The polylith reactor as an alternative to the monolith and the randomly packed-bed reactor

摘要

A novel type of structured catalyst packing is proposed, the polyLith reactor (PLR), that can have higher mass and heat transfer and lateral mixing rates than monoliths, at lower pressure drop than across randomly packed fixed-bed reactors (FBR). The PLR consists of a regular array of catalyst rods that are arranged under a certain angle with the main flow direction and are grouped in alternating layers. By varying the angle of the rods with the main flow direction, the pitch of the rods and the rod diameter, the balance between pressure drop, mass/heat transfer and mixing can be optimized. For an angle of 00 the hydrodynamic characteristics of the PLR resemble those of a monolith, and for an angle between 45 and 60° and a voidage around 0.4, those of an FBR. To assess in which cases a PLR might be preferable over a monolith and/or FBR in case of gas/solid catalytic reactions, the three alternatives were compared quantitatively, using correlations from the literature as well as original experimental data. The PLR is shown to give abetter performance than both the monolith and the FBR in two cases: (1) for reaction rates slow enough to neglect film diffusion resistance, if there is a strong heat effect or lateral mixing is important for other reasons, such as selectivity: (2) for reaction rates so fast that film diffusion determines the overall rate, if the gas contains dust.