Process for the preparation of oxychloride iron

Abstract

The application provides a preparation method of oxychloride iron, and belongs to the technical field of preparation of oxychloride iron. The method uses anhydrous ferric chloride as the only iron-containing raw material, oxygen or a mixed gas of oxygen and chlorine as the reaction gas, controls the molar ratio of the effective oxygen equivalent in the reaction system to the anhydrous ferric chloride to be not more than 1.5:1, and performs a synthesis reaction at 400-700 DEG C. After the reaction is completed, the reaction gas is kept being introduced until the system is cooled, and the solid product is collected to obtain the oxychloride iron. The application also provides a tubular reaction furnace device for implementing the method, which is provided with a reaction zone and a low-temperature zone along the airflow direction, and the reaction gas is regulated by a mass flow controller. The application converts oxygen, which is a necessary interference factor, into a precisely metered reactant by precisely controlling the oxidation depth, and obtains single-phase oxychloride iron without ferric oxide impurities in one step.

Description

Technical Field

[0001] This invention belongs to the field of ferric chloride preparation technology, and specifically relates to a method for preparing ferric chloride. Background Technology

[0002] Ferric oxychloride (FeOCl) is an inorganic compound with a typical layered crystal structure and an interlayer spacing of approximately 0.8 nm. This unique layered structure endows it with excellent electrochemical performance, intercalation modification capability, and catalytic activity. In the electrochemical field, FeOCl, when used as a cathode material for primary lithium batteries, can achieve a discharge capacity more than three times that of MnO2. After intercalation modification with organic monomers such as aniline and pyrrole, it can also be used as a cathode material for secondary lithium batteries. Furthermore, FeOCl shows broad application prospects in photocatalytic degradation of organic pollutants and gas adsorption and separation. With the development of the new energy and catalytic materials industries, the market has an urgent need for the large-scale supply of high-purity FeOCl.

[0003] Currently, the main methods for preparing ferric chloride oxychloride include chemical vapor transport (CVT) technology and traditional hydrolysis. CVT uses Fe₂O₃ and anhydrous FeCl₃ as mixed raw materials, mixed in a molar ratio of 4:3 and sealed in a quartz tube. The mixture is calcined at 380°C for one week under an argon protective atmosphere, followed by filtration with a large amount of anhydrous acetone to wash away excess FeCl₃ and vacuum drying to obtain the product. This method has a reaction cycle of up to 7 days, requires strict control of raw material purity and proportions, and involves cumbersome washing and drying steps that consume large amounts of organic solvents. Traditional hydrolysis uses FeCl₃·6H₂O as raw material, reacting at 200–220°C for 3–4 hours under a nitrogen protective atmosphere to produce ferric chloride oxychloride. Although this shortens the reaction time, it still requires a large amount of nitrogen as a protective gas, the purity of the product depends on the stability of the atmosphere, and it also requires subsequent purification.

[0004] It is worth noting that the aforementioned existing preparation methods share a common technical choice: without exception, they all isolate oxygen through inert gas sealing or protection. This stems from the prevailing understanding in the field that oxygen is a strong oxidizing agent, and the final stable oxide of iron is ferric oxide. In an oxygen atmosphere, ferric chloride will be oxidized all the way to ferric oxide, unable to remain stably in the intermediate state of ferric chloride-oxygenate. Therefore, oxygen is considered a disruptive factor that must be avoided in the preparation of ferric chloride-oxygenate. This understanding results in existing methods having lengthy process chains, high energy consumption and costs, and difficulty in scaling up. Therefore, how to overcome these limitations and develop a simple, efficient, low-cost method for preparing ferric chloride-oxygenate that can yield a single-phase high-purity product is a pressing technical problem to be solved in this field. Summary of the Invention

