Preparation method of high-stability ruthenium-based catalyst and application thereof

Abstract

This invention discloses a method for preparing a highly stable ruthenium-based catalyst. The disclosed method involves synthesizing a Ti-M-Si solid solution oxide via co-precipitation, followed by fluorination etching of the solid solution oxide to load a ruthenium component, ultimately yielding a highly stable ruthenium-based catalyst. This invention significantly improves the stability of the ruthenium-based catalyst by fluorinating and etching the Ti-M-Si solid solution oxide to synthesize a porous Ti-M solid solution support for loading the ruthenium component. This confines the Ru active phase within the pore structure of the support, inhibiting its migration and sintering under heat treatment or high-temperature reaction atmospheres.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalyst preparation, and particularly relates to a preparation method of a high-stability ruthenium-based catalyst. BACKGROUND

[0002] More than 420 million tons of hydrogen chloride are produced as a byproduct worldwide each year. Hydrogen chloride can be used in the industry to produce polyvinyl chloride (PVC), neutralize lye, and the like. However, due to factors such as the slowing growth of PVC demand, the hydrogen chloride market is limited, and the production is actually far in excess of demand. The resulting problems of hydrogen chloride treatment difficulty, environmental pollution, and the like are still very serious.

[0003] The catalytic oxidation method has low energy consumption, few side reactions, and is simple and easy to operate using a fixed bed reaction device, and can effectively promote the low-carbon and green recycling of hydrogen chloride. A catalyst with high activity, high stability, and long service life is a core element and a key development direction for the application of the catalytic oxidation process. Existing hydrogen chloride oxidation catalysts are mainly ruthenium-based catalysts, but there are still problems of insufficient stability and service life.

[0004] In patent US2014335012A1, TiO2 modified by introducing SiO2 is used as a carrier to load ruthenium oxide as a catalyst, which has limited effect on the improvement of the stability of hydrogen chloride catalytic oxidation. At a hydrogen chloride conversion rate of about 6%, the activity decays by 10-20% in only 50 h. SUMMARY

[0005] In view of the technical problem of insufficient stability of existing ruthenium-based catalysts for hydrogen chloride catalytic conversion, the present application provides a preparation method of a high-stability ruthenium-based catalyst.

[0006] Therefore, the preparation method of the high-stability ruthenium-based catalyst provided by the present application comprises the following steps:

[0007] (1) a mixed aqueous solution of a titanium source precursor, a second component metal salt, and a silicon source precursor is added to an alkali solution, and after mixing, a solid substance is collected, and then the solid substance is dried and subjected to first calcination to obtain a Ti-M-Si solid solution oxide; the second component metal salt is one of SnCl4, SnCl4 hydrate, ZrOCl2, ZrOCl2 hydrate, SmCl3, and SmCl3 hydrate; the alkali solution is one or two or more aqueous solutions of NH3, NaOH, KOH, and CsOH;

[0008] (2) the Ti-M-Si solid solution oxide is subjected to fluorination treatment to obtain a Ti-M solid solution oxide;

[0009] (3) the Ru element is loaded on the Ti-M solid solution oxide by a vacuum impregnation method, and after second calcination, the high-stability ruthenium-based catalyst is obtained.

[0010] Optionally, in step (1), the titanium source precursor is added drop by drop into water under stirring at -5-5°C, and then the second component metal salt and the silicon source precursor are added to obtain a mixed aqueous solution of the titanium source precursor, the second component metal salt and the silicon source precursor.

[0011] Optionally, the first-time calcination is performed at 300-500°C for 2-8h.

[0012] Optionally, the titanium source precursor is selected from one of TiCl3, TiCl4, tetrabutyl titanate, tetraethyl titanate and tetraisopropyl titanate.

[0013] Optionally, the silicon source precursor is one of tetraethyl orthosilicate, tetramethyl orthosilicate and silicic acid.

[0014] Optionally, in step (1), the mass ratio of the titanium source precursor, the second component metal salt, the silicon source precursor and water in the mixed aqueous solution of the titanium source precursor, the second component metal salt and the silicon source precursor is 100:(0-50):(20-200):(200-2700).

[0015] Optionally, the concentration of the alkali solution is 5-15 mol / L; and the mass ratio of the titanium source precursor, the second component metal salt, the silicon source precursor, water and the alkali solution is 100:(0-50):(20-200):(200-2700):(500-6000).

