Catalyst for preparing chlorine through catalytic oxidation of hydrogen chloride

Abstract

The invention discloses a catalyst for preparing chlorine by catalytic oxidation of hydrogen chloride. The catalyst takes titanium dioxide as a carrier and ruthenium species as an active component. The titanium dioxide carrier has a hollow sphere structure, and the active component ruthenium is loaded on the hollow sphere structure. According to the catalyst with the hollow sphere structure, the hollow structure is constructed, so that gaps uniformly exist among catalyst particles, a catalyst bed layer formed by stacking the catalyst particles with the hollow sphere structure has bed layer gaps compared with a catalyst bed layer formed by stacking a solid structure, the gaps are uniform, reaction heat is not easy to accumulate, the reaction heat can be quickly dispersed and guided out, and the reaction efficiency is improved. Compared with a traditional supported titanium dioxide supported ruthenium-based catalyst, the catalyst effectively relieves sintering, agglomeration and inactivation of the active component ruthenium due to reaction heat release and high bed temperature, so that high catalytic activity and catalytic stability of the catalyst are guaranteed, and the reaction conversion rate of preparing chlorine through catalytic oxidation of hydrogen chloride is increased.

Description

Technical Field

[0001] The invention relates to a catalyst for preparing chlorine by catalytic oxidation of hydrogen chloride. Background Art

[0002] Chlorine is an important chemical raw material and is widely used in the production of chlor-alkali, polyurethane, pesticide, and pharmaceutical chemical industries. However, the utilization rate of chlorine in the production process is not high, and the same volume of hydrogen chloride gas is usually produced as a by-product. The excess of by-product hydrogen chloride in the chlor-alkali industry has always been a problem that has plagued the entire industry. The outlet and utilization of a large amount of by-product hydrogen chloride have become a common problem that restricts the development of many industries such as polyurethane, chlor-alkali, organic fluorine, pesticide, and pharmaceutical chemicals. Therefore, if the large amount of hydrogen chloride that is a by-product in industry and difficult to handle can be directly converted into chlorine for utilization, the closed-loop circulation of chlorine and zero emission of the reaction process can be achieved, which can not only solve the problem of excess hydrogen chloride in related industries, but also meet the growing demand for chlorine in industry to a certain extent, promote the healthy development of emerging industries and the optimization and upgrading of the chlor-alkali industry, and meet the overall requirements of sustainable development of the industry.

[0003] The research on the conversion of hydrogen chloride into chlorine has a history of more than 100 years. So far, the preparation of chlorine from hydrogen chloride is mainly achieved through three processes: electrolysis, direct oxidation and catalytic oxidation. In the early days, electrolysis or direct oxidation was used to convert HCl into Cl 2 The electrolysis method has the disadvantages of high energy consumption and high impurity content in the product, and is gradually being eliminated. The direct oxidation method uses a strong oxidant such as NO 2 、SO 3 or HNO 3 / H 2 SO 4 The mixed acid is used as an oxidant to directly oxidize hydrogen chloride. This method has complex equipment, is difficult to separate the product, and has relatively high energy consumption, so it has not been promoted.

[0004] The catalytic oxidation method is widely considered to be the most easily industrialized method at this stage due to its advantages such as low energy consumption, simple and easy operation, and high single-pass conversion rate. The core of the process of catalytic oxidation of hydrogen chloride to produce chlorine lies in the research and development of catalysts. Ruthenium-based catalysts have higher reaction activity at lower reaction temperatures, among which ruthenium-based catalysts supported by titanium dioxide have the best performance. However, since a large amount of heat is released during the reaction, the active components sinter and the reaction activity is reduced. Improving the thermal conductivity of the catalyst and delaying the sintering of the active components are the key to improving the stability of ruthenium-based catalysts. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a catalyst with a hollow sphere structure for catalytic oxidation of hydrogen chloride, which can effectively alleviate the excessively high temperature of the catalyst bed, is conducive to timely discharge of reaction heat, prevents sintering of active components, and has high catalytic activity, good stability and long service life.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A catalyst for catalytic oxidation of hydrogen chloride to prepare chlorine, wherein the catalyst uses titanium dioxide as a carrier and a ruthenium species as an active component; the catalyst is characterized in that the titanium dioxide carrier is a hollow sphere structure and the active component ruthenium is loaded on the hollow sphere structure.

[0008] The particle size of the titanium dioxide in the hollow sphere structure is 10 to 200 mm.

