CN1088408C - Process for modifying Ti-Si molecular sieve - Google Patents

Abstract

The invention provides a method for modifying titanium-silicon molecular sieve (TS-1). The method comprises uniformly mixing the synthesized TS-1 molecular sieve, acidic compound and water, and reacting at 5-95°C for 5 minutes to 6 Hours, acid-treated TS-1 molecular sieves were obtained; the obtained acid-treated TS-1 molecular sieves, organic bases and water were mixed evenly, and reacted in a sealed reaction kettle at a temperature of 120-200°C and autogenous pressure for 2 hours to 8 days, wherein said organic base is aliphatic amines, alcohol amines or quaternary ammonium base compounds; the resulting product is filtered, washed and dried. The TS-1 molecular sieve obtained by the method of the invention reduces the ineffective decomposition of the oxidant due to the removal of titanium outside the skeleton in the pores of the molecular sieve, so that the catalytic oxidation activity is significantly improved compared with the prior art, and at the same time, it has better catalytic activity stability.

Description

A kind of modification method of titanium silicon molecular sieve

The invention relates to a method for modifying a titanium-silicon molecular sieve, in particular to a method for modifying a five-membered ring titanium-silicon molecular sieve (TS-1) with an MFI structure.

Titanium silicate molecular sieve is a new heteroatom molecular sieve developed in the early 1980s. TS-1 with MFI structure, TS-2 with MEL structure, and TS-48 with larger pore structure have been synthesized so far. This type of molecular sieve has excellent catalytic activity and directional oxidation performance for many organic oxidation reactions, such as epoxidation of olefins, hydroxylation of aromatic hydrocarbons, oxidation of cyclohexanone, and oxidation of alcohols. They are used as redox molecular sieves The catalyst has a good application prospect.

TS-1 molecular sieve is a new type of titanium-silicon molecular sieve with excellent directional oxidation catalytic performance formed by introducing transition metal element titanium into the molecular sieve framework with ZSM-5 structure. TS-1 not only has the catalytic oxidation effect of titanium, but also has the shape-selective effect and excellent stability of ZSM-5 molecular sieve. Since TS-1 molecular sieve can use non-polluting low-concentration hydrogen peroxide as an oxidant in the oxidation reaction of organic matter, it avoids the problems of complex oxidation process and environmental pollution, and has incomparable energy saving, economy and environment in traditional oxidation systems. It has the advantages of friendliness and good reaction selectivity, so it has a good industrial application prospect.

The synthesis method of TS-1 was first disclosed by Italian Marco Taramasso et al. in 1981 (GB2071071A, USP4,410,501). The method is to firstly prepare a reaction mixture containing silicon source, titanium source, organic base (RN ⁺ ) and/or basic oxide (Men/ ₂ O), and place the reaction mixture in an autoclave at 130-200°C Hydrothermal crystallization for 6-30 days, then separation, washing, drying and roasting to obtain the product. The silicon source can be tetraalkyl silicate, colloidal SiO ₂ or alkali metal silicate, the titanium source can be a hydrolyzable titanium compound, preferably Ti(OC ₂ H ₅ ) ₄ , and the organic base is preferably tetrapropyl Ammonium hydroxide, wherein the molar composition range of the reaction mixture is:

General range Preferred range

SiO ₂ /TiO ₂ : 5～200 35～65

OH-/SiO ₂ : 0.1～1.0 0.3～0.6

H ₂ O/SiO ₂ : 20～200 60～100

Me/SiO ₂ : 0～0.5 0

RN ⁺ /SiO ₂ : 0.1～2.0 0.4～1.0

People such as Thangaraj think that in the TS-1 molecular sieve synthesized by the above method, the effective titanium content entering the framework is very little, so they disclosed a method for synthesizing the TS-1 molecular sieve that can effectively increase the titanium content of the framework in 1992 (Zeolites, 1992 , Vol.12, P943~950), it is said that the Si/Ti ratio of the molecular sieve obtained by the method proposed by Taramasso et al. can be reduced from 39 to 20. The method is to add an appropriate amount of tetrapropylammonium hydroxide (TPAOH) aqueous solution into the ethyl silicate solution and stir to dissolve for a certain period of time, and then slowly add the isopropanol solution of tetrabutyl titanate under vigorous stirring to obtain a clear liquid The mixture (must be dropped slowly to prevent the tetrabutyl titanate from being hydrolyzed too quickly to form a white TiO ₂ precipitate), after stirring for 15 minutes, slowly add an appropriate amount of TPAOH aqueous solution, and then the reaction mixture is chased with alcohol at 75-80°C for 3-6 After one hour, transfer to an autoclave for hydrothermal crystallization at 170°C for 3 to 6 days, and obtain TS-1 molecular sieve after drying. The molar composition of the reaction mixture is: SiO ₂ : (0.01˜0.10) TiO ₂ : 0.36 TPAOH: 35H ₂ O.

Du Hongwei etc. proposed a kind of preparation method of TS-1 molecular sieve in CN1167082A, this method is to dissolve titanium source in tetrapropyl ammonium hydroxide (TPAOH) aqueous solution, and mix with solid silica gel pellets uniformly to obtain reaction mixture, The reaction mixture is hydrothermally crystallized in an autoclave at 130-200° C. for 1-6 days, and then filtered, washed, dried and roasted according to conventional methods.

The main problem existing in the above-mentioned prior art of synthesizing TS-1 molecular sieve is: because a large part of titanium is retained in the pores of the molecular sieve as extra-skeleton titanium, this part of extra-skeleton titanium not only does not have an effective catalytic oxidation effect, but also The ineffective decomposition of the oxidant (hydrogen peroxide) is caused. Therefore, on the one hand, the catalytic oxidation activity of the prepared TS-1 molecular sieve is low; Active TS-1 molecular sieve, the obtained TS-1 molecular sieve has poor activity and stability, which restricts the industrial application of TS-1 molecular sieve.

The purpose of the present invention is to overcome the shortcoming of prior art, provide a kind of method that prepares the titanium-silicon molecular sieve (TS-1) that has the MFI structure of less extra-framework titanium, make gained TS-1 molecular sieve have better catalytic oxidation activity and better activity stability.

The modification method of titanium silicon molecular sieve (TS-1) provided by the present invention comprises:

(1). Mix the synthesized TS-1 molecular sieve, acidic compound and water evenly, and react at 5-95°C for 5 minutes to 6 hours, preferably at 15-60°C for 10 minutes to 3 hours , to obtain acid-treated TS-1 molecular sieves;

(2). Mix the acid-treated TS-1 molecular sieve, organic base and water obtained in (1) evenly, put the resulting mixture in a sealed reaction kettle, and react for 2 hours at a temperature of 120-200°C and under autogenous pressure. During 8 days, preferably 2 hours to 3 days at 150-180° C. under autogenous pressure, the resulting product was filtered, washed and dried.

The method provided by the present invention may also include repeating the process of step (1) and step (2) one or more times to further reduce the amount of titanium outside the framework of the molecular sieve, thereby improving the catalytic oxidation activity of the molecular sieve.

The said TS-1 molecular sieve of step (1) in the method provided by the present invention can be the TS-1 molecular sieve synthesized according to various methods in the prior art, and it can pass through or not through roasting treatment, promptly can contain or No organic templating agent.

The acidic compound mentioned in step (1) in the method provided by the present invention can be an organic acid compound such as fatty acid R(COOH) _n , wherein R is an alkyl group with 1 to 4 carbon atoms, and n=1 to 2; It can also be inorganic mineral acids such as hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, hydrofluoric acid, etc.; or acidic salt compounds such as ammonium chloride, ammonium phosphate, ammonium nitrate, ammonium sulfate, and ammonium fluoride; the preferred acidic compounds For inorganic acids.

In the method provided by the present invention, the ratio of said molecular sieve, acidic compound and water in step (1) is molecular sieve (gram): acidic compound (mole): water (mole)=100: (0.010～2.0): (5～ 250), preferably 100:(0.080-0.80):(10-100).

The organic base mentioned in step (2) of the method provided by the present invention is fatty amines, alcohol amines or quaternary ammonium base compounds, wherein alcohol amine compounds or quaternary ammonium base compounds are preferred.

