|
|
| (One intermediate revision by one other user not shown) |
| Line 1: |
Line 1: |
| {{Orphan|date=February 2009}}
| | Andrew Berryhill is what his spouse loves to call him and he completely digs that name. Some time ago he selected to reside in North Carolina and he doesn't plan on altering it. Distributing production is how he tends to make a residing. To perform domino is something I truly appreciate doing.<br><br>Here is my web site real psychics ([http://www.chk.woobi.co.kr/xe/?document_srl=346069 mouse click the up coming post]) |
| 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]]
| |
Andrew Berryhill is what his spouse loves to call him and he completely digs that name. Some time ago he selected to reside in North Carolina and he doesn't plan on altering it. Distributing production is how he tends to make a residing. To perform domino is something I truly appreciate doing.
Here is my web site real psychics (mouse click the up coming post)