| Industrial inorganic chemistry includes subdivisions of | | | | controls on emissions. Sulfuric acid is manufactured as: |
| the chemical industry that manufacture inorganic | | | | 2SO2 + O2 → 2SO3 ; SO3 + H2O → H2SO4 |
| products on a large scale such as the heavy | | | | Since the reaction of sulfur with dry air is exothermic, |
| inorganics (chlor-alkalis, sulfuric acid, sulfates) and | | | | the sulfur dioxide must be cooled to remove excess |
| fertilizers (potassium, nitrogen, and phosphorus | | | | heat and avoid reversal of the reaction. Most plants |
| products) as well as segments of fine chemicals that | | | | use reactors with various stages in order to cool the |
| are used to produce high purity inorganics on a much | | | | stream for the catalytic step. Conversion by a |
| smaller scale. Among these are reagents and raw | | | | vanadium pentoxide catalyst deposited on a silicate |
| materials used in high-tech industries, pharmaceuticals | | | | support is the critical step in the process, in which the |
| or electronics, for example, as well as in the | | | | gaseous stream is passed over successive layers of |
| preparation of inorganic specialties such as catalysts, | | | | catalyst. The gas mixture is then passed through an |
| pigments, and propellants. Metals are chemicals in a | | | | absorption tower. Oleum, the product, is a |
| certain sense. They are manufactured from ores and | | | | concentrated solution of sulfuric acid containing excess |
| purified by many of the same processes as those | | | | sulfur trioxide. |
| used in the manufacture of inorganics. However, if | | | | As an inexpensive source of acid, a large amount of |
| they are commercialized as alloys or in their pure form | | | | the sulfuric acid that is produced is used for the |
| such as iron, lead, copper, or tungsten, they are | | | | manufacture of other mineral acids. It is also used to |
| considered products of the metallurgical not chemical | | | | produce sulfates, such as ammonium sulfate (a |
| industry. | | | | low-grade fertilizer), sodium sulfate (used in the |
| The chemical industry adds value to raw materials by | | | | production of paper), and aluminum sulfate (used in |
| transforming them into the chemicals required for the | | | | water treatment), as well as organic sulfates (used as |
| manufacture of consumer products. Since there are | | | | surfactants). Sulfuric acid is also a good catalyst for |
| usually several different processes that can be used | | | | many reactions, including the transformation of ethanol |
| for this purpose, the chemical industry is associated | | | | into ethylene or ethyl ether. |
| with intense competition for new markets. It is made | | | | In general, chemicals containing nitrogen are |
| up of companies of different sizes, including several | | | | manufactured from ammonia produced by the Haber |
| giants that are engaged in the transformation of some | | | | process. Since molecular nitrogen is inert, its reaction |
| very basic raw materials into final products, as well as | | | | with hydrogen requires very severe conditions and a |
| medium-size or small companies that concentrate on | | | | catalyst. An iron catalyst is used. High pressure favors |
| very few of these steps. The closer to the raw | | | | the formation of products, but an increase in |
| material, the larger the scale of operations; such | | | | temperature will shift the equilibrium in the opposite |
| "heavy" inorganic chemicals are usually manufactured | | | | direction. Plants will thus operate under conditions that |
| by continuous processes. At the other extreme in | | | | represent the most favorable balance between |
| terms of scale are the firms that manufacture | | | | operating costs and capital investment. Energy |
| "specialties," mostly in batch processes, from | | | | consumption is very high, and its cost is an important |
| "intermediates" that correspond to chemicals which | | | | component along with the starting materials. Nitrogen is |
| have already gone through several steps of synthesis | | | | easily obtained from air and hydrogen and can be |
| and purification. | | | | produced by the shift reaction: CO + H2O → CO2 + |
| Basic chemicals represent the starting point for the | | | | H2 or from hydrocarbon reforming: CH4 + 2H2O → |
| manufacture of inorganic industrial chemicals. They are | | | | CO2 + 4H2 |
| usually one step away from the raw materials and are | | | | Further stages are required to assure conversion and |
| produced on a very large scale employing continuous | | | | to remove carbon dioxide or carbon monoxide from |
| processes. The unit price of these products is relatively | | | | the gas mixture. A mixture of ammonia and synthesis |
| low, and producing them cheaply and efficiently is a | | | | gas (CO + H2) results from the reaction with nitrogen |
| major concern for the companies that manufacture | | | | so the two must be separated and the synthesis gas |
