Olefin chemical processes

For reviews of the photobehavior of alkenes in the gas phase, see (a) Collin, G. J., Ring contraction of cyclic olefins chemical processes specific to electronically excited states /. Photochem., 38, 205, 1987 (b) Collin, G.J., Photochemistry of simple olefins chemistry of electronic excited states or hot ground state Adv. Photochem., 14, 135, 1988. 

CoUin, G.J. and De Mare, G.R., Ring contraction of cyclic olefins chemical processes specific to electronically excited states /. Photochem., 38, 205-215, 1987. 

For chemical processes, some examples are the elimination of aromatics by sulfonation, the elimination of olefins by bromine addition on the double bond (bromine number), the elimination of conjugated diolefins as in the case of the maleic anhydride value (MAV), and the extraction of bases or acids by contact with aqueous acidic or basic solutions. 

The aromatic hydrocarbons are used mainly as solvents and as feedstock chemicals for chemical processes that produce other valuable chemicals. With regard to cyclical hydrocarbons, the aromatic hydrocarbons are the only compounds discussed. These compounds all have the six-carbon benzene ring as a base, but there are also three-, four-, five-, and seven-carbon rings. These materials will be considered as we examine their occurrence as hazardous materials. After the alkanes, the aromatics are the next most common chemicals shipped and used in commerce. The short-chain olefins (alkenes) such as ethylene and propylene may be shipped in larger quantities because of their use as monomers, but for sheer numbers of different compounds, the aromatics will surpass even the alkanes in number, although not in volume. 

This process seems much simpler than the Ziegler process, and you may wonder why it has not crowded Ziegler out. The problem is the olefin feed. Where do you get a ready supply of olefins the right size to feed to the process The answer is you have to malce them, and therein lies the rub. Normal paraffins from petroleum waxes or other chemical processes provide the feedstock to a two-step process, chlorination and dehydrochlorination, which produces an olefin corresponding to the paraffin. 

Since the discovery of olefin metathesis by Banks and Bailey in the 1960s using alumina supported Mo(CO)6 [64] this reaction has become key in both petrochemical and fine chemical processes. While the petrochemical industry has relied for more than three decades on the Lummus process, employing WO3 supported... 

The formation of epoxides is synthetically a very important transformation. The indirect epoxidation of olefins (see Eq. 7) in the presence of electrogenerated chlorine (or bromine) [95] is a commercial process in which chlorine is recycled and not part of the product. The products such as propylene oxide are key intermediates in many further chemical processes. 

In the chemical process industries, nickel, cobalt, platinum, palladium, and mixtures containing potassium, chromium, copper, aluminum, and other metals are used in very large-scale dehydrogenation processes. For example, acetone (6 billion pounds per year) is made from isopropyl alcohol styrene (over 2 billion pounds per year) is made from ethylbenzene. The dehydrogenation of n-paraffins yields detergent alkylates and n-olefins. The catalytic use of rhenium for selective dehydrogenation has increased in recent years. Dehydrogenation is one of the most commonly practiced of ihe chemical unit processes. 

If, however, the same reaction is attempted in methanolic solution, no olefin oxidative cleavage is detected, and solvent oxidation dominates the observed chemical process. Presumably, the polar solvent preferentially binds to the oxide surface, effectively negating the adsorption of the less polar hydrocarbon. The observed reactivity is then restricted to molecules held at the surface, i.e., to solvent oxidation. 

The use of solar energy in chemical processing has also been investigated. Studies describe, for example, the cycloaddition reaction of a carbonyl compound to an olefin carried out in a solar furnace reactor (91) or oxidation of 4-chlorophenol in a solar-powered liber-optic cable reactor (92). The concept of using solar light for the synthesis of e-caprolactam was evaluated, and it was shown that the return on investment was better than for the conventional technology (93). Solar reactors can also be used advantageously in water treatment plants (94). 

From the authors point of view, introduction of this elementary stage to mechanisms of saturated hydrocarbon gas-phase oxidation [26] makes clearer the mechanisms of such complex chemical processes, especially at olefin formation with the same number of carbon atoms as in the initial hydrocarbon. 

Some other natural compounds have been transformed for their use in the synthesis of polymers via olefin metathesis processes. As mentioned in the introduction, furans, which are obtained from carbohydrates, are perfect precursors of monomers for ROMP via simple Diels-Alder cycloadditions (n) (Scheme 25) [26]. In this regard, the first example of the ROMP of 7-oxabicyclo[2.2.1]hept-5-ene derivatives was reported by Novak and Grubbs in 1988 using ruthenium- and osmium-based catalysts [186]. The number of examples of ROMP with monomers with this generic structure is vast, and it is out of the scope of this chapter to cover all of them. However, it is worth mentioning here the great potential of a renewable platform chemical like furan (and derived compounds), which gives access to such a variety of monomers. 

The interaction of unsaturated molecules, for example olefins and acetylenes, with transition metals is of paramount importance for a variety of chemical processes. Included among such processes are stereospecific polymerization of olefin monomers, the production of alcohols and aldehydes in the hydroformylation reaction, hydrogenation reactions, cyclo-propanation, isomerizations, hydrocyanation, and many other reactions. 

It is prepared by passing HF and S03 in fluorosulfonic acid which acts as a solvent as well as heat transfer media. Over 20,000 metric tons of HSO3F are produced per year. It is mostly used as catalyst in the alkylation of branch chain paraffins [26-29], in the polymerization [30-31]. Fluorosulfonic acid is a very strong acid and when added to olefins, it remarkably increases the acidity of the system and enhances its catalytic activity similar to SbF5, TaFs and NbF5 [32-35], It is also used in a chemical process to produce SiF4 [36,37] and BF3 [38],... 

Some olefins can be manufactured industrially by various chemical processes usually employing removal reactions on functional saturated compounds. These specifically involve the dehydration of alcohols and the dehydrochlorination of chlorinated derivatives. 

The world petrochemical industry is surveyed annually in the Oil Gas Journal as the Ethylene Report. This is a useful source of country production, individual steam crackers (including ownership) and the feedstock used. Since 2006 US olefins and the US natural gas liquid supply and prices are each reviewed twice per year by Lippe. Weissermel and Arpe have provided an excellent description of many technologies and approaches to chemical synthesis in the chemical process industry. 

The sorption of H2 on metals which can take place at both high and low temperatures (for example, —180 to 500°C) is accompanied by dissociation of the H2 to II atoms and is undoubtedly a chemical process of metal hydride formation on the metal surface. The sorption of O2 on charcoal, CO, and N2 on transition metals and of olefins on metals are all accompanied by heat evolutions in the neighborhood of 30 to 100 Kcab and are undoubtedly better viewed as chemical reactions than as loose solvation. For these reasons we shall direct our attention to the process of chemisorption in discussing catalytic reactions. 

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