338
A. Shekari, G.S. Patience / Catalysis Today 157 (2010) 334–338
containing 1.4 vol% n-butane in air. The effect of catalyst oxidation
on maleic anhydride production becomes more important when
operating under fuel rich conditions. Under such conditions, an
improvement of the order of 3.5 times in maleic anhydride pro-
duction rate could be expected by extending the catalyst oxidation
time to 10 min. A near equimolar feed of 6% n-butane and oxygen
resulted in the highest maleic anhydride production rate. The tran-
sient maleic anhydride rate data showed that to prevent the catalyst
deactivation and to maintain a high production rate at fuel rich con-
ditions, the feed to the reactor must have an appreciable amount of
oxygen. These data also suggested that efficient catalyst regenera-
tion would still be required to compensate for catalyst deactivation
even at the presence of relatively large amounts of oxygen in the
reduction feed.
Acknowledgements
Fig. 6. VPO catalyst deactivation during redox operations at fuel rich conditions
(feed flow rate: 40 mL/min (STP), temperature: 380 ◦C, oxidation time: 10 min, O2/n-
butane: 0.0).
We would like to thank the Natural Sciences and Engineering
Research Council of Canada (NSERC), Ministre du Développement
Economique, de l’Innovation et de l’Exportation (MDEIE) of Quebec
and Canadian Foundation for Innovation (CFI) for their financial
support of this project. We wish to thank also the DuPont Company
for providing the catalyst samples for this research.
3.2.1. Catalyst deactivation
During the transient redox experiments, we observed that at
relatively high n-butane concentrations in the feed (O2/n-butane
≤0.3), the catalyst undergoes a considerable deactivation dur-
pre-treatment before each reduction cycle (10 min). The catalyst
deactivation was characterized by a stepwise decrease in the maleic
anhydride transient rates during 5–8 consecutive redox cycles
under the same operating conditions. Fig. 6 demonstrates the tran-
sient maleic anhydride rates selected from eight consecutive redox
cycles at the conditions where there was no oxygen in the reduc-
tion feed. A significant decrease in the maleic anhydride transient
rate could be observed by exposing the catalyst to these consecutive
redox cycles. These data show that the deactivation of catalyst could
not be compensated even by 10 min of catalyst oxidation before
each reduction cycle.
When the catalyst oxidation time is relatively short, even in
the presence of some oxygen in the reduction feed (O2/n-butane
≤0.6), the catalyst still suffers a slight deactivation during consecu-
tive redox cycles. Generally, this effect is more noticeable when the
oxygen to n-butane molar ratio in the feed falls below 0.3. Under
these conditions, the catalyst deactivation occurs irrespective of the
duration of oxidation period prior to each reduction cycle (Fig. 6).
These results suggest that to maintain a relatively high production
rate at fuel rich conditions, the feed to the reactor must have an
appreciable amount of oxygen to prevent catalyst over reduction.
Also, even in the presence of oxygen in the reduction feed, efficient
catalyst oxidation would still be required to compensate for the
catalyst deactivation during reduction under fuel rich conditions.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
References
[1] N. Ballarini, F. Cavani, C. Cortelli, S. Ligi, F. Pierelli, F. Trifiro, C. Fumagalli, G.
Mazzoni, T. Monti, Top. Catal. 38 (2006) 147–156.
[2] R.M. Contractor, Chem. Eng. Sci. 54 (1999) 5627–5632.
[3] Y. Schuurman, J.T. Gleaves, Catal. Today 33 (1997) 25–37.
[4] G.S. Patience, M.J. Lorences, Int. J. Chem. Reactor Eng. 4 (2006) 1–18.
[5] Y.H. Taufiq-Yap, B.H. Sakakini, K.C. Waugh, Catal. Lett. 48 (1997) 105.
[6] B.H. Sakakini, Y.H. Taugiq-Yap, K.C. Waugh, J. Catal. 189 (2000) 253.
[7] S.K. Bej, M.S. Rao, Ind. Eng. Chem. Res. 30 (1991) 1819.
[8] U. Rodemerck, B. Kubias, H.-W. Zanthoff, M. Baerns, Appl. Catal. A: Gen. 153
(1997) 203.
[9] D. Creaser, B. Andersson, R.R. Hudgins, P.L. Silveston, J. Catal. 182 (1999)
264–269.
[10] D.X. Wang, M.A. Barteau, Catal. Lett. 90 (2003) 7–11.
[11] J. Gascón, R. Valenciano, C. Téllez, J. Herguido, M. Menéndez, Chem. Eng. Sci. 61
(2006) 6385–6394.
[12] G. Centi, F. Trifiro, J.R. Ebner, V.M. Franchetti, Chem. Rev. 88 (1988) 55.
[13] G. Emig, K. Uihlein, C.-J. Hacker, in: V.C. Corberan, S.V. Bellon (Eds.), New Devel-
opments in Selective Oxidation, Elsevier, Amsterdam, 1994, pp. 243–251.
[14] M.J. Lorences, G.S. Patience, F.V. Diez, J. Coca, Appl. Catal. A: Gen. 263 (2004)
193–202.
[15] X.-F. Huang, C.-Y. Li, B.-H. Chen, P.L. Silveston, AIChE J. 48 (2002) 846–855.
[16] G.S. Patience, R.E. Bockrath, J.D. Sullivan, H.S. Horowitz, Ind. Eng. Chem. Res. 46
(2007) 4374–4381.
[17] G.S. Patience, R.E. Bockrath, Appl. Catal. A: Gen 376 (2010) 4–12.
[18] E. Johansson, A. Lyngfelt, T. Mattisson, F. Johnsson, Powder Technol. 134 (2003)
210–217.
4. Conclusions
[19] M. Ryden, A. Lyngfelt, T. Mattisson, Fuel 85 (2006) 1631–1641.
[20] J.L. Dubois, D. Garrait, A. Legall, G. Bazin, S. Serreau, J. Dubois, Arkema France,
WO 2006/072682 A1, 2006.
[21] B. Turk, J. Schlather, Gasification Technologies Conference, 2006.
[22] L.W. Miller, UOP LLC, U.S. Patent 6,166,282 (2000).
[23] F.J. Keil, Micropor. Mesopor. Mater. 29 (1999) 49–66.
Maleic anhydride production rate is sensitive to catalyst oxi-
dation time and reduction feed composition. Irrespective of the
reduction feed composition, the average maleic anhydride produc-
tion rate in a redox cycle could be increased by up to almost 50%
by extending the catalyst oxidation time from 0.3 to 10 min. Maleic
anhydride production rates increase even with a feed composition