Preparation method of titanium-containing molecular sieve, catalyst and selective oxidation method

文档序号：692232 发布日期：2021-05-04 浏览：26次中文

阅读说明：本技术 一种含钛分子筛的制备方法、含钛分子筛和催化剂及选择性氧化方法 (Preparation method of titanium-containing molecular sieve, catalyst and selective oxidation method ) 是由梁晓航彭欣欣夏长久朱斌林民罗一斌舒兴田于 2019-10-30 设计创作，主要内容包括：本公开涉及一种含钛分子筛的制备方法、含钛分子筛和催化剂及选择性氧化方法,该方法包括：a、将有机钛源、无机钛源和溶剂混合,得到含钛的前驱体溶液；b、将步骤a得到的所述含钛的前驱体溶液与具有骨架羟基空位的分子筛进行接触,得到混合物,去除所述混合物中的溶剂得到固体产物,使所述固体产物进行干燥、焙烧,得到含钛分子筛,其中,所述具有骨架羟基空位的分子筛的红外羟基光谱在3550cm～(-1)附近处有特征峰。本公开通过采用有机钛源、无机钛源和溶剂形成的混合物作为钛前驱体,抑制钛盐的自聚从而有利于钛盐的分散,使得钛更容易地以孤立四配位形式进入分子筛骨架内,且钛更多地位于分子筛的孔道内,使其选择性氧化反应的催化活性得以提高。(The disclosure relates to a method for preparing a titanium-containing molecular sieve, the titanium-containing molecular sieve, a catalyst and a selective oxidation method, wherein the method comprises the following steps: a. mixing an organic titanium source, an inorganic titanium source and a solvent to obtain a titanium-containing precursor solution; b. contacting the titanium-containing precursor solution obtained in the step a with a molecular sieve with skeleton hydroxyl vacancies to obtain a mixture, removing a solvent in the mixture to obtain a solid product, drying and roasting the solid product to obtain the titanium-containing molecular sieve, wherein the infrared hydroxyl spectrum of the molecular sieve with the skeleton hydroxyl vacancies is 3550cm ‑1 There is a characteristic peak in the vicinity. The present disclosure is achieved by using an organic titanium source,The mixture formed by the inorganic titanium source and the solvent is used as a titanium precursor, the self-polymerization of the titanium salt is inhibited, so that the dispersion of the titanium salt is facilitated, the titanium can enter a molecular sieve framework in an isolated four-coordination mode more easily, and the titanium is more positioned in pore channels of the molecular sieve, so that the catalytic activity of the selective oxidation reaction of the titanium is improved.)

1. A method of preparing a titanium-containing molecular sieve, comprising the steps of:

a. mixing an organic titanium source, an inorganic titanium source and a solvent to obtain a titanium-containing precursor solution;

b. b, carrying out the step a on the titanium-containing precursor solution and a molecular sieve with skeleton hydroxyl vacanciesContacting to obtain a mixture, removing a solvent in the mixture to obtain a solid product, drying and roasting the solid product to obtain the titanium-containing molecular sieve, wherein the infrared hydroxyl spectrum of the molecular sieve with skeleton hydroxyl vacancies is 3550cm^-1There is a characteristic peak in the vicinity.

2. The process of claim 1, wherein the inorganic titanium source is titanium trichloride, titanium tetrachloride, titanium sulfate, titanium fluoride, titanium bromide, or titanium fluorotitanate, or a combination of two or three thereof; and/or the like and/or,

the organic titanium source is tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate or tetrabutyl titanate, or a combination of two or three of the above.

3. The process according to claim 1, wherein the solvent is a polar protic and/or aprotic solvent; the polar protic solvent is methanol, ethanol, n-propanol, isopropanol, n-butanol or isobutanol, or a combination of two or three of the above; the aprotic solvent is dichloromethane, dichloroethane, chloropropene, methyl chloropropene, 1-chlorobutane, acetonitrile, N-dimethylformamide, toluene, acetone, propylene glycol methyl ether or dimethyl sulfoxide, or a combination of two or three of the above.

4. The process of claim 1, wherein in step a, the molar ratio of the inorganic titanium source, the organic titanium source and the solvent is 1: (0.5-4): (5-2000), preferably 1: (1-3): (20-500); and/or the like and/or,

in the step b, the molar ratio of the molecular sieve with framework hydroxyl vacancies to the titanium of the titanium-containing precursor solution is 1: (0.001 to 0.1), preferably 1: (0.005-0.05) using SiO as the molecular sieve with skeleton hydroxyl vacancy₂The titanium of the titanium-containing precursor solution is expressed as TiO₂And (6) counting.

5. The process of claim 1, wherein in step b, the titanium-containing precursor solution is contacted with the molecular sieve having framework hydroxyl vacancies in a dropwise manner under a pressure of 0.1-10 Mpa.

6. The method according to claim 1, wherein the solvent removing method in step b comprises self-volatilization, temperature-rising volatilization, grinding volatilization or reduced pressure distillation volatilization, or a combination of two or three of the above.

7. The method of claim 1, wherein in step b, the conditions of the dry roasting treatment comprise: the drying temperature is 60-200 ℃, and the drying time is 0-24 hours; the roasting temperature is 300-800 ℃, and the roasting time is 1-10 hours.

