阅读说明：本技术 一种钝化钛硅沸石六配位钛物种的方法 (Method for passivating titanium silicalite hexacoordinate titanium species ) 是由 郭洪臣 王刚 于 2020-11-11 设计创作，主要内容包括：一种钝化钛硅沸石六配位钛物种的方法,属于沸石分子筛改性技术领域。含有六配位钛的钛硅沸石TS-1在紫外拉曼光谱上存在较强的归属于六配位钛物种的共振信号峰(～700cm～(-1))。在对所说的钛硅沸石TS-1用醇胺类化合物水溶液进行适当的水热处理之后,其紫外拉曼光谱上的六配位钛物种的共振信号峰基本消失。与此同时,处理后的钛硅沸石TS-1在丙烯和双氧水的液相环氧化反应中生成的副产物明显减少,环氧丙烷选择性明显提高。(A method for passivating titanium silicalite hexacoordinate titanium species belongs to the technical field of zeolite molecular sieve modification. The titanium silicalite TS-1 containing the hexacoordinate titanium has stronger resonance signal peak (700 cm) belonging to hexacoordinate titanium species on the ultraviolet Raman spectrum ‑1 ). After the titanium silicalite TS-1 is subjected to appropriate hydrothermal treatment by using an alcohol amine compound aqueous solution, the resonance signal peak of the hexacoordinate titanium species on the ultraviolet Raman spectrum basically disappears. Meanwhile, the by-products generated in the liquid phase epoxidation reaction of propylene and hydrogen peroxide of the treated titanium silicalite TS-1 are obviously reduced, and the selectivity of propylene oxide is obviously improved.)

1. A method of passivating a titanium silicalite hexacoordinated titanium species, comprising the steps of:

first, the titanium silicalite TS-1 parent body is pretreated

The pretreatment aims at removing a template agent and other organic matters adsorbed in the pore canal of the parent body of the titanium silicalite TS-1; the roasting temperature is 300-600 ℃; the roasting time is 0.5-48 hours;

secondly, hydro-thermal treatment modification is carried out on the pretreated titanium silicalite TS-1 matrix by alcohol amine solution

The hydrothermal treatment modification refers to modification treatment of the pretreated titanium silicalite TS-1 matrix by using an aqueous solution containing alcohol amine under the conditions that the hydrothermal treatment temperature is 50-200 ℃ and the hydrothermal treatment time is 2-72 hours; wherein the concentration of the alcohol amine is 0.001-0.4 mol/L, and the ratio of the titanium silicalite TS-1 matrix to the modification liquid is 1: 1-100 g/mL;

thirdly, carrying out conventional post-treatment on the modified TS-1

The post-treatment comprises solid-liquid separation, washing, drying and roasting; washing until the pH value is 7-9; the drying temperature is 50-150 ℃, the drying time is 6-24 hours, the roasting temperature is 300-600 ℃, and the roasting time is 1-100 hours.

2. The method of claim 1, wherein in the first step, the calcination temperature is 350-550 ℃; the roasting time is 3-12 hours.

3. The method of claim 1 or 2, wherein in the second step, the hydrothermal treatment temperature is 100 to 180 ℃ and the hydrothermal treatment time is 6 to 48 hours.

4. A method of passivating a titanium silicalite hexacoordinated titanium species according to claim 1 or 2, wherein in said second step, said alcohol amine is one or a mixture of more than two of monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, n-propanolamine, isobutanolamine, and n-butanolamine; the concentration of the alcohol amine is 0.005-0.2 mol/L; the ratio of the titanium silicalite TS-1 matrix to the modification liquid is 1: 5-20 g/mL.

5. The method of claim 3, wherein in the second step, the alcohol amine is one or a mixture of more than two of monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, n-propanolamine, isobutanolamine, and n-butanolamine; the concentration of the alcohol amine is 0.005-0.2 mol/L; the ratio of the titanium silicalite TS-1 matrix to the modification liquid is 1: 5-20 g/mL.

6. The method of passivating a titanium silicalite hexacoordinated titanium species according to claim 1, 2 or 5, wherein in said third step, the drying temperature is 80-120 ℃ and the drying time is 8-16 h; the roasting temperature is 350-550 ℃, and the roasting time is 3-48 h.

