what is the procedure to estimate the active surface area of liquid catalysts?
Dear Shubhangi,
Did you try methylene blue spot test? I don't know if it works for liquid catalysts but you can give it a try. However, the reference values may hurt you as the test was developed for colloidal suspensions (usually clays).
I am equally interested in this. I will definitely ask my colleagues over here and if I get something useful, I will update you.
MB adsorption is widely used to measure specific surface area of catalysts in the colloidal dispersions
Generally one of the reactants will bond weakly to the catalyst but more strongly than the intended product does.
To test for active surface decide which pure reactant bonds to the catalyst and add a dilute concentration of that component to the dispersion. Micro filter a sample after a period of time allowed to equilibrate and analyze the pure component remaining in the liquid. Active surface implies the dispersion can be filtered.
Repeat several times at gradually increasing concentrations of the pure component. Graph the results of adsorbed reactant compared to reactant remaining in solution as a straight line that can be extrapolated back to zero concentration. The slope and intercept determine the active surface before reactant is added.
When your straight line becomes a curve or different slope at some higher concentration of reactant, it means more than one molecule of reactant is competing for each active site. The test can be stopped.
Thanks to all, I would like to ask Dr. Decker, whether your method is applicable to the colloid suspension where the particle size is hardly 4-15 nm.
please reply.
For such a small size centrifugal separation might be more appropriate. If you can get a clear liquid layer by filtering or centrifugation the method can be used. Centrifuge to excess has risk of removing adsorbed pure component from catalyst.
Nano filtration can go as low as 150 molecular weight. Ultra filtration can go to about 3000 molecular weight. Microfiltration is limited at about 50,000 molecular weight.
If the pure component is a much smaller molecule than the effective catalyst size, then filtration is preferred and only a small amount of clear liquid is needed.
If catalyst and pure component are about the same size but different densities, mild centrifugation might be possible.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders