Method and device for preparing chlorine through catalytic oxidation of hydrogen chloride

Abstract

The invention relates to a method and a device for preparing chlorine through catalytic oxidation of hydrogen chloride. The method comprises the following steps: pretreating hydrogen chloride gas by adopting a pretreater filled with titanium dioxide, and reacting part of hydrogen chloride gas with titanium dioxide to obtain hydrogen chloride gas flow containing hydrogen chloride, water and titanium tetrachloride; the hydrogen chloride gas flow and oxygen are subjected to a catalytic oxidation reaction in a reactor containing a catalyst, and chlorine is obtained; in the hydrogen chloride gas flow at the outlet of the preprocessor, the mass content of titanium tetrachloride is 1-10ppm; the catalyst comprises a titanium dioxide carrier. According to the method, the service life of the catalyst can be effectively prolonged, loss and inactivation of the catalyst are inhibited, and meanwhile, high yield of chlorine and low cost of the process are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and device for preparing chlorine gas by catalytic oxidation of hydrogen chloride. BACKGROUND

[0002] Chlorine is an important raw material for chlorinated chemicals, and is widely used in chemical industry, electronic industry, pharmaceutical industry, textile, petroleum chemical industry, environmental protection and other industries. In the industrial process of producing various chlorine products, the utilization rate of chlorine is less than half, and by-product hydrogen chloride is produced. The by-product hydrogen chloride is highly corrosive, has high transportation cost, is regionally strong in market, is cheap in price, has small demand, and is oversupplied. The alkaline neutralization of excess by-product hydrogen chloride also causes environmental pollution. The by-product hydrogen chloride can be used to prepare chlorine gas, so as to realize its utilization.

[0003] At present, the chemical process methods for preparing chlorine gas from hydrogen chloride mainly include direct oxidation method, electrolysis method and catalytic oxidation method.

[0004] The direct oxidation method is a process method for oxidizing HCl to Cl2 using liquid inorganic oxide at normal pressure and low temperature. The reaction raw materials and products of this method are highly corrosive, which is not conducive to safe production. The reaction process is complicated, the operation difficulty is large, many by-products are difficult to separate from the raw materials, and there are a large amount of waste acid in the by-products. The process of neutralizing waste acid will increase the cost, and the emission will pollute the environment. Therefore, this process cannot realize industrialized production and application.

[0005] The electrolysis method is to pass hydrogen chloride and oxygen into an electrolytic cell, and the chlorine ion and oxygen undergo electrocatalytic oxidation reaction under the condition of power supply, and the chlorine ion recombines to generate chlorine gas. Since the electrolysis process requires large amount of electric energy, the energy consumption is large; and this method requires high purity of raw materials, which also increases the cost.

[0006] The catalytic oxidation method is a method for generating chlorine gas by oxidizing hydrogen chloride with oxygen or air as oxidant under the action of catalyst, and the stoichiometric formula can be expressed as:

[0007]

[0008] This method has the advantages of low energy consumption, low equipment cost and simple operation, and has great economic and social benefits. It is the most promising and industrialized potential method at present.

[0009] In the catalytic oxidation method, two types of catalysts are commonly used, namely, ruthenium-based catalysts and copper-based catalysts. Among them, the ruthenium-based catalysts usually use titanium dioxide as the carrier, and the catalytic mechanism of this reaction is the typical Langmuir-Hinshelwood mechanism. This catalyst has a unique surface structure and abundant active sites, thus having good reaction activity and a relatively low catalytic reaction temperature. Therefore, it is most commonly used in industrial production. The catalytic mechanism of copper-based catalysts is the Mars-van Krevelen mechanism, which involves two steps. In the first step, the chlorination process, HCl reacts with CuO to generate CuCl2, while water is generated. This chlorination process is exothermic. In the second step, the dechlorination process, CuCl2 is oxidized by oxygen molecules to form Cl2 and CuO, and the catalyst is regenerated. This dechlorination step is endothermic. However, the temperature of the second step, dechlorination reaction, needs to reach above 380°C. Since the overall hydrogen chloride catalytic oxidation is an exothermic reaction, the equilibrium conversion rate of HCl is relatively low, the chlorine gas yield is low, and the catalyst deactivation is more severe under high temperature conditions.

[0010] For noble metal catalysts such as ruthenium-based catalysts, catalyst life is particularly critical. In this catalytic oxidation reaction, the main factors affecting catalyst life are:

[0011] First, the organic matter in the raw material produces substances with relatively high boiling points under the action of the catalyst, which adhere to the surface of the catalyst, causing the catalyst's pore channels to be blocked, which easily leads to catalyst deactivation. To address this issue, the patent CN106145039A of Shanghai Chlor-Alkali Chemical Industry Co., Ltd. controls the impurity content in the raw materials hydrogen chloride and oxygen, and uses an additional catalyst A to catalyze the combustion reaction of impurities before the catalytic oxidation reaction to remove impurities. However, the impurity content in the raw material is still relatively high.

[0012] Second, the process brings in sulfur-containing substances, causing the active components of the catalyst to be deactivated. For example, the circulating gas containing H2S, CS2, SO2, and SO3 sulfur impurities after drying with concentrated sulfuric acid enters the reactor, causing the catalyst to combine with the sulfur-containing impurities, greatly reducing the catalyst's life. To address this issue, the patent CN117819481A of Wanhua Chemical Group Co., Ltd. discloses purifying the raw material with 98% concentrated sulfuric acid and controlling the content of key impurities, such as sulfur compounds, in the concentrated sulfuric acid, to reduce the combination of impurity sulfur compounds with the active components of the catalyst and improve the active sites, thereby improving the stability of the catalyst and extending the service life of the catalyst. However, this method requires additional equipment for handling concentrated sulfuric acid, which is costly and complicated to operate.

[0013] III. Reaction hot spots (local abnormal rise in temperature) exist, which leads to over-temperature of the catalyst bed, loss of active components, and finally deactivation of the catalyst. To this end, the patent CN1297471C of BASF SE increases the content of water in the inlet by increasing the circulation, which increases the overall gas velocity after backflow. After the gas flow rate increases, it increases the impact wear on the catalyst, which accelerates the deactivation of the catalyst and affects the service life of the catalyst. The patent CN100357175C of BASF SE uses a combination of fluidized bed and fixed bed, which can effectively reduce the existence of reaction hot spots, but the fluidized bed inlet is free of water. If a catalyst with titanium dioxide as the carrier is used, the carrier component will inevitably be lost, leading to catalyst deactivation. Moreover, the fluidized bed operation is complex, the catalyst deactivation caused by friction in the fluidized bed is more obvious, the catalyst loss rate is high, and the service life of the catalyst is reduced.

[0014] In the preparation of chlorine by catalytic oxidation of hydrogen chloride catalyzed by a ruthenium-based catalyst, how to prolong the service life of the catalyst, inhibit the deactivation of the catalyst, and at the same time ensure a relatively low cost is a difficulty in the synthesis of chlorine by catalytic oxidation. SUMMARY

[0015] The purpose of the present application is to provide a method for preparing chlorine by catalytic oxidation of hydrogen chloride, which can effectively prolong the service life of the catalyst, inhibit the loss and deactivation of the catalyst, and at the same time ensure a high yield of chlorine and a low cost of the process.

[0016] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0017] A method for preparing chlorine by catalytic oxidation of hydrogen chloride, the method comprising the following steps: using a pretreater loaded with titanium dioxide to pretreat hydrogen chloride gas, allowing part of the hydrogen chloride gas to react with the titanium dioxide, and obtaining a hydrogen chloride gas stream containing hydrogen chloride, water, and titanium tetrachloride; and carrying out catalytic oxidation reaction of the hydrogen chloride gas stream and oxygen in a reactor containing a catalyst to obtain chlorine; the mass content of titanium tetrachloride in the hydrogen chloride gas stream at the outlet of the pretreater is 1-10 ppm; and the catalyst comprises a titanium dioxide carrier.

[0018] In the prior art, various patents have adopted various means to prolong the service life of noble metal catalysts such as ruthenium-based catalysts for various reasons of catalyst deactivation, but the prior art has not found that the loss of the carrier of the catalyst will cause the service life of the catalyst to be shortened in the process of catalytic oxidation reaction. The inventors of the present application have found through research that the structure of the carrier of the noble metal catalyst will be damaged at high temperature, which also causes the catalyst to be deactivated and the service life of the catalyst to be shortened. When a noble metal catalyst with titanium dioxide as the carrier is used to catalyze the reaction, it is found through research that the catalyst activity is mainly deactivated more seriously at the inlet of the mixer (the preliminary reaction stage), and gradually deactivated from the inlet, eventually leading to the hydrogen chloride conversion rate not meeting the requirements and the service life of the catalyst being too short. The reason is that in the process of catalytic oxidation, the reactant concentration is high at the beginning, causing the reaction temperature at the inlet to rise, generating a reaction hot spot, causing the active components of the catalyst to be lost, leading to the deactivation of the catalyst; at the same time, the catalyst carrier titanium dioxide will react with the raw material hydrogen chloride at high temperature to generate water and titanium tetrachloride (reaction formula as follows: ), the boiling point of the product titanium tetrachloride is 136℃, which can easily vaporize, and the vaporized titanium tetrachloride will diffuse into the main body of the gas stream, flow with the reaction gas stream, causing the loss of the catalyst carrier, leading to the deactivation of the catalyst.

[0019] To this end, the present application sets a pre-treater before the reactor, uses the pre-treater and the reactor in series, and controls the concentration of titanium tetrachloride at the outlet of the pre-treater within a certain range, which can inhibit the reaction and loss of the catalyst carrier titanium dioxide in the reactor, effectively prolonging the service life of the catalyst. The pre-treater is filled with a pre-treatment agent titanium dioxide, and the added hydrogen chloride raw material first reacts with the titanium dioxide in the pre-treater to generate titanium tetrachloride and water, so that the titanium dioxide pre-treatment agent is reacted to generate titanium tetrachloride and water, and when the reaction raw materials such as hydrogen chloride and oxygen enter the reactor, the reaction in the reactor can be effectively inhibited, thereby controlling the reaction of the catalyst carrier titanium dioxide in the reactor, and effectively preventing the catalyst carrier titanium dioxide from being reacted into titanium tetrachloride and damaging the structure of the catalyst carrier, effectively preventing the catalyst from being deactivated and increasing the service life of the catalyst.

[0020] The reaction between the aforementioned titanium dioxide support and the raw material hydrogen chloride is an equilibrium reaction. When the concentration of the product titanium tetrachloride is high, the equilibrium shifts towards the reverse reaction, suppressing the loss of catalyst support in the reactor and extending the catalyst's lifespan. However, titanium tetrachloride gas flows downstream with the reaction gas stream. When its concentration is too high, it can regenerate solid titanium dioxide in subsequent equipment as the reaction proceeds, easily causing blockage of the reaction apparatus's pipelines. While directly adding titanium tetrachloride can suppress this reaction, large amounts can cause the produced titanium dioxide to clog the pipelines. Furthermore, adding ppm-level titanium tetrachloride is difficult to measure and control, and titanium tetrachloride is chemically unstable, forming fumes in air at room temperature and decomposing in humid air. It also has a certain degree of toxicity, making transportation inconvenient. This invention, by controlling the appropriate concentration of titanium tetrachloride at the pre-processor outlet, can significantly extend catalyst lifespan, significantly suppress catalyst deactivation, extend the stable operation time of the device, and significantly improve the hydrogen chloride conversion rate.

[0021] In some embodiments, the mass content of titanium tetrachloride in the hydrogen chloride gas stream at the preprocessor outlet is 1-5 ppm.

[0022] In some embodiments, the catalyst is selected from ruthenium-based, copper-based, or zirconium-based catalysts.

[0023] Preferably, the catalyst is a ruthenium-based catalyst. For example, a ruthenium-based catalyst may be ruthenium oxide.

[0024] In some implementations, the preprocessor is one or more.

[0025] In some implementations, there are two preprocessors.

[0026] Preferably, the two preprocessors are connected in parallel. When the titanium dioxide in one preprocessor is consumed to a certain extent, the system can switch to the other preprocessor and replenish the consumed preprocessor with new titanium dioxide to avoid affecting the normal operation of the device.

[0027] In some embodiments, the preprocessor includes an inlet, an outlet, a housing with an internal cavity, and a rotating basket located within the cavity; the rotating basket is rotatable and has a hollowed-out design; the titanium dioxide is filled in the rotating basket.

[0028] In some embodiments, the preprocessor further includes a feed conduit for introducing the hydrogen chloride gas from the feed inlet into the rotating basket. The feed conduit facilitates the contact and reaction between hydrogen chloride and titanium dioxide.

[0029] In some embodiments, the preprocessor further includes a drive device for rotating the basket and an impeller connected to the drive device and located inside the basket. During the preprocessing process, hydrogen chloride feedstock is introduced into the preprocessor through the feed inlet and feed conduit. The gaseous reactants pass rapidly and uniformly through the titanium dioxide bed in the basket under the drive of the impeller, while the basket also rotates rapidly, ensuring complete mixing of the gas and solid phases in the prereactor and a uniform distribution of the gas phase composition.

[0030] In some implementations, the preprocessor may also be equipped with a sealing system to prevent gas leakage.

[0031] In some embodiments, both the inlet and outlet are located at the upper end of the housing.

[0032] In some embodiments, both the housing and the rotating basket are made of nickel. Nickel is resistant to hydrogen chloride corrosion.

[0033] In some embodiments, the rotating basket is composed of a wire mesh with pores smaller than the particle size of the titanium dioxide in the preprocessor. This prevents the solid carrier from detaching while allowing gas to pass through smoothly.

[0034] In some embodiments, the reaction temperature in the preprocessor is 300-450°C; preferably 350-400°C. The temperature in the preprocessor of the present invention is higher than the temperature of the reactor.

[0035] In some embodiments, the mass hourly space velocity (HHSV) of the titanium dioxide in the preprocessor is 0.1-10 h⁻¹. -1 Preferably 4-6h -1 .

[0036] In some embodiments, the reactor is a fixed-bed reactor, preferably a tubular reactor.

[0037] In some embodiments, the inlet of the fixed-bed reactor is equipped with a gas distributor.

[0038] In some implementations, the fixed-bed reactor is equipped with multiple temperature detectors.

[0039] In some implementations, the fixed-bed reactor uses molten salt temperature control, with individual temperature control for different fixed beds.

[0040] In some implementations, the height of the fixed bed is 0.5-2m.

[0041] In some embodiments, there are 1 to 6 reactors; preferably 2 to 4; more preferably arranged in series.

[0042] In some implementations, the molar ratio of hydrogen chloride fed into the preprocessor to oxygen fed into the reactor is 1:1 to 4:1.

[0043] In some embodiments, the mass hourly space velocity (MSV) of the reactor is 1-10 h⁻¹. -1 .

[0044] In some embodiments, the temperature of the catalytic oxidation reaction is 240-380°C.

[0045] In some embodiments, the pressure of the catalytic oxidation reaction is 0.1-0.6 MPa.

[0046] In some embodiments, the method further includes steps of compressing, filtering, and preheating the hydrogen chloride gas before performing the pretreatment on the hydrogen chloride gas.

[0047] Furthermore, the compression uses a conventional compressor; the filtration uses a filter containing an adsorbent, preferably carbon dioxide or activated carbon fiber.

[0048] In some embodiments, the method further includes, after the catalytic oxidation reaction, the steps of hydrogen chloride absorption, hydrochloric acid filtration, chlorine drying, chlorine compression, chlorine condensation, and liquid chlorine distillation.

[0049] The present invention also provides an apparatus for the aforementioned method of catalytic oxidation of hydrogen chloride to produce chlorine, the apparatus comprising a pre-processor and a reactor arranged sequentially;

[0050] The preprocessor is filled with titanium dioxide and is used to pretreat hydrogen chloride gas.

