Method for determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BASF CHEMICALS CO LTD
- Filing Date
- 2026-03-12
- Publication Date
- 2026-06-12
Smart Images
Figure SMS_1 
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Abstract
Description
Technical Field
[0001] This invention relates to a method for determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium. Background Technology
[0002] Triphenylphosphine carbonyl acetylacetone rhodium is a core catalyst in the industrial production of butanol and octanol via low-pressure propylene hydroformylation (carbonyl synthesis). Rhodium is very expensive, thus its use results in high production costs. Precisely determining the rhodium content of this catalyst used in the production process is essential for controlling production costs (e.g., catalyst expense settlement, precious metal recovery costs, etc.).
[0003] Existing methods for determining the rhodium content of rhodium catalysts containing triphenylphosphine ligands typically involve pretreatment with highly explosive perchloric acid and high-temperature, high-pressure digestion in hydrochloric acid-hydrogen peroxide. For example, the national standard GB / T 34609.1-2017 employs such a method, in which the sample is pretreated with nitric acid, hydrochloric acid, and perchloric acid, then digested under high temperature and pressure in a polytetrafluoroethylene digester with hydrochloric acid-hydrogen peroxide. In a slightly acidic solution of rhodium chloride complexes, rhodium is precipitated as a double salt using hexaammonium cobalt nitrate, and the rhodium content is determined gravimetrically. In this method, rhodium precipitates as a double salt, and no elemental rhodium is obtained. Therefore, a specialized process is required to recover the expensive rhodium after the rhodium content determination, resulting in additional time and cost. Furthermore, this method uses highly hazardous reagents, involves complex experimental procedures, and has a long cycle (exceeding 30 hours). The method used in national standard GB / T 33913.1-2017 is also performed under similar conditions.
[0004] In existing methods, the use of perchloric acid and high-temperature, high-pressure treatment under hydrochloric acid-hydrogen peroxide conditions is crucial for the complete digestion of rhodium catalysts containing triphenylphosphine ligands, thereby ensuring the accuracy of rhodium content measurement. Currently, no method has been reported that can completely digest rhodium catalysts containing triphenylphosphine ligands without using perchloric acid and hydrochloric acid-hydrogen peroxide conditions under high temperature and pressure.
[0005] Therefore, for industrial production using triphenylphosphine carbonyl acetylacetone rhodium as a catalyst, it is ideal to develop a more efficient, safer, and more cost-effective method for determining rhodium content. Summary of the Invention
[0006] The purpose of this invention is to provide an analytical method for accurately determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium in a shorter time, under safer process conditions, and for directly recovering rhodium metal.
[0007] This invention achieves its objective by pretreating rhodium triphenylphosphine carbonyl acetylacetone with aqua regia, concentrated nitric acid, and concentrated sulfuric acid, and by combining gravimetric analysis and inductively coupled plasma optical emission spectrometry (ICP-OES).
[0008] This invention provides a method for determining the rhodium content of rhodium triphenylphosphine carbonyl acetylacetone, comprising: digesting rhodium triphenylphosphine carbonyl acetylacetone with aqua regia and treating with concentrated sulfuric acid at high temperature; reducing and precipitating rhodium in solution with a reducing agent, and separating the precipitate and filtrate; reducing the precipitate with hydrogen to obtain recovered metallic rhodium; determining the rhodium content in the filtrate using ICP-OES; and calculating the rhodium content of rhodium triphenylphosphine carbonyl acetylacetone by the sum of the weight of the recovered metallic rhodium and the weight of rhodium in the filtrate determined by ICP-OES.
[0009] Specifically, the present invention provides a method for determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium, which includes the following steps: (1) Digestion with aqua regia and concentrated nitric acid: Weigh a sample weighing 0.20000 g to 0.50000 g into a container and record the weight as m; first digest the sample with aqua regia, then digest it with concentrated nitric acid, then digest it with aqua regia again, and cool it to room temperature; (2) Concentrated sulfuric acid treatment: Add concentrated sulfuric acid to the product of step (1), heat at a temperature in the range of 250 ℃ to 340 ℃ until no more smoke is emitted, then add aqua regia to dissolve and obtain a solution; (3) Denitrification: Add concentrated hydrochloric acid to the solution obtained in step (2) and evaporate to dryness under heating; after cooling to room temperature, moisten the sample with water, add concentrated hydrochloric acid, evaporate to dryness under heating, repeat the process until no more yellow fumes are produced, and cool to room temperature; (4) Metal reduction: Add water to the denitration product obtained in step (3) to obtain a red solution, optionally add an alkaline pH adjuster, add a reducing agent; heat the obtained solution to produce a black precipitate, and stop heating and cool after the color of the solution disappears; (5) Filtration: Provide a dry filter and record its weight as m0; transfer the black precipitate and solution from the container in step (4) into the filter; wipe the inner wall of the container from step (4) with an ashing material to transfer the remaining black precipitate into the filter, and put the wiped ashing material into the filter; rinse the black precipitate with a nitric acid solution of 5% to 10% concentration and hot water, dilute the filtrate with water and record the volume as v, as the filtrate to be tested; (6) Drying and calcination: The filter containing the black precipitate and ashing material from step (5) is heated and dried, then calcined at a temperature above 600 °C and cooled; (7) Hydrogen reduction: The filter containing black powder from step (6) is heated and reduced in a hydrogen reduction apparatus, and then cooled in an inert atmosphere to obtain metallic rhodium; (8) Weighing: Weigh the filter containing rhodium that has been cooled to room temperature and record the weight as m1; (9) Analyze the filtrate: Determine the concentration of rhodium in the filtrate from step (5) by ICP-OES at a wavelength of 343.488 nm, and record the concentration as c; (10) Calculation: Calculate the rhodium content in the sample according to the following formula.
