Preparation process of basic copper carbonate and application thereof in preparation of active copper oxide

Abstract

The application discloses a preparation process of basic copper carbonate and application of the basic copper carbonate in preparation of active copper oxide, relates to the technical field of copper oxide preparation, and comprises the following steps: synchronously feeding NH3H2O, CO2 and copper sulfate solution, and obtaining the precipitate by reaction, namely the basic copper carbonate; and the prepared basic copper carbonate is calcined to obtain the active copper oxide. The application replaces ammonium bicarbonate with carbon dioxide, realizes resource utilization of greenhouse gases, greatly reduces raw material procurement cost, simultaneously reduces ammonia-nitrogen wastewater discharge from the source, reduces three-waste treatment investment, and has outstanding green and low-carbon advantages; a standardized coprecipitation system with synchronous feeding, ventilation, constant temperature and pH control is established, the reaction process is controllable by limiting the molar excess ratio of raw materials, the basic copper carbonate precursor with pure phase, uniform particle size and no caking can be stably prepared, and after calcination, the copper oxide powder is loose and porous, has high specific surface area, and is excellent in catalytic and dissolution activity, batch quality is stable, and the rate of defective products is low.

Description

Technical Field

[0001] This invention relates to the field of copper oxide preparation technology, specifically to a preparation process for basic copper carbonate and its application in the preparation of active copper oxide. Background Technology

[0002] Activated copper oxide is a type of copper-based functional powder material with high specific surface area and porous structure. It possesses characteristics such as rapid dissolution rate, high catalytic activity, and low impurity content, and is widely used in precision copper plating of PCB circuit boards, organic synthesis catalysis, flue gas desulfurization, lithium battery electronic materials, and ceramic glazes. It is an irreplaceable key raw material in the electronics, chemical, and fine catalysis industries. The mainstream industrial preparation route involves liquid-phase precipitation to prepare basic copper carbonate precursors, followed by low-temperature controlled calcination to obtain activated copper oxide. The grain morphology, purity, and particle size uniformity of basic copper carbonate directly determine the pore structure, specific surface area, and catalytic activity of the calcined copper oxide. Therefore, the basic copper carbonate synthesis process is the core link restricting the quality of high-activity copper oxide mass production.

[0003] The most mature traditional process for the industrial production of basic copper carbonate is the copper sulfate-ammonium bicarbonate co-precipitation method. The reaction principle involves ammonium bicarbonate dissociating to provide carbonate ions, which synergistically form a complex with copper ions and ammonia in copper sulfate to produce basic copper carbonate precipitate. A calcination process then produces copper oxide. This process has mild reaction conditions and low equipment requirements, and has long dominated the production capacity of small and medium-sized copper salt manufacturers in China. However, with the upgrading of domestic environmental regulations, the implementation of carbon emission reduction policies, and the continuous increase in demand for highly active, low-impurity copper oxide from the downstream electronics industry, the raw material costs, environmental defects, and product quality shortcomings of the traditional ammonium bicarbonate process have become increasingly prominent, making it difficult to meet the requirements of modern green mass production. The traditional ammonium bicarbonate process suffers from the following core defects: high raw material costs, strong dependence on external carbon sources (ammonium bicarbonate is a specialized chemical fertilizer raw material requiring external procurement), severe ammonia nitrogen pollution, and poor controllability of product particle size.

[0004] Therefore, providing a novel preparation process for basic copper carbonate and its application in the preparation of active copper oxide is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a process for preparing basic copper carbonate and its application in the preparation of active copper oxide.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A process for preparing basic copper carbonate specifically includes the following steps:

[0008] NH3·H2O, CO2, and copper sulfate solution are fed simultaneously, and the reaction is carried out at 35-50℃ to obtain a precipitate, which is basic copper carbonate.

[0009] This invention prepares basic copper carbonate by replacing ammonium bicarbonate with CO2. The carbon source is carbon dioxide produced as a byproduct of lime kiln tail gas and fermentation industrial waste gas. The raw materials are widely available and the procurement cost is extremely low. Compared with purchasing ammonium bicarbonate, it can significantly reduce the raw material cost for large-scale production and enhance the market competitiveness of the product. In terms of environmental protection, on the one hand, it recovers industrial waste gas CO2 in a resource-based manner, reducing direct greenhouse gas emissions and meeting the requirements of low-carbon circular production. On the other hand, it eliminates the need for ammonium bicarbonate feeding, eliminating the introduction of extra ammonium ions into the production system at the source, significantly reducing the generation of high ammonia nitrogen wastewater, avoiding the pressure of nitrogen pollutant emission treatment, and significantly reducing the investment and operation and maintenance costs of end-of-pipe waste treatment, demonstrating outstanding environmental friendliness.

