We have developed Zeolite 4A- confirmed from XRD analysis. Now i need to evaluate other properties viz., surface area, pore size, pore volume, CEC, water adsorption capacity etc. The available literature shows various process and it is confusing me- so i am looking for one universally accepted method.
Second thing, surface area analysis with N2 shows negative slope. it implies that the standard process i followed is not suitable (degasing at 150 oc for 3h and run the analysis with liquid N2 at -177 oC). Kindly suggest if there is any other way of preheating the sample.
reference of literature and/or book is also welcome.
If you are trying to distinguish micropore contribution to the sorption isotherm from mesopores | outer surface etc, the standard method is the t-plot.
Hi there,
You can use DFT to determine the pore volume as well, say, micropore, mesopore, and macropore. It can be calculated from the area undercurve of pore size distribution.
Regards.
if you have a DFT kernel for zeolites then yes, DFT is a good option. Note that DFT is insensitive to macropores, and zeolite pores are of a very specific shape, while DFT adopts a common (cylindrical) shape. So perhaps first distinguish between real zeolite contribution (micropores) from the rest (which often present in practice when zeolites are synthesized) using alpha-s ot t- method. Then you have the zeolite contribution alone, and because it's not a new one, it has been characterizaed already in the literature
Dear Dr. Aleksey M Vishnyakov Sir,
Thank you very much for your such insightful answer. Actually, the synthesized zeolite is mostly micro porous in nature (below 2.5 nm) so we avoid DFT model and tried BJH model for pore size and pore volume analysis. One request can you suggest some literate for using T method appropriately ?
Mostofa, BJH is fundamentally flawed and does not work on anything narrower than 20nm. Already for MCM-41 is gives ridiculous results (see Ravikovitch and Neimark first papers on MCM-41 characterization, about 20 years ago. http://sol.rutgers.edu/~aneimark/ and go to "papers", u will find it.
DFT kernel for cylindrical silica-type pores is not the best answer but at least relevant, while BJH is not (btw BET is a theory of multilayer sorption on flat nonporous surface and therefore not applicable to micropore structure of zeolites).
as far as I remember, Geg & Sing book has a good description of comparative plot methods (t- and alpha-s). or look here for examples
http://adsorption.org/awm/ads/meso/plots/MCM-16.htm#alfa-s
what equipment r u using and what kernels r available?
Dear Dr. Aleksey M Vishnyakov Sir,
We are using Quantchrome NOVA 4000e model and almost very Kernel is available. I am not sure which kernel is best to understand the Zeolite surface area, pore size and pore volume distribution so i put the question.
Sir, my heartiest thank you for suggesting documents and correcting me from error.
there must be a micropore+mesopore kernel there. Peter Ravikovitch calculated so many of them for Quantachrome in 2000-2005. As a first guess, take cylindrical silica pores kernel. My guess you will see 2 peaks (micropores you target and mesoporosity that often forms in zeolite synthesis
Thanks sir for your suggestion. I will check and after analyzing will let you know my findings. i will message you personally, if you are comfortable.
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