Process for recycling hexachlorocyclotriphosphazene synthesis waste residues

Abstract

The application discloses a process for recycling hexachlorocyclotriphosphazene synthesis waste residue, which comprises the following steps: reacting the waste residue separated after the end of hexachlorocyclotriphosphazene synthesis reaction with an ammonia source, wherein the ammonia source is liquid ammonia, ammonia gas, ammonia water, ammonium bicarbonate, ammonium carbonate or a combination thereof, adjusting the end point pH value to 6-10, performing solid-liquid separation on the obtained reaction product to obtain filtrate and filter cake, performing post-treatment on the filter cake to obtain recovered metal chloride catalyst, using chlorobenzene as an extractant to extract the filtrate to obtain an extraction phase and a raffinate phase, performing rectification on the extraction phase to obtain chlorobenzene and recovered pyridine or pyridine derivatives, and performing dehydration treatment on the raffinate phase to obtain recovered ammonium chloride. The process realizes high recycling of the hexachlorocyclotriphosphazene synthesis waste residue, the recovery rate of pyridine or pyridine derivatives in the waste residue can reach 95-99% or above, the recovery rate of ammonium chloride and metal chloride catalyst can reach 98% or above, and no new waste residue is generated in the whole process.

Description

Technical Field

[0001] This invention relates to a process for the resource utilization of waste residue from the synthesis of hexachlorocyclotriphosphazene, belonging to the field of chemical production technology. Background Technology

[0002] Hexachlorocyclotriphosphazene is a very important intermediate. Because the phosphorus atom contains two substituted chlorine atoms, it can generate a variety of derivatives, which can be used as flame retardants, adsorbents, and antioxidants.

[0003] Hexachlorocyclotriphosphazene is typically prepared by reacting ammonium chloride and phosphorus pentachloride in an inert solvent with metal chlorides such as aluminum chloride, ferric chloride, barium chloride, magnesium chloride, cobalt chloride, manganese chloride, copper chloride, nickel chloride, zinc chloride, and calcium chloride as catalysts, and pyridine or pyridine derivatives (C1-C3 alkoxypyridines) as acid-binding agents at a certain temperature. After the reaction is complete, pyridine or pyridine derivatives form pyridine hydrochloride that is insoluble in the inert solvent. This hydrochloride is mixed with the metal chloride and excess ammonium chloride to form a solid, which is then separated in a subsequent solid-liquid separation process and disposed of as waste residue. For every ton of hexachlorocyclotriphosphazene produced, approximately 0.6-0.8 tons of this waste residue are generated. This waste residue mainly contains pyridine hydrochloride (or pyridine derivative hydrochloride), ammonium chloride, metal chloride as a catalyst, and a small amount of solvent. The content of pyridine hydrochloride (or pyridine derivative hydrochloride) is 50-70%, the content of ammonium chloride is 10-35%, the content of metal chloride is 5-20%, and the remainder is chlorobenzene and other impurities. Currently, there are no literature or patent reports on the resource recycling of this waste residue.

[0004] Chinese patent CN201410684338.3 proposes a method for synthesizing hexachlorocyclotriphosphazene using PCl5 and NH4Cl in chlorobenzene solvent, with ferric chloride, zinc chloride, and magnesium chloride as a composite catalyst and pyridine as an acid-binding agent. The product is then filtered to remove the pyridine hydrochloride-containing waste residue, and crude hexachlorocyclotriphosphazene is obtained by vacuum distillation. This patent does not mention the method for disposing of the pyridine hydrochloride-containing waste residue.

[0005] Chinese patent CN200610116011.1 proposes a method for producing hexachlorocyclotriphosphazene by reacting PCl5 and NH4Cl in chlorobenzene solvent, using metal chlorides such as magnesium chloride, aluminum chloride, or zinc chloride as catalysts, and pyridine or C1-C3 alkoxypyridine as acid-binding agents at reflux temperature. This patent does not mention any method for disposing of the waste containing pyridine hydrochloride.

[0006] Chinese patent CN202211506957.4 proposes a method for preparing hexachlorocyclotriphosphazene by reacting a solution of phosphorus pentachloride and chlorobenzene, ammonium chloride in chlorobenzene solvent, and an ionic liquid (prepared by passing a mixture of chlorobenzene, a complex metal chloride, and pyridine through HCl) as a catalyst at elevated temperature. The waste residue is removed by filtration, and chlorobenzene is recovered by vacuum distillation to obtain a mixed solid phosphazene. This patent does not mention the disposal method for the waste residue containing pyridine hydrochloride. Summary of the Invention

[0007] In view of the technical problem that the waste residue generated from the synthesis process of hexachlorocyclotriphosphazene cannot be recycled and utilized in the existing technology, the purpose of this invention is to provide a process for resource utilization of the waste residue from the synthesis of hexachlorocyclotriphosphazene.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue includes the following steps:

[0010] 1) The waste residue separated after the synthesis reaction of hexachlorocyclotriphosphazene is reacted with an ammonia source, and the final pH value is adjusted to 6-10 to obtain the reaction product. The ammonia source is liquid ammonia, ammonia gas, ammonia water, ammonium bicarbonate, ammonium carbonate, or a combination thereof.