[0010] This invention involves the simultaneous and continuous feeding and aeration of copper sulfate, ammonia, and carbon dioxide. The system has a uniform and stable carbonate and ammonia complexation environment, preventing localized sudden increases in carbonate or insufficient ammonia. It can stably generate pure-phase basic copper carbonate, avoiding the formation of impurity phases such as copper hydroxide and free copper oxide. It also eliminates the possibility of unqualified precursor phases leading to product scrap after calcination.

[0011] The relevant principles are as follows: (1) The conversion of CO2 and ammonia water to supply carbonate ions. Carbon dioxide is an acidic oxide. After being introduced into the ammonia water solution, it can undergo a step reaction with the free ammonia in the system to first generate ammonium carbonate. When carbon dioxide is continuously introduced in excess, the product is further converted into ammonium bicarbonate. Traditional processes rely on the dissociation of purchased ammonium bicarbonate to provide carbonate ions. This invention utilizes industrial CO2 and ammonia water to generate ammonium carbonate and ammonium bicarbonate in situ, which can supply carbonate ions equally. They combine with copper ions in the system to precipitate and generate basic copper carbonate, thus achieving complete substitution of carbon source from the essence of the reaction. Moreover, the ammonia water solution itself has an ionization equilibrium. The continuous introduction of CO2 can dynamically adjust the carbonate concentration in the system and stably maintain the ion environment required for the precipitation reaction.

[0012] (2) Promotes the hydrolysis of copper ions and drives the precipitation of basic copper carbonate. In the aqueous solution of copper sulfate, copper ions are in hydrolysis equilibrium. Carbon dioxide dissolves in water to form carbonic acid, which dissociates to produce carbonate ions. The carbonate ions can combine with the copper ions produced by hydrolysis, continuously consuming free copper ions, promoting the positive shift of the copper ion hydrolysis equilibrium, and continuously precipitating basic copper carbonate solid, providing thermodynamically favorable conditions for the precipitation reaction.

[0013] Preferably, the reaction temperature is 40-45°C.

[0014] The temperature of this invention needs to be controlled at around 40℃. When the temperature is above 55℃, black copper oxide impurities will be generated. If the temperature is too low, the reaction will be slow, so real-time temperature control is required. If the temperature exceeds the limit, the temperature should be lowered immediately, and if the temperature is below 40℃, the temperature should be raised slowly. At the same time, the precipitation reaction of this invention only requires low-temperature micro-heating and does not require special high-temperature and high-pressure equipment. It can achieve mass production with conventional water baths, metering pumps, and atmospheric pressure reactors. The initial investment in equipment and the daily heating energy consumption are significantly lower than those of high-temperature synthesis processes. The equipment investment threshold is low, the production heating energy consumption is low, and industrial implementation is convenient.

[0015] Preferably, the copper sulfate solution contains Cu 2+ The molar ratio of Cu to NH3·H2O is not higher than 2:2.2, and the Cu in the copper sulfate solution... 2+ The molar ratio of CO2 to CO2 should not exceed 2:1.2.

[0016] Preferably, both NH3·H2O and CO2 are in excess by 5-20%.

[0017] Generally, more ammonia and carbon dioxide are needed to compensate for the incomplete reaction, but the aeration rate and the amount of ammonia added need to be controlled.

[0018] When the carbon dioxide aeration rate is insufficient, the carbonate concentration in the system is low, the copper ion precipitation conversion rate decreases, and the yield of basic copper carbonate decreases. Excessive aeration will significantly change the pH value of the system, easily generating impurities and causing particle agglomeration. Therefore, in production, a flow meter is used to monitor the inlet flow rate in real time, and online pH monitoring is used for linkage adjustment to maintain the stability of the reaction system and ensure the purity of the product phase.

[0019] Insufficient ammonia leads to a low pH, while excessive ammonia results in excessive pH and clumping.

[0020] Preferably, the pH value of the reaction is 6.8-7.2.

[0021] When pH < 6.5: insufficient alkali, low product purity; when pH > 7.5: large particles and agglomeration, impurities are difficult to wash off. This invention precisely controls the carbonate generation rate by adjusting the carbon dioxide flow rate and aeration time, and matching the feeding concentration and dosage of ammonia and copper sulfate solutions. The slow and uniform supply of carbonate can avoid sudden changes in local ion concentration, generating basic copper carbonate precipitate with narrow particle size distribution and no agglomeration, significantly improving the batch stability of the product.