7. The method of claim 3, wherein in the third step, the drying temperature is 80-120 ℃ and the drying time is 8-16 h; the roasting temperature is 350-550 ℃, and the roasting time is 3-48 h.

8. The method of claim 4, wherein in the third step, the drying temperature is 80-120 ℃ and the drying time is 8-16 h; the roasting temperature is 350-550 ℃, and the roasting time is 3-48 h.

9. A process for the passivation of titanium silicalite hexacoordinated titanium species according to claim 1, 2, 5, 7 or 8, characterized in that the pretreatment of the first step and the calcination of the third step are carried out in an air atmosphere.

10. A process according to claim 6, wherein the pretreatment of the first step, the drying of the third step and the calcination are carried out in an air atmosphere.

Technical Field

The invention belongs to the technical field of zeolite molecular sieve modification, and relates to a method for passivating titanium silicalite hexacoordinate titanium species.

Background

Propylene Oxide (PO) is an important chemical intermediate, and polyether polyol and propylene glycol which are derivatives of the PO are widely applied to the industries of chemical industry, light industry, medicine, food, textile and the like. The prior industrial PO production process mainly comprisesChlorohydrin processes, co-oxidation processes, and direct epoxidation processes. The chlorohydrin method has the advantages of simple process, large operation load elasticity, low requirement on the purity of raw materials and higher economic benefit. However, the process equipment has serious corrosion, large three-waste discharge and serious environmental pollution, does not meet the requirement of green chemistry, and is listed in the development restriction line at present. The co-oxidation method overcomes the defect of serious environmental pollution of the chlorohydrin method, but has long process flow, large investment, product income influenced by co-products and limited industrial application. Titanium silicalite TS-1 is used as catalyst and hydrogen peroxide (H)₂O₂) The technology (HPPO process) for producing PO by propylene epoxidation of oxidant has the advantages of mild reaction conditions, high product yield, high atom utilization rate, few byproducts, environmental protection and the like, and is an important direction for the development of PO industrial production in the future. The titanium silicalite TS-1 catalyst is the technical core of the HPPO process. It is known that TS-1 was first synthesized by MacroTalamasso et al in 1981 (US 4410501). Through development and enrichment for forty years, the TS-1 hydrothermal synthesis method forms two main systems: namely a classical synthesis system and an inexpensive synthesis system. The classical synthesis system is a method for synthesizing TS-1 by using tetrapropylammonium hydroxide (TPAOH) as a template agent, and the following patents and published documents are related to the classical synthesis system: US 5656252 (application date: 1995, month 1 and 30), CN 1169952A (application date: 1996, month 7 and 10), CN 1217232A (application date: 1997, month 11 and 13), CN 1167082A (application date: 1997, month 12 and 10), CN 1245089A (application date: 1998, month 8 and 18), CN 1275530A (application date: 1999, month 5 and 28), CN 1275529A (application date: 1999, month 5 and 28), CN 1328878A (application date: 2000, month 1 and 2), CN 1418813A (application date: 2001, month 11 and 14), CN 1401569A (application date: 2002, month 8 and 26), CN 101190793A (application date: 2006, month 11 and 30), CN 101434400A (application date: 2007, month 11 and 5), CN 101327934A (application date: 2008, year 7 and 17) and the like, and Zeolite 1996,16,185, 195, Zeolite, 1997,19, 2003, and 245 porus, Meroleis and Meroleis, 66,143-. The cheap synthesis system is tetrapropylammonium bromide or other cheap mould with relatively low priceA method for synthesizing TS-1 by using a plate agent. The following patents and publications are related to inexpensive synthesis systems: US 5688484 (application date: 1996, 29/7), CN 1513760A (application date: 2002, 12/31), CN 101428814A (application date: 2007, 11/7/2009, CN 101767036A (application date: 2009, 12/25) etc. and Materials chemistry and physics 1997,47,225-.

