Method for detecting titanium content in a titanium-containing reagent, method for detecting titanium content in a polyolefin catalyst

Abstract

This invention relates to the field of materials determination technology, and discloses a method for detecting the titanium content in a titanium-containing reagent and a method for detecting the titanium content in a polyolefin catalyst. The method includes the following steps: (1) under an inert gas protective environment, the titanium-containing reagent is acid-hydrolyzed and reduced to obtain a trivalent titanium ion sample solution; (2) under an inert gas protective environment, ferric ammonium sulfate solution is added dropwise to the sample solution, and the potential is tested using a redox electrode during the addition process. The titration endpoint is determined based on the redox electrode potential threshold, and the titanium content is calculated based on the amount of ferric ammonium sulfate solution added at the titration endpoint. This detection method is green and environmentally friendly, and improves the accuracy of the detection results while reducing the detection cost.

Description

Technical Field

[0001] This invention relates to the field of materials testing technology, specifically to a method for detecting the titanium content in titanium-containing reagents and a method for detecting the titanium content in polyolefin catalysts. Background Technology

[0002] Titanium is the active component in olefin polymerization catalysts, and its content and chemical form affect the performance of these catalysts. Controlling the titanium content in catalysts is a challenge in catalyst preparation. For the analysis of titanium content in catalysts, the testing methods need to be highly precise and accurate.

[0003] Currently, the industry commonly uses the hydrogen peroxide colorimetric-spectrophotometric method to test titanium content. This method requires the use of 30% hydrogen peroxide for colorimetric development and n-heptane extraction to separate organic impurities. Hydrogen peroxide is an explosive chemical, and n-heptane is a flammable chemical; their storage, use, and waste disposal all pose certain HSE risks. With increasingly stringent laboratory HSE management requirements, there is an urgent need to develop a novel, environmentally friendly method for testing titanium content in catalysts to replace the hydrogen peroxide and n-heptane reagents used in the original method, thereby fundamentally improving the HSE level of the method.

[0004] GB-4701 provides a manual redox titration method for testing the titanium content in ferro-titanium alloys. However, due to the complexity of the operating equipment and the difficulty in stably controlling the operating temperature and the isolation of air, the test results are unstable and it has not been widely used. Summary of the Invention

[0005] The purpose of this invention is to overcome the safety risks and unstable test results of existing technologies, and to provide a method for detecting titanium content in polyolefin catalysts. This method is green and environmentally friendly, and improves the accuracy of test results while reducing test costs.

[0006] To achieve the above objectives, the present invention provides a method for detecting the titanium content in a titanium-containing reagent, the method comprising the following steps: (1) Under an inert gas protective environment, the titanium-containing reagent was acid-hydrolyzed and reduced to obtain a trivalent titanium ion test sample solution; (2) Under an inert gas protective environment, ferric ammonium sulfate solution is added dropwise to the sample solution to be tested, and the potential is tested by an oxidation-reduction electrode during the dropwise process. The titration endpoint is determined according to the potential threshold of the oxidation-reduction electrode, and the titanium content is calculated according to the amount of ferric ammonium sulfate solution added at the titration endpoint.

[0007] A second aspect of this invention provides a method for detecting the titanium content in a polyolefin catalyst, employing the method described herein for detecting the titanium content in a titanium-containing reagent. This method includes the following steps: i) Under an inert gas protective environment, the polyolefin catalyst was acid-hydrolyzed and reduced to obtain the trivalent titanium ion test sample solution; ii) Under an inert gas protective environment, ferric ammonium sulfate solution is added dropwise to the sample solution to be tested, and the potential is tested using an oxidation-reduction electrode during the dropwise process. The titration endpoint is determined according to the oxidation-reduction electrode potential threshold, and the titanium content is calculated based on the amount of ferric ammonium sulfate solution added at the titration endpoint.

[0008] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The method for detecting titanium content in titanium-containing reagents provided by the present invention detects titanium content by titration with ferric ammonium sulfate, eliminating the need for hydrogen peroxide color development, thus avoiding the use of hydrogen peroxide as an easily explosive chemical, and without introducing the use of other easily explosive chemicals, thereby reducing the safety risks of reagent management and operation.

[0009] 2. The method provided by this invention allows for direct titration with ferric ammonium sulfate after the titanium-containing reagent is reduced by acid hydrolysis, eliminating the need for pretreatment such as shaking separation, extraction, washing, separation of organic phase, and volume adjustment, thus greatly reducing the number of operation steps and saving pretreatment costs.

