Alkylcyclopentanes

The alkylcyclopentane (AGP) to aromatics process (ACP ACH Ar) is less efficient than ACH dehydrogenation, owing to the slowness of the first step and to ACP ring opening. Under conditions where cyclohexane is converted to benzene with close to 100% efficiency, only 50—75% of methylcyclopentane may be converted to benzene. 

The isomerization reaction, which is acid-site controlled, includes the conversion of alkylcyclopentanes into alkylcyclohexanes, which, in turn, are quickly converted to aromatics by dehydrogenation. In addition, isomerization also includes the conversion of feed n-paraffms into higher octane I-paraffins. 

Dehydrocyclization refers to the conversion of feed paraffins into alkylcyclohexane and alkylcyclopentane naphthenes. These, in turn, are subsequently converted by isomerization and dehydrogenation into aromatics. Dehydrocyclization is controlled by both acid and platinum functions and is the most sensitive indicator of catalyst selectivity. 

Isomerization of alkylcyclopentanes may also occur on the platinum catalyst surface or on the silica/alumina. For example, methylcyclopen-tane isomerizes to cyclohexane ... 

With platinum and palladium supported on acidic alumina, cyclopentanes are important intermediates of aromatization (44, 123-124). For example, n-heptane gave about 2-3 times more aromatic product than 2,4-dimethyl-pentane, whereas the formation of C5 cyclic products was about the same from both alkanes. Alkylcyclopentanes aromatized at a reasonable rate (123a). 

Alkylcyclopentanes and cyclohexanes rearrange to aliphatic alkenes during both photolysis and radiolysis [108-113]. The double bond in the product aliphatic alkenes can be found connected to one of the carbon atoms taking part in ring opening. The derivation of... 

From this compound as well as from other alkylcyclohexanes the yield of ring-opening products is relatively small, about = 0.1-0.4, and G = 0.3-1.6 [108,110] (Table 6), while usually the main decomposition process is the hydrogen formation, which leaves the cyclic structure intact. Here, and with the other alkylcyclohexanes and alkylcyclopentanes, the scission of the ring to smaller molecular mass alkenes and cyclopropane derivates was detected with very low yield. 

Smittenberg has described a composite function of the refractive index and density which he calls the refractivity quotient (38). When the refractivity quotient is plotted against the reciprocal of the number of carbon atoms the n-alkylbenzenes, n-alkylcyclo-hexanes, and n-alkylcyclopentanes, all show alternation for the first several members of the senes. 

Isomerization of alkylcyclopentanes or alkylcyclohexanes in which the alkyl group consists of at least two carbon atoms yields methyl-substituted cyclohexanes. For example, at 50°C, sec-butylcyclopentane produced trimethylcyclohexanes but no propylcyclohexane.16 In another study, n-, sec-, or te/t-butylcyclohexanes at 150°C were almost quantitatively converted to tetramethylcyclohexanes.17... 

Skubla [9] has designed a group contribution scheme which applies for various homologous series. His method relies on eq. 6.2.1 where both coefficients a0 and a have to be derived from group contributions and with respect to Nc. The model applies for n-alkanes, 1-alkenes, n-alkylcyclopentanes and n-alkylcyclohexanes, alkylbenzenes, 1-bromoalkanes, 1-alkanols, di-n-alkyl ethers, carboxylic acids and esters, 1-alkanethiols, 1-aminoalkanes, dialkylamines, alkaneamides, and some... 

Most multipromoted catalysts have been described for the catalytic reforming of petroleum. For this process it is typical, that several reactions take place simultaneously dehydrogenation of cyclohexanes, dehydroisomerization of alkylcyclopentanes and dehydrocyclization of alkanes. Isomerization, hydrogenolysis, and hydrocracking are also involved in the process. 

Il in and Usov have shown that over acidic platinum-alumina catalyst there are at least two consecutive pathways from n-nonane to indan (57) either through alkylaromatic intermediates, by first closing the six-membered ring or through alkylcyclopentane intermediates, by first closing a five-membered ring (Table VII and Fig. 6). 

Kazanskii and co-workers have described an interesting special case, double cyclization of -octane at 310°C over platinum-on-charcoal catalyst at 0.2 liquid hourly space velocity. The reaction product contains about 0.25% m-octahydropentalane and 2.2-4.5% alkylcyclopentanes (an approximately l lmixture of trans-l-methyl-2-ethylcyclopentane and n-pro-pylcyclopentane) (39, 40). Indirect evidence suggests that most of the octahydropentalane is formed from l-methyl-2-ethylcyclopentane, which cyclizes significantly faster than w-propylcyclopentane. 

Catalytic reforming. Catalytic reforming is a process for increasing the octane number of naphthas. It involves isomerisation of alkanes, dehydrogenation of cyclohexanes to aromatic hydrocarbons, isomerisation and dehydrogenation of alkylcyclopentanes, and dehydrocyclisation of alkanes. 

Section 1.1.3.1 Formation of 1-vinyl-2-alkylcyclopentanes from 1,6-dienes. Nakai and coworkers found that (207) undergoes an ene reaction on heating in toluene for 20 h at 200 C to give 97% of (208). The stereochemistry of the enophile does not affect the stereochemistry of the product. The isomer with an ( ) double bond in the ene component gives mixtures of stereoisomers. 

Figure 11 Long-chain alkylcyclopentanes are relatively abundant in the C40+ region of the chromatograms of most oils. Oils from marine (a), saline lacustrine (b), and freshwater lacustrine (c) environments can be differentiated on the basis of these alkylcyclopentane distributions. Marine oils have a distinct odd/even predominance pattern oils from saline lacustrine environments demonstrate a high even/odd predominance pattern, and freshwater lacustrine oils are characterized by a low even/odd to no clear predominance pattern.

Weisz and Prater 28) have pointed out that, while on platinum reforming catalysts alkylcyclohexanes will proceed rapidly to aromatics, the conversion of alkylcyclopentanes to aromatics becomes the key dualfunctional reforming reaction in the neighborhood of 98 (R.O.N. with 3 ml. 

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