Method for purifying toluene containing titanium tetrachloride

Abstract

This invention relates to the field of toluene recovery and purification, and discloses a method for purifying toluene containing titanium tetrachloride. The method includes: i) washing the titanium tetrachloride-containing toluene with washing water under acidic or neutral conditions, separating it into a first oil phase and a first aqueous phase; ii) washing the first oil phase with washing water under pH 6-8 conditions, separating it into a second oil phase and a second aqueous phase; iii) washing the second oil phase with washing water under pH 7-8 conditions, separating it into a third oil phase and a third aqueous phase. The purification method for titanium tetrachloride-containing toluene provided by this invention has the advantages of low water and titanium compound residues, and the resulting water-washed toluene will not cause corrosion or blockage of distillation equipment when used for further distillation and purification.

Description

Technical Field

[0001] This invention relates to the field of toluene recovery and purification, and more specifically to a method for purifying toluene containing titanium tetrachloride. Background Technology

[0002] The production of granular polyolefin catalysts mainly uses toluene and hexane as solvents and detergents. In the initial stage of catalyst synthesis, a large amount of toluene is added to the reaction system as a solvent. After the reaction media dissolve in toluene, a homogeneous solution is formed. Then, the active material, titanium tetrachloride, is added. After a series of processes (including temperature adjustment and the addition of additives), granular polyolefin catalysts are formed. Then, the catalyst is cleaned step by step using the detergents toluene and hexane to obtain the granular polyolefin catalyst product.

[0003] During the production process, a large amount of solvent and excess active material titanium tetrachloride are separated from the catalyst to form a mixed solution. This solution then enters a solvent recovery unit for further separation and can be reused in catalyst synthesis. This separation process mainly uses physical methods such as distillation and rectification to separate toluene, titanium tetrachloride, and hexane based on their different boiling points. However, after rectification, a small amount of titanium tetrachloride remains in the toluene, making it unsuitable as a direct solvent for the initial stage of granular polyolefin catalyst synthesis. Therefore, water washing is generally used to treat the toluene, utilizing the reaction between titanium tetrachloride and water to decompose and destroy the remaining small amount of titanium tetrachloride in the toluene. Further purification of the toluene is then achieved through rectification. The washed toluene still contains a small amount of water, which in turn contains a certain amount of titanium compounds. The water containing titanium compounds has a neutral pH (≈7), but during rectification, the titanium compounds will further decompose to form HCl and titanium oxides. HCl combines with water to form hydrochloric acid, which continuously accumulates and concentrates, ultimately leading to corrosion and damage to the components inside the rectification equipment and the top condenser. Furthermore, titanium oxides will deposit on the components inside the rectification equipment, causing blockages. Summary of the Invention

[0004] In existing technologies, the water washing process for toluene containing titanium tetrachloride leaves traces of water and titanium compounds, which can cause corrosion and blockage of subsequent distillation equipment. To overcome these problems, this invention provides a method for purifying toluene containing titanium tetrachloride. The purification method for toluene containing titanium tetrachloride provided by this invention has the advantages of low residual water and titanium compounds, and the resulting water-washed toluene will not cause corrosion or blockage of distillation equipment when used for further distillation and purification.

[0005] The following provides a detailed description of the purification method for toluene containing titanium tetrachloride provided by this invention. It should be understood that the description herein is for illustrative and explanatory purposes only and is not intended to limit the invention. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of various ranges, the endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0006] This invention provides a method for purifying toluene containing titanium tetrachloride. The method includes: i) washing the titanium tetrachloride-containing toluene with washing water under acidic or neutral conditions, separating it into a first oil phase and a first aqueous phase; ii) washing the first oil phase with washing water under pH 6-8 conditions, separating it into a second oil phase and a second aqueous phase; iii) washing the second oil phase with washing water under pH 7-8 conditions, separating it into a third oil phase and a third aqueous phase, wherein the third oil phase is the target product, washed toluene. The purification method with the aforementioned characteristics has the advantage of low residual water and titanium compounds in the obtained washed toluene, and will not cause corrosion or blockage of the distillation equipment when used for further distillation and purification.

