Aromatic compounds production from alkanes

In terms of the individual compounds found in the condensable products, as with conventional pyrolysis, a-alkenes alkanes and dialkenes were the most abundant compounds. A large number of other aliphatic and aromatic compounds ranging from C3 to approximately 55 were also found, including methylcyclopentene, benzene, cyclohexene, toluene, ethylbenzene, xylene, propylbenzene and methyl-ethylbenzene. The analysis also showed that the condensables obtained at 500 and 700°C, although possessing similar levels of cleavage, showed important differences in the individual compounds present [85],... 

The products of the electrochemical perfluorination of aromatic and heteroaromatic compounds are the corresponding perfluorinated cyclic and heterocyclic alkanes.28 and also per-fluorinated derivatives of the heteroaromatic compounds. Perfluorocyclohexane is the principal product from the electrochemical fluorination of benzene and fluorobenzene. Chloro derivatives of perfluorocyclohexane are produced from chlorobenzenes. Anisoles give fully saturated per-fluoro ethers, together with cleavage products. Extensive cleavage is observed in the fluorination of benzenethiols. Chloropyridines, fluorocarbons and sulfur hexafluoride or nitrogen trifluoride are characteristic byproducts from the above scries of reactions. 

Crude oil, however, has almost completely replaced coal as a source of aromatics. Crude oil contains several percents of benzene, toluene, and xylenes and their cycloalkane precursors. The conversion efficiency for preparing toluene or xylenes from their precursors is nearly 100%. For benzene this efficiency is slightly lower. Moreover, alkanes are also transformed to aromatics during refining processes, allowing efficient production of simple aromatic compounds. 

Kerogens isolated from the Fig Tree cherts produced very complex mixtures of pyrolysis products, dominated by a series of methyl branched alkenes with each member of the series having 3 carbon atoms more than the previous member. At each carbon number a highly complex mixture of branched alkanes and alkenes plus various substituted aromatic compounds was found. The highly branched structures may have actually incorporated isoprenoids originally present in the Precambrian microorganisms (Philp Van DeMent, 1983)6>. 

The bromine solution is red the product that has the bromine atoms attached to carbon is colorless. Thus a reaction has taken place when there is a loss of color from the bromine solution and a colorless solution remains. Since alkanes have only single C—C bonds present, no reaction with bromine is observed the red color of the reagent would persist when added. Aromatic compounds resist addition reactions because of their aromaticity the possession of a closed loop (sextet) of electrons. These compounds react with bromine in the presence of a catalyst such as iron filings or aluminum chloride. 

A number of ILs are hydrophobic, yet they readily dissolve many organic molecules—with the exception of alkanes and alkylated aromatic compounds (e.g., toluene). Among such ILs we find [bmim][PFg], which forms triphasic mixtures with alkanes and water. This multiphasic behavior has decisive implications for clean synthesis. For example, transition-metal catalysts can be exclusively dissolved in the ionic liquid, thus allowing products and by-products to be separated from the ionic liquid by solvent extraction with either water or an organic solvent. This is advantageous when using expensive metal catalysts, as it enables both the ionic liquid and the catalyst to be recycled and reused. Alternatively, some volatile products can be separated from the IL by distillation, as it has negligible vapor pressure. 

Figure 11.5 shows that the functional group compositional analysis of the pyrolysis oil/waxes derived from the fixed-bed pyrolysis of PVC, PS and PET is very different from the polyalkene plastic pyrolysis oil/waxes. The spectra of the PVC pyrolysis oil/wax shows that the characteristic peaks of alkanes and alkenes are present as described for the polyalkene plastics. Since the PVC plastic polymer is based on a similar backbone structure to the polyalkene plastics, a similar degradation product oil/wax composition may be expected. However, the spectra for PVC in Figure 11.5 show that there are additional peaks in the region of 675-900 cm and 1575-1625 cm The presence of these peaks indicates the presence of mono-aromatic, polycyclic aromatic and substituted aromatic groups. Benzene has been identified as a major constituent in oils derived from the pyrolysis of PVC whilst other aromatic compounds identified included alkylated benzenes and naphthalene and other polycyclic aromatic hydrocarbons [19, 32, 39]... 

