Marin, Guy

Thybaut, Joris

Toch, Kenneth

English

Ghent University Academic Bibliography

FACULTY OF ENGINEERING ANDARCHITECTUREEthylene Oligomerization on Bifunctional Heterogeneous Catalysts:Model Development and Catalyst OptimizationK. Toch, J.W. Thybaut and G.B. Marin E-mail: Kenneth.Toch@UGent.beUniversiteit Gent, Laboratory for Chemical Technology Krijgslaan 281 (S5), 9000 Ghent, Belgium  - http://www.lct.UGent.beIntroduction and Objective Experimental Study Modelling Approach: SEMK Valorization of natural gas and biogas by OxidativeCoupling of Methane, followed by Oligomerization to1.8wt% Ni-SiO2-Al2O3absence of acid catalysisSingle-Event MicroKinetics: classification of elementary steps into reaction families Liquids (OCMOL)[1] Detailed mechanistic → determination of metal-ion kinetics(energetic/enthalpic considerations) accounting for symmetry effects (entropic consideration)insights lead to an ‘in-silico’ optimization of both the catalyst and 4.89wt% Ni-Betaboth metal-ion as acid catalysis pre-exponential factors calculated based on statisticalthermodynamicsprocess conditionsapplied (Model Based → determination of acid kineticsOperating conditions: activation energies/reaction enthalpies: determined byregression catalyst descriptors: catalyst propertiesCatalyst Design)[2]T: 443 – 523 K | p0C2: 1.0 – 3.5 Mpa | Wcat/F0: 4.0 – 15.0intrinsic kinetics regime (absence of transport limitations) kinetic descriptors: reaction family propertiesMetal-ion kinetics determination Acid kinetics determination 1.8wt% Ni-SiO2-Al2O3 is highly selective towards dimerization (83-86%)→mainly production butenesC2H4 C HC2H4C2H4 C4H8C2H4metal-ion activity4.89wt% Ni-Beta is highly selective towards dimerization (>80%) →mainly production butenes→ maximum up to C8 detected→ no odd carbon numbered componentsNi+Ni+Ni+Ni+2 4 C4H8Ni+ ...metal-ion activityinsertionchemisorptionchemisorptioninitiation→ maximum up to C8 detected→ lower activity (≈60%) than 1.8wt% Ni- Product selectivities independent of operating conditions18C2H4 C2H4metal-ion activityterminationSiO2-Al2O3but:→ formation of odd carbon numbered 121416 C4H8C4H8C4H8C8H16 H+C8H16acid activity components (C3 and C5) Alkylation of C4 to C8, with consecutive  6810Yield (%)ButeneHexeneH+H+ H+ alkylation, isomerization ...acid activityalkylation / beta-scission(de-)protonation(de-)protonationcracking to C3 and C5 components→ selectivity towards C3 and C5: 0.5–2.0%182022024141622.510121416Conversion (%)0 5 10 15 20 25Conversion (%)1012calculated (%)1.5calculated (%)468Conversion (%) Insertion/termination mechanism inspired by homogeneous polymerization kinetics68XC2-calculated (%)0.51Scr-calculated (%)020 5 10 15W/F° (kgcat s molC2-1) Parameters estimates by regression to 51 exp. data points→ significant parameter estimates44 6 8 10 12 14 16XC2 - experimental (%)00 0.5 1 1.5 2 2.5Scr - experimental (%)p0C2 = 3.5 MPa | : 443 K, : 473 K, : 493 K→ adequate model predictionsCatalyst descriptors ΔHphys(C2) ΔΔHphys(2C) ΔHchem(C2) Kinetic descriptors Ea,ins Ea,ter Catalyst descriptors ΔHphys(C2) ΔΔHphys(2C) ΔHchem(C2) ΔHpr Kinetic descriptors Ea,alkEst. value (kJ mol-1) -7.2 ± 0.2 -12.3 ± 0.4 -49.9 ± 0.6 Est. value (kJ mol-1) 76.3 ± 0.6 67.8 ± 0.6 Est. value (kJ mol-1) -4.9 ± 1.7 -9.9 ± 2.6 -39.3 ± 0.7 -46.6 ± 18.9 Est. value (kJ mol-1) 65.1 ± 22.5phys: physisorption, chem: chemisorption, ins: insertion, ter: termination phys: physisorption, chem: chemisorptio, pr: protonation, alk: alkylation‘In Silico’ Catalyst Development The SEMK model for ethylene oligomerization, including the kinetic 2.55.00descriptors, as ‘engine’ of the catalyst development toolAdjustable parameters:→ catalyst descriptors, c.q.,  catalyst properties2Selectivity (%)GasolinePropylene3.004.00Selectivity (%)GasolinePropylene→ reaction conditionsObjective function defined on economic relevant base11.5Selectivity (%)2.00Selectivity (%)e.g., maximization of the yield of gasoline or propylene0.5Selectivity (%)1.00Selectivity (%)0423 473 523 573 623 673 723 773Temperature (K)0.0010 30 50 70 90ΔHpr (kJ mol-1)Low temperature: only metal-ion catalyzed reactionsNi-Beta studied, p0C2 = 3.5 MPa, Wcat/F0 = 1.0 kgcat s molC2-1modified Ni-Beta, T = 573 K, p0C2 = 3.5 MPa, Wcat/F0 = 1.0 kgcat s molC2-1however: Simultaneous determination of catalyst properties and Future WorkConclusions High temperature: increasing importance of cracking reaction conditions is a difficult optimization problem Expand the experimental dataset on the Ni-Beta  Ni-SiO2-Al2O3 and Ni-Beta allowed to investigate resp. the metal-ion and acid catalyzed → increased insight in the effect of the reaction conditions on the catalyst’s activity→ input for the kinetic modeloligomerization kinetics in detail Ni-SiO2-Al2O3 studied is more active than Ni-Beta Expand and refine the kinetic model→ more significant determination of catalyst and kinetic descriptors Use the refined kinetic model as ‘engine’ for the catalyst development tool→ lower chemisorption enthalpy of ethylene → lower physisorption enthalpies of the olefins Catalyst descriptors were determined significant[1] http://www.ocmol.eu→ determine a full set of optimal catalyst properties and reaction conditions for different, economic relevant, objective functions, e.g., maximized gasoline yield Optimal reaction conditions and catalyst properties determination using the tool is possibleThis presentation reports work undertaken in the context of the project “OCMOL, Oxidative Coupling of Methane followed by Oligomerization to Liquids”. OCMOL is a Large Scale Collaborative Project supported[2] J.W. Thybaut, I.R. Choudhury, J.F. Denayer, G.V. Baron, P.A. Jacobs, J.A. Martens and G.B. Marin, Top. Catal. (52) 1251 - 1260by the European Commission in the 7th Framework Programme (GA n°228953). For further information about OCMOL see: http://www.ocmol.eu or http://www.ocmol.com.

Ethylene oligomerization on bifunctional heterogeneous catalysts: model development and catalyst optimization

https://biblio.ugent.be/publication/4294003/file/4294009

Ethylene oligomerization on bifunctional heterogeneous catalysts: model development and catalyst optimization

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