Optimum temperature profiles during the pyrolysis of ethane exist because the yield goes up with increasing temperature, but consequently, the reactor must be shut down and cleaned out with increasing frequency because the carbon formed deposits along the reactor wall causing high pressure drop. The combined effect causes the yearly production of ethylene to go through an optimum. To find this optimum, a computer program was developed with the ability of handling 25 simultaneous reactions involving up to 25 components. It calculates the carbon deposition profile and the changing pressure profiles, as a function of a predetermined reaction gas temperature profile. The reactor will remain in production until the inlet pressure exceeds 8 atm. The average yearly production rate is calculated, assessing a reactor shut down penalty of 24 and 48 hr required for the cleaning of the clogged pyrolysis tubes. The optimum exit temperature for the 24-hr penalty was 1127°K with a corresponding 59% one pass ethane conversion. The 48-hr penalty lowers the optimum exit temperature to 1124°K and a 50.5% ethane conversion. The practice of increasing pressure to compensate for carbon buildup results in accelerated carbon deposition and is detrimental to the overall production scheme.

This article describes a 10-year cooperative effort between the U.S. National Institute of Standards and Technology (NIST) and five major journals in the field of thermophysical and thermochemical properties to improve the quality of published reports of experimental data. The journals are Journal of Chemical and Engineering Data, The Journal of Chemical Thermodynamics, Fluid Phase Equilibria, Thermochimica Acta, and International Journal of Thermophysics. The history of this unique cooperation is outlined, together with an overview of software tools and procedures that have been developed and implemented to aid authors, editors, and reviewers at all stages of the publication process, including experiment

A statistical mechanical solution theory is used as the basis for corresponding states formulations. Universal functions relate the compressibility to the reduced density and the partial molar volume to reduced solvent density only. Correlations are in good agreement with data for all types of nonelectrolytes over wide ranges of temperatures including saturated and compressed systems. The correlations provide simple methods for describing the isothermal pressure dependence of liquid volumes and the pressure dependence of the ideal-solution solubility of gases in liquids. S. CONCLUSIONS AND SIGNIFICANCEFor all liquids the product of compressibility times temperature can be expressed to a high degree of accuracy as a simple function of reduced density only, Equation The single reducing volume is the critical volume for nonpolar substances but is empirically fitted for polar substances. The form of this relation allows a simple expression for the change in volume with an isothermal change in pressure and the entire liquid state can be described from the saturation volumes and the present correlation.The partial molal volume of gases at infinite dilution in liquids can be obtained to within a few yo from a simple function of reduced density of the solvent and the reducing volumes of the gas and solvent, Equations (9) to (11). This generalized expression provides the means to correct for the effect of pressure on Henry's constant as used to predict solubilities of gases. However, the present equation does not describe the partial molal volume of liquids in liquids; apparently the liquid volumetric behavior is different when a substance is above its critical temperature. The expressions for both compressibility and partial molal volume arise from use of a statistical mechanical solution theory involving integrals of the molecular direct correlation function. Their universality can be attributed to the lack of importance of nonspherical forces in the integral of the correlation function. However, it is not clear why the integrals are independent of temperature in the liquid region since essentially complete cancellation of the effects of temperature must occur in the (positive) long range and (negative) short range values of the correlation functions and there is no molecular theory which would predict this. THERMODYNAMIC PROPERTIESA knowledge of the compressibility of the liquidFor mixtures the partial molal volume is useful to de-scribe the volumetric behavior v = 8 x i u i (3) can be used to generate the equation of state for the liquid along an isotherm since the change of pressure which ocand to correct for the pressure dependence of liquid fugaccurs with a change in density is ity f

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Data for the partial molar volume at infinite dilution for several gaseous solutes and H3BO3 in water have been correlated using a generalized Krichevskii parameter. The result is a simple function for in terms of the water density and compressibility for conditions from ambient to 725 K and 40 MPa. The accuracy is much better with only two parameters than with a previous five-parameter model.

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A systematic approach is suggested for predicting the solubility of sparingly soluble solid fine chemicals and pharmaceuticals. The procedure uses group contribution methods for computing the difference in solubility at infinite dilution in the solvent of interest from an optimal reference solvent with the aim of (1) minimizing the impact of uncertainties in pure-solute properties, (2) decreasing the number of adjustable parameters to be determined by data reduction, and (3) using appropriate experimental data to fit unknown parameters. Several examples illustrate the method.