[0011] 2) The reaction product described in step 1) is subjected to solid-liquid separation to obtain filtrate and filter cake.

[0012] 3) Extract the filtrate from step 2) with chlorobenzene to obtain the extract phase and the raffinate phase.

[0013] 4) The extract phase obtained in step 3) is distilled to obtain chlorobenzene and recovered pyridine or pyridine derivatives.

[0014] In step 1) of the above process, the reaction temperature is further 0-50℃.

[0015] In step 1) of the above process, the waste residue is mixed with water and then reacted with the ammonia source. The mass ratio of waste residue to water is 1:0.5 to 5.

[0016] In step 1) of the above process, the pH endpoint is further adjusted to 6-9.

[0017] In step 1) of the above process, the waste residue is further added to ammonia water, or a solution prepared by water and ammonia water, liquid ammonia, ammonia gas, ammonium carbonate (or a combination thereof) for reaction.

[0018] Further, the filter cake obtained in step 2) is reacted with hydrochloric acid and then dehydrated to obtain the recovered metal chloride catalyst; the recovered metal chloride catalyst is used as a catalyst in the reaction to prepare hexachlorocyclotriphosphazene.

[0019] In the above process step 3), the extraction is either intermittent extraction or countercurrent continuous extraction, and the number of intermittent extractions is 1-5 times.

[0020] Furthermore, the amount of chlorobenzene used as the extractant in each intermittent extraction is 0.5-5 times the mass of water in the filtrate.

[0021] Furthermore, in the countercurrent continuous extraction, the ratio of the extractant mass flow rate to the filtrate mass flow rate is 0.5 to 3:1.

[0022] In step 4) of the above process, the extract phase is first dehydrated by azeotropic distillation, molecular sieve dehydration or pervaporation membrane dehydration to obtain a dehydrated extract phase. Then, the dehydrated extract phase is distilled to obtain recovered pyridine or pyridine derivatives and chlorobenzene from the top of the column. The remaining bottom liquid is reused in step 3) as an extractant.

[0023] In step 4) of the above process, the recovered pyridine or pyridine derivative is used as an acid-binding agent in the reaction to prepare hexachlorocyclotriphosphazene using chlorobenzene as solvent and PCl5 and NH4Cl as raw materials.

[0024] Furthermore, the recovered pyridine or pyridine derivatives are permitted to contain a significant amount of chlorobenzene, with a chlorobenzene content ≤90%.

[0025] Further, the raffinate phase described in step 3) is dehydrated to obtain recovered ammonium chloride.

[0026] Furthermore, the dehydration treatment of the raffinate phase includes the steps of azeotropic distillation, concentration, and drying. First, azeotropic distillation is performed to remove 10-30% of the water in the raffinate phase. The fraction distilled by azeotropic distillation is reused in step 3) for extraction treatment. Then, the concentration and drying operations are performed. After dehydration, the ammonium chloride water content is ≤1%. The water recovered from concentration and drying is reused in step 2) as filter cake washing water and / or in step 1) for mixing with waste residue.

[0027] Furthermore, the recovered ammonium chloride is used as a raw material in the reaction to prepare hexachlorocyclotriphosphazene.

[0028] The beneficial effects of this invention are:

[0029] 1) This invention achieves a high degree of resource recovery and regeneration of hexachlorocyclotriphosphazene synthesis waste residue. The recovery rate of pyridine or pyridine derivatives in the waste residue can reach over 95-99%, and the recovery rate of ammonium chloride and metal chloride catalyst can reach over 98%. The entire process generates no new waste residue. Although the catalyst recovery system generates wastewater due to water introduced by hydrochloric acid, this wastewater is easily treated and meets the standards for light pollution. This invention achieves resource recovery and regeneration of waste residue, significantly reduces the production cost of hexachlorocyclotriphosphazene, and effectively avoids secondary pollution, thus realizing clean production.