8. The process of claim 1, further comprising preparing the molecular sieve having framework hydroxyl vacancies by:

demetallization treatment is carried out on a silicon-aluminum molecular sieve and/or a silicon-boron molecular sieve which are used as parent molecular sieves in an acid solution, and filtration, washing and drying are carried out to obtain the molecular sieve with skeleton hydroxyl vacancies; alternatively, the first and second electrodes may be,

and (3) desiliconizing the all-silicon molecular sieve serving as a parent molecular sieve in an alkali solution, filtering, washing and drying to obtain the molecular sieve with the skeleton hydroxyl vacancy.

9. The method of claim 8, wherein the acid in the acid solution is hydrochloric acid, nitric acid, fluorosilicic acid, ethylenediaminetetraacetic acid, oxalic acid, citric acid, or sulfosalicylic acid, or a combination of two or three thereof; the conditions of the demetallization treatment include: the weight ratio of the molecular sieve to the acid in the acid solution on a dry basis is 1: (5-30) the temperature is 60-110 ℃, and the time is 0.5-48 hours;

the alkali in the alkali solution is inorganic alkali and/or organic alkali; the inorganic base is sodium hydroxide, sodium carbonate or sodium bicarbonate, or a combination of two or three of the above; the organic alkali is tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide or tetrabutyl ammonium hydroxide, or a combination of two or three of the tetramethyl ammonium hydroxide, the tetraethyl ammonium hydroxide, the tetrapropyl ammonium hydroxide or the tetrabutyl ammonium hydroxide; the conditions of the desiliconization treatment include: the weight ratio of the molecular sieve to the alkali in the alkali solution, on a dry basis, is 1: (0.02-1), the temperature is 60-110 ℃, and the time is 0.5-72 hours.

10. The method of claim 8, wherein the parent molecular sieve has a BEA structure; i of the molecular sieve with skeleton hydroxyl vacancies₃₇₃₅/I₃₅₅₀Is 4 to 10, I₃₇₃₅Is 3735cm in an infrared hydroxyl spectrum of the molecular sieve^-1Maximum absorption peak intensity in the vicinity, I₃₅₅₀Is 3550cm in the infrared hydroxyl spectrum of the molecular sieve^-1Maximum absorption peak intensity in the vicinity.

11. A titanium-containing molecular sieve prepared by the method of any one of claims 1 to 10.

12. A catalyst comprising the titanium-containing molecular sieve of claim 11.

13. A method of selective oxidation, the method comprising: contacting the feedstock with an oxidant under selective oxidation reaction conditions in the presence of the catalyst of claim 12.

14. The method of claim 13 wherein said feedstock is C₂-C₂₀Chain aliphatic olefin of (1), C₅-C₂₀Of a cyclic aliphatic olefin, C₈-C₁₀Of aromatic olefins or C₃-C₂₀Or a combination of two or three thereof;

the oxidant is peroxide, oxygen or ozone, or a combination of two or three of the peroxide, the oxygen or the ozone;

the selective oxidation reaction conditions include: the temperature is 0-300 deg.C and the pressure is 0.01-10 MPa.

Technical Field

The disclosure relates to a method for preparing a titanium-containing molecular sieve, the titanium-containing molecular sieve prepared by the method, a catalyst containing the titanium-containing molecular sieve and a selective oxidation method.

Background

Since Enichem company developed titanium silicalite molecular sieve TS-1 with MFI structure in 1983, people developed a series of Ti-containing heteroatom molecular sieves with different framework structures, which show excellent catalytic oxidation performance in selective oxidation reaction of hydrocarbons, and are widely applied to industrial production of olefin epoxidation, ketone ammoximation, phenol hydroxylation and the like.

The titanium silicalite TS-1 is the titanium-containing molecular sieve which is most widely applied at present, and has sinusoidal channels with the pore diameter of about 0.56 multiplied by 0.56nm formed by crossing straight channels in two directions, namely [100] and [010], so that the application of the titanium-containing molecular sieve in the selective oxidation reaction of macromolecular hydrocarbons is limited, and therefore, part of researchers transfer the research gravity center to the titanium-containing molecular sieve with larger pore diameter, such as a Ti-BEA molecular sieve.

Van der Waal et al synthesized gel, then added all-silica molecular sieve seed, and synthesized aluminum-free Ti-BEA molecular sieve (Van der Waal J C, Lin P, Riguto M S, et al. Synthesis of aluminum free from titanium silicate with the BEA structure using a new and selective template and using a catalyst in oxidation [ M ]// study in Surface Science and catalysis. Elsevier,1997,105:1093-1100.) by using bis (cyclohexylmethyl) dimethylammonium hydroxide as template. However, the synthesized Ti-BEA molecular sieve has more unit cell defects to cause poor stability and harsh synthesis conditions, and the Ti-BEA molecular sieve can be synthesized only by long-time crystallization under the condition that the temperature is less than 408K.

