Operandomonitoring of mechanisms and deactivation of molecular catalysts

Abstract

Observing and understanding the phenomena associated with the reaction mechanisms and catalyst deactivation in molecular catalysis is a very challenging task in green chemisty. This knowledge is crucial for applying...

Heterogenized Molecular Rhodium Phosphine Catalyst within Metal-Organic Framework for Ethylene Hydroformylation

“…The kinetic profile obtained for the best performing heterogeneous catalyst, MOF-808-2.0DPPB-RhH, showed a constant production of propionaldehyde for 3 hours which then slowed down slightly (Figure S53). This modification of reaction kinetics might be caused by an inhibition of active site in line with the increased propionaldehyde concentration, as previously reported for homogeneous counterparts, 59,60 and a change in gaseous substrates concentration in the solvent. A change of the reactor head-space for fresh gaseous feed allowed the reaction to restart with similar initial activity, highlighting the limitation due to change in reactant concentration in the closed vessel upon propionaldehyde production after 3 hours at 110°C and 20 bars (Figure S53).…”

Coordination assembly enables highly selective catalytic hydroaminomethylation of olefins

“…The less bulky N-methyl groups, NHCs with π-size extended NHC rings derived from benzimidazolium (BnzIm) and pyrenoimidazolium (PyrIm) salts, were also selected. Finally, in view of the possible deactivation of bis-NHC-metal complexes by clustering at high temperatures and pressures, [40][41][42][43] a self-supporting strategy [44][45][46] was used to support and isolate the Rh centers by NHC ligands, thus also providing an opportunity to access heterogenized molecular catalysts (Fig. 1c).…”

Deactivation of macroporous ion-exchange resins by acetonitrile and inhibition by water in the simultaneous synthesis of ethyltert-butyl ether (ETBE) andtert-amyl ethyl ether (TAEE)

“…spectroscopic techniques such as Raman, X-ray, FTIR and NMR, are applied under real operating reaction medium and conditions allowing for identifying unstable intermediates providing thus more insightful information between the catalyst state and the reaction kinetics. 15 The deactivation of sulfonated IER can proceed through several mechanisms: neutralization, desulfonation, deposition (fouling) and decrosslinking of the polymer matrix, 16 being neutralization the major cause of activity decay in industrial etherification reactors. In this mechanism, active sites are progressively neutralized on stream by base compounds present in the olefinic streams from fluid catalytic cracking (FCC) units through either plug flow or diffused flow neutralization.…”

“…14 The classic approach for monitoring deactivation is to analyze reaction kinetics and product mixtures ( ex situ ) aiming to detect compounds associated with a deactivation process. 15 In addition, in situ methods by spectroscopic measurements have also been widely applied. Finally, operando analytical methods, e.g.…”

“…spectroscopic techniques such as Raman, X-ray, FTIR and NMR, are applied under real operating reaction medium and conditions allowing for identifying unstable intermediates providing thus more insightful information between the catalyst state and the reaction kinetics. 15…”