Maniut, C.

Otto, T.N.

Pitter, S.

Otto, T. N.

KITopen

Forschungszentrum Karlsruhe GmbH, Institut, Postfach 36 40, 76021 KarlsruheInstitut für Technische Chemie, Bereich Chemisch-Physikalische Verfahrenmit der Universität Karlsruhe verbunden inForschungszentrum Karlsruhein der Helmholtz-Gemeinschaft0 60 120 180 240Zeit / Min00.20.40.60.81-Octen Konzentration / Mol .  L-11-Octenn-Nonanali-NonanalIntroductionThe hydroformylation of olefins is one of the industrially most important homogeneously catalyzed reactions. Since early 90th, supercritical carbon dioxide (scCO2) has been investigated as an alternative medium replacing conventional organic solvents in hydroformylation. The physical-chemical properties of scCO2 are between those of liquids and gases. In catalysis applications, the tuneable solvent properties of scCO2 can result in a variety of effects, such as affecting kinetic rates by both temperature and pressure, shifting equilibrium constants in favour of the desired products, and increasing selectivity and yields. One particular benefit of scCO2 is that interface diffusion does not take place.In this work we present our recent studies on Co2(CO)8 catalyzed hydro-formylation of 1-octene in scCO2.A Kinetic Model for the Hydroformylationof 1-Octene in supercritical CO2Constantin Maniut, Thomas N. Otto and Stephan Pitter*MicrokineticsKinetic parameters for the formation of n- and i-nonanal from 1-octenewere determined from the reaction mechanism established by DFT calculations.Kinetics and Formal KineticsAn activation enthalpy of 117 kJ mol-1 for 1-octene hydroformylation was determined in the range between 90 and 150°C. Experiment series at various concentrations of each 1-octene, CO, H2 and Co2(CO)8 were performed, with 1-octene conversion expressing the rate of hydro-formylation. Initial reaction rates and concentrations were determined at 120°C.The following equation (1) was used to describe the reaction rate.ExperimentalExperiments were carried out in a parallel six-reactor system allowing for faster exploration of process parameters up to 350 bar pressure.Automation of reactant dosing, experiments and data recording was performed using a programmable controller. Samples for kinetic analyses were quantitatively analyzed by GC.20.56 0.9 1.68 0.8811.68 0.561 1(1 ) (1 )octene H CO ComodelCO CO octene octenek c c c crK c K c−−−− −⋅ ⋅ ⋅ ⋅− = + ⋅ ⋅ + ⋅Constants in Eq. (1) were fitted to k = 13, KCO = 0.2 and K1-octene = 0.3.As most of the variable influences studied are well expressed by this model, influence of low CO partial pressure (Fig. Right) is not descri-bed satisfyingly. Formal kinetics can also not describe regioselectivity.(1)-80-60-40-20020406080DLTS1ELTS5TS7TS3GLFLHLTS9IL∆G#  (kJ·Mol-1)∆H  (kJ·Mol-1)DVTS2EVTS6TS8TS4GVFVHVTS10IV∆G#  (kJ·Mol-1)∆H  (kJ·Mol-1)For both pathways oxidative addition of H2 through transition states TS7(finally yielding the linear product) and TS8 (yielding the branched product) is energetically the rate-limiting step.From thermodynamical values calculated for all intermediates, the respective rate constants ki and k-i of the elementary reactions were determined. Co2(CO)8+1-OctenDLDVELEVFLFVHLHVGLGVn-nonanali-nonanalCO H2+H2HCo(CO)4isomerization,hydrogenationk3k 1k4k-3k-4k5 k7 k9 k11 k13r6 k8 k10 k12 k14k-5 k-7 k-9 k-11r-6 k-8k-10 k-12k I, H k -I, -Hk’I, Hk’-I, -HILIV+1-OctenCOisomerization,hydrogenationThe non-linear microkinetic model for the hydroformylation pathways was constructed using the SIMULINK toolbox integrated in Matlab®. Visualization of concentrations as function of reaction time took place by utilization of programmable S-function modules in SIMULINK.Regioselectivity in aldehyde formation is explained from the difference in activation enthalpy through transition states TS5 and TS6, respectively. The microkinetic model quantitatively describes the concentration profiles of the corresponding products in the catalytic cylcle, (Co(CO)3-CO-C8H17), GL and GV (here in dependence from initial 1-octeneconcentration), in a stirred tank-reactor.0 200400 600800 1000120000.20.40.60.800.010.02Zeit / M in[1-Octen] / Mol ⋅ L-1[GL] / Mol ⋅ L-10 200400 600800 1000120000.20.40.60.800.10.2Zeit / M in[1-Octen] / Mol ⋅ L-1[GV] / Mol ⋅ L-1In contrast to formal kinetics the microkinetic model is able to reproduce also the rate a low CO partial pressure (Fig. Left) and to describe regio-selectivity on a high level of accuracy.Additionally it allows for the extra-polation outside the experimental range. modeltime / minc / Mol L-1 0 60 120 180 240Zeit / Min00.20.40.60.81-Octen Konzentration / Mol .  L-11-Octenn-Nonanali-NonanalModel,1-octenetime / minc / Mol L-11-o t nen-nonanali-n al-octenenonanal-nonanaltime / minc (1-octene) / Mol L -1 time / minc (1-octene) / Mol L -1c (GL) / Mol L-1c (GV) / Mol L-1hood

A kinetic model for the hydroformylation of 1-octene in supercritical CO₂

https://publikationen.bibliothek.kit.edu/220070763/3815182

A kinetic model for the hydroformylation of 1-octene in supercritical CO₂

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