CN100344375C - Synthesis method of titanium-containing molecular sieve - Google Patents

Abstract

A method for synthesizing titanium-containing molecular sieves belongs to the technical field of inorganic chemical synthesis. Using silica gel or silica sol as the silicon source, organic titanate as the titanium source, and a cyclic molecular amine-hexamethyleneimine or piperidine or a mixture of the two as the organic template, through the synthesis of the directing agent, the reaction Preparation of the mixed solution, hydrothermal crystallization, and conventional filtering, washing, drying, and roasting to obtain TS-1 molecular sieve. The method has the advantages of adopting cheap cyclic molecular amine as the organic template agent, low production cost, good reproducibility by introducing the directing agent, and less pollutant emission in the synthesis process.

Description

A kind of synthetic method of titanium-containing molecular sieve

                      

The invention relates to a method for synthesizing a titanium-containing molecular sieve, specifically, a method for synthesizing a TS-1 molecular sieve, and belongs to the technical field of inorganic chemical synthesis.

Background technique

Since Taramasso et al. (US 4,410,501) first reported in 1983, TS-1 molecular sieve has attracted widespread attention due to its excellent catalytic oxidation performance. At present, the mild reaction system using TS-1 molecular sieve as catalyst and dilute H ₂ O ₂ as oxidant has excellent performance in organic oxidation reactions such as olefin epoxidation, aromatic hydrocarbon hydroxylation, ketone ammonia oximation, alkane oxidation and alcohol oxidation. High activity, selectivity, and an environmentally friendly green chemical process in which the by-product is only water, so TS-1 molecular sieve is known as a milestone in molecular sieve catalysis in the 1980s.

At present, the typical method for the synthesis of TS-1 molecular sieve is to use organic silicon ester and organic titanium ester as silicon source and titanium source respectively, and use tetrapropyl ammonium hydroxide (TPAOH) as template agent under certain temperature and pressure. Hydrothermal synthesis, and the product is obtained through conventional separation, washing, drying and roasting procedures. Because the template agent tetrapropylammonium hydroxide (TPAOH) is used in a large amount and is expensive, the cost of the synthesized TS-1 molecular sieve is relatively high, which is very unfavorable for the application of the molecular sieve in industry.

In order to reduce costs and avoid using TPAOH as a template, Müller et al. (Stud.Surf.Sci.Catal., 1994, 84:203-210) proposed to use tetrapropylammonium bromide (TPABr) as a template and ammonia as an alkali source Substitute TPAOH for the preparation of titanium silicon molecular sieve TS-1. Later, TS-1 molecular sieves were synthesized by TPABr+hexamethylenediamine, TPABr+n-butylamine, TPABr+methylamine, TPABr+ammonia, TPAOH+TBAOH, TEAOH+TBAOH and other systems. It can be seen that the templates used in the synthesis are basically quaternary ammonium salts as the main template, and so far there has been no report on the use of cyclic molecular amines as templates in the synthesis.

Contents of the invention

The object of the present invention is to provide a kind of synthetic method of TS-1 molecular sieve, and its advantage is, make template with the mixture of cheap cyclic molecule amine-hexamethyleneimine (HMI) or piperidine (PI) Agents are used to synthesize TS-1 molecular sieves, and the production cost is significantly reduced.

The present invention adopts the following technical solutions to achieve the above object:

Using silica gel or silica sol as the silicon source, organic titanate as the titanium source, and a cyclic molecular amine-hexamethyleneimine or piperidine or a mixture of the two as the organic template, through the synthesis of the directing agent, the reaction Preparation of the mixed solution, hydrothermal crystallization, and conventional filtering, washing, drying, and roasting to obtain TS-1 molecular sieve.

The technical solution of the present invention is now described in detail. A kind of synthetic method of TS-1 molecular sieve,

Steps:

Synthesis of the first step directing agent

The molar ratio of SiO ₂ in the silicon source: organic base template agent: TiO ₂ in the titanium source: H ₂ O is 1: (0.05-0.2): (0-0.1): (5-90), prepare the reaction mixture , at 50-60°C, hydrolyze into gel for 0.5-1 hour, then raise the temperature of the reaction mixture to 75-85°C, and chase the alcohol for 3-4 hours to prepare the directing agent. The silicon source is tetraethyl silicate, The titanium source is tetrabutyl titanate, and the organic base template is tetrapropylammonium hydroxide;

Preparation of the second reaction mixture

The molar ratio of SiO ₂ in the silicon source: organic template: TiO ₂ in the titanium source: H ₂ O is 1: (0.1-4): (0.005-0.2): (5-90), prepare the mixture solution, first Mix the organic templating agent with water evenly, add the titanium source while stirring, add the silicon source after the hydrolysis is complete, stir evenly, and then add the guiding agent prepared in the first step, the addition amount is 0.1% to 20% of the weight of _SiO2 in the silicon source % to form a reaction mixture, the silicon source is silica gel or silica sol, the titanium source is organic titanate, its general formula is Ti(OR ² ) ₄ , wherein R ² is the alkyl group;

The third step of hydrothermal crystallization

Transfer the reaction mixture prepared in the second step to a high-pressure reactor, conduct hydrothermal crystallization at 130-200°C for 1-6 days, and obtain the product after conventional filtration, washing, drying and roasting, TS-1 molecular sieve;

It is characterized in that the templating agent described in the second step is hexamethyleneimine or piperidine or a mixture of hexamethyleneimine and piperidine.