[0016] Optionally, in step (2), the fluorination treatment is liquid-phase fluorination treatment, gas-phase fluorination treatment or a combination of the two.

[0017] Optionally, the liquid-phase fluorination treatment is soaking the Ti-M-Si solid solution oxide in a 10%-30% mass concentration HF aqueous solution for 0.5-3h, wherein the mass ratio of the HF aqueous solution to the Ti-M-Si solid solution oxide is 100:1-20.

[0018] Optionally, the gas-phase fluorination treatment is treating the Ti-M-Si solid solution oxide with a mixed gas of HF gas and nitrogen gas at 100-300°C for 0.5-8h.

[0019] Optionally, in step (3), the vacuum impregnation method for loading Ru element on the Ti-M solid solution oxide comprises: first, vacuumizing the Ti-M solid solution oxide under vacuum condition, then adding a ruthenium salt precursor solution, stirring under vacuum condition for 2-16h, vacuum evaporating the solvent at 40-60°C, and drying at 80-100°C for 2-10h.

[0020] Alternatively, the second calcination temperature is 200-400℃, and the calcination time is 2-8h.

[0021] The Ti-M-Si solid solution oxide is synthesized by a co-precipitation method, and then a ruthenium component is loaded after fluorination etching of the solid solution oxide, so that a high-stability ruthenium-based catalyst is finally obtained.

[0022] The present application is based on constructing a TiO2-based carrier with limited domain functionality, and a porous Ti-M solid solution carrier is synthesized by fluorination etching of the Ti-M-Si solid solution oxide. After loading of a ruthenium component, the Ru active phase is limited in the pore structure of the carrier, and migration sintering of the Ru active phase under heat treatment or a high-temperature reaction atmosphere is inhibited, so that the stability of the ruthenium-based catalyst is significantly improved. The catalyst of the present application is particularly suitable for use as a catalyst for preparing chlorine gas by catalytic oxidation of hydrogen chloride. DETAILED DESCRIPTION

[0023] Unless otherwise defined, all terms used in connection with the present application are understood according to the common knowledge of a person skilled in the relevant art.

[0024] It should also be understood that the temperatures, time periods, etc. mentioned herein are approximate and are intended for illustrative purposes only. Although methods and materials similar or equivalent to those described herein can be used in the practice of the present disclosure, certain suitable methods and materials are described below. In addition, the materials, methods, material ratios, order of addition of components when mixing materials, and example embodiments are merely illustrative and are not intended to be limiting. In particular embodiments, one skilled in the art can optimize the material ratios, operating parameters, etc. involved in the methods according to the disclosure disclosed herein by using routine experiments to achieve the purposes of the present application.

[0025] It should be noted that the Ru element supply (or ruthenium source precursor) in the present application can be ruthenium trichloride, hydrated ruthenium trichloride, ruthenium acetylacetone, etc.

[0026] In the following examples, the elemental content of the catalyst is determined by inductively coupled plasma atomic emission spectrometry.

[0027] Example 1:

[0028] (1) 5.16 g titanium tetrachloride was dropped into 38.0 ml deionized water under ice water bath at about 0°C and with vigorous stirring, then 1.93 g SnCl4·5H2O and 2.68 g tetraethyl orthosilicate were added, and the mixture was stirred and ultrasonically mixed to obtain a uniform solution; the solution was quickly added into 158 ml NH2 aqueous solution (10 mol / L) within 1.5 s, and after stirring for 2 h, the solid part was filtered to obtain a solid, which was washed, dried, and calcined at 400±10°C for 5 h to obtain a Ti-Sn-Si solid solution oxide;

[0029] Then, 2.0 g of the solid solution oxide was placed in a stainless steel fixed bed reactor, and 200 sccm of 20% HF / N2 mixed gas was introduced at 150±10°C for 0.6 h, then the reactor was taken out after temperature reduction and purging under 200 sccm of pure N2 atmosphere to obtain a Ti-Sn solid solution oxide;

[0030] After that, 1.5 g of the Ti-Sn solid solution oxide was vacuum treated at 0.1 MPa for 2 h, then 5.2 g of RuCl3 ethanol solution (Ru mass content 0.58%) was added, and the mixture was stirred at 0.1 MPa for 12 h, then the solvent was evaporated under vacuum at 50±5°C, and the mixture was dried at 90±5°C for 5 h and then calcined at 280±10°C for 5 h to obtain a ruthenium-based catalyst A, and the mass content of Ru in the catalyst was 1.97%.

