Zeolite molecular sieve How to prepare honeycomb

zeolite honeycomb As ion exchange materials, adsorbents and catalysts, molecular sieves play an important role in chemical industry, petrochemical industry and other fields. With the continuous development of new material field, electronics, information and other industries, its application scope has jumped out of the traditional industry, such as new profiled molecular sieve adsorbents, catalysts and catalytic distillation elements, gas and liquid separation membranes, gas sensors, nonlinear optical materials, fluorescent materials Low dielectric constant materials and anti-corrosion materials have been applied or have potential application prospects. Therefore, the preparation methods of zeolite molecular sieves have attracted more and more attention.  

The traditional preparation methods of zeolite molecular sieves mainly include hydrothermal method, high-temperature synthesis method, vapor phase system synthesis method, etc. However, with the continuous expansion of the application of combinatorial chemistry technology in the field of materials, in the late 1990s, people combined the concept of combinatorial chemistry with the hydrothermal method of zeolite molecular sieves and established the combinatorial hydrothermal method. The application of combinatorial chemistry technology to the hydrothermal synthesis of zeolite molecular sieves speeds up the screening and optimization of synthesis conditions. In addition, new preparation methods such as vapor phase transfer and dry gel method have also been proposed and applied in practice.

Zeolite molecular sieves were prepared by the combined chemical hydrothermal method, and a combined reactor was designed, that is, 100 small holes were drilled on the circular polytetrafluoroethylene sheet, and then the upper and lower surfaces were clamped with stainless steel sheets to form 100 hydrothermal reactors, and hydrothermal synthetic liquids of different proportions were placed in each reactor. Under certain conditions, zeolite molecular sieves can be synthesized as traditional hydrothermal method. They investigated the four component system of Na2O-Al2O3-SiO2-H2O, compared the difference between traditional hydrothermal method and combined hydrothermal method, and confirmed the efficiency and rapid screening of combined chemistry. On this basis, the scientists improved the combined hydrothermal method, designed a device that is easy to automatically determine by X-ray diffraction, and screened the synthetic formula of TS-1 molecular sieve with this method. The combined chemical hydrothermal method has been applied to the preparation of molecular sieves and the synthesis of inorganic materials, but its application is still limited.

At the same time, the combined chemical hydrothermal method should be used, which has the following characteristics:

(1) Each synthesis should produce as many parallel results as possible;

(2) Reduce the amount of samples in each group;

(3) Increase the degree of automation in the synthesis and characterization process;

(4) The experiment process is fully combined with the computer to improve the experiment efficiency

Gas phase transfer method 2.1 Preparation of molecular sieve powder by gas phase transfer method Gas phase transfer method can be used to prepare zeolite molecular sieves with MFI, FER, MOR and other structures. Zhang et al. synthesized ZnAPO-34 and SAPO-34 molecular sieves by gas phase transfer method, proving that water is an indispensable component in the gas phase synthesis of phosphorus aluminum molecular sieves. Later, some people also synthesized AFI and AEI phosphorus aluminum molecular sieves by gas phase method, which verified the role of water in the synthesis process. When n (P2O5)/n (Al2O3)=1, AlPO4-5 and AlPO4-11 molecular sieves were synthesized with triethylamine and di-n-propylamine and water as templates, respectively.

ZSM-22 zeolite molecular sieve was synthesized by gas phase transfer method. Aluminum tributyl alcohol and aluminum metal were used as aluminum sources respectively. It was found that ZSM-22 zeolite could be successfully synthesized when ethylenediamine and water were used as the liquid phase. 2.2 Gas phase transfer method is used for molecular sieve molding. The unsupported ZSM-22 molecular sieve membrane is prepared by gas phase transfer method. The molecular sieve synthetic liquid is evaporated to dry water to form dry glue, and then the dry glue is pressed to form a membrane under a certain pressure, and reacts under the action of ethylene diamine (EDA) and water vapor. The obtained zeolite membrane has high conversion and selectivity in the isomerization reaction of 1-butene to isobutene. ZSM-5 molecular sieve membrane was prepared on honeycomb ceramics by gas phase method. First, ZSM-5 molecular sieve synthetic liquid without template was prepared, and the pretreated honeycomb ceramics were immersed in the synthetic liquid for 20 minutes. Then, the honeycomb ceramics were taken out and placed in a gas phase reactor. A quantitative amount of n-butylamine and water were added to the bottom of the bus as template, The honeycomb ceramics loaded with ZSM-5 molecular sieve were prepared under certain conditions, and the load of molecular sieve on the honeycomb ceramics was calculated by weighing method.  

Dry gel method 3.1 Preparation of molecular sieve powder by dry gel method The dry gel method can be used to synthesize AlPO4-5, AlPO4-11, SAPO-5 and SAPO-11 aluminophosphate molecular sieves. When [Al] - SSZ-31 molecular sieve was prepared by dry gel method, under the same synthetic conditions, different n (Na2O)/n (SiO2) had a significant effect on the synthetic product. When n (Na2O)/n (SiO2) is 0.05~0.12, pure [Al] - SSZ-31 molecular sieve can be formed; When n (Na2O)/n (SiO2) decreases, pure MFI molecular sieve is formed; When n (Na2O)/n (SiO2) increases, BEA molecular sieve is formed. With the same dry rubber component, molecular sieves with different structures were obtained under different synthesis conditions. When the dry rubber reacted at 448K for 36h, molecular sieves with MFI structure were obtained; Reaction at 423K for 46h to obtain molecular sieves with BEA structure; After reaction at 423K for 48h, then heating up to 448K and continuing reaction for 12h, [Al] - SSZ-31 molecular sieve was obtained. Bhaumik et al. synthesized Si-NU-1 molecular sieve and Ti-NU-1 molecular sieve without sodium and aluminum by dry gel method. In the preparation, seed crystal or accelerator is not needed, and a small amount of organic template (tetramethyl ammonium hydroxide) is used. 3.2 Dry glue method is used for molecular sieve molding. In molecular sieve molding, adhesive free ZSM-5 spherical particles are prepared by dry glue method. A certain amount of silicon source, aluminum source, alkali metal hydroxide, organic template agent and deionized water are fully mixed and dried to form dry glue, and then amorphous dry glue is pressed and molded under a certain pressure (0.01~1MPa), ZSM-5 zeolite was obtained by reacting in steam for a certain time, and the obtained zeolite has the same shape as that before synthesis. The binder free mordenite and ZSM-11 spherical particles were prepared by the same method. Later, on the basis of preparing nano zeolite molecular sieve by dry gel method, hollow zeolite molecular sieve pellets were also prepared. First, molecular sieve crystals with a particle size of about 20nm were prepared, and then ultrasonic treatment was carried out in the ethanol solution of ammonia for a period of time to obtain self-assembled hollow zeolite molecular sieve spherical particles with a diameter of 100~300nm and a wall thickness of about 20nm.