A further feature of the present invention is that the operation steps:

Preparation of the second reaction mixture

The molar ratio of SiO ₂ in the silicon source: organic template agent: TiO ₂ in the titanium source: H ₂ O is 1: (0.5-2): (0.01-0.1): (10-50), and the first step is prepared The addition of the directing agent is 1% to 10% of the weight of _SiO in the silicon source;

The third step of hydrothermal crystallization

Hydrothermal crystallization at 160-180°C for 2-6 days.

Compared with the prior art, the technology of the present invention has the following significant advantages:

1. Use cheap cyclic molecular amines as organic templates, silica gel or silica sol as silicon source, which reduces production costs;

2. The introduction of guiding agent has good repeatability;

3. Less pollutant discharge in the synthesis process.

Description of drawings

Fig. 1 is the XRD spectrogram of the molecular sieve synthesized in Example 1 before roasting. The XRD measurement is carried out on a German Bruker axs X-ray diffractometer, using CuK diffraction, and the scanning range is 2θ=5～35°. It can be seen from the XRD spectrum that strong diffraction peaks appear at 2θ=7.8°, 8.8°, 23.2°, 23.8°, 24.3°, etc., indicating that it has an MFI structure.

Fig. 2 is an infrared spectrum (IR) chart of the molecular sieve synthesized in Example 1 after being calcined at 550° C. for 8 hours. IR spectral analysis was carried out on a NEXUS 670 FT-IR spectrometer from Nicolet Company of the United States, and KBr pellets were used. It can be seen from the IR spectrum that a strong absorption peak appears at 960cm ^-1 , indicating that Ti atoms have entered the molecular sieve framework.

Detailed ways

All embodiments are operated according to the operation steps of the above-mentioned technical solutions.

Example 1

Synthesis of the first step directing agent

The molar ratio of SiO ₂ in tetraethyl silicate : tetrapropylammonium hydroxide : TiO ₂ in tetrabutyl titanate : H ₂ O is 1:0.1:0.04:20, and the reaction mixture is prepared at 60°C Carry out hydrolysis to form a gel for 0.5-1 hour, then raise the temperature to 80°C, and wash off the alcohol for 4 hours to prepare the directing agent;

Preparation of the second reaction mixture

The silicon source is silica gel, the titanium source is tetrabutyl titanate, the template is hexamethyleneimine, and the molar ratio of SiO ₂ in the silicon source: organic base template agent: TiO ₂ in the titanium source: H ₂ O is 1: 1: 0.033: 12 prepare the mixture solution, add _SiO in the silicon source 3% of the directing agent obtained in the previous step by weight, form a reaction mixture;

The third step of hydrothermal crystallization

Hydrothermal crystallization at 170°C for 4 days to obtain TS-1 molecular sieve.

The XRD spectrum of TS-1 molecular sieve is shown in Figure 1, and the IR spectrum is shown in Figure 2.

Example 2

Implementation process is except following difference, and all the other are all the same with embodiment 1:

Synthesis of the first step directing agent

The molar ratio of SiO ₂ in the silicon source:organic alkali template:TiO ₂ in the titanium source:H ₂ O is 1:0.2:0.1:80;

Preparation of the second reaction mixture

The organic template is a mixture of hexamethyleneimine and piperidine, and the molar ratio of the two is 5:5.

The XRD spectrum of TS-1 molecular sieve is similar to Figure 1, and the IR spectrum is similar to Figure 2.

Example 3

Implementation process is except following difference, and all the other are all the same with embodiment 1:

Preparation of the second reaction mixture

The organic template is piperidine, and 15% of the directing agent prepared in the previous step based on the weight of _SiO2 in the silicon source is added to form a reaction mixture.

The XRD spectrum of TS-1 molecular sieve is similar to Figure 1, and the IR spectrum is similar to Figure 2.

Example 4

Implementation process is except following difference, and all the other are all the same with embodiment 1:

Preparation of the second reaction mixture

The silicon source is silica sol, and the directing agent obtained in the previous step based on _SiO in the silicon source by weight 8% is added to form a reaction mixture;

The third step of hydrothermal crystallization

Hydrothermal crystallization at 170°C for 6 days to obtain TS-1 molecular sieve.

