Cyclic paraffins

Cyclohexane is a colorless liquid, insoluble in water but soluble in hydrocarbon solvents, alcohol, and acetone. As a cyclic paraffin, it can be easily dehydrogenated to benzene. The dehydrogenation of cyclohexane... 

Today n-paraffms are exclusively produced from the corresponding distillation cuts of paraffin-rich oils with the use of molecular sieves. Molecular sieves are synthetically manufactured aluminum silicates of the zeolite type, which after dehydration have hollow spaces of specific diameters with openings of specific diameters. The molecules are then able to penetrate the openings in the correct size and form and are held in the hollow spaces by electrostatic or van der Waals forces. The diameter of the zeolite type used for the production of paraffins is 5 A and is refined so that the n-paraffins (C5-C24) can penetrate the hollow spaces while the iso- and cyclic paraffins are unable to pass through [15]. 

In this particular case, the adsorption process can be used to overcome the distillation limitation. This is demonstrated in Figure 6.2, which represents the relative adsorption of C5 and C(, Hnear, branched and cycHc paraffins from the liquid phase of the 5A adsorbent used in the HOP GasoHne Molex process, licensed by HOP. In this process, only Hnear paraffins can enter the pores of 5A zeolite, while branched and cyclic paraffins are completely excluded due to their large kinetic diameters. Also, the selectivity for Hnear paraffins with respect to other types of paraffins is infinite. Consequently, the separation of Hnear paraffins from branched and cyclic paraffins becomes possible. 

Selectivity is a relative term and is defined in the Molex process as the adsorbent s preference for desired component (in this case, normal paraffins) over the undesired feed components (cyclic paraffins, iso-paraffins, aromatics) while employing a particular desorbent. One can easily determine an adsorbent and desorbent combination selectivity using a pulse test screening apparatus. This apparatus consists of a known volume of adsorbent placed in a fixed bed. A stream of desorbent is then passed over the bed to fill the pore and interstitial volume of the bed. A known quantity of feed is introduced to the feed at the top of the adsorbent bed and passed across the column as a pulse of feed. This pulse of feed is then pushed through the adsorbent bed using a known desorbent flow rate. Effluent from the column is monitored for the various feed components and the concentrations of each component noted (with respect to time) as they elude from the... 

When we have obtained a good correlation for normal paraffins, we would naturally want to know if we can extend this to the branched paraffins, and onward to the population of all the saturated hydrocarbons (by including the cyclic paraffins), and onward to the population of all hydrocarbons (by including olefins, acetylenes, and aromatic compounds), and then onward to the population of all organic compounds (by including compounds with heteroatoms, such as O, N, Cl). A correlation that applies accurately to a larger domain is more useful than one that works only for a smaller domain. 

Linear, branched, and cyclic paraffins all exist in refined fuel. Fuel performance problems can often be directly related to the type and concentration of paraffin present. TABLE 5-3 provides information on the typical carbon number range and boiling-point temperatures of paraffins found in several representative fuels and other petroleum products. 

Linear, branched and cyclic paraffins can all be present in fuel. At low temperatures, fuel filtration, pumpability and injection problems are primarily due to paraffinic wax. Refiners can contend with fuel wax through processing changes and blending. Examples include ... 

Linear, branched, and cyclic paraffins all exist in refined fuel. Fuel performance problems can often be directly related to the type and concentration of paraffin present. 