[0030] 2) The pyridine recovered from resource recycling can be directly reused in the hexachlorocyclotriphosphazene synthesis process even when there is a high content of chlorobenzene, without affecting the synthesis efficiency of hexachlorocyclotriphosphazene. This significantly reduces the difficulty of distillation in pyridine recovery and saves energy. At the same time, there is no need to pre-treat the initial waste residue to remove residual solvent chlorobenzene before recovery, and residual chlorobenzene can be recovered, saving equipment investment, material consumption, and energy consumption. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the production apparatus for the resource recovery of hexachlorocyclotriphosphazene synthesis waste residue according to this application. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0033] Example 1:

[0034] Adopting such Figure 1 The process framework shown, which utilizes the waste residue from the synthesis of hexachlorocyclotriphosphazene, includes the following steps:

[0035] 1) The waste residue separated after the synthesis reaction of hexachlorocyclotriphosphazene consists of the following components by weight fraction: pyridine hydrochloride content is 53.65%, ammonium chloride is 26.52%, metal chloride (a mixture of ferric chloride, zinc chloride and magnesium chloride) is 15.66%, and the remainder is chlorobenzene solvent and other impurities.

[0036] The above-mentioned waste residue and water were mixed at a mass ratio of 1:2 to obtain a mixture. Ammonia gas was then introduced to carry out the reaction. The reaction temperature was controlled at 35-40℃, and the final pH value was adjusted to 6-7 to obtain the reaction product.

[0037] 2) The reaction product described in step 1) is subjected to solid-liquid separation to obtain filtrate and filter cake. The filter cake is washed with water, and the washing water is combined with the filtrate.

[0038] 3) The filtrate from step 2) is extracted with chlorobenzene to obtain an extract phase and a raffinate phase; the extraction is a batch extraction, and the number of batch extractions is 4. The amount of chlorobenzene used in each batch extraction is 0.8 times the mass of water in the filtrate;

[0039] 4) First, dehydrate the extract phase obtained in step 3) by azeotropic distillation, and then use a control. Figure 1 The fraction obtained from the azeotropic distillation and dehydration is reused in step 3). The dehydrated extract phase is then distilled in a distillation column to obtain recovered pyridine containing a relatively high amount of chlorobenzene from the top of the column. The pyridine content is 53.287%, the chlorobenzene content is 46.690%, and the water content is 0.023%. The remaining bottom liquid, i.e., chlorobenzene, is reused in step 3 as an extractant.

[0040] 5) The raffinate obtained in step 3) is dehydrated. First, the aqueous solution containing pyridine is distilled off by azeotropic distillation, accounting for 23% of the total water in the raffinate. This solution is then used in the next batch of step 3) to mix with the filtrate for extraction. After concentration and drying, the recovered ammonium chloride is obtained. The ammonium chloride has a purity of 98.15%, a water content of 0.46%, and a recovery rate of 98.93%. Part of the water recovered from concentration and drying is used in step 1) to dissolve the filter residue, and part is used in step 2) as filter cake washing water.

[0041] 6) The filter cake obtained in step 2) is neutralized with hydrochloric acid and then dehydrated to obtain the recovered metal chloride catalyst. The purity of the metal chloride (a mixture of ferric chloride, zinc chloride, and magnesium chloride) is 96.11%, the water content is 0.73%, and the recovery rate is 98.49%.

[0042] When the production process described above is running stably, the recovered pyridine basically contains only two components: pyridine and chlorobenzene. The pyridine content is (50-55)% ± 1%, the chlorobenzene content is about 45-50%, and the remaining impurities are less than 0.05%. The pyridine recovery rate can reach more than 95-99%.

[0043] When the recovered pyridine is used as an acid-binding agent, metal chloride as a catalyst, and ammonium chloride as a raw material in the reaction to prepare hexachlorocyclotriphosphazene using chlorobenzene as a solvent and PCl5 as a raw material, the reaction yield of hexachlorocyclotriphosphazene can reach more than 90%, basically achieving the same or similar experimental results as when using fresh pyridine as an acid-binding agent, fresh metal chloride as a catalyst, and fresh ammonium chloride as a raw material.

[0044] Example 2:

[0045] Adopting such Figure 1 The process framework shown, which utilizes the waste residue from the synthesis of hexachlorocyclotriphosphazene, includes the following steps:

[0046] 1) The waste residue separated after the synthesis reaction of hexachlorocyclotriphosphazene consists of the following components by weight fraction: 67.42% pyridine hydrochloride, 14.33% ammonium chloride, 14.27% metal chloride (a mixture of cobalt chloride, aluminum chloride and magnesium chloride), and the remainder is chlorobenzene solvent and other impurities.

[0047] The above-mentioned waste residue was added to 15% ammonia water for reaction, the reaction temperature was controlled at 5-10℃, and the final pH value was adjusted to 8-9 to obtain the reaction product.

