Method for preparing high-activity magnesium oxide by taking hydrated magnesium carbonate as precursor
By mixing hydromagnesite with magnesium hydroxide and decomposing at lower temperatures, the method addresses the agglomeration and CO2 emission issues in traditional hydromagnesite decomposition, resulting in high-activity magnesium oxide with enhanced properties for catalytic and adsorptive applications.
Patent Information
- Application Number
- CN202510703832.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-29
- Publication Date
- 2025-07-15
AI Technical Summary
In the prior art, when using hydrated magnesium carbonate as a precursor to produce highly active magnesium oxide, a higher calcination temperature is required, resulting in agglomeration of MgO particles, a decrease in specific surface area, and carbon dioxide release affects the pore structure of the product.
The calcination is carried out by mixing magnesium carbonate with magnesium hydroxide. By controlling the calcination temperature and pH value, the synergistic decomposition of magnesium hydroxide and magnesium carbonate is generated, the calcination temperature is reduced, and the water vapor generated by the decomposition of magnesium hydroxide is used as a pore-making agent to improve the morphology and pore structure of magnesium oxide.
The calcination temperature is reduced, the specific surface area and porosity of magnesium oxide is increased, the particle sintering is reduced, its application performance in catalyst carriers or adsorbents is improved, and carbon dioxide emissions are reduced.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of chemical material synthesis, and particularly relates to a method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor. Background Art
[0002] Hydrated basic magnesium carbonate (usually expressed as MgCO3·nH2O) is a common magnesium compound and can be converted into highly active magnesium oxide by thermal decomposition. However, when directly using hydrated basic magnesium carbonate as a precursor, a relatively high calcination temperature is often required, usually calcined at >600 °C. Direct thermal decomposition may cause agglomeration of MgO particles and a decrease in specific surface area; the release of carbon dioxide may affect the pore structure of the product. Summary of the Invention
[0003] The technical problem to be solved by the present invention is
[0004] To achieve the above object, the present invention is implemented by adopting the following technical solutions:
[0005] A method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor, the specific steps include:
[0006] 1) Dissolve industrial salt in deionized water and stir evenly to obtain a salt solution;
[0007] 2) Filter to remove insoluble impurities;
[0008] 3) Add ammonia water to the filtered salt solution while stirring the solution, control the pH value of the solution between 8 - 10, and sodium nitrite will react with ammonia water to generate nitrogen and water;
[0009] 4) Heat the salt solution pretreated in step 3) to 60 - 80 °C and stir evenly; slowly add sodium hydroxide solution and control the pH value of the solution between 10 - 11;
[0010] 5) Filtration and washing: Filter the generated magnesium hydroxide precipitate and wash it with deionized water multiple times to remove residual chloride ions and sodium ions;
[0011] 6) Dry the washed magnesium hydroxide at 100 - 120 °C until constant weight;
[0012] 7) Mixing: Mix magnesium hydroxide with hydrated basic magnesium carbonate in a mass ratio of 1:(1 - 2);
[0013] 8) Drying: Dry the mixture at 100 - 120 °C to remove the surface moisture and crystal water of hydrated basic magnesium carbonate, and the drying time is 2 - 3 hours until constant weight;
[0014] 9) Calcination: Calcinate the dried product;
[0015] 10) After pulverization and screening, the finished magnesium oxide product is obtained.
[0016] The particle size range of the hydrated basic magnesium carbonate is from 0.5 μm to 23 μm.
[0017] The mass percentage concentration of the salt solution is 10% - 20%.
[0018] In step 3), 10 - 15 mL of 25% ammonia water is added to every 1 g of industrial salt.
[0019] The calcination heating process in step 9): Heating-up stage: Heating up to 400 - 500 °C at a heating rate of 3 - 5 °C / min; Constant-temperature stage: Maintaining at 400 - 500 °C for 2 - 3 hours; Cooling-down stage: Naturally cooling to room temperature.
[0020] Compared with the existing technology, the beneficial effects of the present invention are:
[0021] In this application, the hydrated basic magnesium carbonate and magnesium hydroxide are mixed and then calcined. Its advantages include:
[0022] Reducing the calcination temperature, the decomposition temperature of magnesium hydroxide is lower than that of hydrated basic magnesium carbonate. After mixing, the overall pyrolysis energy consumption can be reduced. Synergistic effect: Decomposing to generate active MgO and H2O, which may promote the decomposition kinetics of hydrated basic magnesium carbonate.
[0023] Improving the product morphology and pore structure, the water vapor generated by the decomposition of magnesium hydroxide can be used as a pore-forming agent, increasing the specific surface area and porosity of magnesium oxide, and enhancing its application performance in catalyst carriers or adsorbents. Reducing particle sintering to obtain more uniform nanoscale MgO particles.
[0024] Regulating the basic sites of the product, the introduction of magnesium hydroxide may increase the density of basic sites on the surface of MgO, which is suitable for reactions requiring basic catalysis.
[0025] Reducing carbon dioxide emissions, partially replacing hydrated basic magnesium carbonate can reduce the CO2 release amount during the calcination process, which better meets the requirements of green chemical industry.
