| Pulse n |
area
n |
Δarea
n |
V
adsorbed (cm
3 /g STP) |
Cumulative quantity (cm
3 /g STP) |
| 1 |
0 |
0.0105809790 |
0.2800256 |
0.2800256 |
| 2 |
0.000471772 |
0.0105338018 |
0.2787771 |
0.5588027 |
| 3 |
0.00247767 |
0.0081033090 |
0.2144541 |
0.7732567 |
| 4 |
0.009846683 |
0.0007342960 |
0.0194331 |
0.7926899 |
| 5 |
0.010348201 |
0.0002327780 |
0.0061605 |
0.7988504 |
| 6 |
0.010030243 |
0.0005507360 |
0.0145752 |
0.8134256 |
| 7 |
0.009967717 |
0.0006132620 |
0.0162300 |
0.8296556 |
| 8 |
0.010580979 |
0 |
0.0000000 |
0.8296556 |
Includes the volume adsorbed per pulse and the cumulative volume adsorbed.
Gram molecular weight
Gram molecular weight is the weighted average of the number of moles of each active metal in the catalyst. Since this is a monometallic catalyst, the gram molecular weight is equal to the molecular weight of palladium (106.42 [g/mol]). The GMC
Calc is calculated using
[link] , where F is the fraction of sample weight for metal N and W
atomicN is the gram molecular weight of metal N (g/g-mole).
[link] shows the calculation for this experiment.
The metal dispersion is calculated using
[link] , where PD is the percent metal dispersion, V
s is the volume adsorbed (cm
3 at STP), SF
Calc is the calculated stoichiometry factor (equal to 2 for a palladium-hydrogen system), SW is the sample weight and GMW
Calc is the calculated gram molecular weight of the sample [g/g-mole]. Therefore, in
[link] we obtain a metal dispersion of 6.03%.
The metallic surface area per gram of metal is calculated using
[link] , where SA
Metallic is the metallic surface area (m
2 /g of metal), SW
Metal is the active metal weight, SF
Calc is the calculated stoichiometric factor and SA
Pd is the cross sectional area of one palladium atom (nm
2 ). Thus, in
[link] we obtain a metallic surface area of 2420.99 m
2 /g-metal.
Active particle size
The active particle size is estimated using
[link] , where D
Calc is palladium metal density (g/cm
3 ), SW
Metal is the active metal weight, GMW
Calc is the calculated gram molecular weight (g/g-mole), and SA
Pd is the cross sectional area of one palladium atom (nm
2 ). As seen in
[link] we obtain an optical particle size of 2.88 nm.
In a commercial instrument, a summary report will be provided which summarizes the properties of our catalytic material. All the equations used during this example were extracted from the AutoChem 2920-User's Manual.
| Properties |
Value |
| Palladium atomic weight |
106.4 g/mol |
| Atomic cross-sectional area |
0.0787 nm² |
| Metal density |
12.02 g/cm³ |
| Palladium loading |
1 wt% |
| Metal dispersion |
6.03% |
| Metallic surface area |
2420.99 m²/g-metal |
| Active particle diameter (hemisphere) |
2.88 nm |
Summary report provided by Micromeritics AuthoChem 2920.
References
- A. J. Canty,
Accounts Chem. Res. , 1992,
25 , 83.
- H. S. Fogler,
Elements of Chemical Reaction Engineering , Prentice-Hall, New York (1992).
- Micromeritics Instrument Corporation,
AutoChem 2920 – Automated catalyst characterization system – Operators Manual , V4.01 (2009).
- M. O. Nutt, K. N. Heck, P. Alvarez, and M. S. Wong,
Appl. Catal. B-Environ. , 2006,
69 , 115.
- M. O. Nutt, J. B. Hughes, and M. S. Wong,
Environ. Sci. Technol. , 2005,
39 , 1346.
- P. A. Webb and C. Orr,
Analytical Methods in Fine Particle Technology , Micromeritics Instrument Corp, 1997.
- R. Zhang, J. A. Schwarz, A. Datye, and J. P. Baltrus,
J. Catal. , 1992,
138 , 55.