The XRD spectrum of TS-1 molecular sieve is similar to Figure 1, and the IR spectrum is similar to Figure 2.

Example 5

Implementation process is except following difference, and all the other are all the same with embodiment 1:

Preparation of the second reaction mixture

SiO ₂ in the silicon source: organic base template agent: TiO ₂ in the titanium source: H ₂ O in molar ratio 1: 0.6: 0.02: 12 to prepare a mixture solution;

The third step of hydrothermal crystallization

Hydrothermal crystallization at 160°C for 5 days to obtain TS-1 molecular sieve.

The XRD spectrum of TS-1 molecular sieve is similar to Figure 1, and the IR spectrum is similar to Figure 2.

Example 6

Implementation process is except following difference, and all the other are all the same with embodiment 2:

Preparation of the second reaction mixture

SiO ₂ in the silicon source: organic base template agent: TiO ₂ in the titanium source: H ₂ O in the molar ratio of 1: 1.5: 0.02: 20 to prepare a mixed solution;

The third step of hydrothermal crystallization

Hydrothermal crystallization at 180°C for 3 days to obtain TS-1 molecular sieve.

The XRD spectrum of TS-1 molecular sieve is similar to Figure 1, and the IR spectrum is similar to Figure 2.

Example 7

Implementation process is except following difference, and all the other are all the same with embodiment 1:

The titanium source is tetraethyl titanate, the organic template is a mixture of hexamethyleneimine and piperidine, and the molar ratio of the two is 8:2.

The third step of hydrothermal crystallization

Hydrothermal crystallization at 160°C for 5 days to obtain TS-1 molecular sieve.

The XRD spectrum of TS-1 molecular sieve is similar to Figure 1, and the IR spectrum is similar to Figure 2.

Example 8

Implementation process is except following difference, and all the other are all the same with embodiment 2:

Preparation of the second reaction mixture

SiO ₂ in the silicon source: organic base template agent: TiO ₂ in the titanium source: H ₂ O in the molar ratio of 1: 1.5: 0.02: 10 to prepare a mixed solution;

The third step of hydrothermal crystallization

Hydrothermal crystallization at 180°C for 2 days to obtain TS-1 molecular sieve.

The XRD spectrum of TS-1 molecular sieve is similar to Figure 1, and the IR spectrum is similar to Figure 2.

The method of the present invention is particularly suitable for preparing TS-1 molecular sieves.

Claims (2)

1, a kind of synthetic method of TS-1 molecular sieve, operating procedure:

Synthesizing of first step directed agents

SiO in the silicon source in molar ratio ₂: organic base template agent: the TiO in the titanium source ₂: H ₂O is 1: (0.05～0.2): (0～0.1): (5～90), the preparation reaction mixture, be hydrolyzed into glue under 50～60 ℃ 0.5～1 hour, reactant mixture is warming up to 75～85 ℃ again, caught up with alcohol 3～4 hours, and made directed agents, described silicon source is a tetraethyl orthosilicate, described titanium source is a butyl titanate, and the agent of described organic base template is a TPAOH;

The preparation of the second step reactant mixture

SiO in the silicon source in molar ratio ₂: organic formwork agent: the TiO in the titanium source ₂: H ₂O is 1: (0.1～4): (0.005～0.2): (5～90), and preparating mixture solution mixes organic formwork agent and water earlier, stir adding titanium source down, hydrolysis back fully adds the silicon source, stirs, add the directed agents that the first step makes again, addition is SiO in the silicon source ₂0.1%～20% of weight forms reactant mixture, and described silicon source is silica gel or Ludox, and described titanium source is an organic titanate, and its general formula is Ti (OR ²) ₄, R wherein ²For having the alkyl of 2～6 carbon atoms;

The 3rd step hydrothermal crystallizing

Second reactant mixture that make of step is transferred in the autoclave, 130～200 ℃ of following hydrothermal crystallizings 1～6 day, after the filtration of routine, washing, drying, roasting product, the TS-1 molecular sieve;

It is characterized in that the template agent described in second step is the mixture of hexamethylene imine or piperidines or hexamethylene imine and piperidines.

2, the synthetic method of TS-1 molecular sieve according to claim 1 is characterized in that, operating procedure:

The preparation of the second step reactant mixture

SiO in the silicon source in molar ratio ₂: organic formwork agent: the TiO in the titanium source ₂: H ₂O is 1: (0.5～2): (0.01～0.1): the addition of the directed agents that (10～50), the first step make is SiO in the silicon source ₂1%～10% of weight;

The 3rd step hydrothermal crystallizing

160～180 ℃ of following hydrothermal crystallizings 2～6 days.

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