[0010] 3. The method provided by this invention features high continuity, strong anti-interference capability, accuracy, and high efficiency. Compared with traditional spectrophotometry, the measurement and testing steps are reduced from 10 to 2, significantly shortening the detection time for a single sample, greatly improving testing efficiency, and saving labor costs. It can more accurately and efficiently serve production and scientific research work.

[0011] 4. When using the detection method described in this invention to determine the titanium content of polyolefin catalysts with a titanium content of 1.5-4 wt%, the absolute difference is no greater than 0.1%, and when determining the titanium content of polyolefin catalysts with a titanium content of 4-6.5 wt%, the absolute difference is no greater than 0.2%. This effect far exceeds the detection methods for determining the titanium content of polyolefin catalysts disclosed in the prior art. Detailed Implementation

[0012] 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 the various ranges, the endpoint values ​​of the 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.

[0013] In this invention, the detection process can be linked with analytical balances, LIMS systems, etc., to automatically complete the reading of sample quality data and the reporting of test results, thereby further improving testing efficiency and data traceability.

[0014] According to one aspect of the present invention, a method for detecting the titanium content in a titanium-containing reagent is provided, the method comprising the following steps: (1) Under an inert gas protective environment, the titanium-containing reagent was acid-hydrolyzed and reduced to obtain a trivalent titanium ion test sample solution; (2) Under an inert gas protective environment, ferric ammonium sulfate solution is added dropwise to the sample solution to be tested, and the potential is tested by an oxidation-reduction electrode during the dropwise process. The titration endpoint is determined according to the potential threshold of the oxidation-reduction electrode, and the titanium content is calculated according to the amount of ferric ammonium sulfate solution added at the titration endpoint.

[0015] According to one embodiment of the present invention, the formula for calculating the titanium content is as follows: ; In the formula: V – The volume of ferric ammonium sulfate standard titration solution consumed in the titration, in milliliters (mL). c – Concentration of the ferric ammonium sulfate standard titration solution, in moles per liter (mol / L). m — the numerical value of sample mass, in grams (g).

[0016] In this invention, titanium content is detected by titration with ferric ammonium sulfate, eliminating the need for hydrogen peroxide color development and avoiding the use of hydrogen peroxide, a potentially explosive chemical. Furthermore, it avoids the introduction of other potentially explosive chemicals, reducing safety risks associated with reagent management and the operational process. Titanium-containing reagents, after acidolysis and reduction, can be directly titrated with ferric ammonium sulfate without the need for pretreatment processes such as shaking separation, extraction, washing, separation of the organic phase, and volume adjustment. This significantly reduces operational steps and pretreatment costs.

[0017] In this invention, there is no particular limitation on the scope of titanium-containing reagents. The following is an example description, but it does not limit the scope of this invention. According to one embodiment of this invention, the titanium-containing reagent is selected from one or more of polyolefin catalysts, metallurgical materials, and aerospace materials, such as polyethylene catalysts, polypropylene catalysts, polybutene catalysts, titanium-iron alloys, titanium dioxide, aerospace titanium steel, TC titanium alloys, and TB titanium alloys.

[0018] In this invention, the method is preferably carried out in a container equipped with a redox electrode, which is fixed above the bottom of the container. This is an illustrative description and does not affect the scope of the invention. According to one embodiment of the invention, the electrode test area is controlled to not come into contact with the solution during the acidolysis reduction process. The acidolysis reduction process is highly exothermic, and premature contact of the electrode will cause it to be heated, leading to abnormal response and identification in subsequent testing steps.

[0019] According to one embodiment of the present invention, after the acidolysis reduction is completed, deionized water is added to the container so that the electrode test part is immersed in the sample solution to be tested. Only when the electrode is completely immersed in the sample solution to be tested and in full contact with the solution can the potential change of the sample solution to be tested be accurately measured and the titration endpoint be identified.

[0020] In this invention, the redox electrode is placed in a container to facilitate the implementation of the invention, but this does not limit the scope of the invention. For example, the redox electrode can be added before titration without damaging the inert gas protective environment or affecting the acidolysis reduction process. It is worth noting that the test part of the redox electrode must be completely immersed in the sample solution to ensure the detection effect of the invention.

[0021] According to one embodiment of the present invention, the acid hydrolysis reduction step includes: In an inert gas protected environment, titanium-containing reagents are mixed with reducing agents and subjected to acidolysis reduction in an acidic solution containing HCl and / or H2SO4.

[0022] In this invention, the type of reducing agent is not particularly limited, as long as it does not affect the effect of this invention. The following is an example, but it does not limit the scope of this invention. According to one embodiment of this invention, the reducing agent includes one or more of aluminum foil and sulfides, preferably aluminum foil.