[0010] m: Sample weight, g; m0: Weight of the filter, in grams; m1: Weight of the filter and rhodium, in grams; c: Rhodium concentration in the filtrate, mg / L; v: The final volume of the filtrate, in L.
[0011] On the one hand, compared with conventional methods, the method according to the present invention avoids the explosion hazard associated with perchloric acid and eliminates the need for high-temperature and high-pressure digestion, thereby improving the safety and ease of operation of the rhodium content determination method. The method according to the present invention also significantly shortens the experimental cycle; compared with existing standard methods (such as GB / T 34609.1-2017), it can shorten the experimental cycle by 8 hours for content determination alone. If the recovery of metallic rhodium is also considered, the method according to the present invention further shortens the experimental cycle compared with existing standard methods (such as GB / T 34609.1-2017).
[0012] On the other hand, the method of the present invention successfully solves the problem of incomplete digestion of rhodium catalysts containing triphenylphosphine ligands caused by the absence of perchloric acid and high-temperature, high-pressure digestion conditions. Unexpectedly, by combining aqua regia and concentrated nitric acid digestion with concentrated sulfuric acid treatment, the complete digestion of triphenylphosphine carbonyl acetylacetone rhodium is ensured while reducing process hazards, thus ensuring the accuracy of rhodium content determination.
[0013] Furthermore, the method according to the present invention achieves the recovery of metallic rhodium while accurately determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium, which is very beneficial for reducing production costs and improving efficiency. Detailed Implementation
[0014] In this document, unless otherwise specified, all terms are used in the standard or conventional sense in the field of chemistry. For example, “concentrated sulfuric acid” refers to an aqueous solution of sulfuric acid with a weight concentration between 95% and 98%; “concentrated nitric acid” refers to an aqueous solution of nitric acid with a weight concentration between 65% and 68%; “concentrated hydrochloric acid” refers to an aqueous solution of hydrochloric acid with a weight concentration of approximately 37%; and “aqua regia” refers to a mixture of concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 3:1.
[0015] As mentioned above, the present invention provides a method for determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium, which includes the following steps: (1) Digestion with aqua regia and concentrated nitric acid: Weigh a sample weighing 0.20000 g to 0.50000 g into a container and record the weight as m; first digest the sample with aqua regia, then digest it with concentrated nitric acid, then digest it with aqua regia again, and cool it to room temperature; (2) Concentrated sulfuric acid treatment: Add concentrated sulfuric acid to the product of step (1), heat at a temperature in the range of 250 ℃ to 340 ℃ until no more smoke is emitted, then add aqua regia to dissolve and obtain a solution; (3) Denitrification: Add concentrated hydrochloric acid to the solution obtained in step (2) and evaporate to dryness under heating; after cooling to room temperature, moisten the sample with water, add concentrated hydrochloric acid, evaporate to dryness under heating, repeat the process until no more yellow fumes are produced, and cool to room temperature; (4) Metal reduction: Add water to the denitration product obtained in step (3) to obtain a red solution, optionally add an alkaline pH adjuster, add a reducing agent; heat the obtained solution to produce a black precipitate, and stop heating and cool after the color of the solution disappears; (5) Filtration: Provide a dry filter and record its weight as m0; transfer the black precipitate and solution from the container in step (4) into the filter; wipe the inner wall of the container from step (4) with an ashing material to transfer the remaining black precipitate into the filter, and put the wiped ashing material into the filter; rinse the black precipitate with a nitric acid solution of 5% to 10% concentration and hot water, dilute the filtrate with water and record the volume as v, as the filtrate to be tested; (6) Drying and calcination: The filter containing the black precipitate and ashing material from step (5) is heated and dried, then calcined at a temperature above 600 °C and cooled; (7) Hydrogen reduction: The filter containing black powder from step (6) is heated and reduced in a hydrogen reduction apparatus, and then cooled in an inert atmosphere to obtain metallic rhodium; (8) Weighing: Weigh the filter containing rhodium that has been cooled to room temperature and record the weight as m1; (9) Analyze the filtrate: Determine the concentration of rhodium in the filtrate from step (5) by ICP-OES at a wavelength of 343.488 nm, and record the concentration as c; (10) Calculation: Calculate the rhodium content in the sample according to the following formula.
[0016] m: Sample weight, g; m0: Weight of the filter, in grams; m1: Weight of the filter and rhodium, in grams; c: Rhodium concentration in the filtrate, mg / L; v: The final volume of the filtrate, in L.
[0017] Step (1) — Digestion with aqua regia and concentrated nitric acid
[0018] (1.1) Weigh the sample
[0019] Weigh a sample of 0.20000 g to 0.50000 g into a container (e.g., a beaker) and record the weight as m.
[0020] If the sample weight (m) is less than 0.20000 g, the amount of rhodium obtained after reduction will be too small, resulting in a relatively large weighing error. If the sample weight (m) is greater than 0.50000 g, the amount of rhodium obtained after reduction will be larger, which can reduce the weighing error, but the sample digestion time will be longer. Therefore, weighing a sample with a weight between 0.20000 g and 0.50000 g is most desirable.
[0021] (1.2) Aqua regia digestion
[0022] First, the sample weighed into the container is digested with aqua regia. For example, aqua regia can be added to the container, boiled, and evaporated to dryness, and this process is preferably repeated at least once, usually once or twice. Preferably, after each evaporation to dryness, the residue is cooled to room temperature. The aqua regia digestion residue is obtained from the above operations.
