A method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieve

Abstract

The present invention provides a method for solvent-free synthesis of ZSM-5 molecular sieves assisted by a polymer, and belongs to the technical field of molecular sieve preparation. The synthesis method of the present invention is: a silicon source, an aluminum source, an alkali source and polyvinyl pyrrolidone are mixed and ground to obtain a mixture, and the mixture is sequentially subjected to crystallization reaction, suction filtration and drying to obtain a ZSM-5 molecular sieve. The present invention only needs to add a trace amount of polymer PVP to assist in the synthesis of ZSM-5 zeolite molecular sieves. The present invention avoids the use of seed crystals and expensive organic templates, and the obtained product maintains good crystallinity and purity, has good reactivity, and reduces production costs and environmental pollution, and has huge industrial application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of zeolite molecular sieve preparation, and in particular to a method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieve. Background Art

[0002] ZSM-5 molecular sieve is a high silicon molecular sieve with a three-dimensional double ten-membered ring channel structure, which is widely used in the fields of petroleum catalysis, fine chemicals, ion exchange, adsorption and separation. When the ZSM-5 molecular sieve is synthesized by the solvent-free method, tetrapropylammonium bromide is usually used as an organic template (CN102627287A), or a seed crystal method (CN102992343A) is used to guide the synthesis of ZSM-5 molecular sieve. The organic template is expensive, and roasting is required to remove the organic template during the synthesis process, and a large amount of nitrogen oxide waste gas is also discharged during the roasting process. On this basis, the seed crystal method closely combines organic template-free synthesis with solvent-free synthesis, which has more advantages. The seed crystal method synthesizes ZSM-5 molecular sieves by simple washing and drying to obtain ZSM-5 molecular sieves, which saves energy and is environmentally friendly.

[0003] However, the seed method also requires the addition of seed crystals as a guiding agent, which is not conducive to cost saving. Therefore, how to obtain a method for synthesizing ZSM-5 molecular sieves without solvent at a lower cost, less energy consumption, and almost zero pollution is a technical problem that needs to be solved at present. Summary of the invention

[0004] The purpose of the present invention is to provide a method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieves to solve the technical problems of high cost and high energy consumption of the existing seed crystal method.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieves, comprising the following steps:

[0007] A silicon source, an aluminum source, an alkali source and polyvinyl pyrrolidone are mixed and ground to obtain a mixture, and the mixture is subjected to crystallization reaction, suction filtration and drying in sequence to obtain a ZSM-5 molecular sieve.

[0008] Furthermore, the silicon source comprises one or more of white carbon black, solid silica gel and sodium silicate.

[0009] Furthermore, the aluminum source comprises one or more of aluminum sulfate, aluminum nitrate, sodium aluminate and boehmite.

[0010] Furthermore, the alkali source comprises one or more of sodium silicate, sodium hydroxide and potassium hydroxide.

[0011] Furthermore, the molecular weight of the polyvinyl pyrrolidone is 8,000 to 1,300,000.

[0012] Furthermore, the molar ratio of silicon element, aluminum element, sodium element and polyvinyl pyrrolidone in the mixture is 1: 0.02-0.1: 0.1-0.6: 0.0001-0.3.

[0013] Furthermore, the molar ratio of silicon element, aluminum element, potassium element and polyvinyl pyrrolidone in the mixture is 1: 0.02-0.1: 0.1-0.6: 0.0001-0.3.

[0014] Furthermore, the temperature of the crystallization reaction is 120 to 200° C., and the time of the crystallization reaction is 12 to 48 hours.

[0015] Beneficial effects of the present invention:

[0016] 1. Compared with the prior art, only a trace amount of polymer PVP is used in the entire synthesis process, and the obtained product maintains good crystallinity and purity. The polymer PVP can be removed in the washing step and has good catalytic reaction activity.

