Kinetic investigation of lean aqueous hydroformylation - An engineer's view on homogeneous catalysis

- An inhibitory effect was observed for rhodium concentration and ligand excess.
- Substrate gases H2 and CO showed a first order influence on the rate of reaction.
- Reaction rates were linear dependent on the created interfacial area.
- Selectivity towards aldehydes was increased at high pressures and low temperatures.
- With 7.31·10−5 kmolm−3 s−1 high space time yields were reached.

The additive-free, biphasic aqueous hydroformylation of the long chain olefin 1-octene was investigated with the goal to derive a mathematical expression for the macro kinetic and to increase selectivity towards aldehydes while maintaining fast reaction rates. The influence of different important chemical parameters such as catalyst precursor, catalyst concentration, ligand excess, pH-value, salt concentration, temperature, gas pressure and gas composition was estimated. At 10 MPa and 373 K the highest rate of reaction with 41·10-5 kmolm−3 s−1 was reached. An optimal compromise between high selectivity and activity was found at 8 MPa syngas pressure and 353 K reaction temperature. Selectivity was thus increased from 20% to 76% with octene isomers as the only by-products. The rate of reaction was linearly dependent on the created interfacial area as shown in previous publications. The optimised conditions were applied to other olefinic compounds with different structural characteristics. Obtained insights were used to establish a rate expression for this reaction, incorporating the interfacial area between organic substrate and aqueous catalyst phase. This novel approach helps to draw attention towards the aspect of procedural rate enhancement in homogeneous catalysis.

Fluctuat nec mergitur: The kinetics for the aqueous biphasic hydroformylation of 1-octene is derived in cooperating procedural aspects to accelerate the reaction to industrially interesting rates. The parameter screening is additionally used to optimise the selectivity towards aldehydes.120