[0007] In this invention, the washing method is not particularly limited; any suitable method can be selected as long as it achieves the purpose of this invention. According to a preferred embodiment of this invention, steps i) and / or ii) and / or iii) are performed by spraying. The washing method with the aforementioned characteristics allows for sufficient contact between the washing water and the target material, enabling complete hydrolysis of titanium tetrachloride, improving the washing effect, and reducing the residual amount of titanium compounds in the washed toluene.

[0008] According to a preferred embodiment of the present invention, step i) includes: (1) washing toluene containing titanium tetrachloride with washing water under acidic or neutral conditions, and separating the layers to obtain an oil phase and an aqueous phase; (2) washing the oil phase of step (1) with washing water under acidic or neutral conditions, and separating the layers to obtain an oil phase and an aqueous phase, wherein the oil phase of step (2) is the first oil phase, and the aqueous phase of step (2) is the first aqueous phase. Step i) with the aforementioned features can fully hydrolyze titanium tetrachloride, improve the washing effect, and reduce the residual amount of titanium compounds in the washed toluene.

[0009] Furthermore, according to a more preferred embodiment of the present invention, in step (1) and / or step (2), the aqueous phase is recycled for washing water. Step i), having the aforementioned features, can reduce the amount of washing water used.

[0010] In this invention, the amount of washing water used in step (1) can be selected from a wide range. The following is an illustrative example, but it does not limit the scope of this invention. According to a preferred embodiment of the invention, the volume of the washing water is 10% or more of the volume of toluene containing titanium tetrachloride, preferably 10-20%. The amount of washing water with the aforementioned characteristics enables the titanium tetrachloride to be fully hydrolyzed, improving the washing effect and reducing the residual amount of titanium compounds in the washed toluene.

[0011] In this invention, the amount of washing water used in step (2) can be selected from a wide range. The following is an illustrative example, but it does not limit the scope of this invention. According to a preferred embodiment of the invention, the volume of the washing water is more than 10% of the volume of the oil phase in step (1), preferably 10-20%. The amount of washing water with the aforementioned characteristics can fully hydrolyze titanium tetrachloride, improve the washing effect, and reduce the residual amount of titanium compounds in the water-washed toluene.

[0012] According to a preferred embodiment of the present invention, in step i), the first aqueous phase is recycled for washing water. Step i), having the aforementioned features, can reduce the amount of washing water used.

[0013] In this invention, in step i), the acidic conditions can be achieved by using dilute hydrochloric acid as the washing water, as illustrated below, but without limiting the scope of the invention. For example, the washing water can be dilute hydrochloric acid with a concentration of 0.01-2 wt%.

[0014] According to a preferred embodiment of the present invention, in step iii), the washing water is the second aqueous phase of step ii). Step iii), having the aforementioned features, can reduce the amount of washing water used.

[0015] In this invention, the washing temperature in step iii) can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the washing temperature is 60-100°C, preferably 70-90°C. In this preferred embodiment, in step iii), "a pH value of 7-8" refers to the pH value at the aforementioned washing temperature. The washing temperature can be, for example, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C. Washing temperatures with the aforementioned characteristics allow for complete hydrolysis of titanium tetrachloride, improving the washing effect and reducing the residual amount of titanium compounds in the washed toluene.

[0016] In this invention, the separation method in step iii) is not particularly limited; any suitable method can be selected as long as it achieves the purpose of this invention. According to a preferred embodiment of this invention, the separation method is centrifugal separation. The separation method with the aforementioned characteristics can reduce the residual amounts of water and titanium compounds in the washed toluene and shorten the separation time.

[0017] According to a preferred embodiment of the present invention, in step iii), the third aqueous phase is used in the washing water of step i). Step iii), having the aforementioned features, can reduce the amount of washing water used.

[0018] According to a preferred embodiment of the present invention, the purification method for toluene containing titanium tetrachloride provided by the present invention further includes: iv) allowing the third oil phase to stand and separate into an oil phase and an aqueous phase; performing pH detection on the aqueous phase obtained in step iv); if the detected pH value is not within the target value of 7-8, then repeating steps iii)-iv) on the third oil phase; if the detected pH value is within the target value of 7-8, then using the third oil phase as the target product for water washing toluene; preferably, taking 90-95% of the liquid volume from the top of the third oil phase as the target product for water washing toluene, and repeating steps i)-iv) on the remaining liquid of the third oil phase. The purification method for toluene containing titanium tetrachloride with the aforementioned characteristics can reduce the residual amount of water and titanium compounds in the water-washed toluene.