[0017] 2. Compared with the existing technology, the synthesis operation is simple and avoids the use of organic templates and crystal seeds, which is of great significance in the field of actual chemical production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the XRD spectrum of the ZSM-5 molecular sieve in Example 1;

[0019] Figure 2 , Figure 3 The SEM images of the ZSM-5 molecular sieve in Example 1 at different magnifications are shown;

[0020] Figure 4 This is the N2 adsorption-desorption isotherm of the ZSM-5 molecular sieve in Example 1. DETAILED DESCRIPTION

[0021] The present invention provides a method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieves, comprising the following steps:

[0022] A silicon source, an aluminum source, an alkali source and polyvinyl pyrrolidone are mixed and ground to obtain a mixture, and the mixture is subjected to crystallization reaction, suction filtration and drying in sequence to obtain a ZSM-5 molecular sieve.

[0023] In the present invention, the silicon source comprises one or more of white carbon black, solid silica gel and sodium silicate, preferably solid silica gel and / or sodium silicate.

[0024] In the present invention, the aluminum source comprises one or more of aluminum sulfate, aluminum nitrate, sodium aluminate and boehmite, preferably one or more of aluminum sulfate, sodium aluminate and boehmite, and more preferably aluminum sulfate.

[0025] In the present invention, the alkali source comprises one or more of sodium silicate, sodium hydroxide and potassium hydroxide, preferably sodium hydroxide and / or potassium hydroxide, and more preferably sodium hydroxide.

[0026] In the present invention, the molecular weight of the polyvinyl pyrrolidone is 8,000 to 1,300,000, preferably 9,000 to 1,100,000, more preferably 15,000 to 550,000, and even more preferably 20,000 to 400,000.

[0027] In the present invention, the molar ratio of silicon, aluminum, sodium and polyvinyl pyrrolidone in the mixture is 1: 0.02-0.1: 0.1-0.6: 0.0001-0.3, preferably 1: 0.05-0.08: 0.2-0.5: 0.001-0.2, and more preferably 1: 0.06-0.07: 0.3-0.4: 0.01-0.1.

[0028] In the present invention, the molar ratio of silicon, aluminum, potassium and polyvinyl pyrrolidone in the mixture is 1: 0.02-0.1: 0.1-0.6: 0.0001-0.3, preferably 1: 0.05-0.08: 0.2-0.5: 0.001-0.2, and more preferably 1: 0.06-0.07: 0.3-0.4: 0.01-0.1.

[0029] In the present invention, the temperature of the crystallization reaction is 120-200° C., preferably 140-180° C., and more preferably 150-170° C.; the time of the crystallization reaction is 12-48 h, preferably 15-40 h, and more preferably 24-36 h.

[0030] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0031] Example 1

[0032] 1.15g solid silica gel (silicon dioxide content greater than 98wt%), 1.3g sodium silicate nonahydrate, 0.31g aluminum sulfate 18hydrate, and 0.014g polymer PVP (molecular weight 8000) were ground in a mortar, and then the reaction raw materials were added to a polytetrafluoroethylene stainless steel reactor, and crystallized at 180°C for 24h to completely crystallize, and the product was washed, filtered, and dried to obtain the product. The molar ratio of the reaction raw materials is as follows:

[0033] 1SiO2: 0.02Al2O3: 0.18Na2O: 2.1H2O: 0.005PVP.

[0034] Example 2

[0035] 1.15g solid silica gel (silicon dioxide content greater than 98wt%), 1.3g sodium silicate nonahydrate, 0.31g aluminum sulfate 18hydrate, and 0.014g polymer PVP (molecular weight 220000) were ground in a mortar, and then the reaction raw materials were added to a polytetrafluoroethylene stainless steel reactor, and crystallized at 200°C for 24h to completely crystallize, and the product was washed, filtered, and dried to obtain the product. The molar ratio of the reaction raw materials is as follows:

[0036] 1SiO2: 0.02Al2O3: 0.18Na2O: 2.1H2O: 0.005PVP.

[0037] Example 3

[0038] 2.1g SiO2·3H2O, 0.11g sodium aluminate, 0.1g sodium hydroxide, and 0.01g polymer PVP (molecular weight 220000) were ground in a mortar, and then the reaction raw materials were added to a polytetrafluoroethylene stainless steel reactor, and crystallized at 180°C for 24h to completely crystallize. The product was washed, filtered, and dried to obtain the product. The molar ratio of the reaction raw materials is as follows:

[0039] 1SiO2: 0.025Al2O3: 0.104Na2O: 3H2O: 0.005PVP.

