplified and the productivity of the distillation plant is increased, as no need to spend time stopping to digest the tar and lowering its solution, followed by washing the cube.

 The yield of the final product increases (approximately 15%).

 The quality of the final product improves.

 The emission of harmful substances into the atmosphere is reduced.

Claims (2)

1. The method of distillation of technical glycerin in vacuum at a temperature of 175 183 ^o C cube while bubbling with hot steam, characterized in that the distillation is carried out in the presence of a polymer organosilicon liquid, not miscible with glycerin, in an amount of 2.5 to 10.0% by weight.  2. The method according to claim 1, characterized in that as the polymer organosilicon liquid take polydimethyl-, polydiethyl-, polymethylphenylsiloxane liquids PMS, PES, PFMS of various grades.