Sasidharan et al investigated bis-quaternary ammonium bases in different structures

[R₃N⁺-(CH₂)_x-N⁺R₃](OH)₂(x is 1-6) as template agent, and the rule and performance of synthesizing Ti-BEA molecular sieve in fluorine-containing system (Sasidharan M, Bhaunik A. designing the synthesis of catalytic active Ti-beta using the new catalysts in the presence of fluorine formation [ J)]Physical Chemistry Chemical Physics,2011,13(36): 16282-. Researches show that the Ti-BEA molecular sieve can be successfully prepared only when the length x of the bridged alkyl chain of the diquaternary ammonium base is more than or equal to 4; when x is<When 4, mainly MTW and MFI structure molecular sieves are produced.

Therefore, the conditions for directly synthesizing the Ti-BEA molecular sieve are relatively harsh, fluorine or aluminum must be introduced into a synthesis system to assist the nucleation and crystallization of the molecular sieve, the discharge of fluorine-containing wastewater faces the pressure of environmental protection, and the presence of aluminum promotes the ineffective decomposition of an oxidant (peroxide).

In addition to direct synthesis, researchers have also conducted studies on indirect synthesis of Ti-BEA molecular sieves. MS Rigutto et al synthesized a borosilicate BEA molecular sieve first, then reacted with TiCl₄The reaction is carried out to obtain Ti-BEA Molecular sieve without aluminum in the framework, and then hydrolysis or alcoholysis Boron removal is carried out on the Ti-BEA Molecular sieve, thereby reducing the Boron content in the framework of the Molecular sieve to the minimum (Rigutto M S, De Ruiter R, Nieder J P M, et al titanium-Containing Pore Molecular sieve from Boron-Beta: Preparation, chromatography and Catalysis [ M]I/Studies in Surface Science and catalysis. Elsevier,1994,84: 2245-. But the boron removal is incomplete, so that the epoxidation reaction of 1-octene and 1-hexene has more hydrolysisAnd (3) obtaining the product.

Krijnen et al prepared Ti-BEA molecular sieves using gas-solid isomorphous substitution (Krijnen S, S nchez P, Jakobs B T F, et al A controlled post-synthesis route to well-defined and active titanium zeolite catalysts [ J ] Micropore and meso Materials,1999,31(1-2):163- & 173.). The result shows that the Ti-BEA molecular sieve can be prepared by treating the dealuminized BEA molecular sieve with titanium tetrachloride under the conditions of 773K of reaction temperature, 0.5h of reaction time, 5-150m/s of space velocity and the like. Hydrogen peroxide is used as an oxidant to evaluate the epoxidation activity of cyclooctene, and the conversion rate of the cyclooctene and the selectivity of an epoxy product are 69 percent and 70 percent respectively; when tert-butyl hydroperoxide is used as an oxidant, the conversion rate of cyclooctene and the selectivity of an epoxidation product are 47 percent and 70 percent respectively.

Reddy et al reported a method for preparing Ti-BEA molecular sieves by liquid-solid isomorphous substitution (Reddy J S, Sayari A.A new and simple method for the preparation of active Ti-. beta.zeolite catalysts [ J ]. Journal of the Chemical Society Chemical Communications,1995,26(1): 273-276.). Treating the silicon-aluminum BEA molecular sieve with an ammonium titanyl oxalate solution as a titanium source at normal temperature, and reacting for 24 hours to obtain the partially dealuminized Ti-BEA molecular sieve containing framework titanium. With increasing isomorphous substitution, the titanium content of the framework of the molecular sieve is increased and the aluminum content of the framework is correspondingly reduced. The method can prepare the Ti-BEA molecular sieve with higher silicon-titanium ratio and lower silicon-aluminum ratio, but the epoxidation activity of the Ti-BEA molecular sieve for catalyzing 1-hexene is not obviously improved.

Tang et al prepared Ti-BEA molecular sieves using solid-state ion exchange methods (Tang B, Dai W, Sun X, et al. A procedure for the preparation of Ti-Beta zeolites for catalytic oxidation with hydrogen peroxide [ J ]. Green Chemistry,2014,16(4): 2281-2291.). Firstly, carrying out acid treatment and dealumination on a BEA molecular sieve to obtain a DeAl-BEA molecular sieve which does not contain aluminum basically and has hydroxyl vacancy in a framework, and then carrying out solid ion exchange by taking titanocene dichloride as a titanium source; titanium can enter a framework in a four-coordination form to form framework titanium after being roasted, but XPS (X-ray diffraction) characterization of a sample shows that the relative content of the four-coordination titanium is low, most of the titanium exists in a titanium oxide form, and a large amount of organic chloride is consumed to be used as a solvent for preparing the dichlorotitanocene.

In summary, the synthesized macroporous Ti-containing heteroatom molecular sieve has the disadvantages of low catalytic activity, harsh preparation conditions, easy formation of inactive titanium species, and the like.

Disclosure of Invention

The purpose of the present disclosure is to provide a method for preparing a titanium-containing molecular sieve having excellent catalytic performance for selective oxidation reaction.

It is another object of the present disclosure to provide a titanium-containing molecular sieve prepared by the above method, and a catalyst and a selective oxidation method containing the above titanium-containing molecular sieve.

