Kinetic investigation of lean aqueous hydroformylation – An engineer’s view on homogeneous catalysis

Abstract

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 10MPa and 373K the highest rate of reaction with 41·10–5kmolm−3s−1 was reached. An optimal compromise between high selectivity and activity was found at 8MPa syngas pressure and 353K 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.