Hydrogen chloride, chemical formula HCl, molecular weight 36.461, is a colorless, irritating, corrosive and asphyxiating gas, which strongly smokes in wet air[1-2]。A molecule of hydrogen chloride is composed of a chlorine atom and a hydrogen atom. Hydrogen chloride is easily soluble in water, alcohol, and also in ether. Its aqueous solution is called hydrochloric acid, or hydrochloric acid.Under standard conditions (0 ° C, 101.325 kPa), 1 volume of water can dissolve about 500 volumes of hydrogen chloride[3-4]。
Hydrogen chloride is an important industrial chemical used to make dyes, spices, drugs, various chlorides and corrosion inhibitors.In addition, high-purity hydrogen chloride gas is widely used in the electronic industry. Electronic grade hydrogen chloride (purity ≥ 99.999%) is mainly used in processes such as gas phase polishing, epitaxy and etching in the microelectronics industry, and can also be used in fields such as metal smelting, photoconductive communication and scientific research[5-6]。
Hydrogen chloride, colorless, boiling point - 85 ° C, melting point - 114.2 ° C;The gas density is 1.639 kg/mthree(0 ° C, 0.1 MPa), gas specific gravity is 1.268 (0 ° C, air=1), molar volume is 22.25 L;The critical temperature is 51.4 ° C, the critical pressure is 8260 kPa, and the critical density is 420 kg/mthree[1-2]。Easily soluble in water, ethanol and ether, slightly soluble in other organic substances[7]Its aqueous solution is hydrochloric acid. Concentrated hydrochloric acid is volatile. Industrial hydrochloric acid is often yellowish, mainly because of the presence of ferric chloride.
Hydrogen chloride has a strong dipole, which is easy to form hydrogen bonds with other dipoles.Hydrogen chloride gas has a suffocating smell, strong irritation to upper respiratory tract, and corrosion to eyes, skin and mucous membrane.
appearance
Colorless hygroscopic gas
density
1.639 kg/mthree（0 °C，0.1 MPa）
melting point
-114.2 °C
boiling point
-85 °C
Solubility (water)
1: 500 (standard condition)[3], conversion is about 82 g/100 mL
Saturated vapor pressure
4225.6 kPa（20 °C）
chemical property
Announce
edit
Hydrogen chloride does not react with water. When encountering water in the air, it presents a fog shape with strong stability. It does not burn in the air, and the decomposition temperature is higher than 1500 ℃[7]。
Dry hydrogen chloride is very inactive in chemical properties. Pure hydrogen chloride does not react with most metals, but can react with alkali metals, aluminum, manganese, iron, copper, zinc, lead and other metals[2]。
The presence of hydrogen chloride can be tested with concentrated ammonia water, which reacts with hydrogen chloride to form white ammonium chloride particles.
NHthree+HCl = NHfourCl
Anhydrous HCl and SOthreeThe reaction can produce important chemical raw material HSO chlorosulfonic acidthreeCl[7]：
HCl+SOthree= HSOthreeCl
HCl can react with cyanide to release highly toxic HCN gas[7]。
Hydrogen chloride gas reacts with alkenes and alkynes to obtain CtwoHthreeCl、CtwoHfiveCl and CHtwo=CHCCl=CHtwoChemical products such as[7]：
HCl can also react with hydrocarbons to generate CtwoHfourCltwo、CsixHfiveCl、CtwoHClthreeChlorine hydrocarbon products, such as[7]：
Preparation method
Announce
edit
Laboratory preparation
The laboratory usually uses solid sodium chloride to react with concentrated sulfuric acid to produce hydrogen chloride gas. The principle is that hydrochloric acid is a volatile acid, and the nonvolatile acid is concentrated HtwoSOfourReact with its salt to produce volatile acid[8]。
Without heating or slightly heating, sodium bisulfate and hydrogen chloride are generated respectively.
NaCl+HtwoSOfour= NaHSOfour+HCl↑
Continue the reaction under the strong heat condition of 500 ° C to 600 ° C to generate hydrogen chloride and sodium sulfate.
NaHSOfour+NaCl = NatwoSOfour+HCl↑
The total chemical equation can be expressed as follows: (Note: HCl can only be added ↑ under heating and water shortage environment)
2NaCl+HtwoSOfour= NatwoSOfour+2HCl↑
Laboratory preparation
Industrial production
At present, hydrogen chloride is mainly produced by electrolysis.The technological process of producing hydrogen chloride by electrolysis is divided into two steps: the first step is to produce chlorine and hydrogen by electrolysis of saturated salt water;The second step is to ignite and burn hydrogen and chlorine in the combustion nozzle made of quartz to generate hydrogen chloride gas[9]。
In addition, higher concentrations of hydrogen chloride can be produced by the following two methods[1][6]。
1. Desorption method: use concentrated sulfuric acid to react with baked potassium chloride to generate high-purity hydrogen chloride gas, and then use the compressor to press it into the cylinder to obtain more than 99.9% purity hydrogen chloride gas.
