CN103964461B

CN103964461B - A kind of tin si molecular sieves and preparation method thereof

Info

Publication number: CN103964461B
Application number: CN201310036574.XA
Authority: CN
Inventors: 史春风; 朱斌; 林民
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2013-01-30
Filing date: 2013-01-30
Publication date: 2016-01-13
Anticipated expiration: 2033-01-30
Also published as: CN103964461A

Abstract

The invention provides a kind of tin si molecular sieves, it is characterized in that, containing element silicon, tin element and oxygen element, all or part of intra-die has hole or cavity structure, and total specific surface area>=300m ²/ g, external surface area accounts for ratio>=10% of total specific surface area.Tin si molecular sieves of the present invention has good catalytic oxidation effect.

Description

Tin-silicon molecular sieve and preparation method thereof

Technical Field

The invention relates to a tin-silicon molecular sieve and a preparation method thereof.

Background

Silicon molecular sieves, also known as all-silica zeolites, are molecular sieves whose framework is composed entirely of silicon oxygen elements. For example, the Silicalite-1 (S-1) molecular sieve is an all-silica molecular sieve having a molecular sieve framework of ZSM-5 (MFI) structure. The silicon molecular sieve can be directly used as a material for membrane separation, and can also be formed by replacing partial silicon in a framework with other heteroatoms, so that the application prospect is wide.

The tin metal is introduced into the molecular sieve, for example, the beta type all-silicon molecular sieve to form the Sn beta molecular sieve, and the Sn beta molecular sieve is used in the reaction process of catalyzing and synthesizing lactone and has good directional catalytic performance.

CN1301599A, CN1338427A, CN1338428A, and the like disclose titanium silicalite molecular sieves and all-silica molecular sieves having hollow structures, but so far, no reports of tin silicalite molecular sieves having a cavity structure inside the crystal grains are found.

Disclosure of Invention

The invention aims to provide a tin-silicon molecular sieve with a cavity structure in a crystal grain and a preparation method thereof.

The tin-silicon molecular sieve provided by the invention contains silicon element, tin element and oxygen element, all or part of crystal grains have a cavity or cavity structure, and the total specific surface area is more than or equal to 300m²The proportion of the external specific surface area to the total specific surface area is more than or equal to 10 percent.

The radial length of the cavity part of the hollow crystal grain is 0.1-500 nm, preferably 0.5-300 nm; the material is at 25 ℃ and P/P₀An amount of benzene adsorbed, as measured under the condition of an adsorption time of 1 hour, of at least 25mg/g, preferably at least 35mg/g, of 0.10; a hysteresis loop exists between the adsorption isotherm and the desorption isotherm of low-temperature nitrogen adsorption, and the relative pressure is P/P₀When the nitrogen adsorption amount is about 0.60, the difference between the nitrogen adsorption amount during desorption and the nitrogen adsorption amount during adsorption is more than 2 percent of the nitrogen adsorption amount during adsorption; the shape of the cavity part is not fixed and can be various shapes such as rectangle, circle, irregular polygon and the like, or a knot of one or more of the shapesCombining; the crystal grains with cavities or cavity structures in the material account for 50% -100% of all the crystal grains; the crystal grains may be single crystal grains or aggregated crystal grains aggregated from a plurality of crystal grains.

The invention also provides a method for preparing the tin-silicon molecular sieve, which comprises the following steps:

(1) uniformly mixing a tin source and a silicon molecular sieve in a solid phase manner to obtain a mixture of the tin source and the silicon molecular sieve;

(2) adding a template solution into the mixture of the tin source and the silicon molecular sieve in the step (1);

(3) and (3) transferring the mixture obtained in the step (2) into a reaction kettle, carrying out hydrothermal treatment under the hydrothermal crystallization condition, wherein the reaction kettle contains water which forms saturated water vapor under the reaction condition and has a weight ratio with the molecular sieve of less than 1.2, the treatment capacity of the molecular sieve is at least 10 g/l, and recovering the product to obtain the tin-silicon molecular sieve.

The tin source is introduced into the tin-silicon molecular sieve before the secondary hydrothermal treatment in the preparation process, so that the total specific surface area of the tin-silicon molecular sieve is 300m²More than g, and the proportion of the external specific surface area to the total specific surface area is more than 10 percent.