The lower members of the homologous series of 1. Alcohols 2. Aldehydes 3. Ketones 4. Acids 5. Esters 6. Phenols 7. Anhydrides 8. Amines 9. Nitriles 10. Polyhydroxy phenols 1. Polybasic acids and hydro-oxy acids. 2. Glycols, poly-hydric alcohols, polyhydroxy aldehydes and ketones (sugars) 3. Some amides, ammo acids, di-and polyamino compounds, amino alcohols 4. Sulphonic acids 5. Sulphinic acids 6. Salts 1. Acids 2. Phenols 3. Imides 4. Some primary and secondary nitro compounds oximes 5. Mercaptans and thiophenols 6. Sulphonic acids, sulphinic acids, sulphuric acids, and sul-phonamides 7. Some diketones and (3-keto esters 1. Primary amines 2. Secondary aliphatic and aryl-alkyl amines 3. Aliphatic and some aryl-alkyl tertiary amines 4. Hydrazines 1. Unsaturated hydrocarbons 2. Some poly-alkylated aromatic hydrocarbons 3. Alcohols 4. Aldehydes 5. Ketones 6. Esters 7. Anhydrides 8. Ethers and acetals 9. Lactones 10. Acyl halides 1. Saturated aliphatic hydrocarbons Cyclic paraffin hydrocarbons 3. Aromatic hydrocarbons 4. Halogen derivatives of 1, 2 and 3 5. Diaryl ethers 1. Nitro compounds (tertiary) 2. Amides and derivatives of aldehydes and ketones 3. Nitriles 4. Negatively substituted amines 5. Nitroso, azo, hy-drazo, and other intermediate reduction products of nitro com-pounds 6. Sulphones, sul-phonamides of secondary amines, sulphides, sulphates and other Sulphur compounds... 

Ointments are similar to creams but may be more viscous. Many ointments are prepared from a base of anhydrous lanolin or white petrolatum, which is a mixture ofn-, iso-, and cyclic-paraffins. Waxes may be added to make the ointments harder. 

Feed Activity Yield Gas Yield Cyclic Paraffinic... 

Secondly, this mechanism (1,3-carbon-carbon bond activation) apphes to both acychc and cyclic paraffins such as hexane and cyclohexane (Scheme 40 and Table 8). Kinetic studies on the hydrogenolysis of these alkanes are note-... 

It was initially thought that chain folding in polymers like polyethylene would take place in some sort of regular, ordered fashion, as observed in certain cyclic paraffins (Figure 8-55), with some specific sequence... 

Relatively little work has been done on the pyrolyses of cyclopentane and the higher cyclic paraffins, and the nature of the reactions has not been established. Cyclopentane decomposes by two processes, giving (a) cyclopentadiene and hydrogen probably by way of cyclopentene and (b) propene and ethylene (ring cleavage), viz. 

CSj = value from Table 2-344 for C—H groupj bonded to at least one functional gronp or atom Cft = value from Table 2-345 for functional group k Nr = number of nonaromatic rings Ncr= number of—CH2— groups in nonaromatic ring(s) required to form cyclic paraffin of same ring size(s)... 

Carbon numbers quoted are for normal (i.e., straight chain) paraffins. For branched paraffins the carbon numbers will tend to be somewhat higher, and for cyclic paraffins (naphthenes) and aromatics somewhat lower. 

Third, n-allyl complexes are formed by palladium and cobalt analogous complexes of nickel and platinum are less stable, while ruthenium, rhodium, and iridium are not yet known to form them. In catalytic reactions the deuteration of cyclic paraffins over palladium has provided definite evidence for the existence of rr-bonded multiply unsaturated intermediates, while 7r-allylic species probably participate in the hydrogenation of 1,3-butadiene over palladium and cobalt, and of 1,2-cyclo-decadiene and 1,2-cyclononadiene over palladium. Here negative evidence is valuable platinum, for example does not form 7T-allylic complexes readily and the hydrogenation of 1,3-butadiene using platinum does not require the postulate that 7r-allylic intermediates are involved. Since both fields here are fairly well studied it is unlikely that this use of negative evidence will lead to contradiction in the light of future work. 

Table 7.2. NMR chemical shifts and crystallographic forms of cyclic paraffins and polyethylene single crystal in the solid state [18]...

Fig. 9.2. CPMAS NMR spectra of cyclic paraffins, n-paraffin and polyethylene in the solid state [11] (a) C-C24H48 (b) c-CagHss (c) C-C32H64 (d) C-C36H72 (e) C-C40H80 (f) C-C48H96 (g) C-C64H128 (h) c-CgoHieo (i) n-C32H66 and (j) polyethylene. I, II and III correspond to peaks I, II and III in the text, respectively.

Table 9.1. C chemical shifts of cyclic paraffins, n-paraffins and polyethylenes in the solid state.

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