[0009] Preferably, in the catalyst, the active component is ruthenium oxide, and the ruthenium element accounts for 0.1-5.0wt% of the total mass of the catalyst. More preferably, the ruthenium element accounts for 0.5-3.0wt% of the total mass of the catalyst. The active sites at this mass content of the active component are sufficient for the catalytic oxidation reaction of hydrogen chloride and oxygen.

[0010] Preferably, the titanium dioxide is rutile titanium dioxide.

[0011] The method for preparing chlorine by catalytic oxidation of hydrogen chloride using the catalyst of the present invention comprises the following steps:

[0012] (1) an activation step of the catalyst;

[0013] (2) Hydrogen chloride and oxygen are contacted with the activated catalyst for reaction, the volume ratio of hydrogen chloride to oxygen is 1:(0.5-6), and the reaction temperature is 200-800°C.

[0014] The activation step comprises: in a nitrogen atmosphere, heating from room temperature to 100-200° C. at a heating rate of 1-20° C. / min, and then heating to the reaction temperature at a heating rate of 0.5-5° C. / min.

[0015] In step (2), a reaction diluent gas is introduced, wherein the reaction diluent gas is nitrogen.

[0016] The catalyst is loaded in a fixed bed reactor, and the fixed bed reactor may use a Hastelloy tube.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The catalyst of the present invention is a hollow spherical titanium dioxide loaded ruthenium species, which has a unique hollow spherical structure and is more 2 / TiO 2The catalytic bed formed by the accumulation of catalyst particles with a nanometer-scale hollow sphere structure of the present invention has a catalytic bed formed by the accumulation of catalyst particles with a hollow sphere structure, which has a bed gap and a uniform gap compared with the catalyst bed formed by the accumulation of solid structure, is not easy to accumulate reaction heat, and can disperse and guide the reaction heat more quickly. Compared with the traditional supported titanium dioxide supported ruthenium-based catalyst, the catalyst effectively alleviates the sintering and agglomeration deactivation of the active component ruthenium due to the heat release of the reaction and the high bed temperature, thereby ensuring the high catalytic activity and catalytic stability of the catalyst and improving the reaction conversion rate of catalytic oxidation of hydrogen chloride to prepare chlorine; and the nanometer-scale hollow sphere TiO 2 , which is conducive to the dispersion of the active component ruthenium oxide on the surface of titanium dioxide, and obtains better activity in the catalytic oxidation reaction of hydrogen chloride. Compared with the traditional supported titanium dioxide supported ruthenium-based catalyst, it shows better catalytic performance in the catalytic oxidation of hydrogen chloride to produce chlorine. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A model diagram of the catalyst obtained in the preparation example of the present invention is given. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0021] Catalyst Preparation Example

[0022] The method for preparing a high thermal conductivity catalyst for catalytic oxidation of hydrogen chloride provided by the present invention comprises the following steps:

[0023] (1) Preparation of SiO 2 ball

[0024] (1-1) adding a silicon dioxide precursor to a mixture of 5 ml of deionized water and 20 ml of ethanol to prepare a solution A; the silicon dioxide precursor is at least one of sodium silicate, TEOS, and silica sol;

[0025] (1-2) Add 1 ml of 40% ammonia water to the above solution A, stir and mix to obtain a silica precipitate;

[0026] (1-3) The above silicon dioxide precipitate was centrifuged and washed with ethanol to obtain SiO 2 ball;

[0027] (1-4) The washed silica precipitate is dispersed again in an ethanol solution to prepare a dispersion B.

[0028] (2) Dissolve 0.5 g of hydroxypropyl cellulose in 100 ml of a mixture of ethanol and deionized water, stir and mix well to prepare solution C;

[0029] (3) Preparation of core-shell TiO 2 @SiO 2 , the @ refers to the load.

[0030] (3-1) Dispersion liquid B and solution C are mixed to obtain dispersion liquid D;

[0031] (3-2) adding a titanium dioxide precursor to 20 ml of an ethanol solution to obtain a solution E; the titanium dioxide precursor is at least one of tetrabutyl titanate, titanium tetrachloride, and titanium hydroxide;

[0032] (3-3) injecting solution E into dispersion D and stirring at 60 to 90° C. for 20 to 120 min to obtain a precipitate;

[0033] (3-4) The above precipitate was centrifuged and washed with ethanol to obtain TiO 2 @SiO 2 , TiO 2 Loaded on silica spheres (where @ means TiO 2 Loaded on SiO 2 superior);

[0034] (3-5) The above TiO 2 @SiO 2 , calcined at 650-1200°C for 4-12h; the preferred calcination temperature is 800-1000°C.

