Zeolite Beta was grown in the microgravity environment (10-3-10-5g) of the International Space Station from the precursor solutions held unmixed until activation on orbit. The space-grown product had the same spheroidal and truncated square bipyramidal particle morphology, and close to identical "surface" and framework Si/Al ratio, and the same unit cell dimensions as the terrestrial/control product. However, the flight particles were ∼10% larger on average. The less intense terminal silanol infrared band acquired for the flight particles was consistent with their larger average size, but may also indicate a more uniform or "smoother" surface. The Meerwein-Ponndorf-Verley reduction of 4- tert -butylcyclohexanone with 2-propanol performed using the heat-treated flight samples showed lower catalyst activity and higher tr -4- tert -butylcyclohexanol selectivity when compared with the terrestrial/controls. This suggests smaller amounts of aluminum partially coordinated to the framework (as characterized by the ∼3670 cm-1 infrared band), and more space being available in the straight channels of the flight zeolite Beta for hydrogen transfer (i.e., no steric hindrances). This is consistent with a higher degree of perfection and order in the space-grown zeolite Beta framework, and higher degree of thermal stability of the flight product.
- Hydrothermal synthesis
- Meerwein-Ponndorf-Verley reaction
- Zeolite Beta