Synthesis And Properties Of ZSM-5 Type Zeolite Membrane

ZSM-5 zeolite membranes have drawn increasing attention in recent years because of their well-defined crystalline structures and good characteristics such as ion exchange, catalysis, adsorption and molecular sieving, compared with other inorganic membrane materials. The study of the synthesis and application of ZSM-5 type zeolite membranes will be of important significance. In this paper, the synthesis, influencing, factors on the formation of ZSM-5 zeolite membrane, Fe-ZSM-5 zeolite membrane and relation between the synthesis of ZSM-5 membrane and that of ZSM-5 zeolite were studied systemically using n-butylamine as a template on c~-Al2O3 ceramic tubes with length of 250mm and pore diameter of 3-5~im using the conventional method and the novel method of spraying seed coating for the first time. Dehydrogenation of ethylbenzene to styrene on Fe-ZSM-5, ZSM-5 and silicalite-I zeolite membrane reactors were studied and the effect of the permeability of the zeolite membranes on this reaction has been investigated in detail. The influence of calcination on the NBA-ZSM-5 membrane and its effect on both crack formation and gas permeation property were discussed. The zeolite membranes synthesized were characterized by XRD, IR, SEM, DTA and single gas permeation property. (1) it has been shown that the surface property?and pore size of substrates are one of the important influences on the formation of ZSM-5 membranes. Not uniform of the surface of substrate results in forming the defect membrane which has low gas permeselectivity. The substrate with smaller pore diameter which surface is modified by spray seed coating or Sol-gel technique is beneficial to the synthesis of the zeolite membrane with high quality. The formation of zeolite membrane is different from that of the zeolite crystals in the system of synthesis. The formed membrane on the substrate is perfect when the crystallinity of zeolite crystals formed in the autoclave is around 80%. The quality of zeolite membrane is related with the crystal size of zeolite formed on the substrate. The property of zeolite membrane with smaller and spherical crystals is better than that with bigger and rectangle crystals. The smaller crystals are preferably produced and the perfect membranes are formed by adopting ageing at low temperature and queching during the crystallization. Addition of seeds in the synthesis autoclaye is beneficial to the formation of crystals, however, Addition of seeds on the surface lv of substrate is suitable for the formation of membrane with high quality. Good crystals are a prerequisite to the formation of perfect membrane during the synthesis. (2) The synthesis ZSM-5 zeolite membrane was studied using a novel method of spraying coating of seeds. The effect of the concentration of Si02, seeds and the seed quality on the formation of ZSM-5 membrane was discussed. It indicated that when the concentration of Si02 is too high, the seeded surface coating on the substrate is easy to crack. On the contrary, it is uncontinuous. Under the condition of the concentration of 14%-.-15% for Si02, lOgIl?0g/l for the smaller and uniform seeds, a continuous ZSM-5 membrane is produced. New results for permeation of H2, C3H8 and C4H10 reveal that H2 permeability is as high as 2.8Sxl06mo[s~m2P&1, separation factors for H2/C3H8 and H2/C4H10 are as high as 27.65 and 41.13 respectively through the ZSM-5 membrane synthesized using a novel method in two times.