[0048] 2) The reaction product described in step 1) is subjected to solid-liquid separation to obtain filtrate and filter cake. The filter cake is washed with water, and the washing water is combined with the filtrate.

[0049] 3) The filtrate from step 2) is extracted with chlorobenzene to obtain an extract phase and a raffinate phase; the extraction is a batch extraction, the batch extraction is performed once, and the amount of chlorobenzene used in the batch extraction is 4 times the mass of water in the filtrate;

[0050] 4) First, the extract phase obtained in step 3) is dehydrated using 4A molecular sieve, and then the dehydrated extract phase is distilled to obtain recovered pyridine containing a large amount of chlorobenzene from the top of the column. The pyridine content is 13.115%, the chlorobenzene content is 86.850%, and the water content is 0.035%. The remaining bottom liquid of the column, i.e. chlorobenzene, is reused in step 3 as an extractant.

[0051] 5) The raffinate obtained in step 3) is dehydrated. First, the aqueous solution containing pyridine is distilled off by azeotropic distillation, accounting for 20% of the total water in the raffinate. This solution is then used in the next batch of step 3) and mixed into the filtrate for extraction. After concentration and drying, the recovered ammonium chloride is obtained. The ammonium chloride has a purity of 97.89%, a water content of 0.37%, and a recovery rate of 98.39%. Part of the water recovered from concentration and drying is used in step 2) as filter cake washing water, and the remainder is treated as wastewater.

[0052] 6) The filter cake obtained in step 2) is neutralized with hydrochloric acid and then dehydrated to obtain the recovered metal chloride catalyst. The purity of the metal chloride (a mixture of cobalt chloride, aluminum chloride, and magnesium chloride) is 96.5%, the water content is 0.42%, and the recovery rate is 98.68%.

[0053] When the production process described above is running stably, the recovered pyridine basically contains only two components: pyridine and chlorobenzene. The pyridine content is (10-15)% ± 0.5%, the chlorobenzene content is about 85-90%, and the remaining impurities are less than 0.05%. The pyridine recovery rate can reach more than 95-99%.

[0054] When the recovered pyridine is used as an acid-binding agent, metal chloride as a catalyst, and ammonium chloride as a raw material in the reaction to prepare hexachlorocyclotriphosphazene using chlorobenzene as a solvent and PCl5 as a raw material, the reaction yield of hexachlorocyclotriphosphazene can reach more than 90%, basically achieving the same or similar experimental results as when using fresh pyridine as an acid-binding agent, fresh metal chloride as a catalyst, and fresh ammonium chloride as a raw material.

[0055] Example 3:

[0056] Adopting such Figure 1 The process framework shown, which utilizes the waste residue from the synthesis of hexachlorocyclotriphosphazene, includes the following steps:

[0057] 1) The waste residue separated after the synthesis reaction of hexachlorocyclotriphosphazene consists of the following components by weight fraction: 67.42% pyridine hydrochloride, 14.33% ammonium chloride, 14.27% metal chloride (a mixture of cobalt chloride, aluminum chloride and magnesium chloride), and the remainder is chlorobenzene solvent and other impurities.

[0058] The above waste residue and water were mixed at a mass ratio of 1:5 to obtain a mixture. Ammonium carbonate was slowly added to carry out the reaction. The reaction temperature was controlled at 40-45℃ and the final pH value was adjusted to 6-7 to obtain the reaction product.

[0059] 2) The reaction product described in step 1) is subjected to solid-liquid separation to obtain filtrate and filter cake. The filter cake is washed with water, and the washing water is reused in step 1) for the next waste residue dissolution.

[0060] 3) The filtrate from step 2) is extracted with chlorobenzene to obtain an extract phase and a raffinate phase; the extraction is a batch extraction, the number of batch extractions is 5, and the amount of chlorobenzene used in the batch extraction is 0.5 times the mass of water in the filtrate;

[0061] 4) First, the extract phase obtained in step 3) is dehydrated using a pervaporation membrane device, and then the dehydrated extract phase is distilled to obtain recovered pyridine containing a large amount of chlorobenzene from the top of the column. The pyridine content is 12.334%, the chlorobenzene content is 87.639%, and the water content is 0.027%. The remaining bottom liquid of the column, i.e. chlorobenzene, is reused in step 3 as an extractant.