To achieve the above object, a first aspect of the present disclosure: a method for preparing a titanium-containing molecular sieve is provided, the method comprising the steps of:

a. mixing an organic titanium source, an inorganic titanium source and a solvent to obtain a titanium-containing precursor solution;

b. contacting the titanium-containing precursor solution obtained in the step a with a molecular sieve with skeleton hydroxyl vacancies to obtain a mixture, removing a solvent in the mixture to obtain a solid product, drying and roasting the solid product to obtain the titanium-containing molecular sieve, wherein the infrared hydroxyl spectrum of the molecular sieve with the skeleton hydroxyl vacancies is 3550cm^-1There is a characteristic peak in the vicinity.

Optionally, the inorganic titanium source is titanium trichloride, titanium tetrachloride, titanium sulfate, titanium fluoride, titanium bromide, or titanium fluorotitanate, or a combination of two or three thereof.

Optionally, the organic titanium source is tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate, or tetrabutyl titanate, or a combination of two or three thereof.

Optionally, the solvent is a polar protic solvent and/or an aprotic solvent; the polar protic solvent is methanol, ethanol, n-propanol, isopropanol, n-butanol or isobutanol, or a combination of two or three of the above; the aprotic solvent is dichloromethane, dichloroethane, chloropropene, methyl chloropropene, 1-chlorobutane, acetonitrile, N-dimethylformamide, toluene, acetone, propylene glycol methyl ether or dimethyl sulfoxide, or a combination of two or three of the above.

Optionally, in step a, the molar ratio of the inorganic titanium source, the organic titanium source and the solvent is 1: (0.5-4): (5-2000), preferably 1: (1-3): (20-500).

Optionally, in step b, the molar ratio of the molecular sieve having framework hydroxyl vacancies to the titanium of the titanium-containing precursor solution is 1: (0.001 to 0.1), preferably 1: (0.005-0.05) using SiO as the molecular sieve with skeleton hydroxyl vacancy₂The titanium of the titanium-containing precursor solution is expressed as TiO₂And (6) counting.

Optionally, in step b, the titanium-containing precursor solution is contacted with the molecular sieve with framework hydroxyl vacancies dropwise under the pressure of 0.1-10 Mpa.

Optionally, in step b, the solvent removing method comprises self-volatilization, temperature-rising volatilization, grinding volatilization or reduced pressure distillation volatilization, or a combination of two or three of the above.

Optionally, in step b, the conditions of the dry roasting treatment include: the drying temperature is 60-200 ℃, and the drying time is 0-24 hours; the roasting temperature is 300-800 ℃, and the roasting time is 1-10 hours.

Optionally, the method further comprises preparing the molecular sieve having framework hydroxyl vacancies by:

Optionally, the acid in the acid solution is hydrochloric acid, nitric acid, fluorosilicic acid, ethylenediaminetetraacetic acid, oxalic acid, citric acid, or sulfosalicylic acid, or a combination of two or three thereof; the conditions of the demetallization treatment include: the weight ratio of the molecular sieve to the acid in the acid solution on a dry basis is 1: (5-30) the temperature is 60-110 ℃, and the time is 0.5-48 hours;

Optionally, the parent molecular sieve has a BEA structure; i of the molecular sieve with skeleton hydroxyl vacancies₃₇₃₅/I₃₅₅₀Is 4 to 10, I₃₇₃₅Is 3735cm in an infrared hydroxyl spectrum of the molecular sieve^-1Maximum absorption peak intensity in the vicinity, I₃₅₅₀Is 3550cm in the infrared hydroxyl spectrum of the molecular sieve^-1Maximum absorption peak intensity in the vicinity.

In a second aspect of the present disclosure: there is provided a titanium-containing molecular sieve produced by the method of the first aspect of the disclosure.

A third aspect of the disclosure: a catalyst is provided comprising a titanium-containing molecular sieve according to the second aspect of the disclosure.

A fourth aspect of the present disclosure: a method of selective oxidation is provided, the method comprising: contacting the feedstock with an oxidant under selective oxidation reaction conditions in the presence of a catalyst as described in the third aspect of the present disclosure.

Optionally, the raw material is C₂-C₂₀Chain aliphatic olefin of (1), C₅-C₂₀Of a cyclic aliphatic olefin, C₈-C₁₀Of aromatic olefins or C₃-C₂₀Or a combination of two or three thereof;

the oxidant is peroxide, oxygen or ozone, or a combination of two or three of the peroxide, the oxygen or the ozone;

the selective oxidation reaction conditions include: the temperature is 0-300 deg.C and the pressure is 0.01-10 MPa.

The inventor of the present disclosure finds that, although a titanium-containing molecular sieve with a regular structure can be obtained by a liquid-solid isomorphous substitution method, the surface of the molecular sieve is relatively rich in titanium, so that the shape-selective performance of the molecular sieve is weakened, and the improvement of reaction selectivity is not facilitated. According to the present disclosure, by using a mixture of an organic titanium source, an inorganic titanium source and a solvent as a titanium precursor, the self-polymerization of the titanium salt is inhibited to facilitate the dispersion of the titanium salt, so that the titanium is more easily inserted into the pores of the molecular sieve in the form of nano-scale titanium with a four-coordinate framework, and the catalytic activity on selective oxidation reaction is improved.

