Process for preparing chloroplatinic acid powder by using waste platinum-carbon catalyst

Abstract

The invention belongs to the technical field of catalysis, and particularly relates to a process for preparing chloroplatinic acid powder by using a waste platinum-carbon catalyst, which comprises the following steps: S1, stirring materials, roasting and removing carbon; s2, acid dissolution and impurity removal; s3, dissolving crude platinum with aqua regia; s4, precipitating platinum salt and removing impurities; step S5, ammoniation and impurity removal; s6, preparing platinum black through hydrogen reduction; step S7, dissolving platinum black by chlorination; and step S8, atomizing chloroplatinic acid into powder. According to the method, the reagent A and the waste platinum-carbon catalyst are uniformly mixed and roasted, so that the loss of platinum is effectively reduced while carbon is removed. Hydrogen peroxide, hydrogen and chlorine are adopted, no new impurity ions are introduced to pollute the product in the chloroplatinic acid preparation process, the prepared chloroplatinic acid powder has the characteristics of no nitrate, no platinum dichloride and no platinum black, no adverse effect is brought to the subsequent application of the product, and the particle size of the product is 30-200 microns. And convenience is provided for use, weighing, dissolution and the like of subsequent products.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysis, and in particular relates to a process for preparing chloroplatinic acid powder by utilizing waste platinum-carbon catalyst. Background Art

[0002] Platinum carbon catalyst is an important platinum-based catalyst, which is widely used in fine chemicals, pharmaceuticals, petrochemicals and hydrogen energy industries. After a period of use, platinum carbon catalysts will gradually become ineffective due to poisoning, agglomeration and other reasons. Due to the high price of precious metal platinum and the scarcity of precious metal resources in my country, precious metal catalysts need to be recycled and reused after failure. Since the failed waste platinum carbon catalyst contains a large amount of activated carbon and organic matter, it will greatly affect the leaching effect of platinum during the leaching process. Therefore, it is necessary to roast to remove carbon and organic matter before leaching. At present, the main methods for roasting platinum carbon are direct roasting method and granulation roasting method. The direct roasting method is to directly place the waste platinum carbon catalyst in the incinerator for direct incineration. However, due to the low density of the waste platinum carbon catalyst, the incineration process needs to continuously replenish air. This process will produce a lot of smoke and even open flames. Precious metals will flow away with the flue gas and cause losses. The platinum loss rate can reach 2%-10%. The granulation and roasting method is a method in which pulp, flour or organic binder is mixed with waste platinum carbon catalyst in a certain proportion to form particles and then roasted. This roasting method can effectively reduce the loss of platinum, but the platinum loss rate still reaches 0.5%-1%.

[0003] Chloroplatinic acid is one of the most important platinum-based compounds and is almost the precursor or intermediate for preparing all platinum-based catalysts. The preparation methods of chloroplatinic acid mainly include chemical dissolution method and electrochemical dissolution method. The chemical dissolution method generally uses aqua regia to dissolve pure platinum, and obtains chloroplatinic acid solution after operations such as driving out nitrate. The disadvantage of this method is that the prepared chloroplatinic acid solution will have a small amount of nitrate ions remaining, and the nitrate will have an adverse effect on the subsequent application of chloroplatinic acid; another improved chemical dissolution method is to use aqua regia to dissolve pure platinum, add sodium borohydride, hydrazine hydrate, formic acid and other organic or inorganic reducing agents by adjusting pH to obtain highly active platinum black, and finally use hydrochloric acid and hydrogen peroxide to dissolve platinum black to obtain chloroplatinic acid solution. The advantage of this method is that a chloroplatinic acid solution without nitrate can be obtained, but the highly active platinum black will adsorb some organic or inorganic reducing agents during the reduction process due to its high surface area, and even if it is washed multiple times with deionized water, there will still be some residues, which will inevitably have an adverse effect on the purity and subsequent application of chloroplatinic acid. The electrochemical dissolution method is a method for preparing chloroplatinic acid by electrolysis using pure platinum as raw material and hydrochloric acid as electrolyte using direct current or alternating current. Its advantage is that the prepared chloroplatinic acid has the characteristic of being free of nitrate ions. Its disadvantages are slow dissolution rate and incomplete dissolution.

