Hydrocarbons thermodynamic data

A second objective was to provide a balance between hydrate experimental and theoretical perspectives. The monograph was intended as a single record of the majority of hydrocarbon thermodynamic data obtained since 1934, the time of discovery of hydrates in pipelines. The third edition, in particular, shows the transition away from thermodynamics to kinetics, as mankind learns to study more sophisticated, time-dependent phenomena. 

American Petroleum Institute, Bibliographies on Hydrocarbons, Vols. 1-4, "Vapor-Liquid Equilibrium Data for Hydrocarbon Systems" (1963), "Vapor Pressure Data for Hydrocarbons" (1964), "Volumetric and Thermodynamic Data for Pure Hydrocarbons and Their Mixtures" (1964), "Vapor-Liquid Equilibrium Data for Hydrocarbon-Nonhydrocarbon Gas Systems" (1964), API, Division of Refining, Washington. 

Example of NHV calculation for toluene based on thermodynamic data from Thermodynamic Tables - Hydrocarbons" edited by TRC (Thermodynamic Research Center, The Texas A M University System College Station, Texas, USA). 

Thermodynamic data are available only for the lower alkylamines, mainly estimates based on a few experimental deterrninations (3,4). Many manufacturing processes appear to be limited by thermodynamic equiUbria. The lack of accurate free energy data for these amines limits the appHcation of thermodynamic considerations, in contrast to the situation in hydrocarbon technology. 

B. D. Smith and R. Srivastava, Thermodynamic Data for Pure Compounds Part A.. Hydrocarbons and Ketones, Elsevier, Amsterdam, the Netherlands, 1986. T. Boubhk, V. Eried, and E. Hala, The Hapour Pressures of Pure Substances, 2nd ed., Elsevier, Amsterdam, the Netherlands, 1984. 

If the thermodynamic data for a compound of interest have not been determined and abulated, it may be possible to estimate AHf or AGj from tabulated data pertaining to dividual structural units. Procedures have been developed for estimating thermodynamic characteristics of hydrocarbons and derivatives by summing the contributions of the constituent groups. The group increments are derived from experimental thermochemical iata and therefore depend on the existence of reliable data for the class of compounds of merest. 

Existing processes for producing oil and gas products have required the development of phase behavior and other thermodynamic data on light hydrocarbons, heavy hydrocarbons, and the acid gases CO2 and HoS. For this reason a lot of basic data are available on these systems but there is still a lot we don t know such as how to characterize the behavior of hydrocarbon fractions containing numerous paraffin, naphthene, and aromatic components. Additional basic data on these systems would help to improve the efficiency of these existing processes. 

Despite the importance of mixtures containing steam as a component there is a shortage of thermodynamic data for such systems. At low densities the solubility of water in compressed gases has been used (J, 2 to obtain cross term second virial coefficients Bj2- At high densities the phase boundaries of several water + hydrocarbon systems have been determined (3,4). Data which would be of greatest value, pVT measurements, do not exist. Adsorption on the walls of a pVT apparatus causes such large errors that it has been a difficult task to determine the equation of state of pure steam, particularly at low densities. Flow calorimetric measurements, which are free from adsorption errors, offer an alternative route to thermodynamic information. Flow calorimetric measurements of the isothermal enthalpy-pressure coefficient pressure yield the quantity 4>c = B - TdB/dT where B is the second virial coefficient. From values of obtain values of B without recourse to pVT measurements. 

Since the solvent properties of dimethyl sulfoxide are widely different from those of hydrocarbons and halogenated hydrocarbons, it may be difficult to compare the kinetic and thermodynamic data for the C02H group (Table 16) directly with others. However, heating the carboxylic acid (68, X = OH) in toluene affords the sp isomer almost exclusively. Probably, the observed results with the carboxylic acid derive from difficulty in the formation of a hydrogen bond owing to a steric effect, in addition to the nonplanar conformation of the carboxyl group relative to the naphthalene. 

Brown and Melchiore (1966) have recently determined the temperature-dependence of complex formation of aromatic hydrocarbons with HCl and HRr in n-heptane solution. Dissociation constants and thermodynamic data were calculated. 

If the assumption that the entropy of the reaction according to equation (5) is independent of the aromatic substance applies, the entropy contribution TAS must assume a constant value. Mackor et al. (1958b) were able to demonstrate the correctness of this assumption by determining the thermodynamic data for some methylbenzenes and condensed aromatic hydrocarbons. Whereas AH and AO change considerably, the entropy term TAS remains largely unaltered (Table 21). 

