Of isoparaffins

Calculational coefficients related to a change of state of isoparaffins. 

Alkylate is composed of a mixture of isoparaffins whose octane numbers vary with the olefins from which they were made. Butylenes produce the highest octane numbers, propylene the lowest, and amylenes (pentylenes) the iatermediate values. AH alkylates, however, have high (>87) octane numbers that make them particularly valuable. 

Aromatization of isoparaffins and ii-paraffins is more difficult. Not only is the reaction slower, but also the ultimate yield is lower because more... 

The alkylate contains a mixture of isoparaffins, ranging from pentanes to decanes and higher, regardless of the olefins used. The dominant paraffin in the product is 2,2,4-trimethylpentane, also called isooctane. The reaction involves methide-ion transfer and carbenium-ion chain reaction, which is cataly2ed by strong acid. 

Identification becomes more difficult in the case of isoparaffins since many structural isomers are possible with increasing carbon number. Nevertheless, all possible isoalkanes from through have been found in crude oils, along with several isomers of and some of Many isoprenoids (e.g., pristane and phytane) which serve as biomarkers to the genesis of petroleum have been detected in significant... 

The Heterogeneity of Catalyst Surfaces for Chemisorption Hugh S. Taylor Alkylation of Isoparaffins V. N. Ipatieff and Louis Schmerling Surface Area Measurements. A New Tool for Studying Contact Catalysts P. H. Emmett... 

The alkylation of isoparaffins with olefins is the reaction involved in the large scale processes in the petroleum industry. Any isoparaffin and almost any olefin can be used and although the product in largest percentage is usually with the number of carbon atoms equal to the sum of the carbon atoms in the paraffin and olefin, this is not always the case. A great mixture of branch chain products is obtained (Phillips Petroleum Company, 13). 

Just as in the case of aromatic compounds isoparaffins can be alkylated with sources of alkyl groups other than olefins. Alkyl halides, alcohols, ethers, mercaptans, sulfides, etc., can be used. When olefins are used some alkyl fluorides from a combination of olefin and hydrogen fluoride are always formed. The quantity of this in the product can be greatly reduced by providing conditions under which the alkyl fluoride is used in alkylation. The apparent paradox is provided, in that the fluoride content of the product is lessened by further treatment with hydrogen fluoride. A more thorough treatment of the details of the alkylation of isoparaffins with olefins is found elsewhere in this volume. 

The use of additional substances to increase the activity of a catalyst is a well known phenomenon. Hydrogen chloride or traces of water are known to promote aluminum chloride catalyzed reactions. In the same way the reaction of isoparaffins with olefins has been shown to be catalyzed by boron trifluoride in the presence of nickel powder and with water as the promoter (Ipatieff and Grosse, 76). Hydrogen fluoride can take the place of the water and thus serve as the promoter. 

Figure 7. Comparison of isoparaffin yield obtained in micro fluid-bed and large pilot plant.

The relatively recent development of isoparaffinic fractions from petroleum has resulted in experimental products of a very low order of toxicity to plant tissues. Initial studies have also indicated that selected isoparaffinic fractions are of a high order of toxicity to some insects or their eggs. The future development of isoparaffinic oils may result in new and important contributions to pest control on agricultural crops. 

Table I. Effect of Isoparaffinic Oil on Red Spiders and Certain Insect Eggs...

In the work here reported the relatively low phytotoxic qualities of isoparaffinic fractions were evident from the inception of the screening tests in 1945. In order to evaluate this characteristic more precisely, applications of the fraction previously described were made on the foliage of plants in the greenhouse and in the field, employing the oil at full concentration and at several dilutions in emulsion form. 

It appeared desirable to use a method which was relatively simple, and generally known, in initial efforts to correlate data on the phytotoxicity of isoparaffinic fractions with an acceptable quality control procedure. The determination of acid number (value), a common petroleum laboratory procedure, was employed in the current study. 

The increase in phytotoxicity of isoparaffinic fractions stored in light is believed to be due to the accumulation of acids resulting from oxidation. 

The reaction between isobutane and olefins in the presence of an alkylation catalyst results in a product that is essentially paraffinic, and consists of a mixture of isoparaffins ranging from pentanes to decanes and higher regardless of which alkylating olefin is used. 

In the ethylenediammonium forms of these two preparations there was a sensitive dependence of uptake upon molecular dimensions under the experimental conditions used (72) and distinctions between the crystals of the two exchange capacities. The free distance between pairs of siliceous layers of the sorbate free fluorhectorites was 2.8 A. When guest molecules are taken up, this distance within limits increases enough to accommodate the guest. Thus, among the paraffins isobutane and 2,3-dimethylbutane were taken up. However, paraffins with quaternary carbons (neo-Cs, 2,2-di-CH3-C4, 2,2,4-tri-CH.3-C5) were not. The important dimension is the difference in height of these species (4.65 and 5.9 A). The sorption of n-paraffins (minimum thickness 4.0 A) occurred more rapidly than that of isoparaffins. Isotherms and kinetics of uptake are illustrated for n-octane in Figure 12 (72). 

In the specific example shown in Table III, the difference in ratios of isoparaffins to normal paraffins in the C5-l80°F product from the two catalysts results in a four octane number difference. 

Figure 2 shows that the distribution of isoparaffins (on a fresh feed basis) is also altered with ZSM-5 the C7+ isoparaffin yields are decreased and the Cg- isoparaffin yields are increased when ZSM-5 is added to either Catalyst A or B. The increase in the... 

In certain reactions, such as the isomerization of butane and the alkylation of isoparaffins, problems of handling hydrogen chloride and acidic sludge are encountered. The corrosive action of the aluminum chloride-hydrocarbon complex, particularly at 70 to 100°C, has long been recognized and various reactor liners have been found satisfactory. 

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