A process for the preparation of a hydrogen chloride oxidation catalyst

Abstract

The application provides a preparation method of a hydrogen chloride oxidation catalyst, which is a method for preparing a high-activity hydrogen chloride oxidation catalyst by using tin-silicon co-doped titanium dioxide as raw material. The catalyst is a supported catalyst with a composite material of tin-silicon co-doped titanium dioxide and aluminum trioxide as carrier and an oxide of ruthenium as active component. Through laboratory detection, the activity of the catalyst is superior to that of a catalyst synthesized by commercial titanium dioxide, and the conversion rate of the hydrogen chloride oxidation reaction reaches 91% at 300 DEG C. The catalyst has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of chlorine resource recycling, specifically to a method for preparing a chlorination-hydrogenation catalyst, which is the preparation of a supported ruthenium catalyst using a composite material of tin-silicon co-doped nano-titanium dioxide and aluminum oxide as a carrier and its application in the field of chlorine recycling. Background Technology

[0002] Chlorine (Cl2) is a basic chemical raw material with wide applications in chemical, pesticide, and pharmaceutical fields. Reaction involving chlorine accounts for 50% of chemical production processes, and most of these reactions produce an equal amount of hydrogen chloride (HCl) as a byproduct, resulting in an atom utilization rate of less than 50% for chlorine. Using hydrogen chloride as a raw material to produce chlorine allows for the recycling of hydrogen chloride, avoids supply and demand imbalances between chlorine and caustic alkalis, solves the problem of difficult subsequent treatment of hydrogen chloride, and aligns with the requirements of green, sustainable, and circular economic development in today's society.

[0003] Catalytic oxidation of hydrogen chloride refers to the method of oxidizing HCl to Cl2 in the presence of a catalyst using air or oxygen as an oxidant. This reaction is an exothermic and reversible process and has been industrialized in many industries, including isocyanate synthesis. To date, the main catalysts for the catalytic oxidation of hydrogen chloride are ruthenium-based, copper-based, and chromium-based. Ruthenium-based catalysts have the characteristics of high activity and long lifespan. In recent years, they have attracted the attention of many researchers. CN112536032A discloses a high-temperature sintering resistant catalyst for oxidizing hydrogen chloride to produce chlorine and its preparation method. The high-temperature sintering resistant catalyst is composed of a tin-doped titanium dioxide support and highly dispersed ruthenium dioxide nanoparticle active components. Its preparation method includes the following steps: (1) impregnating powdered titanium dioxide with an aqueous solution of tin tetrachloride in equal volume, and then drying and calcining to obtain a tin-doped titanium dioxide support; (2) impregnating the tin-doped titanium dioxide support obtained in step (1) with an aqueous solution of ruthenium trichloride in equal volume, and then drying and calcining to obtain the catalyst. The catalyst prepared by this invention is suitable for the reaction of chlorination and hydrogenation to produce chlorine. Doping tin into the titanium dioxide support can enhance the interaction between the active component of ruthenium dioxide nanoparticles and the support, and improve the catalyst's resistance to high-temperature sintering. However, the tin oxide in the prepared catalyst is distributed on the surface of titanium dioxide, resulting in poor uniformity of tin oxide distribution, uneven distribution of active components, and poor catalytic activity.

[0004] This invention provides a mild method for preparing tin-silicon co-doped titanium dioxide nanoparticles. The nanoparticles are composited with alumina to form a catalyst support, which is then loaded with a ruthenium trichloride solution and calcined to obtain the catalyst. This catalyst support features a large specific surface area of ​​nano-titanium dioxide, and the catalyst exhibits uniform distribution of active components and high catalytic activity, showing promising application prospects. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a highly active hydrogen chloride-hydrogenation catalyst. A catalyst is prepared by supporting ruthenium oxide on a composite material of tin-silicon co-doped titanium dioxide nanoparticles and aluminum oxide. This catalyst exhibits good activity in the hydrogen chloride-hydrogenation reaction.

[0006] The method for preparing the highly active hydrogen chloride-hydrogenation catalyst of the present invention includes the following steps:

[0007] (1) Dissolve the organotitanium compound, organosilicon compound, and organotin compound together in anhydrous ethanol, stir evenly, add dilute hydrochloric acid solution, transfer to a high-pressure reactor, react at 140-180℃ for 6-12h, and then cool naturally to room temperature. Wash the powder with deionized water until the washing solution is neutral, and test with silver nitrate to find no white precipitate. Dry and grind the product to obtain tin-silicon co-doped titanium dioxide. The dilute hydrochloric acid solution is prepared by mixing concentrated hydrochloric acid and pure water at a volume ratio of 1:0.6-1:1.5. The mass ratio of organotitanium compound to organosilicon compound is 140:1~145:1; the mass ratio of organosilicon compound to organotin compound is 1:2~1:3. The organotitanium compound is tetrabutyltitanium oxide, tetrapropyl titanate, tetraethyl titanate, or tetraisopropyl titanate. The organotin compound is tetraethyltin, dimethyltin, dibutyltin, tributyltin, triethyltin, or tetramethyltin. The organosilicon compounds are tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, or methyltriethoxysilane.

