CN112742468B - Titanium-containing molecular sieve, preparation method thereof, catalyst and method for selectively oxidizing hydrocarbon - Google Patents

Titanium-containing molecular sieve, preparation method thereof, catalyst and method for selectively oxidizing hydrocarbon Download PDF

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CN112742468B
CN112742468B CN201911048208.XA CN201911048208A CN112742468B CN 112742468 B CN112742468 B CN 112742468B CN 201911048208 A CN201911048208 A CN 201911048208A CN 112742468 B CN112742468 B CN 112742468B
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molecular sieve
titanium
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combination
hydroxyl
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CN112742468A (en
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梁晓航
彭欣欣
夏长久
朱斌
林民
罗一斌
舒兴田
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/89—Silicates, aluminosilicates or borosilicates of titanium, zirconium or hafnium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/391—Physical properties of the active metal ingredient
    • B01J35/393—Metal or metal oxide crystallite size
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    • C07D301/00—Preparation of oxiranes
    • C07D301/02—Synthesis of the oxirane ring
    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/12—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with hydrogen peroxide or inorganic peroxides or peracids
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/02—Synthesis of the oxirane ring
    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/19—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with organic hydroperoxides
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
    • C07D303/02—Compounds containing oxirane rings
    • C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
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    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • B01J2229/183—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself in framework positions
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Abstract

The present disclosure relates to a titanium-containing molecular sieve, R of the titanium-containing molecular sieve, a method of preparing the titanium-containing molecular sieve, a catalyst, and a method of selective oxidation 1121 /R 800 Is 0.01 to 2, R 1121 1121cm in the UV-Raman spectrum of the molecular sieve ‑1 Maximum absorption peak intensity in the vicinity, R 800 800cm in the UV-Raman spectrum of the molecular sieve ‑1 Maximum absorption peak intensity in the vicinity; i of the titanium-containing molecular sieve 2175 /I 2187 Is above 0.5, I 2175 2175cm in the in situ IR spectrum of a CO probe for the molecular sieve ‑1 Maximum absorption peak intensity in the vicinity, I 2187 2187cm in the in situ infrared spectrum of the CO probe of the molecular sieve ‑1 Maximum absorption peak intensity in the vicinity. The molecular sieve disclosed by the invention has higher skeleton titanium content, and titanium is more positioned in pore channels of the molecular sieve, so that the surface non-selective side reaction can be inhibited, and the shape selective performance of the molecular sieve is realized; the molecular sieve has higher catalytic activity in the oxidation reaction of macromolecular hydrocarbon.

Description

Titanium-containing molecular sieve, preparation method thereof, catalyst and method for selectively oxidizing hydrocarbon
Technical Field
The present disclosure relates to a titanium-containing molecular sieve, a method of preparing the same, a catalyst containing the same, and a method of selectively oxidizing hydrocarbons.
Background
The Ti-containing heteroatom molecular sieve refers to a heteroatom molecular sieve with a framework containing isolated tetra-coordinated titanium, has excellent hydrocarbon selective oxidation catalysis performance, and particularly has the advantages of mild reaction conditions, high atom utilization rate, environment-friendly and pollution-free process and the like in the reaction with hydrogen peroxide as an oxidant, and has great industrial application prospect.
Successful development of Ti-containing heteroatom TS-1 of MFI structure is considered as a milestone in the field of molecular sieve catalysis. At present, ti-containing heteroatom molecular sieves represented by TS-1 molecular sieves have been successfully applied to industrial production processes such as propylene epoxidation, phenol hydroxylation, cyclohexanone ammoxidation and the like. However, the Ti-containing heteroatom molecular sieve widely used at present, namely TS-1, is a ten-membered ring mesoporous molecular sieve with an MFI structure, and has a pore diameter of about 5.5nm, which limits the application of the sieve in the selective oxidation reaction of macromolecular hydrocarbons, so how to prepare the macroporous Ti-containing heteroatom molecular sieve is an urgent concern for researchers.
Common macroporous Ti-containing heteroatom molecular sieves are Ti-MWW molecular sieves and Ti-BEA molecular sieves. The Ti-MWW molecular sieve is a molecular sieve with ten-membered ring pore channels and twelve-membered ring intragranular supercages, and has better mass transfer and diffusion capacity to molecules than the MFI structure molecular sieve. Researchers have successfully synthesized Ti-MWW molecular sieves with titanium atoms in the framework by adopting a direct hydrothermal synthesis method, but the Ti-MWW molecular sieves are difficult to synthesize, special templates are required to be used, and boron is required to be introduced as a crystallization aid. The Ti-BEA molecular sieve is the only macroporous molecular sieve with three-dimensional twelve-membered ring pore canal, the Ti-BEA molecular sieve with a framework containing titanium atoms has a narrow synthetic phase area, aluminum or boron is required to be introduced as a crystallization auxiliary agent, and a fluorine mineralizer is required to be used, but the synthesized molecular sieve is thrown to contain a plurality of anatase species without activating hydrogen peroxide capability.
Because of the disadvantages of direct synthesis of large pore Ti-containing heteroatom molecular sieves, researchers have also reported more on secondary synthesis. The Ti-containing heteroatom molecular sieves with MWW structure (Corma A, dlaz U, forn s V, et al Ti/ITQ-2,a new material highly active and selective for the epoxidation of olefins with organic hydroperoxides[J ]. Chemical Communications,1999 (9): 779-780.) are prepared by grafting method and have certain activity in the epoxidation of macromolecular olefins with organic peroxides as oxidizing agents.
A Ti-BEA molecular sieve (Krijnen S, S.cnchez P, jakobs B T F, et al A controlled post-synthesis route to well-defined and active titanium Beta epoxidation catalysts [ J ]. Microporous and Mesoporous Materials,1999,31 (1-2): 163-173.) was prepared by gas-solid phase isomorphous substitution method. The result shows that the Ti-BEA molecular sieve is prepared by using titanium tetrachloride to treat the dealuminated BEA molecular sieve under the conditions of 773K reaction temperature, 0.5h reaction time, 5-150m/s airspeed and the like. The cyclooctene epoxidation activity is evaluated by taking hydrogen peroxide as an oxidant, and the cyclooctene conversion rate and the epoxy product selectivity can reach 69% and 70% respectively; when tert-butyl hydroperoxide is used as oxidant, the conversion rate of cyclooctene and the selectivity of the epoxidation product can reach 47% and 70% respectively.
Ti-BEA molecular sieves were prepared by solid state ion exchange methods (Tang B, dai W, sun X, et al A procedure for the preparation of Ti-Beta zeolites for catalytic epoxidation with hydrogen peroxide [ J ]. Green Chemistry,2014,16 (4): 2281-2291.). Firstly, performing acid treatment and dealumination on a BEA molecular sieve to obtain a DeAl-BEA molecular sieve with a framework which is basically free of aluminum and has hydroxyl vacancies, and then performing solid-state ion exchange by taking titanocene dichloride as a titanium source; titanium can finally enter a framework to form framework titanium in a four-coordination form after roasting, but XPS characterization of a sample shows that the relative content of the four-coordination titanium is low, most of titanium exists in a titanium oxide form, and a large amount of organic chloride is consumed as a solvent for preparing the dichloro-titanocene.
Wolf P et al prepared Ti-BEA molecular sieves by liquid-solid isomorphous substitution (Wolf P, hammond C, conrad S, et al post-synth)etic preparation of Sn-,Ti-and Zr-beta:a facile route to water tolerant,highly active Lewis acidic zeolites[J]Dalton Transactions,2014,43 (11): 4514-4519.). The method takes silicon aluminum BEA molecular sieve as a parent body and utilizes 13mol/L HNO 3 Treating BEA molecular sieve at 100deg.C for 20 hr, washing, filtering, and roasting to obtain DeAl-BEA molecular sieve with skeleton containing no aluminum and hydroxy vacancy; then treating the DeAl-BEA molecular sieve in an ethanol solution of tetraethyl titanate, and finally roasting to obtain the Ti-BEA molecular sieve. Since tetraethyl titanate is not easy to react with silicon hydroxyl groups of the DeAl-BEA molecular sieve, and is more prone to self-polymerization condensation, the prepared Ti-BEA molecular sieve has more inactive non-framework titanium species, and the ultraviolet spectrum characterization result also proves that the Ti-BEA molecular sieve has more inactive non-framework titanium species.
