Abstract/Details

Microwaves and sorption on oxides: Surface temperature and adsorption selectivity investigation


2008 2008

Other formats: Order a copy

Abstract (summary)

Microwave heating is not the same as conventional heating, and it is believed that this difference, the "microwave effect," may be interpreted to be due to selective local heating. The temperature at the surface where sorption occurs is "effectively" greater than the measured solid or gas temperature. In these studies, measurements of the amount adsorbed as functions of the partial pressure of a specific adsorbate in the presence of microwave irradiation were related to conventional adsorption isotherms. Equating the adsorbate pressure required to achieve a specific coverage (an isostere) in the presence of microwave irradiation to the amount adsorbed for a conventional isotherm allowed for an estimate of the "effective" surface temperature in the presence of microwaves. It was found that the effective surface temperature increased when using adsorbates having a significantly higher permittivity or when increasing the microwave power. The implication of this change in the surface energy for specific species in the presence of microwaves is discussed.

It was hypothesized that the adsorption selectivity in the presence of microwaves is primarily dependent on the permittivity of the adsorbates, while selectivity is dependent on the heat of adsorption under conventional heating. Sorption experiments were carried out using a flow based dual-component adsorption system measuring changes in the amount adsorbed with conventional heating and using microwave heating at 2.45 and 5.8 GHz. The adsorption selectivity as a function of microwave frequency was examined for a case in which the adsorbates have an opposite dependence of permittivity with frequency (isopropanol had a greater permittivity than acetone at 2.45 GHz, and acetone had a greater permittivity than isopropanol at 5.8 GHz). It was found that microwave energy could influence sorption differently than conventional heating. Differences in the adsorption selectivity were not as great as expected based on the bulk liquid permittivities due to the miscibility of the components. The permittivities of the adsorbates in the adsorbed phase at low surface coverage may be different than that of their respective bulk liquids. The smaller than expected change in adsorption selectivity with microwave frequency might also be attributed to the miscibility of acetone and isopropanol.

Indexing (details)


Subject
Chemical engineering
Classification
0542: Chemical engineering
Identifier / keyword
Applied sciences, Adsorption, Dielectrics, Heating, Isotherms, Microwaves, Permittivity
Title
Microwaves and sorption on oxides: Surface temperature and adsorption selectivity investigation
Author
Vallee, Steven James
Number of pages
164
Publication year
2008
Degree date
2008
School code
0118
Source
DAI-B 69/08, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780549663577
Advisor
Conner, William Curtis, Jr.
Committee member
Auerbach, Scott M.; Yngvesson, K. S.
University/institution
University of Massachusetts Amherst
Department
Chemical Engineering
University location
United States -- Massachusetts
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3315479
ProQuest document ID
219914581
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/219914581
Access the complete full text

You can get the full text of this document if it is part of your institution's ProQuest subscription.

Try one of the following:

  • Connect to ProQuest through your library network and search for the document from there.
  • Request the document from your library.
  • Go to the ProQuest login page and enter a ProQuest or My Research username / password.