TITLE: Diffusivities of Synthesis Gas and Fischer--Tropsch Products in Slurry Media: Final Report.

INST.  AUTHOR: Texas A and M Univ., College Station. Dept. of Chemical Engineering.

SPONSOR: Department of Energy, Washington, DC.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Department of Energy [DE],  1987,  121p.

NTIS ORDER NO.: DE88013683/INW  

ABSTRACT:

The task of estimating diffusion coefficients in a Fischer--Tropsch reactor is by no means elementary. The steady state liquid phase, often referred to as FT wax, is primarily a mixture of saturated hydrocarbons with an average carbon number of about 30, although it can range as high as 70. The melting point of the FT wax is typically in excess of 100/degree/C, and reaction conditions of the normal process range from 473-573 K at 1 to 5 MPa. Prior to this study, diffusion coefficients in even the simplest pure low melting hydrocarbons had not been measured at these conditions. The diffusion coefficients measured in this study are properly referred to an 'mutual diffusion coefficients at infinite dilution'. The mutual diffusion coefficient, D(sub 12), is the most common type of diffusion coefficient and is the diffusion coefficient required for mass transfer calculations. Often the mutual diffusion coefficient is simply referred to as the diffusivity of solute A in solvent B. Since most gases are only sparingly soluble in liquids, mutual diffusion coefficients for gases in liquids are always reported as being an infinite dilution.  Since liquid--liquid mixtures can exist over the entire concentration range, the effect of concentration on the liquid--liquid mutual diffusion coefficient can sometimes be important. However, for the case of diffusion in Fischer--Tropsch wax, the mutual diffusion coefficient at infinite dilution, D(sub 120), is the proper diffusion coefficient for design calculations. In this case, D(sub 120), represents the diffusion of infinitely dilute solute, 1, through the Fischer--Tropsch war mixture, 2.  This is precisely the situation occurring as a product or reactant diffuses to or form the surface of the FT catalyst. 79 refs. (ERA citation 13:056374)

REPORT  NUMBER: DOE/PC/70032-T2

CONTRACT  NUMBER: AC22-84PC70032