Hydrogenation of α-methylstyrene in an inclined rotating fixed bed reactor

Trickle bed reactors are widespread in the chemical industry for the implementation of heterogeneous catalytic processes, especially for the production of bulk chemicals. Nevertheless, the reactor performance may be limited by liquid maldistribution as well as by poor mass and heat transfer rates. Furthermore, the rather simple reactor design and operation is accompanied by limited degrees of freedom for manipulation of local conditions to enhance the reactor performance.
Dynamic operation strategies, like the periodic inlet flow rate modulation, have been proposed for process intensification of trickle bed reactors [1]. These strategies have been proven to result in increased space-time-yields at lab-scale, however, their positive effects are strongly dampened with increasing reactor length.
The inclined rotating fixed bed reactor is an alternative reactor concept, that aims to transform the temporal periodic operation into a spatial periodic one, which holds for the whole length of the reactor. The inclination of the reactor, with the catalyst fixed between two retaining grates, results in a phase separation, whereas the superimposed slow rotation ensures a periodic wetting and draining of the catalyst and will therefore enhance the access of the gas phase to the active sites (see Figure 1).
By adjustment of the reactor inclination and rotation, the performance of the reactor can be adapted to a given reaction system (e. g. fast or slow kinetics, high or low viscous liquid etc.) to optimize the local conditions with respect to flow regime and subsequently to mass and heat transfer performance for a specific process.
For the evaluation of the new reactor concept, the space-time-yield of the hydrogenation of α-methylstyrene to cumene (C9H10 + H2  C9H12) is investigated in the trickle bed reactor as well as in the inclined rotating fixed bed reactor. The reaction already exhibits mass transfer limititations of the gas phase at moderate conditions, which allows for attributing changes in the space-time-yield directly to the operational conditions [2].
The reactor (dR = 0.1 m, LR = 1.6 m) is operated like a differential loop reactor with a layer of the palladium egg-shell catalyst (Pd/γ-Al2O3, dP = 4 mm, w = 0,1 wt-% Pd) placed in the middle of the otherwise inert fixed bed. The reaction studies are performed at varying pressure (p = 1 and 6 bar) and temperature (θ = 25°C and 40°C) at isothermal conditions. The rotational speed and the inclination angle are adjusted to identify optimal hydrodynamic conditions regarding the space-time-yield.
The results of the reaction studies are discussed with respect to the prevailing flow regimes obtained by additional tomographic imaging studies for the same setup and operating conditions.