The general formula of said aliphatic amine compound is R(NH ₂ ) _n , wherein R is an alkyl group having 1 to 4 carbon atoms, and n=1 to 2, wherein the preferred aliphatic amine compound is ethylamine, n- Butylamine, Butylenediamine or Hexamethylenediamine.

The general formula of said alcohol amine compounds is (HOR') _m N, wherein R' is an alkyl group with 1 to 4 carbon atoms, m=1 to 3, wherein the preferred alcohol amine compounds are monoethanolamine, diethanolamine or triethanolamine.

The general formula of said quaternary ammonium base compound is R" ₃ NOH, wherein R" is an alkyl group with 1-4 carbon atoms, preferably propyl group.

The ratio of said molecular sieve, organic base and water in the method provided by the present invention (2) is molecular sieve (gram): organic base (mole): water (mole)=100: (0.0050～0.50): (5～ 200), preferably 100:(0.010-0.15):(20-80).

Fig. 1 is the X-ray diffraction (XRD) crystal phase diagram of the sample obtained in Example 1.

The present invention reduces the amount of titanium outside the skeleton of the obtained TS-1 molecular sieve due to the method of acid-base mixed treatment, so that its catalytic oxidation activity is significantly improved compared with the prior art (see Example 9), and has better Stability of catalytic activity (see Example 10).

The following examples will further illustrate the present invention. In each of the following examples, the tetrapropylammonium hydroxide used is a product of Tokyo Chemical Industry, Japan, and the rest of the reagents are commercially available chemically pure reagents.

Comparative example 1

This comparative example illustrates the effect of synthesizing TS-1 molecular sieves without following the method of the present invention and prior art (Zeolites, 1992, Vol. 12, pages 943-950).

Mix 22.5 grams of tetraethyl orthosilicate with 7.0 grams of tetrapropylammonium hydroxide, add 59.8 grams of distilled water, mix well, and then hydrolyze at normal pressure and 60°C for 1.0 hour to obtain a hydrolysis solution of tetraethyl orthosilicate A solution consisting of 1.1 g of tetrabutyl titanate and 5.0 g of anhydrous isopropanol was slowly added under vigorous stirring, and the resulting mixture was stirred at 75° C. for 3 hours to obtain a clear transparent colloid. Put this colloid into a stainless steel sealed reaction kettle, and place it at a constant temperature of 170°C and autogenous pressure for 6 days to obtain a mixture of crystallized products; filter the mixture, wash it with water until the pH is 6-8, and dry it at 110°C After 60 minutes, the original powder of TS-1 was obtained. The TS-1 raw powder was calcined in air atmosphere at 550°C for 4 hours to obtain TS-1 molecular sieve. Its XRD crystal phase diagram is similar to that shown in Figure 1.

Example 1

Get the TS-1 molecular sieve obtained in comparative example 1 according to the ratio of molecular sieve (gram): sulfuric acid (mol): water (mol) = 100: 0.15: 150 and mix evenly, react at 90 ℃ for 5.0 hours, then filter according to conventional methods, Washing and drying yields acid-treated TS-1 molecular sieves.

The above-mentioned acid-treated TS-1 molecular sieves are mixed uniformly according to the ratio of molecular sieve (gram): triethanolamine (mol): water (mol) = 100: 0.35: 180, put into a stainless steel sealed reaction kettle, and at a temperature of 190 ° C and autogenous Place it at a constant temperature under pressure for 0.5 days, after cooling and releasing the pressure, filter, wash, and dry according to conventional methods, and roast in an air atmosphere at 550°C for 3 hours to obtain the modified TS-1 molecular sieve of the present invention, and its XRD crystal phase diagram As shown in Figure 1.

Example 2

Get the TS-1 molecular sieve obtained in Comparative Example 1 according to the ratio of molecular sieve (gram): hydrofluoric acid (mol): water (mol) = 100: 0.25: 60, mix evenly, react at 50 ° C for 3.0 hours, and then follow the conventional method Filtration, washing and drying yielded acid-treated TS-1 molecular sieves.