The tin-silicon molecular sieve according to the invention, more preferably, has an external specific surface area of 35m²More than g.

Generally, the crystal grains of the traditional tin-silicon molecular sieve obtained by adopting the traditional hydrothermal direct crystallization method are in a non-hollow structure, and the proportion of the external specific surface area to the total specific surface area is generally lower than 10%; the tin-silicon molecular sieve crystal grain prepared by introducing the traditional titanium-silicon molecular sieve into a tin source in a supported mode is also in a non-hollow structure, the proportion of the external specific surface area to the total specific surface area is generally lower than 10%, and the external specific surface area is generally not higher than 35m²(ii)/g; meanwhile, even if a hollow-structure silicon molecular sieve (such as the silicon molecular sieve prepared by the CN1338428A method is adopted, the external specific surface area of the hollow-structure silicon molecular sieve accounts for the totalThe proportion of the specific surface area may be more than 10%, and the external specific surface area may also be more than 35m²/g), but the specific surface area after loading tin and other data indexes are changed greatly, and the total specific surface area is 472m before loading²Per gram to 397m after loading with tin²(ii)/g, external specific surface area from 63m before loading²The volume of the solution is reduced to 34m after loading tin²The ratio of the external specific surface area of the samples obtained by loading tin to the total specific surface area is generally less than 10%, and the external specific surface area is generally less than 35m²In terms of/g (see comparative example 4 of the present invention). In the invention, the special specific surface area property of the tin-silicon molecular sieve is presumed to be that a tin source is introduced before secondary hydrothermal treatment in the preparation process of the tin-silicon molecular sieve, and the added tin source can ensure that the structure of the silicon molecular sieve in the secondary hydrothermal crystallization process is changed to a certain extent in the presence of a template agent, so that the proportion of the external specific surface area of the tin-silicon molecular sieve in the total specific surface area is more than 10 percent, and the external specific surface area can reach 35m²More than g. In addition, the tin-silicon molecular sieve has good catalytic oxidation effect, for example, when the tin-silicon molecular sieve is used for phenol hydroxylation reaction, compared with a tin-free silicon molecular sieve or a tin-loaded silicon molecular sieve, the tin-silicon molecular sieve has higher catalytic oxidation activity, and the selectivity of a para-position product hydroquinone is unexpectedly high.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The invention provides a tin-silicon molecular sieve, wherein the tin-silicon molecular sieve contains silicon, oxygen and tin elements, all or part of crystal grains are in a non-hollow structure, and the total specific surface area of the tin-silicon molecular sieve is 300m²At least one of water and water, preferably 310 to 600m²The proportion of the external specific surface area to the total specific surface area is more than 10 percent.

Tin-silicon compounds according to the inventionThe external specific surface area of the sub-sieve, preferably the tin-silicon molecular sieve is 35m²A total of 35 to 150m, preferably²A more preferable range is 35 to 100m²/g。

According to the tin-silicon molecular sieve disclosed by the invention, the proportion of the external specific surface area of the tin-silicon molecular sieve in the total specific surface area is preferably 10-30%, and more preferably 10-25%.

In the present invention, the total specific surface area refers to the BET total specific surface area; and the external specific surface area refers to the surface area of the external surface of the tin-silicon molecular sieve, and can also be referred to as the external surface area for short. The total specific surface area, the external specific surface area and the like can be measured according to the standard method of ASTM D4222-98.

According to the tin-silicon molecular sieve, the tin-silicon molecular sieve with the hollow crystal grains has the spectral properties of a conventional tin-silicon molecular sieve, and particularly, the tin-silicon molecular sieve has a diffraction peak at 0.5-9 degrees of 2 theta in an XRD (X-ray diffraction) pattern, and preferably has a diffraction peak at 5-9 degrees of 2 theta; 460cm in the FT-IR spectrum^-1、975cm^-1、800cm^-1、1080cm^-1Nearby absorption; the absorption is at 200-300 nm in the UV-Vis spectrum, and preferably at 200-260 nm.

According to the tin-silicon molecular sieve, the purpose of the invention can be achieved according to the technical scheme, and for the tin-silicon molecular sieve, the mass ratio of tin element to silicon element in the tin-silicon molecular sieve is preferably 0.05-10: 100, more preferably 0.1-5: 100, and particularly preferably 0.2-2: 100. The tin element and the silicon element in such a ratio can further optimize the catalytic activity of the tin-silicon molecular sieve of the invention.