[0031] Example 2:

[0032] 6.09 g of tetraethyl orthotitanate was dropped into 43.0 ml deionized water under ice water bath at about 0°C and with vigorous stirring, then 1.52 g SmCl3·6H2O and 3.18 g tetraethyl orthosilicate were added, and the mixture was stirred and ultrasonically mixed to obtain a uniform solution; the solution was quickly added into 122 ml NaOH aqueous solution (12 mol / L) within 1.5 s, and after stirring for 2 h, the solid part was filtered to obtain a solid, which was washed, dried, and calcined at 400±10°C for 5 h to obtain a solid solution oxide;

[0033] Then, 2.0 g of the solid solution oxide was soaked in 100 ml 20% mass concentration HF aqueous solution for 0.5 h, and the mixture was stirred every 10 min, then the mixture was filtered, washed, and dried to obtain a porous solid solution oxide;

[0034] Then, 1.5 g of the porous solid solution oxide was vacuumized at 0.1 MPa for 2 h, 5.2 g of RuCl3 ethanol solution (Ru mass content 0.58%) was added, and stirred at 0.1 MPa for 12 h. The solvent was vacuum evaporated at 50±5°C, and the mixture was dried at 90±5°C for 5 h and then calcined at 280±10°C for 5 h to obtain a ruthenium-based catalyst B, and the mass content of Ru in the catalyst was 1.95%.

[0035] Comparative Example 1

[0036] 0.12 g of RuCl3·3H2O was dissolved in 30 ml of ethanol, and then 1.62 g of TiO2 and 0.61 g of SnO2 were added. The mixture was stirred and impregnated for 16 h, and then the solvent was evaporated at 50±5°C under vacuum. The mixture was dried at 80±5°C for 5 h and then calcined at 280±10°C for 4 h to obtain a ruthenium-based catalyst C, and the mass content of Ru in the catalyst was 2.03%.

[0037] Comparative Example 2

[0038] 0.12 g of RuCl3·3H2O was dissolved in 30 ml of ethanol, and then 1.54 g of TiO2 and 0.77 g of Sm2O3 were added. The mixture was stirred and impregnated for 16 h, and then the solvent was evaporated at 50±5°C under vacuum. The mixture was dried at 80±5°C for 3 h and then calcined at 280±10°C for 4 h to obtain a ruthenium-based catalyst D, and the mass content of Ru in the catalyst was 1.96%.

[0039] Catalyst Evaluation

[0040] A fixed bed reactor with a size of 350 mm×Φ10 mm×1 mm was used, and the reaction was carried out at normal pressure. The catalyst was loaded at 1.20 g, and the particle size of the catalyst was 0.1-0.18 mm. Hydrogen chloride gas and oxygen were used as the reaction gas, which was first passed through a mass flow meter and then a preheater before entering the fixed bed reactor. The reactor was heated by electricity, and the reaction temperature was 350±10°C. The flow rate of hydrogen chloride was 80 ml / min, and the flow rate of oxygen was 160 ml / min, i.e. the space velocity was 12000 L / (kg cat ·h).

[0041] After the reaction is stable for 1 h, sample analysis is performed, and iodometric method and acid-base titration method are used to titrate the chlorine and unreacted hydrogen chloride in the sample, respectively. The specific operation steps are as follows: after the system is stable, every certain time, 100 mL of 20% KI solution is prepared, the three-way valve at the outlet of the oxidation reactor is switched, the mixed gas after the reaction is introduced into the constant volume (100 mL) potassium iodide solution, and the absorption is performed for 2 minutes, after the absorption, the absorption liquid is moved into a conical flask, and 0.1 mol / L sodium thiosulfate standard solution is used for titration, and starch is used as an indicator; then, phenolphthalein is used as an indicator, and 0.1 mol / L sodium hydroxide standard solution is used for titration of unreacted HCl.

[0042] The catalysts obtained in Examples 1 and 2 and Comparative Examples 1 and 2 are evaluated in a fixed bed reactor under the above high space velocity reaction conditions, and the hydrogen chloride catalytic oxidation performance is as shown in Table 1. The catalyst stability in Table 1 is represented as the percentage of the Cl2 space-time yield at 100 h to the Cl2 space-time yield at 1 h, which is the initial activity.

