Titanium silical zeolite ts-1, process for the preparation thereof and process for the epoxidation of olefins

Abstract

The application belongs to the technical field of epoxy compound preparation, and particularly relates to a titanium-silicon molecular sieve TS-1, a preparation method thereof and an olefin epoxidation method. The preparation method comprises the following steps: S1, hydrolysis dispersion: hydrolysis and dispersion of a mixture of a silicon source, a titanium source, a structure directing agent, a monosaccharide compound and water to obtain a mixed system I; S2, water-silicon ratio regulation: adding the mixed system I into a concentration kettle, reducing the water-silicon ratio of the mixed system I through distillation dehydration to obtain a mixed system II; S3, crystallization reaction: transferring the mixed system II into a closed crystallization kettle to crystallize under self-generated pressure, and finally filtering, drying and calcining to obtain the titanium-silicon molecular sieve TS-1. The monosaccharide compound introduced in the mixed system I contains rich hydroxyl groups, which can form hydrogen bond action with the silicon / titanium hydroxyl groups in the molecular sieve precursor, thereby affecting the growth process of the molecular sieve crystal grains, and on this basis, the nucleation process of the molecular sieve can be strengthened by regulating the water-silicon ratio.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of epoxy compound preparation, and particularly relates to a titanium silicalite TS-1 for catalyzing olefin epoxidation, a preparation method thereof and application of the titanium silicalite TS-1 in an olefin epoxidation reaction. BACKGROUND

[0002] Epoxy compounds such as ethylene oxide, propylene oxide and butylene oxide are a kind of compounds with a three-membered ring ether structure. Due to the high tension of the three-membered ring in the epoxy compound and the high reactivity thereof, the epoxy compound is more likely to undergo ring-opening reaction, addition reaction, cycloaddition reaction and the like with other compounds. Therefore, the epoxy compound is widely applied in the fields of chemical industry, material science, pharmacy and paint, and is an important precursor for preparing fine chemical products such as polyether, diol and halogenated alcohol.

[0003] The industrial production method of the epoxy compound is to perform an olefin epoxidation reaction by taking an olefin as a raw material and taking oxygen or air, hydrogen peroxide or an organic peroxide as an oxidant. Taking the hydrogen peroxide as the oxidant as an example, the catalyst of the reaction is mainly a heteroatomic molecular sieve TS-1 containing four-coordinated framework titanium. The process has the advantages of mild reaction conditions, high selectivity of the epoxy compound and low three-waste discharge. Although the hydrogen peroxide / heteroatomic molecular sieve TS-1 catalytic system has been successfully applied to the industrial production of propylene oxide, in order to improve the relative content of the four-coordinated framework titanium in the heteroatomic molecular sieve TS-1 and reduce the interference of other elements, the industrial production of the heteroatomic molecular sieve TS-1 often takes tetraethyl silicate as a silicon source. In the hydrolysis process of the tetraethyl silicate, with the decrease of the water-silicon ratio, the silicon is gradually precipitated to form amorphous silicon species, thereby affecting the uniformity of the precursor distribution, which leads to a high water-silicon ratio (H2O:SiO2>20) of the crystallization system. When the water-silicon ratio of the crystallization system is high, the following problems exist: (1) the single-kettle yield of the molecular sieve synthesis is reduced; (2) the size of the molecular sieve is non-uniformly distributed, the content of small-particle molecular sieve is high, the molecular sieve is difficult to be recovered through filter cloth or membrane separation, the yield of the molecular sieve preparation process is reduced, and the membrane is easily blocked when the membrane separation is used, thereby affecting the normal production of the molecular sieve; and (3) the nitrogen-containing wastewater discharge is large, and it is extremely difficult to treat and reuse. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a titanium silicalite TS-1 with high relative content of four-coordinated framework titanium, uniform grain size distribution and good catalytic effect, which is realized by the following technical scheme:

[0005] The preparation method of the titanium silicalite TS-1 comprises the following steps:

[0006] S1, hydrolytic dispersion: hydrolytic dispersion of a mixture of silicon source, titanium source, structure-directing agent, monosaccharide compound and water to obtain a mixed system I;

[0007] S2, regulating water to silicon ratio: adding the mixed system I into a concentration kettle, reducing the water to silicon ratio of the mixed system I by distillation dehydration to obtain a mixed system II;

[0008] S3, crystallization reaction: transferring the mixed system II into a closed crystallization kettle to crystallize under self-generated pressure, and finally filtering, drying and calcining to obtain titanium silicalite TS-1.