[0004] After the chloroplatinic acid solution is concentrated to a certain concentration, chloroplatinic acid solid can be obtained. However, the chloroplatinic acid solid prepared by the traditional method is mostly block crystals, which is particularly inconvenient for subsequent use, weighing, and dissolution. Moreover, during the concentration process, a small amount of chloroplatinic acid will be converted into chloroplatinous acid. Chloroplatinous acid can only exist in an acidic aqueous solution. Continuous evaporation to dryness will decompose to form platinum dichloride and platinum black, which will cause the chloroplatinic acid solid to contain a small amount of platinum dichloride and platinum black, thereby having a negative impact on the purity of the chloroplatinic acid product and subsequent applications. Summary of the invention

[0005] The object of the present invention is to overcome the deficiencies in the prior art, and provide a process for preparing chloroplatinic acid powder using waste platinum carbon catalyst. The embodiment of the present invention adopts A reagent and waste platinum carbon to mix and roast, and effectively reduces the loss of platinum while achieving the purpose of carbon removal, and the platinum loss rate is reduced to 0.1%. The present invention adopts hydrogen peroxide, hydrogen, and chlorine, and no new impurity ions are introduced to pollute the product during the preparation of chloroplatinic acid. The prepared chloroplatinic acid powder has the characteristics of no nitrate, no platinum dichloride, and no platinum black, and will not have an adverse effect on the subsequent application of the product, and the product particle size is between 30-200 μm, which provides convenience for the use, weighing, and dissolution of subsequent products.

[0006] A process for preparing chloroplatinic acid powder using waste platinum-carbon catalyst comprises the following steps:

[0007] Step S1, mixing materials and roasting to remove carbon: the platinum carbon catalyst and reagent A are evenly mixed and placed in a muffle furnace and roasted at 600-800° C. for 2-5 hours; wherein the reagent A is one or more of barium hydroxide, strontium hydroxide, and calcium hydroxide;

[0008] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0009] C+Me(OH)2→CO↑+H2↑+MeO

[0010] wherein Me is Ba, Sr or Ca;

[0011] Step S2, acid dissolution and impurity removal: the material calcined in step S1 is added into a reactor, and deionized water twice the weight of the material is added, stirring is started, and hydrochloric acid is added dropwise to react. After the reaction is completed, the pH is controlled between 0 and 0.5, and finally the crude platinum is filtered;

[0012] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0013] MeO+HCl→H2O+MeCl2

[0014] Step S3, dissolving crude platinum with aqua regia: the crude platinum from step S2 is put into a reactor, and aqua regia is added to dissolve it at 70-100° C. After the dissolution is completed, the nitrate is removed and filtered to obtain a platinum-containing filtrate;

[0015] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0016] Pt+HCl+HNO3→H2O+H2PtCl6+NO↑

[0017] Step S4, precipitation of platinum salt and impurity removal: the platinum-containing filtrate in step S3 is added to a reactor, stirring is started, and then ammonium chloride is added to react to generate a yellow precipitate, and the platinum salt is obtained by solid-liquid separation and filter cake washing, wherein a small amount of platinum contained in the filtrate is replaced and recovered by adding iron powder, and the replacement residue is transferred to step S3 for re-recovery;

[0018] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0019] H2PtCl6+NH4Cl→HCl+(NH4)2PtCl6↓

[0020] H2PtCl6(filtrate)+Fe→Pt↓+H2↑+FeCl2

[0021] Step S5, ammoniation and impurity removal: deionized water, ammonia water and the platinum salt of step S4 are added into a reactor, stirring is started, the temperature is raised to 70-90° C., hydrogen peroxide is added dropwise to accelerate the dissolution of the platinum salt, and after the platinum salt is completely dissolved, it is cooled to room temperature and filtered to obtain a tetraammine dichloroplatinum solution, and base metal impurities including iron are precipitated and filtered to be removed, thereby achieving the purpose of further purification;

