Non-invasive in situ monitoring of catalyzed chemical reactions can show and probe the stability of the catalyst and ensure a high yield of the desired chemical processes. Infrared in situ measurement techniques in attenuated total reflection (ATR) and transmission mode were used to assess the feasibility of these methods and ultimately compare their ability to monitor and detect active or degrading catalyst species. Four different process configurations were used, namely (i) a stirred tank reactor equipped with ATR-IR; (ii) a continuously operated miniplant with ATR-IR; (iii) a continuously operated miniplant with transmission-IR; (iv) a stirred tank reactor equipped with transmission-IR. The established hydroformylation of a long-chain olefin catalyzed by a rhodium-phosphite catalyst was taken as a representative reaction. The potential for process monitoring in molecular catalysis was evaluated. Advanced chemometric analyses by Band Target Entropy Minimization (BTEM) were performed following spectral monitoring to obtain pure component spectra estimates as well as relative time-dependent concentration profiles. In general, this study showed that infrared measurements in transmission mode are able to detect active catalytic species and can follow deactivation phenomena in batch reactions and continuously operated miniplants. Apart from the substrates and products, a number of catalytic intermediates appear to be in equilibrium exchange at reaction conditions and hence the deconvolution of multispecies spectra exhibits superimpositions of these species. Quantum chemical calculations support the structural identification of measured vibrational spectra. This comparative study of ATR versus transmission and batch experiment versus continuously operated miniplant shows that transmission IR is capable of getting in-depth spectroscopic data that can be deconvoluted by BTEM. A distinct dosing strategy is important to get meaningful data on the molecular catalyst under process conditions. This study gives a unique perspective on in situ spectroscopic infrared investigations in molecular catalysis and future process control.

Rhodium-catalysed hydroformylation is the major industrial process to obtain aldehyde products from olefins. The isomerization of the olefin at the catalyst is the most prominent side reaction and lowers the overall yield of the process. We here investigate whether the olefin isomer distribution obtained from batch experiments using Rh(BiPhePhos) as a catalyst and n-decene as the olefin reaches the thermodynamic equilibrium and computational quantum chemical approaches are able to accurately reproduce the experimental olefin isomer distribution. The relative energies of cis/trans configurational and double bond positional isomers of long chain n-decene were calculated using Hartree-Fock, DFT and correlated ab initio methods. Results were compared to experimental data. Electron correlation was found to be critical for the description of cis-isomer relative energies. Dispersion corrections in the DFT calculations partially compensate for deficiencies and generally improve the agreement with experiment. Adding thermodynamic corrections suffers from the neglect of certain contributions to the entropy of flexible molecules. Accounting for the entropy of mixing of multiple conformers significantly reduces the deviation from experiment. The equilibrium distribution of long chain olefins is reasonably described by correlated QM and also some density functional methods. Computational thermochemistry has thus reached a state where it provides reliable parameters for complex reaction network models and process engineering.

The transformation of chemical production processes to a sustainable feedstock from renewable sources requires a careful assessment of current thermodynamic data, reaction mechanisms and kinetics. The Pd-catalyzed alkoxycarbonylation of the long chain olefin methyl 10-undecenoate (10-UME) from castor oil with methanol yields the building blocks for a renewable polyamide. The mechanism for the complex multi-step reaction cycle including active catalyst formation was elucidated. The experimental catalyst selectivity with 1,2-bis(di-tert-butylphos-phino-methyl)benzene (1,2-DTBPMB) as a ligand towards the desired linear diester product can be reproduced and rationalized. The mechanisms of possible side reactions and well as catalyst inhibition by carbon monoxide were also investigated. Solvent effects have an influence on reaction equilibria and transition barriers. These were considered in polar (methanol) and nonpolar (dodecane) media using implicit or mixed cluster/ continuum solvation models when explicit solvent coordination was critical.

This work investigates solvent effects on the reaction equilibrium of the 1-dodecene hydroformylation in a decane/N,N-dimethylformamide solvent system. The reaction was performed at different decane/N,N-dimethylformamide ratios and at temperatures between 368 K and 388 K. The equilibrium concentrations of all reactants and products were determined experimentally. The enthalpy and Gibbs energy of this reaction at the ideal-gas standard state were determined by quantum-chemical calculations in good agreement with literature data. Moreover, quantum-chemically calculated standard Gibbs energies of reaction at infinite dilution in liquid decane/DMF-solvent mixtures allowed a qualitative prediction of the solvent effect on the equilibrium concentrations. Based on the standard Gibbs energy of reaction at the ideal-gas standard state and on fugacity coefficients calculated using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), the equilibrium concentrations of reactants and products for the 1-dodecene hydroformylation performed in decane/N,N-dimethylformamide mixtures of different compositions could be predicted in very good agreement with experimental data.