Besides Ti-MWW and Ti-BEA molecular sieves, researchers also adopt a secondary synthesis method to prepare mesoporous molecular sieves containing Ti hetero atoms such as Ti-SBA-15, ti-MCM-41, ti-MCM-48 and the like, but the preparation conditions are very harsh, the flow is complex, and the problem that titanium is easy to run off under the liquid phase reaction condition is solved.
The comprehensive synthesis of the macroporous Ti-containing heteroatom molecular sieve has the defects of great difficulty, harsh preparation conditions, easy formation of inactive titanium species and the like.
Disclosure of Invention
An object of the present disclosure is to provide a titanium-containing molecular sieve having excellent catalytic performance for selective oxidation reactions, and a method of preparing the same.
It is another object of the present disclosure to provide a catalyst comprising the titanium-containing molecular sieve described above and a method of selective oxidation.
To achieve the above object, a first aspect of the present disclosure: providing a titanium-containing molecular sieve, R of the titanium-containing molecular sieve 1121 /R 800 Is 0.01 to 2, R 1121 1121cm in the UV-Raman spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity, R 800 800cm in the UV-Raman spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity; i of the titanium-containing molecular sieve 2175 /I 2187 Is above 0.5, I 2175 2175cm in the in situ IR spectrum of a CO probe for the molecular sieve -1 Maximum absorption peak intensity in the vicinity, I 2187 2187cm in the in situ infrared spectrum of the CO probe of the molecular sieve -1 Maximum absorption peak intensity in the vicinity.
Optionally, the titanium-containing molecular sieve comprises titanium oxide clusters, and the proportion of the number of the titanium oxide clusters with the particle size of 1-10 nm to the total number of the titanium oxide clusters is more than 50%.
Preferably, the ratio of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters is 60% or more.
Further preferably, the ratio of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters is 80% or more.
Alternatively, the ratio of bulk to surface ratio of silicon to titanium of the silicon-containing molecular sieve is from 0.0001 to 1.0, preferably from 0.1 to 0.5.
Optionally, the titanium-containing molecular sieve is selected from one or more of a molecular sieve with an MFI structure, a molecular sieve with a MEL structure, a molecular sieve with a MOR structure, a molecular sieve with a BEA structure, a molecular sieve with a MWW structure, a molecular sieve with an IMF structure, a molecular sieve with a CON structure, a molecular sieve with a TUN structure, a molecular sieve with a FAU structure, and a molecular sieve with an EWT structure, preferably one or more of a molecular sieve with an MFI structure, a molecular sieve with a BEA structure, a molecular sieve with a CON structure, and a molecular sieve with an EWT structure.
A second aspect of the present disclosure: there is provided a process for preparing a titanium-containing molecular sieve according to the first aspect of the present disclosure, the process comprising the steps of:
a. mixing organic titanium salt, ligand compound and solvent to obtain titanium source;
wherein the ligand compound is fatty alcohol, carboxylic acid, fatty amine, aromatic amine, alcohol amine, pyridine and derivatives thereof, hydroxycarboxylic acid or amide, or a combination of two or three of them; and/or the number of the groups of groups,
the ligand compound is beta-diketone, beta-carbonyl ester or alpha-hydroxyketone with enol structure, or the combination of two or three of the beta-diketone, the beta-carbonyl ester or the alpha-hydroxyketone;
b. c, contacting the titanium source 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, and drying and roasting the solid product to obtain a titanium-containing molecular sieve, wherein the infrared hydroxyl spectrum of the molecular sieve with skeleton hydroxyl vacancies is 3550cm -1 Characteristic peaks are located in the vicinity.
Optionally, the organic titanium salt has a structure as shown in formula (1):
Figure BDA0002254645490000051
wherein R is 1 、R 2 、R 3 And R is 4 Each independently is C 1 ～C 6 Alkyl of (a); preferably, R 1 、R 2 、R 3 And R is 4 Each independently is C 2 ～C 4 Is a hydrocarbon group.
Optionally, the ligand compound is C 1 -C 8 Aliphatic polyol, C 1 -C 8 Carboxylic acid of C 1 -C 12 Fatty amine, C 1 -C 8 Alcohol amine, C 1 -C 8 Pyridine and its derivative, C 2 -C 8 Hydroxy carboxylic acid or C of (2) 1 -C 8 Or a combination of two or three thereof; and/or the number of the groups of groups,
the ligand compound is C 2 -C 8 Beta-diketone, C having enol structure 2 -C 8 Beta-carbonyl esters or C having an enol structure 2 -C 8 Or a combination of two or three thereof.
Optionally, the C 1 -C 8 The aliphatic polyol of (a) is 1, 2-propanediol, glycerol, 1, 2-butanediol, 2, 3-butanediol, 1, 2-pentanediol, neopentyl glycol, pentaerythritol, 1, 2-cyclohexanediol, or 2-methyl 2, 4-pentanediol, or a combination of two or three thereof;
the saidC 1 -C 8 The carboxylic acid of (2) is formic acid, acetic acid, oxalic acid, propionic acid, acrylic acid, butyric acid, succinic acid, isobutyric acid, valeric acid, isovaleric acid, tert-valeric acid, 2-methylbutanoic acid, caproic acid, benzoic acid, phenylacetic acid, maleic acid or phthalic acid, or a combination of two or three of them;
the C is 1 -C 12 The aliphatic amine of (2) is methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, n-propylamine, isopropylamine, dipropylamine, tripropylamine, diisopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, dibutylamine, diisobutylamine, pentylamine, isopentylamine, sec-pentylamine or cyclohexylamine, or a combination of two or three thereof;
The C is 1 -C 8 The alcohol amine is ethanolamine, diethanolamine, isopropanolamine, triethanolamine or butyldiethanolamine, or a combination of two or three of the two or more;
the C is 1 -C 8 Is pyridine, piperidine, 2-picoline, 3-picoline, 4-picoline, 2, 4-lutidine, 2, 6-lutidine, 2,4, 6-collidine or 4-dimethylaminopyridine, or a combination of two or three thereof;
the C is 2 -C 8 Is glycolic acid, 2-hydroxypropionic acid, 2-hydroxysuccinic acid, 2, 3-dihydroxysuccinic acid, 3-hydroxy-1, 3, 5-pentatricoic acid, or o-hydroxybenzoic acid, or a combination of two or three thereof;
the C is 1 -C 8 Is formamide, N-methylformamide, N-dimethylformamide, N-methylacetamide, propionamide, acrylamide, carboamide or benzamide, or a combination of two or three thereof;
the C is 2 -C 8 The beta-diketone with enol structure is acetylacetone; the C is 2 -C 8 The beta-carbonyl ester with an enol structure is ethyl acetoacetate; the C is 2 -C 8 The alpha-hydroxy ketone with enol structure is 2-hydroxy acetophenone.
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 them; 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 them.
Optionally, in step a, the molar ratio of the organic titanium salt, the ligand compound and the solvent is 1: (0.5-8): (5-1000), preferably 1: (1-4): (30-500).
Optionally, in step b, the molar ratio of the molecular sieve having backbone hydroxyl vacancies to the titanium source is 1: (0.001 to 0.1), preferably 1: (0.005-0.05), wherein the molecular sieve having skeleton hydroxyl vacancies is formed of SiO 2 The titanium source is calculated as TiO 2 And (5) counting.
Optionally, in the step b, the titanium source and the molecular sieve with skeleton hydroxyl vacancies are contacted in a dropwise manner under the pressure of 0.1-10 Mpa.
Optionally, in step b, the method for removing the solvent comprises self-evaporation, temperature-rising evaporation, grinding evaporation or reduced pressure distillation evaporation, or a combination of two or three of them.
Optionally, in the step b, the conditions of the drying and 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:
demetallizing a silicon-aluminum molecular sieve and/or a silicon-boron molecular sieve serving as a parent molecular sieve in an acid solution, and filtering, washing and drying to obtain the molecular sieve with skeleton hydroxyl vacancies; or,
And desilicating the all-silicon molecular sieve serving as a parent molecular sieve in an alkali solution, and filtering, washing and drying to obtain the molecular sieve with skeleton hydroxyl vacancies.