The tin-silicon molecular sieve according to the invention, which has a P/P ratio at 25 ℃₀The benzene adsorption amount measured under the condition of 0.10 and 1 hour of adsorption time is at least 35 mg/g. A hysteresis loop exists between the adsorption isotherm and the desorption isotherm of the low-temperature nitrogen adsorption. Further, it is at a relative pressure P/P₀The difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption at 0.60 is greater than 2% of the nitrogen adsorption amount at adsorption.

According to the tin-silicon molecular sieve, the crystal grains with cavities or cavity structures inside the crystal grains account for 50-100% of the total crystal grains. The radial length of the cavity part inside the crystal grain is 0.5-300 nm.

The present invention further provides a process for preparing the above tin-silicon molecular sieve, which comprises:

According to the method of the present invention, the variety of the tin source can be selected widely, and any substance containing tin (for example, a compound containing tin element and/or a simple substance of tin) can achieve the object of the present invention. Inorganic tin compounds such as various inorganic salts of tin and hydrates thereof, e.g., tin chloride pentahydrate, tin nitrate, tin sulfate, tin phosphate, etc.; the organotin compound such as various organic acid salts or organic ligand compounds of tin is preferably various organic acid salts of tin such as acetic acid salts, because the organic ligand compounds of tin are generally highly toxic.

In the production process of the present invention, the silica molecular sieve may be at least one of a silica molecular sieve of MFI structure (e.g., S-1), MEL structure (e.g., S-2), BEA structure (e.g., Beta), MWW structure (e.g., MCM-22), two-dimensional hexagonal structure (e.g., MCM-41, SBA-15), MOR structure (e.g., MOR), TUN structure (e.g., TUN) and other structure (e.g., ZSM-48, MCM-48). Preferably, the silicon molecular sieve is one or more of a silicon molecular sieve of an MFI structure, a silicon molecular sieve of an MEL structure and a silicon molecular sieve of a BEA structure, and more preferably, a silicon molecular sieve of an MFI structure.

In the present invention, said silicalite is commercially available or can be prepared, and the method for preparing said silicalite is well known to those skilled in the art and will not be described herein.

In the invention, the tin-silicon molecular sieve is prepared by introducing tin element in a gas-solid phase in the presence of a template agent in the secondary hydrothermal treatment process of the silicon molecular sieve.

According to the method, in order to improve the catalytic oxidation activity of the tin-silicon molecular sieve prepared by the method, the temperature for mixing and contacting the tin source and the silicon molecular sieve in a solid phase is preferably 20-80 ℃, and more preferably 25-60 ℃.

According to the method of the present invention, the solid phase mixing and contacting of the tin source and the silicon molecular sieve can be carried out according to the contact conditions. The selectable range of the mixing and contacting time is wider, and in order to further improve the catalytic oxidation activity of the tin-silicon molecular sieve, the mixing and contacting time of the tin source and the silicon molecular sieve is further preferably 1-240 min, and more preferably 5-120 min.

According to the method, in order to further improve the catalytic activity of the tin-silicon molecular sieve prepared by the method, the silicon molecular sieve and the tin source are preferably used in amounts such that the mass ratio of tin element to silicon element in the prepared tin-silicon molecular sieve is 0.05-10: 100, preferably 0.1-5: 100, and more preferably 0.5-2: 100.

The purpose of the invention can be realized according to the technical scheme, the selectable ranges of the dosage of the silicon molecular sieve, the template agent, the tin source and the water are wide, and the silicon molecular sieve, the template agent, the tin source and the water are generally usedThe molar ratio of the silicon molecular sieve, the template agent, the tin source and the water is 100: 0.005-20: 0.0005-15: 2-1000, preferably 100: 0.005-20: 0.001-10: 2-500, and particularly preferably 100: 1-15: 0.1-8: 2-50, wherein the silicon molecular sieve is SiO₂The tin source is calculated by the element tin. In the preferred process of the present invention, the amount of water is preferably not more than the amount of saturated water vapor adsorbed by the molecular sieve. The system of the invention can basically provide enough saturated steam quantity for the space, but the rest water is less than the saturated adsorption quantity of the molecular sieve. In other words, the molecular sieve saturation adsorption amount is not exceeded, but it is generally satisfied that the reaction system is at saturation humidity (water vapor amount). This is why the reactor according to the invention is controlled to contain an amount of water which forms saturated water vapor under the reaction conditions and has a weight ratio to the molecular sieve of less than 1.2, the throughput of the molecular sieve being at least 10 g/l of reactor. For example, a 100ml container requires 0.5 g of water at saturation humidity, and the reaction can be carried out with 20 g of molecular sieve, or 1 g of molecular sieve. If the amount of water adsorbed by 1 g of molecular sieve is 0.2 g, 20 g of molecular sieve will not exceed 4 g of water at most, but at least 0.5 g.

