CN111137903A

CN111137903A - ECNU-25 molecular sieve and preparation method and application thereof

Info

Publication number: CN111137903A
Application number: CN201911363481.1A
Authority: CN
Inventors: 吴鹏; 张景岩; 徐浩; 季澎; 蒋金刚; 关业军; 吴海虹; 何鸣元
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2020-05-12
Anticipated expiration: 2039-12-26
Also published as: CN111137903B

Abstract

The invention discloses an ECNU-25 molecular sieve and a preparation method and application thereof, which are characterized in that silicon dioxide is used as a first oxide, boron oxide is used as a second oxide, aluminum oxide, iron oxide, gallium oxide, titanium oxide, tin oxide, rare earth oxide, indium oxide or vanadium oxide is used as a third oxide, and when hetero atoms such as Al, Ti, Sn and the like are introduced into a framework of the ECNU-25 molecular sieve, the ECNU-25 molecular sieve can be used for preparing redox catalysts with different catalytic centers and can be well applied to the selective catalytic reduction reaction for preparing hydrocarbon and alcohol compounds. Compared with the prior art, the invention has an original structure, is discovered for the first time, can enrich the types of the molecular sieve, and provides possibility for developing a novel environment-friendly catalytic system by introducing Al, Ti, Sn and other catalytic centers into the framework of the molecular sieve to construct a solid acid catalyst or a redox catalyst based on the novel pore channel structure of the molecular sieve.

Description

ECNU-25 molecular sieve and preparation method and application thereof

Technical Field

The invention relates to the technical field of molecular sieves, in particular to a newly discovered ECNU-25 molecular sieve which has beneficial properties and a novel structure, and a preparation method and application thereof.

Background

The molecular sieve material has a uniform and regular pore structure, wide acid strength distribution, rich acid content and excellent hydrothermal stability, and is widely applied to the fields of catalysis, adsorption separation, ion exchange and the like. With the large consumption of non-renewable resources and the pollution of the waste gas discharged in the using process to the environment, the development of a molecular sieve material with a novel pore channel structure for solving the problems becomes a problem to be solved urgently. Scientists have studied molecular sieves for many years and have identified that molecular sieves are crystals of multi-dimensional structure with regular pores formed by the connection of silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron through oxygen bridges. The discovery that molecular sieves with the same structure can be successfully synthesized by simulating the existence environment of some natural zeolites, and that some heteroatoms can participate in the construction of the molecular sieve framework in the synthesis process of the molecular sieve enables the synthesis and application of the molecular sieve to be greatly developed. For example, B, Ge, Be and the like can well promote the crystallization of the molecular sieve, thereby obtaining more molecular sieves with novel structures or greatly shortening the synthesis period; for example, Ti, Sn, Fe, Cu, Zr and the like are introduced into the framework in the synthesis process of the molecular sieve to be used as a catalytic active center to create a novel catalytic material and construct a high-efficiency green catalytic system. Boric acid can be used as a boron source to provide boron atoms for the framework, and can also be used as a mineralizer to promote the crystallization of the molecular sieve framework. For example, the Ti-MWW molecular sieve cannot be directly synthesized in a hydrothermal system, but the [ Ti, B ] -MWW molecular sieve can be obtained in a silicon-boron system through hydrothermal synthesis with the aid of boric acid. In addition, for the molecular sieve which is difficult to synthesize with high silicon-aluminum ratio in the prior art, a small amount of Al can be introduced into a silicon-boron system to prepare the molecular sieve with high silicon-aluminum ratio. Therefore, the B element occupies a very important position in the synthesis process of the novel molecular sieve.