| them. Sulfur, nitrogen, phosphorus, and chloralkali | | | | recycled. |
| industries are the main producers of basic inorganic | | | | Most of the ammonia that is produced is employed as |
| chemicals, and they will often sell them to other | | | | fertilizer or used to manufacture other fertilizers, such |
| industries as well as using them in the manufacture of | | | | as urea, ammonium sulfate, ammonium nitrate, or |
| their own end-products. The basic principles for their | | | | diammonium hydrogen phosphate. Ammonia is also |
| production and major uses are indicated here for each | | | | used in the Solvay process, and it is a starting material |
| of these industries. | | | | for the manufacture of cyanides and nitriles (which are |
| Inorganic chemicals produced on an industrial scale can | | | | used to make polymers such as nylon and acrylics) as |
| be easily identified. Many of today's large companies | | | | well as aromatic compounds containing nitrogen, such |
| started as producers of inorganics, but as coal—and | | | | as pyridine and aniline. The other source of nitrogen |
| especially petroleum—became important sources of | | | | compounds in the chemical industry is nitric acid, |
| raw materials; they were integrated into the product | | | | obtained from the oxidation of ammonia: 4NH3 + 5O2 |
| chain. Inorganic chemicals such as chlorine are used in | | | | → 4NO + 6H2O; 3NO + 3/2O2 → 3NO2 and |
| the manufacturing of several chlorides, including PVC | | | | 3NO2 + H2O → 2HNO3 + NO |
| and hydrochloric acid. | | | | The first reaction is run over platinum-rhodium catalysts |
| There are many different sources of raw materials | | | | at around 900°C (1,652°F). In the second and third |
| for the manufacture of inorganic chemicals. Very few | | | | stages, a mixture of nitric oxide and air circulates |
| of them are found in their elemental form. Sulfur is a | | | | through condensers, where it is partially oxidized. The |
| notable exception. It occurs in underground deposits | | | | nitrogen dioxide is absorbed in a tower, and nitric acid |
| and can be brought to the surface by compressed air | | | | sinks to the bottom. Nitric acid is mainly used to make |
| after it is melted by superheated steam. However, | | | | ammonium nitrate, most of it for fertilizer although it |
| increasing quantities of sulfur are recovered from | | | | also goes into the production of explosives. Nitration is |
| petroleum and natural gas (where they occur as | | | | used to manufacture explosives such as nitroglycerine |
| impurities). Air contains molecular nitrogen and oxygen. | | | | and trinitrotoluene (TNT) as well as many important |
| They may be separated by liquefaction and fractional | | | | chemical intermediates used in the pharmaceutical and |
| distillation along with inert gases, especially argon. Salt | | | | dyestuff industries. |
| or brine can be used as sources of chlorine and | | | | The world's major source of phosphorus is apatite, a |
| sometimes bromine, sodium hydroxide, and sodium | | | | class of phosphate minerals. Commercially, the most |
| carbonate, whereas metals such as iron, aluminum, | | | | important is fluoroapatite, a calcium phosphate that |
| copper, or titanium as well as phosphors, potassium, | | | | contains fluorine. This fluorine must be removed for the |
| calcium, and fluorine are obtained from mineral ores. | | | | manufacture of phosphoric acid, but it also can be |
| Saltpeter was once an important source of nitrogen | | | | used to produce hydrofluoric acid and fluorinated |
| compounds, but today most ammonia and nitrates are | | | | compounds. Phosphoric acid is the starting material for |
| produced synthetically from nitrogen gas in the air. | | | | most of the phosphates that are produced industrially. |
| Recovery and recycling provide increasing amounts of | | | | It is obtained from the reaction of the apatite mineral |
| some metals. As environmental concerns increase, | | | | with sulfuric acid. Silica is present in the mineral as an |
| these operations will probably become an important | | | | impurity, and it reacts with hydrofluoric acid to yield |
| source of materials used in the manufacture of certain | | | | silicon tetrafluoride, which can be converted to |
| inorganic chemicals. | | | | fluorosilicic acid, an important source of fluorine. More |
| The origins of the chemical industry can be traced to | | | | than half of the phosphoric acid that is produced by |
| the Industrial Revolution. Sulfuric acid and sodium | | | | the reaction of phosphates with sulfuric acid is |
| carbonate were among the first industrial chemicals. | | | | converted directly to sodium or ammonium phosphates |
| "Oil of vitriol" (as the former was known) played an | | | | to be used as fertilizer; thus, purity is not a concern. |
| important role in the manipulation of metals, but its | | | | For products that require high purity, such as |
| production on an industrial scale required the | | | | detergents and foodstuffs, phosphoric acid is produced |
