Aromatic olefin oligomers

Hydrocarbons. Synthesized hydrocarbons are the most popular of the synthetic base stocks. These are pure hydrocarbons (qv) and are manufactured from raw materials derived from cmde oil. Three types are used olefin oligomers, alkylated aromatics, and polybutenes. Other types, such as cycloahphatics, are also used in small volumes in specialized apphcations. 

A highly obscure feature of cationic polymerization is the great phenomenological difference between aliphatic and aromatic monomers. The survey by Brown and Mathieson [84] of the behaviour of a very wide range of monomers towards trichloroacetic acid is particularly illuminating in this respect. Unfortunately, there are so few studies with aliphatic olefins that detailed comparisons must be confined to isobutene. It is well known that isobutene cannot be polymerised by conventional acids, such as sulphuric, perchloric, hydrochloric, or by salt-like catalysts such as benzoyl perchlorate, whereas all these catalysts readily give at least oligomers from aromatic olefins. Even when the same catalytic system, (e.g., titanium... 

Frequently substantially more than catalytic amounts of a Lewis acid metal halide are required to effect Friedel-Crafts alkylation. This is due partly to complex formation between the metal halide and the reagents or products, especially if they contain oxygen or other donor atoms. Another reason is the formation of red oils. Red oils consist of protonated (alkylated) aromatics (i.e., arenium ions) containing metal halides in the counterions or complexed with olefin oligomers. This considerable drawback, however, can be eliminated when using solid acids such as clays,97 98 zeolites (H-ZSM-5),99,100 acidic cation-exchange resins, and perfluoro-alkanesulfonic acid resins (Nafion-H).101-104... 

In contrast to the polymers and copolymers of butadiene, the oligomers of aromatic olefins, like styrene, are not compatible with PVC. Oligomers of alkylated polystyrenes are a little better, especially in combination with other liquid plasticizers. Copolymers of styrene and isobutylene are not suitable for use with PVC. 

Catalysts used in the polymerization of C-5 diolefins and olefins, and monovinyl aromatic monomers, foUow closely with the systems used in the synthesis of aHphatic resins. Typical catalyst systems are AlCl, AIBr., AlCl —HCl—o-xylene complexes and sludges obtained from the Friedel-Crafts alkylation of benzene. Boron trifluoride and its complexes, as weU as TiCl and SnCl, have been found to result in lower yields and higher oligomer content in C-5 and aromatic modified C-5 polymerizations. 

Highly crystalline isotactic polyolefins are not soluble in organic solvents at room temperature. However, most amorphous polyolefins and oligomers of cr-olefins are easily soluble in saturated and aromatic hydrocarbons at ambient temperature. This difference in solubility can be used to separate amorphous atactic components of polyolefins from crystalline isotactic material in crude polyolefins mixtures. 

Promising applications of SFC include group separations (paraffins, olefins and aromatics) in petrochemical samples, monitoring of supercritical extraction processes (caffeine from coffee, nicotine from tabacco) and oligomer separations. However, it is in the field of applications that SFC has yet to prove its value. Unique separations that can be accomplished with SFC, but not with either GC or LC, have yet to be demonstrated. 

Similar oligomers from propylene, particularly the trimer and tetra-mer, are widely used to prepare alkylated aromatics for detergent manufacture, but little use has been made of these olefins in antioxidant synthesis. The structures shown below are idealized. 

Information on the initiation reaction is restricted to the solvent tetrahydrofuran, in conjunction with the monomers a-methylstyrene and 1,1,-diphenylethylene which can only form oligomers, at least at room temperature. Initiation may once again be produced by metal alkyls or aryls, by direct contact of the olefin with an alkali metal film, or by use of the addition products of alkali metals to condensed aromatic ring compounds. 

For alkylation of aromatic compounds with olefins, alcohols and alkyl halogenids, acidic zeolite catalysts may also be applied as it shown decads ago [1]. Alkylation of benzene with propene over acid catalysts yields isopropylbenzene (cumene) accompanied by formation of n-propylbenzene, di-isopropylbenzenes and propene oligomers as main by-products. 

Families 1, 2, 3 and 4 result from reactions involving alkylaromatic and olefinic compounds. So, the alkylation of alkylaromatics by olefins (propene or propene oligomers) followed by cycUzation and then aromatization through hydrogen transfer reactions may explain the formation of those femilies [9,10],... 

At the same time, the selectivity of olefin formation decreases. This fact shows that n-hexane is converted into aromatic hydrocarbons through the intermediate olefin form on the ZnO/H-ZSM-5. The processes of dehydrogenation of n-hexane into hexene and conversion of oligomers into aromatic hydrocarbons occur in the aromatization of n-hexane over ZnO/H-ZSM-5. The zinc oxide is involved in the n-hexane activation as well as H-ZSM-5. 

As early as the 1940s Emeleus and Haszeldine [17] discovered that perfluoroalkyl iodides are not only cleaved into perfluoroalkyl radicals by light but also that they add readily to a variety of olefins to yield telomers and 1 1 adducts [18]. This kind of radical chain reaction can also be initiated by high temperatures (Scheme 2.100). The addition of perfluoroalkyl iodides to olefins is a very important method for synthesis of partially fluorinated alkanes, polymers, oligomers, and their derivatives [19]. The synthesis of some perfluoroalkyl aromatic compounds can also be achieved [20]. 

It may also be noted that hydrogen transfer reactions of olefins to aromatics lead to the formation of three moles of paraffins for every mole of aromatics formed (Kaa) over HZSM-5,. The alternative dehydrogenation pathway (Km2) provided by zinc for the conversion of C6-Cg oligomers to aromatics suppresses the hydrogen transfer reactions hence more olefinic molecules are available for the aromatization reaction. Thus, the pathways Kmi and Km2 provided by zinc results in the significant increase in aromatics yield... 

HZSM5 zeolites catalyze the transformation of propane aromatic products. This aromatization requires various steps of propene, oligomerization of propene, cyclization of oligomers and hydrogen transfer from naphtenes to olefinic compounds with formation of aromatics. The cracking of Cg-Cg oligomers leads to C2-C5 olefins which, like propene, participate in the formation of aromatics. 

From isopentane, only isopentane molecides are found in the organic material trapped at low temperatures (50-150°C) in the 5A zeolite pores (Table 2). At higher temperatures, isopentane is still the main compound retained in the 5A zeolite, accompanied by a small amoimt of cracked products (olefins and paraffins), oligomers at 250°C, and aromatics at 420°C. 

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