[0005] To address the technical problem of how to quantitatively control the oxidation depth of the ferric chloride synthesis reaction in an oxygen atmosphere in the aforementioned commonly used techniques, so that the oxidation reaction selectively terminates at the ferric chloride-oxygen stage without further generating iron oxide, thereby obtaining a single-phase ferric chloride-oxygen phase without iron oxide impurities in one step, this invention provides a method for preparing ferric chloride-oxygen, comprising the following steps: S1. Using anhydrous ferric chloride as the sole iron-containing raw material, a reaction gas is introduced into the reaction system. The reaction gas is oxygen or a mixture of oxygen and chlorine. The molar ratio of effective oxygen equivalent to anhydrous ferric chloride in the reaction system is controlled to be no greater than 1.5:1. The reaction system is heated to 400~700℃ to carry out the synthesis reaction. S2. After the synthesis reaction is completed, the reaction gas is kept in the state of being introduced until the system is cooled, and the solid product is collected to obtain ferric chloride.

[0006] Furthermore, when the reactant gas is oxygen, the oxygen flow rate is 280~855 mL / min.

[0007] Furthermore, when the reaction gas is a mixture of oxygen and chlorine, the oxygen flow rate is 280~855 mL / min, the chlorine flow rate is 150~600 mL / min, and the flow rate of the mixture does not exceed 1455 mL / min.

[0008] Furthermore, the molar ratio of the effective oxygen equivalent to anhydrous ferric chloride is 0.5:1 to 1.5:1.

[0009] Furthermore, the reaction temperature is 400~550℃.

[0010] Furthermore, the anhydrous ferric chloride has a purity of ≥97%, and the anhydrous ferric chloride is laid in a thickness of 2~5mm to participate in the reaction.

[0011] Furthermore, before heating, the air in the reaction system is replaced with the reaction gas.

[0012] Furthermore, the heating rate is 5~10℃ / min, and the synthesis reaction time is 2~10h.

[0013] Furthermore, the chlorine content of the obtained ferric chloride product is 36.5%~37.2%.

[0014] The present invention also provides an apparatus for preparing ferric chloride oxychloride, for implementing the preparation method of ferric chloride oxychloride as described above, including a tubular reactor; the tubular reactor includes a reaction vessel and a heating device for heating the reaction vessel, and the reaction vessel is provided with a reaction zone and a low temperature zone in sequence along the direction of reaction gas flow; The reaction zone is 30-50 cm long and is used to lay the anhydrous ferric chloride and to carry out the synthesis reaction; the temperature of the low-temperature zone is 50-100°C lower than that of the reaction zone and is used to enrich the ferric chloride-oxygen product during the cooling process. The reaction vessel has a gas inlet at one end near the reaction zone and a gas outlet at the other end near the low-temperature zone. The gas inlet is connected to a mass flow controller to regulate the flow rate of the reaction gas. The heating device is configured to be turned off after the synthesis reaction is completed, and after the heating device is turned off, the reaction gas is continuously introduced until the reaction system cools naturally to 25±5℃, and the ferric chloride product is collected after being enriched in the low temperature zone.

[0015] Compared with the prior art, the present invention has at least the following advantages: This invention uses anhydrous ferric chloride as the sole iron-containing raw material and oxygen or a mixture of oxygen and chlorine as reactants. Through the coordinated control of the composition of the reaction gas, the molar ratio of the effective oxygen equivalent to anhydrous ferric chloride in the reaction system, and the reaction temperature (400~700℃), combined with the operation of continuously introducing reaction gas after the reaction is completed until the system cools down, a one-step preparation of single-phase ferric chloride is achieved. Its technical advantages are specifically reflected in the following aspects: Firstly, the upper limit control of the oxygen molar ratio allows for precise control of the oxidation depth. The gas-solid reaction between anhydrous ferric chloride and oxygen proceeds stepwise, initially forming ferric chloride oxychloride. When oxygen is in excess, the ferric chloride oxychloride is further oxidized to ferric oxide. By limiting the molar ratio of effective oxygen equivalent to anhydrous ferric chloride to less than or equal to 1.5:1, the partial pressure of oxygen in the system is precisely limited to the extent that ferric chloride can only be oxidized to ferric chloride oxychloride. The oxidation reaction terminates at the ferric chloride oxychloride stage, inhibiting the formation of the ferric oxide impurity phase from the source. When chlorine is incorporated to form a mixed reaction gas, chlorine, as a reaction product, reverses the oxidation equilibrium, further strengthening the inhibition of over-oxidation, thus forming a synergistic effect with the molar ratio control.

