Method and device for rapid determination of titanium dioxide in rare earth scr denitration catalyst

Abstract

The application discloses a kind of rare earth SCR denitration catalyst titanium dioxide rapid determination method and device, method includes through matrix reconstruction optimization digestion liquid matrix coordination form, eliminate the interference of titanium coordination structure by fluorine ion;Through aliquot preparation background fraction and pre-column standard fraction construction whole-process correction system, can quantitatively compensate the loss of titanium component in multiple processes;Utilize the flow color monitoring of separation column main flow path and monitoring branch split, linkage electric control valve dynamic interception titanium fraction, avoid the recovery rate fluctuation problem caused by column retention drift, sample plug broadening caused by fixed time length collection mode.The application calculates whole-process recovery rate by double test solution titration difference and corrects detection result, solves the defects that traditional equipment is simply spliced, without matrix collaborative adaptation logic, system error is difficult to eliminate, utilizes multiple processes collaborative coupling, realizes titanium dioxide full-automatic accurate detection, effectively improves the stability and quantitative accuracy of industrial large batch sample detection.

Description

Technical Field

[0001] This invention belongs to the field of catalyst detection and analysis technology, specifically relating to a rapid determination method and apparatus for titanium dioxide in rare earth SCR denitration catalysts. Background Technology

[0002] Rare-earth-based SCR denitration catalysts use titanium dioxide as a carrier, and the titanium dioxide content is a key quality control indicator for catalyst production acceptance, operational performance evaluation, and resource utilization of spent catalysts. Current mainstream detection methods employ wet titration, but the coexisting molybdenum and tungsten components in the sample digestion solution can easily interfere with titanium element determination. Fluorine and chlorine components introduced during digestion can also cause titration endpoint drift. Conventional automated detection schemes simply connect digestion, ion exchange, reduction, and titration modules in series, which has several drawbacks: poor compatibility between the digestion medium and the subsequent analytical system; reliance on a fixed-duration strategy for collecting titanium fractions, resulting in insufficient stability of titanium component recovery due to chromatographic retention drift and sample plugging broadening effects; lack of online calibration methods, making it difficult to compensate for titanium losses throughout the digestion, separation, and reduction processes; numerous manual intervention steps, long detection cycles, and inability to effectively eliminate systemic errors; and the lack of adaptive control logic for the complex matrix of rare-earth SCR catalysts, limiting detection accuracy and failing to meet the engineering requirements for rapid and accurate detection of large batches of samples. Summary of the Invention

[0003] The purpose of this invention is to provide a rapid determination method and apparatus for titanium dioxide in rare earth SCR denitration catalysts, in order to solve the technical defects of existing detection technologies that are easily affected by molybdenum and tungsten impurities and fluorine and chlorine components, rely on collecting titanium fractions for a fixed time, resulting in fluctuations in recovery rate, and lack effective means to compensate for titanium loss in the digestion, separation, and reduction processes.

[0004] To achieve the above objectives, this application provides the following technical solution: The first aspect of this application provides a rapid method for determining titanium dioxide in rare earth SCR denitration catalysts, comprising: The digestion solution of the rare earth SCR denitration catalyst sample to be tested was subjected to matrix reconstruction to obtain the reconstruction mother liquor; The reconstructed mother liquor was divided into equal portions, and a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution were prepared. The two equal portions of the test solution were then sent to the same fluoride-resistant anion exchange separation unit for impurity separation treatment. The fluoride-resistant anion exchange separation unit has a main flow path and a monitoring branch at the outlet of the separation column. After either of the sampled liquids passes through the separation column to remove molybdenum and tungsten impurities, a test solution is obtained. The test solution is then diverted into the monitoring branch, where the titanium component in the test solution reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal of the characteristic peak of the titanium component and controls the main flow path electronic valve to intercept and collect the titanium fraction. The colorimetric solution used in the monitoring branch does not flow back into the main flow path. The collected titanium fraction is subjected to sulfuric acid medium conversion to remove fluoride and chloride ions before being transported to a closed oxygen-free reduction unit to reduce the tetravalent titanium in the fraction to trivalent titanium. The background fraction and the spiked fraction were titrated separately using an automatic potentiometric titration unit. The overall recovery rate was calculated based on the difference in titration volume between the two sets of test solutions. The mass fraction of titanium dioxide in the sample was then calculated using the recovery rate correction.

[0005] Furthermore, the fluoride-resistant anion exchange separation unit has a main flow path and a monitoring branch at the outlet of the separation column. After either of the sampled liquids passes through the separation column to remove molybdenum and tungsten impurities, a test solution is obtained. The test solution is then diverted into the monitoring branch, where the titanium component reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal of this characteristic peak and controls the main flow path's electronically controlled valve to collect the titanium fraction. The colorimetric solution used in the monitoring branch does not flow back into the main flow path. Specifically, this includes: After the molybdenum and tungsten impurities are removed by the separation column, the test solution is transported to the flow distributor. The flow distributor is used to split a small volume branch and introduce it into the monitoring branch. The colorimetric liquid metering pump upstream of the monitoring branch is started to quantitatively deliver the colorimetric liquid into the branch. The colorimetric liquid and the branch test solution are fully mixed in the downstream series mixing coil and a colorimetric reaction occurs, thereby generating the characteristic peak of titanium component that can be optically identified. An optical detector connected in series with the hybrid coil is used to collect the titanium peak signal corresponding to the characteristic peak of the titanium component in real time, and the collected titanium peak signal is transmitted to the controller. After receiving the titanium peak signal, the controller switches the on / off state of the main flow electronic control valve connected to it according to the preset signal threshold, so as to completely intercept and collect the titanium-containing fraction in the main flow distributed by the flow distributor. The waste liquid after the color development reaction in the monitoring branch is discharged separately, so that the monitoring branch pipeline is isolated from the main pipeline, thereby preventing the color development liquid in the monitoring branch from flowing back into the main pipeline.