A large number of basic studies indicate that the four-coordinate titanium species on the TS-1 zeolite is an active center in the epoxidation reaction of propylene and hydrogen peroxide. The four-coordination framework titanium has characteristic absorption of electron transition from oxygen ligand to titanium central atom near 210nm of ultraviolet visible diffuse reflection spectrum, and has characteristic absorption at 1120cm of ultraviolet Raman spectrum^-1Characteristic resonance absorption occurs nearby. In addition, the skeleton titanium also has a mid-infrared region of 960cm in the infrared spectrum^-1Characteristic absorption belonging to Si-O-Ti antisymmetric stretching vibration (or Si-O bond stretching vibration disturbed by framework titanium) appears nearby.

However, since the Ti-O bond is longer than the Si-O bond, it is difficult for the titanium atom to enter the silicate framework, and therefore TS-1 zeolite synthesized by either the classical method or the inexpensive method has more or less hexacoordinated titanium species present therein. Some of the hexacoordinated titanium species exist in the anatase form, which exhibit characteristic absorptions belonging to the electronic transition of the oxygen ligand to the titanium central atom in the vicinity of 350nm of the ultraviolet-visible diffuse reflectance spectrum. Some of the hexacoordinated titanium species exist in isolated or oligomeric form and have an ultraviolet Raman spectrum of 700cm^-1The resonance signals occurring in the vicinity are believed to be related to such hexacoordinated titanium species.

It is well known that a number of studies have shown that hexacoordinated titanium species are detrimental to low temperature oxidation reactions (including epoxidation reactions) using hydrogen peroxide as an oxidant. Thus, two well-defined approaches to addressing the hexacoordinated titanium species in titanium silicalite have been proposed:

the first method is to remove the hexacoordinated titanium species by acid washing titanium silicalite TS-1. For example, CN 1245090A (application date: 8/18/1998), CN 1657168A (application date: 2004, 12/9/2004), CN 101417238A (application date: 2008, 12/8/2009), CN 101591024A (application date: 2009, 6/23/2009) and the like all disclose a method for modifying TS-1 by acid washing. The representative technical characteristic is that TS-1 raw powder and an acidic compound solution are uniformly mixed, react for 5min to 6h at the temperature of 5 to 95 ℃, and then are subjected to post-treatment through filtering, washing, drying and roasting to obtain the modified TS-1 catalyst.

The second method is to convert the hexa-coordinated titanium into tetra-coordinated framework titanium by a hydrothermal recrystallization method. For example, the publications Microporous and Mesoporous Materials 2007,102,80-85 report a method of modifying TS-1 with an aqueous solution of tetrapropylammonium hydroxide. The preparation method comprises the steps of putting 1g of TS-1 molecular sieve in a mixed solution of 4.17mL of TPAOH (1M) and 3.32mL of water, crystallizing for 24h at 170 ℃ in a reaction kettle, and carrying out suction filtration, washing, drying and roasting for 16h at 520 ℃ to obtain the modified TS-1. This is a typical hydrothermal recrystallization method. The method is an effective method for solving the problem of the six-coordination titanium species.

However, the acid washing treatment can remove not only the hexacoordinated titanium species but also a part of the tetracoordinated skeletal titanium active centers. This makes the acid wash treatment unsatisfactory for solving the problem of hexacoordinated titanium species of titanium silicalite. The hydrothermal recrystallization method requires the use of more expensive tetrapropylammonium hydroxide template solution, which further increases the cost of the titanium silicalite.

Disclosure of Invention

The invention provides a method for selectively passivating hexacoordinate titanium species in titanium silicalite by using an alcohol amine solution with low price. We have surprisingly found through a large number of scientific researches that titanium silicalite TS-1 containing hexacoordinated titanium has a strong resonance signal peak (700 cm) belonging to hexacoordinated titanium species on an ultraviolet Raman spectrum^-1). After the titanium silicalite TS-1 is subjected to appropriate hydrothermal treatment by using an alcohol amine compound aqueous solution, the resonance signal peak of the hexacoordinate titanium species on the ultraviolet Raman spectrum basically disappears. Meanwhile, the treated titanium silicalite TS-1 is subjected to liquid-phase epoxidation reaction of propylene and hydrogen peroxideThe by-products generated in the reaction are obviously reduced, and the selectivity of the propylene oxide is obviously improved. Therefore, the modification treatment method has the value of remarkably improving the technical performance of the titanium silicalite catalyst.

