CN1078178C - Preparing method of heteroatomic molecular sieve in extremly thick system - Google Patents

Abstract

A method for preparing heteroatom molecular sieves in an extremely concentrated system belongs to the category of physical chemistry. It is characterized in that the heteroatom silicate gel is obtained by adjusting the pH value of the mixed aqueous solution of sodium silicate and heteroatom salts, and then mixing it with 1,6-hexanediamine, trace water, alkali or Alkali metal salts (may or may not be added) are mixed evenly, sealed, and crystallized at 90-200°C according to the temperature program to obtain Fe-, Cr-, Co-, In-, Mn-heteroatom molecular sieves with ZSM-48 structure and pure silica molecular sieves. The method can effectively reduce the hydrolysis of heteroatoms, reduce environmental pollution, increase the utilization rate of equipment by nearly 4 times, and reduce the product cost by 30%.

Description

Preparation method of heteroatom molecular sieve in extremely concentrated system

The preparation method of the heteroatom molecular sieve in the extremely concentrated system of the present invention belongs to the field of physical chemistry. Specifically, it is a method for synthesizing a heteroatom molecular sieve with a ZSM-48 zeolite structure by using nitrogen-containing organic matter as a template in a wet state system.

The published methods for synthesizing heteroatom molecular sieves are generally hydrothermal crystallization. For the commonly used hydrothermal crystallization method, since trivalent metal heteroatoms (such as Fe, Cr, In, etc.) are hydrolyzed to form insoluble hydroxides or oxides, the heteroatoms are prevented from effectively entering the molecular sieve framework. On the other hand, one of the main problems in the industrialization of the preparation of high-silicon molecular sieves is the high cost and the discharge of a large amount of waste liquid, which causes serious environmental pollution. In order to improve this situation, our research proposed to synthesize heteroatom molecular sieves in non-aqueous system and vapor phase system [1,2]. However, although the mother liquor of the synthetic molecular sieve in the non-aqueous system can be recycled, the cost will be greatly increased due to the large amount of organic matter adhering to the product; in addition, due to the strong volatility of the organic solvent, it will also cause serious environmental pollution. Synthesizing molecular sieves in the vapor phase system is a better method, but the single-pot yield is very low and the equipment utilization rate is low. In addition, there is also a large amount of mother liquor in the vapor phase system. Although it can be recycled, it is difficult to adjust the ratio of raw materials. Therefore, we propose to prepare heteroatom silicate gels from silicate and heteroatom salts, and synthesize heteroatom molecular sieves in an extremely concentrated system.

In order to effectively reduce the hydrolysis of metal heteroatoms and facilitate the entry of heteroatoms into the molecular sieve framework, the present invention proposes to prepare heteroatom silicate gel with silicate and heteroatom salts, so that heteroatoms M exist in the form of Si-O-M bonds, And put forward a method to prepare ZSM-48 heteroatom molecular sieve in extremely concentrated system.

A method for preparing a heteroatom molecular sieve in an extremely concentrated system is characterized in that it is a method for preparing a heteroatom molecular sieve with a ZSM-48 zeolite structure in an extremely concentrated system. It uses nitrogen-containing organic matter as a template, and uses heteroatoms Silicate gel is used as raw material, with a small amount of water as solvent, and the reaction mixture is in a wet state. The preparation process is as follows: the aqueous solution of soluble silicate and heteroatom salt is mixed at a molar ratio of 50≤SiO ₂ /M ₂ O ₃ After uniformity, adjust the pH value to form a gel (gel). The gel is fully washed and dried for use. In the gel, the metal M is a variety of heteroatoms, namely Fe, Cr, Al, Co , Mn, In, heteroatoms and silicon to form Si-OM bonds, by molar ratio (0-8.0) N ₂ O: (50-400) gel: (10-150) 1, 6HDA: (50-300) H ₂ O, where N is an alkali metal cation, mix the heteroatom silicate gel, nitrogen-containing organic template, alkali metal hydroxide and water well, seal it in a high-pressure reactor, and set it at 323-523K according to the procedure Heating crystallization, the crystallization time is 6-35 days, and the crystallization temperature is 323-473K. The product is filtered, washed, and dried for later use. The molar composition of the gel used in the crystallization process is 50≤SiO ₂ /M ₂ O ₃ , the nitrogen-containing organic template used is 1,6-hexamethylenediamine (HDA). The above method for preparing a heteroatom molecular sieve with a ZSM-48 zeolite structure in an extremely concentrated system is characterized in that the alkali metal hydroxide may not be added, and the M heteroatoms may be one type of heteroatom.