[0006] Further, the collected titanium fraction is introduced into a fluorine-resistant sealed heating container and sulfuric acid is added for mixing. The mixed liquid is heated to remove volatile fluorine and chlorine components from the liquid, completing the sulfuric acid medium conversion. The volatile waste gas is introduced into the tail gas absorption unit for treatment. The titanium solution after sulfuric acid medium conversion treatment is transported to the closed oxygen-free reduction unit through the bottom pipeline of the heating container. The inert gas supply component is started to continuously introduce inert gas to create an oxygen-free environment inside the reduction box. The function of allowing the titanium solution to flow through the replaceable zinc granule reduction box is to fully reduce the tetravalent titanium in the solution to trivalent titanium under sulfuric acid medium conditions. The reduced test solution flows into a gas-liquid separator to remove the hydrogen gas produced in the reaction. After degassing, the test solution is directly transported to the automatic potentiometric titration unit through the liquid outlet pipeline of the gas-liquid separator.

[0007] Further, the reconstructed mother liquor is divided into equal portions to prepare a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution. The two fractions are then sequentially and individually sent to the same fluoride-resistant anion exchange separation unit for impurity separation treatment, specifically including: Two equal volumes of the reconstruction mother liquor were quantitatively transferred, one of which was used as the background fraction without added titanium standard material; A titanium standard solution was quantitatively added to another equal volume of the reconstructed mother liquor to prepare a pre-column spiked aliquot. The background extract is transported to a fluoride-resistant anion exchange separation unit for impurity separation. After the background fraction is separated and cleaned, the spiked fraction is sent to the same fluoride-resistant anion exchange separation unit for impurity separation.

[0008] Furthermore, the process of reconstructing the matrix of the digestion solution of the rare earth SCR denitration catalyst sample to obtain the reconstruction mother liquor specifically includes: Boric acid solution was added to the digestion solution of the catalyst sample to be tested to carry out a complexation reaction, and the free fluorine component present in the complexation digestion solution was analyzed. After complexation, the digestion solution was transferred and subjected to sulfuric acid removal treatment under heating conditions to remove excess hydrofluoric acid from the digestion solution; Hydrochloric acid-hydrofluoric acid mixed reagent was added to the digestion solution after acid removal for resolution treatment, and the solution was diluted to a fixed volume and mixed evenly to obtain the reconstituted mother liquor.

[0009] Further, the automatic potentiometric titration unit is used to titrate the background fraction and the spiked fraction, respectively. The overall recovery rate is calculated based on the difference in titration volume between the two sets of test solutions. The recovery rate correction is used to calculate the mass fraction of titanium dioxide in the sample to be tested. Specifically, this includes: The treated background fraction was sent to the automatic potentiometric titration unit for titration to obtain the titration volume data of the background sample. The processed spiked aliquot is sent to the automatic potentiometric titration unit for titration to obtain the titration volume data of the spiked sample. The overall recovery rate of titanium components was calculated based on the difference in titration volume between the two sets of test solutions. The obtained full-process recovery rate was used to perform correction calculations on the background test solution titration results, and the titanium dioxide mass fraction of the rare earth SCR denitration catalyst sample to be tested was obtained.

[0010] A second aspect of this application provides a rapid determination system for titanium dioxide in rare earth SCR denitration catalysts, comprising: The matrix reconstruction module is used to reconstruct the matrix of the digestion solution of the rare earth SCR denitration catalyst sample to be tested, and obtain the reconstruction mother liquor. The test solution preparation module is used to take equal portions of the reconstructed mother liquor and prepare a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution, and then send the two equal portions of test solution into the same fluoride-resistant anion exchange separation unit for impurity separation treatment. The fluoride-resistant anion exchange separation module is used to sequentially receive the background fraction and the spiked fraction, remove molybdenum and tungsten impurities from the test solution, and obtain the purified test solution. The online monitoring and fraction interception module is used to perform split colorimetric detection on the purified test solution. The titanium component in the test solution reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal of the characteristic peak of the titanium component and controls the main flow electronic control valve to intercept and collect the titanium fraction. The colorimetric solution used in the monitoring branch does not flow back into the main flow. The sulfuric acid medium conversion and impurity removal module is used to convert the collected titanium fraction to sulfuric acid medium to remove fluoride ions and chloride ions before transporting it to a closed oxygen-free reduction unit. The closed-loop anaerobic reduction module is used to quantitatively reduce tetravalent titanium to trivalent titanium in the purified titanium solution under a closed anaerobic environment, and to complete gas-liquid separation and impurity removal. An automatic potentiometric titration detection module is used to titrate the background fraction and the spiked fraction, respectively. The recovery rate of the whole process is calculated based on the difference in titration volume between the two sets of test solutions. The mass fraction of titanium dioxide in the sample to be tested is obtained by correcting the recovery rate.

[0011] A third aspect of this application provides an electronic device, comprising: Memory, used to store computer programs; A processor is used to execute the computer program to implement the steps of the rapid determination method for rare earth SCR denitration catalyst titanium dioxide as described above.

[0012] In a fourth aspect, this application provides a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the rapid determination method for rare earth SCR denitration catalyst titanium dioxide as described above.

[0013] In a fifth aspect, this application provides a computer program product, comprising a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of the rapid determination method for titanium dioxide in rare earth SCR denitration catalysts as described above.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. By optimizing the matrix coordination morphology of the digestion solution through matrix reconstruction, the problems of medium instability and fluoride ion interference with titanium coordination structure in rare earth catalyst digestion systems are solved. A full-process control and calibration system is constructed by preparing equal portions of the background fraction and the pre-column spiked fraction, addressing the inability of traditional detection methods to quantitatively compensate for titanium component losses in multiple processes. The dynamic retention of titanium fractions by a linkage electronically controlled valve in the primary and secondary flow paths of the separation column is achieved, resolving the recovery rate fluctuations caused by column retention drift and sample plug widening in fixed-duration collection modes. Furthermore, a thorough sulfuric acid medium conversion process is employed. The system effectively removes fluorine and chlorine impurities from the system, solving the problem of titration endpoint drift caused by residual impurities; it utilizes a closed, oxygen-free reducing environment to ensure quantitative reduction of tetravalent titanium, solving the problem of easy oxidation and distortion of trivalent titanium; it combines the titration difference of two test solutions to calculate the overall recovery rate and correct the results, overcoming the shortcomings of conventional equipment such as simple splicing, lack of matrix-compatible logic, and inability to eliminate system errors; through deep coupling and collaborative operation of multiple processes, it achieves fully automated and accurate detection of titanium dioxide in rare earth SCR denitration catalysts, significantly improving the stability and quantitative accuracy of industrial batch sample detection.