[0009] The monosaccharide compound introduced in the mixed system I contains abundant hydroxyl groups, which can form hydrogen bonds with the silicon / titanium hydroxyl groups in the molecular sieve precursor, thereby affecting the growth process of the molecular sieve crystal, reducing the relative content of the skeleton defects in the molecular sieve crystal, improving the uniformity of the size distribution of the molecular sieve crystal, and having certain influence on the morphology and crystal face orientation of the molecular sieve crystal. In addition, the action can also inhibit the self-aggregation of titanium species to form anatase type non-framework titanium species, and increase the relative content of four-coordinated framework titanium active centers. On this basis, the nucleation process of the molecular sieve can be strengthened by regulating the water to silicon ratio before the crystallization reaction, and at the same time, in cooperation with the monosaccharide compound introduced in the mixed system I, the aggregation of titanium species to form anatase type non-framework titanium species under low water to silicon ratio conditions can be inhibited, the content of four-coordinated framework titanium in the titanium silicalite TS-1 can be increased, and the catalytic performance of the titanium silicalite TS-1 for olefin epoxidation can be improved.

[0010] As a preference, the silicon source in S1 is selected from at least one of organic silicate, silica gel, white carbon black, and silica sol; in order to reduce the influence of heteroatoms in the silicon source on the crystallization product of the catalyst, a single silicon source is preferred; further preferably, the silicon source is at least one of organic silicate, such as methyl orthosilicate, isopropyl silicate, ethyl silicate, tetraethoxysilane, and tetraethyl orthosilicate.

[0011] As a preference, the titanium source in S1 is selected from at least one of titanium tetrachloride, tetrabutyl titanate, tetraethyl titanate, and other organic titanium esters and / or inorganic titanium salts; preferably, the titanium source is at least one of tetrabutyl titanate and tetraethyl titanate.

[0012] As a preference, the structure-directing agent in S1 is selected from at least one of quaternary ammonium base, quaternary ammonium salt, aliphatic amine, and aliphatic alcohol amine.

[0013] Specifically, the structure general formula of the quaternary ammonium base is:

[0014]

[0015] wherein R1, R2, R3, R4 are at least one of C1-C4 alkyl, the C1-C4 alkyl is at least one of C1-C4 linear alkyl, C3-C4 branched alkyl. R1, R2, R3 and R4 can be independently methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.

[0016] Specifically, the general structure of the quaternary ammonium salt is:

[0017]

[0018] wherein R1, R2, R3, R4 are at least one of C1-C4 alkyl, the C1-C4 alkyl is at least one of C1-C4 linear alkyl, C3-C4 branched alkyl. R1, R2, R3 and R4 can be independently methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl; X in the quaternary ammonium salt is at least one of F, Cl, Br, I and other halide ions.

[0019] The general structure of the aliphatic amine is R5(NH2)n, wherein n is an integer of 1 or 2. When n is 1, R5 is at least one of C1-C6 alkyl, the C1-C6 alkyl is at least one of C1-C6 linear alkyl, C3-C6 branched alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, iso-pentyl, tert-pentyl or n-hexyl. When n is 2, R5 is at least one of C1-C6 alkylene, the C1-C6 alkylene is at least one of C1-C6 linear alkylene, C3-C6 branched alkylene, such as methylene, ethylene, n-propylene, n-butylene, n-pentylene or n-hexylene.

[0020] The general structure of the aliphatic alcohol amine is R6(ONH)n, wherein n is an integer of 1 or 2. When n is 1, R6 is at least one of C1-C6 alkyl, the C1-C6 alkyl is at least one of C1-C6 linear alkyl, C3-C6 branched alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, iso-pentyl, tert-pentyl or n-hexyl. When n is 2, R6 is at least one of C1-C6 alkylene, the C1-C6 alkylene is at least one of C1-C6 linear alkylene, C3-C6 branched alkylene, such as methylene, ethylene, n-propylene, n-butylene, n-pentylene or n-hexylene.

[0021] As a preference, the structure directing agent is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tripropylamine, triethylamine, diethylamine, tributylamine, hexanediamine. Further preferably, the structure directing agent is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium chloride.

[0022] As a preference, the monosaccharide compound includes at least one of propenal, propenose, butenal, butenose, erythrose, threose, ribose, arabinose, fructose, xylose, lyxose, allose, altrose, glucose, mannose, gulose, idose, galactose, talose, and at least one of aldo sugars and ketose sugars; further preferably, the monosaccharide compound is at least one of fructose and glucose.

[0023] As a preference, the molar ratio of the silicon source, the titanium source, the structure directing agent, the monosaccharide compound, and water in the mixed system I is 1:(0.0001-0.3):(0.05-0.5):(0.01-3):(20-100), and the silicon source and the titanium source are calculated as SiO2 and TiO2, respectively.

