Octane numbers, of hydrocarbons

Refiners will turn to reformulated motor fuels where the octane number will be increased by alkylate or oxygenated compounds. It has indeed been shown for a long time that oxygenated compounds, alcohols, ethers and ketones Improved the octane number of hydrocarbon-based blends (Whitcomb, 1975). 

The isomerization of light paraffin using superacid solid catalysts is a clean way to increase the octane number of hydrocarbons. On this basis, sulfated metal oxides have attracted the attention of many research groups owing to their high activity in acid catalyzed reactions [1]. Sulfated zirconia was found to be a promising catalyst in this field and at the industrial level [2],... 

To predict the octane numbers of more complex mixtures, non-linear models are necessary the behavior of a component i in these mixtures depends on its hydrocarbon environment. 

Because of its large reactor volume, the auto-refrigerated process can operate at very low alkene space velocities of about 0.1 h-1 LHSV (WHSV ca. 0.03 h 1). This design helps in increasing the octane number of the product and lowering acid consumption. The reaction temperature is maintained at about 278 K to minimize side reactions. Spent acid is withdrawn as 90-92 wt% acid. The isobutane concentration in the hydrocarbon phase is kept between 50 and 70 vol%. 

Reforming the conversion of hydrocarbons with low octane numbers into hydrocarbons having higher octane numbers (e.g., the conversion of an n-paraffin into an isoparaffin). 

Reforming, In refining, a catalytic process in which naphtha molecules are cracked, rearranged, and/or recombined for the purpose of increasing the octane number of the naphtha. Reforming is also the process of converting hydrocarbons and steam to synthesis gas (carbon monoxide and hydrogen). 

Certain rules have been developed for predicting the octane number of different types of gasoline, depending on the ratio of different types of hydrocarbons in the mixtures ... 

The hydrocarbon-type analysis of the Platformate discussed above was based on the product having an octane number of 92.9 (F-l plus 3 ml. of tetraethyllead per gallon). The aromatic content (based on charge) increases continually with increased severity. At the two highest severities, the aromatic yield (based on the charge) is in excess of the total naphthenes and aromatics present in the charge. This indicates the participation of the dehydrocyclization reaction of paraffins to form aromatics. 

Olefin Isomerization. One other type of hydrocarbon isomerization is on the threshold of commercialization—namely, that of olefins. Processes for olefin isomerization were first developed some 15 years ago (11, 14, 20) after it was recognized that highly branched olefins have higher octane numbers than do their straight-chain isomers, and that the octane numbers of olefins increase as the double bond moves toward the middle of the molecule. 

The new Brownsville, Tex., plant for the manufacture of synthetic liquid fuels from natural gas makes use of this reaction to increase the octane number of its product by as much as 20 units. Synthetic naphtha produced over iron catalyst is highly olefinic and contains substantial amounts of straight-chain isomers with terminal double bonds (8). The shifting of these double bonds toward the center of the molecule may be accomplished by vapor-phase treatment employing synthetic cracking catalyst in the fluid state, under mild catalytic cracking conditions. Oxygenated compounds also present are converted under the isomerization conditions to hydrocarbons and water. 

Aromatic hydrocarbons have exceptionally high engine characteristics. The Research octane numbers of all aromatic hydrocarbons thus far measured are above 100. Those measured by the Motor method are a little lower, but in all cases are above 95. The critical compression ratios at 600 revolutions per minute and 212° F., jacket temper-... 

The blending octane number of benzene is the lowest for any aromatic hydrocarbon thus far measured. When measured by either the Research or Motor method it seems to form another case where the first member of an homologous series is anomalous. 

Traditionally, solid acidic catalysts are applied in industry for the oligomerization of butenes and are still studied. MTS-type aluminosilicates,522 a NiCsNaY zeolite,523 and a silica-alumina containing 13% alumina524 proved to be active and selective catalysts. Moreover, deactivation rates of these catalysts are also favorable. Sulfated zirconia promoted with Fe and Mn was active and selective to yield primarily dimethylbutene isomers under supercritical conditions.525 A small amount of water improved productivity and decreased deactivation. A study showed that the blending octane number of Cg hydrocarbons is directly linked to the number of allylic hydrogens in the molecules.526... 

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. 

Yield (wt%) is defined by 100 X [the weight of products divided by the weight of I-butene charged]. 224-TMP = 2,2,4-trimethylpentane, 23-DMH = 2,3-dimethylhexane, etc. Figures in parentheses are research octane number (RON). Hydrocarbons containing 5-7 carbon atoms. JOctenes. Hydrocarbons constaining 9-12 carbon atoms. Catalyst, 1.0 g I-butene, 0.94 g isobutane, 9.4 g. All data were collected at 7 h. 

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