The best example of realizing _{the present invention is as follows: Example 1: get silicon aluminum iron (SiO2/(Fe2O3+Al2O3)=700, Fe2O3/Al2O3 = 1 : 1 (} molar ratio) ₎ Dry gel 5.9g, 1,6 hexamethylenediamine (referred to as 1,6HDA) 5.7g, water 5ml, it is fully stirred and mixed evenly, makes the proportioning of reaction mixture be 501,6HDA:100gel:300H ₂ O (mole ratio), then the mixture is sealed in an autoclave lined with a polytetrafluoroethylene pad, under autogenous pressure and static conditions, the product of ZSM-48 zeolite structure can be obtained in 15 days at 433K crystallization, without miscellaneous crystals ( As shown in Figure 1). Example 2: Take 2.94g of ferrosilicon (SiO ₂ /Fe ₂ O ₃ =600 (molar ratio)) xerogel, 2.8g of 1,6HDA, 1.8ml of water, stir and mix it well and seal it in a polystyrene-lined In a high-pressure reaction kettle with vinyl fluoride pad, under autogenous pressure and static conditions, crystallization at 433K for 12 days can obtain ZSM-48 zeolite-structured ferrosilicon heteroatom molecular sieve without miscellaneous crystals. Example 3: Get ferrosilicon (SiO ₂ /Fe ₂ O ₃ =700 (molar ratio)) xerogel 7.9g, 1,6HDA4.6g, water 7ml, after it is fully stirred and mixed, it is sealed in a polytetrafluoroethylene-lined In a high-pressure reactor with ethylene pads, under autogenous pressure and static conditions, aging at 393K for 2 days and crystallization at 428K for 13 days can obtain ZSM-48 zeolite-structured ferrosilicon heteroatom molecular sieve without miscellaneous crystals. Example 4: Take 4.6g of silicon chromium (SiO ₂ /Cr ₂ O ₃ =300 (molar ratio)) xerogel, 1,6HDA 3.6g, water 2.8ml, fully stir and mix it evenly, and seal it on a polystyrene liner. In a high-pressure reaction kettle with vinyl fluoride pad, under autogenous pressure and static conditions, aging at 383K for 2 days and crystallization at 423K for 13 days can obtain ZSM-48 zeolite-structured silicon-chromium heteroatom molecular sieve without miscellaneous crystals. Example 5: Take 11.5 g of silicon aluminum chromium (SiO ₂ /(Cr ₂ O ₃ +Al ₂ O ₃ )=300, Cr ₂ O ₃ /Al ₂ O ₃ =1:1 (molar ratio)) xerogel, 1, 6HDA 9.9g, water 6.9ml, fully stirred and mixed evenly, sealed in a high-pressure reactor lined with polytetrafluoroethylene pad, under autogenous pressure and static conditions, aged at 373K for 2 days, crystallized at 428K for 12 days The product with ZSM-48 zeolite structure can be obtained without miscellaneous crystals. Example 6: Take silicon chromium (SiO ₂ /Cr ₂ O ₃ =500 (molar ratio)) xerogel 10.6g, 1,6HDA 6.2g, water 11.6ml, stir and mix it well and seal it in a polystyrene-lined In a high-pressure reactor with vinyl fluoride pad, under autogenous pressure and static conditions, aging at 383K for 2 days and crystallization at 453K for 8 days can obtain the product of ZSM-48 zeolite structure without miscellaneous crystals. Example 7: Take silicon chromium (SiO ₂ /Cr ₂ O ₃ =50 (molar ratio)) xerogel 10.1g, 1,6HDA 6.2g, water 10.8ml, stir and mix it well and seal it on a polystyrene liner In a high-pressure reaction kettle with a vinyl fluoride pad, under autogenous pressure and static conditions, aging at 383K for 2 days and crystallizing at 433K for 15 days can obtain a product with a ZSM-48 zeolite structure without miscellaneous crystals. Example 8: Take 12.5g of silicon chromium iron (SiO ₂ /(Cr ₂ O ₃ +Fe ₂ O ₃ )=300, Cr ₂ O ₃ /Fe ₂ O ₃ =1:1 (molar ratio)) xerogel, 1, 6.2g of 6HDA, 12.8ml