Optionally, the acid in the acid solution is hydrochloric acid, nitric acid, fluosilicic acid, ethylenediamine tetraacetic 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 base is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three thereof; the conditions of the desilication treatment include: the weight ratio of the molecular sieve to the alkali in the alkali solution is 1: (0.02-1), the temperature is 60-110 ℃ and the time is 0.5-72 hours.
Optionally, the parent molecular sieve has a BEA structure; i of the molecular sieve with skeleton hydroxyl vacancies 3735 /I 3550 4 to 10, I 3735 3735cm in the IR hydroxyl spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity, I 3550 3550cm in the infrared hydroxyl spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity.
A third aspect of the present disclosure: there is provided a catalyst comprising the titanium-containing molecular sieve of the first aspect of the present 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 according to the third aspect of the present disclosure.
Optionally the raw material is C 2 -C 20 Chain fatty olefins, C 5 -C 20 Cyclic aliphatic olefins, C 8 -C 10 Aromatic olefins or C 3 -C 20 Or are among them multifunctional olefinsA combination of two or three of (a);
the oxidant is peroxide, oxygen or ozone, or a combination of two or three of them;
the selective oxidation reaction conditions include: the temperature is 0-300 ℃ and the pressure is 0.01-10MPa.
The molecular sieve provided by the disclosure has higher skeleton titanium content, and titanium is more located in pore channels of the molecular sieve, so that surface non-selective side reaction can be inhibited, and shape selective performance of the molecular sieve is facilitated to be realized; the molecular sieve has higher catalytic activity in the oxidation reaction of macromolecular hydrocarbon.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:
FIG. 1 is an infrared hydroxyl 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 a Ti-BEA molecular sieve prepared in example 1 of the present disclosure.
FIG. 3 is an ultraviolet-Raman spectrum of the Ti-BEA molecular sieves prepared in example 1 of the present disclosure.
FIG. 4 is an in situ infrared spectrum of a CO probe of the Ti-BEA molecular sieve prepared in example 1 of the present disclosure.
FIG. 5 is a transmission electron micrograph of a 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 the CTi-BEA molecular sieve prepared in comparative example 1 of the present disclosure.
Detailed Description
Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
The first aspect of the present disclosure: providing a titanium-containing molecular sieve having an ultraviolet-Raman spectrum of 1121cm -1 The vicinity has a characteristic peak which is commonly regarded as a characteristic absorption peak of tetra-coordinated framework titanium, R of the titanium-containing molecular sieve 1121 /R 800 Is 0.01 to 2, R 1121 1121cm in the UV-Raman spectrum of the molecular sieve -1 Near, e.g. 1110-1130cm -1 Maximum absorption peak intensity in wavenumber range, R 800 800cm in the UV-Raman spectrum of the molecular sieve -1 Near, e.g. 795-835cm -1 Maximum absorption peak intensity in the wavenumber range; i of the titanium-containing molecular sieve 2175 /I 2187 Is 0.5 or more, for example 0.5 to 100, I 2175 2175cm in the in situ IR spectrum of a CO probe for the molecular sieve -1 Near, e.g. 2171-2177cm -1 Maximum absorption peak intensity in wavenumber range, I 2187 2187cm in the in situ infrared spectrum of the CO probe of the molecular sieve -1 Near, e.g. 2183-2190cm -1 Maximum absorption peak intensity in the wavenumber range. The titanium-containing molecular sieve disclosed by the invention has higher four-coordination framework titanium content and higher catalytic activity.
In accordance with the present disclosure, the titanium-containing molecular sieve may further comprise titanium oxide clusters, which refer to titanium oxide species aggregated from titanium dioxide that do not have a typical titanium dioxide crystal form. In addition to framework tetra-coordinated titanium, the vast majority of other titanium species exist in the form of titanium oxide clusters, the particle size distribution of which can vary widely, and in accordance with the present disclosure, the titanium oxide clusters of the titanium-containing molecular sieve exist predominantly in the size range of 1 to 10nm, and in one embodiment, the ratio of the number of titanium oxide clusters having a size of 1 to 10nm to the total number of titanium oxide clusters can be greater than 50%; preferably, the ratio of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters is 60% or more; further preferably, the proportion of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters may be 80% or more, for example, 80 to 100%.
According to the present disclosure, the titanium-containing molecular sieve is TiO, on an oxide basis and on a molar basis 2 With SiO 2 The molar ratio of (2) may be 1: (10 to 1000), preferably 1: (20-200); the ratio of bulk to surface ratio of silicon to titanium of the titanium-containing molecular sieve may be 0.0001 to 1.0, preferably 0.1 to 0.5. The framework titanium active center of the titanium-containing molecular sieve is more positioned in the pore canal of the molecular sieve, so that reactants smaller than the pore diameter of the molecular sieve can enter the pore canal of the molecular sieve to contact the active center, and the selective oxidation reaction of the reactants is facilitated.
In the present disclosure, the surface SiTi ratio refers to SiO of an atomic layer which is not more than 5nm (e.g., 1 to 5 nm) from the surface of the titanium silicalite molecular sieve grains 2 With TiO 2 The mol ratio of the bulk phase silicon-titanium refers to SiO of the whole molecular sieve crystal grain 2 With TiO 2 Molar ratio of (3). The surface SiTi ratio and bulk SiTi ratio can be determined by methods well known to those skilled in the art, such as by transmission electron microscopy-energy dispersive X-ray spectrometry (TEM-EDX) to determine TiO at the edge and center targets of the SiSi molecular sieve 2 With SiO 2 Molar ratio, tiO at edge target 2 With SiO 2 The molar ratio is the silicon-titanium ratio of the surface and the TiO of the central target point 2 With SiO 2 The molar ratio is bulk silicon-titanium ratio; alternatively, the surface silicon-titanium ratio can be determined by an ion excitation etching X-ray photoelectron spectroscopy (XPS) method; the bulk silicon to titanium ratio may be determined by chemical analysis methods or by X-ray fluorescence spectroscopy (XRF) methods.
The type of the titanium-containing molecular sieve is not particularly limited in the present disclosure, and may be a common titanium-containing molecular sieve having various topologies, for example: the titanium-containing molecular sieve may be one or more of a molecular sieve with an MFI structure (such as TS-1), a molecular sieve with an MEL structure (such as TS-2), a molecular sieve with a MOR structure (such as Ti-MOR), a molecular sieve with a BEA structure (such as Ti-BEA), a molecular sieve with a MWW structure (such as Ti-MCM-22), a molecular sieve with an IMF structure (such as Ti-IMF), a molecular sieve with a CON structure (such as Ti-SSZ-13), a molecular sieve with a TUN structure (such as Ti-TUN), a molecular sieve with a FAU structure (such as Ti-Y) and a molecular sieve with an EWT structure (such as Ti-EWT), preferably one or more of a molecular sieve with an MFI structure, a molecular sieve with a BEA structure, a molecular sieve with a CON structure and a molecular sieve with an EWT structure.
A second aspect of the present disclosure: there is provided a process for preparing a titanium-containing molecular sieve according to the first aspect of the present disclosure, the process comprising the steps of:
a. Mixing organic titanium salt, ligand compound and solvent to obtain titanium source;
wherein the ligand compound is fatty alcohol, carboxylic acid, fatty amine, aromatic amine, alcohol amine, pyridine and derivatives thereof, hydroxycarboxylic acid or amide, or a combination of two or three of them; and/or the number of the groups of groups,
the ligand compound is beta-diketone, beta-carbonyl ester or alpha-hydroxyketone with enol structure, or the combination of two or three of the beta-diketone, the beta-carbonyl ester or the alpha-hydroxyketone;
b. c, contacting the titanium source 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, and drying and roasting the solid product to obtain a titanium-containing molecular sieve, wherein the infrared hydroxyl spectrum of the molecular sieve with skeleton hydroxyl vacancies is 3550cm -1 Characteristic peaks are located in the vicinity.