The basic sources of petrochemical synthesis are benzene and its homologues. The production of these compounds from petroleum is profitable. In 1996, the world requirements for benzene will grow up to 24-26 million tons per year. Non-oxidizing dehydrogenation of alkanes is a subject of intensive investigation. So, the selection and increase of the assortment of highly effective catalysts for the synthesis of olefins and aromatic hydrocarbons from alkanes are very important for development of this branch of industry. There are three main catalysts for non-oxidized dehydrogenation ... 

Many of the organic contaminants which were found in Lippe river water were also present in the source samples (see Table 3). The sewage effluent sample and the Seseke river showed the best accordance with the compound spectrum of the Lippe river. However, also in the two tributaries from the rural upper reaches of the river, numerous specific contaminants like 9-methylacridine (No. 8), alkyl phosphates (Nos. 31, 32) and chlorinated alkyl phosphates (Nos. 34, 36) appeared. In the effluent of a pharmaceutical plant, only a few Lippe river contaminants like n-alkanes (No. 1), naphthalene (No. 3), TXIB (No. 21) and caffeine (No. 67) were detected (see Table 3). Therein, mainly structural relatives of androstanone like 3p-hydroxy-5p-androstan-17-one, 3a-hydroxy-5p-androstan-17-one and androstan-50-3,17-dione were present. These compounds are probably by-products of the synthesis of hormone preparations. Some polycyclic aromatic compounds, halogenated compounds and terpenoids were not detected in the source samples (see the underlined compounds in Table 3) and probably have another origin. Representative sampling of various input sources have to be carried out to prove the origin of these compounds. Hexachlorobutadiene (No. 38) and bis(chloropropyl)ethers (No. 44) appear exclusively at the lower reaches of the Lippe river (see Table 1), downstream the chemical plants in Marl. They are attributed to inputs of the chlorochemical industry (see section 3.1). Hence, this suggests their input by an industrial point source. 

From these examples, it can be seen that almost invariably among isomers the n-alkane has the lowest viscosity at both 40°C and 100°C. The table below (Table 2.5) demonstrates that when aromatic compounds which have a total of three or more aromatic rings are hydrogenated, the perhydro- products are of lower viscosity than the aromatic types—this is particularly true when polyaromatic hydrocarbons are hydrotreated without cracking or isomerization. In contrast,... 

In geologic conditions nonpolar, hydrophobic substances under consideration, depending on pressure and temperature are capable of changing their phase state and can be gaseous, liquid or even solid. In gas state they form underground gas whose composition is dominated by such components as CH, more rarely and very rarely CO. Liquid nonpolar substances are mobile solutions (crude oil, oil products, residual oil, etc.,) whose composition is dominated by complex non-volatile organic compounds, namely, liquid alkanes (from pentane to heptadecane), almost all naphthenes, numerous aromatic hydrocarbons (benzene, toluene, isopropyl benzene, etc.), which in pure form may have melting temperature below 0 °C. 

The employment of suitable organic solvents, such as acetonitrile and acetic acid, with oxidation-resistant supporting electrolytes permits the anodic formation of reactive radical cations from many organic materials. Most aromatic compounds and olefins, as well as those alkanes which have particularly weak C—H bonds, are oxidised in acetonitrile containing fluoroborate or hexafluorophosphate electro-lytes. °" 2 Some aromatic radical cations can be further oxidised to dications within the available potential range. Radical cations in general either deprotonate or attack nucleophiles present in the medium reactions with pyridine, methanol, water, cyanide ion, acetate ion or acetonitrile itself produce addition or substitution products. The complete reactions involve a second electron transfer and coupled chemical... 

Recent advances have shown zeolites are effective in catalysing the direct conversion of synthesis gas to motor fuels. The MTO (methanol-to-olefins) process converts MeOH to C2-C4 alkenes and is also catalysed by ZSM-5. The development of a gallium-modified ZSM-5 catalyst (Ga-ZSM-5) has provided an efficient catalyst for the production of aromatic compounds from mixtures of C3 and C4 alkanes (commonly labelled LPG). 

A typical composition of a light oil product from the high temperature (900°C [1650°F]) of coal might contain (Table 13.7) benzene, toluene, and the xylenes, as well as alkanes (e.g., n-hexane), cycloalkanes (e.g., cyclohexane), olefins (e.g., n-hexene), and a wide variety of various aromatic compounds. 

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