Gasoline-range molecules

Alkylation in petroleum processing produces larger hydrocarbon molecules in the gasoline range from smaller molecules. The products are branched hydrocarbons having high octane ratings. 

In Table II, the product yields of REY-PILC are compared with PILC, a commercial equilibrium catalyst, and with the same commercial catalyst that had been deactivated in the laboratory to near constant conversion. The addition of REY to PILC maintained activity in the presence of steam while coke yield was reduced and the LCO/HCO ratio was slightly higher than for either of the commercial catalysts. This suggests that the microstructure of the PILC after pretreatment D will still convert large molecules into gasoline range products instead of generating coke as seen in PILC alone. 

Butenes are used extensively in gasoline production to produce high-octane gasoline compounds. In alkylation reactions, butenes combine with isobutane to produce branched gasoline-range compounds (see Butane). Isooctane can be produced by dimerization of isobutene in the presence of sulfuric acid. Dimerization is the combination of a molecule with itself to produce a molecule called a dimer. The dimer has exactly twice the number of atoms in the original molecule. Therefore the dimerization of isobutene produces two dimers with the formula C H,... 

This seems to indicate that mono-aromatics shifting from the feed to the gasoline range due to shattering of large molecules can be enhanced by higher reactor bottom temperatures. 

By way of definition of some of these processes, polymerization is the conversion of gaseous olefins such as propylene and butylene into larger molecules in the gasoline range. 

The naphtha fraction is dorninated by saturates having lesser amounts of mono- and diaromatics (Table 2, Eig. 4). Whereas naphtha (ibp to 210°C) covers the boiling range of gasoline, most raw petroleum naphtha molecules have a low octane number and most raw naphtha is processed further, to be combined with other process naphthas and additives to formulate commercial gasoline. 

Polymerization is a reaction in which several molecules of the same or similar material combine to form a larger molecule. We will only discuss the polymerization of C3, C4, and C5 olefins to products in the gasoline boiling range (C5 - Cl2). A typical reaction which occurs in polymerization is illustrated in Figure 24. 

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