Additional features and advantages of the disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

FIG. 1 is an infrared hydroxyl group spectrum of the DeAl-BEA molecular sieve prepared in example 1 of the present disclosure.

FIG. 2 is an X-ray powder diffraction pattern of the Ti-BEA molecular sieve prepared in example 1 of the present disclosure.

Fig. 3 is a uv-raman spectrum of the Ti-BEA molecular sieve prepared in example 1 of the present disclosure.

FIG. 4 is a CO probe in situ IR spectrum of Ti-BEA molecular sieve prepared in example 1 of the present disclosure.

FIG. 5 is a transmission electron micrograph of the Ti-BEA molecular sieve prepared in example 1 of the present disclosure.

Fig. 6 is a uv-raman spectrum of the CTi-BEA molecular sieve prepared in comparative example 1 of the present disclosure.

FIG. 7 is a transmission electron micrograph of a CTi-BEA molecular sieve prepared according to comparative example 1 of the present disclosure.

Detailed Description

The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.

The first aspect of the disclosure: a method for preparing a titanium-containing molecular sieve is provided, the method comprising the steps of:

a. mixing an organic titanium source, an inorganic titanium source and a solvent to obtain a titanium-containing precursor solution;

In accordance with the present disclosure, the inorganic titanium source may be an inorganic titanium compound commonly used in the synthesis of titanium-containing molecular sieves, such as titanium trichloride, titanium tetrachloride, titanium sulfate, titanium fluoride, titanium bromide, or titanium fluorotitanate, or a combination of two or three of them, as is well known to those skilled in the art.

In accordance with the present disclosure, the organic titanium source may be an organic titanium compound, such as an organic titanate, commonly used in the synthesis of titanium-containing molecular sieves, well known to those skilled in the art, and in one embodiment, the organic titanium source may have a structure as shown in formula (1):

wherein R is₁、R₂、R₃And R₄May each independently be C₁～C₆Alkyl of (2) is, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutylAnd a tertiary butyl group. Preferably, R₁、R₂、R₃And R₄May each independently be C₂～C₄Examples of the alkyl group of (1) include ethyl, isopropyl and n-butyl. Further, the organic titanium salt may be tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate, or tetrabutyl titanate, or a combination of two or three of them.

According to the present disclosure, the kind of the solvent may vary over a wide range, and the solvent may be a polar protic solvent and/or an aprotic solvent; the polar protic solvent may be methanol, ethanol, n-propanol, isopropanol, n-butanol or isobutanol, or a combination of two or three thereof; the aprotic solvent may be dichloromethane, dichloroethane, chloropropene, methyl chloropropene, 1-chlorobutane, acetonitrile, N-dimethylformamide, toluene, acetone, propylene glycol methyl ether or dimethyl sulfoxide, or a combination of two or three thereof.

According to the present disclosure, in step a, the molar ratio of the inorganic titanium source, the organic titanium source and the solvent may vary within a certain range, for example, the molar ratio of the inorganic titanium source, the organic titanium source and the solvent may be 1: (0.5-4): (5-2000), and in a preferred embodiment, the molar ratio of the inorganic titanium source, the organic titanium source and the solvent may be 1: (1-3): (30-500).

According to the present disclosure, in step b, the molar ratio of the molecular sieve having framework hydroxyl vacancies to the titanium of the titanium-containing precursor solution may vary within a certain range, for example, the molar ratio of the molecular sieve having framework hydroxyl vacancies to the titanium of the titanium-containing precursor solution may be 1: (0.001 to 0.1), preferably 1: (0.005-0.05) using SiO as the molecular sieve with skeleton hydroxyl vacancy₂The titanium of the titanium-containing precursor solution is expressed as TiO₂And (6) counting.

According to the present disclosure, in step b, the titanium-containing precursor solution and the molecular sieve having skeletal hydroxyl vacancies may be contacted in a dropwise manner under a pressure of 0.1 to 10Mpa, preferably 0.1 to 0.5 Mpa.

According to the present disclosure, in step b, the method for removing the solvent may include self-volatilization, temperature-rising volatilization, grinding volatilization or reduced pressure distillation volatilization, or a combination of two or three of them.

In step b, the dry roasting treatment is a conventional treatment in the art, and the conditions of the dry roasting may include: drying at 60-200 deg.C, preferably 80-110 deg.C for 0-24 hr, preferably 2-4 hr; the roasting temperature is 300-800 ℃, preferably 400-550 ℃, and the roasting time is 1-10 hours, preferably 2-4 hours. In accordance with the present disclosure, the source of the molecular sieve having framework hydroxyl vacancies is not particularly limited, and in one embodiment, the molecular sieve having framework hydroxyl vacancies can be prepared by the following steps: demetallization treatment is carried out on a silicon-aluminum molecular sieve and/or a silicon-boron molecular sieve which are used as parent molecular sieves in an acid solution, and filtration, washing and drying are carried out to obtain the molecular sieve with skeleton hydroxyl vacancies; among them, the kind of the acid solution is not particularly limited, and preferably, the acid in the acid solution is hydrochloric acid, nitric acid, fluosilicic acid, ethylenediaminetetraacetic acid, oxalic acid, citric acid or sulfosalicylic acid, or a combination of two or three of them; the demetallization treatment conditions may include: the weight ratio of the molecular sieve to the acid in the acid solution on a dry basis is 1: (5-30) at 60-110 ℃ for 0.5-48 hours, preferably, the weight ratio of the molecular sieve to the acid in the acid solution on a dry basis is 1: (10-20) the temperature is 80-100 ℃, and the time is 10-24 hours.