[0015] 2. By using a flow distributor to sample a small amount of the separated sample solution via a micro-branch, the problem of not being able to capture the titanium peak range in real time during full-volume sample detection is solved. A metering pump quantitatively delivers the chromogenic solution, ensuring it reacts fully within the mixing coil, addressing the issues of uneven titanium colorimetric reaction and weak characteristic signals. An optical detector collects the characteristic peak signals of the titanium components in real time and feeds them back to the controller, resolving the problem of column retention drift that cannot be adapted to traditional fixed-sequence methods. The controller dynamically switches the on / off state of the main flow electronic valve to precisely intercept the titanium fraction, solving the problem of incomplete titanium fraction collection and fluctuations in recovery rate caused by sample plug widening. Independent discharge of waste liquid from monitoring branches and complete isolation of the flow path solve the problem of chromogenic solution reflux contaminating the main flow sample solution and causing detection interference. This achieves accurate, interference-free, and full-coverage collection of titanium fractions, effectively improving the stability and repeatability of titanium component recovery after impurity separation.

[0016] 3. By using a fluorine-resistant, sealed heating container to convert the titanium fraction to a sulfuric acid medium, the problem of incompatibility between the original fluorine- and chlorine-containing digestion media and the reduction titration system is solved. Volatile fluorine and chlorine components in the system are removed by heating and a tail gas absorption unit is added to solve the problems of residual impurities causing titration endpoint drift and severe matrix interference. A sealed, oxygen-free environment is created by continuous purging with an inert gas supply assembly to solve the problem of oxygen in the system causing re-oxidation of the trivalent titanium generated during reduction and resulting in lower values. A replaceable zinc granule reduction box stabilizes the sulfuric acid medium reduction conditions, solving the problems of reduced module activity decay and unstable reduction efficiency. A gas-liquid separator removes hydrogen produced in the reaction, solving the problem of bubble interference in the titration process. The entire titanium reduction reaction process is stabilized, ensuring complete reduction of tetravalent titanium and significantly improving the reliability and detection accuracy of the reduction process.

[0017] 4. By quantitatively transferring equal volumes of reconstructed mother liquor to prepare background and spiked fractions, the problem of single-solution detection being unable to identify component losses throughout the entire process is solved. A spiked control system is constructed by quantitatively adding titanium standard solution before the column, addressing the lack of a full-process calibration benchmark and the inability to quantify systematic errors in traditional detection methods. A progressive detection process, starting with background analysis followed by spiked analysis and then combined with pipeline cleaning, solves the problem of cross-residual interference between different solutions. Standardized processing of two sets of solutions using the same fluoride-resistant anion exchange separation unit resolves the issue of inconsistent experimental conditions leading to calibration data failure. A stable and reliable basis for calculating the full-process recovery rate is established, effectively compensating for titanium component losses in each digestion, separation, and reduction step, significantly improving the accuracy of detection result calibration.

[0018] 5. By immobilizing free fluoride through a complexation reaction with boric acid solution in the digestion solution, the problems of free fluoride in the digestion solution interfering with the coordination morphology of titanium and corroding the flow path electrodes are solved. Excess hydrofluoric acid is removed by sulfuric acid heating treatment, solving the problems of unstable media and severe interference in subsequent reactions in high-fluoride systems. The matrix is ​​reconstituted by rehydration and volume adjustment with a hydrochloric acid-hydrofluoric acid mixed reagent, solving the problems of titanium component analysis and poor system homogeneity after acid removal. The physicochemical state of the digestion solution is optimized by a step-by-step matrix modification process, solving the problems of poor compatibility between traditional digestion systems and separation, reduction, and titration modules, and the lack of synergistic logic in simple splicing. A reconstructed mother liquor with uniform composition, stable properties, and compatibility with subsequent full-process detection is obtained, reducing matrix interference from the source and providing a reliable sample basis for accurate detection.

[0019] 6. By performing automatic potentiometric titration on the background test solution and the spiked test solution separately and collecting titration volume data, the problem of matrix interference and component loss error cannot be distinguished by a single test; the recovery rate of titanium components throughout the entire process is calculated by the difference between the two sets of titration volumes, which solves the problem that traditional methods only correct the endpoint and cannot compensate for titanium loss throughout the pretreatment process; the background test results are corrected by the recovery rate, which solves the problem that the cumulative systematic error of multiple processes cannot be eliminated and the detection accuracy decays over a long period of time. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This invention provides a schematic flowchart of a rapid determination method for titanium dioxide in rare earth SCR denitration catalysts. Figure 2 A block diagram of a rapid determination system for titanium dioxide in rare earth SCR denitration catalysts provided by the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] To address the technical deficiencies mentioned in the background section, this embodiment provides a method and apparatus for the rapid determination of titanium dioxide in rare earth SCR denitrification catalysts.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1 As shown, in a first aspect of the present invention, a method for rapid determination of titanium dioxide in rare earth SCR denitration catalysts is provided, comprising: S101. The digestion solution of the rare earth SCR denitration catalyst sample to be tested is reconstructed to obtain the reconstruction mother liquor. For example, a boric acid complexation reaction vessel, a sulfuric acid removal heating vessel, and a hydrochloric acid-hydrofluoric acid reconstitution and volume-determination vessel are pre-configured in series. The fluids are transported between the vessels using PFA fluorine-resistant pipelines to prevent fluorine media from corroding the pipelines and introducing impurities to contaminate the test solution.

