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Sorption kinetics of linear paraffins in zeolite BEA nanocrystals
Microporous and Mesoporous Materials 124 (2009) 236–237
Contents lists available at ScienceDirect
Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso
Correspondence
Sorption kinetics of linear paraffins in zeolite BEA nanocrystals Patrícia M. Lima a, Caroline V. Gonçalves b, Célio L. Cavalcante Jr. b, Dilson Cardoso a,* a b
Catalysis Laboratory – LabCat, Federal University of São Carlos, P.O. Box 676, 13565-905 São Carlos-SP, Brazil Chemical Engineering Department, Federal University of Ceará, 60455-760 Fortaleza-CE, Brazil
a r t i c l e
i n f o
a b s t r a c t
Article history: Received 31 March 2009 Received in revised form 15 April 2009 Accepted 17 April 2009 Available online 29 May 2009
It has come to our attention that one of the aspects of our paper recently published [P.M. Lima, C.V. Goncalves, C.L. Cavalcante Jr., D. Cardoso, Micropor. Mesopor. Mater. 116 (2008) 352] had an inaccuracy: Eq. (9) missed a temperature term in the denominator of the right-hand side of the equation. With this observation it may be disregard the importance of heat effects in our calculations and may consider that our desorption experiments were performed essentially in isothermal conditions. Ó 2009 Elsevier Inc. All rights reserved.
Keywords: Desorption Zero length column Alkanes Beta zeolite
Dear Editor, It has come to our attention that one of the aspects of our paper recently published [1] had an inaccuracy: Eq. (9) missed the temperature in the denominator of the first term in the right-hand side of the equation. So the correct equation should be, as reported in Brandani et al. [2]:
ðad=cÞ ¼
2 DH C 0 FR RT haV s
ð1Þ
where R is the gas constant and a is the external area/volume for adsorbent particle (=3/Rp).
After realizing that mistake, the calculations that are presented in Table 4 of the original paper were checked and the correct new values are presented below (Table 1). As in the original paper, the values for the parameter (ad/c) were determined considering the radius of the small crystallites (7 nm) and the aggregates of particles (2500 nm). It may be observed now that the values obtained for the parameter (ad/c) are indeed very low with either particle radius we use, in contrary to what was reported previously in our paper [1]. With this observation we may disregard the importance of heat effects in our model and may consider that our experiments were performed essentially in isothermal conditions. Thus the very low val-
Table 1 Significance of heat effects in diffusion measurement of liner paraffins from zeolite beta (revision of Table 4 of Lima et al. [1]).
n-C7
Rp (nm)
T (K)
F (mL/min)
C0 (gmol/cm3)
(DH/RT)
ha (cal/min cm2 K) (1/cm)
C 0 FR haV s
ad/c
2500
393 473 393 473
20 20 20 20
5.35 107 5.35 107 5.35 107 5.35 107
19.209 15.960 19.209 15.960
2.14 105 2.14 105 2.73 1010 2.73 1010
1.78 107 1.78 107 1.40 1012 1.40 1012
6.59 105 4.55 105 5.16 1010 3.56 1010
423 473 423 473
20 20 20 20
8.23 109 8.23 109 8.23 109 8.23 109
23.795 21.280 23.795 21.280
2.14 105 2.14 105 2.73 1010 2.73 1010
2.75 109 2.75 109 2.15 1014 2.15 1014
1.55 106 1.24 106 1.22 1011 9.75 1012
7 n-C10
2500 7
Note: ha = 3k/Rp, where k is the thermal conductivity of the carrier gas and Rp is the radius of the particle.
* Corresponding author. Tel.: +55 16 3351 8693; fax: +55 16 3351 8269. E-mail address: [email protected] (D. Cardoso). 1387-1811/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2009.04.024
P.M. Lima et al. / Microporous and Mesoporous Materials 124 (2009) 236–237
ues obtained for the diffusivities of n-C7 and n-C10 in our experiments using zeolite beta, when compared to zeolites with similar pore aperture (e.g., FAU), can be attributed to extracrystalline mass transfer resistances (bed diffusion), not to non-isothermal effects. We apologize for the inaccuracy presented in our original paper [1] and hope this letter can be published for the sake of correction of our data and their interpretation.
237
References [1] P.M. Lima, C.V. Goncalves, C.L. Cavalcante Jr., D. Cardoso, Micropor. Mesopor. Mater. 116 (2008) 352. [2] S. Brandani, C.L. Cavalcante Jr., A. Guimarães, D.M. Ruthven, Adsorption 4 (1998) 275.