[0023] In this invention, the formulation of the acid solution is not particularly limited. The following is an example, but it does not limit the scope of the invention. According to one embodiment of the invention, the acid solution contains: HCl with a concentration of 1~5 mol / L, preferably 2~4 mol / L; and H2SO4 with a concentration of 0.02~0.07 mol / L, preferably 0.03~0.05 mol / L.

[0024] In this invention, there are no special requirements for the specific amounts of titanium-containing reagents, acid solutions, and reducing agents used, as long as the tetravalent Ti in the titanium-containing reagent is completely reduced to trivalent Ti.

[0025] According to one embodiment of the present invention, the acid hydrolysis reduction conditions include: the acid hydrolysis reduction time is 1 to 10 minutes, preferably 5 to 8 minutes.

[0026] According to one embodiment of the present invention, the conditions for acid hydrolysis reduction include: the acid hydrolysis reduction temperature is 45~65℃.

[0027] According to one embodiment of the present invention, the conditions for acid hydrolysis reduction include: the acid hydrolysis reduction process adopts water bath heating, and the container used for acid hydrolysis reduction is heated by water bath. This method can make the heating more uniform and is conducive to the technical implementation of the present invention.

[0028] According to one embodiment of the present invention, the conditions for acid hydrolysis reduction include: acid hydrolysis reduction is carried out under dynamic conditions, and the stirring speed is 500-1000 rpm.

[0029] In this invention, the concentration of the ferric ammonium sulfate solution in step (2) is not particularly limited. The following is an example, but it does not limit the scope of the invention. According to one embodiment of the invention, the Fe in the ferric ammonium sulfate solution... 3+ The concentration is 0.01~0.1mol / L, preferably 0.01~0.02mol / L.

[0030] In this invention, there are no special limitations on the dropping rate and dropping interval of the ferric ammonium sulfate solution in step (2). The following is an example, but it does not limit the scope of this invention. According to one embodiment of this invention, the dropping rate of the ferric ammonium sulfate solution is 0.01~0.04mL / s, and the dropping interval is 3~8s.

[0031] In this invention, a foil ring composite electrode is used as an example of a redox electrode, but this does not limit the scope of the invention. For example, it can also be used to produce new electrode products that meet the requirements of pH tolerance and heat tolerance, as long as they are verified to be able to operate stably for a long time.

[0032] According to one embodiment of the present invention, in steps (1) and (2), the inert gas each includes nitrogen and / or carbon dioxide gas.

[0033] According to one embodiment of the present invention, in steps (1) and (2), the flow rate of the inert gas introduced is 180~240 mL / min.

[0034] According to a second aspect of the present invention, a method for detecting the titanium content in a polyolefin catalyst is provided. The method for detecting the titanium content in a titanium-containing reagent according to the present invention includes the following steps: i) Under an inert gas protective environment, the polyolefin catalyst was acid-hydrolyzed and reduced to obtain the trivalent titanium ion test sample solution; ii) Under an inert gas protective environment, ferric ammonium sulfate solution is added dropwise to the sample solution to be tested, and the potential is tested using an oxidation-reduction electrode during the dropwise process. The titration endpoint is determined according to the oxidation-reduction electrode potential threshold, and the titanium content is calculated based on the amount of ferric ammonium sulfate solution added at the titration endpoint.

[0035] In this invention, titanium content is detected by titration with ferric ammonium sulfate, eliminating the need for hydrogen peroxide color development and avoiding the use of hydrogen peroxide, a potentially explosive chemical. Furthermore, it avoids the introduction of other potentially explosive chemicals, reducing safety risks associated with reagent management and the operational process. Polyolefin catalysts, after acid hydrolysis and reduction, can be directly titrated with ferric ammonium sulfate without the need for pretreatment processes such as shaking separation, extraction, washing, separation of the organic phase, and volume adjustment, significantly reducing operational steps and pretreatment costs.

[0036] When the detection method described in this invention is used to determine the titanium content of polyolefin catalysts with a titanium content of 1.5-4 wt%, the absolute difference is no greater than 0.1%, and when the titanium content of polyolefin catalysts with a titanium content of 4-6.5 wt%, the absolute difference is no greater than 0.2%. This effect far exceeds the detection methods for determining the titanium content of polyolefin catalysts disclosed in the prior art.

[0037] According to one embodiment of the present invention, the polyolefin catalyst is selected from one or more of polyethylene, polypropylene, and polybutene catalysts, preferably polyethylene and / or polypropylene catalysts. The embodiments of the present invention specifically use polyethylene and polypropylene catalysts as examples to illustrate the advantages of the present invention, but are not intended to limit the present invention.

