Systems, isobutylene-propane

As discussed in Sec. 4, the icomplex function of temperature, pressure, and equilibrium vapor- and hquid-phase compositions. However, for mixtures of compounds of similar molecular structure and size, the K value depends mainly on temperature and pressure. For example, several major graphical ilight-hydrocarbon systems. The easiest to use are the DePriester charts [Chem. Eng. Prog. Symp. Ser 7, 49, 1 (1953)], which cover 12 hydrocarbons (methane, ethylene, ethane, propylene, propane, isobutane, isobutylene, /i-butane, isopentane, /1-pentane, /i-hexane, and /i-heptane). These charts are a simplification of the Kellogg charts [Liquid-Vapor Equilibiia in Mixtures of Light Hydrocarbons, MWK Equilibnum Con.stants, Polyco Data, (1950)] and include additional experimental data. The Kellogg charts, and hence the DePriester charts, are based primarily on the Benedict-Webb-Rubin equation of state [Chem. Eng. Prog., 47,419 (1951) 47, 449 (1951)], which can represent both the liquid and the vapor phases and can predict K values quite accurately when the equation constants are available for the components in question. 

In systems where the hydroxyl is on a secondary or tertiary carbon, neighboring hydroxyl participation can occur. For example, the acid hydrolysis of I-chloro-2-methyl-propan-2-ol gives isobutyraldehyde as well as isobutylene glycol (i8). 

Reaction pressure was maintained with a dome-loaded back-pressure regulator (Circle Seal Controls). All heated zones were controlled and monitored with a Camile 2500 data acquisition system (Camile Products). Products were analyzed online by gas chromatography with an HP 5890 II GC, equipped with an FID, and a DB-Petro 100 m column (J W Scientific), operated at 35° C for 30 min, ramped at 1.5°/min to 100° C, 5°/min to 250° C for 15 min. An alkylate reference standard (Supelco) allowed identification of the trimethylpentanes (TMP) and dimethylhexanes (DMH). The combined mass of TMP and DMH is referred to hereafter as the alkylate product . As discussed elsewhere [19], propane, an impurity in the isobutane feed, was used as an internal standard for butene conversion calculations. Since isomerization from 1-butene to 2-butene isomers is rapid over acidic catalysts, reported conversion is for all butene isomers to C5 and higher products. Isobutylene formation was not observed under any conditions. 

Fio. 3-6. Vapor-liquid curves for system propane-isobutylene. 

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