Synthesis Of ZSM-5 Zeolite And Its Application In Ammoniation Of Ethanolamine

We synthesized ZSM-5 zeolite in hydrothermal system, with water glass and Al2(SC>4)3 ?18H2O as silicon and aluminum resources respectively. With pre-ageing of the water glass at high temperature, the induction period was shortened greatly, then the total time of crystallization was cut down. We also investigated the effect of temperature, alkalinity on crystallization. When the temperature rose, both the induction period and the growing period were cut down. When the alkalinity of system rose, the total time of crystallization was cut down too. But in the system with high alkalinity, ZSM-5 zeolite can be resolved by OH" in the solution, them more stable phase, such as alpha-quartz, would form. When the alkalinity of system was reduced, the formation of impurity crystal can be forbidden effectively.We characterized the as synthesized zeolite with powder X-ray diffraction, and calculated the crystallinity according to the data obtained by the powder X-ray diffraction. The results showed that the as synthesized zeolite was ZSM-5 zeolite with high crystallinity. We characterized the zeolite sample with transmission scanning electron microscope. The stereoscan photograph showed that the ZSM-5 crystal we obtained was regular hexagonal crystal. We also analyzed the SiCh/AbOa ratio by conventional chemical analysis.We modified the ZSM-5 zeolite by dipping, isomorphous replacing etc. ZSM-5 zeolites with different acid strength, such as F-ZSM-5, H-ZSM-5, and B-ZSM-5, or different transition metal oxide modified, such as ZnO-ZSM-5 and NiO-ZSM-5, were prepared. In which, the strength of acid site is: F-ZSM-5>H-ZSM-5>B-ZSM-5. We shaped the as prepared zeolite catalyst into < 2 X (2-4) mm cylinders. We investigated the catalytic performance of the catalysts mentioned above in the ammoniation of monoethanolamine (MEA). The reaction was carried out in a continuous tube reactor, at atmosphere pressure. The conversion of MEA reached over 95%, and the total selectivity of ethylenediamine (EDA), piperazine (PIP), and triethylenediamine (TEDA) reached over 85%.The results showed that in the catalysts with different acid strength, F-ZSM-5 is more selective to EDA. This indicated that enhancement of acid strength had passive effect on the selectivity of EDA. At low temperature, B-ZSM-5 is more selective thaninH-ZSM-5 or F-ZSM-5 to PIP and TEDA. This indicated that catalyst with media strength acid sites is more selective to PIP and TEDA.The ZSM-5 zeolite modified by transition metal oxide is more active than the unmodified ZSM-5 zeolite. The selectivity of TEDA is much more than the unmodified zeolite. This is because the ZSM-5 zeolites modified ZnO or NiO not only have many media strength acid sites, which is selective to TEDA, but also the formed PIP will react easily with MEA and form TEDA.Temperature can affect the reaction greatly. When the temperature is lower, the conversion of MEA is lower too, but the total selectivity of EDA, PIP, and TEDA is higher. On the contrary, as the temperature rises, the conversion of MEA rises too, but the side reaction increases, and the total selectivity of EDA, PIP, and TEDA is reduced. Increase of K (NHa/MEA, molar ratio) has passive effect on the selective of EDA, but has little effect on the total selectivity of EDA, PIP, and TEDA.