Normal-Octane

The principal class of reactions in the FCC process converts high boiling, low octane normal paraffins to lower boiling, higher octane olefins, naphthenes (cycloparaffins), and aromatics. FCC naphtha is almost always fractionated into two or three streams. Typical properties are shown in Table 5. Properties of specific streams depend on the catalyst, design and operating conditions of the unit, and the cmde properties. 

P2.10 Data methane-octane normal alkane combustion enthalpies... 

CAS/DOT IDENTIFICATION 111-65-9/UN1262 SYNONYMS n-octane, normal octane. 

Write equations using graphic formulas by which normal butyl alcohol can be converted into (a) normal octane, ( ) normal butylene, (c) secondary butyl alcohol, (d) normal amyl alcohol, (e) normal butane, (/) butylene bromide, (g) secondary butyl bromide, (h) methylethyl ketone, (i) methyl-diethyl carbinol. 

Synonyms/Trade Names n-Octane, normal-Octane ... 

Melaven, R.M., Mack, Jr., E., The collision areas and shapes of carbon chain molecules in the gaseous state normal-heptane, normal-octane, normal-nonane. J. Am. Chem. Soc. 1932, 54, 888. 

Alkylate octane normal Dirty acid on start-up Cold acid... 

By about 1970 the benefits of ZSM-5 zeolite in cracking low-octane normal paraffins in FCC units were well known. By adding 1% of ZSM-5 as a promoter to reforming catalysts it was possible to increase the octane number of reformate at the ejqtense of some liquid yield. 

As a complementary process to reforming, isomerization converts normal paraffins to iso-paraffins, either to prepare streams for other conversions nCi —> /C4 destined for alkylation or to increase the motor and research octane numbers of iight components in the gasoiine pooi, i.e., the C5 or Cs-Ce fractions from primary distillation of the crude, or light gasoline from conversion processes, having low octane numbers. 

Zeohte 5A is used because its pores can size-selectively adsorb straight-chain molecules while excluding branched and cycHc species. The normal hydrocarbon fraction has better than 95% purity, and the higher octane isomer fraction contains less than 2% normal hydrocarbons (64). 

Isomerization. Isomerization is a catalytic process which converts normal paraffins to isoparaffins. The feed is usually light virgin naphtha and the catalyst platinum on an alumina or zeoflte base. Octanes may be increased by over 30 numbers when normal pentane and normal hexane are isomerized. Another beneficial reaction that occurs is that any benzene in the feed is converted to cyclohexane. Although isomerization produces high quahty blendstocks, it is also used to produce feeds for alkylation and etherification processes. Normal butane, which is generally in excess in the refinery slate because of RVP concerns, can be isomerized and then converted to alkylate or to methyl tert-huty ether (MTBE) with a small increase in octane and a large decrease in RVP. 

The normal paraffins produced are raw materials for the manufacture of biodegradable detergents, plasticizers, alcohols, and synthetic proteins. Removal of the / -paraffins upgrades gasoline by improving the octane rating. 

Paraffin Isomerization. Another weU-estabhshed commercial process which employs zeoflte catalysts is the isomerization of normal paraffins into higher octane, branched isomers. The catalyst for the Hysomet process of the Shell Oil Co. is dual-functional, and consists of a highly acidic, latge-pote zeoflte loaded with a small amount of a noble-metal hydrogenation component. This catalyst possesses the same... 

The Hysomer process produces an increase of about 12 octane numbers in suitable naphtha feedstocks. The process can be operated in conjunction with the Isosiv process (Union Carbide Corp.) for the separation of normal and isoparaffins, achieving complete isomerization of a C-5—C-6 stream. The combined process is trade named TIP (total isomerization process), and results in increases in octane numbers of about 20, rather than the 12 obtained with a once-through Hysomet treatment. 

Octane number is a measure of a fuel s abiUty to avoid knocking. The octane number of a gasoline is deterrnined in a special single-cylinder engine where various combustion conditions can be controlled. The test engine is adjusted to give trace knock from the fuel to be rated. Various mixtures of isooctane (2,2,4-trimethyl pentane) and normal heptane are then used to find the ratio of the two reference fuels that produce the same intensity of knock as that by the unknown fuel. 

By defining isooctane as having an octane number of 100 and / -heptane as having an octane number of 0, the volumetric percentage of isooctane in heptane that matches the knock from the unknown fuel can be calculated as the octane number of the fuel. For example, 90 vol % isooctane and 10 vol % normal heptane produce a 90-octane-number reference fuel. 

Sebacic acid is normally made from castor oil, which is essentially glyceryl ricinoleate. The castor oil is treated with caustic soda at high temperature, e.g. 250°C, so that saponification, leading to the formation of ricinoleic acid is followed by a reaction giving sebacic acid and octan-2-ol Figure 18.5. 

Because some hydrocracking occurs, Powerforming also produces saturated C to Q light hydrocarbons. The methane and ethane formed normally are consumed as refinery fuel. Propane and butane products are frequently marketed as LPG. The relative quantities of each of these products vary considerably with feed quality, operating conditions and octane severity. 

The octane number of a fuel is a measure of the tendency of the fuel to knock. The octane scale has a minimum and maximum based on the performance of reference fuels. In the laboratoi"y, these are burned under specific and preset conditions. One reference fuel is normal heptane. This is a very poor fuel and is given an octane rating of zero. On the opposite end of the scale is iso-octane (2,2,4 trimethyl pentane). Iso-octanc is a superior fuel and is given a rating of 100. 

---