[0027] Before carrying out matrix reconstruction, the catalyst sample pretreatment and microwave digestion were completed. The surface dust of the rare earth SCR denitration catalyst to be tested was removed, crushed and ground and passed through a 0.074 mm sieve. The powder under sieve was dried at 105-110℃ to constant weight and transferred to a desiccator for cooling. 0.1000-0.3000 g of sample was accurately weighed. When the estimated TiO2 content was less than 50%, the sample amount was adjusted to a maximum of 0.5000 g. The digestion effect and the carrying capacity of the separation column were verified.

[0028] After weighing, the sample is placed into a fluorine-resistant microwave digestion vessel, and 6–10 mL of hydrochloric acid, 1–3 mL of nitric acid, and 0.5–1.5 mL of hydrofluoric acid are added. The digestion vessel is sealed, and the temperature is raised to 185–210℃ in 8–15 min and held for 15–30 min. After digestion and cooling, the system inside the vessel is checked. If there is solid residue, an additional digestion process is required to confirm that the titanium element has been completely dissolved.

[0029] The cooled digestion solution was introduced into a boric acid complexation reaction vessel, and boric acid solution was added to complex the free fluorine component in the system. After complexation, the solution was transferred to a sulfuric acid removal heating vessel, and the temperature was raised to remove excess hydrofluoric acid. The solution after removal was transferred to a hydrochloric acid-hydrofluoric acid reconstitution and volume-adjusting vessel, and a hydrochloric acid-hydrofluoric acid mixed reagent was added for reconstitution, volume adjustment and mixing to finally prepare the reconstituted mother liquor.

[0030] The preferred method for fluorine complexation is to use a boric acid solution with a mass concentration of 4% to 8%, and the complexation solution is a system of hydrochloric acid with a volume fraction of 10% to 30% combined with hydrofluoric acid of 3% to 10%.

[0031] S102. Take equal portions of the reconstructed mother liquor and prepare a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution, and send the two equal portions of the test solution into the same fluoride-resistant anion exchange separation unit for impurity separation treatment. For example, a standard spiking unit is provided, which consists of a titanium standard storage bottle, a metering pump, and a mixing chamber connected in series. The outlet pipeline of the mixing chamber is connected to the sample inlet of the fluoride-resistant anion exchange separation unit. Two equal volumes of the reconstructed mother solution are quantitatively transferred. The first portion is used directly as the background fraction without adding any titanium standard material. Ti(IV) standard solution is quantitatively added to the second portion of the reconstructed mother solution using the standard spiking unit to prepare the spiking fraction. The spiking amount is preferably controlled to increase the final titration volume by 20% to 50% compared to the sample background titration volume.

[0032] First, the background fraction is fed into the fluoride-resistant anion exchange separation unit for purification and separation. After the background fraction has completed the separation process, a pipeline cleaning procedure is initiated to eliminate any residual test solution in the pipeline. After cleaning, the spiked fraction is then fed in for a completely identical separation operation. The fluoride-resistant anion exchange separation unit uses a PFA / PTFE / PEEK column, filled with a quaternary ammonium-type strong basic anion exchange resin. It utilizes the differences in the retention behavior of titanium, molybdenum, and tungsten fluorine complexes to achieve the separation of titanium components from molybdenum and tungsten impurities.

[0033] S103, the separation column outlet of the fluoride-resistant anion exchange separation unit is configured with a main flow path and a monitoring branch. After the separated liquid flows through the separation column to remove molybdenum and tungsten impurities, a test solution is obtained. The test solution is diverted into the monitoring branch, where the titanium component in the test solution reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal and controls the main flow path electronic control valve to intercept and collect the titanium fraction. The colorimetric solution in the monitoring branch does not flow back into the main flow path. For example, the separation column of the fluoride-resistant anion exchange separation unit is connected to the sample inlet and the flow distributor at both ends through fluoride-resistant tubing, respectively. The flow distributor splits into two channels, one of which is connected to the main flow solenoid valve, and the other is a monitoring branch. The monitoring branch is equipped with a colorimetric liquid metering pump, a mixing coil, and an optical detector in sequence along the fluid flow direction. The signal output terminal of the optical detector is electrically connected to the controller, and the output control terminal of the controller is connected to the main flow solenoid valve to form a closed-loop signal linkage control system.

[0034] After molybdenum and tungsten impurities are removed by the separation column, the test solution is delivered to a flow distributor. The flow distributor divides the fluid into two streams: 90%–99% of the fluid enters the main stream, and 1%–10% of the fluid is directed into the monitoring branch. A metering pump delivers hydrogen peroxide colorimetric solution quantitatively. The test solution and the colorimetric solution in the branch are thoroughly mixed and reacted in a mixing coil to generate a titanium peroxide colorimetric complex with characteristic absorption. An optical detector continuously acquires optical signals in the 390–430 nm wavelength band to identify the characteristic elution peaks of the titanium component. The controller compares the acquired signal with a preset threshold in real time. When the signal exceeds the opening threshold, the main stream electronic control valve is switched, directing the main stream fluid into the fraction collection container. After the titanium signal falls back to the closing threshold and remains for a set time, the controller shuts off the collection process. The waste liquid after the reaction in the monitoring branch is discharged independently, and the flow paths are isolated to completely prevent the colorimetric solution from flowing back into the main stream and interfering with subsequent reduction and titration processes.

[0035] S104. The collected titanium fraction is converted to sulfuric acid medium to remove fluoride ions and chloride ions, and then transported to a closed oxygen-free reduction unit to reduce the tetravalent titanium in the fraction to trivalent titanium. For example, a sulfuric acid medium conversion device and a closed oxygen-free reduction unit are configured; the sulfuric acid medium conversion device includes a fluorine-resistant closed heating container, the top pipeline of the heating container is connected to the tail gas absorption unit, and the bottom liquid outlet pipeline is connected to the closed oxygen-free reduction unit; the closed oxygen-free reduction unit is sequentially equipped with an inert gas supply component, a replaceable zinc granule reduction box, and a gas-liquid separator, and the liquid outlet pipeline of the gas-liquid separator is directly connected to the automatic potentiometric titration unit.