The technical scheme of the invention is as follows:

in the first step, the titanium silicalite TS-1 matrix is pretreated. The purpose is to remove the template agent and other organic matter adsorbed in the pore channels. The pretreatment is carried out in an air atmosphere. The roasting temperature is 300-600 ℃, and preferably 350-550 ℃; the roasting time is 0.5 to 48 hours, preferably 3 to 12 hours.

The titanium silicalite TS-1 can be a product synthesized by a classical method or a product synthesized by a cheap method. The titanium silicalite precursors can be obtained by hydrothermal synthesis by engineers familiar with the art according to the methods disclosed in the publications and patent literature.

And secondly, carrying out hydrothermal treatment modification on the pretreated titanium silicalite TS-1 matrix by using an alcohol amine solution. The hydrothermal treatment modification refers to using an aqueous solution containing alcohol amine, and the hydrothermal treatment temperature is 50-200 ℃, preferably 100-180 ℃; the modification treatment is carried out on the pretreated titanium silicalite TS-1 matrix under the condition that the hydrothermal treatment time is 2-72 h, preferably 6-48 h. The alcohol amine is selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, n-propanolamine, isobutanolamine, n-butanolamine, and mixtures thereof. Wherein, the concentration of the alcohol amine is 0.001-0.4 mol/L, preferably 0.005-0.2 mol/L. The ratio (mL) of the titanium silicalite TS-1 matrix (g) to the modification solution is 1: 1-1: 100, preferably 1: 5-1: 20.

And thirdly, carrying out conventional post-treatment on the modified titanium silicalite TS-1. The post-treatment comprises solid-liquid separation, washing, drying and roasting. Wherein, the solid-liquid separation comprises centrifugal separation or filtration; washing until the pH value is 7-9; and drying is carried out in an air atmosphere at the temperature of 50-150 ℃ for 6-24 h, preferably 80-120 ℃ for 8-16 h. The roasting is carried out in an air atmosphere at the temperature of 300-600 ℃ for 1-100 h, preferably 350-550 ℃ for 3-48 h.

The effects of the present invention can be evaluated by the following methods:

1. ultraviolet Raman spectroscopy:

the method enables reliable discrimination between the hexacoordinated titanium species and the tetracoordinated titanium species of titanium silicalite TS-1. The resonance signal of the hexacoordinate titanium species on the ultraviolet Raman spectrum is located at 700cm^-1Nearby, and the resonance signal of the four-coordinate titanium species is at 1120cm^-1Nearby. Engineers familiar with the art can refer to the published article "chem. eur.j.2012,18, 13854-13860" to collect uv raman spectra of TS-1 samples using a 266nm excitation light source.

2. Evaluation method of reactivity:

this is an evaluation method of auxiliary ultraviolet raman spectroscopy. The liquid phase epoxidation reaction of propylene and hydrogen peroxide is sensitive to titanium silicalite hexacoordinate titanium species, so that the method is suitable for being used as an auxiliary evaluation method. The recommended method is as follows: firstly, 0.4g of TS-1 catalyst is added into a stainless steel batch reaction kettle, and then H with the concentration of 3mol/L is added₂O₂40mL of methanol solution. Then, the reaction vessel was closed, air was repeatedly replaced with propylene, and the reaction was carried out at 50 ℃ for 2 hours while stirring while maintaining the propylene pressure at 0.6 MPa. The conversion rate of hydrogen peroxide is determined by iodometry, and the selectivity of the propylene oxide is analyzed by gas chromatography. The passivation effect of the alcohol amine solution can be judged by comparing the reaction result of the unmodified parent zeolite and the reaction result of the modified zeolite after hydrothermal treatment. The above methods are reported in a large number of publications and patent documents, and the specific procedures can be selected by an engineer skilled in the art.