[0024] As a preference, the distillation dehydration in S2 refers to discharging water vapor through the exhaust valve of the concentration kettle at 80-100°C under autogenous pressure to reduce the water to silicon ratio of the mixed system I.

[0025] As a preference, the water to silicon ratio of the mixed system II in S2 is (3-15):1, and the silicon source is calculated as SiO2.

[0026] In the crystallization reaction system, pressure is another important factor affecting the crystal form and crystallization rate of the product, and the autogenous pressure of the reaction system depends on the size of the empty volume of the closed crystallization kettle. In order to improve the efficiency of the crystallization reaction, preferably, the total volume of the mixed system II in S3 is 60-85% of the capacity of the closed crystallization kettle.

[0027] As a preference, the crystallization reaction in S3 is carried out at 120-190°C for 6-96h.

[0028] A titanium silicalite TS-1 is prepared by any one of the above preparation methods.

[0029] As a preference, the titanium silicalite TS-1 contains surface hydroxyl groups, and does not contain adjacent hydroxyl groups and intracrystalline hydroxyl pits.

[0030] As a further preference, the ratio of the Si(OSi)4 and Si(OSi)3(OH) characteristic peaks in the 29Si MAS NMR spectrum of the titanium silicalite TS-1 is >30.

[0031] The present invention also proposes the use of the titanium silicate molecular sieve TS-1 prepared by any of the above preparation methods in olefin epoxidation reaction.

[0032] Preferably, the olefin epoxidation reaction is carried out using titanium silicate TS-1 as a catalyst and hydrogen peroxide as an oxidant, and at 40-90°C and 0.5-5MPa, titanium silicate TS-1, hydrogen peroxide and olefin are contacted and reacted in a reactor to obtain an epoxy compound.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention can enhance the nucleation process of the molecular sieve by regulating the water-silicon ratio before crystallization, reduce the content of skeleton defects in the molecular sieve crystal, improve the size uniformity of the molecular sieve, and increase the molecular sieve yield in the separation process.

[0035] (2) The present invention can inhibit the formation of anatase-type non-framework titanium species by regulating the water-silicon ratio and introducing a monosaccharide compound into the mixed system I, increase the content of tetracoordinate framework titanium, and improve its olefin epoxidation performance. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the specification and specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only a portion of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0037] The unified preparation method of titanium silicate molecular sieve TS-1 in the following examples is:

[0038] S1, hydrolyzing and dispersing a mixture of a silicon source, a titanium source, a structure-directing agent, a monosaccharide compound, and water at 60° C. for 8 h to obtain a mixed system I;

[0039] S2, adding the mixed system I to the concentration kettle, and reducing the water-silicon ratio of the mixed system I by distillation and dehydration to obtain the mixed system II;

[0040] S3. Transfer the mixed system II to a closed crystallization kettle and crystallize it under autogenous pressure. Finally, cool, release the pressure, filter, dry at 110°C for 2h, and calcined at 550°C for 3h to obtain titanium silicate molecular sieve TS-1.

[0041] The unified method for preparing organic esters in the following examples using titanium silicalite TS-1 to catalyze olefin epoxidation reaction is as follows: using titanium silicalite TS-1 as catalyst and hydrogen peroxide as oxidant, the titanium silicalite TS-1, hydrogen peroxide and olefin are contacted and reacted in a reactor under specific temperature and pressure conditions (see table for details) to obtain epoxide compounds.

[0042] Examples 1-3

[0043] The raw materials, raw material ratio and preparation conditions of titanium silicalite TS-1 in Examples 1-3 are shown in Table 1 below.

[0044] Table 1, related parameters for preparing titanium silicalite TS-1 in Examples 1-3

[0045]

[0046] Examples 4-6

[0047] The raw materials, raw material ratio and preparation conditions of titanium silicalite TS-1 in Examples 4-6 are shown in Table 2 below.

[0048] Table 2, related parameters for preparing titanium silicalite TS-1 in Examples 4-6

[0049]

[0050]

[0051] Examples 7-9

[0052] The raw materials, raw material ratio and preparation conditions of titanium silicalite TS-1 in Examples 7-9 are shown in Table 3 below.

[0053] Table 3, related parameters for preparing titanium silicalite TS-1 in Examples 7-9

[0054]

[0055]

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 1 is that no monosaccharide compound is added, and the rest is the same as Example 1, which will not be described in detail in this part.