Disclosure of Invention

The invention aims to provide an ECNU-25 molecular sieve and a preparation method and application thereof, wherein silicon dioxide is used as a first oxide, boron oxide is used as a second oxide, aluminum oxide, iron oxide, gallium oxide, titanium oxide, tin oxide, rare earth oxide, indium oxide or vanadium oxide is used as a third oxide, the molar ratio of the first oxide to the second oxide is 0.5-30, the molar ratio of the first oxide to the third oxide is more than 10 to form the molecular sieve with the structure shown by the formula of 'first oxide and second oxide' or 'first oxide, second oxide and third oxide', the molecular sieve is confirmed to have an original structure and a novel pore channel structure by an XRD spectrogram, and when heteroatoms such as Al, Ti, Sn and the like are introduced into a framework of the molecular sieve, the molecular sieve can be used for preparing oxidation-reduction catalysts with different catalytic centers and can be well applied to selective catalytic reduction reaction for preparing hydrocarbon and alcohol compounds, provides possibility for discovering and enriching molecular sieve types for the first time and providing an environment-friendly catalytic system.

The specific technical scheme for realizing the aim of the invention is that the ECNU-25 molecular sieve is characterized in that the molecular sieve has a chemical composition represented by a formula of 'first oxide and second oxide' or 'first oxide and second oxide and third oxide', and an XRD diffraction pattern of the molecular sieve has X-rays (Cu-K α,

) Diffraction line:

table 1: structural data table of X-ray diffraction of ECNU-25 molecular sieves

Wherein: (a) is +/-0.30 degrees; the diffraction peak intensity w is less than 20 (weak), m is 20-40 (medium), s is 40-70 (strong), and vs is more than 70 (very strong).

The first type of oxide is silicon oxide; the second oxide is boron oxide; the third oxide is one or the mixture of more than two of aluminum oxide, ferric oxide, gallium oxide, titanium oxide, tin oxide, rare earth oxide, indium oxide or vanadium oxide; the molar ratio of the first oxide to the second oxide is 0.5-30, and the molar ratio of the first oxide to the third oxide is more than 10.

The preparation method of the ECNU-25 molecular sieve is characterized in that the ECNU-25 molecular sieve is prepared by the following steps:

mixing a first oxide source (calculated as a first oxide) with a second oxide source (calculated as a second oxide), a third oxide source (calculated as a third oxide), an organic template, water and a seed crystal (calculated as a first oxide) according to a molar ratio of 1: 0.02-2: 0-0.02: 0.1-1.0: 10-80, adding 1-10 wt.% of a silicon-boron molecular sieve with a CHA structure as the seed crystal, aging at 35-80 ℃ for 1-10 hours, then crystallizing at 110-180 ℃ for 10-360 hours, filtering, washing, drying, and roasting the crystallized product to obtain a synthesized ECNU-25 molecular sieve having an exemplary chemical composition shown by the formula "first oxide, second oxide, third oxide", the exemplary chemical composition actually representing a framework chemical composition of the ECNU-25 molecular sieve, wherein when the molecular sieve exists in a synthesized state, X-ray (Cu-K α - α) shown in Table 1,

) Diffraction characteristics:

TABLE 1 structural data Table for X-ray diffraction of ECNU-25 molecular sieves

The molecular sieve has an X-ray pattern when present in the calcined state as shown in table 2 below (Cu-K α,

) Diffraction-characterized structure:

TABLE 2 structural data Table for X-ray diffraction of ECNU-25 molecular sieves

Wherein: (a) is +/-0.30 degrees; the diffraction peak intensity w is less than 20 (weak), m is 20-40 (moderate), s is 40-70 (strong), vs is more than 70 (very strong)

The organic template agent is a compound with the following structural formula A or quaternary ammonium salt and quaternary ammonium base thereof:

wherein: r₁Being alkyl radicals C of different carbon chain numbers_1～6Preferably alkyl C_1～3；R₂Being alkyl radicals C of different carbon chain numbers_1～6Preferably alkyl C_3～6The counter anion of the quaternary nitrogen structure may be a halogen ion or a hydroxide ion, but is not limited thereto.

The ECNU-25 molecular sieve is a membrane product in a powdery, granular or geometric shape in a roasting state.

