Sources of chemicals

Atypically, there are a few materials which occur in an elemental form. Perhaps the most notable example is sulphur, which occurs in underground deposits in areas such as Louisiana, Southern Italy and Poland. It can be brought to the surface using the Frasch process in which it is first melted by superheated steam and then forced to the surface by compressed air. This produces sulphur of high purity. Substantial quantities of sulphur are also removed and recovered from natural gas and crude oil (petroleum). This amounted to 24 million tonnes out of a total world sulphur production of 37 million tonnes in 1991, and clearly demonstrates the vast scale on which the oil and petrochemical industries operate since crude oil normally contains between 0.1 and 2.5% of sulphur, depending on its source. Desulphurization of flue gases from some U.K. power stations will be another source of sulphur in the future. Over 80% of all sulphur is converted into sulphuric acid, and approximately half of this is then used in fertilizer manufacture. 

A second example of the occurrence in nature of materials in elemental form is air, which may be physically separated into its component gases by liquefaction and fractional distillation. In this way substantial amounts of nitrogen and oxygen, plus small amounts of the inert gases argon, neon, krypton, and xenon are produced. A recent development has been the use of zeolites (p. 323) for carrying out this separation. 

In contrast to inorganic chemicals which, as we have already seen, are derived from many different sources, the multitude of commercially important organic compounds are essentially derived from a single source. Nowadays in excess of 90% (by tonnage) of all organic chemicals is obtained from crude oil (petroleum) and natural gas via petrochemical processes. This is a very 

A further reason to discontinue the use of fossil fuels for energy generation is that they produce mainly carbon dioxide and water by complete combustion. Because this has taken place on such an enormous scale over many years, the quantity of carbon dioxide released into the atmosphere has been very large indeed. Considerable concern has been expressed for the consequences of this. It has been suggested that as all this carbon dioxide diffuses into the earth s upper atmosphere it will reduce the amount of screening of the sun s rays, causing the so-called greenhouse effect. 

Clearly alternative energy sources to fossil fuels are now available if we have the will to use them, and we can confidently expect other alternatives to become available in the not too distant future. It is therefore essential that we retain our precious oil supplies for chemicals production. The statement that the last thing you should do with oil is burn it becomes more valid every year. It is interesting, and salutory, to note that as early as 1894 Mendeleyev (the Russian chemist who developed the Periodic Table) reported to his government that oil was too valuable a resource to be burned and should be preserved as a source of chemicals . 

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Two-Stage Resins. The ratio of formaldehyde to phenol is low enough to prevent the thermosetting reaction from occurring during manufacture of the resin. At this point the resin is termed novolac resin. Subsequently, hexamethylenetetramine is incorporated into the material to act as a source of chemical cross-links during the molding operation (and conversion to the thermoset or cured state). 

Coal is used ia industry both as a fuel and ia much lower volume as a source of chemicals. In this respect it is like petroleum and natural gas whose consumption also is heavily dominated by fuel use. Coal was once the principal feedstock for chemical production, but ia the 1950s it became more economical to obtain most industrial chemicals from petroleum and gas. Nevertheless, certain chemicals continue to be obtained from coal by traditional routes, and an interest in coal-based chemicals has been maintained in academic and industrial research laboratories. Much of the recent activity in coal conversion has been focused on production of synthetic fuels, but significant progress also has been made on use of coal as a chemical feedstock (see Coal CONVERSION processes). 

High Temperature Carbonization. When heated at temperatures in excess of 700°C (1290°F), low temperature chars lose their reactivity through devolatilization and also suffer a decrease in porosity. High temperature carbonization, at temperatures >900° C, is, therefore, employed for the production of coke (27). As for the low temperature processes, the tars produced in high temperature ovens are also sources of chemicals and chemical intemiediates (32). 

The substrates of catabolism—proteins, carbohydrates, and lipids—are good sources of chemical energy because the carbon atoms in these molecules are in a relatively reduced state (Figure 18.9). In the oxidative reactions of catabolism, reducing equivalents are released from these substrates, often in the form of hydride ions (a proton coupled with two electrons, H ). These hydride ions are transferred in enzymatic dehydrogenase reactions from the substrates... 

The periodicity in the oxidation state or valence shown by the elements was forcefully illustrated by Mendeleev in one of his early forms of the periodic system and this is shown in an extended form in Fig. 2.5 which incorporates more recent information. The predictive and interpolative powers of such a plot are obvious and have been a fruitful source of chemical experimentation for over a century. 

Among the techniques mentioned previously, XPS has the greatest impact on polymer surface analysis. A major additional source of chemical information from polymers comes from IR and Raman spectroscopy methods, These vibrational data can be obtained from the bulk and the surface region, although the information depth is much greater than with AES, XPS, or ISS. 

M—O I —(CH2)4 O C=0) has been suggested as another source of chemical interaction between the urethane and the metal counterface [51]. 

When crude oil is refined, some of the processes yield additional gaseous products. The C3 and C4 constituents differ from those released from crude oil or from NGLs, which are saturated hydrocarbons. Refinery gases are high in unsaturates, e.g. propane (propylene) and butane (butylenes). These unsaturated hydrocarbons are a valuable source of chemical process intermediates and enjoy a large market alongside naphtha. 

About eight gallons of coal tar are obtained from a ton of coal. Coal tars are very complex mixtures over 200 different carbon compounds have been isolated from them. While the great value of coal to mankind has been as a fuel, a source of energy, the many substances in coal gas and coal tar make coal also an important source of chemical raw materials. 

An overview of the use of hardwood and softwood is given in Figure 8.1 (B. Holmbom, 2009, private communication). As the schematic picture reveals, many possibilities exist for the use of wood - and biomass in general - as a source of chemicals. 

An external source of chemical energy must be available to drive the biosynthetic reactions... 

In brook trout (Salvelinus fontinalis), feces was the most important egestion route, and spawning was not an important source of chemical elimination of 2,3,7,8-TCDD (Nichols etal. 1998). However, Tietge etal. (1998) disagree and, using radioisotope techniques, show 39% maternal transfer of 2,3,7,8-TCDD to eggs in brook trout, and suggest the need for additional research in this area. 

NON-RULED MARKET ECONOMY AS A SOURCE OF CHEMICAL TERRORISM. AUTOMOTIVE FUEL QUALITY AND ENVIRONMENTAL SAFETY... 

Non-ruled Market Economy as a Source of Chemical Terrorism... 

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