The effect of elevated gravity on the crystallization of the MFI zeolites, ZSM-5 and silicalite

The primary objective of this research was to study the effect of applying an elevated gravitational force on the crystallization of zeolites, in particular, ZSM-5/Silicalite. Experiments were performed to evaluate the influence of gravity on crystal growth rate, size, product yield, and crystal morphology. These results were used to postulate a fundamental synthesis mechanism for zeolite crystals produced under the effects of elevated gravitational field. All the experimental work was carried out at 180{dollar}spcirc{dollar}C and different gravities, 1, 10, 30, and 50 G. The molar composition of reaction mixture used for silicalite synthesis was 100SiO{dollar}sb2{dollar}-2800H{dollar}sb2{dollar}O-2.55Na{dollar}sb2{dollar}O-5TPABr. All the experimental conditions and sources of reactants were kept constant. In this work, three different experimental systems were applied to the above molar composition. The first set of experiments was carried out at one day intervals under gravity conditions, 1, 30, and 50 G. In the second set of experiments the reaction mixtures were prepared using different silica source, that is, amorphous precipitated silica while the other sources and experimental conditions were kept constant. These experiments were carried out for one day intervals under 1 and 50 G. In final set experiments, the combinations of high and normal gravities were applied and the reactions were carried out under the mixtures of high and normal gravities.; Results for all the runs showed the substantial enhancements in crystal size, product yield and a reduction in the reaction time when compared to the normal gravity. Additionally, a minimum pH was obtained from the sample which produced the largest crystals and had the highest product yield. It was also found by TG-DTG analysis that the variation of TPA{dollar}sp{lcub}+{rcub}{dollar} concentration in solution during the synthesis of silicalite under elevated gravity was directly related to (strongly associated with) rapid crystallization and redissolution processes, suggesting a solution phase mechanism (type A). Finally, it was found that the elevated gravity enhanced the crystal sizes and product yields of ZSM-5 and zeolite A, indicating that similar increases in crystal size and yield can be realized with the application of elevated gravity to the synthesis of different types of zeolites.; Although more extensive experimentation is required to completely understand the role of gravity, the most significant conclusion that can be drawn from this work is that the synthesis of zeolite under an elevated gravitational field enhances zeolite crystal size and yield. The growth of large zeolite crystals with high yields has historically been one of the most significant technical problems facing zeolite producers. This initial work will provide a fundamental basis to other researchers for further studies of the effects of gravity on zeolite synthesis.