2.1 thermal stability
Zsm-5 zeolite has high thermal stability.This is made from a skeleton with a structurally stable five-membered ring and a high si/al ratio
Into.For example, the crystal structure of the sample remains unchanged after roasting at 850℃ for 2 hours.It can even withstand 1100℃
The high temperature.So far, zsm-5 is one of the highest known zeolites.So we use it at high temperatures
Cheng is especially suitable.For example, it can be used as a cracking catalyst for hydrocarbon to withstand the high temperature of regeneration catalyst.
2.2 acid resistance
Zsm-5 zeolite has a good acid resistance, it can withstand all kinds of acid except hydrofluoric acid.
2.3 water vapor stability
The studies of Wang, IKai et al. have shown the structure of other zeolites when they are subjected to water vapor and heat
It is generally destroyed, resulting in irreversible inactivation.Mobil USES zsm-5 as methanol conversion (water is the main one)
One of the products) catalyst.This shows that zsm-5 has good stability to water vapor.Partial pressure at 540℃ is
After water vapor treatment of hzsm-5 and HY zeolite in 22mmHg column for 24 hours, the crystallinity of hzsm-5 was about
However, under the same conditions, the skeleton of HY zeolite was almost completely destroyed.
2.4 hydrophobic
Zsm-5 has a high si/al ratio and a small surface charge density.Water, on the other hand, is a more polar molecule, so it's not easy
It was adsorbed by zsm-5.Although the diameter of water molecules is smaller than n-hexane, zsm-5 generally adsorbs n-hexane at a higher rate
In the water
2.5 not easy to accumulate carbon
The effective shape and size of the zsm-5 orifice and the curvature of the orifice prevent the formation and accumulation of large condensates.
At the same time, there is no cavity (cage) larger than the hole in the zsm-5 skeleton, so the large condensation from the side reaction is limited
The formation of molecules.Thus, the possibility of carbon deposition in zsm-5 catalyst is reduced.Zsm-5 pair alkyl aromatics enter the channel shape
It becomes an obstacle, so it can't continue to react in the smaller channel in the reaction process, and finally forms coke by condensation polymerization.so
The carbon deposition rate of zsm-5 is much slower than that of Y type and zeolite, almost two orders of magnitude.Volume of zsm-5 zeolite
It's also high in carbon.
2.6 excellent form selection
With zeolite as catalyst, only molecules smaller than crystal pore can enter and exit the catalytic reaction by boiling
With the control of pore size, zeolite catalyst has a great choice on the size and shape of reactants and product molecules
Sex.Zsm-5 zeolite 10 - ring formation of the channel system with a medium size orifice diameter, so that it has a good shape selection
Selectivity.
