Marin, Guy

Thybaut, Joris

Toch, Kenneth

English

Ghent University Academic Bibliography

Towards an Optimal Ethylene Oligomerization Catalyst based onSingleK. Toch, J.W. Thybaut*, G.B. MarinLaboratory for Chemical Technology, Introduction As the worlds’ crude oil reserves are declining, the global energy demand is rising and the environmental legislation is becomingand chemicals is evermore a hot topic. methane, e.g., via ethylene formation oligomerization using homogeneous catalysselectively in even carbon atom numbered alpha over homogeneous catalysis, among others,heterogeneous catalysis offers demands, i.e., linear α-alkenesThe aim of this work is to contribute to the catalyst for ethylene oligomerization. This challenge is addressed via fundamental modeling using Single-Event MicroKinetics (SEMK)on a bench mark catalyst and will be used parameters, which can be classified as kinetic and descriptors can be varied through simulation, in order to identify the optimal catalyst behavior. Procedures Experiments are performed in a fixed bed plugcatalyst impregnated with 1.8 wt% the range in which acid catalyzed reactions are reflected in the product yieldspressures between 1.0 and 3.5 MPa are used with a molar ethylene content in the feed of The space time was varied from 3.0mass transfer limitations. A microkinetic model was constructed describing the intrinsic kinetics according to the SEMKmolecules with a maximum carbon number 10000 elementary steps. Physical ato any chemical elementary stepResults and discussion As reported in the literature [1, 3]the temperature, see Figure 1 as products resulting from a coordinated insertion mechanism of ethylene on an Figure 1: Left: experimental conversion of ethylene as function of temperature at 3.5MPa and 45.0 kgcat s molto C18) mixed for several experiments at different conditions.-Event MicroKinetic Modelling  Ghent University, Belgium, Joris.Thybaut more and more strict, the search for lowAlternative routes are being explored to valorize by oxidative coupling. At present, is is an established industrial procesalkenes. Heterogeneous catalysis is preferred  because of environmental reasons. Moreover, more opportunities to tune the product yields or a complex mixture to be used as high octane development of an active, stable and selective  [2]. An intrinsic kinetic data set is being acquired for regression purposes, i.e., to determine tcatalyst descriptors. In particular the latter -flow reactor on a bench-mark Ni. The temperature was varied from 443 K to 503 K, i.e.,  to 45.0 kgcat s moleth-1. Care is taken to ethylene oligomerization  methodology [2]. The reaction networkof 12 and consisted of over 3000 species and over dsorption of the components inside the catalyst  was included via a Langmuir isotherm. , the catalyst exhibited two regions of activity(left). At low temperatures mainly linear α-alke          eth-1; Right: chromatogram of the collected liquid phase (C @UGent.be  -emission fuels ethylene s, resulting  to the market fuel blend [1]. he model silica-alumina  [1]. Total 60%. avoid heat and  was limited to pores, prior  as function of nes are obtained     6  active nickel cation site. Between 373 and transformation of Ni occurs leading to an activity loss of the catalyst[1]. At higher temperatures, i.e., above time-on-stream up to 6 hours. spectrum shows that no cracking occurredBecause higher operating temperatures offer a wider range of possibilities for tuning the product yields, the corresponding data are assessed first present simulations have been performed using initial parameter values basedata [1] and have not been further optimized yet by regression. critical for ethylene dimerization to butene. In contrast to ethylene, which can only form primary carbenium ions, butenes can lead to more stable secondary carbenium ionsparticipate in acid catalyzed oligomerization reactionsup out of linear alkenes, C6 and heavier ion catalyzed oligomerization catalyzed oligomerization disturbs thismore pronounced with increasing temperaturestemperature of the linear alkene content in the C503 K, also illustrates the increase of thehigher temperatures.        Figure 2: Left: natural logarithm of the molar number; Right: product distribution as oligomerization included  Conclusions A microkinetic model for ethylene oligomerization at highis able to qualitatively reproduce the linear character because ethylene dimerizationC12 species are mainly branched, due to thcatalyzed reactions, deviations from the obtained. No odd carbon numbered alkenes are presentThe kinetic and the catalyst descriptors in the quantitatively determined by regression and optimal catalyst descriptor valuesidentified. Acknowledgements The research leading to these results has received funding from the European Community's Seventh Framework Program FP7/2007References  [1] Heveling, J., C.P. Nicolaides, and M.S. Scurrell, Applied Catalysis a(1998). [2] Thybaut, J.W., I.R. Choudhury, J.F. Denayer, G.V. Baron, P.A. Jacobs, J.A. Martens, and G.B. Marin, Topics in Catalysis, [3] Sohn, J.R., Catalysis Surveys from Asia, 403 K, in the presence of ethylene below this 423 K, stable catalyst behavior was obtainedThe absence of odd carbon numbered alkenes , see Figure 1 (right).  using the microkinetic model. At The metal. While the C4 fraction fractions also contain branched isomersresults in an Anderson Schulz Flory distribution ASF distribution, however, see Fig, see Figure 2 right. The decrease with the 8 fraction from 43.2 % at 443 K to 25.2 % at  relative importance of acid catalyzed outlet flow rates as functionfunction of temperature, acid at 3.5 MPa and 6.7 kgcat s molether temperatures experimental trends. The C4 species formed  occurs on the metal-ion sites, while the Ce acid catalyzed reactions. Because of the acid Anderson Schulz Flory product distribution are , indicating the absence of cracking.Single-Event MicroKinetic -2013 under grant agreement n° 228953.52 (2009). 8 (2004). , an irreversible temperature  for a in the product d on literature -ion function is  that is entirely built . Pure metal-. The acid ure 2, left. This is reactions at  of the carbon catalyzed -1. is constructed and all have a 6 to  model will be  will be  -General, 173 

Towards an optimal ethylene oligomerization catalyst based on single-event microkinetic modelling

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Towards an optimal ethylene oligomerization catalyst based on single-event microkinetic modelling

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Ghent University Academic Bibliography

Ghent University Academic Bibliography