[0019] In this invention, the settling time in step iv) can be selected within a wide range, as illustrated below, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the settling time is not less than 8 hours.

[0020] In this invention, the amount of washing water used in step i) can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the volume of the washing water is 10% or more of the volume of toluene containing titanium tetrachloride, preferably 10-20%. The amount of washing water with the aforementioned characteristics enables the titanium tetrachloride to be fully hydrolyzed, improving the washing effect and reducing the residual amount of titanium compounds in the washed toluene.

[0021] In this invention, the amount of washing water used in step ii) can be selected from a wide range. The following is an illustrative example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the volume of the washing water is 20% or more of the volume of the first oil phase, preferably 20%-30%. The amount of washing water with the aforementioned characteristics enables the complete hydrolysis of titanium tetrachloride, improves the washing effect, and reduces the residual amount of titanium compounds in the washed toluene.

[0022] In this invention, the amount of washing water used in step iii) can be selected from a wide range. The following is an illustrative example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the volume of the washing water is 20% or more of the volume of the second oil phase, preferably 20%-30%. The amount of washing water with the aforementioned characteristics enables the complete hydrolysis of titanium tetrachloride, improves the washing effect, and reduces the residual amount of titanium compounds in the washed toluene.

[0023] In this invention, the content of titanium tetrachloride in the toluene containing titanium tetrachloride can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the content of titanium tetrachloride in the toluene containing titanium tetrachloride is ≤10 wt%, preferably 2-8 wt%.

[0024] In this invention, the source of the titanium tetrachloride-containing toluene is not particularly limited; any suitable source can be selected as long as it achieves the purpose of this invention. According to a preferred embodiment of this invention, the titanium tetrachloride-containing toluene is recovered toluene obtained by distillation separation of the mixed solvent generated during the production of granular polyolefin catalysts.

[0025] In this invention, the pH condition in steps ii) and iii) can be achieved using a pH adjuster. There is no particular limitation on the type of pH adjuster; any suitable type can be selected as long as it achieves the purpose of this invention. According to a preferred embodiment of this invention, in steps ii) and iii), the pH adjuster is independently an alkaline aqueous solution, such as a NaOH aqueous solution.

[0026] In this invention, the concentration of alkali in the alkaline aqueous solution can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the concentration of alkali in the alkaline aqueous solution is 10-20 wt%. The alkaline aqueous solution with the aforementioned characteristics can fully hydrolyze titanium tetrachloride, improve the washing effect, and reduce the residual amount of titanium compounds in the water-washed toluene.

[0027] In this invention, the washing equipment is not particularly limited; any suitable equipment can be selected as long as it can achieve the purpose of this invention. According to a preferred embodiment of the invention, the washing equipment is an acid-resistant device; preferably, the washing equipment includes an agitator; more preferably, the washing equipment includes a multi-layer agitator.

[0028] In this invention, the circulation can be achieved by a pump. There is no particular limitation on the type of pump; any suitable type can be selected as long as it achieves the purpose of this invention. According to a preferred embodiment of this invention, the pump is an acid-resistant pump, preferably an acid- and alkali-resistant pump, and more preferably an acid-, alkali-, and toluene-resistant pump.

[0029] The purification method for toluene containing titanium tetrachloride provided by this invention has the advantages of low water and titanium compound residues, and the resulting water-washed toluene will not cause corrosion or blockage to the distillation equipment when used for further distillation and purification. Detailed Implementation

[0030] The present invention will be described in detail below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0031] For any experimental steps or conditions not specified in the examples and comparative examples, the procedures and conditions described in the literature in this field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0032] Example 1

[0033] i):

[0034] (1) Toluene containing 5 wt% titanium tetrachloride was sprayed and washed with washing water with a pH of 7, and the oil phase and water phase were separated by layering. The water phase was pumped out and recycled for spray washing in step (1). The volume of washing water was 15% of the volume of toluene containing titanium tetrachloride.