[0016] Secondly, the temperature window of 400~700℃ balances the reaction driving force and phase stability. Below 400℃, the reaction kinetics are insufficient, and ferric chloride is difficult to convert; above 700℃, side reactions and local sintering are triggered, producing impurity phases. This temperature range and the control of the oxygen molar ratio are mutually dependent and indispensable to ensure the purity of the product phase.

[0017] Third, after the reaction is complete, the reaction gas is kept flowing in until the system cools down, so that the hot products are always under the protection of the reaction gas, avoiding the oxidation or deliquescence of the products caused by backflow of air during the cooling process, and there is no need to introduce additional inert protective gases such as argon or nitrogen.

[0018] Due to the synergistic effect of the above characteristics, the obtained solid product contains no iron oxide impurities and is a single-phase ferric chloride without any subsequent purification treatment. Compared with existing chemical vapor transport technology, this invention obtains the target product in one step with a single inexpensive raw material, shortening the reaction cycle from 7 days to several hours. It eliminates post-processing steps such as organic solvent washing and vacuum drying, as well as the consumption of protective gases. The process is simple, energy consumption and cost are low, and the product batch stability is good, making it suitable for large-scale industrial production. At the same time, this invention converts oxygen, which is generally considered to be necessary to isolate in the art, into a precisely metered reactant for utilization, overcoming the inherent technical biases in the prior art. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 The image shown is the XRD pattern of the product in Comparative Example 1 of this invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0024] This invention provides a method for preparing ferric chloride, comprising the following steps: S1. Using anhydrous ferric chloride as the sole iron-containing raw material, a reaction gas is introduced into the reaction system. The reaction gas is oxygen or a mixture of oxygen and chlorine. The molar ratio of effective oxygen equivalent to anhydrous ferric chloride in the reaction system is controlled to be no greater than 1.5:1. The reaction system is heated to 400~700℃ to carry out the synthesis reaction.

[0025] This invention controls the molar ratio of effective oxygen equivalent to anhydrous ferric chloride in the reaction system to be no greater than 1.5:1. From the reaction mechanism, anhydrous ferric chloride undergoes a gas-solid reaction with oxygen to generate ferric chloride oxychloride (2FeCl3 + O2 → 2FeOCl + 2Cl2). Theoretically, only 0.5 mol of effective oxygen equivalent (O2:FeCl3 = 0.5:1) is needed to completely convert all FeCl3. However, when oxygen is supplied in excess, the generated ferric chloride oxychloride will be further oxidized to ferric oxide (4FeOCl + O2 → 2Fe2O3 + 2Cl2), resulting in the introduction of ferric oxide impurities into the product. Through experiments, the inventors discovered that a molar ratio of effective oxygen equivalent to anhydrous ferric chloride of 1.5:1 is the critical value for the phase transition of the product. When this molar ratio is less than or equal to 1.5:1, the partial pressure of oxygen in the system is precisely limited to the extent that ferric chloride can only be oxidized to ferric chloride-oxygenate, and the oxidation reaction terminates at the ferric chloride-oxygenate stage, with the product being a single ferric chloride-oxygenate phase. However, when this molar ratio exceeds 1.5:1, excess oxygen drives over-oxidation, and an iron oxide impurity phase appears in the product, which is irreversible under the reaction atmosphere. Experiments show (see Examples 1 and 6 and Comparative Examples 1 and 2) that the product phase undergoes a regular transition with 1.5:1 as the boundary, confirming that this critical value is not arbitrarily chosen, but rather a phase inflection point determined by the stoichiometry of the reaction.