The application of ECNU-25 molecular sieve is characterized by that the main skeleton composition of said molecular sieve is expressed by anhydrous form of oxide as SiO₂-B₂O₃-Al₂O₃The catalyst is an active component of a selective catalytic reduction catalyst for preparing hydrocarbon compounds and nitrogen oxides; when its main skeleton composition is represented by the anhydrous form of the oxide as SiO₂-B₂O₃-TiO₂When the catalyst is an active component of the catalyst for preparing the hydrocarbon oxygen-containing compound; when its main skeleton composition is represented by the anhydrous form of the oxide as SiO₂-B₂O₃-SnO₂The catalyst is an active component of the catalyst for preparing the alcohol compound.

In conclusion, when the framework contains heteroatoms such as Al, Ti, Sn and the like, materials with different catalytic centers can be prepared and can be well applied, and the possibility is provided for developing a novel environment-friendly catalytic system. Compared with the prior art, the invention has an original structure and is found for the first time, based on the novel pore channel structure of the molecular sieve, when hetero atoms such as Al, Ti, Sn and the like are introduced into the framework of the molecular sieve, the invention can prepare redox catalysts with different catalytic centers, can be well applied to the selective catalytic reduction reaction for preparing hydrocarbon and alcohol compounds, can enrich the types of the molecular sieve, and provides possibility for an environment-friendly catalytic system.

Drawings

FIG. 1 is an X-ray diffraction pattern of ECNU-25 prepared in example 2;

FIG. 2 is an X-ray diffraction pattern of Al-ECNU-25 prepared in example 3;

FIG. 3 is an X-ray diffraction pattern of Ti-ECNU-25 prepared in example 5;

FIG. 4 is an X-ray diffraction pattern of Sn-ECNU-25 prepared in example 6;

Detailed Description

The preparation of the present invention is further illustrated by the following specific examples.

Example 1

2.11 g of organic template agent N, N, N-trimethyl-1-adamantyl ammonium hydroxide (water content: 75 wt.%) was mixed uniformly with 0.062 g of boric acid, 2.0 g of silica sol (water content: 70 wt.%) and 0.62 g of deionized water, the molar ratio of the materials in the mixed solution was: SiO 2₂/B₂O₃10; organic template agent/SiO₂＝0.25；H₂O/SiO₂Aging the prepared mixed solution at 25 ℃ for 2 hours, crystallizing at 150 ℃ for 6 days, filtering and washing the crystallized product, drying at 80 ℃ to obtain a synthesized B-CHA molecular sieve, roasting at 550 ℃ for 6 hours to obtain a roasted B-CHA molecular sieve, and using the roasted B-CHA molecular sieve as a seed crystal for later use.

Example 2

2.01 g of organic template agent A aqueous quaternary ammonium base solution (R)₁Selecting methyl, R₂Isobutyl alcohol, 83.6 wt.% water) was chosen to be mixed homogeneously with 0.124 g boric acid, 1.0 g silica sol (70 wt.% water), 1.22 g deionized water and 0.003 g seed crystals (B-CHA molecular sieve prepared in example 1)The molar ratio of the materials of the mixed solution is as follows: SiO 2₂/B₂O₃1.25; organic template agent A quaternary ammonium base/SiO₂＝0.5；H₂O/SiO₂And (3) ageing the prepared mixed solution at the temperature of 25 ℃ for 1 hour, then crystallizing at the temperature of 150 ℃ for 6 days, filtering and washing the crystallized product, drying at the temperature of 80 ℃ to obtain a synthesized ECNU-25 molecular sieve, and roasting at the temperature of 550 ℃ for 6 hours to obtain the roasted ECNU-25 molecular sieve.

Referring to fig. 1, the above-described ECNU-25 molecular sieve in the calcined state has an X-ray diffraction pattern (XRD, Cu-K α,

) The characterization is carried out, and the crystallinity is good.