[0038] In this invention, the composition of the polyolefin catalyst is not particularly limited, and commonly used titanium-containing polyolefin catalysts can be detected using the method of this invention. The following is an exemplary description, but it does not limit the scope of this invention. According to one embodiment of this invention, the composition of the polyolefin catalyst includes: titanium, magnesium, chlorine, phthalate, hexane, ethoxy, and furan, wherein the titanium content is 1.5~10 wt%.

[0039] In this invention, there are no special limitations on the amount of reagents added or the reaction conditions in the acid hydrolysis reduction. The following examples illustrate this, but do not limit the scope of the invention. For example, in the detection of titanium content in polyolefin catalysts, the sample weight of polyolefin catalyst is 30-100 mg, the sample weight of aluminum foil is 180-220 mg, and the acid solution is 15-40 mL.

[0040] The remaining steps and conditions have been disclosed above and will not be repeated here.

[0041] According to a preferred embodiment of the present invention, an automatic method for detecting the titanium content of a polyolefin catalyst is as follows: A nitrogen generator is used to control the nitrogen flow rate, and the nitrogen is delivered to the acidolysis reduction unit through pipelines; The water bath temperature is controlled by a constant temperature water bath, and the water temperature of the water bath tank or water bath jacket where the acidolysis reduction unit is located is controlled by the external circulation of the water bath. The control transfer unit moves the container containing the polyolefin catalyst sample and aluminum foil to the acid hydrolysis reduction unit; The acid solution feeding unit is controlled to add the prepared acid solution to the container; The reagent in the container was stirred by controlling the stirrer, and the acid hydrolysis and reduction yielded the trivalent titanium ion test sample solution; The deionized water feeding unit is controlled to add deionized water to the container, raising the water level of the sample solution in the container until the redox electrode testing area is submerged in the sample solution; Controlling the potential of the sample solution in the redox electrode measuring container; The addition of ferric ammonium sulfate solution to the ferric ammonium sulfate solution feeding unit is controlled, and the redox electrode potential and the corresponding amount of ferric ammonium sulfate solution added are recorded. The computer determines the titration endpoint based on the redox electrode potential threshold, calculates the titanium content, and outputs the calculation results.

[0042] The present invention will be described in detail below through examples. In the following examples, HCl and H2SO4 of a certain concentration were prepared on-site and were commercially available products; the catalyst raw materials were commercially available products from Sinopec Catalyst Co., Ltd.; the redox electrode was a product sold by Mettler Toledo or Metrohm AG, model DMI-147; and the automatic acid-base titrator was model T7.

[0043] Example 1 During acid hydrolysis and reduction, the electrode testing area is not in contact with the solution; Five polyolefin catalyst samples with different titanium content levels (determined by spectrophotometry) were selected, and the titanium content is shown in the table below: experimental group category Titanium content / wt% Level 1 Gas phase polypropylene catalyst 2.85 Level 2 Spherical polypropylene catalyst 2.54 Level 3 Ultra-high molecular weight slurry polyethylene catalyst 3.72 Level 4 General Purpose Slurry Polyethylene Catalyst 5.26 Level 5 General Purpose Slurry Polyethylene Catalyst 5.65 The experiments were conducted separately, with the entire process being closed and nitrogen gas continuously introduced at a flow rate of 220 min / min. Add 25 mL of the prepared acid solution (HCl concentration of 4 mol / L and H2SO4 concentration of 0.05 mol / L) to the container, add 80 mg of catalyst and 200 mg of aluminum foil, place in a 50℃ water bath and stir at 1000 rpm for 7 min; Add 35 mL of deionized water to ensure that the electrode test area is submerged in the sample solution. Titration was performed using a 0.02 mol / L ferric ammonium sulfate solution at a titration rate of 0.02 mL / s and a titration interval of 3 s. According to GB6379, six parallel experiments were conducted, and the experimental results are shown in Table 1. Table 1. Results of repeatability experiments on titanium content experimental group Level 1 Level 2 Level 3 Level 4 Level 5 1 2.909 2.588 3.712 5.251 5.832 2 2.830 2.572 3.652 5.413 5.693 3 2.843 2.543 3.693 5.376 5.742 4 2.873 2.512 3.726 5.382 5.709 5 2.895 2.589 3.679 5.402 5.841 6 2.884 2.588 3.701 5.315 5.872 mean 2.87 2.57 3.69 5.36 5.78 Standard deviation 0.03 0.03 0.03 0.06 0.07 As shown in Table 1, when this method is used to test polypropylene catalysts (levels 1 and 2) and ultra-high molecular weight slurry polyethylene catalysts (level 3), the titanium content level is 2.5%–3.8%, and the repeatability limit r = 2.8Sr = 2.8 × (0.03 + 0.03 + 0.03) / 3 = 0.08, indicating that the method has good precision. When used to test general-purpose slurry polyethylene catalysts (levels 4 and 5), the titanium content level is 5.0%–6.0%, and the repeatability limit r = 2.8Sr = 2.8 × (0.06 + 0.07) / 2 = 0.18, indicating that the method has good precision.