[0036] The collected titanium fraction is transferred to a fluorine-resistant, sealed heating container, mixed with sulfuric acid, and heated to remove volatile fluorine and chlorine components, completing the medium conversion. Fluorine- and chlorine-containing waste gases are introduced into a tail gas absorption unit for harmless treatment. The titanium solution after medium conversion is transported to a sealed, oxygen-free reduction unit. An inert gas supply component continuously introduces nitrogen or argon to maintain an oxygen-free atmosphere inside the reduction chamber. The titanium solution flows through a replaceable zinc particle reduction chamber, quantitatively reducing Ti(IV) to Ti(III) under sulfuric acid medium conditions. The reduced solution flows into a gas-liquid separator to remove hydrogen generated from the reaction of zinc and sulfuric acid. The degassed solution is then transported via a sealed pipeline to an automatic potentiometric titration unit, minimizing pipeline length and reducing the contact between Ti(III) and air. The preferred zinc particle size is 0.3–1.5 mm, the reduction environment temperature is maintained at 20–35°C, and the sulfuric acid concentration is controlled at 0.5–1.5 mol / L.

[0037] S105. The background fraction and the spiked fraction are titrated separately using an automatic potentiometric titration unit. The overall recovery rate is calculated based on the difference in titration volume between the two sets of test solutions. The mass fraction of titanium dioxide in the sample to be tested is obtained by correcting the recovery rate.

[0038] For example, the automatic potentiometric titration unit is equipped with a closed titration cell, which is connected to the liquid outlet pipeline of the gas-liquid separator, the inert gas purging pipeline, and the ferric ammonium sulfate standard burette. The titration cell is equipped with a dual salt bridge reference electrode and a platinum indicator electrode, and the electrode signal lines are connected to the controller.

[0039] Ti(III) reacts with Fe(III) in a 1:1 molar ratio: Ti³ + +Fe³ + →Ti 4+ +Fe² + The treated background fraction was introduced into a closed titration cell, and the air in the cell was continuously purged with inert gas. The titration program was started, and the titration volume of the background sample was recorded as V_A. After the titration was completed, the titration cell was thoroughly cleaned. Then, the sample corresponding to the spiked fraction was introduced, and the same titration procedure was performed to obtain the titration volume of the spiked sample as V_B. The blank titration volume of the entire process was measured simultaneously as V_0.

[0040] Based on the formula: R = c × (V_B) The overall recovery rate of titanium components was calculated using V_A) / n_add; the recovery rate was then used to correct the background titration data, based on the formula: w(TiO2)=[c×(V_A) / n_add]. The mass fraction of titanium dioxide in the sample is calculated as [V_0)×M_TiO2×V_total] / [1000×m×V_splitting liquid×R]×100%. A 0.0050–0.0200 mol / L ferric ammonium sulfate standard solution is used for titration. The titration endpoint is determined by the maximum value of the first derivative of the potential curve, and the endpoint is verified by the second derivative.

[0041] If the overall recovery rate exceeds the preset acceptable range, the system will automatically determine the test results as invalid and remind the operator to check the activity of the separation and collection unit, the reduction unit, and the status of the titration reagent.

[0042] In a second aspect, this invention provides a rapid determination system for titanium dioxide in rare earth SCR denitration catalysts, such as... Figure 2 As shown, it includes: The matrix reconstruction module is used to reconstruct the matrix of the digestion solution of the rare earth SCR denitration catalyst sample to be tested, and obtain the reconstruction mother liquor. The matrix reconstruction module includes a boric acid complexation reaction vessel, a sulfuric acid removal heating vessel, and a hydrochloric acid-hydrofluoric acid reconstitution and volume adjustment vessel. The vessels are connected by PFA fluorine-resistant pipelines.

[0043] The test solution preparation module is used to take equal portions of the reconstructed mother liquor and prepare a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution. The two fractions are then sent to the same fluoride-resistant anion exchange separation unit for impurity separation. The test solution preparation module integrates a standard spiking unit, which includes a titanium standard storage bottle, a metering pump, and a mixing chamber.

[0044] The fluorine-resistant anion exchange separation module is used to sequentially receive the background fraction and the spiked fraction, remove molybdenum and tungsten impurities from the test solution, and obtain the purified test solution; it includes a separation column made of PFA / PTFE / PEEK material, and the column is filled with quaternary ammonium type strong base anion exchange resin.

[0045] The online monitoring and fraction interception module is used for split colorimetric detection of the purified test solution. The titanium component in the test solution reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal of the characteristic peak of the titanium component and controls the main flow solenoid valve to intercept and collect the titanium fraction. The colorimetric solution used in the monitoring branch does not flow back into the main flow. The module includes a flow distributor, a colorimetric solution metering pump, a mixing coil, an optical detector, and a main flow solenoid valve.

[0046] The sulfuric acid medium conversion and impurity removal module is used to convert the collected titanium fraction into sulfuric acid medium, remove fluoride and chloride ions, and then transport it to a closed oxygen-free reduction unit; it consists of a fluorine-resistant closed heating container, a sulfuric acid metering pump, and a tail gas absorption unit.

[0047] The closed-loop anaerobic reduction module is used to quantitatively reduce tetravalent titanium to trivalent titanium in a purified titanium solution under a closed anaerobic environment, and to complete gas-liquid separation and impurity removal; it includes an inert gas supply component, a replaceable zinc granule reduction box, and a gas-liquid separator.

[0048] The automatic potentiometric titration detection module is used to titrate the test solutions corresponding to the background aliquot and the spiked aliquot separately. The recovery rate of the whole process is calculated based on the difference in titration volume between the two test solutions. The mass fraction of titanium dioxide in the test sample is obtained by calculation using recovery rate correction. It is equipped with a closed titration cell, a platinum indicator electrode, a dual salt bridge reference electrode, and an automatic titration mechanism.

