Conclusions TAP approach can be effectively used for transport studies

1. Pulse valve adsorption desorption Empty Pore Catalyst zone Inert zone Occupied Pore Occupied Pore Reactant mixture t Microreactor Catalyst diffusion diffusion Occupied Brønsted Acid Site Mass spectrometer Vacuum (10-8 torr) Results and Discussion Introduction • Problem: Safety, environmental and reliability issues associated with current liquid acid alkylation technologies • Challenge: Develop and demonstrate an environmentally friendly and competitive Solid Acid Catalyst (SAC) technology to replace HF and H2SO4 technologies • Different solid acid catalysts are tested for alkylation of isobutane and n-butene to form 2,2,4 trimethylpentane (gasoline) • Zeolites • Supported Nafion • Hetropoly acids • Ion exchange resins • Zeolites • High product selectivity (~ 85 – 95 %) • Rapid decrease in activity Modified residence time vs. inverse square root temperature for isobutane and argon over beta-zeolities Modified residence time vs. inverse square root temperature for isobutane and argon over inert quartz particles Adsorption/Desorption Studies on Solid Acid Alkylation CatalystsS.V. Nayak, M.P. Dudukovic, and P. A. Ramachandran Chemical Reaction Engineering Laboratory, Washington University in St.Louis Residence time divided by the square root molecular weight vs. inverse square root of temperature (Nayak et al., 2007) The catalytic cycle in alkylation reaction catalyzed by zeolites TAP experimental responses of argon and isobutane over beta-zeolites Single Pulse TAP Experiments Mean = Adsorption Capacity Spread = Diffusivity, Adsorption/ Desorption Constants Important questions How do organic molecules diffuse inside a nanoporous zeolite? How does the intra-crystalline channel network of a zeolite influence diffusion, adsorption/ desorption and reaction pathway of organic molecules? van’t Hoff plot for equilibrium constant (Nayak et al., 2007) Theoretical Representation of TAP Inert Zone II Inert Zone I Zeolite Zone Table1: Heat of Adsorption and pre-exponential factor (Nayak et al., 2007) Sub-Project Goal To understand and quantify the overall adsorption kinetics and transport processes of the reactant and products involved in Solid Acid Alkylation Processes Narrow Inlet BC Vacuum BC at outlet Observed Exit Flow Methodology Adsorption-Desorption and Intraparticle Diffusion model for Zeolite Zone Using LDF approximation(Nayak et al., 2008) TAP Reactor Model: Accumulation - Transport Term = Reaction Rate • Conclusions • TAP approach can be effectively used for transport studies • Experimental procedure and method for quantifying TAP results are presented • The understanding gained with TAP results should help in quantifying the frequency for periodic regeneration and the key features needed for the optimal catalysts design and regeneration techniques for solid acid alkylation processes Diffusion Knudsen Diffusion • References: • Nayak S. V., Ramachandran P. A., Dudukovic M. P., 2007 “Transport in nanoporous Beta and ultrastable Y zeolite”, AIChE,fall meeting • Nayak S. V., Ramachandran P. A., Dudukovic M. P., 2008 “Adsorption-desorption and intraparticle diffusion model using LDF approximation”, in preparation • Acknowledgement: NSF Grant, EEC-0310689 Temporal Analysis of Products (TAP) Pulse Response Experiment