Isopentane data

Nearly all experimental eoexistenee eurves, whether from liquid-gas equilibrium, liquid mixtures, order-disorder in alloys, or in ferromagnetie materials, are far from parabolie, and more nearly eubie, even far below the eritieal temperature. This was known for fluid systems, at least to some experimentalists, more than one hundred years ago. Versehaflfelt (1900), from a eareflil analysis of data (pressure-volume and densities) on isopentane, eoneluded that the best fit was with p = 0.34 and 8 = 4.26, far from the elassieal values. Van Laar apparently rejeeted this eonelusion, believing that, at least very elose to the eritieal temperature, the eoexistenee eurve must beeome parabolie. Even earlier, van der Waals, who had derived a elassieal theory of eapillarity with a surfaee-tension exponent of 3/2, found (1893)... 

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. 

The composition of the feed to a debutaniser is given below. Make a preliminary design for a column to recover 98 per cent of the n-butane overhead and 95 per cent of the isopentane from the column base. The column will operate at 14 bar and the feed will be at its boiling point. Use the short-cut methods and follow the procedure set out below. Use the De Priester charts to determine the relative volatility. The liquid viscosity can be estimated using the data given in Appendix D. 

Fig. 12.4. Vapor-to-water transfer data for saturated hydrocarbons as a function of accessible surface area, from [131]. Standard states are 1M ideal gas and solution phases. Linear alkanes (small dots) are labeled by the number of carbons. Cyclic compounds (large dots) are a = cyclooctane, b = cycloheptane, c = cyclopentane, d = cyclohexane, e = methylcyclopentane, f = methylcyclohexane, g = cA-l,2-dimethylcyclohexane. Branched compounds (circles) are h = isobutane, i = neopentane, j = isopentane, k = neohexane, 1 = isohexane, m = 3-methylpentane, n = 2,4-dimethylpentane, o = isooctane, p = 2,2,5-tri-metbylhexane. Adapted with permission from [74], Copyright 1994, American Chemical Society...

In a review of the fire and explosibility hazards of this group, data on 15-50% solutions of trimethyl- and triisobutyl-aluminium in isopentane and in hexane are... 

One important application of analysis of variance is in the fitting of empirical models to reaction-rate data (cf. Section VI). For the model below, the analysis of variance for data on the vapor-phase isomerization of normal to isopentane over a supported metal catalyst (Cl)... 

An augmented central composite design was used in obtaining reaction-rate data in a flow differential reactor the reaction occurring was the isomerization of normal pentane to isopentane in the presence of hydrogen (Cl). Using the subscripts 1, 2, and 3 for hydrogen, normal pentane, and isopentane respectively, an empirical rate equation can be written... 

Theoretical studies on N-methylborazine and N-dimethylborazine predict an electron-density on the boron atoms adjacent to the N-methyl group which is greater than that for the parent borazine molecule. This fact would lead to the expectation that para substitution is favored in the reaction of photoexcited N-methylborazine with ammonia, due to the lower electron density at the para site. However, B NMR data and H- N coupling constant results predict a lower electron density at the ortho site. The photochemical results are in accord with this latter prediction. Beachley produced 70% para B-chloro-N-methylborazine in the substitution reaction of HgCl2 with N-methylborazine in isopentane solution. Because this reaction has been shown to occur by a bimolecular exchange mechanism, these results can be explained by steric factors in the same manner as the HN(CH3)2 and CH3OH photochemical results. 

AM. Kettle No. 3 discharge piping cracks. Contents of kettle start dumping to the curb. Isopentane vapors spread as material flashes. (Concluded from data). 

Ostergaard, K.K. Tohidi, B. Danesh, A. Burgass, R.W. Todd, A.C. (2001). Equilibrium data and thermodynamic modelling of isopentane and 2,2-dimcthylpcntanc hydrates, h luid Phase Equilibria, 169, 101-115. 

The group contribution method, which is conveniently packaged in the software Cranium, can be useful when experimental data and correlations are not available. Let us consider the properties of pentane, isopentane, and neopentane. 