of water, fully stirred and mixed evenly, sealed in a high-pressure reactor lined with a polytetrafluoroethylene pad, aged at 383K for 2 days under autogenous pressure and static conditions, and crystallized at 408K for 30 days The product with ZSM-48 zeolite structure can be obtained without miscellaneous crystals. Example 9: Take 13.7g of silicon indium (SiO ₂ /In ₂ O ₃ =500 (molar ratio)) xerogel, 10.6g of 1,6HDA, and 12.5ml of water, stir and mix them well and seal them in a polystyrene-lined In a high-pressure reaction kettle with a vinyl fluoride pad, under autogenous pressure and static conditions, aging at 373K for 1 day and crystallization at 423K for 15 days can obtain a silicon indium molecular sieve with a ZSM-48 zeolite structure without miscellaneous crystals. Example 10: Take 15.2g of silicon indium (SiO ₂ /In ₂ O ₃ =350 (molar ratio)) xerogel, 10.3g of 1,6HDA, and 15.9ml of water, stir and mix them well and seal them in a polystyrene-lined In a high-pressure reaction kettle with a vinyl fluoride pad, under autogenous pressure and static conditions, aging at 393K for 2 days and crystallization at 443K for 10 days can obtain a silicon indium molecular sieve with a ZSM-48 zeolite structure without miscellaneous crystals. Example 11: Take 6.9g of silicon-cobalt (SiO ₂ /Co ₂ O ₃ =500 (molar ratio)) xerogel, 6.7g of 1,6HDA, 4.1ml of water, stir and mix them well and seal them in a polystyrene-lined In a high-pressure reactor with a vinyl fluoride pad, under autogenous pressure and static conditions, aging at 393K for 2 days and crystallization at 433K for 13 days can obtain a silicon-cobalt molecular sieve with ZSM-48 zeolite structure without miscellaneous crystals. Example 12: Take 2.5g of silicon cobalt (SiO ₂ /Co ₂ O ₃ =700 (molar ratio)) xerogel, 2.1g of 1,6HDA, 0.04g of NaOH, 1.5ml of water, stir and mix them well and seal them in In a high-pressure reactor lined with a polytetrafluoroethylene pad, under autogenous pressure and static conditions, silicon-cobalt molecular sieves with a ZSM-48 zeolite structure can be obtained by crystallization at 423K for 14 days without miscellaneous crystals. Example 13: Take 10.8g of silicomanganese (SiO ₂ /Mn ₂ O ₃ =400 (molar ratio)) xerogel, 8.4g of 1,6HDA, and 6.5ml of water, stir and mix them evenly, and seal them on a polystyrene liner. In a high-pressure reaction kettle with vinyl fluoride pad, under autogeneous pressure and static conditions, crystallization at 433K for 12 days can obtain a silico-manganese molecular sieve with ZSM-48 zeolite structure without miscellaneous crystals. Example 14: Take 5.1g of silicomanganese (SiO ₂ /Mn ₂ O ₃ =600 (molar ratio)) xerogel, 4.8g of 1,6HDA, 0.1g of NaOH, 4.5ml of water, stir and mix them well and seal them in In a high-pressure reactor lined with a polytetrafluoroethylene pad, under autogenous pressure and static conditions, aging at 383K for 2 days and crystallization at 423K for 14 days can obtain a silico-manganese molecular sieve with ZSM-48 zeolite structure without miscellaneous crystals. Example 15: Take 6.8g of pure silicon xerogel, 5.5g of 1,6HDA, and 4.5ml of water, stir and mix it well and seal it in a high-pressure reactor lined with a polytetrafluoroethylene pad, under autogenous pressure and static conditions Under the condition of crystallization at 423K for 18 days, a pure silicon molecular sieve with ZSM-48 zeolite structure can be obtained without any miscellaneous crystals.