[0023] The amount of aqua regia can be selected from 15 mL to 20 mL, preferably 18 mL to 20 mL. When aqua regia is added more than once, the amount of aqua regia refers to the amount added each time.
[0024] Preferably, the boiling and evaporation to dryness in step (1.2) can be carried out at a temperature in the range of 175 °C to 185 °C, preferably at 180 °C.
[0025] (1.3) Digestion of concentrated nitric acid
[0026] The resulting aqua regia digestion residue is further digested with concentrated nitric acid. For example, concentrated nitric acid can be added to the aqua regia digestion residue, boiled, and evaporated to dryness, and this process is preferably repeated at least once until an oily clump residue is obtained. Preferably, after each evaporation to dryness, the evaporated residue is cooled to room temperature.
[0027] Preferably, the resulting oily clump residue is further heated at an elevated temperature (e.g., 200 °C) until no more white vapor is produced. The concentrated nitric acid digestion residue is obtained from the aforementioned operation.
[0028] The amount of concentrated nitric acid can be selected from 5 mL to 10 mL, preferably 5 mL to 7 mL. When concentrated nitric acid is added more than once, the amount of concentrated nitric acid refers to the amount added each time.
[0029] Preferably, the boiling and evaporation to dryness in step (1.3) can be carried out at a temperature in the range of 175 °C to 185 °C.
[0030] (1.4) Aqua regia further dissolves
[0031] The resulting concentrated nitric acid digestion residue is further digested with aqua regia to ensure complete sample digestion. For example, aqua regia can be added to the concentrated nitric acid digestion residue, boiled, and evaporated to dryness; this process can optionally be repeated at least once. The digestion product is obtained from the foregoing operations. Preferably, after each evaporation to dryness, the evaporated residue is cooled to room temperature.
[0032] Preferably, the boiling and evaporation to dryness in step (1.4) can be carried out at a temperature in the range of 195 °C to 205 °C, preferably at 200 °C.
[0033] The amount of aqua regia can be selected from 5 mL to 10 mL, preferably 5 mL to 7 mL. When aqua regia is added more than once, the amount of aqua regia refers to the amount added each time.
[0034] The digestion product is cooled to room temperature for use in the concentrated sulfuric acid treatment in step (2).
[0035] Step (2) — Concentrated sulfuric acid treatment
[0036] Add concentrated sulfuric acid to the digestion product of step (1) and heat it at a temperature in the range of 250 °C to 340 °C, preferably in the range of 300 °C to 340 °C, until it no longer smokes; then add aqua regia to dissolve it and obtain a solution.
[0037] Organic matter in the digestion product can be removed by treating it with concentrated sulfuric acid through fuming. The amount of concentrated sulfuric acid can be selected from 2 mL to 4 mL. If the amount of concentrated sulfuric acid added is less than 2 mL, the organic matter in the digestion product cannot be completely removed. If the amount of concentrated sulfuric acid added is more than 4 mL, it will have an adverse effect on the metal reduction in the subsequent step (4).
[0038] For example, if too much concentrated sulfuric acid is used in this step, on the one hand, the solution after metal reduction in step (4) will always be gray, making it impossible to judge whether the metal reduction is complete by the solution color. On the other hand, in order to avoid the sulfuric acid remaining in the system from adversely affecting the occurrence of the reduction reaction, a large amount of salt will be generated. Once the salt precipitates out of the solution, it is difficult to separate from the reduced metal rhodium, affecting the accuracy of the final Rh content determination.
[0039] After cooling to room temperature, aqua regia is added to the residue after the concentrated sulfuric acid fumigation treatment to dissolve the residue and obtain a solution. The amount of aqua regia can be selected from 4 mL to 6 mL, preferably 5 mL.
[0040] Step (3) — Denitrification
[0041] Add concentrated hydrochloric acid to the solution obtained in step (2), and evaporate to dryness under heating; after cooling to room temperature, wet the sample with water, add concentrated hydrochloric acid, and evaporate to dryness under heating. Repeat this process until no more yellow fumes are produced, and then cool to room temperature. The denitrification product is obtained from the above operations.
[0042] Residual nitric acid in the system can be removed by evaporation under concentrated hydrochloric acid. Complete removal of nitric acid can be determined by the absence of any observed yellow fumes from its decomposition.
[0043] The amount of concentrated hydrochloric acid can be selected from 3 mL to 5 mL, preferably 4 mL to 5 mL, based on the amount added each time. The heating can be carried out at a temperature in the range of 130 °C to 150 °C, preferably in the range of 135 °C to 140 °C.
[0044] Step (4) — Metal Reduction
[0045] Adding water to the denitrification product obtained in step (3) yields a product containing [RhCl6]. 3- A red solution of complex ions is optionally mixed with an alkaline pH adjuster and a reducing agent; the resulting solution is heated to produce a black precipitate; heating is stopped and the solution is cooled after the color of the solution disappears.
[0046] The amount of water can be selected from 50 mL to 150 mL, preferably from 70 to 120 mL.
[0047] There are no particular restrictions on the reducing agent used in step (4), and any reducing agent known for precious metal recovery may be used. For example, a suitable reducing agent may be selected from one or more of formic acid, hydrazine hydrate, stannous chloride, sodium borohydride, and hydrazine acetate. Preferably, hydrazine hydrate is used as the reducing agent. The reducing agent may be used in a form known per se, such as in an aqueous solution.