[0026] It should be noted that the molar ratio of effective oxygen equivalent to anhydrous ferric chloride in this invention refers to the ratio of the limiting oxygen equivalent that can participate in the gas-solid oxidation reaction in the reaction atmosphere during the isothermal synthesis stage to the total amount of anhydrous ferric chloride fed. It does not include excess carrier gas oxygen that only passes through the material layer as purge gas and does not participate in the oxidation reaction. In the continuous gas supply system of the tubular furnace, most of the introduced oxygen is only used for gas displacement and product purging and does not participate in the oxidation reaction; the steady-state oxygen partial pressure of the system is determined by the gas ratio and temperature, corresponding to a single effective oxygen equivalent. When the reaction gas is a mixture of oxygen and chlorine, only oxygen is included in the effective oxygen equivalent, and chlorine is not included in this ratio; the oxygen in the residual air discharged during the displacement stage is not included in the effective oxygen equivalent.

[0027] This invention controls the synthesis reaction temperature to 400-700℃. Below 400℃, the gas-solid reaction kinetics are insufficient, making it difficult to convert ferric chloride. Above 700℃, localized melting and sintering occur on the surface of the ferric chloride particles, forming a dense product layer that hinders gas diffusion, triggers side reactions, and results in the appearance of impurities and a decrease in product purity. Single-phase ferric chloride can be obtained within the 400-700℃ range; the preferred range is 400-550℃, where the gaseous product formation rate is moderate, the material is less prone to sintering, and the product purity and yield are superior to other temperature ranges.

[0028] In some embodiments, when the reactant gas is oxygen, the oxygen flow rate is 280~855 mL / min.

[0029] In other embodiments, when the reactant gas is a mixture of oxygen and chlorine, the oxygen flow rate is 280~855 mL / min and the chlorine flow rate is 150~600 mL / min.

[0030] In some embodiments, the molar ratio of oxygen to anhydrous ferric chloride is 0.5:1 to 1.5:1.

[0031] In some embodiments, the reaction temperature is 400~550°C.

[0032] In some embodiments, the purity of the anhydrous ferric chloride is ≥97%, and the anhydrous ferric chloride is laid in a thickness of 2~5 mm to participate in the reaction.

[0033] In some embodiments, the air in the reaction system is replaced with the reaction gas before heating.

[0034] Replacing the air in the reaction system before heating is a prerequisite for ensuring the effectiveness of oxygen molar ratio control. The oxygen in the residual air is an uncontrollable oxygen source, which diffuses and accumulates on the surface of the material layer during the heating process, causing the actual oxygen molar ratio on the surface of the material layer to far exceed 1.5:1, resulting in local over-oxidation and the formation of iron oxide, which cannot be reversed under the subsequent reaction atmosphere.

[0035] In some embodiments, the heating rate is 5~10℃ / min, and the synthesis reaction time is 2~10h.

[0036] It should be noted that this invention does not limit the specific form of the reaction device; any reactor capable of constructing a closed reaction system and realizing the introduction of reaction gas and parameter control is acceptable, including but not limited to tubular reactors, fixed-bed reactors, and fluidized-bed reactors; tubular reactors are preferred, as they naturally form a temperature gradient along the gas flow direction, and the products are enriched in a low-temperature zone 50-100°C lower than the reaction zone and then directly collected. For large-scale production, the scale can be increased proportionally according to the gas flow rate per unit mass of raw material.

[0037] S2. After the synthesis reaction is completed, the reaction gas is kept in the state of being introduced until the system is cooled, and the solid product is collected to obtain ferric chloride.

[0038] After the synthesis reaction is completed, the reaction gas is kept flowing in until the system cools to room temperature. This ensures that the high-temperature product is always under the protection of the reaction gas, preventing the air backflow caused by the decrease in gas pressure in the furnace during the cooling process, and avoiding the secondary oxidation or moisture absorption and deterioration of the hot product. At the same time, the continuous airflow carries the gaseous product to the low-temperature zone for directional migration, which is beneficial for the enrichment and collection of the product in the low-temperature zone.