[0022] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0023] (NH4)2PtCl6+NH3·H2O→Pt(NH3)4Cl2+NH4Cl+NH2Cl+H2O

[0024] (NH4)2PtCl6+NH3·H2O+H2O2→Pt(NH3)4Cl2+NH4Cl+O2↑+H2O

[0025] Me'Cl x +NH3·H2O→Me'(OH) x ↓+NH4Cl

[0026] Wherein, Me' is a base metal including Fe;

[0027] Step S6, preparing platinum black by hydrogen reduction: add the tetraammineplatinum dichloride solution of step S5 into the reactor, start stirring, heat to 60-90° C., introduce high-purity nitrogen to exhaust the air in the reactor, then switch to high-purity hydrogen to react for 2-4 hours, finally stop heating and stirring, exhaust the hydrogen in the reactor with high-purity nitrogen, and filter and wash the solution after the temperature drops to room temperature to obtain platinum black;

[0028] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0029] Pt(NH3)4Cl2+H2+H2O→Pt↓+NH4Cl+NH3·H2O

[0030] Step S7, chlorination dissolving platinum black: add the platinum black and hydrochloric acid in step S6 to the reactor, start stirring, raise the temperature to 65-80°C, pass chlorine gas into the solution to dissolve for 1-2h, after the platinum black is completely dissolved, continue to pass chlorine gas and adjust the flow rate to 20-100mL / min, start vacuum, concentrate at 65-80°C, and finally concentrate to a density of chloroplatinic acid solution of 2.2-2.3g / mL;

[0031] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0032] Pt+HCl+Cl2→H2PtCl6

[0033] Step S8, atomizing chloroplatinic acid into powder: turn off the chlorine gas, open the discharge valve and the nitrogen atomizer, atomize the chloroplatinic acid liquid and spray it into a Dewar flask filled with liquid nitrogen, the chloroplatinic acid liquid will quickly solidify into powder, the volume of the liquid nitrogen will not cover the chloroplatinic acid powder, after the discharge is completed, close the discharge valve and the nitrogen atomizer, pour out the excess liquid nitrogen in the Dewar flask, and quickly package the chloroplatinic acid powder;

[0034] The process in this step is as follows:

[0035] H2PtCl6·6H2O(liquid)→H2PtCl6·6H2O(solid).

[0036] Furthermore, in step S1, the mass content of platinum in the waste platinum carbon catalyst is 20%-60%, and the mass ratio of the reagent A: the waste platinum carbon catalyst is 3-7:1.

[0037] Furthermore, in step S5, the mass ratio of hydrogen peroxide: platinum = 0.6-1.8, and the mass ratio of deionized water: ammonia water: platinum = 10-15: 2.5-3.1: 1.

[0038] Furthermore, in step S6, the mass ratio of hydrogen to platinum is 0.1-0.2.

[0039] Furthermore, the particle size of the chloroplatinic acid powder obtained in step S8 is 30-200 μm.

[0040] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0041] 1) The present invention uses reagent A and waste platinum carbon catalyst to mix and roast, which can effectively reduce the loss of platinum while removing carbon.

[0042] 2) The present invention adopts hydrogen peroxide, hydrogen and chlorine, and no new impurity ions are introduced to pollute the product during the preparation of chloroplatinic acid. The prepared chloroplatinic acid powder has the characteristics of no nitrate, no platinum dichloride and no platinum black, and will not bring adverse effects on subsequent applications of the product. The particle size of the product is between 30 and 200 μm, which provides convenience for the use, weighing and dissolution of subsequent products. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The present invention is a process flow chart for preparing chloroplatinic acid powder using waste platinum-carbon catalyst in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] Example 1

[0046] A process for preparing chloroplatinic acid powder using waste platinum-carbon catalyst comprises the following steps:

[0047] Step S1, mixing and roasting to remove carbon: 2000g of platinum carbon catalyst containing 40wt% platinum and 10000g of calcium hydroxide were evenly mixed and placed in a muffle furnace and roasted at 700°C for 3h;

[0048] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0049] C+Ca(OH)2→CO↑+H2↑+CaO

[0050] Step S2, acid dissolution and impurity removal: the material roasted in step S1 is added into a reactor, and 17 kg of deionized water is added, stirring is started, and 31.3 kg of hydrochloric acid with a mass concentration of 35% is added dropwise to react. After the reaction is completed, the pH is 0.1, and finally 1 kg of crude platinum is obtained by filtration;

[0051] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0052] CaO+HCl→H2O+CaCl2

[0053] Step S3, dissolving crude platinum with aqua regia: put the crude platinum from step S2 into a reactor, add 5.5 kg of aqua regia, start stirring, heat to 80°C for dissolution, add 2.5 kg of hydrochloric acid with a mass concentration of 35% to remove nitrate after dissolution, concentrate, cool and filter to obtain 4 L of platinum-containing filtrate;

[0054] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0055] Pt+HCl+HNO3→H2O+H2PtCl6+NO↑

[0056] Step S4, precipitation of platinum salt and impurity removal: add the platinum-containing filtrate in step S3 into a reactor, start stirring, then add 0.8 kg of ammonium chloride to react and generate a yellow precipitate, separate the solid and liquid and wash the filter cake to obtain 2.3 kg of platinum salt, add 10 g of iron powder to the filtrate for displacement, and after the displacement is completed, filter the 1.6 g of displacement residue and transfer it to step S3 for recovery;

[0057] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0058] H2PtCl6+NH4Cl→HCl+(NH4)2PtCl6↓

[0059] H2PtCl6(filtrate)+Fe→Pt↓+H2↑+FeCl2

[0060] Step S5, ammoniation and impurity removal: 12 kg of deionized water, 2.4 kg of ammonia water with a mass concentration of 25%, and the platinum salt of step S4 are added into a reactor, stirring is started, the temperature is raised to 80° C., 0.8 kg of hydrogen peroxide with a mass concentration of 30% is slowly added dropwise to accelerate the dissolution of the platinum salt, and after the platinum salt is completely dissolved, it is cooled to room temperature and filtered to obtain a dichlorotetraammineplatinum solution; base metal impurities including iron are precipitated and filtered to achieve the purpose of further purification;

[0061] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0062] (NH4)2PtCl6+NH3·H2O→Pt(NH3)4Cl2+NH4Cl+NH2Cl+H2O

[0063] (NH4)2PtCl6+NH3·H2O+H2O2→Pt(NH3)4Cl2+NH4Cl+O2↑+H2O

[0064] Me'Cl x +NH3·H2O→Me'(OH) x ↓+NH4Cl

[0065] Wherein, Me' is a base metal including Fe;

[0066] Step S6, preparing platinum black by hydrogen reduction: add the tetraammineplatinum dichloride solution of step S5 into the reactor, start stirring, heat to 80°C, introduce high-purity nitrogen to exhaust the air in the reactor, then switch to high-purity hydrogen to react for 3 hours, the amount of hydrogen used is 120g, stop heating and stirring after the reaction is completed, switch to high-purity nitrogen to exhaust the hydrogen in the reactor, wait until the solution temperature drops to room temperature, filter and wash to obtain 1.2kg of platinum black;

[0067] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0068] Pt(NH3)4Cl2+H2+H2O→Pt↓+NH4Cl+NH3·H2O

[0069] Step S7, chlorination dissolving platinum black: add the platinum black of step S6 and 5kg of hydrochloric acid with a mass concentration of 35% into the reactor, start stirring, heat to 65-80°C, introduce chlorine gas into the solution for dissolution for 1.5h, after the platinum black is completely dissolved, adjust the chlorine gas flow rate to 50mL / min, start vacuum, and concentrate at 65-80°C. During the concentration process, the density of the chloroplatinic acid solution is detected by a density meter. When the density of the chloroplatinic acid solution is 2.25g / mL, turn off the vacuum and stop concentrating;

