|
|
| Line 1: |
Line 1: |
| {{Orphan|date=February 2009}}
| | Alyson is the title people use to contact me and I think it seems fairly good when you say it. To play lacross is the thing I adore most of all. Office supervising is where her main income arrives from. For years he's been living in Alaska and he doesn't plan on changing it.<br><br>Look at my homepage: psychic phone, [http://203.250.78.160/zbxe/?document_srl=1792908 visit here], |
| The '''Weisz-Prater Criterion''' is a method used to estimate the influence of pore diffusion on reaction rates in heterogeneous catalytic reactions.<ref>{{Cite journal|last1=Weisz|first1=P. B.|last2=Prater|first2=C. D.|title=Interpretation of Measurements in Experimental Catalysis|journal=Advances in Catalysis|volume=6|date=1954|pages=143|doi=10.1016/S0360-0564(08)60390-9|postscript=<!--None-->|series=Advances in Catalysis|isbn=978-0-12-007806-6}}</ref> If the criterion is satisfied, pore diffusion limitations are negligible. The criterion is <br />
| |
| <math>N_{W-P} = \dfrac{\mathfrak{R} R^2_p}{C_s D_{eff}} \le 3\beta</math><br />
| |
| Where <math>\mathfrak{R}</math> is the [[reaction rate]] per volume of catalyst, <math>R_p</math> is the catalyst particle radius, <math>C_s</math> is the reactant concentration at the particle surface, and <math>D_{eff}</math> is the effective [[mass diffusivity|diffusivity]]. Diffusion is usually in the [[Knudsen number|Knudsen]] regime when average pore radius is less than 100 nm.<br />
| |
| For a given effectiveness factor,<math>\eta</math>, and [[reaction order]], n, the quantity <math>\beta</math> is defined by the equation:<br /> | |
| <math>\eta = \dfrac{3}{R^3_p} \int_{0}^{R_p} [1-\beta (1-r/R_p)^n] r^2\ dr</math><br />
| |
| for small values of beta this can be approximated using the [[binomial theorem]]:<br />
| |
| <math>\eta = 1-\dfrac{n \beta}{4}</math><br />
| |
| Assuming <math>\eta \ge 0.95</math> with a 1st or zero order reaction gives values of <math>\beta</math>, 0.6 and 6 respectively. Therefore for many conditions, if <math>N_{W-P} \le 0.3</math> then pore diffusion limitations can be excluded.<ref>{{cite book|last=Vannice|first=M. Albert| title=Kinetics of Catalytic Reactions|publisher=Springer Science+Business Media|place=New York|year=2005|pages=63–65}}</ref>
| |
| | |
| | |
| == References ==
| |
| <references />
| |
| [[Category:Scientific techniques]]
| |
| [[Category:Laboratory techniques]]
| |
| [[Category:Transport phenomena]]
| |
| [[Category:Chemical engineering]]
| |
Revision as of 12:16, 4 March 2014
Alyson is the title people use to contact me and I think it seems fairly good when you say it. To play lacross is the thing I adore most of all. Office supervising is where her main income arrives from. For years he's been living in Alaska and he doesn't plan on changing it.
Look at my homepage: psychic phone, visit here,