[0039] In some embodiments, the chlorine content of the resulting ferric chloride product is 36.5% to 37.2%.

[0040] It should be noted that this invention uses both XRD characterization and chlorine content analysis to determine the product, and there is a clear correspondence between the two. The theoretical chlorine content of ferric chloride oxychloride (FeOCl) is 33.04% (calculated based on the molecular formula FeOCl). The XRD pattern is the direct basis for phase determination: when only the characteristic diffraction peaks of ferric chloride oxychloride appear in the diffraction pattern and no characteristic diffraction peaks of iron oxide are detected, the product is determined to be a single ferric chloride oxychloride phase; the chlorine content is a quantitative evidence of phase purity: iron oxide does not contain chlorine, and the more iron oxide mixed in the product, the lower the measured chlorine content. The chlorine content of the single-phase ferric chloride products obtained in Examples 1-7 of this invention is 36.5%~37.2% (slightly higher than the theoretical value due to trace adsorption of chlorine gas and co-deposition of a small amount of oligomeric ferric chloride). In Comparative Example 2, the chlorine content monotonically decreases from 35.22% to 28.09% as the amount of iron oxide impurities increases. In Comparative Example 3 (800℃), the chlorine content drops to 34.01% when impurities appear. The chlorine content and phase purity show a strict monotonic correlation. Therefore, chlorine content can be used as an auxiliary indicator for quickly determining the phase purity of the product: a chlorine content in the range of 36.5%~37.2% corresponds to single-phase ferric chloride, and deviations from this range indicate the formation of impurities.

[0041] It should also be noted that the above-mentioned technical solution of this application represents a breakthrough from the technical biases in this field. For a long time, there has been a common understanding in this field that iron will be oxidized to its final state of ferric oxide in an oxygen atmosphere, and that ferric chloride oxychloride, as an intermediate state, cannot be stably obtained in an oxygen atmosphere. Therefore, existing methods for preparing ferric chloride oxychloride invariably employ argon gas sealing or nitrogen protection to isolate oxygen; simultaneously, using an excess of oxidant in reactions involving oxidation to ensure complete conversion is also a conventional technical approach in this field. Furthermore, the inventors' previous research has also shown that ferric chloride oxychloride decomposes in an oxygen atmosphere at 400-600°C and is difficult to maintain stably.

[0042] Based on the above understanding, those skilled in the art have neither the motivation nor the courage to prepare ferric chloride oxychloride in an oxygen atmosphere at 400-600°C. Through extensive experimentation, the inventors unexpectedly discovered that the oxidation of ferric chloride by oxygen is a stepwise process, and the depth of oxidation is quantitatively determined by the amount of oxygen supplied: when the molar ratio of effective oxygen equivalent to anhydrous ferric chloride is less than 1.5:1, the oxidation reaction precisely terminates at the ferric chloride oxychloride stage. Combined with a temperature window of 400-700°C, ferric chloride oxychloride can not only be generated in an oxygen atmosphere but also exist stably as a single solid phase. Therefore, this application breaks the technical prejudice that the preparation of ferric chloride oxychloride must avoid oxygen, transforming oxygen from a necessary and isolated interfering factor into a precisely quantified reactant, achieving the unexpected technical effect of one-step synthesis of single-phase ferric chloride oxychloride.

[0043] The present invention also provides an apparatus for preparing ferric chloride oxychloride, for implementing the preparation method of ferric chloride oxychloride as described above, including a tubular reactor; the tubular reactor includes a reaction vessel and a heating device for heating the reaction vessel, and the reaction vessel is provided with a reaction zone and a low temperature zone in sequence along the direction of reaction gas flow; The reaction zone is 30-50 cm long and is used to lay the anhydrous ferric chloride and to carry out the synthesis reaction; the low-temperature zone is located outside the heating area of ​​the heating device and its temperature is 50-100°C lower than that of the reaction zone, and is used to enrich the ferric chloride product during the cooling process. The reaction vessel has a gas inlet at one end near the reaction zone and a gas outlet at the other end near the low-temperature zone. The gas inlet is connected to a mass flow controller to regulate the flow rate of the reaction gas. The heating device is configured to be turned off after the synthesis reaction is completed, and after the heating device is turned off, the reaction gas is continuously introduced until the reaction system cools naturally to 25±5℃, and the ferric chloride product is collected after being enriched in the low temperature zone.

