Rich octane number

The preceding information indicates the paths to follow in order to obtain stocks of high octane number by refining. The orientation must be towards streams rich in aromatics (reformate) and in isoparaffins (isomerization, alkylation). The olefins present essentially in cracked gasolines can be used only with moderation, considering their low MONs, even if their RONs are attractive. 

After bauxite treatment the product was fractionated to produce C3-C4 and naphtha (C5-204°C) fractions. The C3-C4 olefin-rich gas was oligomerized over a solid phosphoric acid (SPA) catalyst to produce an unhydrogenated polymer gasoline with a research octane number (RON) of 95 and MON of 82.21 The bauxite-treated FT motor gasoline (RON of 87, MON of 76) was mixed with the polymer gasoline and some natural gas condensates (and crude-oil-derived naphtha) to produce the final motor gasoline product. In this respect it is noteworthy that the Fe-HTFT-derived material was the high-octane-blend stock. 

Knock value, min. Rich rating Minimum Octane Number 87 — —... 

To determine the octane number, a standard CFR engine is run with the test fuel under specified conditions [9] and the compression ratio is increased until the engine knocks, as indicated by a meter based on an accelerometer attached to the cylinder block. The air/fuel ratio is adjusted for the conditions of maximum knock, which occurs slightly rich of stoichiometric. The test is repeated with a series of reference fuels to find a pair whose critical compression ratios are just above and below that of the test fuel, and the composition of the reference fuel which would exactly match is found by interpolation. 

The octane number of a non branched parafiBn is low when compared with a branched one [2]. Hence, for raw gasoline cuts rich in linear paraffin, that number can be increased developing catalytic processes that are able to crack hydrocarbons with large carbon chains, and to transform C5 and C6 ones to branched isomers. 

The higher grades of fuel are thus classified by their specified antiknock ratings under both sets of test conditions. For example, 100/130 grade fuel has an antiknock quality of 100 minimum by the weak mixture test procedure and 130 minimum by the rich mixture procedure. Octane numbers are used to specify ratings of 100 and below, whereas performance numbers are used above 100. 

Even when it does not contain any RE ions, the Y zeolite is always responsible for a drop in octane number compared to the old amorphous silica-alumina-based catalysts. In order to gain a few points in the octane number, many refiners add to the principal catalyst a small percentage of a ZSM-5-based additive that has pores 0.55 nm in diameter that can only be penetrated by linear aliphatic structures and, to a lesser degree, by monobranched aliphatic structures (Tables 1 and 2). These hydrocarbons, which are those with the lowest octane number, are mainly cracked to olefin-rich LPG, obviously at the expense of a few percentage points in gasoline yield. 

It can also be noted that the slope of the S , .,f-Ka plot reflects the combined effect of stretch rate and non-equidiffusion on the flame speed. Figure 4.1.6 clearly shows that the flame response with stretch rate variation differs for lean and rich mixtures. In particular, as Ka increases, the S for stoichiometric and rich mixtures increases, but decreases for the mixture of equivalence ratio = 0.7. This is because the effective Lewis numbers of lean w-heptane/ air and lean /so-octane/air flames are... 

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