They are totally different:

BET is a method for estimating surface area of a non-porous solid based on multilayer adsorption.

BJH is a method to determine pore size distribution of a mesoporous solid based on the Kelvin equation.

Thank you. Do you know about an article that describes each method? Since now, I acknowledge you.

Both BET and BJH are abbreviations of scientists´ names who developed the theories for different calculations. For doing these calculations, an isotherm with enough datapoint is necessary.

BET calculation is used for determining the surface area of a micro-/ meso-/macroporous material.

BJH calculation is used for plotting a pore size distribution graph.

For articles, you can check their original paper published many years ago by Brunauer, Emmett, Teller for BET and Barrett-Joyner-Halenda for BJH

or;

The IUPAC technical report entitled: "Recommendations for the characterization of porous solids (Technical Report)" written in 1994.

BET calculation, strictly speaking, should not be used for determining the surface area of a micro-/ meso-/macroporous material, since it will lead to surface areas larger than real. This occurs due to enhanced interactions of the gas inside the pores.

If you have no option but to use BET, then you should check that it obeys some rules established by Rouquerol (ahhh... where is the original paper??? but should be in his last book ISBN: 0080970362).

BET method is precise for a non-porous material only, since derivation of the main equation does not take into account enhanced potential by pores. 

In any case, both original articles (BET and BJH) are attached.

Thank you for the comments!

Thank alot

Thank you sir for the providing good data...

thank you all.

THANKS  Fernando  FOR YOUR HELP  

any one help me for reaching an article about heterogenous catalysis to understand kinetic parameters and kinetic models and the effect of perovskites in isotopic exchange surfaces>??

Guys, that's an old report. You can refer to the newest one I'm attaching.

Regards!

It is better to look into Non-Local Density Function Theory, instead of outdated models such as BJH, SK and HK.

IUPAC recommends it now also, see the paper posted by Jorge in the above post.

thank you

Thank you for the explanations and the pdf files provided

HI,VERY GOOD INFORMATION

Hey guys, this is not an answer. In fact is a question. Suppose they have a hierarchical structured solid which has perfectly cylindrical macropores of variable length (in the order several mm) and 10 to 15 micron of diameter. They are fully open and have a lot of connection between them forming 90º angles these connection are regular separated by micron distances and the ensamble form three dimensional network. Simultaneously there is in the space between them, another class of pores that look like non regular slits. This is a consequence of two of the three dimensions of the slits are very big; in fact they are a kind of a wavy like continuous plates where the wide between the walls of the slit can vary continuously (between 500 to100 nanometers). Additionally the solid is inert, electrical conductor material and perfectly crystalline and its entire surface is constituted by the same crystallographic family. What technique/s you choice would be suitable to study this solid?

Hi Alicia,

If its a question, and not an answer, you should create a new question, instead of adding it as an answer.

By doing that you will make sure to get the attention that your question needs from the people following the topics that your question mentions.

Querido Fernando ¿Hablas español?

And yes, of course, I did what you said

BET theory measures the specific surface area of materials while BJH theory is a pore size distribution determination method.

Thanks Elida

For complete the most popular answer in this question, is important considerate that B.E.T method has weaknes on theoretical aspects, but is recognized and widely accepted for non porous, macro and mesoporous materials.

I leave this articles, if someone requier information

Article Surface Area and Pore Texture of Catalysts

https://www.degruyter.com/view/j/ci.2016.38.issue-1/ci-2016-0119/ci-2016-0119.xml

I agree with Alicia and Elida.

Thanks

Very helpful information! Thank you all!

Very useful information. Thanks

hi guys, BET measures the specific surface area of materials, while BJH theory estimate the a pore size distribution.

Brunauer-Emmett-Teller (BET) Surface Area Analysis and Barrett-Joyner-Halenda (BJH) Pore Size and Volume Analysis

How to plot Barrett-Joyner-Halenda (BJH) pore size and pore volume distribution graph in OriginPro? https://youtu.be/O55Ut4eLo9M

Thanks all

BET analysis provides precise specific surface area evaluation of materials by nitrogen multilayer adsorption measured as a function of relative pressure using a fully automated analyzer. The technique encompasses external area and pore area evaluations to determine the total specific surface area in m2/g, yielding important information in studying the effects of surface porosity and particle size in many applications.

BJH analysis can also be employed to determine pore area and specific pore volume using adsorption and desorption techniques. This technique characterizes pore size distribution independent of external area due to particle size of the sample.

It's an old topic. However, BET is used for porous materials to determine the specific surface area, so I am astonished about some answers saying it - per se - would not be suitable. Check it out:

https://en.wikipedia.org/wiki/BET_theory

https://www.3p-instruments.com/measurement-methods/bet-surface-area/