[0044] In some embodiments, anhydrous ferric chloride is laid with a thickness of 2-5 mm to ensure that the reaction gas penetrates the material layer and diffuses evenly, avoiding incomplete reaction of the inner raw materials due to excessive material layer thickness; the heating rate is controlled at 5-10℃ / min to ensure that the system temperature rises evenly and to prevent local overheating and premature sintering; the constant temperature for 2-10 hours can ensure complete reaction. If the time is too short, the conversion rate will be insufficient, and if it is too long, the energy consumption will increase and there will be no further improvement to the phase.

[0045] In some embodiments, after the reaction is completed, the product migrates with the gas flow to the low-temperature zone for enrichment, and is collected directly in the low-temperature zone after the furnace is opened; the collected ferric chloride product is placed in a desiccator and sealed for storage, with the relative humidity of the storage environment ≤30% to prevent moisture absorption and deterioration.

[0046] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided: Example 1 300g of anhydrous ferric chloride (98% purity) was evenly spread in the quartz reaction zone of a tubular reactor to a thickness of 5mm. After evacuating to 100Pa and replacing with oxygen, oxygen (99.9% purity) was introduced at a flow rate of 284mL / min, maintaining a steady-state effective oxygen equivalent to anhydrous ferric chloride molar ratio of 0.5:1. Excess oxygen continuously introduced into the pipeline was used only as a purging carrier gas and was not included in the effective oxygen equivalent calculation. The temperature was increased to 400℃ at a rate of 5℃ / min and maintained at this temperature for 3 hours. After the reaction, oxygen was continuously introduced, and the system was allowed to cool naturally to room temperature (25±5℃). 194.5g of solid product was collected in the low-temperature zone.

[0047] Experimental results: The product was a black, lumpy substance with a metallic luster. XRD characterization showed it to be a single ferric chloride-oxychloride phase, with no characteristic diffraction peaks of iron oxide detected. The chlorine content was 36.83%, and the yield was 93.8%. A small amount of raw material escaped with the tail gas due to high-temperature gasification, and trace amounts of product were adsorbed on the pipeline wall and not completely collected, resulting in a yield that did not reach 100%.

[0048] Example 2 Compared to Example 1, all other conditions remain the same in this example, except that the reaction temperature is adjusted to 500°C.

[0049] Experimental results: The product was a single ferric chloride-oxychloride phase with a chlorine content of 36.91% and a yield of 95.1%.

[0050] Example 3 Compared to Example 1, all other conditions remain the same in this example, except that the reaction temperature is adjusted to 700°C.

[0051] Experimental results: The product was a single ferric chloride-oxychloride phase with a chlorine content of 36.65% and a yield of 90.8%.

[0052] Example 4 Compared to Example 1, all other conditions remain the same in this example, except that the reaction temperature is adjusted to 550°C.

[0053] Experimental results: The product is a single ferric chloride-oxychloride phase with a chlorine content of 36.88% and a yield of 95.6%. Compared with Example 3, the product yield in this example is better, supporting the preferred temperature range of 400~550℃.

[0054] Example 5 Compared to Example 1, all other conditions remain unchanged in this example, except that the molar ratio of effective oxygen equivalent to anhydrous ferric chloride is adjusted to 1:1.

[0055] Experimental results: The product is a single ferric chloride phase with a chlorine content of 36.76% and a yield of 94.0%.

[0056] Example 6 Compared to Example 1, all other conditions remain unchanged in this example, except that the molar ratio of effective oxygen equivalent to anhydrous ferric chloride is adjusted to 1.5:1.