2. Hydrochloric acid desorption method: place concentrated hydrochloric acid in the desorption tower for heating and desorption to produce more than 99.9% hydrogen chloride gas.
application area
Announce
edit
Hydrogen chloride is an important industrial chemical, which is widely used in rubber, medicine, organic and inorganic fields;High purity hydrogen chloride is also widely used in electronic industry.
Organic field
Chlorine containing products are directly prepared from hydrogen chloride.For example, ethylene is oxychlorinated with hydrogen chloride to produce 1,2-dichloroethane[7][10]；Preparation of epichlorohydrin from hydrogen chloride and glycerol[10]。
Chlorination of Aromatic Hydrocarbons with Hydrogen Chloride as Chlorine Source[10]。For example, anisole is chlorinated to prepare 2,4-dichloroanisole, p-nitroaniline is chlorinated to prepare 2,6-dichloro-p-nitroaniline, and naphthalene is chlorinated to prepare monochloronaphthalene, as shown in the following figure.
Organic field
Hydrogen chloride is used to hydrolyze starch to produce glucose and produce various organic agents;Pickling and mercerizing after treatment in bleaching and dyeing industry[7]。
Inorganic field
Anhydrous HCl and SOthreePreparation of important chemical raw material HSO chlorosulfonic acid by reactionthreeCl，HSOthreeCl can be used in pharmaceutical products, coatings, plastics and other fields[7]。
Hydrogen chloride is absorbed by water to produce hydrochloric acid.Hydrochloric acid is an important basic chemical raw material, which is often used in dye, medicine, food, printing and dyeing, leather and other industries[11]。
Preparation of Cl by electrolysis, direct oxidation and catalytic oxidationtwo, gaseous HCl is introduced into the aluminum chloride solution to prepare crystalline aluminum chloride (AlClthree·6HtwoO），And production of anhydrous magnesium chloride[12]。
electronics industry
Electronic grade hydrogen chloride (purity ≥ 99.999%) is mainly used for gas phase polishing, epitaxy, etching and other processes in the microelectronics industry[5]。
In addition, high-purity hydrogen chloride is also used for metal surface chemical treatment, laser gas mixture, film production and carbon fiber surface treatment[1]。
Storage method
Announce
edit
Hydrogen chloride is filled in a high-pressure liquefied gas cylinder with a nominal working pressure of 12.5 MPa by means of high-pressure liquefaction. The filling coefficient is not more than 0.57 Kg/L. The valve shall be made of acid resistant stainless steel[13]。
(1) The filling, storage and transportation of hydrogen chloride shall comply with the relevant provisions of the Regulations on Safety Supervision of Gas Cylinders, the Regulations on Safety Management of Dangerous Chemicals and the Regulations on Safety Supervision of Special Equipment.
(2) The filling of hydrogen chloride shall comply with the relevant provisions of GB14193.
(3) Hydrogen chloride products shall be stored in a cool, dry and ventilated warehouse. It is strictly prohibited to expose to the sun and keep away from heat sources.
Safety measures
Announce
edit
(1) Hydrogen chloride has strong irritation to eyes and respiratory tract mucosa.Acute poisoning can cause headache, dyspnea, pulmonary edema and other symptoms;Chronic poisoning can cause chronic bronchitis, gastric dysfunction, tooth erosion and other characteristics.Therefore, pay attention to safety during operation and use, and wear protective equipment.
(2) Hydrogen chloride is a nonflammable gas, but it will react with active metals and generate hydrogen, which is a potential fire hazard.In case of open fire or high temperature, the internal pressure of bottled hydrogen chloride will increase and there is a danger of bursting.Dry powder, carbon dioxide, water or conventional foam can be used to extinguish the fire.
(3) Skin contact: immediately take off the contaminated clothes and wash them with a large amount of flowing water; eye contact: immediately lift the eyelids and wash them thoroughly with a large amount of flowing water or physiological saline;Inhalation: quickly leave the site to a place with fresh air to keep breathing smooth.Seek medical advice in serious cases.
(4) Hydrogen chloride is non corrosive, but it is highly corrosive when encountering water.It is harmful to the environment, and special attention should be paid to water pollution.
(5) Store in a cool and ventilated warehouse.The warehouse area shall be equipped with leakage emergency treatment equipment and fire-fighting equipment.
(6) Maximum allowable concentration: China (MAC) 15 mg/mthree。[5]
