Introduction of ZSM-5 Zeolite into Micro Channels

Rebrov et al. [158] synthesized ZSM-5 zeolite in micro channels. The main focus of this work was to assess the performance benefits of zeolitic coatings in micro channels compared with conventional zeolite-based pellets and powders. The coatings were performed in a sandwich of two plates of 1 cm length and width at a thickness of 2 mm. The plates carried seven channels each, which were 1 cm long and had a diameter of500 pm. The plates were positioned at a distance of280 pm from each other in the housing of the reactor. A zeolitic film of one crystal thickness was formed under the optimum synthesis conditions, which were determined as a water/silicon ratio of 130 and a template/aluminum ratio of 2 at a temperature of 130 °C after 35 h on a flat plate. The Si/Al ratio of the zeolite, which also lowers the crystal size when decreased, was optimized to a value of 28. 

To obtain a uniform distribution of the zeolite in the micro channels, a two-step procedure was developed, including nucleation growth at high temperature at the horizontally oriented plates followed by a growth period at the vertically oriented plates, which was performed at lower temperature and water/silicon ratio. The crystals were oriented parallel to the surface of the carrier. Nitrogen adsorption revealed the typical micropore distribution of ZSM-5 for the coating. Thermal cycling 

By XRD analysis, high crystallinity of the coatings exceeding 90% was determined. 

The crystallization took place on the whole platelet and the crystal layer had to be removed mechanically from the flat surface. 

Input from the earlier work summarized above [158] was used by Rebrov et al. 

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