In another embodiment, the molecular sieve having framework hydroxyl vacancies can be prepared by the following steps: carrying out desiliconization treatment on an all-silicon molecular sieve serving as a parent molecular sieve in an alkali solution, filtering, washing and drying to obtain the molecular sieve with skeleton hydroxyl vacancies; wherein, the kind of the alkali solution is not particularly limited, and the alkali of the alkali solution may be an inorganic alkali and/or an organic alkali; the inorganic base is sodium hydroxide, sodium carbonate or sodium bicarbonate, or a combination of two or three of the above; the organic alkali is tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide or tetrabutyl ammonium hydroxide, or a combination of two or three of the organic alkali and the tetraethyl ammonium hydroxide; the conditions of the desiliconization treatment may include: the weight ratio of the molecular sieve to the alkali in the alkali solution, on a dry basis, is 1: (0.02-1) at a temperature of 60-110 ℃ for a time of 0.5-72 hours, preferably the weight ratio of said molecular sieve to the alkali in said alkali solution on a dry basis is 1: (0.02-0.05), the temperature is 60-80 ℃, and the time is 0.5-2 hours.

According to the present disclosure, the parent molecular sieve has the BEA structure; the molecular sieve with skeleton hydroxyl vacancy is a molecular sieve with a silicon hydroxyl structure formed after partial skeleton atoms in the molecular sieve are removed, and the infrared hydroxyl spectrum of the molecular sieve is 3550cm^-1Characteristic peaks are arranged near the surface; further, the molecular sieve having skeletal hydroxyl vacancies has the BEA structure, I thereof₃₇₃₅/I₃₅₅₀Can be 4-10, preferably 4-6, I₃₇₃₅Is 3735cm in an infrared hydroxyl spectrum of the molecular sieve^-1In the vicinity of, for example, 3725-3745cm^-1Maximum absorption peak intensity in the wavenumber range, I₃₅₅₀Is 3550cm in the infrared hydroxyl spectrum of the molecular sieve^-1In the vicinity of, for example, 3540-3560cm^-1Maximum absorption peak intensity in the wavenumber range.

In a second aspect of the present disclosure: there is provided a titanium-containing molecular sieve produced by the method of the first aspect of the disclosure. The molecular sieve provided by the disclosure has higher framework titanium content, more titanium is positioned in the pore channel of the molecular sieve, surface non-selective side reaction can be inhibited, and the shape selective performance of the molecular sieve is favorably realized; the molecular sieve has high catalytic activity in the oxidation reaction of macromolecular hydrocarbons.

A third aspect of the disclosure: a catalyst is provided comprising a titanium-containing molecular sieve according to the second aspect of the disclosure.

The titanium-containing molecular sieve disclosed by the invention has higher catalytic activity in oxidation reactions of macromolecular hydrocarbons, such as olefin epoxidation, olefin chlorohydrination, aldehyde ketone ammoximation, aromatic hydrocarbon hydroxylation, thioether oxidation, oxidative desulfurization and the like.

A fourth aspect of the present disclosure: a method of selective oxidation is provided, which may include: contacting the feedstock with an oxidant under selective oxidation reaction conditions in the presence of a catalyst as described in the third aspect of the present disclosure.

According to the present disclosure, the starting material may be, but is not limited to, C₂-C₂₀Chain aliphatic olefin of (1), C₅-C₂₀Of a cyclic aliphatic olefin, C₈-C₁₀Of aromatic olefins or C₃-C₂₀Or a combination of two or three of them. For example, the C₂-C₂₀The chain aliphatic olefin may be 1-hexene, 1-octene, 1-dodecene; said C is₅-C₂₀The cyclic aliphatic olefin can be cyclopentene, cyclohexene, cyclooctene, alpha-pinene, cyclododecene, dicyclopentadiene, cyclooctadiene, cyclododecatriene; said C is₈-C₁₀The aromatic olefin of (a) may be styrene, p-chlorostyrene, methylstyrene; said C is₃-C₂₀The multifunctional olefin can be allyl alcohol, maleic acid, linalool and methyl oleate.

According to the present disclosure, the oxidizing agent may be peroxide, oxygen, or ozone, or a combination of two or three of them. Specific examples of the peroxide may include, but are not limited to, hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide, cyclohexyl hydroperoxide, or dicumyl peroxide, or a combination of two or three thereof. The oxidizing agent may be provided in pure form, or may be provided in the form of a solution (preferably in an aqueous solution) or a mixed gas.

According to the present disclosure, the selective oxidation reaction conditions may include: the temperature is 0-300 deg.C, preferably 30-80 deg.C, and the pressure is 0.01-10MPa, preferably 0.1-0.5 MPa.

