Carbon dioxide hydrogenation, correlations

It is common in natural-gas engineering to calculate the viscosity of a sour gas mixture using a two-step procedure. First, you estimate the viscosity of a sweet gas at the temperature and pressure of interest. This viscosity is corrected for the presence of hydrogen sulfide and carbon dioxide. Such correlations are usually limited to a small amount of acid gas and thus are not applicable to acid gas mixtures. Therefore, a different approach must be used for acid gas. 

Rate expressions of this type have been proposed to correlate the data for the reaction between hydrogen and carbon dioxide on tungsten. 

The results report in Figure 4a show that there is no linear correlation between the basic activity and the carbon dioxide retained at RT. In the case of eta and gamma, some basic sites were detected by C02 adsorption but could not be active in hydrogen transfer at 250°C. 

Of the problems presented, correlation of the NH3-CO2-H2S-H2O system is most important. Data that might be used for direct empirical correlation of partial pressures or fugacities with total concentrations of ammonia, carbon dioxide, and hydrogen sulfide in the liquid are available for relatively limited ranges... 

Table IX. CORRELATION EQUATIONS FOR SALTING-OUT OF AMMONIA, CARBON DIOXIDE, AND HYDROGEN SULFIDE...

Kobe Murti determined by Macleod method values a, A, B C for several compds which have been used by Rush Gamson. These compds included ethane, propane, pentane, heptane, cyclohexane, hydrogen, oxygen, benzene, CCI2F2, carbon dioxide, decane and chlorine. The results were similar to those repotted by R G but better correlation was obtd... 

A systematic attempt to correlate the catalytic effect of different surfaces with their adsorptive capacity was made by Taylor and his collaborators. Taylor and Burns, for example, investigated the adsorption of hydrogen, carbon dioxide, and ethylene by the six metals nickel, cobalt, palladium, platinum, iron, and copper. All these metals are able to catalyse the hydrogenation of ethylene to ethane, while nickel, cobalt, and palladium also catalyse the reduction of carbon monoxide and of carbon dioxide to methane. 

SCF carbon dioxide is a lipophilic solvent since the solubility parameter and the dielectric constant are small compared with a number of polar hydrocarbon solvents. Co-solvents(also called entrainers, moditiers, moderators) such as ethanol have been added to fluids such as carbon dioxide to raise the solvent strength while maintaining it s adjustability. Most liquid cosolvents have solubility parameters which are larger than that of carbon dioxide, so that they may be used to increase yields, or to decrease pressure and solvent requirements. A summary of the large increases in solubility that may be obtained with a simple cosolvent is given at the top of Table I. Cosolvents, unlike carbon dioxide, can form electron donor-acceptor complexes (for example hydrogen bonds) with certain polar solutes to influence solubilities and selectivities beyond what would be expected based on volatilities alone. Several thermodynamic models have been developed to correlate and in some cases predict effects of cosolvent on solubilities( ,2). They are used extensively in SCF research and development... 

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