The inventor of the present disclosure found that, although a titanium-containing molecular sieve with a neat structure can be obtained by adopting a liquid-solid same crystal substitution method, the surface of the molecular sieve is relatively rich in titanium, the shape selectivity of the molecular sieve is weakened, the improvement of the reaction selectivity is not facilitated, and titanium mainly exists in a non-framework titanium form, so that the titanium cannot be used as an effective active catalytic component, and the ineffective decomposition of an oxidant is often caused. In one embodiment according to the present disclosure, the ligand compound may be used with a solvent, for example, the solvent may be mixed with the ligand compound prior to slow addition of the molecular sieve having framework hydroxyl vacancies. By using a mixture of an organic titanium salt, a ligand compound and a solvent as a titanium precursor, self-polymerization of the titanium salt is suppressed to facilitate dispersion of the titanium salt, so that titanium is more easily inserted into the molecular sieve framework in the form of isolated tetra-coordinated titanium, and the catalytic activity for selective oxidation reaction is improved.
In accordance with the present disclosure, the organotitanium salt may be an organotitanium compound commonly used in the synthesis of titanium-containing molecular sieves, such as organotitanates, which are well known to those skilled in the art, and in one embodiment, may have a structure as shown in formula (1):
Figure BDA0002254645490000111
wherein R is 1 、R 2 、R 3 And R is 4 Can each independently be C 1 ～C 6 For example methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl. Preferably, R 1 、R 2 、R 3 And R is 4 Can each independently be C 2 ～C 4 For example, ethyl, isopropyl, 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 thereof.
The kind of the ligand compound may vary widely according to the present disclosure, for example, at least one of fatty alcohols, carboxylic acids, fatty amines, aromatic amines, alcohol amines, pyridine and derivatives thereof, hydroxycarboxylic acids, amides, and carbonyl compounds having an enol structure. Among them, aliphatic alcohols, carboxylic acids, aliphatic amines, aromatic amines, alcohol amines, pyridines and derivatives thereof, hydroxycarboxylic acids, amides, and carbonyl compounds having an enol structure may be respectively of conventional kinds.
In one embodiment, the fatty alcohol may be selected from C 1 -C 8 At least one of the aliphatic polyols of (a) such as 1, 2-propanediol, glycerol, 1, 2-butanediol, 2, 3-butanediol, 1, 2-pentanediol, neopentyl glycol, pentaerythritol, 1, 2-cyclohexanediol, or 2-methyl-2, 4-pentanediol, or a combination of two or three thereof; preferably 1, 2-propanediol, 1, 2-butanediol or1, 2-cyclohexanediol, or a combination of two or three thereof.
In one embodiment, the carboxylic acid may be selected from C 1 -C 8 Monocarboxylic acid R of (2) 5 COOH, where R 5 Alkyl, alkenyl, cycloalkyl, aryl groups which may be of 1 to 8 carbon atoms, for example, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, n-hexyl, cyclohexyl, benzyl or phenethyl; the carboxylic acid may also be selected from C 2 -C 8 For example, the carboxylic acid may be oxalic acid, succinic acid, maleic acid, phthalic acid. Preferably, the carboxylic acid is acetic acid, propionic acid, butyric acid or valeric acid, or a combination of two or three thereof.
In one embodiment, the fatty amine may be C 1 -C 12 The aliphatic amine of (2) may be a mono-aliphatic amine such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, sec-pentylamine or cyclohexylamine, or a combination of two or three thereof. The fatty amine may also be a dibasic fatty amine such as ethylenediamine, propylenediamine, 1, 3-propylenediamine, 1, 4-butylenediamine or diethylaminopropylamine, or a combination of two or three thereof. The fatty amine can also be ternary fatty amine, and the general formula is as follows:
Figure BDA0002254645490000121
wherein R is 6 、R 7 And R is 8 Each may be C 1 ～C 6 Alkyl, cycloalkyl, alkenyl or aryl groups of (a); in particular, R 7 、R 8 Or may be H. For example, R 6 、R 7 And R is 8 Each may be methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl or phenyl. Preferably, R 6 At least one selected from the group consisting of methyl, ethyl and n-propyl；R 7 R is R 8 At least one selected from the group consisting of H, methyl, ethyl, n-propyl and isopropyl.
In one embodiment, the alcohol amine may be C 1 -C 8 For example, having a structure represented by any one of formulas I to VI:
Figure BDA0002254645490000131
wherein R is 8 May be C 1 -C 4 Alkylene, alkenylene, R 9 R is R 10 Each may be C 1 -C 4 Alkyl, alkenyl or the corresponding alkylene, alkenylene groups. For example, R 9 Can be methylene, ethylene, n-propylene, isopropylene, allylene, n-butylene, sec-butylene or isobutylene; r is R 10 R is R 11 Each may be methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, isobutyl, sec-butyl, tert-butyl or the corresponding alkylene, alkenylene. Preferably, R 9 Is methylene or ethylene; r is R 10 R is R 11 Is at least one of methyl, ethyl, n-propyl and isopropyl.
In one embodiment, the pyridine and its derivatives may be C 1 -C 8 For example, pyridine, piperidine, 2-picoline, 3-picoline, 4-picoline, 2, 4-lutidine, 2, 6-lutidine, 2,4, 6-collidine, or 4-dimethylaminopyridine, or a combination of two or three thereof; preferably 4-dimethylaminopyridine.
In one embodiment, the hydroxycarboxylic acid may be C 2 -C 8 For example glycolic acid, 2-hydroxypropionic acid, 2-hydroxysuccinic acid, 2, 3-dihydroxysuccinic acid, 3-hydroxy-1, 3, 5-pentatricoic acid or o-hydroxybenzoic acid, or a combination of two or three thereof.
In one embodiment, the amide may be C 1 -C 8 The amide of the general formula:
Figure BDA0002254645490000141
wherein R is 12 、R 13 And R is 14 Each may be C 1 -C 6 Alkyl, alkenyl, aryl or amino, in particular R 12 、R 13 R is R 14 Or may be H. For example, R 12 、R 13 R is R 14 Each may be methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, isobutyl, sec-butyl, tert-butyl, methallyl, cyclopentyl, cyclohexyl or phenyl. Preferably, R 12 H and amino; r is R 13 R is R 14 Is at least one of H, methyl, ethyl and n-propyl.
In one embodiment, the carbonyl compound having an enol structure may be C 2 -C 8 Beta-diketone, C having enol structure 2 -C 8 Beta-carbonyl esters or C having an enol structure 2 -C 8 An alpha-hydroxy ketone having an enol structure, or a combination of two or three thereof; wherein the C 2 -C 8 The beta-diketone having an enol structure of (a) may be acetylacetone; the C is 2 -C 8 The beta-carbonyl ester with an enol structure of (a) can be ethyl acetoacetate; the C is 2 -C 8 The alpha-hydroxy ketone having an enol structure of (a) may be 2-hydroxyacetophenone.
According to the present disclosure, 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 dimethylsulfoxide, or a combination of two or three thereof.
According to the present disclosure, in step a, the molar ratio of the organic titanium salt, the ligand compound and the solvent may be varied within a certain range, for example, the molar ratio of the organic titanium salt, the ligand compound and the solvent may be 1: (0-8): (5-1000), in a preferred embodiment, the molar ratio of the organic titanium salt, the ligand compound, and the solvent may be 1: (1-4): (30-500).
According to the present disclosure, in step b, the molar ratio of the molecular sieve having backbone hydroxyl vacancies to the titanium source may vary over a wide range, for example the molar ratio of the molecular sieve having backbone hydroxyl vacancies to the titanium source may be 1: (0.001 to 0.1), in a preferred embodiment, the molar ratio of the molecular sieve having skeletal hydroxyl vacancies to the titanium source may be 1: (0.005-0.05), wherein the molecular sieve having skeleton hydroxyl vacancies is formed of SiO 2 The titanium source is calculated as TiO 2 And (5) counting.
According to the present disclosure, in step b, the titanium source and the molecular sieve having a skeletal hydroxyl vacancy 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 of removing the solvent may include self-evaporation, temperature-rising evaporation, milling evaporation or reduced pressure distillation evaporation, or a combination of two or three thereof.