[0051] The reactor contains a catalyst and is used for the catalytic oxidation reaction of hydrogen chloride and oxygen, the catalyst comprising a titanium dioxide support;

[0052] The preprocessor includes an inlet, an outlet, a shell with an internal cavity, and a rotating basket located inside the cavity; the rotating basket is rotatable and has a hollowed-out design; the titanium dioxide is filled in the rotating basket.

[0053] In some embodiments, the preprocessor further includes a feed conduit for introducing the hydrogen chloride gas from the feed inlet into the rotating basket.

[0054] In some embodiments, the preprocessor further includes a drive device for driving the basket to rotate and an impeller located inside the basket and connected to the drive device.

[0055] In some embodiments, both the inlet and outlet are located at the upper end of the housing.

[0056] In some embodiments, both the housing and the rotating basket are made of nickel.

[0057] In some embodiments, the rotating basket is composed of a wire mesh with a pore size smaller than the particle size of the titanium dioxide in the preprocessor.

[0058] In some embodiments, the reactor is a fixed-bed reactor, preferably a tubular reactor.

[0059] In some embodiments, the inlet of the fixed-bed reactor is equipped with a gas distributor.

[0060] In some implementations, the fixed-bed reactor is equipped with multiple temperature detectors.

[0061] In some implementations, the fixed-bed reactor uses molten salt temperature control, with individual temperature control for different fixed beds.

[0062] In some implementations, the height of the fixed bed is 0.5-2m.

[0063] In some embodiments, there are 1 to 6 reactors; preferably 2 to 4; more preferably arranged in series.

[0064] In some embodiments, the apparatus further includes a hydrogen chloride compressor, a hydrogen chloride filter, and a hydrogen chloride preheater disposed upstream of the preprocessor.

[0065] In some embodiments, the apparatus further includes a hydrogen chloride absorption tower, a hydrochloric acid filter, a chlorine drying tower, a chlorine compressor, a chlorine condenser, and a liquid chlorine distillation tower disposed after the reactor.

[0066] In some embodiments, the apparatus further includes a molten salt heat exchanger for reactor temperature control.

[0067] In some embodiments, the apparatus further includes an oxygen feed pipe located after the preprocessor and before the reactor.

[0068] In some embodiments, the apparatus further includes an oxygen compressor and an oxygen preheater.

[0069] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0070] This invention, by setting a pre-processor before the reactor, connecting the pre-processor and the reactor in series, and controlling the concentration of titanium tetrachloride at the pre-processor outlet within a certain range, can suppress the reaction and loss of titanium dioxide catalyst support in the reactor, effectively extend catalyst life, suppress catalyst deactivation, and at the same time ensure relatively stable production, long stable operation time of the device, and significantly improve hydrogen chloride conversion rate.

[0071] The catalyst of the catalytic oxidation reaction of the present invention has a lifespan of more than 30,000 hours and a catalyst loss rate of less than 0.5%, and the catalyst stability is significantly improved. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of an apparatus for the catalytic oxidation of hydrogen chloride to produce chlorine according to an embodiment of the present invention;

[0073] Figure 2 This is a schematic diagram of the preprocessor structure according to an embodiment of the present invention;

[0074] Figure 3 This is a schematic diagram of the transfer basket in the preprocessor according to an embodiment of the present invention;

[0075] Among them, 1-hydrogen chloride compressor, 2-hydrogen chloride filter, 3-hydrogen chloride preheater, 4-pre-processor, 5-oxygen compressor, 6-oxygen preheater, 7-oxygen feed pipe, 8-reactor, 9-hydrogen chloride absorption tower, 10-hydrochloric acid filter, 11-chlorine drying tower, 12-chlorine compressor, 13-chlorine condenser, 14-liquid chlorine distillation tower, 15-tower top condenser, 16-reboiler, 17-liquid chlorine storage tank, 18-heater, 19-molten salt heat exchanger, 20-feed inlet, 21-discharge outlet, 22-shell, 23-rotating basket, 24-titanium dioxide, 25-feed conduit, 26-impeller, 27-drive device, a-hydrogen chloride gas, b-oxygen. Detailed Implementation

[0076] The apparatus for the catalytic oxidation of hydrogen chloride to produce chlorine gas according to the present invention can be specifically implemented as follows:

[0077] like Figure 1As shown, the apparatus includes a hydrogen chloride and oxygen pretreatment module, a catalytic oxidation reaction module, and a product separation module. The hydrogen chloride and oxygen pretreatment module includes a hydrogen chloride compressor 1, a hydrogen chloride filter 2, and a hydrogen chloride preheater 3 for hydrogen chloride pretreatment, and an oxygen compressor 5 and an oxygen preheater 6 for oxygen pretreatment. After preheating, the oxygen enters the reactor 8 via an oxygen feed pipe 7. The catalytic oxidation reaction module includes a pre-processor 4 and the reactor 8, and may also include a molten salt heat exchanger 19 for temperature control of the reactor 8, and a heater 18 for heating the reactor 8. The product separation module includes a hydrogen chloride absorption tower 9, a hydrochloric acid filter 10, a chlorine drying tower 11, a chlorine compressor 12, a chlorine condenser 13, and a liquid chlorine distillation tower 14 after the reactor 8. The top of the liquid chlorine distillation tower 14 is connected to a top condenser 15, and the bottom is connected to a reboiler 16. The distilled liquid chlorine is temporarily stored in a liquid chlorine storage tank 17. There may be one or more pre-processors 4, preferably two pre-processors 4 arranged in parallel. Although... Figure 1 The diagram shows two preprocessors 4, but the invention is not limited to this. There are 1-6 reactors 8; preferably 2-4; more preferably arranged in series. Although Figure 1 The diagram shows two reactors 8, but the present invention is not limited to this.

[0078] like Figures 2-3 As shown, the preprocessor 4 includes an inlet 20, an outlet 21, a housing 22 with an internal cavity, and a rotating basket 23 located inside the cavity; the rotating basket 23 is rotatable and has a hollowed-out design; titanium dioxide 24 is filled in the rotating basket 23.

[0079] Furthermore, the preprocessor 4 also includes a feed conduit 25 for introducing hydrogen chloride gas a from the feed port into the rotating basket 23.

[0080] Furthermore, the preprocessor 4 also includes a drive unit 27 for driving the rotating basket 23 to rotate and an impeller 26 located inside the rotating basket 23 connected to the drive unit 27.

[0081] Furthermore, both the inlet 20 and the outlet 21 are located at the upper end of the housing 22. Both the housing 22 and the rotating basket 23 are made of nickel.

[0082] Furthermore, the rotating basket 23 is composed of a metal mesh with a pore size smaller than the particle size of the titanium dioxide 24 in the preprocessor 4.

[0083] Furthermore, reactor 8 is a fixed-bed reactor 8, preferably a tubular reactor 8. The height of the fixed bed is 0.5-2m.

[0084] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention, but the present invention is not limited to the scope of the examples described.

[0085] Example 1

[0086] This embodiment provides a method for preparing chlorine gas by the catalytic oxidation of hydrogen chloride, using the aforementioned apparatus, and the specific steps are as follows:

[0087] The initial feed hydrogen chloride gas and oxygen gas molar ratio was 2:1. The hydrogen chloride gas was first compressed, filtered, and preheated before entering one of two parallel preprocessors filled with titanium dioxide. The temperature of the preprocessor was controlled at 380℃, the reaction pressure at 0.3MPa, and the mass hourly space velocity (HHSV) of the preprocessor relative to the titanium dioxide packed in the rotating basket was 5h⁻¹. -1 The mass concentration (ppm) of titanium tetrachloride in the gas flow at the pre-processor outlet is 2.10 ppm. The specific method for detecting the ppm mass of titanium tetrachloride is as follows: Graphite furnace atomic absorption spectrophotometry is used. A 20g water sample is taken at the pre-reactor outlet. By controlling the opening of the sampling outlet valve, it is ensured that no bubbles escape during the absorption process, and the sampling process is a closed-loop process to prevent gas leakage. This ensures that all water, titanium tetrachloride, and residual hydrogen chloride generated in the pre-processor reaction are absorbed. The sample is weighed as m3, and then measured using graphite furnace atomic absorption spectrophotometry on a pyrolysis-coated graphite tube. The mass percentage concentration of titanium tetrachloride in the aqueous solution is calculated, and the result is x. Therefore, the mass of titanium tetrachloride in the sample is m3*x. Thus, the mass concentration (ppm) of titanium tetrachloride in the hydrogen chloride gas flow at the pre-processor outlet can be calculated as m3*x / (m3-20)*10. 6 The specific instrument operating conditions are as follows: detection wavelength: 365.4nm; slit width: 0.2nm; titanium hollow cathode lamp, lamp current: 20mA; argon flow rate: 0.3L / min (gas stopped during atomization stage); sample volume: 20μL; drying temperature: 85~125℃; drying time: 55s; ashing temperature: 1400℃; ashing time: 20s; atomization temperature: 2800℃; atomization time: heating up 1.5s, holding for 4s; scavenging temperature: 2850℃; scavenging time: 2s.