[0008] (2) Tin-silicon co-doped titanium dioxide and aluminum oxide powder are mixed evenly and placed in a kneader. Pure water is added and kneaded for 2-4 hours to form a viscous material. Then, the mixture is extruded into nano-strips with a diameter of 1.0-2.0 mm using an extruder. After drying and breaking the strips into 3.6-5.2 mm long strips, they are calcined at 600-800℃ for 4-12 hours and then naturally cooled to room temperature to obtain the catalyst support. The mass ratio of tin-silicon co-doped titanium dioxide to aluminum oxide powder is 1:2 to 1:3. The amount of pure water added is 20-30% of the total mass of tin-silicon co-doped titanium dioxide and aluminum oxide powder. The aluminum oxide powder is amorphous, γ-Al2O3, β-Al2O3, or α-Al2O3, preferably α-Al2O3.

[0009] (3) Dissolve RuCl3 completely in pure water or acid to form an impregnation solution. Add the catalyst support to the impregnation solution, allow it to adsorb for 10-30 minutes, then remove and filter. Dry the saturated catalyst support at 40-60℃. After drying, slowly raise the temperature to 300-400℃ and hold for 4-8 hours to obtain the chlorination-hydrogenation catalyst. The mass ratio of RuCl3 to pure water or acid is 1:6 to 1:8. The mass ratio of RuCl3 to the catalyst support is 1:25 to 1:30. The acid is at least one of dilute hydrochloric acid, citric acid, oxalic acid, succinic acid, formic acid, acetic acid, propionic acid, butyric acid, and octanoic acid.

[0010] In summary, this invention presents a supported catalyst using a titanium dioxide and aluminum oxide composite material as a carrier and ruthenium oxide as the active component. The catalyst is prepared by hydrothermal reaction of a mixture of organotitanium, organotin, and organosilicon compounds in the presence of hydrochloric acid to generate tin-silicon co-doped nano-titanium dioxide particles. The tin-silicon co-doped titanium dioxide and aluminum oxide composite material provides a large specific surface area, and the supported catalyst is prepared using ruthenium oxide as the active component. This catalyst exhibits uniform distribution of active components, high catalytic activity, and good aging resistance. Laboratory testing showed that this catalyst achieves a 91% conversion rate in the hydrogen chloride-hydrogenation reaction at 300℃, demonstrating promising prospects for industrial application. Detailed Implementation

[0011] Example 1

[0012] (1) Weigh 265 g of tetrabutyltitanium oxide, 1.86 g of tetraethoxysilane, and 4.95 g of tetraethyltin and dissolve them in 1000 g of analytical grade ethanol. After stirring evenly, add dilute hydrochloric acid solution (prepared by mixing 200 ml of concentrated hydrochloric acid with 200 ml of pure water). Transfer the solution to a 2 L high-pressure reactor and react at 160 °C for 3 h. Then, allow it to cool naturally to room temperature. Wash the powder with 5 L of deionized water until the washing solution is neutral. Test the washing solution with silver nitrate to ensure no white precipitate is found. Dry and grind the product for later use.

[0013] (2) Mix 30g of the above-mentioned tin-silicon co-doped titanium dioxide with 70g of commercial aluminum oxide evenly and pour the mixture into a kneader. Add 22g of pure water and knead for 2 hours to form a viscous material. Then, use an extruder to extrude the material into nano-strips with a diameter of 1.5mm. After drying, break the nano-strips into 3.0-4.0mm strips, heat the strips to 800℃ at 8℃ / min and calcine for 6 hours. Then, allow the strips to cool naturally to room temperature to obtain the catalyst support.

[0014] (3) 3.7g of commercially available RuCl with a ruthenium content of 37% was completely dissolved in 28g of pure water to form an impregnation solution. 100g of catalyst support was added to the impregnation solution. After adsorption for 15min, the catalyst support was removed and filtered. The saturated catalyst support was dried at 50℃. After drying, the temperature was increased to 300℃ at 3℃ / min and kept at 3℃ / min for 4h to obtain the hydrogen chloride-hydrogenation catalyst.