The above-mentioned acid-treated TS-1 molecular sieve is mixed uniformly according to the ratio of molecular sieve (gram): tetrapropylammonium hydroxide (mol): water (mol) = 100: 0.010: 80, put into a stainless steel sealed reaction kettle, at 170 The temperature of ℃ and the temperature of self-generated pressure are kept at constant temperature for 1 day, after cooling and pressure relief, filter, wash and dry according to the conventional method, and roast in air atmosphere at 550 ℃ for 3 hours to obtain the modified TS-1 molecular sieve of the present invention, Its XRD crystal phase diagram is similar to that shown in Figure 1.

Example 3

Get the TS-1 molecular sieve obtained in comparative example 1 according to the ratio of molecular sieve (gram): phosphoric acid (mol): water (mol) = 100: 1.55: 250 and mix evenly, react at 68 ℃ for 0.3 hour, then filter according to conventional methods, Washing and drying yields acid-treated TS-1 molecular sieves.

The TS-1 molecular sieve of above-mentioned acid treatment is mixed according to the ratio of molecular sieve (gram): hexamethylenediamine (mol): water (mol) = 100: 0.50: 200, put into stainless steel sealed reactor, at 140 ℃ of temperature and Place it at a constant temperature under autogenous pressure for 6 days, after cooling and depressurization, filter, wash, and dry according to conventional methods, and roast in an air atmosphere at 550 ° C for 3 hours to obtain the modified TS-1 molecular sieve of the present invention, and its XRD crystal phase The figure is similar to figure 1.

Example 4

Get the TS-1 molecular sieve obtained in Comparative Example 1 according to the ratio of molecular sieve (gram): ammonium nitrate (mol): water (mol) = 100: 3.25: 200 and mix evenly, react at room temperature (25 ℃) for 1.5 hours, then press Filtration, washing and drying by conventional methods to obtain acid-treated TS-1 molecular sieves.

The TS-1 molecular sieve of above-mentioned acid treatment is mixed according to the ratio of molecular sieve (gram): n-butylamine (mol): water (mol)=100: 0.18: 30, put into stainless steel sealed reactor, at 160 ℃ of temperature and Place it at a constant temperature under autogenous pressure for 4.0 days, after cooling and depressurization, filter, wash, and dry according to conventional methods, and roast in an air atmosphere at 500 ° C for 4 hours to obtain the modified TS-1 molecular sieve of the present invention, and its XRD crystal phase The figure is similar to figure 2.

Example 5

The unroasted TS-1 molecular sieve raw powder obtained in Comparative Example 1 was mixed uniformly according to the ratio of molecular sieve (gram):hydrochloric acid (mol):water (mol)=100:0.75:260, and reacted at 15°C for 6.0 hours, Then filter, wash and dry according to conventional methods to obtain acid-treated TS-1 molecular sieve.

The TS-1 molecular sieve of above-mentioned acid treatment is according to molecular sieve (gram): butyldiamine (mol): the ratio of water (mol)=100: 0.30: 10 is mixed evenly, puts into stainless steel sealed reactor, at 155 ℃ of temperature and Place it at a constant temperature under autogenous pressure for 3 days, after cooling and depressurization, filter, wash, and dry according to conventional methods, and roast in an air atmosphere at 600 ° C for 2 hours to obtain the modified TS-1 molecular sieve of the present invention, its XRD crystal phase The figure is similar to figure 1.

Example 6

Get the TS-1 molecular sieve obtained in Comparative Example 1 according to the ratio of molecular sieve (gram): oxalic acid (mol): water (mol) = 100: 4.5: 30 and mix evenly, react at 80 ° C for 2.5 hours, and then follow the conventional method Filtration, washing and drying yielded acid-treated TS-1 molecular sieves.

The above-mentioned acid-treated TS-1 molecular sieves were mixed evenly according to the ratio of molecular sieves (grams): diethanolamine (moles): water (moles) = 100:0.30:50, put into a stainless steel sealed reaction kettle, and at a temperature of 165 ° C and autogenous Place it at a constant temperature under pressure for 2 days, after cooling and releasing the pressure, filter, wash, and dry according to conventional methods, and roast in an air atmosphere at 550°C for 3 hours to obtain the modified TS-1 molecular sieve of the present invention, and its XRD crystal phase diagram Similar to Figure 1.