According to the present disclosure, by using a mixture of an organic titanium source, an inorganic titanium source and a solvent as a titanium precursor, the self-polymerization of the titanium salt is inhibited to facilitate the dispersion of the titanium salt, so that the titanium is more easily inserted into the pores of the molecular sieve in the form of nano-scale titanium with a four-coordinate framework, and the catalytic activity on selective oxidation reaction is improved.

The following examples will further illustrate the present disclosure, but are not intended to limit the same.

In the examples, the determination of the infrared hydroxyl spectroscopy of molecular sieves with skeletal hydroxyl vacancies was carried out on a Nicolet model 870 Fourier transform Infrared spectrometer, the sample being pressed into a free-standing sheet and placed in an infrared cell at 1X 10^-3And (3) treating the sample for 3h at 450 ℃ under the Pa condition, and measuring the infrared hydroxyl spectrum of the sample.

In the examples, the measurement of the X-ray powder diffraction (XRD) pattern of the titanium-containing molecular sieve was performed on a Siemens D5005 type X-ray diffractometer, in which the crystallinity of the sample relative to a reference sample was expressed by the ratio of the sum of diffraction intensities (peak heights) of five-finger diffraction characteristic peaks between 22.5 ° and 25.0 ° in 2 θ of the sample and the reference sample, and the crystallinity was 100% in terms of Al-BEA molecular sieve as the reference sample.

In the examples and comparative examples, the measurement of the UV-Raman spectrum of the titanium-containing molecular sieve was carried out on a LabRAMHR UV-NIR confocal micro-Raman spectrometer, manufactured by JobinYvon France, using a 325nm monochromatic laser from a HeCd laser, manufactured by Kimmon corporation, Japan.

In the embodiment, the determination of the in-situ infrared spectrogram of the CO probe containing the titanium molecular sieve is carried out on a NICOLET6700 Fourier transform infrared spectrometer of Thermo Fisher company, USA, 10mg of catalyst is pressed into a self-supporting sheet, the self-supporting sheet is placed into a self-made low-temperature quartz infrared in-situ tank, purified samples are desorbed in vacuum at high temperature and then cooled to the temperature of liquid nitrogen to adsorb purified CO, and then the temperature is gradually raised to obtain the infrared characteristic spectrum of CO adsorption.

In examples and comparative examples, the size (minor axis direction) of the titanium oxide cluster of the titanium-containing molecular sieve was measured by the TEM-EDX method, and TEM electron microscopy was performed on a transmission electron microscope of the type TecnaiF20G2S-TWIN, manufactured by FEI, equipped with the energy filter system GIF2001, manufactured by Gatan, and equipped with an X-ray energy spectrometer. An electron microscope sample is prepared on a micro-grid with the diameter of 3mm by adopting a suspension dispersion method, the micro-grid is placed in a sample injector after being dried, then the micro-grid is inserted into an electron microscope for observation, 100 clusters are randomly selected for particle size statistics, and the proportion of titanium oxide clusters with the particle size of 1-10 nm in the total titanium oxide clusters is calculated.

In the examples and comparative examples, the surface silicon-titanium ratio and bulk silicon-titanium ratio of the titanium-containing molecular sieve were determined by transmission electron microscopy-energy dispersive X-ray spectroscopy elemental analysis (TEM-EDX), first dispersing the sample with ethanol, ensuring that the grains do not overlap, loading on a copper mesh, dispersing with as little sample as possible so that the grains do not overlap, then observing the morphology of the sample by Transmission Electron Microscopy (TEM), randomly selecting single isolated grains in the field of view and making a straight line along the diameter direction, uniformly selecting 6 measurement points in the order of 1,2, 3, 4, 5 and 6 from one end to the other end, sequentially performing energy spectroscopic analysis of the microscopic composition, and measuring the SiO respectively₂Content and TiO₂Content of SiO calculated from₂With TiO₂The molar ratio of (a) to (b). Target SiO at edge of titanium-silicon molecular sieve₂With TiO₂Molar ratio (SiO at the 1 st and 6 th measuring points)₂With TiO₂Average value of molar ratio) is the surface silicon-titanium ratio, and the target SiO of the center of the titanium-containing molecular sieve₂With TiO₂Molar ratio (SiO at measurement points 3 and 4₂With TiO₂The average value of the molar ratio) is the bulk silicon-titanium ratio.

The raw materials used in the examples and comparative examples had the following properties:

nitric acid, 66-68 wt% aqueous solution, chemical reagents of national drug group, ltd

Tetrapropylammonium hydroxide, 20% strength by weight aqueous solution, available from Guangdong chemical plant.

Dichloromethane, analytical grade, Tianjin, metallocene chemical reagents.

Absolute ethanol, analytically pure, Tianjin, Daloco Chemicals, Inc.

Tetraethyl titanate, analytically pure, chemical reagents of the national pharmaceutical group, ltd.

Titanium tetrachloride, analytically pure, chemical reagents of the national drug group, ltd.

1-hexene, analytically pure, chemical reagents of the national pharmaceutical group, ltd.

Acetonitrile, analytical grade, Tianjin, Mao Chemicals, Inc.

Hydrogen peroxide, analytically pure, aqueous solution with concentration of 30 wt%.