According to the method of the present invention, the conditions for the hydrothermal crystallization treatment can be selected widely, and for the present invention, it is preferable that the crystallization conditions include: the crystallization temperature under the closed condition is 80-200 ℃, preferably 100-180 ℃, and more preferably 110-175 ℃; the time is 6-96 h, preferably 24-96 h.

According to the method of the present invention, the selection range of the type of the template agent is wide, and the selection range can be specifically selected according to the type of the tin-silicon molecular sieve to be prepared, and the skilled person can know the selection range. For the present invention, it is preferred that the template agent is one or more of tetraalkylammonium hydroxide, alcohol amine and alkylamine.

In the method of the present invention, the tetraalkylammonium hydroxide may be selected from a wide variety of types, and the tetraalkylammonium hydroxide commonly used in the art can achieve the object of the present invention, and for the present invention, it is preferable that the tetraalkylammonium hydroxide is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.

As mentioned above, the variety of the alkylamine in the present invention can be widely selected, and in the present invention, the alkylamine is preferably C2-C10 alkylamine, and more preferably the alkylamine is selected from the group consisting of those of the general formula R¹(NH₂)_nIn which R is¹Is C1-C6 alkyl or alkylene, n is 1 or 2, and the alkylamine is one or more of ethylamine, n-butylamine, butanediamine and hexanediamine.

As mentioned above, the variety of the alcohol amine in the present invention can be widely selected, and in the present invention, the alcohol amine is preferably C2-C5 alcohol amine, more preferably the alcohol amine is selected from the group consisting of alcohol amines represented by the general formula (HOR)²)_mNH_(3-m)Alcohol amine of (1), said R²Is C1-C4 alkyl; m is 1, 2 or 3; more preferably, the alcohol amine is one or more of monoethanolamine, diethanolamine and triethanolamine.

In the method provided by the invention, the tin source is one or more of inorganic tin compounds or organic tin compounds. For example, the tin source is preferably at least one of tin chloride, tin nitrate and tin acetate.

The recovery is well known to those skilled in the art and, in the process of the present invention, the product obtained may be dried and calcined without filtration. The drying and calcining methods are well known to those skilled in the art, for example, the drying of the obtained product is generally carried out at a temperature between room temperature and 200 ℃, and the rest conditions are also well known to those skilled in the art and will not be described herein.

The tin-silicon molecular sieve with hollow crystal grains prepared by the method has a diffraction peak at 0.5-9 degrees of 2 theta in an XRD (X-ray diffraction) pattern, and preferably has a diffraction peak at 5-9 degrees of 2 theta; 460cm in the FT-IR spectrum^-1、975cm^-1、800cm^-1、1080cm^-1Nearby absorption; the absorption is at 200-300 nm in the UV-Vis spectrum, and preferably at 200-260 nm. Therefore, the tin-silicon molecular sieve with hollow crystal grains has the basic characteristics of the tin-silicon molecular sieve.

Compared with a silicon molecular sieve containing no tin or a silicon molecular sieve loaded with tin, the tin-silicon molecular sieve has better catalytic oxidation activity, is particularly remarkable when being used for a phenol hydroxylation reaction, and presumably leads to the improvement of the selectivity of hydroquinone in a product due to a special structure.

The following examples further illustrate the invention but do not limit the scope of the invention.

In the comparative examples and examples, the reagents used were all commercially available analytical reagents.

Comparative examples and examples the silicalite used was, without particular indication, a sample of S-1 synthesized according to the prior art (method described in Nature, 1978, Vol.271, page 512).