[0015] Example 2

[0016] (1) Weigh 132 g of tetrabutyloxytitanium, 0.93 g of tetraethoxysilane, and 2.49 g of tetraethyltin and dissolve them in 500 g of analytical grade ethanol. After stirring evenly, add dilute hydrochloric acid solution (prepared by mixing 100 ml of concentrated hydrochloric acid with 100 ml of pure water). Transfer the solution to a 1 L high-pressure reactor and react at 180 °C for 3 h. Then, allow it to cool naturally to room temperature. Wash the powder with 5 L of deionized water until the washing solution is neutral. Test the washing solution with silver nitrate solution to ensure that no white precipitate is found. Dry and grind the product for later use.

[0017] (2) After mixing 30g of the above-mentioned tin-silicon co-doped titanium dioxide with 70g of commercial aluminum oxide evenly, the mixture was placed in a kneader, and 25g of pure water was added and kneaded for 2 hours to form a viscous material. Then, it was extruded into nano-strips with a diameter of 1.5mm using an extruder. After drying, the nano-strips were broken into strips with a length of 3.0-4.0mm, heated to 600℃ at 8℃ / min and calcined for 6 hours, and then naturally cooled to room temperature to obtain the catalyst support.

[0018] (3) 3.51 g of commercially available RuCl with a ruthenium content of 37% was completely dissolved in 25 g of pure water to form an impregnation solution. 100 g of catalyst support was added to the impregnation solution. After adsorption for 15 min, the catalyst support was removed and filtered. The saturated catalyst support was then dried at 50 °C. After drying, the temperature was increased to 300 °C at 3 °C / min and held for 4 h to obtain the hydrogen chloride-hydrogenation catalyst.

[0019] Compare with Example 1

[0020] Weigh 265 g of tetrabutyltitanium oxide and dissolve it in 1000 g of analytical grade ethanol. After stirring evenly, add dilute hydrochloric acid solution (prepared by mixing 200 ml of concentrated hydrochloric acid with 200 ml of pure water). Transfer the solution to a 2 L high-pressure reactor and react at 160 °C for 3 h, then allow it to cool naturally to room temperature. Wash the powder with 5 L of deionized water until the washing solution is neutral. Test with silver nitrate to ensure no white precipitate is found in the washing solution. Dry and grind the product for later use.

[0021] The remaining steps are the same as in Example 1.

[0022] Compare with Example 2

[0023] Weigh 265 g of tetrabutyltitanium oxide and 4.95 g of tetraethyltin and dissolve them together in 1000 g of analytical grade ethanol. After stirring evenly, add dilute hydrochloric acid solution (prepared by mixing 200 ml of concentrated hydrochloric acid with 200 ml of pure water). Transfer the solution to a 2 L high-pressure reactor and react at 160 °C for 3 h, then allow it to cool naturally to room temperature. Wash the powder with 5 L of deionized water until the washing solution is neutral. Test with silver nitrate to ensure no white precipitate is found in the washing solution. Dry and grind the product for later use.

[0024] The remaining steps are the same as in Example 1.

[0025] Compare with Example 3

[0026] Weigh 265 g of tetrabutyloxytitanium and 1.86 g of tetraethoxysilane and dissolve them together in 1000 g of analytical grade ethanol. After stirring evenly, add dilute hydrochloric acid solution (prepared by mixing 200 ml of concentrated hydrochloric acid with 200 ml of pure water). Transfer the solution to a 2 L high-pressure reactor and react at 160 °C for 3 h, then allow it to cool naturally to room temperature. Wash the powder with 5 L of deionized water until the washing solution is neutral. Test with silver nitrate to ensure no white precipitate is found in the washing solution. Dry and grind the product for later use.

[0027] The remaining steps are the same as in Example 1.

[0028] Compare with Example 4

[0029] (1) Weigh 30g of commercially available rutile titanium dioxide and 70g of commercially available alumina, mix them evenly, place them in a kneader, add 25g of pure water and knead for 2h to form a viscous material, and then use an extruder to extrude it into nano strips with a diameter of 1.5mm. After drying, break them into small strips of 3.0-4.0mm, heat them to 600℃ at 8℃ / min and calcine for 6h, and then cool them naturally to room temperature to obtain the catalyst support.

[0030] (2) 3.51 g of commercially available RuCl with a ruthenium content of 37% was completely dissolved in 25 g of pure water to form an impregnation solution. 100 g of catalyst support was added to the impregnation solution. After adsorption for 15 min, the catalyst support was removed and filtered. The saturated catalyst support was then dried at 50 °C. After drying, the temperature was increased to 300 °C at 3 °C / min and held for 4 h to obtain the hydrogen chloride-hydrogenation catalyst.