[0048] Depending on the specific substance used as a reducing agent, the amount of reducing agent can be selected from different ranges. Those skilled in the art can determine the appropriate amount of reducing agent based on the actual reducing agent used, as long as the reduction reaction is ensured to proceed completely (for example, one of the signs of a complete reduction reaction is the disappearance of the red color of the solution).
[0049] Optionally, the pH of the red solution can be adjusted to a value greater than 7, preferably in the range of 8 to 14, and more preferably in the range of 12 to 14, by adding an alkaline pH adjuster. In particular, when using one or more of formic acid, hydrazine hydrate, sodium borohydride, and hydrazine acetate as a reducing agent, an alkaline pH adjuster is added to adjust the solution to a pH value greater than 7, preferably in the range of 8 to 14, and more preferably in the range of 12 to 14.
[0050] There are no particular restrictions on alkaline pH adjusters, as long as they do not react with substances in the system (such as chloride ions) to form a precipitate. For example, sodium hydroxide solution or potassium hydroxide solution can be used.
[0051] Preferably, when using an alkaline pH adjuster, the alkaline pH adjuster is added first, followed by the reducing agent.
[0052] The heating process can be carried out at temperatures ranging from 250 °C to 300 °C, preferably from 280 °C to 300 °C. During heating, the oxidized rhodium in the solution is reduced to metallic rhodium, forming a black precipitate. As the reduction proceeds, the red color of the solution gradually lightens. Heating is stopped and the solution is cooled after the color disappears.
[0053] Step (5) — Filtering
[0054] (5.1) Prepare the filter
[0055] For the purposes of this invention, a suitable filter is a high-temperature ignition resistant filter. For example, a filter-type crucible containing ignition-resistant filter paper can be used as the filter. Typical examples of filter-type crucibles are Gooch crucibles, quartz crucibles, etc. Typical examples of ignition-resistant filter paper are glass fiber filter paper, ceramic fiber filter paper, quartz fiber filter paper, etc. Preferably, a Gooch crucible containing glass fiber filter paper is used as the filter in this step.
[0056] Before use, dry the filter to provide a dry filter. Weigh the dry filter and record its weight as m0.
[0057] (5.2) Transfer and Filtering
[0058] Transfer the black precipitate and solution from the container in step (4) to the prepared filter.
[0059] In order to transfer all the black precipitate in the container, the inner wall of the container from step (4) is wiped with an ashing material to transfer the remaining black precipitate on the inner wall into the filter, and the wiped ashing material is placed into the filter.
[0060] In this article, "ashable material" refers to a material that can be completely burned or decomposed at high temperatures (e.g., 500 °C) with very low ash residue (or which can be easily removed by subsequent processing), also known as ashless material. Typical ashable materials include, for example, ashable filter paper (ashless filter paper), especially quantitative filter paper.
[0061] After the transfer is complete, the black precipitate in the filter is rinsed with a nitric acid solution with a concentration in the range of 5% to 10% and hot water to remove residual reducing agent and, optionally, alkaline pH adjusters and other impurities. For example, the black precipitate in the filter is rinsed first with a nitric acid solution and then with hot water. The volume of the nitric acid solution used can be in the range of 80 mL to 120 mL, preferably 90 mL to 110 mL. The volume of the hot water used can be in the range of 150 mL to 350 mL, preferably 200 mL to 300 mL. Preferably, the total amount of nitric acid solution and hot water used for rinsing does not exceed 400 mL, preferably not more than 300 mL.
[0062] The filtration process can be carried out using ordinary filtration or vacuum filtration, with vacuum filtration being preferred.
[0063] (5.3) Make up the volume of filtrate.
[0064] The collected filtrate is diluted to volume with water and the volume is recorded as v. Volume dilution can be performed using known methods, such as transferring the filtrate to a volumetric flask and adding water to the mark. For example, the filtrate can be diluted to 500 mL. The diluted filtrate will be used as the test solution in step (9).
[0065] Step (6) — Drying and calcining
[0066] The filter containing the black precipitate and ashable material from step (5) is heated and dried to remove residual moisture. The heating and drying can be carried out at a temperature ranging from 80°C to 120°C, preferably from 100°C to 110°C. For example, the heating and drying can be carried out in an oven. There is no particular limitation on the heating and drying time, as long as the residual moisture is sufficiently removed. For example, the heating and drying can be carried out for 5 to 15 minutes.
[0067] The dried filter is then incinerated at a temperature above 600 °C, preferably in the range of 700 °C to 800 °C, to burn off the ashing material used for wiping. Typically, incineration lasts for at least 80 minutes to ensure complete removal of the ashing material without residue. The incineration can be carried out in a conventional high-temperature furnace in an air atmosphere. For example, the incineration can be performed in a muffle furnace.
[0068] After burning, only black powder remains in the filter. The black powder mainly consists of metallic rhodium and a small amount of rhodium oxide, because metallic rhodium can oxidize during the burning process.
[0069] Step (7) — Hydrogen reduction
[0070] The filter containing the black powder from step (6) is heated and reduced in a hydrogen reduction apparatus. Hydrogen (H2) can be used as the reducing gas, or a mixture of hydrogen and an inert gas (such as argon) can be used as the reducing gas.
[0071] The heating reduction is preferably carried out at a temperature in the range of 600 °C to 700 °C. Typically, the reaction system can be preheated to a specified temperature in the range of 600 °C to 700 °C, and then a reducing gas, such as H2 or an H2 / Ar mixture (e.g., 5% H2 / 95% Ar), is introduced. The preheating can be completed within 10 to 20 minutes.