[0049] The controller is electrically connected to all electrical control components and executes the entire process logic of fluid delivery, valve switching, signal acquisition, titration control, data processing, and abnormal alarm according to a preset timing sequence.

[0050] System operation sequence: The carrier fluid is flushed through the pipeline to establish a detection baseline; background fraction is introduced, titanium peaks are identified online, and titanium fractions are collected; medium conversion, oxygen-free reduction, and potentiometric titration are completed sequentially, and background titration data are collected; after pipeline cleaning, spiked fraction is introduced, and the entire process is repeated to obtain spiked titration data; the controller automatically calculates the overall recovery rate, and if the recovery rate is qualified, the titanium dioxide content is calculated; the separation column regeneration program is automatically started based on column load and retention time drift.

[0051] In a third aspect of the present invention, an electronic device is provided, including a memory and a processor; the memory is used to store a computer program; the processor is used to execute the computer program stored in the memory and perform method steps S101 to S105.

[0052] Electronic devices can include industrial control computers, embedded controllers, and automated analysis workstations.

[0053] The processor can be a general-purpose central processing unit (CPU), a microprocessor (MCU), or a programmable logic controller (PLC). The memory includes volatile and non-volatile storage media, used to store control timing parameters, signal thresholds, standard solution parameters, calculation formulas, and historical detection data. When the processor runs the computer program, it performs functions such as sample pretreatment timing control, pump flow regulation, electrically controlled valve on / off control, optical signal reading, potential signal acquisition, recovery rate calculation, detection result output, and abnormal status alarms.

[0054] In a fourth aspect of the embodiments of the present invention, a computer-readable storage medium is provided, in which a computer program is stored, and when the computer program is executed by a processor, all steps of the rapid determination method for titanium dioxide in rare earth SCR denitration catalyst are implemented.

[0055] The computer-readable storage medium includes carriers such as a USB flash drive, a solid-state drive, a mechanical hard disk, a flash memory card, and an optical disc; the program code stored inside the storage medium includes the complete set of equipment linkage control logic, titanium peak identification algorithm, endpoint identification algorithm, full-process recovery rate calculation program, result correction algorithm, and data storage and report output program.

[0056] In a fifth aspect of the embodiments of the present invention, a computer program product is provided, which includes a computer program stored in a computer-readable storage medium. When the program is loaded and run by a processor, all the operation steps from S101 to S105 are executed; the computer program product can be transmitted and downloaded through a network, and directly deployed on the industrial control terminal supporting the determination system, so as to realize the automatic operation of the entire analysis process.

[0057] Different operation examples are provided below to illustrate the present solution Example 1 Sample: Weigh 0.3000 g of rare earth SCR denitration catalyst powder that has been dried at 105°C and passed through a 0.074 mm sieve; Microwave digestion: 8.0 mL of hydrochloric acid, 2.0 mL of nitric acid, 1.0 mL of hydrofluoric acid; heat up to 200°C in 10 min, and hold for 20 min; Fluorine complexation treatment: Add 10 mL of boric acid solution with a mass fraction of 4% to the cooled digestion solution, and heat at 140°C in a sealed state for 10 min; Acid driving and conversion: Transfer to a PFA container, add 2.0 mL of sulfuric acid, heat until sulfuric acid fumes are generated and maintain for 5 min; Redissolution and volume fixation: Use the calibrated hydrochloric acid-hydrofluoric acid redissolution solution to dissolve the residue, and fix the volume to 100.0 mL to obtain a reconstituted mother liquor; Test solution aliquot: Pipette 1.00 mL of the reconstituted mother liquor respectively to prepare a background aliquot and a spiked aliquot; Anion separation: The flow rate of the separation column is 0.5 to 1.5 mL / min; On-line monitoring: 5% of the flow enters the monitoring branch, and the titanium chromogenic signal is detected at a wavelength of 410 nm; Medium conversion: Add sulfuric acid to the fraction and heat to remove halides, then cool to prepare a 1.0 mol / L titanium sulfate solution; Reduction conditions: Continuous nitrogen protection, temperature 25±3°C, the test solution flows through the zinc particle reduction box, and is sent to the titration cell after gas-liquid separation; Potentiometric titration: Automatic titration with 0.0050 mol / L ammonium ferric sulfate standard solution, and the endpoint is determined by the potential derivative method.

[0058] Example 2 Sample mass m = 0.3000 g; total volume of reconstructed mother liquor V_total = 100.0 mL; volume of aliquot V_liquot = 1.00 mL; concentration of ferric ammonium sulfate c = 0.005000 mol / L; blank volume V0 = 0.040 mL; background titration volume V_A = 6.194 mL; spiking titration volume V_B = 8.174 mL; amount of added titanium standard n_add = 1.000 × 10⁻⁶ g / mL -5 mol; Recovery rate R = 0.005000 × (8.174) 6.194)×10 - ³÷1.000×10 -5 =0.990; the molar mass of TiO2 is 79.88 g / mol; w(TiO2)=[0.005000×(6.194 [0.040)×79.88×100.0]÷[1000×0.3000×1.00×0.990]×100%=82.76%. This calculation example verifies the matching of the entire set of process parameters. The titration volume is within the optimal working range of the automatic potentiometric titrator, avoiding the problem of mismatch between reagent concentration and sampling volume.

[0059] In terms of system fault diagnosis, for abnormal operating conditions where the titanium peak signal is normal but the overall recovery rate is consistently low, priority should be given to investigating the problem of incomplete fraction collection caused by deviations in the opening and closing sequence of the fraction collection electronic control valve, valve response lag, or premature shut-off. At the same time, check the core causes such as titanium component adsorption residue on the inner wall of the sulfuric acid medium conversion vessel, loss of test solution adhering to the wall, and activity decay and reduced reduction capacity of the replaceable zinc granule reduction box after long-term operation, so as to locate the source of abnormal titanium loss in the entire process.