Contents lists available at ScienceDirect
Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso
Correspondence
Sorption kinetics of linear paraffins in zeolite BEA nanocrystals Patrícia M. Lima a, Caroline V. Gonçalves b, Célio L. Cavalcante Jr. b, Dilson Cardoso a,* a b
Catalysis Laboratory – LabCat, Federal University of São Carlos, P.O. Box 676, 13565-905 São Carlos-SP, Brazil Chemical Engineering Department, Federal University of Ceará, 60455-760 Fortaleza-CE, Brazil
a r t i c l e
i n f o
a b s t r a c t
Article history: Received 31 March 2009 Received in revised form 15 April 2009 Accepted 17 April 2009 Available online 29 May 2009
It has come to our attention that one of the aspects of our paper recently published [P.M. Lima, C.V. Goncalves, C.L. Cavalcante Jr., D. Cardoso, Micropor. Mesopor. Mater. 116 (2008) 352] had an inaccuracy: Eq. (9) missed a temperature term in the denominator of the right-hand side of the equation. With this observation it may be disregard the importance of heat effects in our calculations and may consider that our desorption experiments were performed essentially in isothermal conditions. Ó 2009 Elsevier Inc. All rights reserved.
Keywords: Desorption Zero length column Alkanes Beta zeolite
Dear Editor, It has come to our attention that one of the aspects of our paper recently published [1] had an inaccuracy: Eq. (9) missed the temperature in the denominator of the first term in the right-hand side of the equation. So the correct equation should be, as reported in Brandani et al. [2]:
ðad=cÞ ¼
2 DH C 0 FR RT haV s
ð1Þ
where R is the gas constant and a is the external area/volume for adsorbent particle (=3/Rp).
After realizing that mistake, the calculations that are presented in Table 4 of the original paper were checked and the correct new values are presented below (Table 1). As in the original paper, the values for the parameter (ad/c) were determined considering the radius of the small crystallites (7 nm) and the aggregates of particles (2500 nm). It may be observed now that the values obtained for the parameter (ad/c) are indeed very low with either particle radius we use, in contrary to what was reported previously in our paper [1]. With this observation we may disregard the importance of heat effects in our model and may consider that our experiments were performed essentially in isothermal conditions. Thus the very low val-
Table 1 Significance of heat effects in diffusion measurement of liner paraffins from zeolite beta (revision of Table 4 of Lima et al. [1]).
n-C7
Rp (nm)
T (K)
F (mL/min)
C0 (gmol/cm3)
(DH/RT)
ha (cal/min cm2 K) (1/cm)
C 0 FR haV s
ad/c
2500
393 473 393 473
20 20 20 20
5.35 107 5.35 107 5.35 107 5.35 107
19.209 15.960 19.209 15.960
2.14 105 2.14 105 2.73 1010 2.73 1010
1.78 107 1.78 107 1.40 1012 1.40 1012
6.59 105 4.55 105 5.16 1010 3.56 1010
423 473 423 473
20 20 20 20
8.23 109 8.23 109 8.23 109 8.23 109
23.795 21.280 23.795 21.280
2.14 105 2.14 105 2.73 1010 2.73 1010
2.75 109 2.75 109 2.15 1014 2.15 1014
1.55 106 1.24 106 1.22 1011 9.75 1012
7 n-C10
2500 7
Note: ha = 3k/Rp, where k is the thermal conductivity of the carrier gas and Rp is the radius of the particle.
* Corresponding author. Tel.: +55 16 3351 8693; fax: +55 16 3351 8269. E-mail address: [email protected] (D. Cardoso). 1387-1811/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2009.04.024
P.M. Lima et al. / Microporous and Mesoporous Materials 124 (2009) 236–237
ues obtained for the diffusivities of n-C7 and n-C10 in our experiments using zeolite beta, when compared to zeolites with similar pore aperture (e.g., FAU), can be attributed to extracrystalline mass transfer resistances (bed diffusion), not to non-isothermal effects. We apologize for the inaccuracy presented in our original paper [1] and hope this letter can be published for the sake of correction of our data and their interpretation.
237
References [1] P.M. Lima, C.V. Goncalves, C.L. Cavalcante Jr., D. Cardoso, Micropor. Mesopor. Mater. 116 (2008) 352. [2] S. Brandani, C.L. Cavalcante Jr., A. Guimarães, D.M. Ruthven, Adsorption 4 (1998) 275.