[0022] Preferably, the copper content in the copper sulfate solution is 56.9 g / L, and the NH3·H2O is concentrated ammonia solution with a concentration of 25-28%.

[0023] Preferably, the CO2 is industrial waste gas, but the industrial waste gas carbon dioxide needs to be purified in advance. Impurities in the raw material gas will interfere with the precipitation reaction, be mixed into the precursor, and reduce the purity of the final copper oxide. A purification process needs to be set up before production to ensure that the purity of the CO2 intake gas meets the standard.

[0024] Preferably, the flow rate of the copper sulfate solution is 769.23 ml / min, and the flow rate of the NH3·H2O is 230.77 ml / min.

[0025] Preferably, the amount of concentrated ammonia added is 300-360 mL / L of copper sulfate solution.

[0026] Preferably, the flow rate of the CO2 is 15-25 sccm.

[0027] The flow rate of carbon dioxide must not exceed 30 sccm, and the absolute red line is a flow rate of 35 sccm. When it exceeds 30 sccm, blue copper hydroxide flocculent matter will be produced, indicating that the impurities exceed the standard.

[0028] Preferably, the precipitate further includes washing and drying with deionized water.

[0029] Preferably, the deionized water washing specifically involves washing the precipitate with deionized water, a total of 5 times; each wash is thoroughly stirred until the washing solution is colorless, free of impurity ions, has no ammonia odor, and has a conductivity ≤200.

[0030] Preferably, the drying is performed at a constant temperature of 60°C for 120 minutes.

[0031] The above-described preparation process for basic copper carbonate is applied in the preparation of active copper oxide.

[0032] This invention uses pure-phase basic copper carbonate as a precursor for low-temperature decomposition, which forms a rich porous structure during the decomposition process. Unlike copper hydroxide, which is prone to grain coarsening and pore collapse during calcination, the resulting copper oxide is a brownish-black, loose, and lightweight powder.

[0033] Preferably, the prepared basic copper carbonate is calcined to obtain active copper oxide.

[0034] Preferably, the specific parameters for calcination are as follows: heating from room temperature to 120°C at a heating rate of 2°C / min, then heating from 120°C to 300°C at a heating rate of 1°C / min, heating from 300°C to 360°C at a heating rate of 0.5°C / min, and finally holding at 360°C for 60 minutes and then allowing it to cool naturally.

[0035] This invention strictly controls the upper limit of temperature and the heating rate throughout the calcination process, effectively inhibiting grain agglomeration and growth, resulting in a finished product with high specific surface area and excellent reactivity.

[0036] The maximum temperature during the entire calcination process of this invention must not exceed 400℃. If the temperature exceeds 400℃ during the instantaneous / constant temperature stage, the precursor will decompose and the grains will coarsen, resulting in a complete loss of catalytic activity, and the sample will be directly scrapped. At the same time, prolonged high-temperature constant temperature holding is prohibited: the longer the high-temperature stage is held, the more the grains will continue to agglomerate and grow, the specific surface area will decrease rapidly, and the catalytic activity will be greatly reduced. After heating to the target temperature, the constant temperature holding time should be shortened, and the temperature should be lowered immediately upon reaching the decomposition endpoint.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) This invention utilizes industrial waste gas carbon dioxide to replace purchased ammonium bicarbonate, thereby realizing the resource utilization of greenhouse gases, significantly reducing the cost of raw material procurement, and at the same time reducing the discharge of ammonia nitrogen wastewater from the source, reducing the investment in the treatment of the three wastes, and highlighting the green and low-carbon advantages.

[0039] (2) The preparation method of the present invention establishes a standardized co-precipitation system with synchronous feeding and aeration and constant temperature and pH control. By limiting the molar excess ratio of copper ions, ammonia monohydrate and carbon dioxide, the reaction process is highly controllable and can stably prepare pure phase, uniform particle size and no agglomeration of basic copper carbonate precursor.

[0040] (3) The present invention uses a gradient low-speed heating calcination process to strictly limit the maximum calcination temperature and holding time. The resulting copper oxide powder is loose and porous, has a high specific surface area, excellent catalytic and dissolution activity, stable batch quality, and low defect rate.

[0041] (4) The reaction conditions of the process of the present invention are mild, no high temperature and high pressure equipment is required, the production energy consumption is low, the raw material loss is small, the operation is safe and has high tolerance for error, and it is suitable for the continuous industrial transformation of existing copper salt production lines. The products can meet the needs of high-end markets such as electronic copper plating and fine catalysis. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0043] Figure 1 This is a product image of basic copper carbonate from Example 1 of the present invention;

[0044] Figure 2 This is a diagram of the active copper oxide product from Example 2 of the present invention. Detailed Implementation

[0045] The following describes embodiments of the present invention. These embodiments are exemplary and intended to explain the present invention, and are not to be construed as limiting the present invention.