[0044] Example 2 Accuracy verification The test results of the catalysts of multiple different batches using the method of the present invention were compared with the spectrophotometric test results of titanium content. The results are shown in Table 2 according to the method of Example 1. Table 2 Comparison of titanium content measured by different analytical methods

[0045] As can be seen from the data in Table 2, the test results of the method of the present invention are basically consistent with those of the spectrophotometric method, and the test accuracy is good.

[0046] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for detecting the titanium content in a titanium-containing reagent, characterized in that, The method includes the following steps: (1) Under an inert gas protective environment, the titanium-containing reagent was acid-hydrolyzed and reduced to obtain a trivalent titanium ion test sample solution; (2) Under an inert gas protective environment, ferric ammonium sulfate solution is added dropwise to the sample solution to be tested, and the potential is tested by an oxidation-reduction electrode during the dropwise process. The titration endpoint is determined according to the potential threshold of the oxidation-reduction electrode, and the titanium content is calculated according to the amount of ferric ammonium sulfate solution added at the titration endpoint.

2. The method according to claim 1, wherein, Titanium-containing reagents are selected from one or more of polyolefin catalysts, metallurgical materials, and aerospace materials; and / or This method is carried out in a container equipped with a redox electrode, and the electrode testing area is controlled to not come into contact with the solution during the acidolysis and reduction process; After acid hydrolysis and reduction, deionized water is added to the container so that the electrode test area is immersed in the sample solution for redox electrode testing.

3. The method according to claim 1 or 2, wherein, In step (1), the acid hydrolysis and reduction steps include: In an inert gas protected environment, titanium-containing reagents are mixed with reducing agents and subjected to acidolysis reduction in an acidic solution containing HCl and / or H2SO4.

4. The method according to claim 3, wherein, The reducing agent includes one or more of aluminum foil and sulfides, preferably aluminum foil.

5. The method according to claim 3, wherein, In the acid solution: the concentration of HCl is 1~5 mol / L, preferably 2~4 mol / L; the concentration of H2SO4 is 0.02~0.07 mol / L, preferably 0.03~0.05 mol / L.

6. The method according to any one of claims 1-5, wherein, In step (1), the conditions for acid hydrolysis reduction include: The acid hydrolysis reduction time is 1-10 minutes, preferably 5-8 minutes; and / or The acidolysis reduction temperature is 45~65℃; and / or The acidolysis-reduction process employs water bath heating; and / or Acid hydrolysis and reduction are carried out under dynamic conditions with a stirring speed of 500-1000 rpm.

7. The method according to any one of claims 1-6, wherein, In step (2), Fe in ferric ammonium sulfate solution 3+ The concentration is 0.01~0.1mol / L, preferably 0.01~0.02mol / L; and / or The dropping rate of ferric ammonium sulfate solution is 0.01~0.04 mL / s, and the dropping time interval is 3~8 s; and / or The redox electrode is a foil ring composite electrode.

8. The method according to any one of claims 1-7, wherein, In steps (1) and (2), The inert gases each comprise nitrogen and / or carbon dioxide; and / or The flow rates of the inert gases introduced are 180~240 mL / min.

9. A method for detecting the titanium content in a polyolefin catalyst, characterized in that, The method described in any one of claims 1-8, wherein the titanium-containing reagent is a polyolefin catalyst, comprises the following steps: i) Under an inert gas protective environment, the polyolefin catalyst was acid-hydrolyzed and reduced to obtain the trivalent titanium ion test sample solution; ii) Under an inert gas protective environment, ferric ammonium sulfate solution is added dropwise to the sample solution to be tested, and the potential is tested using an oxidation-reduction electrode during the dropwise process. The titration endpoint is determined according to the oxidation-reduction electrode potential threshold, and the titanium content is calculated based on the amount of ferric ammonium sulfate solution added at the titration endpoint.

10. The detection method according to claim 9, wherein, The polyolefin catalyst is selected from one or more of polyethylene catalysts, polypropylene catalysts, and polybutene catalysts, preferably polyethylene catalysts and / or polypropylene catalysts. and / or The polyolefin catalyst comprises titanium, magnesium, chlorine, phthalate, hexane, ethoxylate, and furan, wherein the titanium content is 1.5~10 wt%.

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