Hello,

In a gas-ideal approximation (which is good for lower temperatures), it is possible to convert mmol per g into cm3 per g. The procedure is as follow:

*Use the molar volume of the gas: Nitrogen have a value of 22.40 L/mol, so, multiplying the value that you have per 22.40 L/mol, you will obtain the conversion into cm3/g.

V(cm3/g)= (x)*(22.40 L/mol), where x is the value in mmol/g. Directly you will obtain the value in cm3 per gram of catalyst or adsorbent.

PRACTICE EXERCISE: Supposing that you have a value of 2.50 mmol/g, convert it into cm3/g.

-SOLUTION: Applying the previous equation:

V(cm3/g)=(2.50)*(22.40)= 56 cm3/g

-ANSWER: The value of 2.50 mmol/gcatalyst (adsorbent) will correspond to 56 cm3/gcatalyst (adsorbent).

SOME ADDITIONAL CONSIDERATIONS:

*Other people use the ideal gas-equation PV=nRT ---> V=nRT/P, but the results are quite different.

*As 22.40 L/mol is the molar volume of the gas at standard conditions (0K and 273.15 K), it would be necessary to obtain/determine the value of the volume molar of nitrogen at the experimental conditions (77 K).

If you have a doubt, please contact me.

with kind regards,

Julián Sánchez (Ed Schz Velandia-Patinök)

Julián E. Sánchez-Velandia Thank you very much for your response. I have got it. You explained it very well..

This paper can help you

Abdelkader Dehbi Thank you.

Can anyone help me with the conversion of adsorption capacity unit for Nitrogen at 77K from mmol/g to cm3/g?

Very simple way for this conversion is ,,,,,,,,,,,,,,,,

*1 mole of nitrogen gas=22400 ml or 22400 ml/mole

*The value obtained from BET instrument= X mmol/g

*convert this X mmol/g to mol/g or divide X mmol by 1000

you will get X mol/g

* 1 mole N2 = 22400 ml (22400*X/1= your answer)

X mole = X ml

this gives you the final volume adsorbed per g of the sample

I hope it is clear

Kempanna Kanakikodi Thank you for your response.

In some software, at least Micromeritics, You can choose the unit for the gas. mmol/g or cm3/g. In the Micromeritics software it is under Units.

Julián E. Sánchez-Velandia

Hello

I think it should be divided by 22.40 not multiplied.

V(cm3/g)=(2.50) / (22.40)= 0.112 cm3/g

Majida Khazaal I hope that you are fine.

No, you must Multiplied instead of divided it. As demonstration I am attaching a file with the verification of units. Maybe you are confusing with the molar volume which have L/mol units instead of mol/L units.

With kind regards,

Julián.

Julián E. Sánchez-Velandia Thank you for your explanation, but what I meant was that 1 mol of gas at STP occupies 22.4 L, Then 1 mmol occupies 22.4 mL.

With best wishes,

Majida

But it is still not a division. It is good to check the units. If You put in mmol/g and l/mol You get the right units as explained above.

May anyone help me with the conversion of the adsorption capacity unit for Carbon dioxide at 298.150 K from cm3/g STP to mmol/g? Thank You.

Multiply your value by 22.414 to have value in cm^3/g

Thank you