The invention has the effect and benefit that the aim of selectively passivating the titanium silicalite TS-1 hexacoordinate titanium species is achieved by utilizing the hydrothermal treatment of a relatively cheap alcohol amine solution. For the preparation of commercial catalysts of titanium silicalite this means that the synthesis conditions for the titanium silicalite precursor can be relaxed, making it possible to prepare the catalyst with inexpensive TS-1 zeolite. In addition, the molecular weight of the used alcohol amine is small, the structure is simple, so the method can be suitable for other types of titanium silicalite, and the treated titanium silicalite can be used for other types of low-temperature oxidation reaction taking hydrogen peroxide as an oxidant.

Drawings

FIG. 1 is a UV Raman spectrum of a TS-1 sample collected using a 266nm excitation light source.

Detailed Description

The present invention will be described in further detail with reference to examples, but the scope of the present invention is not limited by the examples.

Example 1:

according to the patent CN 1401569A, titanium silicalite TS-1 is synthesized, and then the titanium silicalite TS-1 is roasted for 6 hours at 540 ℃ in the air atmosphere to remove a template agent, so that a TS-1 matrix is obtained. 0.19g ethanolamine was added to 100g deionized water to prepare a modified solution. Mixing 10g of TS-1 matrix and 100mL of modified solution, stirring for 30min, placing in a crystallization kettle, and performing hydrothermal treatment at 170 ℃ for 24 h. And (3) carrying out centrifugal separation, washing with water until the pH value is 8, drying at 110 ℃ for 12h, and roasting at 540 ℃ for 6h to obtain the modified TS-1 catalyst. And adopting a 266nm excitation light source to acquire an ultraviolet Raman spectrum of the TS-1 sample. As shown in FIG. 1, the UV Raman characteristic peak (700 cm) of the modified ethanolamine TS-1^-1) The signal becomes weaker. 0.4g of modified TS-1 catalyst is added into a stainless steel batch reactor, and then H with the concentration of 3mol/L is added₂O₂40mL of methanol solution. Then, the reaction vessel was closed, air was repeatedly replaced with propylene, and the reaction was carried out at 50 ℃ for 2 hours while stirring while maintaining the propylene pressure at 0.6 MPa. The conversion rate of hydrogen peroxide determined by iodometry is 77.36%, and the selectivity of propylene oxide analyzed by gas chromatography is 76.11%.

Comparative example 1

0.4g of TS-1 catalyst precursor is added into a stainless steel batch reactor, and then H with the concentration of 3mol/L is added₂O₂40mL of methanol solution. Then, the reaction vessel was closed, air was repeatedly replaced with propylene, and the reaction was carried out at 50 ℃ for 2 hours while stirring while maintaining the propylene pressure at 0.6 MPa. The conversion rate of the hydrogen peroxide is 76.56%, and the selectivity of the propylene oxide is 64.85%.

Example 2:

example 1 was repeated except that ethanolamine was changed to diethanolamine. The conversion rate of the hydrogen peroxide is 76.58%, and the selectivity of the propylene oxide is 74.37%.

Example 3:

example 1 was repeated except that ethanolamine was changed to isopropanolamine. The conversion rate of the hydrogen peroxide is 78.67%, and the selectivity of the propylene oxide is 79.18%.

Example 4:

example 1 was repeated except that 0.03g of ethanolamine was added to 100g of deionized water to prepare a modified solution. The conversion rate of the hydrogen peroxide is 77.08 percent, and the selectivity of the propylene oxide is 69.15 percent.

Example 5:

example 1 was repeated except that 2.44g of ethanolamine was added to 100g of deionized water to prepare a modified solution. The conversion rate of the hydrogen peroxide is 76.6 percent, and the selectivity of the propylene oxide is 79.15 percent.

Example 6:

example 1 was repeated except that ethanolamine was changed to isopropanolamine and the hydrothermal treatment was carried out for 6 h. The conversion rate of the hydrogen peroxide is 79.57 percent, and the selectivity of the propylene oxide is 70.20 percent.

The characterization result and the reaction data jointly show that six-coordinate titanium species can be passivated by the ethanol amine modification treatment TS-1, and the selectivity of propylene oxide is improved.

The above description is only for a part of specific embodiments, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution of the present invention and its inventive concept within the technical scope of the present invention.