Aromatic hydrocarbons, very high pressure

Aust RB, Bentley WH, Drickamer HG (1964) Behavior of fused-ring aromatic hydrocarbons at very high pressure. J Chem Phys 41 1856-1864... 

A very simple and effective method of increasing the intensity of Ti So transitions by several orders of magnitude was introduced by Evans 53-s5) Either the pure liquid or concentrated solutions of an aromatic hydrocarbon in chloroform were saturated with oxygen or nitric oxid at high pressures. The newly appearing absorption bands are proportional to the applied gas pressures from 0—100 atm. The So absorptions are in general well structured and the posi-... 

Figure 8.8—Electrochromatographic separation of aromatic hydrocarbons. The movement of the mobile phase is strictly due to the electro-osmotic flow. In contrast to HPLC, no pressure is exerted at the head of the column. Separations can be carried out with a very high efficiency.

Alkylation is a very broad reaction type and it can, depending on the nature of the alkylating agent, proceed either as a substitution or as an addition reaction. The alkylation by substitution of, for example, aromatic hydrocarbons, phenols or amines is based on the reaction with alkyl halides or alcohols. Some evidence indicates that, at least partly, the alkylation proceeds through the intermediate formation of alkenes from the alkylating agent when the reaction is conducted at atmospheric pressure and at high temperature. 

In catalytic reforming the naphtha is processed to obtain high octane gasoline for motor fuel and aromatics for petrochemical industry. The monometallic Pt/Al203 has been replaced by a number of bimetallics like Pt-Ir, Pt-Re, Pt-Sn etc. because of the superior activity, stability and selectivity for C5 hydrocarbons. Pt-Sn/Al203 has become more attractive in recent years because it allows operations at very low pressures and is more selective for aromatics and hydrogen (1). Tin, when incorporated with Pt on an acidic alumina support promotes aromatization and suppresses hydrogenolysis (2,3). 

Most OPPs are slightly water-soluble, have a high and a low vapor pressure. Some are very miscible with water (trichlorfon, vamidothion, mevinphos, monocrotophos, omethoate, oxydeme-ton-methyl, phosphamidon). Most, with the exception of dichlorvos, are of comparatively low volatility, and are all degraded by hydrolysis, yielding water-soluble products. Parathion, for example, is freely soluble in alcohol, esters, ethers, ketones, and aromatic hydrocarbons, but is almost insoluble in water (20 ppm), petroleum ether, kerosene, and spray oils. 

Nitro Compounds as Explosives.—Nitro compounds prepared from aromatic hydrocarbons and certain of their derivatives were very important explosives used in the recent war. The compounds differ markedly in the properties which are characteristic of explosives namely, (1) sensitiveness to shock, (2) explosive force, and (3) the velocity of the explosion through the substance. If (1) is very high the explosive can not be transported very safely (2) determines the amount of the explosive to be used if (3) is very high the pressure is developed to its maximum so suddenly that rupture of the gun in which it is used may take place. Substances which are very sensitive to shock are used as detonators or boosters a small amount of the material is exploded by the trigger and the explosive wave set up causes the explosion of the less sensitive material. Mercury fulminate, lead azide, Pb(Ns)2, and several nitro derivatives of aniline (see below) are used for this purpose. 

The direct conversion of hydrocarbons to diamond has also been demonstrated. C3 is the region where organic compounds such as anthracene, camphene, fluorene, pyrene, sucrose, polyethylene, adamantane, and paraffin wax have been converted to very fine diamonds under high pressure (about 1pm in size) (Wentorf [33]). Aliphatic compounds seem to work but compounds with aromatic rings and/or... 

An approach to VOC reduction is use of supercritical carbon dioxide as a component in a solvent mixture (216). The critical temperatin-e and pressure of CO2 are 31.3°C and 7.4 MPa (72.9 atm), respectively. Below that temperatin-e and above that pressure, CO2 is a supercritical fluid. Under these conditions, solvency properties of CO2 are similar to aromatic hydrocarbons. A very high solids coating and supercritical CO2 are metered into a proportioning spray gim in such a ratio as to reduce the viscosity to the level needed for proper atomization. Airless spray guns are used it has been found that the rapid evaporation of the CO2 as the coating leaves the orifice of the spray gun assists atomization. VOC emission reductions of 50% or more have been reported. 

Although the requirement for specialized high pressure equipment has limited its application, extraction with supercritical carbon dioxide maintained at temperatures and pressures above the critical point where separate liquid and vapor phases do not exist is a very effective means of extracting some organic analytes. Method 3561 is used to extract polycyclic aromatic hydrocarbons such as acenaphthene, benzo(a)py-rene, fluorene, and pyrene from solid samples using a relatively complicated three-step procedure. 

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