Description:
ZSM*5 zeolite properties
Thermal stability
High thermal stability of ZSM*5 zeolite. This is caused
by a skeleton in a stable five-membered ring structure
and a high silica to alumina ratio. For example, the
sample calcined at **0 ℃ After 2 hours, the crystal
structure unchanged. Even can withstand high
temperature of ***0 ℃. So far, ZSM*5 zeolites are known
to one of the highest qualitative hot temperature.
Therefore, it is used in high-temperature process is
particularly suitable. For example, use it as a
hydrocarbon cracking catalyst, regeneration of the
catalyst can withstand passage of time.
Acid resistance
ZSM*5 zeolite has good acid resistance, it is resistant
to various acids except hydrofluoric acid.
Steam stability
Wang, IKai other studies have shown that when other
zeolites by steam and hot water, and their general
structure is destroyed, leading to irreversible
deactivation. The Mobil company with ZSM*5 as the
conversion of methanol (water is one of the major
product) catalyst. This suggests that ZSM*5 to water
vapor with good stability. **0 ℃ lower partial pressure
of *2mmHg steaming column and HY zeolite HZSM*5 after
*4 hours, a crystallinity of HZSM*5 and about *0
percent of fresh catalyst, but under the same
conditions, HY zeolite skeleton almost completely
damage.
Hydrophobic
ZSM*5 having a high silica to alumina ratio, the
smaller the surface charge density. The water molecule
is polar, so you will not ZSM*5 is adsorbed. Although
water molecules smaller than the diameter of n-hexane,
but the amount of adsorption of n-hexane ZSM*5 is
generally greater than water.
Easy to coke
ZSM*5 V-shaped aperture effective, pore size and
bending, preventing a large condensate formation and
accumulation. Meanwhile, ZSM*5 framework is no greater
than the bore of the cavity (cage) exist, so limiting
the formation of large molecules from the secondary
condensation reactions. So that the possibility of
ZSM*5 catalyst coke is reduced. ZSM*5 for an alkyl
aromatics into the tunnel barrier is formed, and thus
the reaction process it can not continue to react in
smaller pores, the final condensation formed coke.
ZSM*5 so much slower than the rate of coke deposition
and Y-type mordenite, difference of almost two orders
of magnitude. Capacity of ZSM*5 zeolite carbon content
is higher.
Excellent shape-selective selectivity
Zeolite molecular sieve as catalyst, only smaller than
the hole crystal molecules can catalyze the reaction
out of control pore size crystalline zeolite suffering
zeolite catalyst size and shape of reactant and product
molecules showed great selectivity. Pore system of
ZSM*5 zeolite having a **-MR constituted medium size
orifice diameter, it has a good shape-selective
selectivity.