[0035] (2) The oil phase in step (1) is sprayed and washed with washing water with a pH of 7, and the first oil phase and the first water phase are separated by layer. The first water phase is pumped out and recycled for spray washing in step (2). The volume of the washing water is 15% of the volume of the oil phase in step (1).

[0036] ii): The first oil phase is sprayed and washed with washing water with a pH of 7 to form a second oil phase and a second aqueous phase, wherein the volume of the washing water is 25% of the volume of the first oil phase.

[0037] iii): Heat to 80°C, use a pump to extract the second aqueous phase, use a 20wt% NaOH aqueous solution to adjust the pH of the second aqueous phase to 8, use the pH-adjusted second aqueous phase to spray wash the second oil phase, centrifuge to separate the third oil phase and the third aqueous phase, use a pump to extract the third aqueous phase and recycle it for spray washing in step i).

[0038] iv): The third oil phase was allowed to stand for 9 hours to separate into an oil phase and an aqueous phase. The pH of the aqueous phase obtained in step iv) was measured using precision pH paper, and the measured pH value was 7.3. 90% of the liquid from the top of the third oil phase was used to wash toluene. The remaining liquid from the third oil phase was used to repeat steps i) to iv).

[0039] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 No corrosion or blockage occurred in the distillation equipment after 120 days of continuous operation.

[0040] Example 2

[0041] The method of Example 1 is different except that in step (1), the volume of the washing water is 7% of the volume of toluene containing titanium tetrachloride; and in step (2), the volume of the washing water is 6% of the volume of the oil phase in step (1).

[0042] In step iv), the pH of the aqueous phase obtained in step iv) is tested using precision pH test paper. The pH value is 6.3, which is not within the target value of 7-8. Steps iii)-iv) are repeated for the third oil phase. The pH of the aqueous phase in the second step iv) is tested again using precision pH test paper. The pH value is 7.0.

[0043] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 No corrosion or blockage occurred in the distillation equipment after 120 days of continuous operation.

[0044] Example 3

[0045] The method is the same as in Example 2, except that step iv is omitted.

[0046] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 The distillation equipment corroded after 97 days of continuous operation and required equipment repair.

[0047] Example 4

[0048] The method is the same as in Example 1, except that in step ii), the volume of the washing water is 17% of the volume of the first oil phase.

[0049] In step iv), the pH of the aqueous phase obtained in step iv) is measured using precision pH test paper. The measured pH value is 6.7, which is not within the target value of 7-8. Steps iii)-iv) are repeated for the third oil phase. The pH of the aqueous phase in the second step iv) is measured again using precision pH test paper. The measured pH value is 7.2.

[0050] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 No corrosion or blockage occurred in the distillation equipment after 120 days of continuous operation.

[0051] Example 5

[0052] The method is the same as in Example 1, except that in step ii), the washing temperature is 60°C.

[0053] In step iv), the pH of the aqueous phase obtained in step iv) is measured using precision pH test paper, and the measured pH value is 7.0.

[0054] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 The distillation equipment became clogged after running continuously for 109 days and required equipment repair.

[0055] Example 6

[0056] The method is the same as in Example 1, except that in step iv), the third oil phase is entirely washed with water toluene.

[0057] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 The distillation equipment became clogged after running continuously for 106 days and required equipment repair.

[0058] Example 7

[0059] The method of Example 1 is different except that step i) is: to spray wash the toluene containing 5 wt% titanium tetrachloride with washing water with a pH of 7, and separate the layers to obtain a first oil phase and a first aqueous phase. The first aqueous phase is pumped out and recycled for spray wash in step i). The volume of the washing water is 15% of the volume of the toluene containing titanium tetrachloride.

[0060] In step iv), the pH of the aqueous phase obtained in step iv) is tested using precision pH test paper. The pH value is 6.4, which is not within the target value of 7-8. Steps iii)-iv) are repeated for the third oil phase. The pH of the aqueous phase in the second step iv) is tested again using precision pH test paper. The pH value is 7.3.

[0061] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 No corrosion or blockage occurred in the distillation equipment after 120 days of continuous operation.

[0062] Example 8

[0063] The method is the same as in Example 1, except that in steps (1) and (2), the washing water is 0.1 wt% dilute hydrochloric acid.