In the invention, an X-ray diffraction (XRD) crystalline phase diagram of a sample is determined on a Siemens D5005 type X-ray diffractometer, a ray source is K α (Cu), the test range 2 theta is 0.5-30 degrees, and a Fourier infrared (FT-IR) spectrogram of the sample is determined on a Nicolet8210 type Fourier infrared spectrometer, wherein the test range is 400-1400 cm^-1. A sample solid ultraviolet-visible diffuse reflection spectrum (UV-vis) is measured on a SHIMADZUUV-3100 model ultraviolet-visible spectrometer, and the measuring range is 200-1000 nm. Total specific surface area, external specific surface area and pressure P/P relative to the sample₀Data such as the amount of nitrogen adsorbed at around 0.60 was measured on an ASAP2405 static nitrogen adsorber manufactured by Micromeritics according to the standard method ASTM D4222-98. TEM transmission electron micrograph of the sample is TecnaiG, FEI²Obtained on a transmission electron microscope of the F20S-TWIN type.

In the present invention, the analysis of each composition in the activity evaluation system is performed by gas chromatography, and the quantification is performed by a calibration and normalization method, which can be performed with reference to the prior art, and on the basis of which the evaluation indexes such as the conversion rate of the reactant and the selectivity of the product are calculated (see table 1 for specific results).

In the test example:

example 1

(1) Mixing a tin source and a silicon molecular sieve in a solid phase for 30min at 25 ℃ to obtain a mixture of the tin source and the silicon molecular sieve;

(2) adding a template solution into the mixture of the tin source and the silicon molecular sieve in the step (1) (in the contact process, water is added or not added according to the requirement, if the feeding of the step (1) can meet the feeding requirement of the water, the water is not needed, if the feeding of the step (1) can not meet the feeding requirement of the water, the water can be additionally added when the mixture containing tetrapropylammonium hydroxide, tin chloride and the silicon molecular sieve is stirred and contacted, other embodiments are similar, and the description is not repeated); wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), tin source (crystallized stannic chloride) and water (100: 10:0.5: 20), wherein the silicon source is SiO₂The tin source is calculated by the tin element;

(3) and (3) transferring the mixture obtained in the step (2) into a stainless steel sealed reaction kettle, crystallizing for 144 hours at the temperature of 170 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and then roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the mass percentage of tin is 1.8; the crystal grains are characterized as hollow structures by TEM; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, there is an absorption at 220nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Comparative example 1

This comparative example is a procedure for preparing a sample of TS-1 molecular sieve as described in Zeolite, 1992, Vol.12:943 to 950.

Tetraethyl orthosilicate 22.5 g and tetrapropylammonium hydroxide 7.0 g are mixed, and then distilled water 59.8 g is added, after uniform mixing, the mixture is hydrolyzed at 60 ℃ and normal pressure for 1.0 hour to obtain a tetraethyl orthosilicate hydrolyzed solution, a solution consisting of tetrabutyl titanate 1.1 g and anhydrous isopropanol 5.0 g is slowly added under vigorous stirring, and the obtained mixture is stirred at 75 ℃ for 3 hours to obtain a clear and transparent colloid. Placing the colloid in a stainless steel sealed reaction kettle, and standing at a constant temperature of 170 ℃ for 3 days to obtain a mixture of crystallized products; filtering the mixture, washing with water, drying at 110 deg.C for 60min to obtain TS-1 raw powder, and calcining the TS-1 raw powder at 550 deg.C for 3 hr to obtain TS-1 molecular sieve.

The Ti content by mass percentage is 2.6 by XRF composition analysis; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized by non-hollow structures through TEM; in FT-IR, 460cm^-1、800cm^-1、960cm^-1、1080cm^-1Nearby absorption; in UV-Vis, there is absorption at 210nm, the yield, total specific surface area, external specific surface area, the ratio of external specific surface area to total specific surface areaRatio and at relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Comparative example 2

The tin-silicon molecular sieve was prepared with reference to the method of comparative example 1, except that the titanium source was replaced by equimolar tin pentahydrate tetrachloride, which is a tin source, to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the mass percentage of Sn is 3.5; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized by non-hollow structures through TEM; in FT-IR, 460cm^-1、800cm^-1、970cm^-1、1080cm^-1Nearby absorption; in UV-Vis, absorption at 210nm, yield, total specific surface area, external specific surface area, proportion of external specific surface area to total specific surface area and relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Comparative example 3

Directly and mechanically mixing tin tetrachloride pentahydrate and S-1, and roasting (under the same roasting condition as in example 1) to obtain the tin-loaded silicon molecular sieve, wherein the mass percentage of Sn in the prepared tin-silicon molecular sieve is 1.9 due to the use amount of a tin source.

