Alkenes octane number

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 Spent acid is withdrawn as 90-92 wt% acid.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%. 

Summary of octane number aromatics, alkenes, and alkynes > cyclic alkanes and branched alkanes > straight-chain alkanes. 

Dehydrogenation (Reforming)17-20—to increase octane number of gasoline, to produce alkenes from alkanes [Eq. (1.2)], as well as aromatics, such as benzene, toluene, and xylenes [Eq. (1.3)] ... 

Isomerization of straight-chain to branched alkanes also increases the octane number, as do alkylates produced by alkene-isoalkane alkylation (such as that of isobutane and propylene, isobutylene, etc.). These large-scale processes are by now an integral part of the petroleum industry. Refining and processing of transportation fuels became probably the largest-scale industrial operation. 

Environmental considerations, including removal of lead additives as well as carcinogenic alkenes and aromatics from gasoline, increase the significance of isomerization to provide gasoline of suitable octane numbers. 

It is advantageous to pretreat butene feeds before alkylation.294-298 1,3-Butadiene is usually hydrogenated (to butenes or butane) since it causes increased acid consumption. The additional benefit of this process is that under hydrogenation conditions alkene isomerization (hydroisomerization) takes place, too. Isomerization, or the transformation of 1-butene to 2-butenes, is really attractive for HF alkylation since 2-butenes give better alkylate (higher octane number) in HF-cata-lyzed alkylation. Excessive 1,3-butadiene conversion, therefore, ensuring 70-80% isomerization, is carried out for HF alkylation. In contrast, approximately 20% isomerization is required at lower butadiene conversion for alkylation with H2SO4. 

Irisov 85) related octane number with free energy of formation for alkanes, alkenes, and alkynes. Correlations were said to be better than those by Kobayashi and Mibashan. 

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