[0057] Experimental results: The product was a single ferric chloride-oxychloride phase with a chlorine content of 36.52% and a yield of 92.4%.

[0058] Example 7 Compared to Example 1, all other conditions remain unchanged in this example, except that the reaction gas is a mixture of oxygen and chlorine, the oxygen flow rate is 568 mL / min, the chlorine flow rate is 300 mL / min, the effective oxygen equivalent to anhydrous ferric chloride molar ratio is 1:1, and the reaction temperature is 500℃.

[0059] Experimental results: The product was a single ferric chloride phase with a chlorine content of 37.05% and a yield of 96.6%.

[0060] Comparative Example 1 Compared to Example 1, all other conditions in this comparative example remain unchanged, except that the molar ratio of effective oxygen equivalent to anhydrous ferric chloride in the system is adjusted to 2:1.

[0061] Experimental results: such as Figure 1 As shown, the XRD pattern of the product shows obvious characteristic diffraction peaks of iron oxide, indicating that it is a mixed phase of ferric chloride and iron oxide. The chlorine content is reduced to 35.10%, and the yield of ferric chloride is 76.2%.

[0062] This comparative example shows that when the molar ratio of effective oxygen equivalent to anhydrous ferric chloride increases to 2:1, exceeding the critical value of 1.5:1, the oxygen content in the system exceeds the stoichiometry required to oxidize ferric chloride to ferric chloride oxychloride. Excess oxygen drives the over-oxidation reaction in the forward direction, and the product transforms from a single phase to a mixed phase of ferric chloride oxychloride and ferric oxide. Comparison with the single-phase results of Example 1 (0.5:1) and Example 6 (1.5:1) shows that 1.5:1 is the critical value for the phase transformation of the product and is not an arbitrary choice of conventional parameters.

[0063] Comparative Example 2 Compared to Example 1, all other conditions in this comparative example remained unchanged, except that the molar ratio of effective oxygen equivalent to anhydrous ferric chloride was adjusted to 1.6:1, 2.5:1 and 3:1, respectively.

[0064] Experimental results: The proportion of iron oxide in the product increased with the increase of molar ratio, and the chlorine content was 35.22%, 31.46%, and 28.09%, respectively, with yields of 87.5%, 63.1%, and 49.6%, respectively.

[0065] This comparative example, through gradient experiments at ratios of 1.6:1, 2.5:1, and 3:1, shows that after exceeding the critical value, the proportion of iron oxide in the product monotonically increases with the increase of the oxygen molar ratio, while the chlorine content correspondingly decreases monotonically from 35.22% to 28.09%. The phase purity responds continuously and regularly to the oxygen molar ratio, further confirming that the phase inflection point at 1.5:1 is determined by the stoichiometry of the reaction. It also shows that there is a quantitative correlation between chlorine content and phase purity, which can be used as an auxiliary indicator for judging product purity.

[0066] Comparative Example 3 Compared to Example 1, all other conditions in this comparative example remained unchanged, except that the reaction temperature was adjusted to 800°C.

[0067] Experimental results: The XRD pattern of the product showed iron oxide impurities, and the particles were sintered and agglomerated. Red iron oxide powder and black iron chloride with metallic luster appeared in the product. The chlorine content in the product was 34.01%, and the phase purity was significantly lower than that of Example 1. The yield was 72.7%.

[0068] This comparative example raises the reaction temperature to 800℃, exceeding the 400~700℃ temperature upper limit of this invention. Under high temperature conditions, the generated ferric chloride oxychloride is prone to thermal decomposition, and at the same time, it significantly accelerates the deep oxidation side reaction of ferric chloride oxychloride to iron oxide; moreover, a large amount of ferric chloride is vaporized and lost with the tail gas. The final product contains both iron oxide impurities and ferric chloride oxychloride agglomerates, and the chlorine content drops to 34.01%, resulting in a significant decrease in the target single-phase ferric chloride oxychloride yield.

