Condensed polynuclear aromatic

In this instance a second aromatic ring can be substituted for two adjacent hydrogen atoms giving condensed polynuclear aromatics, for... 

Asphaltenes are obtained in the laboratory by precipitation in normal heptane. Refer to the separation flow diagram in Figure 1.2. They comprise an accumulation of condensed polynuclear aromatic layers linked by saturated chains. A folding of the construction shows the aromatic layers to be in piles, whose cohesion is attributed to -it electrons from double bonds of the benzene ring. These are shiny black solids whose molecular weight can vary from 1000 to 100,000. 

The aromatic extracts are black materials, composed essentially of condensed polynuclear aromatics and of heterocyclic nitrogen and/or sulfur compounds. Because of this highly aromatic structure, the extracts have good solvent power. 

SCHOLL Polyaromatle synthesis Preparation of condensed polynuclear aromatics by Friedel-Crafts catalysts... 

Inokuchi, H., Shiba, S., Handa, T., Akamatsu, H. (1952) Heats of sublimation of condensed polynuclear aromatic hydrocarbons. Bull. Chem. Soc. Japan 25, 299-302. 

Similarly in condensed polynuclear aromatic compounds and heterocyclic compounds, the magnitude of the coupling constants between protons in the aromatic rings reflects the relative position of the coupled protons. 

In the foregoing discussion of the structure of benzene the stability and characteristic aromatic properties of the substance have been attributed to resonance of the molecule between the two Kekul6 structures. A similar treatment, which provides a similar explanation of their outstanding properties, can be given the condensed polynuclear aromatic hydrocarbons. 

The chromatogram obtained for the extract of the cumene-deactivated parent H-mordenite is shown in Figure 9. The temperature profile-product distribution of the chromatogram is similar to that obtained by Venuto et al. (8, 4) in their studies on REX catalyst deactivation. They established the presence of condensed polynuclear aromatics in the REX adsorbate. 

Although the great majority of petroleum and coal-based pitch materials, as well as model compounds such as polyvinyl chloride, acenaphthylene, decacyclene and polynuclear aromatic hydrocarbons, form anisotropic graphitizable carbons, it is an almost impossible task to predict the type of optical texture of a coke from an elemental analysis of the pitch. The size, shape and reactivity of peri-condensed polynuclear aromatic molecules in the products of pyrolysis of a pitch play a more important role in determining optical texture. 

Direct fiuorination of carbons and condensed polynuclear aromatic compounds... 

On the other hand, Margrave et al. reported that the condensed polynuclear aromatic compounds such as anthracene, pyrene and coronene, were easily fluorinated even at ambient temperature and that the various perfluoro-derivatives were obtained depending upon the starting materials [9-12]. In their method, fluorine gas was introduced into the reactor at a slow rate such that the initial concentration of the fluorine was a mere trace and the concentration of fluorine was then gradually increased up to 100%. Such fiuorination condition was quite different from that of the graphite in spite of the common feature of the existence of the graphite-like layers and 7r-bond. 

Asphaltene Structure by Spectroscopic Methods. Much of the information available on the carbon skeleton of asphaltenes has been derived from spectroscopic studies of asphaltenes isolated from various petroleums and natural asphalts (I, 2). The data from these studies support the hypothesis that asphaltenes, viewed structurally, are condensed polynuclear aromatic ring systems bearing alkyl sidechains. The number of rings apparently varies from as low as six in smaller systems to fifteen to twenty in more massive systems (13,14). 

A key feature in the current concept of asphaltene structure is believed to be the occurrence of condensed polynuclear aromatic clusters, which may contain as many as twenty individual rings and account for approximately 50% of the asphaltene carbon (i, 2, 13, 14). However, it would be naive to presume that precise (or meaningful average ) molecular structures can be deduced by means of any spectroscopic technique (I, 2, 13, 14) when too many assumptions (incorporating several unknown factors) are required to derive the structural formulae. 

SCHOLL Polyaiomaticsynttwsis Preparation oi condensed polynuclear aromatics by PriedeKrans catalysts... 

SCHOLL Poly aromatic synthesis Preparation oI condensed polynuclear aromatics by FrtedeLCrafts catalysts... 

The major drawback to the application of a PY/GC/MS technique to study polynuclear aromatic systems in petroleum asphaltenes is the amount of material that remains as a nonvolatile residue (Table II). The nonvolatile residue has been postulated (20) to be the result of a highly condensed polynuclear aromatic system being present in the asphaltene (Scheme III). 

JAP2151>. Non-cross-linked condensed polynuclear aromatic resins were prepared using 1,2,4-trioxane and a number of aromatic compounds as monomers at 80-100 °C under acidic catalysis. A mechanism for the polymerization reaction was proposed and the resins obtained were found to be stable up to 400 C. 

THERMODYNAMIC PROPERTIES OF SOME CONDENSED POLYNUCLEAR AROMATIC COMPOUNDS AND SOME BICYCLIC GLOBULAR MOLECULES. PH. D. THESIS. 

In terms of composition, the compoimds positively identified as pitch components consist predominantly of condensed polynuclear aromatic hydrocarbons or heterocyclic compounds containing from three to six rings. Some methyl and hydroxyl substituent groups have also been observed. 

Albaugh and Talarico [24] used several detectors in series to increase the discriminatory power of the method. A Pye Unicam LCM2 flame ionization detector gave total mass distribution, a refractometer indicated the distribution of aromatics and aliphatics UV at > 320 nm sensed the condensed polynuclear aromatics, and a sulphur-specific detector (Dohrmann micro-coulometer) completed the characterization. 

Otani S, Some properties of a condensed polynuclear aromatic resin (COPNA) as a binder for carbon fibre composites, J Mater Sci, 21(6), 2027, 1986. 

They also formed the condensed polynuclear aromatic (COPNA) resin film on a porous a-alumina support tube. Next, a pinhole-free CMSM was produced by carbonization at 400-1,000°C [29], The mesopores of the COPNA-based caibon membranes did not penetrate through the total thickness of each membrane and served as channels which increased permeances by linking the micropores. CMSMs produced using COPNA and BPDA-pp ODA polyimdes showed similar permeation properties even though they had different pore stractures. This suggests that the micropores are responsible for the permselectivities of the carbonized membrane. Besides that, Fuertes [30] used phenohc resin in conjunction with the dip coating technique to prepare adsorption-selective carbon membrane supported on ceramic tubular membranes. 

Kusakabe K, Gohgi S, Morooka S (1998) Carbon molecular sieving membranes derived from condensed polynuclear aromatic (COPNA) resins for gas separation. Ind Eng Chem Res 37 (11) 4262-4266... 

Condensed polynuclear aromatic (COPNA) resins were used as precursor for carbonization by Kusakabe and co-woikers [64], Since COPNA resin is a thermoplastic resin with three-dimensional stmcture, the pore stracture of the carbonized COPNA membrane is expeeted to be different from that of the membrane fabricated by carbonization of PI which is hnear. COPNA corrrporrrrds were synthesized from polycyclic aromatic compormd (PCA) such as pyrene, phenanthrene and 1,4-ben-zenedimethanol (BDM) using p-toluene srriforrie acid as the eatalyst by the procedure given in Fig. 4.18. 

---