| development of materials that would resist attack. | | | | from elemental phosphorus (at about four times the |
| Sodium carbonate was obtained in its anhydrous form, | | | | cost). An electric furnace operating at |
| "soda ash," from vegetable material until the quantities | | | | 1,400–1,500°C (2,552–2,732°F) is used to form |
| produced could no longer meet the rapidly expanding | | | | a molten mass of apatite and silica that reacts with |
| needs of manufacturers of glass, soap, and textiles. | | | | coke and reduces the phosphate mineral: |
| This led the Royal Academy of Sciences of Paris, in | | | | 2Ca3 (PO4)2 + 6SiO2 + 10C → P4 + 6CaSiO3 + |
| 1775, to establish a contest for the discovery of a | | | | 10CO |
| process based on an abundant raw material, sodium | | | | Concentrating phosphoric acid leads to polyphosphoric |
| chloride, and to Nicolas Leblanc's method for the | | | | acid, a mixture of several polymeric species, a good |
| preparation of soda by converting salt into sulfate: | | | | catalyst and dehydrating agent. Polyphosphate salts |
| 2NaCl + H2SO4 → Na2SO4 + 2HCl; followed by | | | | are used as water softeners in detergents or as |
| conversion of the sulfate to soda with charcoal and | | | | buffers in food. Small quantities of elemental |
| chalk: Na2SO4 + 2C + CaCO3 → Na2CO3 + CaS | | | | phosphorus are used to make matches, and |
| + 2CO2 | | | | phosphorus halides to prepare specialty chemicals for |
| Although he did not win the prize, Leblanc's process is | | | | the pharmaceutical and agrochemical industries. |
| associated with the birth of industrial chemistry. The | | | | Industries producing chlorine, sodium hydroxide (also |
| industrial production of chemicals was usually based on | | | | known as caustic soda), sodium carbonate (or soda |
| running reactions that were known to yield the desired | | | | ash) and its derivatives and compounds based on |
| products on much larger scales. Success in these | | | | calcium oxide (or lime) are usually included under the |
| endeavors lay much more in the experience and skill | | | | chloralkali category. As both sodium hydroxide and |
| of their practitioners than the application of solid | | | | chlorine have a common raw material, sodium chloride, |
| chemical principles. This led to serious problems of | | | | they are produced in quantities that reflect their equal |
| control and the generation of noxious by-products. The | | | | molar ratio, irrespective of the market for either |
| introduction of the Leblanc process in the northwest of | | | | product. Since they are produced by electrolysis, they |
| England led to a general public outcry against the dark | | | | require a cheap source of brine and electricity: |
| and corrosive smoke that covered the surrounding | | | | 2NaCl + 2H2O → 2NaOH + Cl2 + H2 |
| countryside. The Alkali Act, passed in response in 1863, | | | | Most processes are based on the electrolysis of a |
| represents the first legislation that established emission | | | | sodium chloride solution, but some plants operate with |
| standards. | | | | the molten salt. Three different cell types are used in |
| Sulfuric acid was an essential chemical for dyers, | | | | electrolysis in water: mercury cells, diaphragm cells, and |
| bleachers, and alkali manufacturers. Its production on a | | | | membrane cells. Membrane cells are replacing the |
| large scale required the development of lead-lined | | | | other two types in modern units, but it may not be |
| chambers that could resist the vapors which were | | | | economically feasible to convert older plants. |
| formed when sulfur was burned with nitrates: | | | | Sodium hydroxide and sodium carbonate are |
| SO2 + NO2 + H2O → H2SO4 + NO, and NO + 1 | | | | alternative sources of alkali, and their use has followed |
| 2O2 → NO2 | | | | the availability of raw materials as well as the |
| This process was wasteful and emitted corrosive | | | | efficiency of processes developed for their production. |
| gases. It improved only in the mid-nineteenth century | | | | Both require sodium chloride and energy and, if |
| when towers to recycle the gases were finally | | | | limestone deposits are also available, sodium |
| introduced. The transportation of sulfuric acid was | | | | carbonate may be produced by the Solvay process. |
| dangerous, and alkali manufacturers tended to produce | | | | Limestone consists mainly of calcium carbonate and |
| their own as a result. This marked the beginning of the | | | | can be used to produce calcium oxide (or quicklime) |
| diversification and vertical integration that are | | | | and calcium hydroxide (or slaked lime); the oxide may |
| characteristic of the chemical industry. Sulfuric acid | | | | be obtained by heating (1,200–1,500 ° C or |
| was also used in the manufacture of | | | | 2,192–2,732 ° F) limestone, while the hydroxide, |
| superphosphates, which were produced as fertilizers | | | | which is more convenient to handle, is obtained by |
