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These methods have some limitations and cannot be commercialized.
In yet another embodiment of the invention, the autoclavation pressure is varied from 20 to 50 atm near to sub-critical and supercritical pressure of the organic solvent used.In one embodiment of the invention, the organic solvent used is selected from the group consisting of methanol, acetone, isopropanol, acetonitrile and ethanol.In another embodiment of the invention, water is used as a co-solvent along with the organic solvent.(4) The definite Si/Al ratio in the gel and the product (5) product yield.Objects of the invention Accordingly it is an object of the invention to provide a process for the preparation of ZSM-5 catalyst which is commercially feasible.The ZSM-5 catalyst was initially prepared within eight days, typically at 150°C for six days.
There are various attempts to reduce the time of the autoclavation from six days to two days by seeding gel method (Microporous Materials 22, 626-627 (1998).
It is another object of the invention, to provide a process for the preparation of ZSM - 5 catalyst which shows high X-ray and crystalline phase purity and specific Si/Al ratios.
It is a further object of the invention to provide a process for the preparation of ZSM- 5 catalyst which provides a high product yield in short autoclavation time.
The attempts have been made to reduce the autoclavation time by using anionic promoters like HPO (Nature, 381, 298 (1996)) and by varying ratios of various precursors (Zeolites 12, 943 (1992)).
Many other patents have been reported in the literature.
In another embodiment of the invention, the Si/Al atomic ratio in the seeding gel is varied thereby controlling the Si Al atomic ratio in the as synthesized ZSM-5.