Heteropoly acid supported on hierarchical Y zeolite decorated SiC foam as the structured catalytic packing for reactive distillation synthesis of ethyl lactate

Abstract

Rational design of catalytic packing is crucial in developing reactive distillation (RD) processes as efficient in-situ coupling of reaction and separation is required. Structured catalytic packings are advantageous than the conventional packings (e.g., inert packing + catalyst ‘tea bags’), due to the integration of the catalysis and separation function in one unit, mitigating mass/heat transfer limits. Herein, we present one of the latest developments in the field of structured catalytic packings, which was applied to a pilot-scale RD process of ethyl lactate (EL) synthesis via acid-catalyzed esterification and showed the advantages. The tungstophosphoric acid and hierarchical Y zeolite were uniformly decorated on corrugated silicon carbide (SiC) foam sheets via new preparation method (of ultrasound-assisted impregnation and microwave-assisted drying). The activity of the resulting materials was first assessed in a batch reactor, then the best candidate was employed by the pilot process. Findings from the pilot-scale RD experiments show that the developed structured SiC foam catalytic packing (SSFCP) exhibited an excellent performance (with the normalized conversion of 0.155 mol/gcatalyst), outperforming the conventional seepage catalytic packing internal (0.002 mol/gcatalyst). The influence of various variables (including molar feed ratio, feed position and reflux ratio) on the process performance of the pilot RD rig was also investigated and optimized, achieving a lactic acid conversion of 46.9 % and EL purity of 44.9 % (bottom). The good performance was attributed to the improved mass transfer thanks to SiC foam corrugated sheet (which encourage the vortex formation), thereby enabling more efficient coupling with the reaction. The SSFCP demonstrated reasonable stability, making it a promising candidate for relevant practical RD applications.