[0062] 5) The raffinate obtained in step 3) is dehydrated. First, the aqueous solution containing pyridine is distilled off by azeotropic distillation, accounting for 10% of the total water in the raffinate. This solution is then used in the next batch of step 3) to mix with the filtrate for extraction. After concentration and drying, the recovered ammonium chloride is obtained. The ammonium chloride has a purity of 98.11%, a water content of 0.39%, and a recovery rate of 98.59%. Part of the water recovered from concentration and drying is used in step 1) to dissolve the filter residue, and part is used in step 2) as filter cake washing water.

[0063] 6) The filter cake obtained in step 2) is neutralized with hydrochloric acid and then dehydrated to obtain the recovered metal chloride catalyst. The purity of the metal chloride (a mixture of cobalt chloride, aluminum chloride, and magnesium chloride) is 97.44%, the water content is 0.38%, and the recovery rate is 98.62%.

[0064] When the production process described above is running stably, the recovered pyridine basically contains only two components: pyridine and chlorobenzene. The pyridine content is (10-15)% ± 0.5%, the chlorobenzene content is about 85-90%, and the remaining impurities are less than 0.05%. The pyridine recovery rate can reach more than 95-99%.

[0065] When the recovered pyridine is used as an acid-binding agent, metal chloride as a catalyst, and ammonium chloride as a raw material in the reaction to prepare hexachlorocyclotriphosphazene using chlorobenzene as a solvent and PCl5 as a raw material, the reaction yield of hexachlorocyclotriphosphazene can reach more than 90%, basically achieving the same or similar experimental results as when using fresh pyridine as an acid-binding agent, fresh metal chloride as a catalyst, and fresh ammonium chloride as a raw material.

[0066] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue, characterized in that... Includes the following steps: 1) The waste residue separated after the synthesis reaction of hexachlorocyclotriphosphazene is reacted with an ammonia source, and the final pH value is adjusted to 6-10 to obtain the reaction product. The ammonia source is liquid ammonia, ammonia gas, ammonia water, ammonium bicarbonate, ammonium carbonate or a combination thereof. 2) The reaction product described in step 1) is subjected to solid-liquid separation to obtain filtrate and filter cake; 3) Extract the filtrate from step 2) with chlorobenzene to obtain the extract phase and the raffinate phase; 4) The extract phase obtained in step 3) is distilled to obtain chlorobenzene and recovered pyridine or pyridine derivatives; In step 4), the extract phase is first dehydrated by azeotropic distillation, molecular sieve dehydration, or pervaporation membrane dehydration to obtain a dehydrated extract phase. Then, the dehydrated extract phase is distilled to obtain recovered pyridine or pyridine derivatives and chlorobenzene from the top of the column. The remaining bottom liquid is reused in step 3) as an extractant. The recovered pyridine or pyridine derivatives contain ≤90% chlorobenzene, which is reused as an acid-binding agent in the reaction to prepare hexachlorocyclotriphosphazene using chlorobenzene as solvent and PCl5 and NH4Cl as raw materials.

2. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 1, characterized in that... In step 1), the reaction temperature is 0-50℃.

3. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 1, characterized in that... In step 1), the waste residue is mixed with water and then reacted with the ammonia source. The mass ratio of waste residue to water is 1:0.5~5.

4. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 1, characterized in that... In step 1), the pH endpoint is adjusted to 6-9.

5. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 1, characterized in that... The filter cake is reacted with hydrochloric acid and then dehydrated to obtain the recovered metal chloride catalyst; the recovered metal chloride catalyst is used as a catalyst in the reaction to prepare hexachlorocyclotriphosphazene.

6. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 1, characterized in that... In step 3), the extraction is either intermittent extraction or countercurrent continuous extraction. The number of intermittent extractions is 1-5 times, and the amount of chlorobenzene used as the extractant in each intermittent extraction is 0.5-5 times the mass of water in the filtrate. In the countercurrent continuous extraction, the ratio of the mass flow rate of the extractant to the mass flow rate of the filtrate is 0.5-3:

1.

7. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 1, characterized in that... The raffinate phase obtained in step 3) is dehydrated to obtain recovered ammonium chloride.

8. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 1 or 7, characterized in that... The raffinate phase is dehydrated by a process including azeotropic distillation, concentration and drying. First, azeotropic distillation is performed to remove 10-30% of the water in the raffinate phase. The fraction distilled by azeotropic distillation is used in step 3) for extraction. Then, concentration and drying are performed. After dehydration, the ammonium chloride water content is ≤1%. The water recovered from concentration and drying is used in step 2) as filter cake washing water and / or in step 1) for mixing with waste residue.

9. The process for resource recovery of hexachlorocyclotriphosphazene synthesis waste residue as described in claim 7, characterized in that... The recovered ammonium chloride is used as a raw material in the reaction to prepare hexachlorocyclotriphosphazene.

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