The other reagents are not further explained, are all commercial products and are analytically pure.

Example 1

Adding water into 50g (dry basis) of BEA molecular sieve (silicon-aluminum ratio is 11) to prepare molecular sieve solution with solid content of 10 weight percent, and adding 13mol/LHNO while stirring₃Heating to 100 deg.C, stirring at constant temperature for 20h, filtering, washing with water to neutral filtrate, oven drying, and calcining at 550 deg.C for 2 hr to obtain molecular sieve with skeleton hydroxyl vacancy, labeled as DeAl-BEA molecular sieve, and its hydroxyl infrared hydroxyl spectrogram is shown in FIG. 1 at 3550cm^-1A characteristic peak is near the molecular sieve, the absorption peak indicates that partial framework atoms of the molecular sieve are removed, and the DeAl-BEA molecular sieve with framework hydroxyl vacancies has I₃₇₃₅/I₃₅₅₀Is 4.3.

Slowly adding dichloromethane, tetraethyl titanate and titanium tetrachloride which are used as solvents into a test tube in sequence, wherein the weight ratio of dichloromethane: tetraethyl titanate: titanium tetrachloride 125: 1: 1, putting the raw materials on a magnetic stirrer with heating and stirring functions, mixing at 30 ℃ to obtain a titanium-containing precursor solution, and adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to tetraethyl titanate is 80: 1, stirring for 4 hours at 30 ℃, then removing the solvent by a grinding volatilization method to obtain a solid product, drying the solid product at 110 ℃ for 2 hours, and roasting at 550 ℃ for 3 hours to obtain the titanium-containing molecular sieve prepared in the embodiment, which is marked as Ti-BEA-1, wherein an XRD spectrogram of the titanium-containing molecular sieve is shown in figure 2, and the titanium-containing molecular sieve has a characteristic peak of the BEA molecular sieve; the ultraviolet-Raman spectrum is shown in FIG. 3 and can be seen at 1121cm^-1A characteristic absorption peak is obvious in the vicinity of the molecular sieve, and the absorption peak is a characteristic peak indicating that Ti enters a molecular sieve framework in the form of four-coordinate titanium; the in-situ infrared spectrum of the CO probe is shown in figure 4, and can be seen at 2175cm^-1An absorption peak is formed, and the absorption peak also indicates that Ti enters the BEA molecular sieve framework in an isolated four-coordination form; the transmission electron micrograph is shown in FIG. 5, and it can be seen that the titanium oxide clusters have a particle size of 1 to 10nm, and the evaluation data are shown in Table 1.

Example 2

Adding water into 50g (dry basis) of all-silicon BEA molecular sieve (BEA molecular sieve only containing Si and O) to prepare molecular sieve solution with solid content of 10 weight percent, adding 0.1g of sodium hydroxide while stirring, heating to 60 ℃, stirring for 1h at constant temperature, filtering, washing with water until filtrate is neutral, drying, roasting at 550 ℃ for 2h to obtain the molecular sieve with skeleton hydroxyl vacancy, and marking as a Desi-BEA molecular sieve, wherein the hydroxyl infrared hydroxyl spectrogram of the molecular sieve is similar to that of figure 1, and the molecular sieve with skeleton hydroxyl vacancy is arranged at 3550cm^-1A characteristic peak is near the molecular sieve, the absorption peak indicates that partial framework atoms of the molecular sieve are removed, and the Desi-BEA molecular sieve with framework hydroxyl vacancies has I₃₇₃₅/I₃₅₅₀Is 4.

Slowly adding solvents of dichloromethane, tetraisopropyl titanate and titanium tetrachloride into a high-pressure reaction kettle in sequence, wherein the weight ratio of absolute ethyl alcohol: tetraisopropyl titanate: titanium tetrachloride of 500: 1: 1, mixing to obtain a titanium-containing precursor solution, and adding a Desi-BEA molecular sieve, wherein the molar ratio of the Desi-BEA molecular sieve to tetraisopropyl titanate is 80: stirring for 4 hours under 0.5MPa, removing the solvent by a heating volatilization method to obtain a solid product, drying the solid product at 110 ℃ for 2 hours, and roasting at 550 ℃ for 3 hours to obtain the titanium-containing molecular sieve prepared in the embodiment, which is marked as Ti-BEA-2, wherein an XRD spectrogram is similar to that of figure 2, and the titanium-containing molecular sieve has a characteristic peak of the Ti-BEA molecular sieve; the ultraviolet-Raman spectrum is similar to that of FIG. 3 and can be seen at 1121cm^-1The absorption peak with medium intensity is near, and the absorption peak is a characteristic peak for indicating that Ti enters the framework of the molecular sieve in the form of four-coordinate titanium; the in-situ infrared spectrum of the CO probe is similar to that of figure 4, and 2175cm can be seen^-1An absorption peak is formed, and the absorption peak is a characteristic peak for indicating that Ti enters a molecular sieve framework in the form of isolated four-coordinate titanium; the transmission electron micrograph of the titanium oxide cluster is similar to that of FIG. 5, and the titanium oxide cluster with the particle size of 1-10 nm is seen, and the evaluation data are shown in Table 1.

Example 3