In an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized by non-hollow structures through TEM; in FT-IR, 460cm^-1、800cm^-1、1080cm^-1Nearby has absorption, and 970cm^-1No obvious absorption nearby; in UV-Vis, absorption is observed at 210nm, the yield, the total specific surface area, the external specific surface area, the ratio of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Comparative example 4

Directly and mechanically mixing tin tetrachloride pentahydrate with S-1 prepared according to the method in CN1338428A in example 1, and then roasting (the roasting condition is the same as that in example 1) to obtain the tin-loaded silicon molecular sieve, wherein the tin tetrachloride pentahydrate is used in an amount which enables the mass percentage content of Sn in the prepared tin-silicon molecular sieve to be 1.8.

In an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、1080cm^-1Nearby has absorption, and 970cm^-1No obvious absorption nearby; in UV-Vis, absorption at 210nm, yield, total specific surface area, external specific surface area, proportion of external specific surface area to total specific surface area and relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 2

(1) Mixing a tin source and a silicon molecular sieve in a solid phase for 60min at 25 ℃ to obtain a mixture of the tin source and the silicon molecular sieve;

(2) adding a template solution into the mixture of the tin source and the silicon molecular sieve in the step (1); wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), tin source (crystallized stannic chloride) and water (100: 15:0.1: 10), wherein the silicon source is SiO₂The tin source is calculated by the tin element;

(3) and transferring the mixture into a stainless steel sealed reaction kettle, crystallizing for 120 hours at the temperature of 160 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the mass percentage of Sn is 1.0; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; characterization of crystals by TEMThe particles are hollow structures; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, there is an absorption at 220nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 3

(1) Mixing a tin source and a silicon molecular sieve in a solid phase for 40min at 35 ℃ to obtain a mixture of the tin source and the silicon molecular sieve;

(2) adding a template solution into the mixture of the tin source and the silicon molecular sieve in the step (1); wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), tin source (tin nitrate) and water (100: 10:0.2: 5), wherein the silicon source is SiO₂The tin source is calculated by the tin element;

(3) and (3) transferring the mixture obtained in the step (2) into a stainless steel sealed reaction kettle, crystallizing for 96 hours at the temperature of 170 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the mass percentage content of Sn is 0.84; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, there is an absorption at 230nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 4

(1) Mixing a tin source and a silicon molecular sieve in a solid phase for 10min at 30 ℃ to obtain a mixture of the tin source and the silicon molecular sieve;

(2) adding a template solution into the mixture of the tin source and the silicon molecular sieve in the step (1); wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), tin source (crystallized stannic chloride) and water (100: 5:1: 40), wherein the silicon source is SiO₂The tin source is calculated by the tin element;

(3) and (3) transferring the mixture obtained in the step (2) into a stainless steel sealed reaction kettle, crystallizing for 72 hours at the temperature of 120 ℃ and under autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the mass percentage of Sn is 6.6; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, absorption is observed at around 240nm, the yield, the total specific surface area, the external specific surface area, the ratio of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 5

(1) Mixing a tin source and a silicon molecular sieve in a solid phase for 120min at 40 ℃ to obtain a mixture of the tin source and the silicon molecular sieve;

(2) adding a template solution into the mixture of the tin source and the silicon molecular sieve in the step (1); wherein,ensuring the feeding molar ratio of each substance as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), tin source (tin acetate) and water (100: 18:2: 10), wherein the silicon source is SiO₂The tin source is calculated by the tin element;

(3) and (3) transferring the mixture obtained in the step (2) into a stainless steel sealed reaction kettle, crystallizing for 24 hours at the temperature of 170 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and then roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the Sn mass percentage content is 5.3; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, there is an absorption at 230nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 6

(1) Mixing a tin source and a silicon molecular sieve in a solid phase for 180min at 25 ℃ to obtain a mixture of the tin source and the silicon molecular sieve;

(2) adding a template solution into the mixture of the tin source and the silicon molecular sieve in the step (1); wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), tin source (stannic chloride) and water (100: 11:1.5: 50), wherein the silicon source is SiO₂The tin source is calculated by the tin element;

