Blend, octane number of

The octane number R + M jT) of such reformates is typically in the range of 88.9—94.5, depending on severity of the reforming operation. Toluene itself has a blending octane number of 103—106, which, as shown in Table 19, is exceeded only by oxygenated compounds such as methyl tert-huty ether, ethanol, and methanol. 

The boiling point, refractive index, and density of the olefin derivative of any paraffin were shown, by use of Table III, to stand in the onier of their olefin type. Table X contains the engine data of the olefin derivatives of 2-methylpentane and 3-methylpentane, recorded in the order of their olefin type. No consistent relations between octane numbers or critical compression ratios are obvious—but the blending octane numbers of these branched olefins, as measured by both the research and Motor methods, do generally stand in the order of their type. Two olefins of type III form exceptions, the exceptions being in one case too high and in the other case too low. 

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... 

Fig. 7.7. Non-linear blending of octane number and the definition of blending octane number as used in the API-45 project, illustrated schematically. Mixtures of fuels may show either positive or negative deviations from linearity (solid curves). The blending octane number of a hydrocarbon tabulated in Refs. [10] and [13] is obtained by extrapolation from the ON of the base fuel through the measured octane number of a mixture containing 20% of the hydrocarbon to the righthand axis, as shown.

Fig. 4-46. Approximation for obtaining the blending octane numbers of high-octane components.

TAME has chemical and physical properties that are similar to those of MTBE and ETBE. As expected from its molecular structure, the properties of TAME are closer to gasoline than those of MTBE and ETBE. TAME is miscible with gasoline in all proportions, TAME-gasoline blends are water tolerant (the addition of water does not induce phase separation as with ethanol-gasoline blends Mueller et al., 2009) and can be distributed via pipelines in blends with gasoline, has a high octane number (blending octane number of 112, see table I-E-1), and solubility in water of 11 g liter" ... 

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). 

As can be seen from Figure 4, LBVs for these components are not constant across the ranges of composition. An iateraction model has been proposed (60) which assumes that the lack of linearity results from the iateraction of pairs of components. An approach which focuses on the difference between the weighted linear average of the components and the actual octane number of the blend (bonus or debit) has also been developed (61). The iadependent variables ia this type of model are statistical functions (averages, variances, etc) of blend properties such as octane, olefins, aromatics, and sulfur. The general statistical problem has been analyzed (62) and the two approaches have been shown to be theoretically similar though computationally different. 

Most of the octane blending values reported ia the Hterature use a slight variation on this theoretically sound approach. The composition and octane of the base fuel are assumed to be fixed and the second component is assumed to be added. Using the same nomenclature, the blending octane number (BON) of component 2 is defined as... 

The advantage of this definition is that it does not depend on measuting the tangent of the response curve, although the variation ia the value of the blending octane number is greater. Typically, BONs are measured at an 80/20 mixture. This technique is also usehil when trying to measure the octane of a compound such as butane or methanol that is difficult or impossible to measure ia its pure state. 

Octane. An octane number is a quantitative measure of a fuel mixture s resistance to knocking. The octane number of a particular sample is measured against a standard blend of n-heptane, which has zero octane, and iso-octane, which has 100 octane. The percent of isooctane that produces the same knock intensity as the sample is reported as the octane number. 

Suppose three intermediates (light naphtha, heavy naphtha, and catalytic oil) made in a refinery are to be blended to produce an aviation fuel. The octane number of the fuel must be at least 95. The octane numbers for the three intermediates are shown in the table. 

In this equation, all molecules are divided into four groups paraffins (P), olefins (O), naphthenics (N), and aromatics (A). The v values represent the volume fractions of each component used, while the fa values are the blending values, which were calculated for each of the molecular lumps shown in Table 2. Pure component octane numbers used are designated as ON/, but one should note that in the development of the model, 57 molecular lumps were made based on GC analysis, and pure component ONs were assigned to each lump, and not necessarily each pure component. The kt values are calculated interaction parameters between paraffins, olefins, and naphthenics, and are also shown in Table 2. Based on this equation, and knowing the composition and pure octane numbers of a fuel mixture, an estimation of the blending ON may then be made. 

The data in Table IV and Figure 1 indicate that most of the paraffin concentration reduction took place in the Ce to Ce range and involved monomethyl paraffins. The blending octane numbers for 2-methyl and 3-methyl hexanes are reported as 40 to 56 by ASTM ( ) and are lower than the blending numbers for light (Cs to C ) olefins and Ce to Cii aromatics. Thus, reduction in concentration of these branched paraffins is expected to improve the research octane number of the gasoline. 

An arbitrary mixture of hydrocarbons is compared to a mixture of these two compounds, with its octane number that equal to the appropriate mixture of these standard compounds. Some molecules and their octane ratings are indicated in Table 2-6. Aromatics have a high octane number (toluene is 120), and some compounds such as tetraethyl lead have a strong octane enhancement when added to other mixtures (blending octane number). Oxygenates such as ethanol and ethers (MTBE) have fairly high octane numbers and supposedly produce less pollution, either alone or blended with hydrocarbons. 

The process data are summarized in Table XI. The operation was conducted at a pressure of 250 pounds per square inch and a temperature of 934° F. The depentanized liquid product was fractionated into three cuts called preaviation, aviation, and postaviation blending agents. The yields of these three products were 22.8, 33.5, and 12.6 volume %, respectively. The aviation blending agent had an F-3 blending octane number (1-C) of 100 and an F-4 blending index number (3-C) of 216. The clear research oc-... 

Similarly, the measured octane numbers of the debutanized blend of thermal reformate with polymer are plotted in Figures 1 and 2 at the observed yield of 76.2 volume % for the debutanized blend. 

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