The case of propane

Polar organic solvents readily precipitate exopolysaccharides from solution. The solvents commonly used are acetone, methanol, ethanol and propan-2-ol. Cation concentration of the fermentation liquor influences the amount of solvent required for efficient product recovery. In the case of propan-2-ol, increasing the cation concentration can lead to a four-fold reduction in die volume of solvent required to precipitate xanthan gum. Salts such as calcium nitrate and potassium chloride are added to fermentation broths for this purpose. 

The reaction selectivity is better under these conditions at steady state, because an equihbrated ratio is observed between the resulting higher and lower homolog alkanes. In addition, dynamic conditions allow us to vary the contact time to obtain information about primary products and then about the mechanism. It appears that, in the case of propane metathesis in a stationary regime, conversion increases Hnearly with contact time, which shows that the reaction is under dynamic control with no diffusion Hmitation. Under these conditions, decreasing contact time results in an increase of the selectivity for hydrogen and olefin whereas that of alkanes decreases. Similarly, the alkanes/olefins ratio tends to zero as the contact... 

Ayabe et al. [53] studied the catalytic ATR of methane and propane over AI2O3-supported metal catalysts. In the case of methane they found the following scale of activity Rh> Pd> Ni> Pt> Co, and limited carbon deposition, whereas in the case of propane a large amount of carbon deposition was observed even under steam-rich conditions. 

The most striking aspect of these results is the low Arrhenius A factors corresponding to p factors of the order of 10-3. Callear and Wilson attribute this to a lack of equilibrium involving the transition state caused by relaxation to the lower surface. It is clearly possible in principle to extend this type of measurement to other hydrocarbons. Its extension to the reactions of Br A Py2), although thermochemically favorable (Table X), would be very difficult experimentally on account of more rapid relaxation of Br(42/>i/2) (Table IX) yielding low stationary concentrations of the excited atoms, and possibly even lower yields of the products than with l(52Py, which, in the case of propane,65-88 involved measurement of the order of 10-9 moles in a given experiment.65... 

Reactions of the recoil C1] with several olefins have been studied, including ethylene, propylene, cyclopentene, and cfs-butene-2, as well as with several paraffins. The type of products observed indicated the existence of several general modes of interaction, such as CH bond insertion, interactions with CC double bonds, formation of methylene-C11. The most important single product in all systems is acetylene, presumably formed by CH insertion and subsequent decomposition of the intermediate. Direct interaction with double bonds is shown by the fact that, for example, in the case of propylene, yields of stable carbon atom addition products were significantly higher than in the case of propane. The same was true for ethylene and ethane. 

Propanal reacts with ammonia in acetonitrile to give a hexahydrotriazine (17 R = Et) chloroethanal (17 R = CH2CI) reacts similarly, but in lower yield.24 The reactions proceed via carbinolamines, but increasing chloro substitution (17 R = CHCI2/CCI3) stabilizes the intermediate and disfavours trimerization. hi the case of propanal, forward and reverse rate and equilibrium data are reported, with dehydration of the carbinolamine rate determining. The course of the reactions with some primary amines is also reported. 

This eclipsed conformation has two CH3 with H interactions and one H with H interaction. If a CH3 with H interaction here costs the same amount of energy as it did in the case of propane (1.3 kcal/mol), then this conformation would be expected to be destabilized by 2(1.3) + I = 3.6 kcal/mol (15 kj/mol). This value is in reasonable agreement with the experimental value of 3.7 kcal/mol (15.5 k /mol). 

Aromatization of short alkanes can be carried out on a purely acidic HZSM-5 zeolite. In this case, activation of the alkane is thought to occur by protonation on the zeolite acid sites, with formation of a penta-coordinated carbonium ion (1). In the case of propane, protonation at a C-H bond will lead to the formation of H2 and a sec-propyl cation (dehydrogenation), while protonation at a C-C bond will produce methane and a primary ethyl cation (cracking) ... 

In the thermodynamically controlled isopropylidenation of propane-1,2,3-triols, it is the 5-membered 1,3-dioxolane ring that is preferred (see section 3.2.1). However in the case of propane-2-acylamino-l 3-diols, the thermodynamically favoured product is the 1,3-dioxane ring [Scheme 8,162].356... 

In the case of propane, the two chief products are ethylene and propylene. In practice, operations arc conducted to 70 to 90 per cent conversion depending on the desired nhyiene to propylene ratio. At 90 per cent once-through conversion, a hnal ethylene yield of about 45 molar per cent is obtained after ethane recycling, and the propylene ieid varies from 26 per cent for 75 per cent once-through conversion to 16 molar per cent for 90 per cent conversion. 