[0040] Example 4

[0041] 2.1g SiO2·3H2O, 0.11g sodium aluminate, 0.1g sodium hydroxide, and 0.1g polymer PVP (molecular weight 220000) were ground in a mortar, and then the reaction raw materials were added to a polytetrafluoroethylene stainless steel reactor, and crystallized at 180°C for 24h to completely crystallize. The product was washed, filtered, and dried to obtain the product. The molar ratio of the reaction raw materials is as follows:

[0042] 1SiO2: 0.025Al2O3: 0.104Na2O: 3H2O: 0.05PVP.

[0043] Example 5

[0044] 2.1g SiO2·3H2O, 0.088g boehmite, 0.2g potassium hydroxide, and 0.01g polymer PVP (molecular weight 1300000) were ground in a mortar, and then the raw materials were added into a polytetrafluoroethylene stainless steel reactor, and crystallized at 180°C for 24h to completely crystallize, and the product was washed, filtered, and dried to obtain the product. The molar ratio of the raw materials is as follows:

[0045] 1SiO2: 0.033Al2O3: 0.14K2O: 3H2O: 0.005PVP.

[0046] The XRD spectrum, SEM photo, and N2 adsorption-desorption isotherms of the ZSM-5 molecular sieve in Example 1 are as follows: Figure 1 , Figure 2 and 3 , Figure 4 As shown. Figure 1 The XRD spectrum of the product shows that it has characteristic diffraction peaks consistent with ZSM-5 zeolite and good crystallinity; Figure 2 and Figure 3 From the SEM photos, we can see that the crystals of the synthesized product are hexagonal blocks with a particle size range of 5 to 8 μm, and the crystals are completely crystallized, indicating that the product has good crystallinity. Figure 4 The adsorption-desorption isotherm curves show typical type I adsorption, corresponding to the micropores of ZSM-5 molecular sieve, proving that the product has open micropore channels and a large specific surface area.

[0047] The effects of the molecular sieves obtained in other embodiments are equivalent to that in embodiment 1.

[0048] As can be seen from the above examples, the present invention provides a method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieves. The present invention only needs to add a trace amount of polymer PVP to assist in the synthesis of ZSM-5 zeolite molecular sieves. The present invention avoids the use of seed crystals and expensive organic templates, while the prepared product maintains good crystallinity and purity, has good reactivity, and reduces production costs and environmental pollution, and has great industrial application prospects.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieves, characterized in that: The following steps are involved: A silicon source, an aluminum source, an alkali source and polyvinyl pyrrolidone are mixed and ground to obtain a mixture, and the mixture is sequentially subjected to crystallization reaction, suction filtration and drying to obtain a ZSM-5 molecular sieve; The molar ratio of silicon element, aluminum element, sodium element and polyvinyl pyrrolidone in the mixture is 1:0.02-0.1:0.1-0.6:0.0001-0.01; The molar ratio of silicon element, aluminum element, potassium element and polyvinyl pyrrolidone in the mixture is 1:0.02-0.1:0.1-0.6:0.0001-0.

01.

2. The method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieve according to claim 1, characterized in that: The silicon source comprises one or more of white carbon black, solid silica gel and sodium silicate.

3. The method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieve according to claim 1 or 2, characterized in that: The aluminum source comprises one or more of aluminum sulfate, aluminum nitrate, sodium aluminate and boehmite.

4. The method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieve according to claim 3, characterized in that: The alkali source comprises one or more of sodium silicate, sodium hydroxide and potassium hydroxide.

5. The method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieve according to claim 1, 2 or 4, characterized in that: The molecular weight of the polyvinyl pyrrolidone is 8000-1300000.

6. The method for polymer-assisted solvent-free synthesis of ZSM-5 molecular sieve according to claim 1 or 4, characterized in that: The temperature of the crystallization reaction is 120-200° C., and the time of the crystallization reaction is 12-48 hours.

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