Center for Environmentally
Beneficial Catalysis

  • Home
  • New Fundamental Insights Into Adsorption/Desorption Behavior Using Real Time TEOM Measurements

New Fundamental Insights Into Adsorption/Desorption Behavior Using Real Time TEOM Measurements

Friday, February 20, 2009

The Tapered Element Oscillating Microbalance (TEOM) was demonstrated to be a valuable tool for elucidating the adsorption/desorption characteristics of alkylation reactants on microporous and mesoporous catalysts.. The catalyst is loaded onto the element, and changes in the oscillation frequency sensitively translate into small changes of the catalyst mass. This unique feature provides real-time changes in the mass of the catalyst during adsorption and desorption of reactant/product molecules from which a host of insights into the physicochemical processes occurring in the catalyst pores may be obtained.

Equilibrium adsorption isotherms were obtained on these catalysts using n-butane, isobutane, and propane as proxy reactant molecules (T = 303-398 K, adsorbate partial pressure 0-1.2 bar) and 2,2,4-trimethylpentane (2,2,4-TMP) as proxy product molecule (T = 298-473 K, P224-TMP = 0-0.3 bar). Analysis of the transient adsorption/desorption profiles of the reactant molecules demonstrate that diffusion in the secondary meso-/macroporous structure formed in either the catalyst packing or the pelletized cataysts control the overall sorption rates. The experimental adsorption/desorption profiles from the pelletized zeolites were regressed with dynamic models to obtain effective meso-/macropore diffusivities for reactant molecules. Neither USY nor beta zeolites appear to be durable catalysts for alkylation. The alkylate product (C8) is retained in the pores, and even reactant molecules (C4's) are slow to desorb. Mesoporous silica gels provide good pore accessibility for C8 alkylates as evidenced by complete desorption of 224-TMP even at mild temperatures. These results suggest that the design of solid acid catalysts for n-butane + isobutane alkylation must focus on mesoporous structures for better pore accessibility and extended durability.



CEBC Calendar

September 13, Wednesday - Mandatory Lab Safety Meeting
All researchers at 1501 Wakarusa Dr. must attend

9:00 a.m. in Building B seminar room

September 19, Tuesday - CEBC Colloquium
Dr. David Sholl, Chair of Georgia Tech School of Chemical & Biomolecular Engineering
"New Nanoporous Materials for Practical Applications Using Computation Modeling - How Close Is the Dream to Reality?"

9:00 a.m. - 10:00 a.m., 1501 Wakarusa Drive, Building B seminar room
10:00 a.m. discussion with students

October 16 & 17, Monday & Tuesday - CEBC Fall Industry Advisory Board Meeting
Registration is Open - click here!

Monday 12:00-7:30 p.m. at the Adams Alumni Center, 1266 Oread Avenue, Lawrence
Tuesday 8:30-noon at the CEBC Complex, 1501 Wakarusa Drive, Lawrence

November 7, Tuesday - CEBC Industry Colloquium
Dr. Brandon Emme, Cellulose Team Leader, ICM, Inc.
"Title TBA"

9:00 a.m. - 10:00 a.m., 1501 Wakarusa Drive, Building B seminar room
10:00 a.m. discussion with students

KU Today
48 nationally ranked graduate programs.
—U.S. News & World Report
Pharmacy school No. 2 nationally for NIH funding