Example 7

The TS-1 molecular sieve obtained in Comparative Example 1 was mixed uniformly according to the ratio of molecular sieve (g): ammonium fluoride (mol): water (mol) = 100:0.05:80, reacted at 35°C for 4.5 hours, and then followed the conventional method Filtration, washing and drying yielded acid-treated TS-1 molecular sieves.

The above acid-treated TS-1 molecular sieves were mixed uniformly according to the ratio of molecular sieve (gram): tetraethylammonium hydroxide (mol): water (mol) = 100: 0.25: 60, put into a stainless steel sealed reaction kettle, at 175 ℃ temperature and self-generated pressure at a constant temperature for 3 days, after cooling and pressure relief, filter, wash, and dry according to conventional methods, and roast in an air atmosphere at 550 ° C for 3 hours to obtain the modified TS-1 molecular sieve of the present invention. The XRD crystal phase diagram is similar to that shown in Figure 1.

Example 8

Repeat the steps described in Example 7 once, except that the TS-1 molecular sieve obtained by the method of Example 7 is used to replace the TS-1 molecular sieve obtained in Comparative Example 1, to obtain the polyacid-base molecular sieve according to the present invention. Submodified TS-1 molecular sieve. Its XRD crystal phase diagram is similar to that shown in Figure 1.

Example 9

This example illustrates the effect of the TS-1 molecular sieve obtained by the method of the present invention and the method of the comparative example used in the catalytic oxidation reaction of phenol hydroxylation.

表1 名称  苯酚转化率％  苯二酚选择性％               产品分布％  邻苯二酚  对苯二酚  苯醌 实施例1  16.43  98.72  51.80  46.93  1.28 实施例2  21.82  99.18  52.29  46.88  0.82 实施例3  13.75  97.53  52.65  44.87  2.47 实施例4  15.64  98.34  49.17  49.17  1.66 实施例5  16.01  98.88  50.47  48.41  1.12 实施例6  12.10  96.86  50.74  46.12  3.14 实施例7  22.15  99.50  49.57  49.93  0.50 实施例8  22.72  99.34  50.26  49.08  0.66 对比例1  12.54  90.35  45.37  44.98  9.65 The TS-1 molecular sieves prepared in the above-mentioned examples and comparative example 1 were mixed uniformly in a three-necked flask with a condenser according to the weight ratio of TS-1: phenol: acetone = 1: 20.0: 16.0, and the temperature was raised to 80 ° C. Then under stirring state according to phenol: the weight ratio of hydrogen peroxide=1:0.39 is added the hydrogen peroxide that concentration is 30 weight %, reacted 6 hours at this temperature, gained product uses OV-101 capillary column on Varian3400 chromatograph (30m×0.25mm) to measure the distribution of each product, the results are shown in Table 1. In Table 1:

Table 1 name Phenol conversion % Hydroquinone selectivity% Product Distribution % Catechol Quinol Benzoquinone Example 1 16.43 98.72 51.80 46.93 1.28 Example 2 21.82 99.18 52.29 46.88 0.82 Example 3 13.75 97.53 52.65 44.87 2.47 Example 4 15.64 98.34 49.17 49.17 1.66 Example 5 16.01 98.88 50.47 48.41 1.12 Example 6 12.10 96.86 50.74 46.12 3.14 Example 7 22.15 99.50 49.57 49.93 0.50 Example 8 22.72 99.34 50.26 49.08 0.66 Comparative example 1 12.54 90.35 45.37 44.98 9.65

Example 10

This example illustrates the activity stability of the TS-1 molecular sieve obtained by the method of the present invention and the method of the comparative example when it is used in the catalytic oxidation reaction of phenol hydroxylation.

The TS-1 molecular sieves prepared in Example 1 and Comparative Example 1 were mixed uniformly in a three-necked flask with a condenser according to the weight ratio of TS-1: phenol: acetone = 1: 20.0: 16.0, and the temperature was raised to 80 ° C , then under stirring state according to the weight ratio of phenol: hydrogen peroxide=1: 0.39, adding concentration is the hydrogen peroxide of 30% by weight, reacts at this temperature sampling at different times, the sample taken uses OV- on the Varian3400 chromatograph 101 capillary columns (30m * 0.25mm) measure the distribution of each product, and the test results are shown in Table 2. The definition of phenol conversion in Table 2 is the same as in Example 9. It can be seen from Table 2 that the activity of the titanium-silicon molecular sieve obtained after modification by the method of the present invention is improved compared with the molecular sieve obtained in Comparative Example 1, and the activity stability is better. and coke, indicating that the titanium-silicon molecular sieve modified by the method of the present invention has less titanium content outside the framework.