[0060] To address the persistent shift in the retention time of the titanium component, the main investigation focuses on changes in key parameters such as deviations in the carrier acidity ratio of the separation system, fluctuations in pipeline fluid flow rate, aging and deactivation of the anion exchange resin, and drift in column operating temperature. These factors directly alter the column retention behavior of the titanium-fluorine complex, leading to peak shifts. For persistent titration potential drift and unstable endpoint determination, the effectiveness of the inert gas protection in the closed system, the state and conductivity stability of the salt bridge liquid in the dual-salt-bridge reference electrode, the exposure time of the Ti(III) reduction solution in the pipeline, and the dehydrogenation effect of the gas-liquid separator must be carefully examined to prevent potential baseline fluctuations caused by oxygen intrusion and bubble interference. For abnormal fluctuations in the titration increment and irregular deviations in the spiking response, the stability of the titanium standard stock solution concentration, the metering accuracy of the pre-column quantitative spiking pump, the matching of blank subtraction parameters throughout the process, and the calibration effectiveness of the ferric ammonium sulfate titration reagent must be verified to eliminate errors in the metering and reagent systems.

[0061] Regarding equivalent alternative implementation methods, the present invention has a variety of compliant replacement forms; the reduction unit can replace the conventional replaceable zinc granule reduction box with a flow-through electrochemical reduction unit. After the replacement, the reduction efficiency needs to be verified by using a gradient titanium standard solution. The side reaction of electrode hydrogen evolution and the accumulation of contaminants on the electrode surface are strictly controlled to ensure that the quantitative reduction effect of Ti(IV) is consistent with the original scheme.

[0062] In the titanium peak online monitoring system, the hydrogen peroxide colorimetric detection method can be replaced by other highly selective optical and electrochemical identification methods for titanium. It is only necessary to meet the core requirement of accurately identifying the start and end range of the titanium elution peak, and to ensure that the reaction waste liquid in the monitoring branch is discharged independently and that the branch fluid is strictly prohibited from flowing back into the main channel, so as to prevent interference with the subsequent reduction and titration processes.

[0063] The sulfuric acid medium conversion and impurity removal process can replace closed acid evaporation equipment such as micro-closed evaporators and programmable temperature-controlled PFA reaction cups. The core control logic is to completely remove residual nitric acid and free fluorine components in the system, and to uniformly convert the complex mixed medium into a single sulfuric acid medium, so as to ensure the stability of the subsequent reduction and titration system.

[0064] For industrial testing scenarios requiring stable sample matrices and high batch consistency, an intermittent pre-column spiking calibration mode can be used to improve testing efficiency. Only when the separation column retention time deviates or the reduction unit verification index exceeds a preset control threshold is the single-sample pre-column spiking calibration mechanism reverted, balancing testing accuracy and efficiency. The separation column packing can be replaced with other anion exchange packings with resistance to hydrofluoric acid and hydrochloric acid corrosion. Before replacement, the column retention characteristics and resolution of Ti, Mo, and W components must be verified to ensure effective sequential separation of the three components, meeting the core testing requirements of impurity isolation and accurate fraction collection.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rapid method for determining titanium dioxide in rare earth SCR denitration catalysts, characterized in that, include: The digestion solution of the rare earth SCR denitration catalyst sample to be tested was subjected to matrix reconstruction to obtain the reconstruction mother liquor; The reconstructed mother liquor was divided into equal portions, and a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution were prepared. The two equal portions of the test solution were then sent to the same fluoride-resistant anion exchange separation unit for impurity separation treatment. The fluoride-resistant anion exchange separation unit has a main flow path and a monitoring branch at the outlet of the separation column. After either of the sampled liquids passes through the separation column to remove molybdenum and tungsten impurities, a test solution is obtained. The test solution is then diverted into the monitoring branch, where the titanium component in the test solution reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal of the characteristic peak of the titanium component and controls the main flow path electronic valve to intercept and collect the titanium fraction. The colorimetric solution used in the monitoring branch does not flow back into the main flow path. The collected titanium fraction is subjected to sulfuric acid medium conversion to remove fluoride and chloride ions before being transported to a closed oxygen-free reduction unit to reduce the tetravalent titanium in the fraction to trivalent titanium. The background fraction and the spiked fraction were titrated separately using an automatic potentiometric titration unit. The overall recovery rate was calculated based on the difference in titration volume between the two sets of test solutions. The mass fraction of titanium dioxide in the sample was then calculated using the recovery rate correction.

2. The rapid determination method for titanium dioxide in rare earth SCR denitration catalyst according to claim 1, characterized in that, The fluoride-resistant anion exchange separation unit has a main flow path and a monitoring branch at the outlet of the separation column. After either of the sampled liquids passes through the separation column to remove molybdenum and tungsten impurities, a test solution is obtained. The test solution is then diverted into the monitoring branch, where the titanium component reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal of this characteristic peak and controls the main flow path's electronically controlled valve to collect the titanium fraction. Furthermore, the colorimetric solution used in the monitoring branch does not flow back into the main flow path. Specifically, this includes: After the molybdenum and tungsten impurities are removed by the separation column, the test solution is transported to the flow distributor. The flow distributor is used to split a small volume branch and introduce it into the monitoring branch. The colorimetric liquid metering pump upstream of the monitoring branch is started to quantitatively deliver the colorimetric liquid into the branch. The colorimetric liquid and the branch test solution are fully mixed in the downstream series mixing coil and a colorimetric reaction occurs, thereby generating the characteristic peak of titanium component that can be optically identified. An optical detector connected in series with the hybrid coil is used to collect the titanium peak signal corresponding to the characteristic peak of the titanium component in real time, and the collected titanium peak signal is transmitted to the controller. After receiving the titanium peak signal, the controller switches the on / off state of the main flow electronic control valve connected to it according to the preset signal threshold, so as to completely intercept and collect the titanium-containing fraction in the main flow distributed by the flow distributor. The waste liquid after the color development reaction in the monitoring branch is discharged separately, so that the monitoring branch pipeline is isolated from the main pipeline, thereby preventing the color development liquid in the monitoring branch from flowing back into the main pipeline.