According to the present disclosure, in the step b, the conditions of the dry roasting treatment may include: the drying temperature is 60-200deg.C, preferably 80-110deg.C, and the drying time is 0-24 hr, preferably 2-4 hr; the calcination temperature is 300-800 ℃, preferably 400-550 ℃, and the calcination 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 may be prepared using the following steps: demetallizing a silicon-aluminum molecular sieve and/or a silicon-boron molecular sieve serving as a parent molecular sieve in an acid solution, and filtering, washing and drying 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, ethylenediamine tetraacetic acid, oxalic acid, citric acid or sulfosalicylic acid, or a combination of two or three thereof; the conditions of the demetallization treatment 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 a temperature of 60-110 ℃ for a time of 0.5-48 hours, preferably the weight ratio of the molecular sieve to the acid in the acid solution on a dry basis may be 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 may be prepared using the following steps: desilication treatment is carried out on the all-silicon molecular sieve serving as a parent molecular sieve in alkali solution, and filtering, washing and drying are carried out, so that the molecular sieve with skeleton hydroxyl vacancies is obtained; 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, sodium bicarbonate or a combination of two or three of the above; the organic base is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, or a combination of two or three thereof; the conditions of the desilication treatment may include: the weight ratio of the molecular sieve to the alkali in the alkali solution is 1: (0.02-1) at a temperature of 60-110 ℃ for a time of 0.5-72 hours, preferably the weight ratio of the molecular sieve to the alkali in the alkali solution on a dry basis may be 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 a BEA structure; the molecular sieve with skeleton hydroxyl vacancy refers to a molecular sieve with a silicon hydroxyl structure formed by removing part of skeleton atoms of the molecular sieve, and the infrared hydroxyl spectrum of the molecular sieve is 3550cm -1 Characteristic peaks are arranged nearby; further, the molecular sieve having a framework hydroxyl vacancy has a BEA structure, I 3735 /I 3550 May be 4 to 10, preferably 4 to 6, I 3735 3735cm in the IR hydroxyl spectrum of the molecular sieve -1 Near, e.g. 3725-3745cm -1 Maximum absorption peak intensity in wavenumber range, I 3550 Infrared for the molecular sieve3550cm in hydroxyl Spectrum -1 Near, e.g. 3540-3560cm -1 Maximum absorption peak intensity in the wavenumber range.
A third aspect of the present disclosure: there is provided a catalyst comprising the titanium-containing molecular sieve of the first aspect of the present disclosure.
The titanium-containing molecular sieve has higher catalytic activity in the 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 according to the third aspect of the present disclosure.
In accordance with the present disclosure, the feedstock may be, but is not limited to, C 2 -C 20 Chain fatty olefins, C 5 -C 20 Cyclic aliphatic olefins, C 8 -C 10 Aromatic olefins or C 3 -C 20 Or a combination of two or three thereof. For example, the C 2 -C 20 The chain aliphatic olefin of (2) may be 1-hexene, 1-octene, 1-dodecene; the C is 5 -C 20 The cyclic aliphatic olefin of (a) may be cyclopentene, cyclohexene, cyclooctene, α -pinene, cyclododecene, dicyclopentadiene, cyclooctadiene, cyclododecatriene; the C is 8 -C 10 The aromatic olefin of (a) can be styrene, p-chlorostyrene or methylstyrene; the C is 3 -C 20 The multi-functional olefin of (C) can be allyl alcohol, maleic acid, linalool, methyl oleate.
The oxidizing agent may be peroxide, oxygen or ozone, or a combination of two or three thereof, according to the present disclosure. Specific examples of the peroxide may include, but are not limited to, hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide, cyclohexylhydroperoxide, diisopropylbenzene peroxide. The oxidizing agent may be provided as a pure substance or as a solution (preferably as an aqueous solution) or as a mixed gas.
According to the present disclosure, the selective oxidation reaction conditions may include: the temperature is 0-300 ℃, preferably 30-80 ℃, and the pressure is 0.01-10MPa, preferably 0.1-0.5MPa.
The following examples will further illustrate the disclosure, but are not thereby limiting the disclosure.
In examples, the determination of the infrared hydroxyl spectrum of a molecular sieve having skeletal hydroxyl vacancies was carried out on a fourier transform infrared spectrometer model Nicolet 870, the sample was pressed into a self-supporting sheet, placed in an infrared cell, at 1 x 10 -3 The sample was treated at 450℃for 3 hours under Pa conditions, and the infrared hydroxyl spectrum of the sample was measured.
In the examples, the determination of the X-ray powder diffraction (XRD) spectrum of the titanium-containing molecular sieve was performed on a Siemens D5005 type X-ray diffractometer, wherein the crystallinity of the sample relative to the reference sample is expressed as a ratio of the sum of diffraction intensities (peak heights) of five-finger diffraction characteristic peaks of the sample and the reference sample at 2 theta between 22.5 ° and 25.0 °, wherein the crystallinity is calculated as 100% based on the Al-BEA molecular sieve as the reference sample.
In examples and comparative examples, the measurement of ultraviolet-Raman spectrum of the titanium-containing molecular sieve was carried out on a LabRAMHR UV-NIR confocal microscopic Raman spectrometer manufactured by Jobin Yvon Co., france, using a 325nm monochromatic laser of HeCd laser, kimmon, japan as an excitation light source.
In the embodiment, the measurement of the in-situ infrared spectrogram of the CO probe containing the titanium molecular sieve is carried out on a NICOLET6700 Fourier transform infrared instrument of Thermo Fisher company of America, 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, the sample is subjected to high-temperature vacuum desorption and purification, then the temperature is reduced to the liquid nitrogen temperature for adsorbing and purifying CO, and the temperature is gradually increased, so that the infrared characteristic spectrum of CO adsorption is obtained.
In examples and comparative examples, the size (short axis direction) of the titanium oxide clusters of the titanium-containing molecular sieve was measured by a TEM-EDX method, and TEM electron microscope experiments were carried out on a TecnaiF20G2S-TWIN transmission electron microscope of FEI company, equipped with an energy filter system GIF2001 of Gatan company, and equipped with an X-ray spectrometer. The electron microscope sample is prepared on a micro grid with the diameter of 3mm by adopting a suspension dispersion method, is placed in a sample injector after being dried, is then inserted into an electron microscope for observation, and 100 clusters are randomly taken for particle size statistics, so that the proportion of the titanium oxide clusters with the particle size of 1-10 nm to the total titanium oxide clusters is calculated.
In examples and comparative examples, the surface Si/Ti ratio and bulk Si/Ti ratio of the titanium-containing molecular sieve were measured by a transmission electron microscope-energy dispersive X-ray spectrometry (TEM-EDX) method, first dispersing the sample with ethanol, ensuring that the grains do not overlap, loading on a copper mesh, and the amount of sample during dispersion was as small as possible so that the grains do not overlap, then observing the morphology of the sample by a Transmission Electron Microscope (TEM), randomly selecting single isolated particles in the field of view and making a straight line along the diameter direction thereof, 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 the spectrometry microcosmic composition, and measuring SiO, respectively 2 Content and TiO 2 Content of SiO was calculated from this 2 With TiO 2 Molar ratio of (2). Target spot SiO at edge of titanium-silicon molecular sieve 2 With TiO 2 Molar ratio (SiO at 1 st measurement point and 6 th measurement point 2 With TiO 2 Average value of molar ratio) is surface silicon-titanium ratio, and the target spot SiO of the titanium-containing molecular sieve center 2 With TiO 2 Molar ratio (SiO at 3 rd and 4 th measurement points 2 With TiO 2 Average of molar ratios) is the bulk silicon-to-titanium ratio.
The properties of the raw materials used in the examples and comparative examples are as follows:
nitric acid, 66-68 wt% aqueous solution, national drug group chemical company, ltd.
Tetrapropylammonium hydroxide, 20 wt% strength aqueous solution, was available in Guangdong, a chemical plant.
Dichloromethane, analytically pure, tianjin, metallocene chemical reagent company.
Absolute ethanol, analytically pure, tianjin, metallocene chemical company.
Tetraethyl titanate, analytically pure, national pharmaceutical chemicals limited.
1-hexene, analytically pure, national pharmaceutical group chemical company, inc.
