High Thermal Stability ZSM-5 Zeolite With Stable Five Membered Ring
ZSM-5 zeolite properties
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 850 ℃ After 2
hours, the crystal structure unchanged. Even can withstand high
temperature of 1100 ℃. 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.
ZSM-5 zeolite has good acid resistance, it is resistant to various
acids except hydrofluoric acid.
Mole Ratio: 15-1000
Nominal Cation Form: Ammonium/Hydrogen
|SiO2/Al2O3Mole Ratio||Nominal Cation Form||Na2O Weight %||Surface Area, m2/g|
Na2O Weight %: 0.05
Surface Area, m2/g: 340
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. 540 ℃ lower partial pressure of 22mmHg steaming column
and HY zeolite HZSM-5 after 24 hours, a crystallinity of HZSM-5 and
about 70 percent of fresh catalyst, but under the same conditions,
HY zeolite skeleton almost completely damage.
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 10-MR constituted medium size
orifice diameter, it has a good shape-selective selectivity.