Oxidation from alkyl benzenes

Surfactants can be produced from both petrochemical resources and/or renewable, mostly oleochemical, feedstocks. Crude oil and natural gas make up the first class while palm oil (+kernel oil), tallow and coconut oil are the most relevant representatives of the group of renewable resources. Though the worldwide supplies of crude oil and natural gas are limited—estimated in 1996 at 131 X 1091 and 77 X 109 m3, respectively [28]—it is not expected that this will cause concern in the coming decades or even until the next century. In this respect it should be stressed that surfactant products only represent 1.5% of all petrochemical uses. Regarding the petrochemically derived raw materials, the main starting products comprise ethylene, n-paraffins and benzene obtained from crude oil by industrial processes such as distillation, cracking and adsorption/desorption. The primary products are subsequently converted to a series of intermediates like a-olefins, oxo-alcohols, primary alcohols, ethylene oxide and alkyl benzenes, which are then further modified to yield the desired surfactants. 

The basic petrochemical feedstocks are ethylene and benzene which are converted to the surfactant intermediates ethylene oxide, linear alkyl benzene (LAB), and detergent alcohols. Oleochemical or natural surfactants are commonly derived from plant oils (coconut and pahn oils), from plant carbohydrates such as sorbitol, sucrose, and glucose or from animal fats such as tallow. 

The concentrations of volatile aromatics which occur in the environment are generally - in opposition to the concentrations of olefinic compounds - too low to be harmful for plants [5, 13]. In concentrations of more than 2% - as they may be found when sprayed as solvents for pesticides - volatile aromatics are, however, more ecotoxic than olefines and paraffines [13, 107]. Relatively critical are oxidants, which may be produced from alkylated benzenes in a similar way as from olefinic compounds [5, 13]. 

Styrene is manufactured by alkylating benzene with ethene followed by dehydrogenation, or from petroleum reformate coproduction with propylene oxide. Styrene is used almost exclusively for the manufacture of polymers, of which the most important are polystyrene, ABS plastics and styrene-butadiene rubber. U.S. production 1980 3 megatonnes. 

CYP2El s substrates are small molecular weight aromatic hydrocarbons or their methyl derivatives, as the enzyme s active site is relative small and restricted. In a recently published study from Lewis et al. (235) eight alkyl benzenes, which undergo oxidative metabolism via human CYP2E1, were used to... 

Molybdenum complexes are the most effective catalysts known for the selective epoxidation of olefins with alkyl hydroperoxides (210-212). Commonly known is the Arco or Halcon process for the large-scale manufacture of propylene oxide from propylene. This process uses t-BuOOH or ethyl benzene hydroperoxide (EBHP) as an oxidant and Mo(CO)6, for example, as a source of Mo. The Mo(CO)6 acts as a catalyst precursor, which is converted into a soluble active form by complexation with diols (3). Chemists have designed several supported versions of the catalysts for this epoxidation chemistry. A clear classification can be made on the basis of the nature of the support. 

Most important is the cumene process with an 80-85% share worldwide cumene (isopropylbenzene obtained from alkylation of benzene with propylene) is oxidized to the corresponding hydroperoxide which is decomposed to a mixture of phenol and acetone. In Japan the second most important process for acetone production is the direct oxidation of propylene with a 12% share. 

Carbonium ions can be generated at a variety of oxidation levels. The alkyl carbocation can be generated from alkyl halides by reaction with a Lewis acid (RCl + AICI3) or by protonation of alcohols or alkenes. The reaction of an alkyl halide and aluminium trichloride with an aromatic ring is known as the Friedel-Crafts alkylation. The order of stability of a carbocation is tertiary > secondary > primary. Since many alkylation processes are slower than rearrangements, a secondary or tertiary carbocation may be formed before aromatic substitution occurs. Alkylation of benzene with 1-chloropropane in the presence of aluminium trichloride at 35 °C for 5 hours gave a 2 3 mixture of n- and isopropylbenzene (Scheme 4.5). Since the alkylbenzenes such as toluene and the xylenes (dimethylbenzenes) are more electron rich than benzene itself, it is difficult to prevent polysubsiitution and consequently mixtures of polyalkylated benzenes may be obtained. On the other hand, nitro compounds are sufficiently deactivated for the reaction to be unsuccessful. 

