mo/hzsm-5 catalyst, preparation method and application thereof
A catalyst and template technology, applied in the field of catalysis, can solve the problems affecting the mechanical strength and stability of the catalyst, the decrease of crystallinity, the loss of Mo species, etc., to achieve good catalytic activity and stability, promote efficient generation, and improve dispersion. Effect
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Embodiment 1
[0026] Weigh 0.72g of molybdenum acetylacetonate, 12.5g of tetraethyl orthosilicate and 0.25g of aluminum isopropoxide, and add them into a beaker filled with a mixed organic solvent of 20mL of isopropanol and 20mL of toluene. Keep stirring in a water bath at 25°C for 3 hours. After all the materials are completely dissolved and fully mixed, a clear solution I is obtained; weigh 8g of tetrapropylammonium hydroxide, 17g of water and 10mL of isopropanol, mix and stir to form a uniform solution II.
[0027] Under continuous stirring conditions, use a peristaltic pump to slowly add solution II to solution I dropwise to configure a HZSM-5 molecular sieve synthesis solution, in which the molar ratio of silicon source, aluminum source, template agent, and water is 1:0.02:0.16:24. After continuing to stir for 0.5h, the temperature of the water bath was raised to 40-50°C, and the synthetic solution gradually turned into a transparent gel. After aging and natural air-drying, the xerogel ...
Embodiment 2
[0033] The synchrotron radiation method was used to characterize and analyze the Mo species placement and coordination states of catalysts A and B. figure 1 , figure 2 Catalyst A and catalyst Mo species L in the total electron (TEY) and fluorescence (FY) collection modes, respectively 3 -Edge near-edge absorption rate (XANES) changes. Through two different acquisition methods of TEY and FY, the coordination information of Mo species located in different regions of the bulk phase and the outer surface of the molecular sieve can be obtained.
[0034] Depend on figure 1 It can be seen that MoO with a typical hexacoordinated octahedral structure 3 Compared with the standard sample, both the four-coordinated Mo species and the hexa-coordinated Mo species exist on the outer surface of the catalyst A of Example 1 and the catalyst B of Comparative Example 1. In the normalized spectrogram, it can be seen from the peak intensity difference The content of Mo species on the outer sur...
Embodiment 3
[0037] Before carrying out the oxygen-free dehydrogenation aromatization of methane, the Mo / HZSM-5 catalysts prepared in Example 1 and Comparative Example 1 were pressed into tablets, crushed, and sieved into 20-60 meshes. Weigh 0.6g of catalyst A or catalyst B and load it into a stainless steel fixed-bed continuous flow reactor with an inner diameter of 7mm, and the ratio of bed height to diameter is 4. The reaction pressure is 1atm, the temperature of the catalyst is raised to 750°C in a He atmosphere of 30ml / min, and after stabilizing at this temperature for 30min, switch to 60ml / min raw material gas to start the reaction, and the space velocity is 6000ml / g cat h. Using the method of adding nitrogen to the feed gas as an internal standard (CH 4 / N 2 =9), the product is introduced into two gas chromatographs equipped with thermal conductivity detector and hydrogen flame detector respectively by two six-way valves and carried out on-line analysis, to investigate the convers...
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