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Enhancement of Equilibrium Shift in Dehydrogenation Reactions Using a Novel Membrane Reactor Semi-Annual Report: September 1996-February 1997

Description: A mathematical model is developed to describe the permeation of hydrogen through thin-film palladium ceramic composite membrane in cocurrent flow configuration. Numerical simulation results show that the model under predicts reject composition and over predicts the product purity. These results suggest that the gas phase mass transfer resistance could be important. The difference between the predicted and actual hydrogen composition is less than 12%. Thus the model appears to be adequate for predicting the membrane module performance.
Date: January 7, 1998
Creator: Ilias, Shamsuddin & King, Franklin G.

Enhancement of Equilibrium Shift in Dehydrogenation Reactions Using a Novel Membrane Reactor Semi-Annual Report: March-September 1998

Description: Electroless deposition of palladium thin-films on a surface of microporous ceramic substrate has been used to develop a new class of perm-selective inorganic membrane. In the last report, we presented a numerical method to analyze the stability in single-stage gas permeation. In this reporting period, we present our modeling work on dehydrogenation of cyclohexane in Pd-Ceramic membrane reactor. A model for studying dehydrogenation of cyclohexane in a membrane reactor is developed. Radial diffusion is considered to account for the concentration gradient in radial direction due permeation through the membrane. The model equations are derived for systems with reaction and without reaction. In the non-reaction case, a mixture of argon, benzene, cyclohexane, and hydrogen is used in the reaction side and argon is used as sweep gas in the separation side. Currently, we are working on the details of numerical solution of the model equations.
Date: December 16, 1998
Creator: Ilias, Shamsuddin & King, Franklin G.

Enhancement of Equilibrium Shift in Dehydrogenation Reactions Using a Novel Membrane Reactor Semi-Annual Report: October 1998-February 1999

Description: Using electroless deposition of palladium thin-films on a microporous ceramic substrate, we developed a hydrogen-selective palladium-ceramic composite membrane. The new membrane has significantly higher permeability and selectivity for hydrogen than many of the commercially available dense-metallic membrane. The hydrogen permeability of the new membrane increases with increasing temperature. These properties make it an ideal candidate for use in membrane reactors to study dehydrogenation reactions by equilibrium shift. To investigate the usefulness of the new membrane in membrane reactor-separator configuration, a model for studying dehydrogenation of cyclohexane by equilibrium in a membrane reactor is developed. Radial diffusion is considered to account for the concentration gradient in the radial direction due to permeation through the membrane. The model is investigated with and without the reaction. In the non-reaction case, a mixture of argon, benzene, cyclohexane, and hydrogen is used in the reaction side and argon is used in the separation side. In the case of dehydrogenation reaction, the feed stream to the reaction side contained hydrogen and argon while in the separation side argon is used as sweep gas. Equilibrium conversion for dehydrogenation of cyclohexane is 18.7%. Present study shows that 100% conversion can be achieved by equilibrium shift using Pd-Ceramic membrane reactor. For a feed containing cyclohexane and argon of 164X10{sup -6} and 1.0x10{sup -3} mol / s, 98% conversion is achieved.
Date: April 30, 1999
Creator: Ilias, Shamsuddin & King, Franklin G.

Enhancement of Equilibrium Shift in Dehydrogenation Reactions Using a Novel Membrane Reactor Semi-Annual Report: September 1999-February 2000

Description: In our previous report we reported technical difficulties encountered in the fabrication of tubular membrane reactor using our Pd-ceramic composite membranes. Although the membrane is highly selective to hydrogen but in test runs we observed leakage of hydrogen from the end-seals and metallic fittings. This was a serious problem. An attempt to improve the seal by tightening was not helpful but resulted in cracks and breakage of the ceramic tube. To test the equilibrium conversion and equilibrium shift effect on dehydrogenation of cyclohexane to benzene and hydrogen in membrane reactor, we used Pd-ceramic discs in our diffusion cell as reactor packed with Pt-catalyst pellets. Test results show that by manipulating the feed (cyclohexane) flow rate and sweep gas flow rate (permeate side) we can have over 55% conversion as opposed to 18.7% equilibrium conversion under identical conditions. This demonstrates the usefulness of the new membrane in H{sub 2} separation and also in membrane-reactor configurations for equilibrium limited decomposition and dehydrogenation reactions.
Date: March 9, 2000
Creator: Ilias, Shamsuddin & King, Franklin G.