(3) and (3) transferring the mixture obtained in the step (2) into a stainless steel sealed reaction kettle, crystallizing for 36 hours at the temperature of 170 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and then roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the Sn mass percentage content is 4.1; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, the absorption is carried out at 220-250 nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 7

The tin-silicon molecular sieve was prepared according to the method of example 6, except that the silicon source, the alkali source template, the tin source, and the water =100:1:12:15, to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the Sn mass percentage content is 9.6; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, the absorption is carried out at 230-260 nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 8

The tin-silicon molecular sieve was prepared according to the method of example 6, except that the tin source was replaced with tin acetate to obtain the tin-silicon molecular sieve.

By XRF compositional fractionSeparating out Sn, wherein the mass percentage of Sn is 3.5; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, the absorption is carried out at 230-260 nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Example 9

A tin silicalite molecular sieve was prepared as in example 6, except that the contacting temperature in step (1) was 10 ℃.

The prepared tin-silicon molecular sieve is analyzed by XRF composition, and the mass percentage of Sn is 2.8; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, absorption is at 240nm, the yield, the total specific surface area, the external specific surface area, the ratio of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Comparative example 5

The comparative example is used for illustrating that the tin-silicon molecular sieve is prepared by mixing all substances at the same time, and specifically comprises the following steps:

mixing, stirring and contacting tetrapropyl ammonium hydroxide aqueous solution (the concentration is 16 weight percent), a tin source and a silicon molecular sieve for 5 hours at the temperature of 60 ℃ to obtain a gel mixture; wherein, the feeding molar ratio of each substance is ensured as follows: silicon source (silicon molecular sieve), alkali source template agent (tetrapropylammonium hydroxide), tin source (stannic chloride pentahydrate) and water =100:10:0.5:200, wherein the silicon source is SiO₂The tin source is calculated by the tin element;

and transferring the mixture into a stainless steel sealed reaction kettle, crystallizing for 196h at the temperature of 170 ℃ and the autogenous pressure, filtering the obtained crystallized product, washing with water, drying for 120 minutes at the temperature of 110 ℃, and roasting for 3 hours at the temperature of 550 ℃ to obtain the tin-silicon molecular sieve.

By XRF composition analysis, the mass percentage of Sn is 1.4; in an XRD crystal phase diagram, diffraction peaks exist at positions with 2 theta of 5-9 degrees; the crystal grains are characterized as hollow structures by TEM; in FT-IR, 460cm^-1、800cm^-1、975cm^-1、1080cm^-1Nearby absorption; in UV-Vis, the absorption is at 230-250 nm, the yield, the total specific surface area, the external specific surface area, the proportion of the external specific surface area to the total specific surface area and the relative pressure P/P₀The data, such as the percentage of the difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption to the nitrogen adsorption amount at adsorption when the value is 0.60, are shown in table 1.

Test example

This test example is intended to illustrate the effectiveness of the molecular sieves prepared by the process of the present invention and the prior art processes for the catalytic oxidation of phenol hydroxylation.

The molecular sieves of the above examples and comparative examples were charged in a weight ratio of molecular sieve phenol to acetone =1:20:16, mixed uniformly in a three-necked flask with a condenser, heated to 80 ℃, and then, under stirring, added with 27.5 wt% aqueous hydrogen peroxide in a molar ratio of phenol to hydrogen peroxide =3:1, reacted at this temperature for 3 hours, and the resulting product was measured for phenol conversion on a 6890N type gas chromatograph using an HP-5 capillary column (30 m × 0.25 mm), and the results are shown in table 1.

As can be seen from table 1: compared with the common tin-silicon molecular sieve, the tin-silicon molecular sieve with hollow crystal grains prepared by the invention has higher hydroquinone selectivity in the phenol hydroxylation reaction than the tin-silicon molecular sieve prepared by the prior art; particularly, the tin-silicon molecular sieve prepared by the optimal method has better hydroquinone selectivity, catalytic oxidation activity and effective utilization rate of an oxidant. Meanwhile, the yield of the tin-silicon molecular sieve prepared by the optimal method is higher.

