Case Study 3

Zeolite microparticle synthesis

Problem

Zeolites are aluminosilicates composed of SiO4 and AlO4 tetrahedral structures assembled into porous 3D materials. The arrangement of the tetrahedra into a porous structure results in regular arrays of openings and voids (microporosity), allowing some molecules to be selectively incorporated into the microporosity, while others are rejected due to steric effects or affinity differences.

LTA, FAU, and MFI zeolites are known for their large to medium pores (1.1, 0.8, and 0.55 nm, respectively), which make them an attractive material for catalytic and adsorption applications. Zeolites are synthesized by hydrothermal processes in which aluminate and silicate solutions are mixed before being subjected to an induction (aging) phase, during which nucleation occurs, and then heated (reactive crystallization) to cause crystal growth at high temperature.

This process is usually carried out in closed containers (i.e. batch process) and takes a long time to complete crystallization. The long aging time (slow step of several hours, at low temperature below 40°C), which is not compatible with a continuous synthesis process, should be avoided by adding germs or preformed germs directly into the reaction mixture or „gel“.

Objectives of SIMPLI-DEMO

In SIMPLI-DEMO, the existing COBR pilot plant will be further upgraded to TRL7.

• Further work will be carried out on the various aspects of the process along the COBR (mixing, heating, reacting, ripening).

• The number of diverter elements as well as the overall length of the COBR will be optimized. MW is used in the upstream and crystallization sections for rapid and versatile heating of reagents and/or synthesis gel.

• Ultrasound is used to improve dissolution/mixing in the upstream section during synthesis gel or seed production, to improve mixing during crystallization, to prevent clogging in the continuous reactor, and to deagglomerate the particle aggregates at the end of the crystallization step.