[0031] Catalytic activity testing: Catalyst evaluation was conducted using a custom-designed fixed-bed reactor with a 15mm inner diameter and 500mm length titanium alloy tube. The reaction was carried out at atmospheric pressure, with 20g of catalyst loaded. After heating the reaction tube to 300°C, hydrogen chloride and oxygen, with flow rates precisely controlled by a mass flow meter, were introduced into the fixed-bed reactor. The hydrogen chloride flow rate was controlled at 240ml / min, and the oxygen flow rate at 120ml / min. After the reaction stabilized for 1 hour, samples were taken for analysis. Iodometric titration and acid-base titration were used to titrate the chlorine gas and unreacted hydrogen chloride in the samples, respectively.

[0032] The specific operating steps are as follows: After the reaction tube temperature reaches 300℃, absorb the gas produced after the reaction using a 30% KI solution for 5 minutes. Titrate the absorbed liquid with a 0.5 mol / L sodium thiosulfate standard solution to calculate the chlorine gas produced in the reaction. Titrate the unreacted HCl with a 0.5 mol / L sodium hydroxide standard solution. Calculate the hydrogen chloride conversion rate based on the above titration results.

[0033] The activity of the catalysts synthesized in the above examples and control examples was tested, and the results are shown in the table below.

[0034]

[0035] The above activity results show that the catalyst synthesized using tin-silicon co-doped titanium dioxide exhibits the best activity, significantly outperforming the samples synthesized using commercial titanium dioxide as a raw material. The performance of catalysts synthesized using undoped titanium dioxide and tin- or silicon-doped titanium dioxide alone falls somewhere in between.

[0036] The tin-silicon co-doped titanium dioxide and the catalyst synthesized from it reported in this invention exhibit high catalytic activity and promising application prospects. The above descriptions are merely embodiments of this invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a hydrogen chloride-hydrogenation catalyst, comprising the following steps: (1) Dissolve the organotitanium compound, organosilicon compound and organotin compound together in anhydrous ethanol, stir evenly and add dilute hydrochloric acid solution, transfer it to a high-pressure reactor, react at 140-180℃ for 6-12h and then cool naturally to room temperature, wash the powder with deionized water until the washing solution is neutral, use silver nitrate to test that there is no white precipitate in the washing solution, dry and grind the product to obtain tin-silicon co-doped titanium dioxide; The organotitanium compounds are tetrabutyloxytitanium, tetrapropyl titanate, tetraethyl titanate, or tetraisopropyl titanate; the organotin compounds are tetraethyltin, dimethyltin, dibutyltin, tributyltin, triethyltin, or tetramethyltin; the organosilicon compounds are tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, or methyltriethoxysilane. The mass ratio of organotitanium compounds to organosilicon compounds is 140:1 to 145:1; the mass ratio of organosilicon compounds to organotin compounds is 1:2 to 1:

3. (2) After the tin-silicon co-doped titanium dioxide and aluminum oxide powder are mixed evenly, they are placed in a kneader, pure water is added and kneaded for 2-4 hours to form a viscous material. Then, the material is extruded into nano strips with a diameter of 1.0-2.0 mm using an extruder. After drying and breaking into strips with a length of 3.6-5.2 mm, the material is heated to 600-800℃ and calcined for 4-12 hours, and then naturally cooled to room temperature to obtain a catalyst support. The mass ratio of tin-silicon co-doped titanium dioxide to aluminum oxide powder is 1:2 to 1:

3. (3) Dissolve RuCl3 completely in pure water or acid to form an impregnation solution. Add the catalyst support to the impregnation solution. After adsorption for 10-30 min, remove and filter. Dry the saturated catalyst support at 40-60℃. After drying, slowly raise the temperature to 300-400℃ and keep it at that temperature for 4-8 h to obtain the chlorination-hydrogenation catalyst. The mass ratio of RuCl3 to the catalyst support is 1:25~1:

30.

2. The process for preparing a hydrogen chloride oxidation catalyst according to claim 1, characterized by: In step (1), the dilute hydrochloric acid solution is prepared by mixing concentrated hydrochloric acid and pure water in a volume ratio of 1:0.6-1:1.

5.

3. The process for preparing a hydrogen chloride oxidation catalyst according to claim 1, characterized by: In step (2), the aluminum oxide powder is amorphous, γ-Al2O3, β-Al2O3 or α-Al2O3.

4. The process for preparing a hydrogen chloride oxidation catalyst according to claim 1, characterized by: In step (2), the amount of pure water added is 20-30% of the total mass of tin-silicon co-doped titanium dioxide and aluminum oxide powder.

5. The process for preparing a hydrogen chloride oxidation catalyst according to claim 1, characterized by: In step (3), the mass ratio of RuCl3 to pure water or acid is 1:6 to 1:

8.

6. The process for preparing a hydrogen chloride oxidation catalyst according to claim 1, characterized by: In step (3), the acid is at least one of dilute hydrochloric acid, citric acid, oxalic acid, succinic acid, formic acid, acetic acid, propionic acid, butyric acid, and octanoic acid.

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