A new generation of MFI-type zeolite pellets with very high mechanical performance for space decontamination

Abstract

MFI-type zeolite pellets were elaborated with a hydraulic press in the presence of a small amount of binder (methylcellulose (MC) or anhydrous sodium metasilicate (Na2SiO3)) for molecular decontamination, in particular for the space field. The influence of the compression load and the amount of binder was investigated to determine the optimum conditions to get pellets with high mechanical performances and high adsorption capacities. The compression load varied from 2 to 8 tons and the amount of binder varied from 5 to 20 wt% of the total pellet weight. Nitrogen sorption–desorption revealed a small loss of micropore volume (17%) with a compression load of 8 tons (0.15 cm3/g instead of 0.18 cm3/g for the MFI-type zeolite powder), which can be attributed to a partial amorphization. Adsorption kinetics of n-hexane showed that the optimum pellets can adsorb volatile organic compounds. Indeed, MFI-type zeolite adsorbs 7.6 molecules of n-hexane per cell whereas the pellets made with 5 wt% of MC or Na2SiO3 adsorb about 7 molecules of n-hexane per unit-cell, respectively. These results are coherent with the ones obtained with nitrogen sorption–desorption. Uniaxial compression tests showed that the addition of small amount of binder in the mixture really improved the mechanical performances: the ultimate compressive strength was multiplied by 8 (10 MPa for the pellets without binder) when only 5 wt% of MC are used (80 MPa), with a compression load of 4 tons.