Kinetics of catalytic hydrogenation of β-ionone and application of a presaturated one-liquid flow reactor for the production of fine chemicals

Fine chemicals are commonly produced in batch or semibatch reactors, which are frequently operated on a rather limited basis with respect to the knowledge of the kinetics. A typical example is the hydrogenation of the flavor-substance β-ionone. The previously unknown kinetics were studied under industrially relevant conditions (180-230 °C, 5-90 bar, Raney-Ni). The conversion of the triple-unsaturated β-ionone up to complete hydrogenation proceeds via a network of three parallel and four consecutive reactions. The kinetic parameters were determined, including the influence of external and particularly internal diffusion. Furthermore, the applicability of the presaturated one-liquid flow (POLF) reactor was studied. In this steady-state system, the liquid is externally presaturated with hydrogen, and then fed into a fixed-bed reactor. This leads to a simple - e.g. with respect to scale-up - two-phase system (liquid and solid catalyst) compared to common three-phase batch reactors (and also to “steady-state alternatives” like a trickle bed). For the given reaction, a liquid recycle is installed to compensate the low hydrogen-solubility. Results of experiments and modelling show the good applicability of the POLF-reactor with respect to temperature control, required reactor size, and the inherent advantages of a steady-state process.