| on a large scale by the mid-nineteenth century. By that | | | | adding water to the oxide: CaO + H2O → Ca(OH)2 |
| time, a solution was found for the complex engineering | | | | Its principal use is in steelmaking, but it also goes into |
| problems that had hampered the use of the alternative | | | | the manufacture of chemicals, water treatment, and |
| process to produce soda: | | | | pollution control. In the Solvay process, calcium |
| NH3 + H2O + CO2 → NH4HCO3 | | | | carbonate and sodium chloride are used to produce |
| NaCl + NH4HCO3 → NaHCO3 + NH4Cl | | | | calcium chloride and sodium carbonate with ammonia |
| 2 NaHCO3 → Na2CO3 + H2O + CO2 | | | | (which is recycled) as a medium for dissolving and |
| Ernest Solvay, a Belgian chemist, designed a tower in | | | | carbonating the sodium chloride and calcium hydroxide |
| which carbon dioxide reacted efficiently with solid salts. | | | | for precipitating calcium chloride from the solution. |
| The Solvay process had enormous advantages over | | | | As sodium carbonate may be mined directly, its use |
| the Leblanc process: It did not generate as much | | | | may be preferred over a manufactured product. It is |
| waste and pollution; its raw materials, brine and | | | | used mainly in the glass industry. Sodium silicates may |
| ammonia, were readily available (the latter from | | | | be derived from sodium carbonate and in their finely |
| gasworks); less fuel was used, and no sulfur or nitrate | | | | divided form, silica gel, may be used in detergents and |
| was involved. In spite of its higher capital costs, it was | | | | soaps. Sodium hydroxide has many different uses in |
| rapidly adopted and soon became the major source | | | | the chemical industry. Considerable amounts are used |
| of alkali. | | | | in the manufacture of paper and to make sodium |
| Another major process used in the manufacture of | | | | hypochlorite for use in disinfectants and bleaches. |
| inorganic chemicals is the catalytic conversion of | | | | Chlorine is also used to produce vinyl chloride, the |
| nitrogen and hydrogen to ammonia. The German | | | | starting material for the manufacture of polyvinyl |
| chemist Fritz Haber first synthesized ammonia from | | | | chloride (PVC), and in water purification. Hydrochloric |
| nitrogen and hydrogen in 1909. Four years later, | | | | acid may be prepared by the direct reaction of |
| together with another German, Carl Bosch, he modified | | | | chlorine and hydrogen gas or by the reaction of |
| the process for the commercial production of | | | | sodium chloride and sulfuric acid. It is used as a |
| ammonia. The Haber (or Haber–Bosch) process | | | | chlorinating agent for metals and organic compounds. In |
| represented a technological breakthrough since it | | | | certain regions of the world, there are salt deposits or |
| required a very specialized plant to handle gases at | | | | brines that have been enriched by bromine. |
| high pressures and temperatures. | | | | Commercially, bromine may be extracted by treating |
| Sulfuric acid has long been the chemical that is | | | | the brines with chlorine and removing it by steam. |
| manufactured in the largest quantities on a world scale. | | | | Bromine is used in water disinfection; bleaching fibers |
| Its production is often linked to a country's stage of | | | | and silk; and in the manufacture of medicinal bromine |
| development, owing to the large number of | | | | compounds and dyestuffs. |
| transformation processes in which it is used. Sulfuric | | | | Titanium dioxide is by far the most important titanium |
| acid is manufactured from elemental sulfur. Mining was | | | | compound. It can be purified by dissolving in sulfuric |
| the main source for this element, which was obtained | | | | acid and precipitating the impurities. The solution is then |
| from sulfide-containing ores or in very pure form from | | | | hydrolyzed, washed, and calcinated. Alternatively, |
| underground deposits by the Frasch process (injection | | | | ground rutile is chlorinated in the presence of carbon |
| of superheated steam and air into drillings and the | | | | and the resulting titanium tetrachloride is burned in |
| separation of the mixture that rises to the surface). | | | | oxygen to produce the chloride. Titanium dioxide is |
| The large-scale consumption of petroleum and natural | | | | found in nature in three crystal forms: anastase, |
| gas has changed this scenario since sulfur occurs as | | | | brookite, and rutile. Its extreme whiteness and |
| an impurity in most fossil fuels and must be removed | | | | brightness and its high index of refraction are |
| before the fuels are processed. These fuels are | | | | responsible for its widespread use as a white pigment |
| presently the main source of sulfur, and their relative | | | | in paints, lacquers, paper, floor covering, plastics, |
| importance tends to increase with more rigorous | | | | rubbers, textiles, ceramics, and cosmetics. |