Although steam cracking was initially designed for ethylene manufacture, it is only economically justified if tbe different hydrocarbons which it produces are properiy upgraded as petrochemical intennediates. Hence although ethane only produces ethylene as an upgradable product, in the case of propane an attempt is made to profit from the sale of ethylene and propylene, and, in the case of the liquid petroleum fractions (naphtha... 

From now on, butane can be dehydrogenated by a new technique caQed the Star process, already mentioned in the case of propane dehydrogenation (see Section 23.4.2) and also in that of isobutene manufoctnre (see Secticm 63). 

Since the rate of isomerization of alkylperoxy radicals depends upon their molecular weight and structure, it can be seen that the temperature at which the transition occurs will be dependent upon the molecular weight and structure of the hydrocarbon. Thus, for example, in the case of propane 1 5 hydrogen transfer is impossible for the prop-2-ylperoxy radical and 1 4 hydrogen transfer involves the cleavage of a primary C—H bond. The expression therefore reduces to... 

By using palladium on carbon, from previous studies on C3-diol oxidation, poor selectivity can be expected in the case of propane-1,2-diol [12] and good selectivity in the case of propane-1,3-diol (86% of 3-hydroxy-propanoate) [6a],... 

The parameter K can also, like values in enzyme kinetics, be an agglomeration of rate constants that refers to a steady state, rather than an equilibrium situation. Rapid reaction kinetics, in the case of propane-1,2-diol, established that the intermediate was kinetically competent.The reaction with pinacol, where K is very large and the reaction is cleanly second order over a wide range of pinacol concentration,exhibited general acid and general... 

Another important difference between oxidation of Ci-C2 and C3+ hydrocarbons is the appearance in the latter case of degeneration of the primary alkyl radicals. Already in the case of propane, the existence of two isomeric forms of propyl species (not always taken into account) can lead to substantial kinetic consequences because of the distinct difference in their thermochemistry and reactivity. Even certain reaction channels may vary depending on the isomeric form of propyl radicals. This factor may cause a substantial uncertainty especially in the case of modeling of catalytic oxidation due to a poor knowledge about thermochemistry and reactivity of surface active sites and chemisorbed species. 

The oxidation of butane and propane under the influence of radiation from radon did not go to completion as indicated by the appearance of liquid products other than water.7 Prolonged exposure to the alpha radiation, however, gave complete oxidation in the case of propane. 

In the thermal decomposition of such saturated hydrocarbons as propane and butane or higher homologs for the formation of olefins, the cracking may occur over two routes, exemplified in the case of propane by dehydrogenation and demethanation as follows ... 

At the temperatures ordinarily used these two reactions occur with about equal velocities in the case of propane. Both of the olefins which are formed tend to polymerize and undergo further decomposition at this temperature (700° to 800° C.), the propylene at a much higher rate than the ethylene, with the result that either low yields are obtained or low conversions per pass through the cracking reactor must be accepted. A process which would enable a paraffin hydrocarbon to be converted to an olefin of the same number of carbon atoms by a dehydrogenation reaction would be highly desirable in some cases. 

Dickinson and Meyers, 1952). It too uses propane as a selective solvent and its purpose is to concentrate the polyunsaturated triglycerides (the so-called drying oils) in vegetable oils and to extract the vitamin-A values from fish oils. The Solexol process is described in two publications (Dickinson and Meyers, 1952 Passino, 1949). Compare some descriptive phrases from an early paper with contemporary SCF developments for the case of propane-lube oil refining. 

In one of the first such examples, the lithium enolate of (S)-3-methyl-2-pentanone was allowed to react with several aldehydes in the case of propanal, the two products are formed in 15% diastereomeric excess, favoring (179 equation 115). The di- -butylboron enolate of this ketone has been studied and found to give (179) and (180) in a ratio of 63 37 in CH2CI2 and 64 36 in pentane. ... 

To check this assumption, propene was fed together with Nj. As can be seem in Figure 2, C4, Cj and Cg alkanes and alkenes are obtained in the products (the ratio of iso- to normal-hydrocarbon is higher than that expected from thermodynamic equilibrium). Meanwhile, the ratio of toluene plus xylene, to benzene has considerably increased with respect to the case of propane, as was predicted above. This ratio is even higher when... 

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