[0070] The chemical reaction formula of the chemical reaction occurring in this step is as follows:

[0071] Pt+HCl+Cl2→H2PtCl6

[0072] Step S8, atomizing chloroplatinic acid into powder: turn off the chlorine gas, open the discharge valve and the nitrogen atomizer, atomize the chloroplatinic acid liquid and spray it into a Dewar flask filled with liquid nitrogen, and the chloroplatinic acid liquid will quickly solidify into powder. After the discharge is completed, close the discharge valve and the nitrogen atomizer, pour out the excess liquid nitrogen in the Dewar flask, and quickly package the chloroplatinic acid powder to obtain 2018 g of chloroplatinic acid powder.

[0073] The process in this step is as follows:

[0074] H2PtCl6·6H2O(liquid)→H2PtCl6·6H2O(solid).

[0075] The platinum mass fraction of chloroplatinic acid powder was tested to be 37.66%, the purity was 99.99%, the average particle size was 98 μm, no nitrate was detected, and the water solubility test solution was clear and without residue.

[0076] Comparative Example 1

[0077] A direct calcination experiment was conducted on a waste platinum-carbon catalyst containing 40 wt% of platinum at a calcination temperature of 700° C. for 3 h. The experimental results are shown in Table 1.

[0078] Comparative Example 2

[0079] The waste platinum carbon catalyst containing 40wt% of platinum was mixed with flour in a mass ratio of 1:5 for granulation and roasting experiments. The roasting temperature was 700°C and the roasting time was 3h. The experimental results are shown in Table 1.

[0080] Comparative Example 3

[0081] The waste platinum carbon catalyst containing 40wt% of platinum was mixed with calcium hydroxide in a mass ratio of 1:5 for a mixing and calcination experiment. The calcination temperature was 700°C and the calcination time was 3h. The experimental results are shown in Table 1.

[0082] Table 1 Comparison of treatment methods and platinum loss rates of comparative examples 1-3

[0083] name 40wt% waste platinum carbon catalyst (g) Flour(g) Calcium hydroxide (g) Platinum loss rate Comparative Example 1 100 / / 5％ Comparative Example 2 100 500 / 1％ Comparative Example 3 100 / 500 0.1％

[0084] Note: “ / ” in Table 1 means no addition.

[0085] As can be seen from Table 1, the loss rate of platinum is 5% when the waste platinum carbon catalyst is directly roasted for carbon removal, while the loss rate of platinum is significantly reduced when roasting and carbon removal after granulation with flour, but the loss rate of platinum still reaches 1%. Finally, the loss rate of platinum is the lowest when roasting and carbon removal is carried out by mixing with calcium hydroxide, which is only 0.1%. It can be seen that compared with the traditional roasting method in Comparative Examples 1 and 2, Comparative Example 3 can effectively reduce the loss of platinum in the roasting and carbon removal process, and the recovery rate of platinum reaches 99.9%. In addition to the roasting and carbon removal steps of mixing materials in Comparative Example 3, Example 1 of the present invention also includes acid dissolution and impurity removal, aqua regia dissolution of crude platinum, precipitation of platinum salt impurity removal, ammoniation and impurity removal, hydrogen reduction to prepare platinum black, chlorination dissolution of platinum black, and chloroplatinic acid atomization into powder. The platinum mass fraction of the finally obtained chloroplatinic acid powder is 37.66%, and the purity is 99.99%. The waste platinum carbon catalyst is prepared into chloroplatinic acid powder, the loss rate of platinum is low, and the precious metal platinum can be reused.

