Enabling compact GTL by 3D-printing of structured catalysts

Abstract

This paper uses 3D printing methods to overcome mass and heat transport limitations in small-scale processes for the conversion of syngas to ethanol. Advances in the past two decades in nano-materials technologies had resulted in a new generation of highly active catalysts. These catalysts are formed into porous pellets or monoliths and placed into the reactors which often operate at elevated temperatures and pressures. The key problem with this arrangement is that transport rates are of different orders of magnitudes within the particles which is dominated by (slow) diffusion, and between the particles, which is set by (fast) pressure driven viscous flow. Balancing these timescales requires either (i) making the pellets very small, so that the diffusion path lengths and hence travel times are reduced – but this so severely impacts the pressure drop over the system that it is impractical; or (ii) increasing the residence time in the reactor and/or reducing the reaction rate by limiting the catalyst activity (which is the currently used solution, where typically catalyst carriers dilute the active materials by >90%), but this results in very large reactor sizes. Further, for highly energetic reactions requiring intensive heating or cooling, packed beds and monoliths becomes limited by the poor heat transfer properties of the arrangement. Poor temperature control results in reduced conversion efficiency, and a wider range of products and by-products which in turn require additional downstream separation and purification operations. Here, we discuss 3D printing approach to lay down catalysts into reactor architecture.