[0043] Table 1

[0044]

[0045] As can be seen from Table 1, under the condition that the Ru content in the catalysts is the same or substantially the same, the catalytic stability of the hydrogen chloride oxidation catalysts A and B obtained by the preparation method of the present application is significantly higher than that of the catalysts C and D prepared by the conventional method. The method plays a significant gain role in improving the stability of the ruthenium-based catalyst. Under a high space velocity of 12000 L / (kg cat ·h), the catalysts of the present application are used for continuous reaction for 100 h, and the catalytic activity is basically not attenuated.

Claims

1. A process for the preparation of a highly stable ruthenium-based catalyst for the catalytic oxidation of hydrogen chloride to produce chlorine, characterized in that, The method comprises: (1) adding a mixed aqueous solution of a titanium source precursor, a second component metal salt and a silicon source precursor into an alkali solution, collecting solid substances after mixing, and then drying and first calcining the solid substances to obtain a Ti-M-Si solid solution oxide; the second component metal salt is one of SnCl4, SnCl4 hydrate, ZrOCl2, ZrOCl2 hydrate, SmCl3 and SmCl3 hydrate; the alkali solution is one or more than two of NH3, NaOH, KOH and CsOH aqueous solutions; (2) fluorination treatment is performed on the Ti-M-Si solid solution oxide to obtain a Ti-M solid solution oxide; (3) Ru element is loaded on the Ti-M solid solution oxide by a vacuum impregnation method, and the high-stability ruthenium-based catalyst is obtained after second calcination; The fluorination treatment in step (2) is liquid-phase fluorination treatment, gas-phase fluorination treatment or a combination of the two; The liquid-phase fluorination treatment is soaking the Ti-M-Si solid solution oxide in a 10%-30% mass concentration HF aqueous solution for 0.5-3 h, wherein the mass ratio of the HF aqueous solution to the Ti-M-Si solid solution oxide is 100:1-20; The gas-phase fluorination treatment is treating the Ti-M-Si solid solution oxide with a mixed gas of HF gas and nitrogen gas at 100-300 ℃ for 0.5-8 h.

2. The method for preparing the highly stable ruthenium-based catalyst as described in claim 1, characterized in that, In step (1), the titanium source precursor is added dropwise into water under stirring at-5-5 ℃, and then the second component metal salt and the silicon source precursor are added after mixing to obtain a mixed aqueous solution of the titanium source precursor, the second component metal salt and the silicon source precursor.

3. The method for preparing the highly stable ruthenium-based catalyst as described in claim 1, characterized in that, The first calcination temperature is 300-500 ℃, and the calcination time is 2-8 h.

4. The method for preparing the highly stable ruthenium-based catalyst as described in claim 1, characterized in that, The titanium source precursor is selected from one of TiCl3, TiCl4, tetrabutyl titanate, tetraethyl titanate and tetraisopropyl titanate.

5. The method for preparing the highly stable ruthenium-based catalyst as described in claim 1, characterized in that, The silicon source precursor is one of tetraethyl orthosilicate, tetramethyl orthosilicate and silicic acid.

6. The method for preparing the highly stable ruthenium-based catalyst as described in claim 1, characterized in that, In step (1), the mass ratio of the titanium source precursor, the second component metal salt, the silicon source precursor and water in the mixed aqueous solution of the titanium source precursor, the second component metal salt and the silicon source precursor is 100:(0-50):(20-200):(200-2700); the mass ratio of the titanium source precursor, the second component metal salt, the silicon source precursor, water and the alkali solution is 100:(0-50):(20-200):(200-2700):(500-6000); and neither of the end point values 0 is included.

7. The method for preparing the highly stable ruthenium-based catalyst as described in claim 6, characterized in that, The concentration of the alkali solution is 5-15 mol / L.

8. The method for preparing the highly stable ruthenium-based catalyst as described in claim 1, characterized in that, In step (3), the loading of Ru element on the Ti-M solid solution oxide by the vacuum impregnation method comprises: first vacuumizing the Ti-M solid solution oxide under vacuum conditions, then adding a ruthenium salt precursor solution, stirring for 2-16 h under vacuum conditions, vacuum evaporating the solvent at 40-60 ℃, and drying at 80-100 ℃ for 2-10 h.

9. The method for preparing the highly stable ruthenium-based catalyst as described in claim 1, characterized in that, The second calcination temperature is 200-400 ℃, and the calcination time is 2-8 h.

10. A process for the production of chlorine gas by catalytic oxidation of hydrogen chloride, characterized in that, The process employs a catalyst prepared according to the process of any one of claims 1 to 9. The process employs a catalyst prepared according to the process of any one of claims 1 to 9.

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