[0046] Example 1

[0047] This invention provides a process for preparing basic copper carbonate, specifically including the following steps:

[0048] (1) Raw material preparation:

[0049] Copper sulfate solution pretreatment: Take 1L of prepared copper sulfate solution with a copper content of 56.9g / L, remove insoluble solid impurities by filtering, transfer the filtrate to the feed storage tank (connected to an independent metering feed pump), seal and let it stand for later use;

[0050] Ammonia preparation: According to the standard of 300-360mL per liter of copper sulfate, measure 300mL of concentrated ammonia (concentration 25-28%) and transfer it to the feed storage tank (connected to an independent metering feed pump) for later use;

[0051] Carbon dioxide gas source preparation: Check the appearance of the CO2 cylinder and the airtightness of the pressure reducing valve. Connect the gas pipeline to the reactor inlet according to the specifications. After checking for leaks and confirming that there are no leaks, close the valve and wait for use.

[0052] (2) Turn on the water bath heating device to preheat the continuous synthesis reactor of nanomaterials. The preheating time is strictly controlled at 10 minutes to stabilize the temperature of the equipment cavity. Simultaneously start the two metering feed pumps of copper sulfate solution storage tank and ammonia water storage tank to uniformly deliver copper sulfate solution and ammonia water to ensure that the two liquids are fed synchronously and the feeding is completed synchronously. The flow rate of the copper sulfate solution is 769.23 ml / min and the flow rate of NH3·H2O is 230.77 ml / min. At the same time, open the carbon dioxide cylinder valve and set the gas flow rate to 15-25 sccm. The gas introduction time is consistent with the feeding of the two liquids throughout the process. The gas introduction is stopped synchronously. The water bath temperature is controlled at 40℃ throughout the process. The pH value of the reaction system is monitored online in real time. If the pH deviates from the range of 6.8-7.2 during the feeding process, the feeding rate of the two pumps is slightly adjusted to maintain the pH standard range.

[0053] (3) After the reaction is complete, turn off the heating and stirring devices, and allow the entire reaction system to cool naturally to room temperature. Then, use a vacuum filtration device to complete the solid-liquid separation, filter and collect the solid product, and dispose of the filtrate in a unified manner. Wash the solid product with deionized water for a total of 5 times, stirring thoroughly during each wash until the washing liquid is colorless, free of impurity ions, has no ammonia odor, and has a conductivity ≤200. Transfer the washed wet solid product to a clean petri dish, place it in a vacuum drying oven, set the drying temperature to 60℃, and dry at a constant temperature for 120 minutes. After drying, take out the sample and cool it to room temperature. This is basic copper carbonate. See the product image below. Figure 1 ;

[0054] In this embodiment, the flow rate of the relevant substances must be within the protection range of this invention. If the copper sulfate solution is fed in large quantities, a large amount of sky-blue copper hydroxide paste will be generated instantly. Due to the excessively high local copper ion concentration, ammonia water cannot complex in time and directly generates Cu(OH)2, which will coat the surface of the crystal grains. No matter how long carbon dioxide is passed through later, it cannot be eliminated. The finished product turns blue or gray, the purity decreases, and the sulfate ions cannot be washed away cleanly with water. Moreover, if the copper sulfate is fed in too quickly, crystallization will occur explosively, with particles in the micron range. This will clog the filter paper during vacuum filtration and result in extremely poor water permeability during plate and frame filtration, with a water content of over 40%. After drying, the material will clump and harden, with extremely poor activity. The copper carbonate particles added at a uniform rate and in small amounts are coarse and can be dehydrated in ten minutes of pressure filtration.

[0055] Meanwhile, if the amount of copper sulfate is large, it will consume a lot of ammonia water. If the ammonia content in the system is insufficient, carbon dioxide will only precipitate instead of turning into green basic copper carbonate. The product will always be light blue. Once this happens, it is difficult to reverse the situation by adding ammonia water, and the liquid can only be wasted. Moreover, if a large amount of copper sulfate enters at once, the pH will drop from 10 to below 8 in a few minutes. When carbon dioxide is introduced, white anhydrous copper carbonate will be generated directly. It is very easy to hydrolyze and turns white when it comes into contact with water, so it cannot be used as a catalyst. The rapidly precipitated crystal lattice will contain a large amount of ammonium sulfate. Even after washing with water three times, the sulfate content will still exceed the standard, and the impurities in the roasted copper oxide will be too high.