[0072] The reducing gas is continuously introduced for at least 20 minutes, for example, 20 to 40 minutes, to completely convert the black powder containing rhodium oxide into metallic rhodium. Hydrogen reduction yields metallic rhodium with a gray metallic luster.
[0073] After reduction, an inert gas, such as argon or nitrogen, is introduced into the system to cool the filter containing rhodium in an inert atmosphere. The cooled filter containing rhodium is then removed for weighing in step (8). If necessary (e.g., if the filter is removed before cooling to room temperature or cannot be weighed immediately after removal), the removed filter can be placed in a desiccator, preferably a desiccator with an inert atmosphere, before weighing.
[0074] Step (8) — Weighing
[0075] Weigh the filter containing rhodium that has been cooled to room temperature and record the weight as m1.
[0076] Step (9) — Analyze the filtrate
[0077] The concentration of rhodium in the filtrate from step (5) was determined by ICP-OES (inductively coupled plasma optical emission spectrometry) at a wavelength of 343.488 nm and recorded as c.
[0078] The conditions and parameter settings required for ICP-OES analysis can be selected based on the specific instrument used. For example, in some implementation schemes, the condition and parameter settings shown in the table below can be used:
[0079] Step (10) — Calculation
[0080] The rhodium content in the sample is calculated using the following formula:
[0081] m: Sample weight, g; m0: Weight of the filter, in grams; m1: Weight of the filter and rhodium, in grams; c: Rhodium concentration in the filtrate, mg / L; v: The final volume of the filtrate, in L.
[0082] In the method according to the invention, in any of steps (1) to (4), during heating, it is preferable to cover the container with a non-sealed lid, such as a watch glass, to avoid potential losses due to splashing during heating.
[0083] Unless otherwise specified, the heating in steps (1) to (4) can be performed using any heating device, preferably a temperature-controlled heating device. Under laboratory conditions, a heating plate is preferred for the heating operation.
[0084] Detailed Implementation Plan
[0085] Implementation Scheme 1. A method for determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium, comprising the following steps: (1) Digestion with aqua regia and concentrated nitric acid: Weigh a sample weighing 0.20000 g to 0.50000 g into a container and record the weight as m; first digest the sample with aqua regia, then digest it with concentrated nitric acid, then digest it with aqua regia again, and cool it to room temperature; (2) Concentrated sulfuric acid treatment: Add concentrated sulfuric acid to the product of step (1), heat at a temperature in the range of 250 ℃ to 340 ℃ until no more smoke is emitted, then add aqua regia to dissolve and obtain a solution; (3) Denitrification: Add concentrated hydrochloric acid to the solution obtained in step (2) and evaporate to dryness under heating; after cooling to room temperature, moisten the sample with water, add concentrated hydrochloric acid, evaporate to dryness under heating, repeat the process until no more yellow fumes are produced, and cool to room temperature; (4) Metal reduction: Add water to the denitration product obtained in step (3) to obtain a red solution, optionally add an alkaline pH adjuster, add a reducing agent; heat the obtained solution to produce a black precipitate, and stop heating and cool after the color of the solution disappears; (5) Filtration: Provide a dry filter and record its weight as m0; transfer the black precipitate and solution from the container in step (4) into the filter; wipe the inner wall of the container from step (4) with an ashing material to transfer the remaining black precipitate into the filter, and put the wiped ashing material into the filter; rinse the black precipitate with a nitric acid solution of 5% to 10% concentration and hot water, dilute the filtrate with water and record the volume as v, as the filtrate to be tested; (6) Drying and calcination: The filter containing the black precipitate and ashing material from step (5) is heated and dried, then calcined at a temperature above 600 °C and cooled; (7) Hydrogen reduction: The filter containing black powder from step (6) is heated and reduced in a hydrogen reduction apparatus, and then cooled in an inert atmosphere to obtain metallic rhodium; (8) Weighing: Weigh the filter containing rhodium that has been cooled to room temperature and record the weight as m1; (9) Analyze the filtrate: Determine the concentration of rhodium in the filtrate from step (5) by ICP-OES at a wavelength of 343.488 nm, and record the concentration as c; (10) Calculation: Calculate the rhodium content in the sample according to the following formula.
[0086] m: Sample weight, g; m0: Weight of the filter, in grams; m1: Weight of the filter and rhodium, in grams; c: Rhodium concentration in the filtrate, mg / L; v: The final volume of the filtrate, in L.
[0087] 2. The method according to implementation scheme 1, wherein step (1) includes: (1.1) Weigh a sample weighing between 0.20000 g and 0.50000 g into the container and record this weight as m. (1.2) After adding aqua regia, boil and evaporate to dryness to digest the sample, and repeat this digestion at least once. (1.3) Add concentrated nitric acid to the product of step (1.2), boil and evaporate to dryness to further digest the sample, and repeat this digestion at least once until an oily mass is obtained. Then increase the temperature and continue heating until no white vapor is produced. (1.4) Add aqua regia to the product of step (1.3), boil and evaporate to dryness, optionally repeat the above operation at least once to obtain the digestion product, and cool it to room temperature.
[0088] 3. The method according to implementation scheme 2, wherein in step (1.2), the amount of aqua regia added is in the range of 15 mL to 20 mL, based on the amount added each time.
[0089] 4. The method according to implementation scheme 3, wherein in step (1.2), the amount of aqua regia added is in the range of 18 mL to 20 mL, based on the amount added each time.
[0090] 5. The method according to any one of embodiments 2 to 4, wherein, in step (1.3), the amount of concentrated nitric acid added is in the range of 5 mL to 10 mL, based on the amount added each time.
