High molecular weight aromatics

High-molecular-weight aromatic poly(benzothiazole)s can be obtained from dichloride (26) of 15 and 29 in PPA under similar reaction conditions (Scheme 17). 

A significant portion of the sulfur- and nitrogen-containing species in crude oil can be found in heterocyclic form within the asphaltene, maltene, and resin compounds. Oxygen-containing heterocycles may also be present. Examples of high-molecular-weight aromatic, resinous, and polar compounds found in crude oil are provided in TABLE 3-1. 

TABLE 3-1. Examples of High-Molecular-Weight Aromatic, Resinous, and Polar Compounds Found in Crude Oil... 

Fuel olefins have been implicated as the primary cause of deposits in gasoline fuel injectors and carburetors. High-boiling-point, high-molecular-weight aromatic components have also been shown to contribute to intake system deposit and gum formation. Once formed, other compounds in the fuel can adhere to these deposits to form an amorphous-type deposit. 

Methyl nitrite (CH3ONO) MNIT High-molecular-weight aromatic oxidation ... 

For hydroconversion of nonhydrocarbon constituents, catalysts with weak acidity are used where cracking is undesirable. Strong hydrogenation activity is needed, particularly with heavy feedstocks containing high molecular weight aromatics. 

High molecular weight aromatic ether polymers have now been successfully prepared by a number of different methods and several other... 

This is perhaps the most ovious approach to the synthesis of a high molecular weight aromatic ether because it is the reaction which has most commonly been used in the laboratory. However, the yields that have been reported for the preparation of simple aromatic ethers by this method do not appear to be high enough to allow the formation of high molecular weight polymers (72, 82). 

The Demex process selectively rejects asphaltenes, metals, and high molecular weight aromatics from vacuum residues. The resulting demetallized oil can then be combined with vacuum gas oil to give a greater availability of acceptable feed to subsequent conversion units. 

The first stage overhead is heated by an exchange with hot solvent. The increase in temperature decreases the solubility of resins and high molecular weight aromatics. These precipitate in the second stage extractor. The bottom stream of this second stage extractor is recycled to the first stage. A portion of this stream can also be drawn as a separate product. 

Desulfurisation. Aliquots of polar and High-Molecular-Weight Aromatic (HMWA Figure 1) fractions were desulfurised using Raney Ni as described elsewhere (18). The mixture after desulfurisation was separated over a small (5 x 0.5 cm) alumina column using hexane/C C (9 1) to elute the saturated and aromatic hydrocarbons and CH2Cl2 to elute more polar... 

The kinetics of polycondensation hy nucleophilic aromatic substitution in highly polar solvents and solvent mixtures to yield linear, high molecular weight aromatic polyethers were measured. The basic reaction studied was between a di-phenoxide salt and a dihaloaromatic compound. The role of steric and inductive effects was elucidated on the basis of the kinetics determined for model compounds. The polymerization rate of the dipotassium salt of various bis-phenols with 4,4 -dichlorodiphenylsulfone in methyl sulfoxide solvent follows second-order kinetics. The rate constant at the monomer stage was found to be greater than the rate constant at the dimer and subsequent polymerization stages. 

Aromatic polyesters were enzymatically synthesized under mild reaction conditions. Divinyl esters of isophthalic acid, terephthalic acid, and p-phen-ylene diacetic acid were polymerized with glycols by lipase CA catalyst to give polyesters containing an aromatic moiety in the main chain.208 In the lipase-catalyzed polymerization of dimethyl isophthalate and 1,6-hexanediol in toluene with nitrogen bubbling, a mixture of linear and cyclic polymers was formed.209 High molecular weight aromatic polyester (Mw 5.5 x 104) was synthesized by the lipase CA-catalyzed polymerization of isophthalic acid and 1,6-hexanediol under vacuum.210 Enzymatic polymerization of divinyl esters and aromatic diols also afforded the aromatic polyesters.211... 

Asphaltenes are derived from the root word "asphalt", a "sticky tar-like substance found naturally in petroleum crude oil." Asphaltenes are complex, high molecular weight aromatic compounds suspended within the fuel. They have high melting points and high carbon/hydrogen ratios with low calorific values. 

Photochemical oxidation acts on oil at or near sea surface to convert high molecular weight aromatic hydrocarbons to polar oxidized compounds. Some of the oxidation products formed by this process include alcohols, ethers, dialkyl peroxides, and aliphatic acids. The photochemical oxidation process, which operates most efficiently on thin oil slicks 10 cm thick), is more important after the volatile oil fractions have evaporated. 

Heterogeneous mixtures of high-molecular-weight aromatic structures that result from secondary synthesis reactions. 

High molecular weight aromatic poly(l,3,4-oxadiazole)s (PODS) were prepared by a one-pot procedure from dicarboxyhc acid and a hydrazine salt (sulfate, phosphate) or dicarboxylic acid dihydrazides in a mixture of ionic liquid and triphenyl phosphate, used both as a solvent and condensing agent. The polycyclization occurred at a sufficiently low temperature of 210 °C to give film-forming PODS [92]. 

---