Thermodynamic Properties of Isobutane

Temperature Pressure Density Volume Int. energy Enthalpy Entropy C, CT Sound speed Joule-Thomson Therm, cond. Viscosity 

The uncertainties in density are 0.02% at temperatures below 340 K and pressures below 12 MPa (both liquid and vapor states), 0.3% at temperatures below 300 K and pressures above 12 MPa, 0.1% in the vapor phase between 340 and 450 K, and 0.5% elsewhere. In the critical region, deviations in pressure are 0.5%. Uncertainties in heat capacities are typically 1-2%, rising to 5% in the critical region and at temperatures below 200 K. Uncertainties in the speed of sound are typically 1-2%, rising to 5% at temperatures below 200 K and in the critical region. The uncertainty in viscosity varies from 0.4% in the dilute gas between room temperature and 600 K to 3.0% over the rest of the fluid surface. Uncertainty in thermal conductivity is 3%, except in the critical region and dilute gas which have an uncertainty of 5%. 

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Example 4.1. Thermodynamic properties of isobutane were measured at subcritical temperatures from 70°F (294.29°K) to 250°F (394.26°K) over a pressure range of 10 psia (68.95 kPa) to 3000 psia (20.68 MPa) by Sage and Lacey. Figure 4.1 is a log-log graph of pressure (psia) versus molal volume (fP/lbmole) of the experimental two-phase envelope (saturated liquid and saturated vapor) using the tabulated critical conditions from Appendix I to close the curve. Shown also is an experimental isotherm for 190°F (360.93°K). Calculate and plot 190°F isotherms for the R-K equation of state and for the ideal gas law and compare them to the experimental data. 

The values in these tables were generated from the NIST REFPROP software (Lemmon, E. W., McLinden, M. O., and Huber, M. L., NIST Standard Reference Database 23 Reference Fluid Thermodynamic and Transport Properties—REFPROP, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, Md., 2002, Version 7.1). The primary source for the thermodynamic properties is Buecker, D., and Wagner, W, Reference Equations of State for the Thermodynamic Properties of Fluid Phase n-Butane and Isobutane, /. Phys. Chem. Ref Data 35(2) 929-1019, 2006. The source for viscosity is Vogel, E., Kuechenmeister, C., Bich, E., and Laesecke, A., Reference Correlation of the Viscosity of Propane, /. Phys. Chem. Ref Data 27(5) 947-970, 1998. The source for thermal conductivity is Marsh, K., Perkins, R., and Ramires, M. L. V, Measurement and Correlation of the Thermal Conductivity of Propane from 86 to 600 K at Pressures to 70 MPa, /. Chem. Eng. Data 47(4) 932-940, 2002. 

Substances considered in a compilation of the thermodynamic properties of refrigerants include hydrogen, parahydrogen, helium, neon, nitrogen, air, oxygen, argon, carbon dioxide, hydrocarbons (e.g. methane, ethane, propane, butane, isobutane, ethylene, and propene), and fluoro-and fluoro-chloro-hydrocarbons. Properties listed include those for the liquid and saturated vapour, superheated vapour, and unsaturated vapour. In addition, pressure-enthalpy, and in some instances pressure-entropy, diagrams are provided. 

Biicker, D., and Wagner, W, Reference Equations of State for the Thermodynamic Properties of Fluid Phase n-Butane and Isobutane, J. Phys. Chem. Ref. Data 35, 929, 2006. 

The properties of butane and isobutane have been summarized ia Table 5 and iaclude physical, chemical, and thermodynamic constants, and temperature-dependent parameters. Graphs of several physical properties as functions of temperature have been pubUshed (17) and thermodynamic properties have been tabulated as functions of temperature (12). 

S. S. Chen, R. C. Wilhoit and B. J. Zwolinski, Ideal gas thermodynamic properties and isomerization of n-butane and isobutane , J. Phys. Chem. Ref. Data, 4, 859 (1975). Review and evaluation of structural parameters (including vibrational frequencies and internal rotation properties) tabulation of thermodynamic properties [C°, S°, (H°-H°)/T, (G°-H°)/T] for 0statistical thermodynamic methods (RRHO approximation). 

This paper presents experimental results for the equilibrium adsorption of the shorter unbranched hydrocarbons, ethane, ethene, propane, and propene and of the linear and branched C4 alkanes n-butane and isobutane on Kureha activated carbon, a purely microporous material. The aim of the present study is to investigate comparative packing efficiencies of these light alkanes and alkenes and of the linear and branched C4 alkanes inside the adsorbent pores. An interpretation of the difference in the adsorption behaviour for these six adsorptives is given. In addition, thermodynamic properties like isosteric heat associated with adsorption are presented to characterize interactions between adsorptive and adsorbent and an outlook on mixture adsorption is discussed for this carbon. 

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