Chemistry. 2014 Sep 08;20(37):11921-31. doi: 10.1002/chem.201402515. Epub 2014 Jul 31.

An operando FTIR spectroscopic and kinetic study of carbon monoxide pressure influence on rhodium-catalyzed olefin hydroformylation.

Chemistry (Weinheim an der Bergstrasse, Germany)

Christoph Kubis, Mathias Sawall, Axel Block, Klaus Neymeyr, Ralf Ludwig, Armin Börner, Detlef Selent

PMID: 25081298 DOI: 10.1002/chem.201402515

Abstract

The influence of carbon monoxide concentration on the kinetics of the hydroformylation of 3,3-dimethyl-1-butene with a phosphite-modified rhodium catalyst has been studied for the pressure range p(CO)=0.20-3.83 MPa. Highly resolved time-dependent concentration profiles of the organometallic intermediates were derived from IR spectroscopic data collected in situ for the entire olefin-conversion range. The dynamics of the catalyst and organic components are described by enzyme-type kinetics with competitive and uncompetitive inhibition reactions involving carbon monoxide taken into account. Saturation of the alkyl-rhodium intermediates with carbon monoxide as a cosubstrate occurs between 1.5 and 2 MPa of carbon monoxide pressure, which brings about a convergence of aldehyde regioselectivity. Hydrogenolysis of the acyl intermediate is fast at 30 °C and low pressure of p(CO)=0.2 MPa, but is of minus first order with respect to the solution concentration of carbon monoxide. Resting 18-electron hydrido and acyl complexes that correspond to early and late rate-determining states, respectively, coexist as long as the conversion of the substrate is not complete.

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keywords: IR spectroscopy; hydroformylation; kinetics; operando; rhodium

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• Journal Article