3. The rapid determination method for titanium dioxide in rare earth SCR denitration catalysts according to claim 1, characterized in that, The collected titanium fraction is introduced into a fluorine-resistant sealed heating container and sulfuric acid is added for mixing. The mixed liquid is heated to remove volatile fluorine and chlorine components from the liquid, thus completing the sulfuric acid medium conversion. The volatile waste gas is introduced into the tail gas absorption unit for treatment. The titanium solution after sulfuric acid medium conversion treatment is transported to the closed oxygen-free reduction unit through the bottom pipeline of the heating container. The inert gas supply component is started to continuously introduce inert gas to create an oxygen-free environment inside the reduction box. The function of allowing the titanium solution to flow through the replaceable zinc granule reduction box is to fully reduce the tetravalent titanium in the solution to trivalent titanium under sulfuric acid medium conditions. The reduced test solution flows into a gas-liquid separator to remove the hydrogen gas produced in the reaction. After degassing, the test solution is directly transported to the automatic potentiometric titration unit through the liquid outlet pipeline of the gas-liquid separator.

4. The rapid determination method for titanium dioxide in rare earth SCR denitration catalyst according to claim 1, characterized in that, The reconstructed mother liquor was divided into equal portions to prepare a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution. The two fractions were then sequentially and separately sent to the same fluoride-resistant anion exchange separation unit for impurity separation treatment, specifically including: Two equal volumes of the reconstruction mother liquor were quantitatively transferred, one of which was used as the background fraction without added titanium standard material; A titanium standard solution was quantitatively added to another equal volume of the reconstructed mother liquor to prepare a pre-column spiked aliquot. The background extract is transported to a fluoride-resistant anion exchange separation unit for impurity separation. After the background fraction is separated and cleaned, the spiked fraction is sent to the same fluoride-resistant anion exchange separation unit for impurity separation.

5. The rapid determination method for titanium dioxide in rare earth SCR denitration catalyst according to claim 1, characterized in that, The process of reconstructing the matrix of the digestion solution of the rare earth SCR denitration catalyst sample to obtain the reconstruction mother liquor specifically includes: Boric acid solution was added to the digestion solution of the catalyst sample to be tested to carry out a complexation reaction, and the free fluorine component present in the complexation digestion solution was analyzed. After complexation, the digestion solution was transferred and subjected to sulfuric acid removal treatment under heating conditions to remove excess hydrofluoric acid from the digestion solution; Hydrochloric acid-hydrofluoric acid mixed reagent was added to the digestion solution after acid removal for resolution treatment, and the solution was diluted to a fixed volume and mixed evenly to obtain the reconstituted mother liquor.

6. The rapid determination method for titanium dioxide in rare earth SCR denitration catalyst according to claim 1, characterized in that, The process involves using an automatic potentiometric titration unit to titrate the background fraction and the spiked fraction, respectively. The overall recovery rate is calculated based on the volume difference between the two sets of solutions. The recovery rate is then used to correct for and calculate the mass fraction of titanium dioxide in the sample. Specifically, this includes: The treated background fraction was sent to the automatic potentiometric titration unit for titration to obtain the titration volume data of the background sample. The processed spiked aliquot is sent to the automatic potentiometric titration unit for titration to obtain the titration volume data of the spiked sample. The overall recovery rate of titanium components was calculated based on the difference in titration volume between the two sets of test solutions. The obtained full-process recovery rate was used to perform correction calculations on the background test solution titration results, and the titanium dioxide mass fraction of the rare earth SCR denitration catalyst sample to be tested was obtained.

7. A rapid determination system for titanium dioxide in rare earth SCR denitration catalysts, characterized in that, include: The matrix reconstruction module is used to reconstruct the matrix of the digestion solution of the rare earth SCR denitration catalyst sample to be tested, and obtain the reconstruction mother liquor. The test solution preparation module is used to take equal portions of the reconstructed mother liquor and prepare a background fraction without added titanium standard material and a spiked fraction with pre-column quantitative addition of titanium standard solution, and then send the two equal portions of test solution into the same fluoride-resistant anion exchange separation unit for impurity separation treatment. The fluoride-resistant anion exchange separation module is used to sequentially receive the background fraction and the spiked fraction, remove molybdenum and tungsten impurities from the test solution, and obtain the purified test solution. The online monitoring and fraction interception module is used to perform split colorimetric detection on the purified test solution. The titanium component in the test solution reacts with the colorimetric solution to generate a characteristic peak of the titanium component. The controller detects the titanium peak signal of the characteristic peak of the titanium component and controls the main flow electronic control valve to intercept and collect the titanium fraction. The colorimetric solution used in the monitoring branch does not flow back into the main flow. The sulfuric acid medium conversion and impurity removal module is used to convert the collected titanium fraction to sulfuric acid medium to remove fluoride ions and chloride ions before transporting it to a closed oxygen-free reduction unit. The closed-loop anaerobic reduction module is used to quantitatively reduce tetravalent titanium to trivalent titanium in the purified titanium solution under a closed anaerobic environment, and to complete gas-liquid separation and impurity removal. An automatic potentiometric titration detection module is used to titrate the background fraction and the spiked fraction, respectively. The recovery rate of the whole process is calculated based on the difference in titration volume between the two sets of test solutions. The mass fraction of titanium dioxide in the sample to be tested is obtained by correcting the recovery rate.

8. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the rapid determination method for rare earth SCR denitration catalyst titanium dioxide as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein when the computer program is executed by a processor, it implements the steps of the rapid determination method for titanium dioxide in rare earth SCR denitration catalysts as described in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the rapid determination method for titanium dioxide in rare earth SCR denitration catalysts as described in any one of claims 1 to 6.

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