[0088] Oxygen is first compressed and preheated, then enters the reactor through the oxygen feed pipe. The hydrogen chloride gas stream from the pre-processor outlet also enters the reactor. An oxidation catalyst is loaded into the fixed-bed reactor; specifically, it is a ruthenium-based titanium dioxide supported catalyst (specifically, a titanium dioxide-supported ruthenium oxide catalyst, which can be commercially available or prepared using conventional processes in the art). The temperature in the fixed-bed reactor is controlled at 320°C, the reaction pressure at 0.3 MPa, and the mass hourly space velocity (WHSV) at 4 h⁻¹.-1 The oxidation reaction was carried out in a fixed-bed reactor, and the chlorine recovery rate was 86.8%. After the fixed-bed reactor was continuously operated for 1200 hours, the unit was disassembled, the catalyst was removed, and weighed as m2. The catalyst loss rate was calculated to be 0.18%. The loss rate is calculated as: Loss rate = (m1-m2) / m1*100%.

[0089] Examples 2-9

[0090] This embodiment provides a method for preparing chlorine gas by catalytic oxidation of hydrogen chloride. The specific steps are basically the same as those in Embodiment 1, except that different process parameters are adjusted. Specifically, the reaction temperature of the pre-processor, the mass hourly space velocity of the pre-processor, the mass percentage of titanium tetrachloride in the pre-processor outlet gas stream, the reaction temperature of the fixed-bed reactor, and different operating times of the device are shown in Table 1.

[0091] The reaction yields and catalyst loss rates for each embodiment are shown in Table 1 below.

[0092] Table 1. Process parameters and results of each embodiment.

[0093]

[0094]

[0095] Comparative Example 1

[0096] This comparative example provides a method for the catalytic oxidation of hydrogen chloride to produce chlorine. The specific steps are basically the same as in Example 1, except that the reaction apparatus does not have a pre-processor, and hydrogen chloride gas and oxygen are directly mixed and introduced into the fixed-bed reactor after preheating. The result was a chlorine yield of 77.5%. After continuous operation for 1200 hours, the apparatus was disassembled, the catalyst was removed, and the calculated catalyst loss rate was 1.5%.

[0097] Comparative Example 2

[0098] This comparative example provides a method for the catalytic oxidation of hydrogen chloride to produce chlorine. The specific steps are basically the same as in Example 1, except that the reaction apparatus does not have a pre-processor, and water is added at the inlet of the fixed-bed reactor. The molar amount of water added is 0.1 times the molar ratio of the hydrogen chloride feed. The result is a chlorine yield of 79.8%. After continuous operation for 1200 hours, the apparatus was disassembled, the catalyst was removed, and the catalyst loss rate was calculated to be 0.9%.

[0099] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing chlorine gas by catalytic oxidation of hydrogen chloride, characterized in that: The method includes the following steps: pretreating hydrogen chloride gas using a pre-processor filled with titanium dioxide, causing a portion of the hydrogen chloride gas to react with the titanium dioxide to obtain a hydrogen chloride gas stream containing hydrogen chloride, water, and titanium tetrachloride; catalytically oxidizing the hydrogen chloride gas stream with oxygen in a reactor containing a catalyst to obtain chlorine gas; the mass content of titanium tetrachloride in the hydrogen chloride gas stream at the outlet of the pre-processor is 1-10 ppm; the catalyst includes a titanium dioxide support.

2. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The mass content of titanium tetrachloride in the hydrogen chloride gas stream at the preprocessor outlet is 1-5 ppm.

3. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The catalyst is selected from ruthenium-based, copper-based, or zirconium-based catalysts.

4. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The preprocessor is one or more; preferably, the preprocessor is two; more preferably, the two preprocessors are connected in parallel.

5. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The preprocessor includes an inlet, an outlet, a shell with an internal cavity, and a rotating basket located inside the cavity; the rotating basket is rotatable and has a hollowed-out design; the titanium dioxide is filled in the rotating basket.

6. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 5, characterized in that: The preprocessor also includes a feed conduit for introducing the hydrogen chloride gas from the feed inlet into the rotating basket; And / or, the preprocessor further includes a drive device for driving the rotating basket to rotate and an impeller located inside the rotating basket and connected to the drive device.

7. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 5, characterized in that: The inlet and outlet are both located at the upper end of the housing; and / or, the housing and the rotating basket are both made of nickel; and / or, the rotating basket is composed of a metal wire mesh, the aperture of which is smaller than the particle size of the titanium dioxide in the preprocessor.

8. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The reaction temperature in the preprocessor is 300-450°C; and / or, the mass hourly space velocity (HHSV) of the titanium dioxide in the preprocessor is 0.1-10 h⁻¹. -1 .

9. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The reactor is a fixed-bed reactor, preferably a tubular reactor; and / or, there are 1-6 reactors; and / or, the molar ratio of hydrogen chloride in the pre-processor feed to oxygen in the reactor feed is 1:1-4:1; and / or, the mass hourly space velocity (MSV) of the reactor is 1-10 h⁻¹. -1 ; and / or, the temperature of the catalytic oxidation reaction is 240-380℃; and / or, the pressure of the catalytic oxidation reaction is 0.1-0.6MPa.

10. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The method further includes steps of compressing, filtering, and preheating the hydrogen chloride gas before performing the pretreatment.

11. The method for preparing chlorine gas by catalytic oxidation of hydrogen chloride according to claim 1, characterized in that: The method further includes, after the catalytic oxidation reaction, steps of absorbing hydrogen chloride, filtering hydrochloric acid, drying chlorine, compressing chlorine, condensing chlorine, and distilling liquid chlorine.

12. An apparatus for the method of catalytic oxidation of hydrogen chloride to produce chlorine gas according to any one of claims 1-11, characterized in that: The device includes a preprocessor and a reactor arranged sequentially. The preprocessor is filled with titanium dioxide and is used to pretreat hydrogen chloride gas. The reactor contains a catalyst and is used for the catalytic oxidation reaction of hydrogen chloride and oxygen, the catalyst comprising a titanium dioxide support; The preprocessor includes an inlet, an outlet, a shell with an internal cavity, and a rotating basket located inside the cavity; the rotating basket is rotatable and has a hollowed-out design; the titanium dioxide is filled in the rotating basket.

13. The apparatus according to claim 12, characterized in that: The preprocessor further includes a feed conduit for introducing the hydrogen chloride gas from the feed inlet into the rotating basket; and / or, the preprocessor further includes a drive device for driving the rotating basket to rotate and an impeller connected to the drive device and located inside the rotating basket; and / or, the feed inlet and the discharge outlet are both located at the upper end of the housing; and / or, the housing and the rotating basket are both made of nickel; and / or, the rotating basket is composed of a metal wire mesh, the aperture of which is smaller than the particle size of the titanium dioxide in the preprocessor.

14. The apparatus according to claim 12, characterized in that: The apparatus further includes a hydrogen chloride compressor, a hydrogen chloride filter, and a hydrogen chloride preheater disposed before the preprocessor; and / or, the apparatus further includes a hydrogen chloride absorption tower, a hydrochloric acid filter, a chlorine drying tower, a chlorine compressor, a chlorine condenser, and a liquid chlorine distillation tower disposed after the reactor; and / or, the apparatus further includes an oxygen feed pipe located after the preprocessor and before the reactor.

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