Engenharia Mecânica
MANAGING CATALYST DEACTIVATION IN REACTIVE DISTILLATION COLUMNS
Filipe, R.M.a,b; Matos, H.A.b,c; Novais, A.Q.d
aISEL, Inst Super Engn Lisboa, Área Departamental de Engenharia Química, 1959-007
Lisboa, Portugal
bCentro de Processos Químicos, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
cDepartamento de Engenharia Química e Biológica, Instituto Superior Técnico, Av. Rovisco
Pais, 1049-001 Lisboa, Portugal
dUnidade de Modelação e Optimização de Sistemas e Energia, Laboratório Nacional de
Energia e Geologia, Est. do Paço do Lumiar, 1649-038 Lisboa, Portugal
Fonte: Book of Abstracts of the 11th International Chemical and Biological Engineering Conference, Pages 486-487, 2011
Conferência: 11th International Chemical and Biological Engineering Conference, Lisbon, Portugal, 5-7 September 2011
Tipo de Documento: Article
Resumo: Reactive distillation (RD) represents a major breakthrough in process intensification, combining reaction and separation into the same physical vessel, with economic and environmental gains [1] leading to systems with significantly greener engineering attributes [2].
In previous work, the authors’ developed a framework combining feasible regions and optimization techniques for the design and multi-objective optimization of complex RD columns (RDC) [3]. This led to the consideration of RDC with distributed feeds, involving the combination of superheated and subcooled feeds that provide a source or a sink of heat at specified trays of the columns, which favors reaction while reducing the total reactive holdup requirements. It was also found that higher conversions could be obtained with the same reactive holdup by using these feed qualities outside the traditional range, which led to the consideration of using this technique to overcome catalyst deactivation during column operation.
Catalyst deactivation represents both an operational and a design problem. The reaction conversion achieved at each tray is reduced, which may limit column performance and product specifications. However, if catalyst deactivation is addressed at the design stage, an early assessment is possible and an operational strategy set in place to deal with the catalyst life-cycle. Little attention has been paid to the catalyst deactivation in RDC by the research community. Wang et al. [4] addresses the control of RDC when the production rate changes or the catalyst deactivates and proposes a control scheme able to maintain high purity and high conversion under such conditions.
This work addresses the effects of catalyst deactivation and investigates methods to reduce their impact on the RDC performance. In previous work the use of variable feed quality and
reboil ratio were investigated, and their positive effect in dealing with catalyst deactivation assessed [5]. This analysis was further extended with the inclusion of two new designs and different strategies on column energy supply to tackle catalyst deactivation [6].
In this work a rigorous dynamic model developed in gPROMS and applied to an illustrative example, the olefin metathesis system, wherein 2-pentene reacts to form 2-butene and 3-hexene, is used to investigate how the feed quality and reboil ratio changes can maintain product purity while the catalyst deactivates. Besides identifying column behavior under situations of reduced reaction conversion, strategies to overcome catalyst deactivation are also addressed, namely through manipulation of the feed temperature and the reboil ratio. This procedure extends the operating time of the column without having to interrupt production and replace the catalyst load. The effectiveness of these actions is largely dependent on column design, but satisfactory results were obtained with the proposed strategies to handle situations where catalyst activity is decreased down to 50%, at the expense of increased energy consumption. The results clearly show that the manipulation of the feed quality can be successfully used, although at the expense of a higher increase in energy consumption when compared to the manipulation of the reboil ratio.
In practice, the adoption of these strategies should be preceded by a economic evaluation accounting for the incurred extra energy costs and the savings associated to the extended life- cycle of the catalyst and reduced number of column shut-down and start-up operations. The trade-off between the cost of increasing energy supply and replacing the catalyst is investigated aiming at the determination of the ideal time for column operation interruption and catalyst replacement. Several scenarios with different catalyst lifetime are used to assess how the total operating costs can be minimized, while maintaining the product specifications. [1] R. Taylor and R. Krishna, Modelling Reactive Distillation, Chemical Engineering Science 55 (2000) 5183-5229
[2] M.F. Malone, R.S. Huss, and M.F. Doherty, Green chemical engineering aspects of reactive distillation, Environmental Science & Technology 37 (2003) 5325-5329.
[3] R.M. Filipe, S. Turnberg, S. Hauan, H.A. Matos, and A.Q. Novais, Multiobjective Design of Reactive Distillation with Feasible Regions, Industrial & Engineering Chemistry Research 47 (2008) 7284-7293.
[4] S.J. Wang, D.S.H. Wong, and E.K. Lee, Control of a reactive distillation column in the kinetic regime for the synthesis of n-butyl acetate, Industrial & Engineering Chemistry Research 42 (2003) 5182-5194.
[5] R.M. Filipe, H.A. Matos, and A.Q. Novais, Catalyst deactivation in reactive distillation, Computer-Aided Chemical Engineering 27 (2009) 831-836.
[6] R.M. Filipe, H.A. Matos, and A.Q. Novais, A strategy to extend reactive distillation column performance under catalyst deactivation, ESCAPE 21 (2011) Porto Carras, Greece.
MgA1 HYDROTALCITES AS SOLID HETEROGENEOUS CATALYSTS FOR BIODIESEL PRODUCTION
Gomes, J.F.P.a,b; Puna, J.F.B.a; Gonçalves, L.M.a; Bordado, J.C.M.b
aISEL, Instituto Superior de Engenharia de Lisboa, Chemical Engineering Department, 1959-
007 Lisboa, Portugal
bIST - Instituto Superior Técnico/UTL, Institute of Biotechnology and Bioengineering, 1049-
Fonte: Proceedings of the 11th International Chemical and Biological Engineering Conference, 2011
Conferência: CHEMPOR 2011 - 11th International Chemical and Biological Engineering Conference, September 2011.
Editor: FCT/UNL
Tipo de Documento: Proceeding Paper
Resumo: This study, reports experimental work on the use of new heterogeneous solid basic catalysts for biodiesel production: double oxides of Mg and Al, produced by calcination, at high temperature, of MgAl lamellar structures, the hydrotalcites (HT). The most suitable catalyst system studied are hydrotalcite Mg:Al 2:1 calcinated at 507 °C and 700 °C, leading to higher values of FAME also in the second reaction stage. One of the prepared catalysts resulted in 97.1% Fatty acids methyl esters (FAME) in the 1st reaction step, 92.2% FAME in the 2nd reaction step and 34% FAME in the 3rd reaction step. The biodiesel obtained in the transesterification reaction showed composition and quality parameters within the limits specified by the European Standard EN 14214. 2.5% wt catalyst/oil and a molar ratio methanol:oil of 9:1 or 12:1 at 60–65 °C and 4 h of reaction time are the best operating conditions achieved in this study. This study showed the potential of Mg/Al hydrotalcites as heterogeneous catalysts for biodiesel production.
NANOFILTRATION FOR THE TREATMENT OF COKE PLANT AMMONIACAL