[0056] In summary, the relevant ratios and flow rates defined in this invention are the best conclusions obtained through a large number of inventive experiments, and represent significant progress.

[0057] Example 2

[0058] This invention provides a preparation method for activated copper oxide, specifically including the following steps:

[0059] The basic copper carbonate obtained in Example 1 was calcined to prepare activated copper oxide. (See product image below.) Figure 2 Color: Brownish-black, loose, light, non-clumping, D 50 It has a diameter of approximately 3 μm and a specific surface area of ​​12-16 m². 2 / g, with a main content of 99.5%; the calcination parameters are as follows: heating from room temperature to 120℃ at a heating rate of 2℃ / min, then heating from 120℃ to 300℃ at a heating rate of 1℃ / min, heating from 300℃ to 360℃ at a heating rate of 0.5℃ / min, and finally holding at 360℃ for 60min, followed by natural cooling.

[0060] Traditional preparation methods involve calcining at 450℃ for 2 hours, which results in low activity. This invention uses a gradient low-speed heating calcination process to strictly limit the maximum calcination temperature and holding time, resulting in copper oxide powder that is loose and porous, has a high specific surface area, excellent catalytic and dissolving activities, stable batch quality, and a low defect rate.

[0061] Furthermore, the traditionally synthesized active copper oxide has low activity and the process requires 6 hours or even longer, while the active copper oxide prepared by the synthesis method of this invention has a significantly shorter preparation time.

[0062] Copper oxide activity experiment

[0063] Turn on the thermostatic heating magnetic stirrer, put 100ml of the prepared dilute sulfuric acid solution (water: sulfuric acid = 93:7) into a beaker, place it on the magnetic stirrer, set the temperature to 25℃ and the speed to 960r / min, then pour copper oxide into the dilute acid solution, adjust the speed to 1100r / min, and observe the color change of the solution;

[0064] The active copper oxide prepared in Example 2 of this invention was placed in a dilute sulfuric acid solution and stirred for 20 seconds. The beaker was then removed for observation, and the solution turned blue.

[0065] Copper oxide prepared by the traditional copper sulfate-ammonia-ammonium bicarbonate coprecipitation method turns blue when the beaker is removed and observed after stirring for 50 seconds.

[0066] As can be seen from the above, the activated copper oxide prepared by the method of the present invention has high activity and excellent catalytic and dissolution activities, which are significantly better than the activated copper oxide in the prior art.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for preparing basic copper carbonate, characterized in that, Specifically, the following steps are included: NH3·H2O, CO2, and copper sulfate solution are fed simultaneously, and the reaction is carried out at 35-50℃ to obtain a precipitate, which is basic copper carbonate.

2. The preparation process of basic copper carbonate according to claim 1, characterized in that, Cu in copper sulfate solution 2 + The molar ratio of Cu to NH3·H2O is not higher than 2:2.2, and the Cu in the copper sulfate solution... 2+ The molar ratio of CO2 to CO2 should not exceed 2:1.

2.

3. The preparation process of basic copper carbonate according to claim 1, characterized in that, The pH value of the reaction is 6.8-7.

2.

4. The preparation process of basic copper carbonate according to claim 1, characterized in that, The copper sulfate solution contains 56.9 g / L of copper, and the NH3·H2O is a concentrated ammonia solution with a concentration of 25-28%.

5. The preparation process of basic copper carbonate according to claim 4, characterized in that, The amount of concentrated ammonia added is 300-360 mL / L of copper sulfate solution, the flow rate of the copper sulfate solution is 769.23 mL / min, and the flow rate of NH3·H2O is 230.77 mL / min.

6. The preparation process of basic copper carbonate according to claim 1, characterized in that, The CO2 flow rate is 15-25 sccm.

7. The preparation process of basic copper carbonate according to claim 1, characterized in that, The precipitation process also includes washing and drying with deionized water.

8. The application of the preparation process of basic copper carbonate as described in any one of claims 1-7 in the preparation of active copper oxide.

9. The application according to claim 8, characterized in that, The prepared basic copper carbonate is calcined to obtain active copper oxide.

10. The application according to claim 9, characterized in that, The specific parameters for calcination are as follows: heat from room temperature to 120°C at a heating rate of 2°C / min, then heat from 120°C to 300°C at a heating rate of 1°C / min, then heat from 300°C to 360°C at a heating rate of 0.5°C / min, and finally hold at 360°C for 60 minutes before cooling.

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