[0058] Comparative Example 2

[0059] The difference between Comparative Example 2 and Example 1 is that the water-silicon ratio is not controlled, and the rest is the same as Example 1, which will not be described in detail in this part.

[0060] Comparative Example 3

[0061] Comparative Example 3 differs from Example 1 in that neither a monosaccharide compound is added nor the water-to-silicon ratio is regulated, and the rest is the same as Example 1, which will not be described in detail here.

[0062] Performance test

[0063] The following parameters of Examples 1-9 and Comparative Examples 1-3 were measured, and the specific measurement methods are as follows: the grain size was measured by scanning electron microscopy (SEM). The Q4:Q3 measurement method was that the titanium silicate molecular sieve TS-1 prepared was subjected to 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR) testing, and the ratio of Si(OSi)4and Si(OSi)3characteristic peaks was calculated. The calculation formulas of hydrogen peroxide conversion rate, hydrogen peroxide selectivity, and epoxide selectivity are as follows:

[0064]

[0065]

[0066]

[0067] The following table is obtained by calculation and integration:

[0068] Table 4, performance test results

[0069]

[0070] By comparing Examples 1-9 and Comparative Examples 1-3, it can be seen that by introducing a monosaccharide compound in the mixed system I and setting the step of regulating the water-to-silicon ratio on this basis, on the one hand, the grain size distribution range can be effectively reduced, and the titanium silicate molecular sieve TS-1 prepared has a uniform grain distribution. On the other hand, the content of the heteroatom molecular sieve TS-1 with four-coordinated framework titanium can be increased. In addition, when the titanium silicate molecular sieve TS-1 prepared by the method of the present application is used to catalyze the epoxidation of olefins, the selectivity of hydrogen peroxide and epoxide is high, and the catalytic effect is excellent.

Claims

1. A method for preparing titanium silicate molecular sieve TS-1, characterized in that: The following steps are involved: S1. Hydrolysis and dispersion: The mixture of silicon source, titanium source, structure directing agent, monosaccharide compound and water is hydrolyzed and dispersed to obtain a mixture. System I; S2. Adjusting the water-silicon ratio: adding the mixed system I to the concentration kettle, and reducing the water-silicon ratio of the mixed system I by distillation and dehydration to obtain the mixed system II; S3, crystallization reaction: transfer the mixed system II to a closed crystallization reactor, crystallize it under autogenous pressure, and finally obtain titanium silicon molecular sieve TS-1 by filtration, drying and calcination; The molar ratio of tetracoordinate framework Ti to tricoordinate Ti in the titanium silicate molecular sieve TS-1 is greater than 30; and the grain size is 251-376 nm.

2. The method for preparing titanium silicate molecular sieve TS-1 according to claim 1, characterized in that: The monosaccharide compound includes at least one of aldotrigose, acetose, aldotreose, ketutose, erythrose, threose, ribose, arabinose, fructose, xylose, lyxose, allose, altrose, glucose, mannose, gulose, idose, galactose, and talose.

3. The method for preparing titanium silicate molecular sieve TS-1 according to claim 1, characterized in that: The molar ratio of the silicon source, titanium source, structure directing agent, monosaccharide compound and water in the mixed system I is 1: (0.0001-0.3): (0.05-0.5): (0.01-3): (20-100), and the silicon source and titanium source are calculated as SiO2 and TiO2, respectively.

4. The method for preparing titanium silicate molecular sieve TS-1 according to claim 1, characterized in that: The distillation dehydration in S2 refers to the discharge of water vapor through the exhaust valve of the concentration kettle under autogenous pressure of 80 to 100° C. to reduce the water-silicon ratio of the mixed system I.

5. The method for preparing titanium silicate molecular sieve TS-1 according to claim 1 or 4, characterized in that: The water-silicon ratio of the mixed system II in S2 is (3-15):1, and the silicon source is calculated as SiO2.

6. A titanium silicate molecular sieve TS-1, characterized in that Prepared by the method according to any one of claims 1 to 5.

7. The titanium silicate molecular sieve TS-1 according to claim 6, characterized in that: The titanium silicate molecular sieve TS-1 contains surface hydroxyl groups but does not contain adjacent hydroxyl groups and hydroxyl nests within the crystal.

8. Use of the titanium silicate TS-1 prepared by the method of any one of claims 1 to 5 or the titanium silicate TS-1 according to claim 7 in olefin epoxidation.

9. The use according to claim 8, characterized in that With titanium silicate TS-1 as catalyst and hydrogen peroxide as oxidant, titanium silicate TS-1, hydrogen peroxide and olefin are contacted and reacted in a reactor at 40-90°C and 0.5-5MPa to obtain epoxy compound.

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