[0091] 6. The method according to embodiment 5, wherein in step (1.3), the amount of concentrated nitric acid added is in the range of 5 mL to 7 mL, based on the amount added each time.
[0092] 7. The method according to any one of embodiments 2 to 6, wherein in step (1.4), the amount of aqua regia added is in the range of 5 mL to 10 mL.
[0093] 8. The method according to embodiment 7, wherein in step (1.4), the amount of aqua regia added is in the range of 5 mL to 7 mL.
[0094] 9. The method according to any one of embodiments 1 to 8, wherein, in step (2), the heating is performed at a temperature in the range of 300 °C to 340 °C.
[0095] 10. The method according to any one of embodiments 1 to 9, wherein in step (2), the amount of concentrated sulfuric acid added is in the range of 2 mL to 4 mL.
[0096] 11. The method according to any one of embodiments 1 to 10, wherein in step (2), the amount of aqua regia added is in the range of 4 mL to 6 mL.
[0097] 12. The method according to any one of embodiments 1 to 11, wherein in step (3), the amount of concentrated hydrochloric acid added is in the range of 3 mL to 5 mL, based on the amount added each time.
[0098] 13. The method according to embodiment 12, wherein the amount of concentrated hydrochloric acid added in step (3) is in the range of 4 mL to 5 mL.
[0099] 14. The method according to any one of embodiments 1 to 13, wherein, in step (3), the heating is performed at a temperature in the range of 130°C to 150°C.
[0100] 15. The method according to embodiment 14, wherein, in step (3), the heating is performed at a temperature in the range of 135 °C to 140 °C.
[0101] 16. The method according to any one of embodiments 1 to 15, wherein, in step (4), the reducing agent is selected from one or more of formic acid, hydrazine hydrate, stannous chloride, sodium borohydride and hydrazine acetate.
[0102] 17. The method according to embodiment 16, wherein, in step (4), the reducing agent is selected from hydrazine hydrate.
[0103] 18. The method according to any one of embodiments 1 to 17, wherein, in step (4), the reduction is carried out at a pH greater than 7.
[0104] 19. The method according to embodiment 18, wherein, in step (4), the reduction is carried out at a pH in the range of 8 to 14.
[0105] 20. The method according to embodiment 18, wherein in step (4), the reduction is carried out at a pH in the range of 12 to 14.
[0106] 21. The method according to any one of embodiments 1 to 20, wherein the amount of water added in step (4) is in the range of 50 mL to 150 mL.
[0107] 22. The method according to embodiment 21, wherein the amount of water added in step (4) is in the range of 70 to 120 mL.
[0108] 23. The method according to any one of embodiments 1 to 22, wherein, in step (4), the heating is performed at a temperature in the range of 250°C to 300°C.
[0109] 24. The method according to embodiment 23, wherein in step (4), the heating is performed at a temperature in the range of 280 °C to 300 °C.
[0110] 25. The method according to any one of embodiments 1 to 24, wherein in step (5), the amount of the nitric acid solution used is in the range of 80 mL to 120 mL.
[0111] 26. The method according to embodiment 25, wherein in step (5), the amount of nitric acid solution used is in the range of 90 mL to 110 mL.
[0112] 27. The method according to any one of embodiments 1 to 26, wherein, in step (6), the burning is carried out at a temperature above 600 °C.
[0113] 28. The method according to embodiment 27, wherein in step (6), the burning is carried out at a temperature in the range of 700 °C to 800 °C.
[0114] 29. The method according to embodiment 27 or 28, wherein, in step (6), the burning is performed for at least 80 minutes.
[0115] The present invention will be further described below with reference to specific embodiments.
[0116] Example
[0117] In the following embodiments, all operations were performed at atmospheric pressure and room temperature (ambient temperature in a laboratory setting), and all percentages are by weight unless otherwise specified.
[0118] The triphenylphosphine carbonyl acetylacetone rhodium used as the test sample was a given rhodium content of 20.9% from McCarthy's reagent.
[0119] Example 1
[0120] The rhodium content of triphenylphosphine carbonyl acetylacetone rhodium was determined according to the method of the present invention.
[0121] Weigh the sample and record the weight as m. Place the sample in a 250 mL beaker. Add 20 mL of aqua regia to the beaker, boil at 180 °C and evaporate to dryness. Repeat this process twice. Then, add 5 mL of concentrated nitric acid, boil at 180 °C and evaporate to dryness. Repeat this process until an oily clump residue is obtained. Increase the heating temperature from 180 °C to 200 °C and continue heating until no white vapor rises. Add 5 mL of aqua regia to the residue, boil at 200 °C and evaporate to dryness, then cool to room temperature.
[0122] Add 2 mL of concentrated sulfuric acid to the beaker and heat at 340 °C until fumes are observed. After the fumes cease, cool to room temperature and add 5 mL of aqua regia to dissolve the contents of the beaker, thus obtaining a solution.
[0123] Add 5 mL of concentrated hydrochloric acid to the aforementioned solution and cover with a watch glass. Evaporate the sample to dryness on a hot plate at 135 °C. Remove the beaker from the hot plate and cool to room temperature. Wet the sample with water, then add another 5 mL of concentrated hydrochloric acid and cover with a watch glass. Evaporate the sample to dryness on a hot plate at 135 °C. Repeat the above steps until no more yellow fumes are observed. Then remove the beaker from the hot plate and cool to room temperature.
