Higher paraffins

Space does not permit a detailed consideration of the other paraffin hydrocarbons whose pyrolysis mechanisms have been elucidated the following are some references to recent publications  

Isobutane Niclause et Brooks Purnell et Isopentane Bryce and Chrysochoos Niclause et Neopentane Niclause et Anderson and Benson °. 

It is of interest to note that the ethane and neopentane mechanisms each involve only two propagation reactions, namely 

In all cases two types of propagation reactions take place  

In some cases e.g. C2H5) a radical may act both asa p radical and a g radical. 

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Sage, B. H., Lacey, W. N., "Thermodynamic Properties of Higher Paraffin Hydrocarbons and Nitrogen," Am. Petr. Inst., New York, N.Y. (1950). ... 

In a polluted or urban atmosphere, O formation by the CH oxidation mechanism is overshadowed by the oxidation of other VOCs. Seed OH can be produced from reactions 4 and 5, but the photodisassociation of carbonyls and nitrous acid [7782-77-6] HNO2, (formed from the reaction of OH + NO and other reactions) are also important sources of OH ia polluted environments. An imperfect, but useful, measure of the rate of O formation by VOC oxidation is the rate of the initial OH-VOC reaction, shown ia Table 4 relative to the OH-CH rate for some commonly occurring VOCs. Also given are the median VOC concentrations. Shown for comparison are the relative reaction rates for two VOC species that are emitted by vegetation isoprene and a-piuene. In general, internally bonded olefins are the most reactive, followed ia decreasiag order by terminally bonded olefins, multi alkyl aromatics, monoalkyl aromatics, C and higher paraffins, C2—C paraffins, benzene, acetylene, and ethane. 

Typical COED syncmde properties are shown in Table 12. The properties of the oil products depend heavily on the severity of hydroprocessing. The degree of severity also markedly affects costs associated with hydrogen production and compression. Syncmdes derived from Western coals have much higher paraffin and lower aromatic content than those produced from Illinois coal. In general, properties of COED products have been found compatible with expected industrial requirements. 

A zero value has been assumed for n-paraffins, 100 for aromatics. A low BMCI value indicates a higher paraffin concentration in a petroleum fraction. 

Higher paraffinic hydrocarbons than methane are not generally used for producing chemicals by direct reaction with chemical reagents due to their lower reactivities relative to olefins and aromatics. Nevertheless, a few derivatives can be obtained from these hydrocarbons through oxidation, nitration, and chlorination reactions. These are noted in Chapter 6. 

The fit of these equations to the data is very good, as seen in Fig. 18. These equations are valid to very small values of CO concentrations, where the reaction becomes first order with respect to CO. In a mixture of CO with oxygen, there should be a maximum in reaction rate when the CO concentration is at 0.2%, as shown in Fig. 19. When the oxidation of olefins and aromatics over a platinum loaded monolith is over 99% complete, the conversion of higher paraffins may be around 90% and the conversion of the intractable methane is only 10%. 

Air atmospheric t,/2 2.4-24 h for C4H10 and higher paraffins for the reaction with hydroxyl radical, based on the EPA Reactivity Classification of Organics (Darnall et al. 1976) photooxidation reaction rate constant of 1.02 x 10-11 cm3 molecule-1 s-1 with OH radical with an estimated lifetime x = 14 h during summer daylight (Altshuller 1991). 

When a combustible substance is mixed with air, the mixture will explode only when it is neither too rich nor too lean. The lower explosion limit (LEL) is the minimum volume percent of the substance in air with flammability, which is separated from the upper explosion limit (UEL) by the explosive concentration range. The tabulations in handbooks are based on experimental data, and sometimes derived from estimation methods based on the elemental composition of the fuel as CmEtxOy. Figure 6.11 shows the LEL for the series of normal paraffins and of 1-alcohols versus the number of carbon atoms. There are two ways to plot the results, which show that, for paraffins, the volume percent shows a steeply declining trend, but the weight percent shows a mildly increasing trend. One may conclude that a smaller volume percent of higher paraffin... 

Dilute with lower-viscosity kerosene having a higher paraffin/lower aromatic content. 

Over-cracking of PCC gasoline with either ZSM-5 or REHY results, in both cases, in a preferential loss of heavier olefin components. The major differences between the two zeolites is the increased C3/C4 ratio with ZSM-5 which has been assigned to pore size effects, and enhanced bimolecular hydrogen transfer reactions with REHY, resulting in a higher paraffin/olefin ratio. 

Figure 2 shows that there is a limited conversion of higher paraffins on either zeolite. There is seme evidence to suggest that C7/C8 paraffin conversion is higher with ZSM-5 and C9/C10 with REHY. However, it would appear that ZSM-5 is not, under the present conditions, particularly effective in paraffin modification in the presence of a relatively high concentration of olefins. 

Often naphtha is split at about lOO C into a heavy and a light fraction. The light fractions tend to have a higher paraffin content and more attractive to petrochemical operators and the heavy fraetion containing higher levels of naphthenes and aromatics are of interest to refiners for reforming into high octane blend stock. 

After the war, ARGF (Arbeitsgememschaft Ruhrehemie und turgi) developed the high-load fixed-bed process. The precipitated iron catalysts used consisted of Fe (100). SiOj (25), K2O (5). and Cu (5). The typical product composition obtained was 32% gasoline, 21 % diesel fuel, and 47% higher paraffins (wax) [3]. 

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