[0086] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A process for preparing chloroplatinic acid powder using waste platinum-carbon catalyst, characterized in that: The following steps are involved: Step S1, mixing and roasting to remove carbon: evenly mix the platinum carbon catalyst and reagent A, place them in a muffle furnace, and roast them at 600-800° C. for 2-5 hours; Step S2, acid dissolution and impurity removal: the material obtained by calcination in step S1 is added into a reactor, and deionized water twice the weight of the material is added, stirring is started, and hydrochloric acid is added dropwise to react. After the reaction is completed, the pH is controlled between 0 and 0.5, and finally the crude platinum is obtained by filtration; Step S3, dissolving crude platinum with aqua regia: the crude platinum from step S2 is put into a reactor, and aqua regia is added to dissolve it at 70-100° C. After the dissolution is completed, the nitrate is removed and filtered to obtain a platinum-containing filtrate; Step S4, precipitation of platinum salt and impurity removal: the platinum-containing filtrate in step S3 is added to a reactor, stirring is started, and then ammonium chloride is added to react to generate a yellow precipitate, and the platinum salt is obtained by solid-liquid separation and filter cake washing, wherein a small amount of platinum contained in the filtrate is replaced and recovered by adding iron powder, and the replacement residue is transferred to step S3 for re-recovery; Step S5, ammoniation and impurity removal: deionized water, ammonia water and the platinum salt of step S4 are added into a reactor, stirring is started, the temperature is raised to 70-90° C., hydrogen peroxide is added dropwise to accelerate the dissolution of the platinum salt, and after the platinum salt is completely dissolved, the solution is cooled to room temperature and filtered to obtain a dichlorotetraammineplatinum solution; Step S6, preparing platinum black by hydrogen reduction: add the tetraammineplatinum dichloride solution of step S5 into the reactor, start stirring, heat to 60-90° C., introduce high-purity nitrogen to exhaust the air in the reactor, then switch to high-purity hydrogen to react for 2-4 hours, finally stop heating and stirring, exhaust the hydrogen in the reactor with high-purity nitrogen, and filter and wash the solution after the temperature drops to room temperature to obtain platinum black; Step S7, chlorination dissolving platinum black: add the platinum black and hydrochloric acid in step S6 to the reactor, start stirring, raise the temperature to 65-80°C, pass chlorine gas into the solution to dissolve for 1-2h, after the platinum black is completely dissolved, continue to pass chlorine gas and adjust the flow rate to 20-100mL / min, start vacuum, concentrate at 65-80°C, and finally concentrate to a density of chloroplatinic acid solution of 2.2-2.3g / mL; Step S8, atomizing chloroplatinic acid into powder: turn off the chlorine gas, open the discharge valve and the nitrogen atomizer, atomize the chloroplatinic acid liquid and spray it into a Dewar flask filled with liquid nitrogen, the chloroplatinic acid liquid will quickly solidify into powder, the volume of the liquid nitrogen covers the chloroplatinic acid powder, after the discharge is completed, close the discharge valve and the nitrogen atomizer, pour out the excess liquid nitrogen in the Dewar flask, and package the chloroplatinic acid powder.

2. The process for preparing chloroplatinic acid powder using waste platinum-carbon catalyst according to claim 1, characterized in that: In step S1, the mass content of platinum in the waste platinum carbon catalyst is 20%-60%, and the reagent A is one or more of barium hydroxide, strontium hydroxide, and calcium hydroxide. In terms of mass ratio, the reagent A: waste platinum carbon catalyst = 3-7:

1.

3. The process for preparing chloroplatinic acid powder using waste platinum-carbon catalyst according to claim 1, characterized in that: In step S5, the mass ratio is: hydrogen peroxide: platinum = 0.6-1.8, and deionized water: ammonia: platinum = 10-15: 2.5-3.1:

1.

4. The process for preparing chloroplatinic acid powder using waste platinum-carbon catalyst according to claim 1, characterized in that: In step S6, the mass ratio of hydrogen to platinum is 0.1-0.

2.

5. The process for preparing chloroplatinic acid powder using waste platinum-carbon catalyst according to claim 1, characterized in that: The particle size of the chloroplatinic acid powder obtained in step S8 is 30-200 μm.

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