[0069] Comparative Example 4 Compared to Example 1, all other conditions in this comparative example remained unchanged, except that the reaction temperature was adjusted to 300°C.

[0070] Experimental results: Chlorine content was 32.55%, and yield was 66.1%.

[0071] In this comparative example, the reaction temperature was lowered to 300°C, which is below the 400°C lower reaction limit of this invention. Under low-temperature conditions, the gas-solid oxidation reaction kinetics of ferric chloride with oxygen are extremely low, making it difficult for the generated chlorine gas to desorb from the material surface, thus inhibiting the forward progression of the main reaction. Most of the anhydrous ferric chloride cannot be converted to ferric chloride oxychloride. The product is mainly unreacted ferric chloride, containing only a small amount of ferric chloride oxychloride.

[0072] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing ferric chloride oxychloride, characterized in that, Includes the following steps: S1. Using anhydrous ferric chloride as the sole iron-containing raw material, a reaction gas is introduced into the reaction system. The reaction gas is oxygen or a mixture of oxygen and chlorine. The molar ratio of effective oxygen equivalent to anhydrous ferric chloride in the reaction system is controlled to be no greater than 1.5:

1. The reaction system is heated to 400~700℃ to carry out the synthesis reaction. S2. After the synthesis reaction is completed, the reaction gas is kept in the state of being introduced until the system is cooled, and the solid product is collected to obtain ferric chloride.

2. The method for preparing ferric oxychloride according to claim 1, characterized in that, When the reactant gas is oxygen, the oxygen flow rate is 280~855 mL / min.

3. The method for preparing ferric chloride oxychloride according to claim 1, characterized in that, When the reactant gas is a mixture of oxygen and chlorine, the oxygen flow rate is 280~855 mL / min, the chlorine flow rate is 150~600 mL / min, and the flow rate of the mixture does not exceed 1455 mL / min.

4. The method for preparing ferric oxychloride according to claim 1, characterized in that, The molar ratio of the effective oxygen equivalent to anhydrous ferric chloride is 0.5:1 to 1.5:

1.

5. The method for preparing ferric oxychloride according to claim 1, characterized in that, The reaction temperature is 400~550℃.

6. The method for preparing ferric oxychloride according to claim 1, characterized in that, The anhydrous ferric chloride has a purity of ≥97%, and the anhydrous ferric chloride is laid in a thickness of 2~5mm to participate in the reaction.

7. The method for preparing ferric chloride oxychloride according to claim 1, characterized in that, Before heating, the air in the reaction system is replaced with the reaction gas.

8. The method for preparing ferric chloride according to claim 1, characterized in that, The heating rate is 5~10℃ / min, and the synthesis reaction time is 2~10h.

9. The method for preparing ferric chloride oxychloride according to claim 1, characterized in that, The chlorine content of the obtained ferric chloride product was 36.5%~37.2%.

10. The method for preparing ferric chloride according to claim 1, characterized in that, The preparation method is carried out in a preparation apparatus for ferric chloride oxychloride, the preparation apparatus including a tubular reactor; the tubular reactor includes a reaction vessel and a heating device for heating the reaction vessel, and the reaction vessel is provided with a reaction zone and a low temperature zone in sequence along the direction of reaction gas flow; The reaction zone is 30-50 cm long and is used to lay the anhydrous ferric chloride and to carry out the synthesis reaction; the temperature of the low-temperature zone is 50-100°C lower than that of the reaction zone and is used to enrich the ferric chloride-oxygen product during the cooling process. The reaction vessel has a gas inlet at one end near the reaction zone and a gas outlet at the other end near the low-temperature zone. The gas inlet is connected to a mass flow controller to regulate the flow rate of the reaction gas. The heating device is configured to be turned off after the synthesis reaction is completed, and after the heating device is turned off, the reaction gas is continuously introduced until the reaction system cools naturally to 25±5℃, and the ferric chloride product is collected after being enriched in the low temperature zone.

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