Table 2 Different reaction time phenol conversion rate (mol %) Response time h 2 4 6 8 10 12 twenty four 36 48 Example 1 16.57 20.64 22.72 22.68 22.59 22.14 22.05 21.27 21.08 Comparative example 1 5.26 13.15 12.54 14.29 12.45 11.87 10.24 9.85 8.64

Claims (17)

1. method of modifying with HTS (TS-1) of MFI structure is characterized in that this method comprises:

(1). TS-1 molecular sieve, acid compound and the water that will synthesize mix, and under 5～95 ℃, reacted 5 minutes to 6 hours, obtain acid-treated TS-1 molecular sieve, wherein the ratio of molecular sieve, acid compound and water is molecular sieve (gram): acid compound (mole): water (mole)=100: (0.010～2.0): (5～250);

(2). (1) gained is mixed through acid-treated TS-1 molecular sieve, organic base and water, the gained mixture is put into sealed reactor, 2 hours to the 8 day time of reaction under 120～200 ℃ temperature and self-generated pressure, products therefrom is filtered, washs and drying, and wherein the ratio of molecular sieve, organic base and water is molecular sieve (gram): organic base (mole): water (mole)=100: (0.0050～0.50): (5～200).

2. according to the method for claim 1, it is characterized in that this method also comprises the described process of repetition one or many step (2).

3. according to the process of claim 1 wherein that the said TS-1 molecular sieve of step (1) is the TS-1 molecular sieve that synthesizes according to the whole bag of tricks of the prior art.

4. according to the process of claim 1 wherein that the said acid compound of step (1) is that general formula is R (COOH) _nThe organic fatty acid compounds, wherein R is selected from the alkyl with 1～4 carbon atom; N=1 or 2.

5. according to the process of claim 1 wherein that the said acid compound of step (1) is the inorganic acids compound that is selected from hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid and hydrofluoric acid.

6. according to the process of claim 1 wherein that the said acid compound of step (1) is the bisalt compound that is selected from ammonium chloride, ammonium fluoride, ammonium phosphate, ammonium nitrate and ammonium sulfate.

7. according to the process of claim 1 wherein that the ratio of the said molecular sieve of step (1), acid compound and water is molecular sieve (gram): acid compound (mole): water (mole)=100: (0.080～0.80): (10～100).

8. according to the process of claim 1 wherein in the step (1) that said reaction is 15～60 ℃ of reactions 10 minutes to 3 hours down.

9. according to the process of claim 1 wherein that the said organic base of step (2) is fat amine compound, alcamine compound or quaternary amine alkali compounds.

10. according to the method for claim 9, wherein said its general formula of fat amine compound is R (NH ₂) _n, wherein R is selected from the alkyl with 1～4 carbon atom, n=1 or 2.

11. according to the method for claim 10, wherein said fat amine compound is ethamine, n-butylamine, butanediamine or hexamethylene diamine.

12. according to the method for claim 9, wherein said its general formula of alcamine compound is (HOR ') _mN, wherein R ' is selected from the alkyl with 1～4 carbon atom, m=1,2 or 3.

13. according to the method for claim 12, wherein said alcamine compound is MEA, diethanol amine or triethanolamine.

14. according to the method for claim 9, wherein said its general formula of quaternary amine alkali compounds is R " ₃NOH, wherein R " are selected from the alkyl with 1～4 carbon atom.

15. according to the method for claim 14, wherein said quaternary amine alkali compounds is a TPAOH.

16. according to the process of claim 1 wherein that the ratio of the said molecular sieve of step (2), organic base and water is molecular sieve (gram): organic base (mole): water (mole)=100: (0.010～0.15): (20～80).

17. according to the process of claim 1 wherein in the step (2) that said reaction is reaction 2 hours to 3 days under 150～180 ℃ and self-generated pressure.