[0124] Add 100 mL of water to the beaker to dissolve the contents, yielding a blood-red solution. Add 10-20 drops of 50% sodium hydroxide aqueous solution to this solution until the pH is between 12 and 14, then add 3 mL of 80% hydrazine hydrate solution. Place the beaker, covered with a watch glass, on a heating plate at 300 °C and heat until a black precipitate forms. When the solution is partially clear and the red color disappears, remove the beaker from the heating plate and cool to room temperature.
[0125] Place dry glass fiber filter paper at the bottom of the Goohl crucible and weigh the total weight of the crucible and filter paper, recording this weight as m0. Pour the black precipitate and solution from the beaker into the Goohl crucible for vacuum filtration. Wipe the inner wall of the beaker with Whatman #541 reinforced ashless filter paper and place the filter paper into the Goohl crucible, ensuring that all precipitate is completely transferred to the crucible. Rinse the precipitate with 100 mL of 10% nitric acid solution, then rinse with hot water until the filtrate volume is 400 mL. Transfer the filtrate to a 500 mL volumetric flask and dilute to the mark with water.
[0126] The Gooch crucible containing the precipitate and filter paper was placed in an oven and dried at 110 °C for 10 minutes, and then transferred to a muffle furnace at 700 °C and calcined for 80 minutes.
[0127] The cooled Gooch crucible was removed from the muffle furnace and placed in a hydrogen reduction apparatus, where it was heated to 700 °C for 15 minutes. Then, at this temperature, a mixture of 5% H₂ and 95% Ar was introduced for 30 minutes. After heating and the introduction of the mixture were stopped, the crucible was cooled for 45 minutes while argon was introduced.
[0128] Remove the Gooch crucible containing metallic rhodium from the hydrogen reduction apparatus, place it in a desiccator to cool to room temperature, weigh it, and record the weight as m1.
[0129] Under the conditions shown in Table 1, the aforementioned diluted filtrate was tested using an Agilent 5110 ICP-OES to determine the rhodium concentration in the filtrate, which was denoted as c.
[0130] Table 1
[0131] Calculate the Rh content (Rh%) in the sample using the following formula:
[0132] m: Sample weight, g; m0: Weight of the Gooch crucible and glass fiber filter paper, in grams; m1: Weight of the Gooch crucible, glass fiber filter paper, and rhodium, in g; c: The concentration of rhodium in the filtrate, mg / L; v: The final volume of the filtrate, in L.
[0133] Example 2
[0134] According to GB / T 34609.1-2017, "Chemical Analysis Methods for Rhodium Compounds", Part 1, Hexaammonium Nitrate Cobalt Gravimetric Method, the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium was determined.
[0135] Weigh the sample and record the weight as m. Place the sample in a 100 mL beaker, add 10 mL of nitric acid, cover with a watch glass, and heat on a hot plate until dissolved without yellow fumes. Remove and let cool slightly. Add 5 mL of perchloric acid and evaporate to 3 mL. Open the watch glass and evaporate to near dryness. Cover with the watch glass, add 10 mL of hydrochloric acid, and evaporate to 1 mL. Rinse the surface and beaker walls with water, and heat on a hot plate to 1 mL. Transfer 20 mL of hydrochloric acid to a polytetrafluoroethylene digestion vessel, add 5 mL of hydrogen peroxide, and place in an oven at 150 °C for digestion for 5 hours. Remove and cool.
[0136] Transfer the digested solution from the PTFE digestion vessel to a 500 mL beaker, distill down to 1 mL, remove the beaker, add water to 300 mL, cover with a watch glass, heat to 60 °C, add 5 g of sodium nitrite, and continue heating until the solution boils. While stirring, add 25 mL of saturated hexaammonium cobalt nitrate solution, and continue stirring until a large amount of precipitate forms. Maintain a gentle boil for 10 minutes. Immerse the beaker in cold water to cool for 1 hour.
[0137] Filter the mixture using a pre-washed, dried, and constant-weighted No. 4 glass frit crucible. Record the weight of the crucible as m'1. Use a glass rod with a rubber tip to wipe off the precipitate adhering to the beaker wall. Wash the precipitate completely into the glass frit crucible using hexaammonium cobalt nitrate washing solution. Wash the precipitate twice more with hexaammonium cobalt nitrate washing solution, then three times with anhydrous ethanol and once with ether. Place the glass frit crucible in a glass vacuum desiccator and dry for 30 minutes. Weigh the crucible and dry it again until constant weight is achieved. Weigh the crucible and the rhodium double salt precipitate; record the weight as m2.
[0138] Perform a blank test along with the same sample and record it as m'0.
[0139] The rhodium content (Rh%) of the sample is calculated using the following formula:
[0140] m: Sample weight, g; m'1: Weight of the crucible, in grams; m2: Weight of the rhodium complex salt precipitate and crucible, in grams; m'0: blank value, g; 0.19054: The factor for converting rhodium complex salts to rhodium.
[0141] Three determinations were performed according to the methods of Examples 1 and 2, and the average rhodium content and relative standard deviation of the three determinations were calculated. The determination results are shown in Tables 3 and 4.
[0142] Table 3
[0143] Table 4
[0144] The test results clearly show that the method according to the present invention not only achieves satisfactory accuracy, which is very close to the measurement of the standard method, but also achieves accuracy that is even higher than that of the standard method; and it also achieves direct recovery of metallic rhodium while greatly shortening the test cycle.