[0035] (4) Preparation of hollow TiO 2 ball

[0036] (4-1) TiO 2 @SiO 2 Dispersed in deionized water to obtain dispersion F;

[0037] (4-2) Add 5 ml of 2.5 mol / L NaOH solution to the dispersion F, stir and mix thoroughly to obtain a precipitate;

[0038] (4-3) The precipitate is centrifuged, washed, dried, and dispersed again in deionized water to obtain a dispersion G;

[0039] (4-4) Add the hydrochloric acid solution to the dispersion G and stir to obtain TiO 2 Hollow ball.

[0040] (5) Preparation of RuO 2 / TiO 2

[0041] Ruthenium chloride solution is loaded on TiO 2 On the hollow sphere, the equal volume impregnation method was used. Weigh 10g TiO 2 Hollow spheres, a ruthenium chloride solution is prepared according to the ruthenium loading amount, the immersion time is 4 to 12 hours, the immersion temperature is 20 to 40°C, the drying temperature is 50 to 200°C, and the calcination temperature is 100 to 600°C to obtain the catalyst, wherein the active component ruthenium oxide is loaded on the titanium dioxide with a hollow sphere structure, and the particle size of the titanium dioxide with a hollow sphere structure is 10 to 200 mm.

[0042] In step (5), the drying temperature is preferably 60-120° C., and the calcination temperature is preferably 150-400° C. The isovolumetric impregnation method is a conventional technique in the art and will not be described in detail herein. It should be noted that, in the isovolumetric impregnation process of the present invention, ruthenium chloride solution is used for impregnation, the impregnation time is 4-12 hours, and the impregnation temperature is 20-40° C.

[0043] The following table shows the different catalysts prepared under different conditions of silica precursor, titanium dioxide precursor, Ru loading, calcination temperature, etc., as shown in Table 1 below:

[0044] Table 1 Different catalysts obtained under different reaction conditions

[0045]

[0046] The catalyst prepared as above is used to carry out catalytic oxidation to prepare chlorine.

[0047] Example 1-21, using the catalyst prepared in the previous example to catalytically oxidize hydrogen chloride to produce chlorine

[0048] Reaction temperature 200~800℃, reaction space velocity 40000h -1 , HCl and O 2 The volume ratio is 1: (0.5-6), the diluent is nitrogen, the catalyst is loaded in a fixed bed reactor, the reactor has an outer diameter of 20 mm, an inner diameter of 10 mm Hastelloy tube, and the catalyst loading is 1 g. After 6 hours of reaction, the sample is analyzed, and the product is analyzed by iodine titration and acid-base neutralization titration. The product analysis results of each embodiment are shown in Table 3 below:

[0049] Table 3 Analysis results of products in various examples

[0050]

[0051] From Table 3 above, it can be seen that when the reaction temperature is 350°C, the catalyst effect is the best when the reaction temperature is 350°C.2 The best effect is achieved when the volume ratio is 1:2. Comparing Examples 1 to 12, the catalyst has the best effect when TEOS and tetrabutyl titanate are used as titanium dioxide precursors.

[0052] Comparative Example 1

[0053] The operation of this comparative example is the same as that of Example 1, except that the catalyst carrier is changed to ordinary solid TiO 2 , RuO 2 Loaded on solid TiO 2 The catalyst formed on the surface of the catalyst. Analysis of the product shows that the raw material conversion rate is only 28%.

Claims

1. A catalyst for catalytic oxidation of hydrogen chloride to prepare chlorine, the catalyst having titanium dioxide as a carrier and a ruthenium species as an active component; It is characterized in that The titanium dioxide carrier is a hollow sphere structure, and the active component ruthenium is loaded on the hollow sphere structure.

2. The catalyst for preparing chlorine by catalytic oxidation of hydrogen chloride according to claim 1, Features: In the catalyst, the active component is ruthenium oxide, and the ruthenium element accounts for 0.1-5.0wt% of the total mass of the catalyst.

3. The catalyst for catalytic oxidation of hydrogen chloride according to claim 1, Features: The ruthenium element accounts for 0.5-3.0wt% of the total mass of the catalyst.

4. The catalyst for preparing chlorine by catalytic oxidation of hydrogen chloride according to claim 1, Features: The titanium dioxide is rutile titanium dioxide.

5. The catalyst for preparing chlorine by catalytic oxidation of hydrogen chloride according to claim 1, Features: The particle size of the hollow sphere structured titanium dioxide is 10 to 200 mm.

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