[0064] In step iv), the pH of the aqueous phase obtained in step iv) is measured using precision pH test paper, and the measured pH value is 7.0.

[0065] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3No corrosion or blockage occurred in the distillation equipment after 120 days of continuous operation.

[0066] Comparative Example 1

[0067] Toluene containing 5 wt% titanium tetrachloride was sprayed and washed with washing water with a pH of 7, and the layers were separated to obtain a first oil phase and a first aqueous phase. The first oil phase is the water-washed toluene.

[0068] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 The distillation equipment corroded after 58 days of continuous operation and required equipment repair.

[0069] Comparative Example 2

[0070] The method is the same as in Example 1, except that steps iii)-iv) are not performed, and the second oil phase is water-washed toluene.

[0071] Toluene washed with water is fed into a distillation unit for distillation and purification to obtain toluene. The daily processing capacity of the washed toluene is set at 17m³. 3 The distillation equipment corroded after 69 days of continuous operation and required equipment repair.

[0072] The method for purifying toluene containing titanium tetrachloride provided by this invention has been described in detail above; however, this invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solution of this invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, this invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as part of the content disclosed in this invention and are all within the protection scope of this invention.

Claims

1. A method for purifying toluene containing titanium tetrachloride, characterized in that, The method includes: i) Under acidic or neutral conditions, toluene containing titanium tetrachloride is washed with washing water and separated into layers to obtain a first oil phase and a first aqueous phase; ii) Under conditions of pH 6-8, the first oil phase is washed with washing water to form a second oil phase and a second aqueous phase. iii) Under pH conditions of 7-8, the second oil phase is washed with washing water to separate the third oil phase and the third aqueous phase.

2. The purification method according to claim 1, wherein, Step i) and / or steps ii) and / or steps iii) are performed by spraying.

3. The purification method according to claim 1, wherein, Step i) includes: (1) Under acidic or neutral conditions, toluene containing titanium tetrachloride is washed with washing water and separated into oil and water phases. (2) Under acidic or neutral conditions, the oil phase of step (1) is washed with washing water and separated into oil phase and water phase, wherein the oil phase of step (2) is the first oil phase and the water phase of step (2) is the first water phase.

4. The purification method according to claim 3, wherein, In step i), In step (1) and / or step (2), the aqueous phase is recycled for washing water; and / or In step (1), the volume of the washing water is at least 10% of the volume of toluene containing titanium tetrachloride, preferably 10-20%; and / or In step (2), the volume of the washing water is more than 10% of the volume of the oil phase in step (1), preferably 10-20%.

5. The purification method according to claim 1, wherein, In step i), the first aqueous phase is recycled for washing water.

6. The purification method according to claim 1, wherein, In step iii), The wash water is the second aqueous phase of step ii); and / or The washing temperature is 60-100℃, preferably 70-90℃.

7. The purification method according to claim 1, wherein, In step iii), Separation is performed by centrifugation; and / or The third aqueous phase is used for the washing water in step i).

8. The purification method according to claim 1, wherein, The method also includes: iv) The third oil phase is allowed to stand and separate into oil and water phases. The pH of the water phase obtained in step iv) is tested. If the pH value is not within the target value of 7-8, the third oil phase is repeated in steps iii)-iv). If the pH value is within the target value of 7-8, the third oil phase is used as the target product to wash toluene. Preferably, 90-95% of the liquid in the upper part of the third oil phase is used as the target product to wash toluene, and the remaining liquid in the third oil phase is repeated in steps i)-iv).

9. The purification method according to claim 1, wherein, In step i), the volume of the washing water is at least 10% of the volume of toluene containing titanium tetrachloride, preferably 10-20%; and / or In step ii), the volume of the washing water is at least 20% of the volume of the first oil phase, preferably 20%-30%; and / or In step iii), the volume of the washing water is more than 20% of the volume of the second oil phase, preferably 20%-30%.

10. The purification method according to claim 1, wherein, In toluene containing titanium tetrachloride, the content of titanium tetrachloride is ≤10 wt%, preferably 2-8 wt%; and / or Toluene containing titanium tetrachloride is a recovered toluene obtained by distillation separation of mixed solvents generated during the production of particulate polyolefin catalysts.