Example 3

1.62 g of organic template agent A aqueous quaternary ammonium base (R)₁Selecting methyl, R₂Isobutyl, 83.6 mass percent of water), 0.10 g of boric acid, 0.01 g of aluminum isopropoxide, 1.0 g of silica sol (70 mass percent of water), 1.52 g of deionized water and 0.008 g of seed crystal (B-CHA molecular sieve prepared in example 1) are selected and uniformly mixed, and the material ratio (molar ratio) of the mixed solution is as follows: SiO 2₂/B₂O₃1.5; organic template agent A quaternary ammonium base/SiO₂＝0.4；SiO₂/Al₂O₃＝50；H₂O/SiO₂And (3) ageing the prepared mixed solution at 25 ℃ for 1 hour, then crystallizing at 150 ℃ for 8 days, filtering and washing the crystallized product, drying at 80 ℃ to obtain a target product, namely the synthetic Al-ECNU-25 molecular sieve, and roasting at 550 ℃ for 6 hours to obtain the roasted Al-ECNU-25 molecular sieve.

Referring to fig. 2, the calcined Al-ECNU-25 zeolite was prepared by X-ray diffraction (XRD, Cu-K α,

) The characterization is carried out, and the crystallinity is good.

Example 4

0.242 g of copper nitrate trihydrate, 5 g of deionized water and 1g of the Al-ECNU-25 molecular sieve prepared in example 2 were mixed uniformly, stirred at 25 ℃ for 12 hours, the reaction solution was filtered, washed and dried at 80 ℃, and the dried product was calcined at 550 ℃ for 6 hours to obtain a calcined Cu-Al-ECNU-25 molecular sieve, the structure of which was consistent with that of the Al-ECNU-25 molecular sieve.

Example 5

2.18 g of organic template agent A aqueous quaternary ammonium base (R)₁Selecting ethyl, R₂Selecting isoamyl (with water content of 78.5 mass percent), 0.077 g of boric acid, 0.017 g of tetrabutyl titanate, 1.0 g of silica sol (with water content of 70 mass percent), 0.24 g of deionized water and 0.006 g of seed crystal (B-CHA molecular sieve prepared in example 1), and uniformly mixing, wherein the material molar ratio of the mixed solution is as follows: SiO 2₂/B₂O₃2.0; organic template agent A quaternary ammonium base/SiO₂＝0.5；SiO₂/TiO₂＝100；H₂O/SiO₂Aging the prepared mixed solution at 25 ℃ for 1 hour, crystallizing at 150 ℃ for 8 days, filtering and washing the product, drying at 80 ℃ to obtain the synthesized Ti-ECNU-25 molecular sieve, and roasting at 550 ℃ for 6 hours to obtain the roasted Ti-ECNU-25 molecular sieve.

Referring to fig. 3, the calcined Al-ECNU-25 zeolite was prepared by X-ray diffraction (XRD, Cu-K α,

) The characterization is carried out, and the crystallinity is good.

Example 6

2.01 g of organic template agent A aqueous quaternary ammonium base solution (R)₁Selecting methyl, R₂Isobutyl (water content 83.6 mass%), 0.10 g boric acid, 0.013 g tin tetrachloride, 1.0 g silica sol (water content 70 mass%), 0.72 g deionized water and 0.0075 g seed crystals (B-CHA molecular sieve prepared in example 1) were chosen and mixed uniformly, the molar ratio of the materials of the mixture was: SiO 2₂/B₂O₃1.5; organic template agent A quaternary ammonium base/SiO₂＝0.5；SiO₂/SnO₂＝100；H₂O/SiO₂Mixing the prepared powder 25 ═ 25Aging the mixed solution at 25 deg.C for 1 hr, crystallizing at 150 deg.C for 10 days, filtering, washing, drying at 80 deg.C to obtain synthesized Sn-ECNU-25 molecular sieve, and calcining at 550 deg.C for 6 hr to obtain calcined Sn-ECNU-25 molecular sieve.

