Exploring Between the Extremes: Conversion‐Dependent Kinetics of Phosphite‐Modified Hydroformylation Catalysis

Abstract

The kinetics of the hydroformylation of 3,3-dimethyl-1-butene with a rhodium monophosphite catalyst has been studied in detail. Time-dependent concentration profiles covering the entire olefin conversion range were derived from in situ high-pressure FTIR spectroscopic data for both, pure organic components and catalytic intermediates. These profiles fit to Michaelis-Menten-type kinetics with competitive and uncompetitive side reactions involved. The characteristics found for the influence of the hydrogen concentration verify that the pre-equilibrium towards the catalyst substrate complex is not established. It has been proven experimentally that the hydrogenolysis of the intermediate acyl complex remains rate limiting even at high conversions when the rhodium hydride is the predominant resting state and the reaction is nearly of first order with respect to the olefin. Results from in situ FTIR and high-pressure (HP) NMR spectroscopy and from DFT calculations support the coordination of only one phosphite ligand in the dominating intermediates and a preferred axial position of the phosphite in the electronically saturated, trigonal bipyramidal (tbp)-structured acyl rhodium complex.

On generalized Borgen plots. I: From convex to affine combinations and applications to spectral dataSpectra

“…If D has negative matrix elements, then D -" A is a necessary condition which guarantees that the geometric constructions work properly; otherwise, at least one vertex of INNPOL-RS would be located outside FIRPOL-RS. In Figure 2, INNPOL-RS and FIRPOL-RS are shown for " A = 1.0054 10 -4 , and for FT-IR spectroscopic data from [5], see Section 4 for details. for`= 1, : : : , s the affine hull of these s points t (`) includes INNPOL-RS.…”

“…In Figure 1, the AFS with RS-scaling M and the AFS with FSV-scaling M for an FT-IR data set from the rhodium-catalyzed hydroformylation [5] are shown. Obviously, the AFS segments look quite different.…”

“…However, these test calculations demonstrate how increasing or decreasing " C or " A changes the form of the AFS. In Figure 6, the three black circles in each AFS represent the positions of the final pure component spectra which have been determined by means of a kinetic model in [5]. The smallest element of D is -0.000101.…”

“…An experimental spectral data set is considered from the rhodium-catalyzed hydroformylation process (see [5] for experimental details). This data set comes with a number of k = 1045 FT-IR spectra, each with n = 664 spectral channels.…”

“…This low-dimensional representation of feasible solutions of the factorization problem is called the area of feasible solutions (AFS). A typical example of an AFS is shown in Figure 1 [5]. In 1985, Borgen and Kowalski described two geometric algorithms to construct the AFS, namely, the tangent algorithm and the simplex rotation algorithm.…”