TRC Thermodynamic Tables-Hydrocarbons, Thermodynamics Research Center The Texas A M University System, College Station, TX (Loose-leaf Data Sheets). 

So acute was the need for accurate data on freezing point, boiling point, refractive index, density, and the spectrographic fingerprints of pure hydrocarbons that two new projects were set up. These included A.P.I.-R.P. 44, a project for the collection, evaluation, and distribution of physical, chemical, and thermodynamic data (1), and A.P.I.-R.P. 46, a project for the preparation and distribution of standard spectrometric samples (3). A.P.I.-R.P. 45 made substantial contribution to these new ventures. 

The volume of tabular information necessary to record in detail the thermodynamic data for the paraffin hydrocarbons and their mixtures, as was done for steam, is excessive. It appears hopeful that graphical generalizations typified by the work of Edmister (19) will prove adequate for the less rigorous requirements of design, whereas the Benedict equation of state (4) may be employed where precision is necessary. However, the effective application of this equation of state to compounds containing more than four carbon atoms per molecule still awaits the evaluation of the constants. After the composition and specific volume have been established for a particular state, the solution of equations of state to establish enthalpy and entropy is a straightforward process. 

Auerbach et al. (101) used a variant of the TST model of diffusion to characterize the motion of benzene in NaY zeolite. The computational efficiency of this method, as already discussed for the diffusion of Xe in NaY zeolite (72), means that long-time-scale motions such as intercage jumps can be investigated. Auerbach et al. used a zeolite-hydrocarbon potential energy surface that they recently developed themselves. A Si/Al ratio of 3.0 was assumed and the potential parameters were fitted to reproduce crystallographic and thermodynamic data for the benzene-NaY zeolite system. The functional form of the potential was similar to all others, including a Lennard-Jones function to describe the short-range interactions and a Coulombic repulsion term calculated by Ewald summation. 

Thermodynamic data on hydrocarbons show that at temperatures above 1300°C. ethylene, acetylene, and carbon are more stable than methane or other saturated hydrocarbons however, although data of this kind will indicate the species likely to be formed at high temperatures, the amounts of unsaturated hydrocarbons and carbon produced will depend on the rates of the reactions involved and on the temperature cycle used. 

Good thermochemical values for halogenated compounds have lagged behind those for hydrocarbons. Until recent years only the crudest estimates were available, even for some of the most common compounds. Now, however, reliable thermodynamic data have become available for some species, though there is still uncertainty for many other species, especially those containing oxygen. 

At a sea salt concentration totaling 3.5 wt%, using the thermodynamic data of Dholabhai et al. (1991) in Chapter 6, a pressure of 4.364 MPa (a minimum seawater depth of 436 m—about 55 m deeper than in pure water) is required to stabilize hydrates at 277 K. Further corrections to the phase boundary are required considering effects of (1) hydrocarbons other than methane, (2) salt concentrations other than 3.5 wt%, and (3) sediment pores or capillary pressure, as indicated in Chapter 5. 

Hydrocarbon Processing excellent flowsheets, thermodynamic data series, and major articles. 

On the basis of the regular behavior of the heat capacity, Gill and Wadso125) were able to summarize the thermodynamic data for the hydrophobic interaction of hydrocarbons as... 

D.2. Determination of Kx from Thermodynamic Data for Alcohol—Hydrocarbon Mixtures. Using the available excess Gibbs energy and excess enthalpy data for alcohol—hydrocarbon mixtures,16 the value of Kx can be estimated as described below. The Gibbs energy of the... 

A certain kind of radical transfer can be modelled by the transfer of a hydrogen atom from an alkane molecule to a small alkyl radical. This reaction was studied in detail in the gas phase. With hydrocarbon partners, heats of reaction are a fairly safe measure of the relative rate of transfer, as the pre-exponential Arrhenius factors remain approximately constant for a series of transfers to a given radical. Tabulated thermodynamic data indicate, however, [31, 32] that the correlation between the heat of reaction and the transfer rate is not valid for reactions of a radical with polar substrates [32, 33], In condensed phases, transfer reactions have not been sufficiently studied. Polymerizations themselves are the source of the most valuable, though incomplete, information. 

Also, relevant thermodynamic data (Table 4.2) indicate that the rise of the methane pressure during standard aromatization of C2 C4 alkanes must result in the direct insertion of methane into aromatic hydrocarbons at 720 770 K (450 500°C) that is, by reaction 2C3H8 -F CFI4 CgFIsCFIs + 6FI2 (see Table 4.2). 

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