Acetonitrile, analytically pure, tianjin, metropetalum chemical reagent company.
Hydrogen peroxide, analytically pure, 30% strength by weight aqueous solution.
The remaining reagents, not further described, were all commercially available and analytically pure.
Example 1
50g (dry basis) of BEA molecular sieve (silicon-aluminum ratio 11) was added with water to prepare a molecular sieve solution having a solid content of 10% by weight, and 13mol/LHNO was added while stirring 3 Heating to 100deg.C, stirring for 20 hr, filtering, washing with water to neutral, oven drying, and calcining at 550deg.C for 2 hr to obtain molecular sieve with skeleton hydroxy vacancy, labeled as DeAl-BEA molecular sieve, whose hydroxy infrared hydroxy spectrum is shown in figure 1, at 3550cm -1 The vicinity has characteristic peaks which indicate that part of framework atoms of the molecular sieve are removed, and the DeAl-BEA molecular sieve with framework hydroxyl vacancies has I 3735 /I 3550 4.3.
Sequentially and slowly adding absolute ethyl alcohol, tetraethyl titanate and 1, 2-butanediol serving as a ligand compound into a three-neck flask, and performing absolute ethyl alcohol: tetraethyl titanate: 1, 2-butanediol = 500:1:1, putting the raw materials into a magnetic stirrer with heating and stirring functions, uniformly mixing the raw materials at 30 ℃ to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, stirring for 4 hours at 30 ℃, removing the solvent by a reduced pressure distillation 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 denoted as Ti-BEA-1, wherein an XRD spectrum is shown in figure 2, and the XRD spectrum has characteristic peaks of the BEA molecular sieve; its ultraviolet-Raman spectrum is shown in FIG. 3, and can be seen at 1121cm -1 The vicinity has obvious characteristic absorption peaks, and the absorption peaks are characteristic peaks which indicate that Ti enters the molecular sieve framework in the form of tetra-coordinated titanium; the in-situ infrared spectrum of the CO probe is shown in FIG. 4, 2175cm can be seen -1 An absorption peak is arranged at the position, and the absorption peak indicates that Ti enters the BEA molecular sieve framework in an isolated four-coordination form; transmission electron microscope photograph thereofAs seen in FIG. 5, it is seen that it has titanium oxide clusters with a particle size of 1 to 10nm, and the evaluation data are shown in Table 1.
Example 2
Adding 50g (dry basis) of all-silicon BEA molecular sieve (BEA molecular sieve containing only Si and O) into water to prepare a molecular sieve solution with the solid content of 10 weight percent, adding 0.1g of sodium hydroxide into the solution, heating to 60 ℃ and stirring for 1h at constant temperature, filtering, washing with water until the filtrate is neutral, drying, roasting at 550 ℃ for 2h to obtain a molecular sieve with skeleton hydroxyl vacancies, namely DeSi-BEA molecular sieve, wherein the hydroxyl infrared hydroxyl spectrum is similar to that of FIG. 1, and the molecular sieve is prepared at 3550cm -1 The vicinity has characteristic peaks which indicate that part of framework atoms of the molecular sieve are removed, and the DeSi-BEA molecular sieve with framework hydroxyl vacancies has I 3735 /I 3550 4.
Sequentially and slowly adding absolute ethyl alcohol serving as a solvent, tetraethyl titanate and a ligand compound benzoic acid into a test tube, and performing absolute ethyl alcohol: tetraethyl titanate: benzoic acid = 125:1:1, uniformly mixing to obtain a titanium source, and then adding a DeSi-BEA molecular sieve, wherein the molar ratio of the DeSi-BEA molecular sieve to the tetraethyl titanate is 40:1, stirring for 4 hours at 30 ℃, removing the solvent by a grinding and volatilizing 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 denoted as Ti-BEA-2, wherein the XRD spectrum is similar to that of FIG. 2, and the XRD spectrum has characteristic peaks of the Ti-BEA molecular sieve; its UV-Raman spectrum is similar to that of FIG. 3, and can be seen at 1121cm -1 The vicinity has obvious characteristic absorption peaks, and the absorption peaks are characteristic peaks which indicate that Ti enters the molecular sieve framework in the form of tetra-coordinated titanium; its CO probe in situ infrared spectrum is similar to that of FIG. 4, and can be seen at 2175cm -1 There is obvious characteristic absorption peak, which indicates Ti enters the molecular sieve framework in the form of isolated tetra-coordinated titanium; the transmission electron micrograph was similar to FIG. 5, and it was found that it had titanium oxide clusters with particle diameters of 1 to 10nm, and the evaluation data are shown in Table 1.
Example 3
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding absolute ethyl alcohol, tetraethyl titanate and a ligand compound diethyl amine into a three-mouth bottle reaction device with an automatic temperature control water bath, magnetic stirring and condensation reflux system, and mixing according to the absolute ethyl alcohol: tetraethyl titanate: diethylamine = 500:1:1, and reflux-stirring for 4 hours at 75 ℃, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, then removing the solvent by heating and volatilizing 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 denoted as Ti-BEA-3, wherein evaluation data are shown in Table 1.
Example 4
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding a solvent of dichloromethane, tetraethyl titanate and a ligand compound of 4-dimethylaminopyridine into a test tube according to absolute ethyl alcohol: tetraethyl titanate: 4-dimethylaminopyridine=125: 1:1, uniformly mixing to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, then removing the solvent by a grinding and volatilizing method to obtain a solid product, drying the solid product at 110 ℃ for 2 hours, and roasting the solid product at 550 ℃ for 3 hours to obtain the titanium-containing molecular sieve prepared in the embodiment, which is denoted as Ti-BEA-4, wherein evaluation data are shown in table 1.
Example 5
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding a solvent of dichloromethane, tetraethyl titanate and a ligand compound of acetylacetone into a high-pressure reaction kettle, and performing ethanol: tetraethyl titanate: acetylacetone=1000: 1:2, stirring for 4 hours under 0.5MPa to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, then removing the solvent by a grinding and volatilizing method to obtain a solid product, drying the solid product at 110 ℃ for 2 hours, and roasting the solid product at 550 ℃ for 3 hours to obtain the titanium-containing molecular sieve prepared in the embodiment, which is denoted as Ti-BEA-5, wherein evaluation data are shown in table 1.
Example 6
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding absolute ethyl alcohol, tetraethyl titanate and ligand compound acetic acid into a three-neck flask according to the absolute ethyl alcohol: tetraethyl titanate: acetic acid=500: 1:1, uniformly mixing the raw materials at room temperature to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, stirring for 4 hours at room temperature, removing the solvent by a reduced pressure distillation and 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 denoted as Ti-BEA-6, wherein evaluation data are shown in table 1.
Example 7
DeAl-EWT molecular sieves having backbone hydroxyl vacancies were prepared according to the procedure of example 1, I 3735 /I 3550 6.
Sequentially and slowly adding a solvent of 1-chlorobutane, tetraethyl titanate and a ligand compound of isooctanoic acid into a three-neck flask according to the proportion of 1-chlorobutane: tetraethyl titanate: isooctanoic acid=1000: 1:1, uniformly mixing the raw materials at room temperature to obtain a titanium source, and then adding a DeAl-EWT molecular sieve, wherein the molar ratio of the DeAl-EWT molecular sieve to the tetraethyl titanate is 80:1, stirring and heating for 4 hours at 60 ℃, then removing the solvent by a reduced pressure distillation and 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 denoted as Ti-EWT-7, wherein evaluation data are shown in table 1.
Example 8
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding ethanol, tetraethyl titanate and 1, 2-butanediol serving as a ligand compound into a three-neck flask, and performing ethanol: tetraethyl titanate: 1, 2-butanediol = 2000:1:1, uniformly mixing the raw materials at room temperature to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, refluxing and stirring for 4 hours at 78 ℃, then evaporating the solvent under normal pressure 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 denoted as Ti-BEA-8, wherein evaluation data are shown in Table 1.
Example 9
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding ethanol, tetraethyl titanate and 1, 2-butanediol serving as a ligand compound into a three-neck flask, and performing ethanol: tetraethyl titanate: 1, 2-butanediol = 500:1:2, uniformly mixing the raw materials at room temperature to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, stirring for 4 hours at room temperature, removing the solvent by reduced pressure rotary evaporation 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 denoted as Ti-BEA-9, wherein evaluation data are shown in table 1.