The anodic oxidation of benzene produces a mixture of polyphenylene compounds. This oligomerization can be performed in acetonitrile [21] or in liquid sulfur dioxide [22]. Mixed coupling between naphthalene and alkyl benzenes has also been demonstrated (Table 1, numbers 12-16). The relative yield of mixed coupling products increases with the basicity of the alkyl benzene with mesitylene 19%, with tetramethylbenzene 42%, and with pentamethylbenzene 64% of mixed coupling products are obtained. This suggests an electrophilic reaction between naphthalene cation radicals and alkylbenzenes. The mixed coupling reaction of phenanthrene with anisole has been studied kinetically. The results indicate that initially a complex PA is formed between the phenanthrene radical cation and anisole, followed by an electron transfer from the complex. The resulting PA" -anisole complex then decomposes to the product [23]. 

Hamilton, J.F., A.C. Lewis, C. Bloss, V. Wagner, A.P. Henderson, B.T. Golding, K. Wirtz, K, M. Martin-Reviejo and M.J. Pilling Measurements of photo-oxidation products from the reaction of a series of alkyl-benzenes with hydroxyl radicals during EXACT using comprehensive gas chromatography. Atmos. Chem. PAys., 3, (2003) 1999-2014. 

Moreover, studies of products formed during the smog-chamber oxidations of multialkyl benzenes invariably indicate the presence of ring decomposition reactions (leading, for example, to the production of per-oxyacetyl nitrate from m-xylene or mesitylene). Chemical reactivity of aromatic hydrocarbons is enhanced by an increasing number of alkyl groups, especially those in meta positions on the benzene ring. 

Condensed monoaromatic naphthenes (i.e., monoaromatics such as decalin) with fused cycloparaffinic rings showed no induction period and reacted rapidly from the start, with inhibition developing in the later stages of the oxidation, as is typical of the autoretardant mechanism. In contrast, alkylated benzenes and... 

Benzene derivatives as such do not absorb much light in the solar UV region however, in the presence of oxygen some of them form complexes (Chien, 1965 Khalil and Kasha, 1978 Onodera et al., 1980 Pasternak and Morduchowitz, 1983) that are susceptible to photolysis. It appears that the absorption spectra of the complexes tail into the solar UV region (Chien, 1965) and that the quantum yield for reaction is rather high. Products of the reactions include long-chain conjugated dialdehydes from benzene itself (Wei et al., 1967) and alcohols and aldehydes from side-chain oxidation of alkyl-substituted benzenes (Pasternak and Morduchowitz,... 

The kinetics of the primary oxidation steps of the OH initiated oxidation of the alkylated benzenes, i) abstraction of an H atom from an alkyl side group, and ii) addition to the ring, as outlined in Fig. 9, are reasonably well established (Becker, Devolder, Kerr, Zetzsch). Branching ratios for abstraction/addition have been obtained for toluene and the xylene isomers, however, data for higher alkylated benzenes are poor. Reversible addition to the aromatic ring is the dominant pathway and accounts for approximately 90 % of the reaction. 

Organic residual components are the most worrying because of their toxicity. Some of these compounds are formed as by-products. Volatile organic compounds are determined by headspace GC, GC-MS. Intermediate products, such as sultones and sulfones, from sulfonation of olefin and alkyl-benzene, respectively, can be detected by LC. Unreacted products, like ethylene oxide from the synthesis of ethoxylated nonionic and anionic surfactants, are studied by GC benzyl chloride from the quaternization of tertiary amines and aliphatic amines from amidation reaction are determined by LC (Figure 5). 

The rates of OZ, DMPC and CHP formation are increase with [NiO]. The ozonides are obtained from the ozone interaction with C=C bonds in the benzene ring, and the ozonolysis of the hydrocarbon part takes place via a hydrogen atom abstraction mechanism. No ozonides formation on the surface and ozonation of the alkyl part dominates in homogeneous and heterogeneous part of the reaction. The ozone is activated on the NiO surface via the formation of the surface compound Ni Oj according to the scheme oxidizes the alkyl part of cumene ... 

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