Critical properties and vapor pressure equation for alkanes CnH2n+2: Normal alkanes with n <= 36 and isomers for n=4 through n=9

A correlation for estimating the vapor pressure of normal alkanes from meth ane through n-hexatriacontane and isomers of butane to nonane is reported, This work extends the correlation for normal alkanes (CnH2n+2), with n less than or equal to 20, reported by Ambrose, to both normal alkanes with n le ss than or equal to 36 and their isomers with n less than or equal to 9. Th is vapor pressure equation was based on the Wagner equation and is similar to that used by Ambrose. Literature vapor pressure measurements have been r eviewed. Tables are given that list the type of apparatus, measurement rang e and precision, and chemical purity. These criteria were initially used to select measurements for inclusion in the regression analyses to determine the coefficients of the correlation, Vapor pressures estimated from the cor relation were compared with all vapor pressure (p(1+g)) measurements review ed in this work. At pressures greater than 1 kPa, the vapor pressure equati on presented here has the following accuracies: 0.0001.p(1+g) for methane, 0.001.p(1+g) for ethane, propane, and n-butane, 0.002.p(1+g) for n-pentane through n-octane, 2-methylpropane, and 2-methylbutane, 0.005.p(1+g) for 2,2 -dimethylpropane, n-nonane, n-decane, and the isomers of hexane through non ane, 0.01.p(1+g) for n-undecane to n-hexadecane, 0.02.p(1+g) for n-heptadec ane to n-eicosane, 0.05.p(1+g) for n-heneicosane to n-octacosane, and 0.10. p(1+g) for n-nonacosane to n-hexatriacontane, Equations for the critical te mperatures and pressures of the normal alkanes as functions of the carbon n umber are also reported. (C) 2000 American Institute of Physics. [S0047-268 9(90)00201-X].