Example 10
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding ethanol, tetraethyl titanate and 1, 2-butanediol serving as a ligand compound into a test tube, and performing ethanol: tetraethyl titanate; 1, 2-butanediol = 125:1:1, uniformly mixing to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to the tetraethyl titanate is 10:1, then removing the solvent by a grinding and volatilizing method to obtain a solid product, drying the solid product at 110 ℃ for 2 hours, and roasting the solid product at 550 ℃ for 3 hours to obtain the titanium-containing molecular sieve prepared in the embodiment, which is denoted as Ti-BEA-10, wherein evaluation data are shown in table 1.
Example 11
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1.
Sequentially and slowly adding solvent ethanol, tetraisopropyl titanate and ligand compound 1, 2-butanediol into a test tube according to ethanol: tetraisopropyl titanate: 1, 2-butanediol = 125:1:1, uniformly mixing to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the DeAl-BEA molecular sieve to tetraisopropyl titanate is 40:1, then removing the solvent by a grinding and volatilizing method to obtain a solid product, drying the solid product at 110 ℃ for 2 hours, and roasting the solid product at 550 ℃ for 3 hours to obtain the titanium-containing molecular sieve prepared in the embodiment, which is denoted as Ti-BEA-11, wherein evaluation data are shown in table 1.
Comparative example 1
The preparation is carried out according to the method provided in the literature (Wolf P, hammond C, conrad S, et al post-synthetic preparation of Sn-, ti-and Zr-beta: a facile route to water tolerant, highly active Lewis acidic zeolites [ J ]. Dalton Transactions,2014,43 (11): 4514-4519.).
BEA molecular sieves (same as in example 1) 50g (dry basis) of water were added to prepare a molecular sieve solution having a solids content of 10% by weight, and 13mol/LHNO was added with stirring 3 Heating to 100 ℃, stirring for 20 hours at constant temperature, filtering, washing with water until filtrate is neutral, drying, roasting at 550 ℃ for 2 hours to obtain the molecular sieve with skeleton hydroxyl vacancies, and marking as DeAl-BEA molecular sieve.
Sequentially and slowly adding absolute ethyl alcohol and tetraethyl titanate serving as solvents into a three-neck flask, and performing ethanol mixing: tetraethyl titanate = 125:1, putting the raw materials into a magnetic stirrer with heating and stirring functions, uniformly mixing the raw materials at 30 ℃ to obtain a titanium source, and then adding a DeAl-BEA molecular sieve, wherein the molar ratio of the CDeAl-BEA molecular sieve to the tetraethyl titanate is 40:1, stirring at 30deg.C for 4 hr, removing solvent by vacuum distillation to obtain solid product, drying at 110deg.C for 2 hr, and calcining at 550deg.C for 3 hr to obtain titanium-containing molecular sieve prepared in this comparative example, denoted CTi-BEA-1, with ultraviolet-Raman spectrum shown in figure 6 and 1121cm -1 The absorption peaks in the vicinity were weak, which means that only a very small amount of Ti was intercalated into the molecular sieve skeleton as four-coordinate titanium, and the transmission electron micrograph thereof was shown in FIG. 7, and it was found that the particle size of the titanium oxide clusters was 30 to 100nm, and the evaluation data are shown in Table 1.
Comparative example 2
Titanium-containing molecular sieves were prepared as provided in the literature (Tang B, dai W, sun X, et al A procedure for the preparation of Ti-Beta zeolites for catalytic epoxidation with hydrogen peroxide [ J ]. Green Chemistry,2014,16 (4): 2281-2291.).
DeAl-BEA molecular sieves having backbone hydroxyl vacancies were prepared following the procedure of example 1. Then selecting dichloro titanocene as a titanium source, and mixing the DeAl-BEA molecular sieve with the dichloro titanocene according to a mole ratio of 40:1 in a mortar, drying the solid mixed product at 110 ℃ for 2h, and roasting at 550 ℃ for 3h to obtain the titanium-containing molecular sieve prepared in the embodiment, which is denoted as CTi-BEA-2, and has an ultraviolet-Raman spectrum similar to that of FIG. 6, and can be seen at 1121cm -1 The absorption peaks in the vicinity were weak, which means that only a very small amount of Ti was intercalated into the molecular sieve skeleton as four-coordinate titanium, and the transmission electron micrograph was similar to FIG. 7, and it was found that the particle size of the titanium oxide clusters was 30 to 100nm, and the evaluation data are shown in Table 1.
TABLE 1
Figure BDA0002254645490000251
A-the ratio of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters
As can be seen from table 1, the titanium-containing molecular sieves of the present disclosure have a higher framework titanium content and more titanium is located within the pores of the molecular sieve, with the titanium oxide clusters mostly present in a particle size of 1 to 10 nm.
Test case
Samples Ti-BEA-1 to Ti-BEA-11 obtained in examples 1 to 11 and molecular sieve samples CTi-BEA-1 to CTi-BEA-2 obtained by the method of comparative example were tested for catalytic effect for selective oxidation of 1-hexene.
The selective oxidation of 1-hexene was carried out in a 250ml three-necked flask reactor with an automatic temperature control water bath, magnetic stirring and condensation reflux system. The molecular sieve samples obtained in the examples and the comparative examples are respectively added into a three-mouth bottle according to 0.24g of molecular sieve catalyst, 24g of solvent acetonitrile and 2.36g of 1-hexene, and then the three-mouth bottle is put into a water bath kettle with the preset reaction temperature of 40 ℃, 3.70g of hydrogen peroxide (mass fraction of 30%) is slowly added into the reaction system, and after the reaction is finished for 4 hours, the temperature is reduced, and the reaction is stopped. The liquid and solid were separated by filtration, a certain amount of internal standard was added to the filtrate, the product composition was determined on an Agilent 6890N chromatograph using an HP-5 capillary column, the solvent was not integrated, and the calculation results are shown in table 2.
The conversion of 1-hexene and the selectivity of the product 1, 2-epoxyhexane were calculated according to the following formulas, respectively:
Figure BDA0002254645490000261
Figure BDA0002254645490000262
wherein the mass of the initial 1-hexene is designated M 0 The mass of unreacted 1-hexene is designated M CH The mass of 1, 2-epoxyhexane is designated M CHX 。
TABLE 2
Catalyst source 1-hexene conversion% 1, 2-epoxyhexane selectivity,%
Example 1 56.3 98.5
Example 2 45.9 98.5
Example 3 50.1 98.6
Example 4 54.0 98.6
Example 5 41.6 98.1
Example 6 52.6 98.5
Example 7 43.7 99.1
Example 8 40.6 97.6
Example 9 56.1 98.6
Example 10 45.1 98.6
Example 11 53.5 98.6
ComparisonExample 1 25.7 95.9
Comparative example 2 40.1 97.9
* The catalyst is Ti-EWT molecular sieve, the oxidant is tert-butyl hydroperoxide (70%), the temperature is 60 ℃, and the reaction time is 10h.
As can be seen from Table 2, the titanium-containing molecular sieve disclosed by the invention has higher catalytic activity, and is beneficial to improving the raw material conversion rate and the selectivity of target products in the reaction of producing 1, 2-epoxyhexane by using the titanium-containing molecular sieve in the selective oxidation of 1-hexene.
The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims (21)

1. A process for preparing a titanium-containing molecular sieve, comprising the steps of:
a. mixing organic titanium salt, ligand compound and solvent to obtain titanium source;
wherein the ligand compound is fatty alcohol, carboxylic acid, fatty amine, aromatic amine, alcohol amine, pyridine and derivatives thereof, hydroxycarboxylic acid or amide, or a combination of two or three of them; and/or the number of the groups of groups,
the ligand compound is beta-diketone, beta-carbonyl ester or alpha-hydroxyketone with enol structure, or the combination of two or three of the beta-diketone, the beta-carbonyl ester or the alpha-hydroxyketone;
b. c, contacting the titanium source 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, and drying and roasting the solid product to obtain a titanium-containing molecular sieve, wherein the infrared hydroxyl spectrum of the molecular sieve with skeleton hydroxyl vacancies is 3550cm -1 Characteristic peaks are arranged nearby;
in step a, the molar ratio of the organic titanium salt, the ligand compound and the solvent is 1: (0.5-8): (5-1000); in step b, the molar ratio of the molecular sieve with framework hydroxyl vacancies to the titanium source is 1: (0.001-0.1), wherein the molecular sieve having skeleton hydroxyl vacancies is formed of SiO 2 The titanium source is calculated as TiO 2 Counting;
the titanium-containing molecular sieve is a molecular sieve with a BEA structure;
the solvent is a polar proton 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 them; 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;
the conditions of the drying and 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.
