Towards the elucidation of a chemical reaction network for the palladium-catalysed phenylacetylene oxidative carbonylation reaction
Advancing the chemical engineering fundamentals
Chemical Reaction Engineering: Kinetics & Modelling (T2-2a)
Keywords: reaction networks, modelling, complex dynamics, experimental data
Towards the elucidation of a chemical reaction network for the palladium-catalysed phenylacetylene oxidative carbonylation reaction
K. Novakovic, M.J. Willis and A.R. Wright
University of Newcastle, School of Chemical Engineering and Advanced Materials,
Newcastle upon Tyne, NE1 7RU, UK
katarina.novakovic@ncl.ac.uk; mark.willis@ncl.ac.uk; a.r.wright@ncl.ac.uk;
The palladium-catalysed phenylacetylene (PhAc) oxidative carbonylation reaction provides a novel pH and heat of reaction (Qr) oscillator operating in a stirred batch reactor (Novakovic et al. 2006). Furthermore, it provides the potential for the chemoselective synthesis of several commercially valuable products. The objective of this work is to determine reliable reaction network (rate determining reactions in a chemical mechanism) of the system. A reaction network is first requirement in the determination of the predictive kinetic model for use in reaction engineering studies, including process optimisation and scale-up.
The complex chemical dynamics associated with this reaction are studied using a three stage experimental programme. This divides the system into sub-systems in order to minimise the number of experiments needed for reaction network elucidation. The experimental programme focuses on three aspects (1) the reaction pathway associated with catalyst activation (2) the pathway associated with catalyst regeneration (3) the overall reaction network. The first two steps are necessary for the understanding of how the catalyst affects the pH and the oscillations in pH. While the third stage is used to study the interaction between the catalytic system and the behaviour of both the reactant (PhAc) and pH.
In the first set of experiments, PdI2 (the catalyst), KI (used primarily to facilitate PdI2 dissolution) and NaOAc (a buffer) in a methanol solution are purged with CO. Here, as no O2 is present the PdI2 is not regenerated hence the experimental data may be used to develop the reaction network and determine the rate constants associated with catalyst activation. A second subset of experiments is then performed with PdI2, KI and NaOAc in a methanol solution being purged with both CO and Air. The presence of O2 (Air) allows for the regeneration of the catalyst to take place. Hence, using pH measurements (no Qr is observed) the network obtained from the initial modelling studies is augmented with the new pathways and the corresponding rate constants are estimated. Finally, a third set of experiments is performed with PdI2, KI, NaOAc in methanol solution purged with CO and Air with subsequent addition of the reactant, PhAc. Quantitative analysis is used to provide time-concentration profiles of the PhAc and the products formed. This data, together with on-line measurements of pH and Qr are used to postulate and validate the final reaction network as well as estimate the associated rate constants.
Throughout the work the BatchCAD(™) software package is used for kinetic fitting. The ordinary differential equation (ODE) structures of the reaction networks are postulated based on the observations and measurements made in experiments combined with the available literature. Subsequently, these ODEs are regressed to the recorded pH, Qr and species’ time-concentration data. The structure of the reaction network is progressively modified until the simulation of the ODEs closely matches the recorded experimental data. The result is a reaction network and associated ODE model that may be used for subsequent chemical engineering design applications.
References
K. Novakovic, C. Grosjean, S.K Scott, A. Whiting, M.J. Willis, A.R. Wright (2006). "Achieving pH and Qr Oscillations in a Palladium Catalysed Phenylacetylene Oxidative Carbonylation Reaction Using an Automated Reactor System." Chemical Physics Letters, in press.
Presented Monday 17, 11:52 to 12:11, in session Chemical Reaction Engineering: Kinetics & Modelling (T2-2a).
