SAPO-34 from Dalian Haixin Chemical is formed by introducing Si into the Aluminum phosphate framework with PO2+、AlO2+ and SiO2 tetrahedron, electronegativity, surface proton acidic center and exchangeable cations. The silicon aluminum phosphate zeolite with different topological structure and acidity can be prepared by changing the synthesis conditions and the Si content.
SAPO-34 is widely used in catalytic conversion of light alkanes to light alkenes, C4~C8 linear alkenes/alkanes cracking to light alkenes, purification of automobile exhaust, catalyst carrier, membrane separation materials and luminous material because of its three-dimensional cross channel, the eight membered ring orifice diameter and medium acid center.
SAPO-34 from Dalian Haixin Chemical has been successfully used in catalytic field, treatment of the automobile exhaust, gas membrane separation materials and functional materials.
Main applications of SAPO-34 are as follows:
1, Application in conversion of low carbons to light alkenes
(1) Methanol to light alkenes/propene
The MTO process with ethylene and propene as the target product and FMTP process with propene as the target product are developed based on SAPO-34. SAPO-34 shows higher catalytic activity and selectivity for the MTO reaction with proper proton acidity, larger specific surface area, better adsorption capacity and better thermal stability and hydrothermal stability, and it is suitable to produce small moleculars such as ethylene, propene and n-alkanes while the formation of isoalkane and aromatics can be strictly limited. The selectivity for C2=~C4= can be up to 90% when methanol is catalyzed using SAPO-34.
(2) Chloromethane to light alkene
According to the result from R&D center of Dalian Haixin Chemical, under the same reaction condition, the reaction of halomethane to light alkene has familiar rules with MTO reaction in the reaction induction period, product distribution and carbon pool of hydrocarbon species distribution in catalyst. From CH3Cl and CH3Br to light alkenes reaction will have better selectivity and yield when using SAPO-34 than using other zeolite catalyst.
(3) Ethylene to propene
The selectivity for propene depends on the channel size and acidity of zeolite. SAPO-34 has higher propene selectivity, higher 1-butene and 2- butane selectivity and lower isobutene selectivity. It is because the eight membered ring orifice diameter of SAPO-34 is close to the dynamic diameters of ethylene, propene and 1-butene, which is good for reactant and product diffusing in and out of the channel. The moderate proton acidity and the shape selectivity make SAPO-34 have a high yield of propene.
2, Application in cracking reaction of heavy hydrocarbons
(1) Olefin catalytic cracking to propylene
Using SAPO-34 as catalyst, C5 above products are restricted because of its appropriate pore size, and the selectivity for propylene in active time is very high, the yield of propylene is higher than that of other molecular sieve catalyst, and the conversion rate is higher as well.
(2) Heavy hydrocarbons catalytic cracking to propylene
SAPO-3 has certain catalytic activity and good selectivity for light alkenes in the catalytic cracking of hydrocarbon fuels. SAPO-34 has better cracking activity and higher selectivity for propene because of its proper acidity and good shape selectivity.
3, Application in alkenes to light alkenes
(1)Oxidative dehydrogenation of ethane
(2)Dehydrogenation of propane
(3)Dehydrogenation of butane
Dehydrogenation reaction is carried out on the higher acid catalytic center, but the cracking reaction is promoted at the same time. Using SAPO-34 as the metal carrier can avoid cracking reaction, and is good for alkane dehydrogenation reaction: the metal can take H out of alkanes to form intermediates, and in the weak acid activity center, the light alkenes can be formed by the intermediates.
4, Application in zeolitic membrane
(1) Selective separation of CO2/CH4
Gas Separation Membrane is a process of separating the gas mixture by the different adsorption capacity of each component on the surface of polymer or zeolitic membrane and the difference of dissolution - diffusion in the membrane.
Main applications of gas membrane separation of CO2/CH4 are as follows:
(a) As the pressure keeps decreasing during oil exploration, inert gas (CO2) is injected to improve the oil recovery rate, which is called Enhanced Oil Recovery (EOR). It is very essential to separate and recover CO2 from the oil and hydrocarbon gas.
(b) Natural gas contains large amounts of acid gas and water vapor, and removing the acid gas can improve the calorific value of natural gas and reduce the pipeline corrosion. Because the natural gas is generally in a high pressure state, the membrane separation method can be used to save power.
(c) Bio gas, generally contains 50%-70% methane gas, can be developed to reduce the usage of fossil fuels.
(2) Purification of H2
SAPO-34 membrane can separate CH4/H2 because of its fast H2 diffusion rate, the familiar size of channel to CH4 molecular size and lower diffusion capacity than H2. The selectivity of H2 and CH4 has a maximum value as the temperature change, and decreases slightly as the pressure and the CH4 concentration in the raw material increases.
5, Application in treatment of NOX
NOX is one of the main polutant in the air, which can cause acid rain and photochemical polution. It comes mainly from automobile exhaust. Cu-SAPO-34 is a NOX reduction catalyst with good applications. It has better thermal stability, longer lifetime and can keep higher catalytic activity even in moisture condition.
6, Application in material fields
Zinc Oxide is a kind of multi-functional material, mainly used in reflective coating, gas sensor, electronic and optical instruments and voltage dependent resistor. With the microporous SAPO-34 as the main body, nano ZnO particles can be formed in the smaller chabazite cage by the method of zinc salt impregnation burning. The ZnO particle size is smaller and the quantum size effect is more obvious, because the chabazaite cage of SAPO-34 is smaller that that of Y-zeolite and the SiO2 channel.