Table 1: XRD data of different ZSM-48 heteroatom molecular sieves

                                                        , 

d(A) I/I ₀ d(A) I/I ₀ d(A) I/I ₀

11.734 23.4 11.718 24.5 11.690 19.8

  10.051 22.6 10.140 15.6 10.131 16.7

4.165 63.1 4.174 82.9 4.168 61.2

3.883 100.0 3.889 100.0 3.886 100

3.034 28.9 3.034 19.0 3.034 25.9

2.838 31.4 2.845 15.7 2.841 15.0 (continued)

In-ZSM-48 Cr-ZSM-48 Co-ZSM-48

d(A) I/I ₀ d(A) I/I ₀ d(A) I/I ₀

11.06 19.5 11.729 19.9 11.725 25.8

10.146 12.7 10.059 16.5 10.062 17.8

4.172 88.5 4.167 83.5 4.168 77.5

3.888 100.0 3.883 100.0 3.886 100.0

3.032 17.6 3.030 22.7 3.034 29.5

2.844 16.0 2.839 16.7 2.841 19.3

References: 1. Ruifeng Li, Wenyang Xu and Jingzhong Wang Zeolites, 12(1992) 716. 2. Dong Jinxiang, Zhao Xingguo, Zhou Feng. Journal of Inorganic Chemistry, 1995, No.1.

Description of figures and tables: Figure 1 XRD patterns of heteroatom molecular sieves with ZSM-48 Figure 2 FTIR patterns of different ZSM-48 heteroatom molecular sieves Figure 3 ESR of ferrosilicon and silicon chromium ZSM-48 heteroatom molecular sieves tested in vacuum Chart 1: XRD data of different ZSM-48 heteroatom molecular sieves

Claims (2)

1. the preparation method of hetero-atom molecular-sieve in the extremely dense system, it is characterized in that it being to have the method for the zeolite structured hetero-atom molecular-sieve of ZSM-48 a kind of in extremely dense system, the preparation, it is to be template with the itrogenous organic substance, with the heteroatoms silicate gel is raw material, with the minor amount of water is solvent, reaction mixture is wetting attitude, and its preparation process is:

I. with the aqueous solution of soluble silicate and heteroatoms salt 50≤SiO in molar ratio ₂/ M ₂O ₃After mixing, by regulating the pH value, form gel (gel), this gel is standby after thorough washing, oven dry, and in the gel, metal M is that multiple heteroatoms exists simultaneously, is Fe, Cr, Al, Co, Mn, In, and heteroatoms and silicon form the Si-O-M key.

II. in molar ratio (0-8.0) N ₂O: (50-400) gel: (10-150) 1,6HDA: (50-300) H ₂O, N is an alkali metal cation in the formula, with heteroatoms silicate gel, nitrogenous organic formwork agent, alkali metal hydroxide and water thorough mixing evenly after, be sealed in the autoclave, in 323-523K follow procedure intensification crystallization, crystallization time is 6-35 days, and crystallization temperature is 323-473K, product after filtration, washing, oven dry back be standby, and wherein used gel mole consists of 50≤SiO in the crystallization process ₂/ M ₂O ₃, used nitrogenous organic formwork agent is 1,6-hexanediamine (HDA).

2. have the method for the zeolite structured hetero-atom molecular-sieve of ZSM-48 described the preparation according to claim 1 in extremely dense system, it is characterized in that described alkali metal hydroxide can not add, many kinds of heteroatomss of described M can be a kind of heteroatoms.

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