TABLE 1

Claims

1. The tin-silicon molecular sieve is characterized by containing silicon element, tin element and oxygen element, wherein all or part of crystal grains have a cavity or cavity structure, and the total specific surface area is more than or equal to 300m²The proportion of the external specific surface area to the total specific surface area is more than or equal to 10 percent.

2. The tin-silicon molecular sieve of claim 1, having an external specific surface area of 35m or more²/g。

3. The tin-silicon molecular sieve according to claim 1 or 2, wherein the total specific surface area is 310 to 600m²The external specific surface area is 35-100 m²And/g, wherein the proportion of the external specific surface area to the total specific surface area is 10-25%.

4. A tin-silicon molecular sieve according to claim 1 or 2 having an XRD pattern with a diffraction peak, in terms of 2 Θ, at 0.5 ° to 9 °; 460cm in the FT-IR spectrum^-1、975cm^-1、800cm^-1、1080cm^-1Nearby absorption; the absorption is at 200-300 nm in the UV-Vis spectrum.

5. The tin-silicon molecular sieve according to claim 1 or 2, wherein the mass ratio of the tin element to the silicon element is 0.05 to 10: 100.

6. The tin-silicon molecular sieve of claim 1, which is at 25 ℃, P/P₀The benzene adsorption amount measured under the condition of 0.10 and 1 hour of adsorption time is at least 35 mg/g.

7. The tin-silicon molecular sieve of claim 1, having a hysteresis loop between the adsorption isotherm and the desorption isotherm for low temperature nitrogen adsorption.

8. The tin-silicon molecular sieve of claim 1, which is at a relative pressure of P/P₀The difference between the nitrogen adsorption amount at desorption and the nitrogen adsorption amount at adsorption at 0.60 is greater than 2% of the nitrogen adsorption amount at adsorption.

9. The tin-silicon molecular sieve according to claim 1, wherein the crystal grains having a cavity or cavity structure inside the crystal grains account for 50% to 100% of the total crystal grains.

10. The tin-silicon molecular sieve of claim 1, wherein the radial length of the cavity portion inside the crystal grain is 0.5 to 300 nm.

11. The tin-silicon molecular sieve according to claim 1, wherein the shape of the hollow portion inside the crystal grains of the material is selected from one or a combination of rectangular, circular and irregular polygonal shapes.

12. The tin-silicon molecular sieve of claim 1, wherein the material grains are single grains or aggregated grains formed by aggregation of a plurality of grains.

13. A process for preparing the tin silicalite molecular sieve of any one of claims 1 to 12, characterized in that the process comprises:

(3) and (3) transferring the mixture obtained in the step (2) into a reaction kettle, carrying out hydrothermal treatment under the hydrothermal crystallization condition, wherein the reaction kettle contains water which forms saturated water vapor under the reaction condition and has a weight ratio with the molecular sieve of less than 1.2, the treatment capacity of the silicon molecular sieve is at least 10 g/l, and recovering the product to obtain the tin-silicon molecular sieve.

14. The method of claim 13, wherein said conditions for mixing a tin source with a silicon molecular sieve in a solid phase comprise: the mixing temperature is 20-80 ℃, and the mixing time is 1-240 min.

15. The process of claim 13 wherein said molecular sieve is at least one member selected from the group consisting of MFI, MEL, BEA, MWW, hexagonal two-dimensional structure, MOR, TUN structure molecular sieves.

16. The method of claim 13, wherein the silicon molecular sieve and the tin source are used in amounts such that the mass ratio of tin element to silicon element in the prepared tin-silicon molecular sieve is 0.05-10: 100.

17. The method of claim 13, wherein the molar ratio of the silicon molecular sieve, the template agent, the tin source and the water is 100: 1-15: 0.1-8: 2-50, and the silicon molecular sieve is SiO₂The tin source is calculated by the element tin.

18. The method of claim 13, wherein said hydrothermal crystallization conditions comprise: the temperature of the treatment under the closed condition is 80-200 ℃, and the time is 6-96 h.

19. A method according to any one of claims 13 to 17 wherein the source of tin is one or more of an inorganic tin compound or an organotin compound.

20. The method of claim 19, wherein the source of tin is at least one of tin chloride, tin chloride pentahydrate, tin nitrate, tin sulfate, tin phosphate, and tin acetate.

21. The method of claim 13, wherein the templating agent is one or more of tetraalkylammonium hydroxide, alcohol amine, and alkyl amine.