Referring to fig. 4, the calcined Al-ECNU-25 zeolite was prepared by X-ray diffraction (XRD, Cu-K α,

) The characterization is carried out, and the crystallinity is good.

Example 7

The Al-ECNU-25 catalyst prepared in example 3 is applied to the reaction of catalyzing methanol to prepare low carbon olefin (MTO) as follows:

weighing 100mg of Al-ECNU-25 catalyst in a quartz tube with an inner diameter of 6mm for 20mL min^-1N₂Activating at flow rate and 500 deg.C for 1 hr, and introducing sample after the temperature is reduced to 400 deg.C, wherein the methanol feed rate is 0.088mL h^-1The carrier gas is N₂At a flow rate of 20mL min^-1The mass space velocity (WHSV) under the condition is 0.7h^-1After 1 hour of reaction, the product obtained is mainly C₂ ^＝、C₃ ^＝Analysis of the olefin, product was done using a gas chromatograph.

Example 8

The Cu-Al-ECNU-25 catalyst prepared in example 4 was applied to the selective catalytic reduction reaction of nitrogen oxides using ammonia as a reducing agent as follows:

50mg of Cu-Al-ECNU-25 catalyst was weighed into a quartz tube with an inner diameter of 6mm at 500ppm NO, 500ppm NH₃、5％O₂、N₂As an equilibrium gas, the flow rate was 50mL min^-1Mass space velocity (WHSV) of 60000mLg_cat ^-1h^-1Carrying out selective catalytic reduction reaction of nitrogen oxides.

The testing temperature is 100-600 ℃, the analysis of the tail gas is completed by adopting a flue gas analyzer, and the catalyst has a wider temperature window and N in a testing temperature range₂Selectivity toTo more than 95%.

Example 9

The application of the Ti-ECNU-25 catalyst prepared in example 5 above to olefin epoxidation is as follows:

0.10 g of Ti-ECNU-25 molecular sieve catalyst, 10g of acetonitrile solvent and 10mmol of 30 wt% aqueous hydrogen peroxide are sequentially added into an autoclave with a pressure indicator, 2.5MPa ethylene gas is introduced into the autoclave, and the autoclave is placed in a 313K water bath for magnetic stirring reaction for 4 hours. And after the reaction is finished, placing the reaction kettle in an ice water bath for cooling for 5min, then quickly opening the reaction kettle, adding 0.1g of internal standard isopropanol, and measuring the conversion rate of a substrate and the selectivity of a product by using gas chromatography, wherein the selectivity of ethylene oxide can reach more than 85%.

Example 10

The Sn-ECNU-25 catalyst prepared in example 6 above was applied to the hydration reaction of ethylene oxide under the following reaction conditions:

0.10 g of Sn-ECNU-25 molecular sieve catalyst, 10mmol of ethylene oxide and 150mmol of water are sequentially added into a reaction tube, and the reaction tube is placed in a water bath with 313K for magnetic stirring reaction for 28 hours. And after the reaction is finished, placing the reaction tube in an ice water bath for cooling for 5min, then quickly opening the reaction tube, adding 0.1g of internal standard isopropanol, and measuring the conversion rate of a substrate and the selectivity of a product by using gas chromatography, wherein the conversion rate of ethylene oxide can reach more than 70%, and the selectivity of ethylene glycol can reach more than 99%.

The above embodiments are only for further illustration of the present invention and are not intended to limit the present invention, and all equivalent implementations of the present invention should be included in the scope of the claims of the present invention.

Claims

1. An ECNU-25 molecular sieve, characterized in that the molecular sieve is the chemical composition of the formula shown in "first oxide, second oxide" or "first oxide, second oxide, and third type of oxide" , and has the structural data shown in Table 1 below:

Table 1 Structure data table of X-ray diffraction of ECNU-25 molecular sieve

Among them: (a) is ±0.30°; the diffraction peak intensity w is less than 20, m is 20-40, s is 40-70, and vs is greater than 70;

The first oxide is silicon dioxide; the second oxide is boron oxide; the third oxide is aluminum oxide, titanium oxide, tin oxide, iron oxide, gallium oxide, rare earth oxide, indium oxide and vanadium oxide Mixing of one or more of the two; the molar ratio of the first oxide to the second oxide is 0.5 to 30 in terms of oxides, and the molar ratio of the first oxide to the third oxide is in terms of oxides. >10.

