The reaction of carbon with the metals at high temperaturahpoluchayutsya carbides.For example, calcium carbide: Ca + 2C → CaC2.Of all carbides it has great practical significance.Net CaC2 - well crystallized solid, colorless crystals are formed by ions of Ca2 + and C2-.His other names - acetylide calcium or calcium carbide.The molar mass equal to 64.1 g / mol.It is non-volatile and not soluble in any known solvent and decomposed by water.Its density is 2.22 g / cc.Melting point equals 2160 ° C and the boiling - 2300 ° C.According to the impact on the body is a substance extremely dangerous (1st class of danger).
first calcium acetylide was prepared in 1862 by the German chemist Friedrich Wohler when heated with carbon alloy of zinc and calcium.He also described the reaction of calcium carbide with H2O.Even with its next (for example, with atmospheric moisture) calcium carbide reacts vigorously with release of large amounts of heat.But in case of lack of water may occur self-ignition of the resulting acetylene.Calcium carbide vigorously reacts with diluted inorganic acids and aqueous alkaline solutions.This also is an allocation of acetylene.As a strong reducing agent, CaC2 able to restore all the metal oxides to carbides or pure metals.
Getting calcium carbide is more convenient not from the calcium and its oxide.At high temperatures (2000 to 2300 ° C) is its recovery.The metal and carbon are connected: 3C → CaO + CO ↑ + CaC2.The process takes place in an electric arc furnace, which glows a mixture of quicklime and coke or anthracite.The crude product is colored, has a grayish color, because it contains impurities in the form of free carbon monoxide as well as sulfide, calcium phosphide and other chemical compounds.Mass fraction CaC2 it is 80-85%.
The interaction of carbides with water or metal stands, or acetylene.According to the second embodiment reacts with water the calcium carbide.Acetylene resulting reaction that has industrial importance: CaC2 + 2H2O → C2H2 + Ca (OH) 2, is a technical and has an unpleasant odor, because it contains a number of impurities (NH3, H2S, PH3, etc.).Although in pure form, it is a colorless gas with a characteristic odor rather weak, and it is quite soluble in water.It has great significance for calcium cyanamide (a raw material in the production of cyanide, or used as a fertilizer) carbide by reacting it with nitrogen at the reaction equation: N2 + CaC2 → CaCN2 + C.
Last CaC2 widely used carbide lamps, where he served as a source of acetylene flame.Currently, the use of such a light source is limited mainly potholing, it is also used in buoys and lighthouses.Other important areas of application CaC2 - are chemical technology, where it is the raw material.For example, in the manufacture of organic synthesis products, chief among them is the synthetic rubber.Also obtained from calcium carbide, acetylene black, vinyl chloride, vinyl acetic acid, acrylonitrile, ethylene, acetone, synthetic resins, styrene.The steel is used for deoxidization and desulfurization metals (reduction of oxygen and sulfur, respectively).Calcium carbide is used to produce a plant growth regulator, a carbide powder reagent (acetylene welding).
every ton CaC2 requires about 3000 kW / h of electricity.Therefore it is justified by the presence of low prices.Overall, however, world production of calcium carbide is growing.If in the 70s of the previous century annually produce up to 5 million tons, in this century the number has grown by about half.In China, the production of acetylene by calcium carbide is the main source of raw materials for the chemical industry, in particular for the production of polyvinyl chloride.Production of acetylene from its raw materials more economically than using imported oil.Therefore, its production in China is increasing.In 2005, it reached 8.94 million tons, and has a real opportunity to produce 17 million tons.
Unlike China, the US, Europe and Japan, consumption of calcium carbide, tend to decline.The level of its production in the US in the 90s was of 236 thousand tons per year.In our country, calcium carbide produced by the specifications set forth in ISO 1460-81.Its main customers - it is Ukraine, Uzbekistan, Romania and Slovakia.Because of the high energy consumption of the product, and due to rising prices for electricity consumption of calcium acetylide in Russia and exporting countries has fallen by half.