Claims
1. A method for determining the rhodium content of triphenylphosphine carbonyl acetylacetone rhodium, comprising the following steps: (1) Digestion with aqua regia and concentrated nitric acid: Weigh a sample weighing 0.20000 g to 0.50000 g into a container and record the weight as m; first digest the sample with aqua regia, then digest it with concentrated nitric acid, then digest it with aqua regia again, and cool it to room temperature; (2) Concentrated sulfuric acid treatment: Add concentrated sulfuric acid to the product of step (1), heat at a temperature in the range of 250 ℃ to 340 ℃ until no more smoke is emitted, then add aqua regia to dissolve and obtain a solution; (3) Denitrification: Add concentrated hydrochloric acid to the solution obtained in step (2) and evaporate to dryness under heating; after cooling to room temperature, moisten the sample with water, add concentrated hydrochloric acid, evaporate to dryness under heating, repeat the process until no more yellow fumes are produced, and cool to room temperature; (4) Metal reduction: Add water to the denitration product obtained in step (3) to obtain a red solution, optionally add an alkaline pH adjuster, add a reducing agent; heat the obtained solution to produce a black precipitate, and stop heating and cool after the color of the solution disappears; (5) Filtration: Provide a dry filter, the weight of which is recorded as m0; transfer the black precipitate and solution from the container in step (4) into the filter; Wipe the inner wall of the container from step (4) with an ashing material to transfer the remaining black precipitate into the filter, and put the wiped ashing material into the filter; rinse the black precipitate with a nitric acid solution of 5% to 10% and hot water, dilute the filtrate with water and record the volume as v, as the filtrate to be tested; (6) Drying and calcination: The filter containing the black precipitate and ashing material from step (5) is heated and dried, then calcined at a temperature above 600 °C and cooled; (7) Hydrogen reduction: The filter containing black powder from step (6) is heated and reduced in a hydrogen reduction apparatus, and then cooled in an inert atmosphere to obtain metallic rhodium; (8) Weighing: Weigh the filter containing rhodium that has been cooled to room temperature and record the weight as m1; (9) Analyze the filtrate: Determine the concentration of rhodium in the filtrate from step (5) by ICP-OES at a wavelength of 343.488 nm, and record the concentration as c; (10) Calculation: Calculate the rhodium content in the sample according to the following formula. m: Sample weight, g; m0: Weight of the filter, in grams; m1: Weight of the filter and rhodium, in grams; c: Rhodium concentration in the filtrate, mg / L; v: The final volume of the filtrate, in L.
2. The method according to claim 1, wherein, Step (1) includes: (1.1) Weigh a sample weighing between 0.20000 g and 0.50000 g into the container and record this weight as m. (1.2) After adding aqua regia, boil and evaporate to dryness to digest the sample, and repeat this digestion at least once. (1.3) Add concentrated nitric acid to the product of step (1.2), boil and evaporate to dryness to further digest the sample, and repeat this digestion at least once until an oily mass is obtained. Then increase the temperature and continue heating until no white vapor is produced. (1.4) Add aqua regia to the product of step (1.3), boil and evaporate to dryness, optionally repeat the above operation at least once to obtain the digestion product, and cool it to room temperature.
3. The method according to claim 2, wherein, In step (1.2), the amount of aqua regia added is in the range of 15 mL to 20 mL, preferably in the range of 18 mL to 20 mL, based on the amount added each time.
4. The method according to claim 2 or 3, wherein, In step (1.3), the amount of concentrated nitric acid added is in the range of 5 mL to 10 mL, preferably in the range of 5 mL to 7 mL, based on the amount added each time.
5. The method according to any one of claims 2 to 4, wherein, In step (1.4), the amount of aqua regia added is in the range of 5 mL to 10 mL, preferably in the range of 5 mL to 7 mL.
6. The method according to any one of claims 1 to 5, wherein, In step (2), the heating is carried out at a temperature in the range of 300 °C to 340 °C.
7. The method according to any one of claims 1 to 6, wherein, In step (2), the amount of concentrated sulfuric acid added is in the range of 2 mL to 4 mL.
8. The method according to any one of claims 1 to 7, wherein, In step (2), the amount of aqua regia added is in the range of 4 mL to 6 mL.
9. The method according to any one of claims 1 to 8, wherein, In step (3), the amount of concentrated hydrochloric acid added is in the range of 3 mL to 5 mL, preferably in the range of 4 mL to 5 mL, based on the amount added each time.
10. The method according to any one of claims 1 to 9, wherein, In step (3), the heating is carried out at a temperature in the range of 130 ℃ to 150 ℃, preferably in the range of 135 ℃ to 140 ℃.
11. The method according to any one of claims 1 to 10, wherein, In step (4), the reducing agent is selected from one or more of formic acid, hydrazine hydrate, stannous chloride, sodium borohydride and hydrazine acetate, preferably hydrazine hydrate.
12. The method according to any one of claims 1 to 11, wherein, In step (4), the reduction is carried out at a pH greater than 7, preferably in the range of 8 to 14, and more preferably in the range of 12 to 14.
13. The method according to any one of claims 1 to 12, wherein, The amount of water added in step (4) is in the range of 50 mL to 150 mL, preferably in the range of 70 to 120 mL.
14. The method according to any one of claims 1 to 13, wherein, In step (4), the heating is carried out at a temperature in the range of 250 °C to 300 °C, preferably in the range of 280 °C to 300 °C.
15. The method according to any one of claims 1 to 14, wherein, In step (5), the amount of nitric acid solution used is in the range of 80 mL to 120 mL, preferably in the range of 90 mL to 110 mL.
16. The method according to any one of claims 1 to 15, wherein, In step (6), the burning is carried out at a temperature above 600°C, preferably in the range of 700°C to 800°C, and preferably for at least 80 minutes.