2. A preparation method of ECNU-25 molecular sieve according to claim 1, characterized in that the first oxide source, the second oxide source, the organic template agent and the water are 1:0.02～2:0.1～1.0:10 ~80 molar ratio mixing, or first oxide source, second oxide source, third oxide source, organic template agent and water in a molar ratio of 1:0.02~2:0~0.02:0.1~1.0:10~80 Mix, add 1-10wt.% silicon boron molecular sieve with CHA structure as crystal seed, age at 35-80℃ for 1-10 hours, then crystallize at 110-180℃ for 10-360 hours, crystallize The resulting product is filtered, washed, dried, or dried to obtain a synthetic state or a calcined state ECNU-25 molecular sieve by calcination, and the first oxide source is silica sol, fumed silica gel, silicic acid, and tetraalkyl silicate. A mixture of one or more of ester and water glass; the second oxide source is a mixture of one or more of boric acid, borate, borax and diboron trioxide; the third type of oxide is A mixture of one or more of aluminum oxide, iron oxide, titanium oxide, tin oxide, gallium oxide, rare earth oxide, indium oxide and vanadium oxide; the organic template is a compound of the following structural formula A or its quaternary Ammonium salts and quaternary ammonium bases:

Wherein: R ₁ and R ₂ are alkyl groups C _1-6 with different carbon chain numbers.

3. The preparation method of ECNU-25 molecular sieve according to claim 2, characterized in that the calcined ECNU-25 molecular sieve is a geometric molding of powder, granule or strip, clover.

4. the application of the described ECNU-25 molecular sieve of claim 1, it is characterized in that this ECNU-25 molecular sieve is used for the catalytic reaction of alcohols making hydrocarbons, the catalytic reaction of olefin epoxidation, the hydration catalytic reaction of epoxy compound The catalytic elimination reaction with nitrogen oxides, the catalytic reaction of the alcohols to hydrocarbons is the Al-ECNU-25 catalyst with Al atoms introduced into the framework of the molecular sieve, and the catalytic reaction of low-carbon olefins is carried out at a temperature of 400 ° C, and its methanol The feed rate is 0.088mL h ^-1 , the amount of Al-ECNU-25 catalyst used is 50-100mg, and the mass space velocity is 0.7-1.4h ^-1 ; the catalytic reaction of the olefin epoxidation is introduced into the framework of the molecular sieve. The Ti-ECNU-25 catalyst of Ti atom performs selective oxidation reaction, the oxidant is hydrogen peroxide, and the molar ratio of the Ti-ECNU-25 molecular sieve to olefin is 0.03-0.3; the hydration catalytic reaction of the epoxy compound is a molecular sieve catalyst. The Sn-ECNU-25 catalyst with Sn atoms introduced into the skeleton is used for the preparation of alcohol compounds, and the molar ratio of the Sn-ECNU-25 catalyst to the olefin is 0.02 to 0.2; the catalytic elimination of nitrogen oxides is ECNU-25 molecular sieve and After the combination of copper, iron or cobalt transition metals, the nitrogen oxides in the exhaust gas are reduced to harmless products. The reaction temperature of the catalytic elimination is 100～600℃, and the components of the reaction gas are 500ppm NO, 500ppm NH ₃ and 5% O ₂ , N ₂ as equilibrium gas, flow rate is 50mL min ^-1 , Al-ECNU-25 catalyst usage is 50～100mg, mass space velocity (WHSV) is 30000～60000mLg _cat ^-1 h ^-1 .