In methanol, the extinction of the absorption at 241 nm is less than 40 % of the value in isopentane with little change on lowering the temperature. In isopentane, the extinction drops significantly to the value found in methanol when the temperature is lowered. The data on the temperature-dependent CD in methanol can be interpreted on the basis of a temperature-dependent equilibrium between two chiral species. The change of the rotatory strength appears to be AG° = —2.0 KJ mol-1. This phenomenon is interpreted by the assumption that the cis-conformer about the C(6)-C(7) bond is favored in methanol and, at lower temperatures, in isopentane. 

Fig. 8. Experimental integral permeability data for PC-C02 pure C02 O in the presence of 117.8 torr of isopentane on the upstream side (P. = 0) 71>...

FIGURE 6.33 Data for structure H hydrates of methane with isopentane, neohexane, 2,3-dimethylbutane, and sodium chloride inhibition of hydrates of methane with isopentane, neohexane, and tert-butyl methyl ether. 

Figure 6.37 Data for structure H hydrates of methane with 2,3-dimethylbutane, isopentane, and neohexane.

The same phenomenon was observed61 with propane (Figure 5.6) and isopentane (Figure 5.7) above 20 mol% of SbF5, reversible protonation and protolytic ionization decrease rapidly whereas the conversion of the alkane with concomitant reduction of SbF5 increases. H-D exchange data observed in small alkanes are collected in Table 5.1. 

The data shown in Figure 8 illustrate the reduction in permeability of polycarbonate to CO2 caused by competition between isopentane and CO2 for Langmuir sorption sites (33) ... 

Rothe (5, , 1 5) calculated the aroma values of some volatiles identified in the crumb of wheat bread and the crust of rye bread. The data listed in Table I indicate that ethanol, isobutanal, iso-pentanal, diacetyl and isopentanol contribute with high aroma values to the aroma of the wheat bread crumb. During baking of rye bread, the two Strecker aldehydes, isobutanal and isopentanal, increased so much in the crust that they showed the highest aroma values of the volatiles investigated. 

The temperature of isomerization controls equilibrium isomer composition, and thereby product octane. Figure 4.8 is a plot of isopentane in the C5 product as a function of temperature. The data are from pilot plant runs with three types of commercial UOP isomerization catalysts. The feedstock was a 50/50 mixture of normal pentane and normal hexane, containing about 6% cyclics. The 1-8 and I-80 catalysts are very active at a low temperature, where equilibrium isopentane content is highest. The acid functions in 1-8 and 1-80 are chlorided aluminas. The zeolitic catalyst, HS-10 , requires relatively high temperatures of operation. The LPI-100 catalyst contains sulfated zirconia as the acid function and falls in the middle of the temperature range (12). Due to the equilibrium constraints, a lower temperature operation yields a higher octane product. The 1-8 and 1-80 catalysts yielded Research Octane Numbers of 82-84, as compared to 80-82 for LPI-100 catalyst and 78-80 for HS-10. 

Semikinetic modeling is illustrated by a generalized model for naphtha pyrolysis. The empiricism associated with the semikinetic model dictates the need for an extensive data base for parameter estimates. The naphtha data base consists of about 400 tests covering pure components and their mixtures and 17 naphthas (25). The pure components studied were normal and isopentanes, cyclohexane, and n-heptane. The wide range of naphtha feed properties is summarized in Table III. 

The data given for a reaction temperature of 300°C clearly showed the mordenite catalyst to be the more active for isomerization of both the C5 and Ce fractions. Conversions quoted were precious-metal-H-mordenite C5 —65 wt %, Cq >— 15 wt % precious metal-H-Y C5 — 40 wt %, Ce 4 wt %. These data suggest that the pentane fraction may be slightly easier to isomerize over mordenite than the hexane. The equilibrium conversions to isopentane and 2,2-DMB at 300°C are in the vicinity of 65 and 18 wt %, respectively. A possible explanation is that impurities present—e.g., cyclohexane and/or benzene—aifect the rate of 2,2-DMB formation more than that of the isopentane. 

Fig. 2. Relative scale of the Tc of the main HTSC groups and solidification points of different mixed solvents chloroethane + butyronitrile (I), n-pentane + methylcyclohexane + n-propanol (II), bromo-ethane + butyronitrile + isopentane + methylcyclopentane (III), chloromethane + dimethyl ether (IV), bromoethane + butyronitrile (V), propionitrile + butyronitrile (VI), methanol + dichloromethane (VII), ammonia + isopropanol + dimethylformamide (VIII). Data are taken from [28, 152].

---