2. The method of claim 1, wherein the organotitanium salt has a structure as shown in formula (1):
Figure FDA0004241120250000021
Wherein R is 1 、R 2 、R 3 And R is 4 Each independently is C 1 ～C 6 Is a hydrocarbon group.
3. The method of claim 2, wherein R 1 、R 2 、R 3 And R is 4 Each independently is C 2 ～C 4 Is a hydrocarbon group.
4. The method of claim 1, wherein the ligand compound is C 1 -C 8 Aliphatic polyol, C 1 -C 8 Carboxylic acid of C 1 -C 12 Fatty amine, C 1 -C 8 Alcohol amine, C 1 -C 8 Pyridine and its derivative, C 2 -C 8 Hydroxy carboxylic acid or C of (2) 1 -C 8 Or a combination of two or three thereof; and/or the number of the groups of groups,
the ligand compound is C 2 -C 8 Beta-diketone, C having enol structure 2 -C 8 Beta-carbonyl esters or C having an enol structure 2 -C 8 Or a combination of two or three thereof.
5. The method of claim 4, wherein the C 1 -C 8 The aliphatic polyol of (a) is 1, 2-propanediol, glycerol, 1, 2-butanediol, 2, 3-butanediol, 1, 2-pentanediol, neopentyl glycol, pentaerythritol, 1, 2-cyclohexanediol, or 2-methyl 2, 4-pentanediol, or a combination of two or three thereof;
the C is 1 -C 8 The carboxylic acid of (2) is formic acid, acetic acid, oxalic acid, propionic acid, acrylic acid, butyric acid, succinic acid, isobutyric acid, valeric acid, isovaleric acid, tert-valeric acid, 2-methylbutanoic acid, caproic acid, benzoic acid, phenylacetic acid, maleic acid or phthalic acid Formic acid, or a combination of two or three thereof;
the C is 1 -C 12 The aliphatic amine of (2) is methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, n-propylamine, isopropylamine, dipropylamine, tripropylamine, diisopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, dibutylamine, diisobutylamine, pentylamine, isopentylamine, sec-pentylamine or cyclohexylamine, or a combination of two or three thereof;
the C is 1 -C 8 The alcohol amine is ethanolamine, diethanolamine, isopropanolamine, triethanolamine or butyldiethanolamine, or a combination of two or three of the two or more;
the C is 1 -C 8 Is pyridine, piperidine, 2-picoline, 3-picoline, 4-picoline, 2, 4-lutidine, 2, 6-lutidine, 2,4, 6-collidine or 4-dimethylaminopyridine, or a combination of two or three thereof;
the C is 2 -C 8 Is glycolic acid, 2-hydroxypropionic acid, 2-hydroxysuccinic acid, 2, 3-dihydroxysuccinic acid, 3-hydroxy-1, 3, 5-pentatricoic acid, or o-hydroxybenzoic acid, or a combination of two or three thereof;
the C is 1 -C 8 Is formamide, N-methylformamide, N-dimethylformamide, N-methylacetamide, propionamide, acrylamide, carboamide or benzamide, or a combination of two or three thereof;
The C is 2 -C 8 The beta-diketone with enol structure is acetylacetone; the C is 2 -C 8 The beta-carbonyl ester with an enol structure is ethyl acetoacetate; the C is 2 -C 8 The alpha-hydroxy ketone with enol structure is 2-hydroxy acetophenone.
6. The method according to claim 1, wherein in step a, the molar ratio of the organic titanium salt, the ligand compound and the solvent is 1: (1-4): (30-500);
in step b, the molar ratio of the molecular sieve with framework hydroxyl vacancies to the titanium source is 1: (0.005-0.05).
7. The process of claim 1, wherein in step b, the titanium source is contacted with the molecular sieve having skeletal hydroxyl vacancies in a dropwise manner at a pressure of 0.1 to 10 Mpa.
8. The method of claim 1, wherein in step b, the method of removing solvent from the mixture comprises self-evaporation, temperature-rising evaporation, milling evaporation, or reduced pressure distillation evaporation, or a combination of two or three thereof.
9. The process of claim 1, further comprising preparing the molecular sieve having framework hydroxyl vacancies by:
demetallizing a silicon-aluminum molecular sieve and/or a silicon-boron molecular sieve serving as a parent molecular sieve in an acid solution, and filtering, washing and drying to obtain the molecular sieve with skeleton hydroxyl vacancies; or,
And desilicating the all-silicon molecular sieve serving as a parent molecular sieve in an alkali solution, and filtering, washing and drying to obtain the molecular sieve with skeleton hydroxyl vacancies.
10. The method of claim 9, wherein the acid in the acid solution is hydrochloric acid, nitric acid, fluosilicic acid, ethylenediamine tetraacetic 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 base is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, or a combination of two or three thereof; the conditions of the desilication treatment include: the weight ratio of the molecular sieve to the alkali in the alkali solution is 1: (0.02-1), the temperature is 60-110 ℃ and the time is 0.5-72 hours.
11. The method of claim 9, wherein the parent molecular sieve has a BEA structure; i of the molecular sieve with skeleton hydroxyl vacancies 3735 /I 3550 4 to 10, I 3735 3735cm in the IR hydroxyl spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity, I 3550 3550cm in the infrared hydroxyl spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity.
12. The titanium-containing molecular sieve produced by the method according to any one of claims 1 to 11, wherein R of the titanium-containing molecular sieve 1121 /R 800 Is 0.01 to 2, R 1121 1121cm in the UV-Raman spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity, R 800 800cm in the UV-Raman spectrum of the molecular sieve -1 Maximum absorption peak intensity in the vicinity; i of the titanium-containing molecular sieve 2175 /I 2187 Is above 0.5, I 2175 2175cm in the in situ IR spectrum of a CO probe for the molecular sieve -1 Maximum absorption peak intensity in the vicinity, I 2187 2187cm in the in situ infrared spectrum of the CO probe of the molecular sieve -1 Maximum absorption peak intensity in the vicinity.
13. The titanium-containing molecular sieve according to claim 12, wherein the titanium-containing molecular sieve comprises titanium oxide clusters, and the ratio of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters is 50% or more.
14. The titanium-containing molecular sieve according to claim 13, wherein the ratio of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters is 60% or more.
15. The titanium-containing molecular sieve according to claim 14, wherein the ratio of the number of the titanium oxide clusters having a particle diameter of 1 to 10nm to the total number of the titanium oxide clusters is 80% or more.
16. The titanium-containing molecular sieve of claim 12, wherein the ratio of bulk to surface ratio of silicon to titanium of the titanium-containing molecular sieve is from 0.0001 to 1.0.
17. The titanium-containing molecular sieve of claim 16, wherein the ratio of bulk to surface ratio of silicon to titanium of the titanium-containing molecular sieve is from 0.1 to 0.5.
18. The titanium-containing molecular sieve of claim 12, wherein the titanium-containing molecular sieve is a molecular sieve of BEA structure.
19. A catalyst comprising the titanium-containing molecular sieve of any one of claims 12 to 18.
20. 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 19.
21. The method of claim 20, wherein the feedstock is C 2 -C 20 Chain fatty olefins, C 5 -C 20 Cyclic aliphatic olefins, C 8 -C 10 Aromatic olefins or C 3 -C 20 Or a combination of two or three thereof;
the oxidant is peroxide, oxygen or ozone, or a combination of two or three of them;
the selective oxidation reaction conditions include: the temperature is 0-300 ℃ and the pressure is 0.01-10MPa.
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