[0026] The purity of the magnesium oxide prepared in this application can reach more than 98%. Specific embodiments
[0028] Unless otherwise clearly specified and defined, the terms "installation", "connection", and "linkage" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0029] A method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor, the specific steps including:
[0030] 1) Dissolve industrial salt in deionized water and stir evenly to obtain a salt solution;
[0031] 2) Filter to remove insoluble impurities;
[0032] 3) Add ammonia water to the filtered salt solution while stirring the solution, control the pH value of the solution between 8 and 10, and sodium nitrite will react with ammonia water to generate nitrogen and water.
[0033] The reaction equation is as follows: NaNO2 + NH3·H2O → NaOH + N2↑ + 2H2O
[0034] Heat the solution to 60 - 80 °C to accelerate the reaction, keep stirring to ensure that the reaction proceeds fully, filter to remove insoluble impurities after the reaction, and wash the filtrate with deionized water multiple times to remove the residual ammonia water and reaction by-products.
[0035] 4) Heat the salt solution pretreated in step 3) to 60 - 80 °C and stir evenly; slowly add sodium hydroxide solution, control the pH value of the solution between 10 and 11, and precipitate the magnesium ions Mg2+ in the salt solution as magnesium hydroxide Mg(OH)2.
[0036] The reaction equation: Mg2+ + 2OH- → Mg(OH)2↓
[0037] 5) Filtration and washing: Filter the generated magnesium hydroxide precipitate, wash it with deionized water multiple times to remove the residual chloride ions (Cl-) and sodium ions (Na+);
[0038] 6) Dry the washed magnesium hydroxide at 100 - 120 °C until constant weight;
[0039] 7) Mixing: Mix magnesium hydroxide with hydrated basic magnesium carbonate in a mass ratio of 1:(1 - 2).
[0040] 8) Drying to remove moisture: Dry at 100 - 120 °C to remove the surface moisture and crystal water from the hydrated basic magnesium carbonate. The drying time is 2 - 3 hours until constant weight. The dried product is anhydrous basic magnesium carbonate MgCO3.
[0041] Reaction equation: MgCO3·nH2O → MgCO3 + nH2O
[0042] 9) Calcination: Put the dried product into calcination. During the calcination process, basic magnesium carbonate and magnesium hydroxide decompose into magnesium oxide. The reaction equations are as follows: MgCO3 → MgO + CO2↑
[0043] Mg(OH)2 → MgO + H2O
[0044] 10) Crush and screen to obtain the finished magnesium oxide product.
[0045] The particle size range of the hydrated basic magnesium carbonate is from 0.5 μm to 23 μm.
[0046] The mass percentage concentration of the salt solution is 10% - 20%.
[0047] In step 3), 10 - 15 mL of 25% ammonia water is added to every 1 g of industrial salt.
[0048] Step 9) Calcination heating process: Heating-up stage: Heat up to 400 - 500 °C at a heating rate of 3 - 5 °C / min. Constant-temperature stage: Maintain at 400 - 500 °C for 2 - 3 hours. Cooling-down stage: Naturally cool to room temperature.
[0049] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Additionally, it should be noted that in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention does not further describe various possible combination methods. Furthermore, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.
[0050] To make the purpose, technical solutions and technical effects of the present invention clearer, the technical solutions in the embodiments of the present invention are now described clearly and completely. However, the embodiments described below are only a part of the embodiments of the present invention, not all of the embodiments. Combining the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.
[0051] Example 1:
[0052] A method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor, the specific steps include:
[0053] 1) Dissolve industrial salt: Weigh 200 g of industrial salt and dissolve it in 1 L of deionized water, stir evenly to obtain a salt solution with a mass percentage concentration of 20%.
[0054] 2) Filter impurities: Filter the above salt solution to remove insoluble impurities.
[0055] 3) Remove sodium nitrite: Add 300 mL of 25% ammonia water to the filtered salt solution, stir the solution simultaneously, and control the pH value of the solution between 9 and 10. Sodium nitrite reacts with ammonia water to produce nitrogen and water.
[0056] 4) Precipitate magnesium hydroxide: Heat the salt solution pretreated in step 3) to 70 °C, stir evenly; slowly add 200 mL of 1 mol / L sodium hydroxide solution, and control the pH value of the solution between 10 and 11.
[0057] 5) Filter and wash: Filter the precipitated magnesium hydroxide, wash it with deionized water multiple times to remove residual chloride ions and sodium ions.
[0058] 6) Dry magnesium hydroxide: Dry the washed magnesium hydroxide at 120 °C until constant weight.
[0059] 7) Mix: Mix the dried magnesium hydroxide and hydrated basic magnesium carbonate in a mass ratio of 1:1. The particle size range of the hydrated basic magnesium carbonate is 5 μm - 15 μm.
[0060] 8) Dry the mixture: Dry the mixture at 120 °C for 2 hours to remove the surface moisture and crystal water of the hydrated basic magnesium carbonate until constant weight.
[0061] 9) Calcination: Calcinate the dried product, and the specific process is as follows:
[0062] Heating stage: Heat to 450 °C at a heating rate of 4 °C / min.
[0063] Isothermal stage: Hold at 450 °C for 2 hours.
[0064] Cooling stage: Naturally cool to room temperature.
[0065] 10) Crushing and screening: Crush and screen the calcined product to obtain the finished product of highly active magnesium oxide.
[0066] Example 2:
[0067] A method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor, the specific steps including:
[0068] 1) Dissolve industrial salt: Weigh 150 g of industrial salt and dissolve it in 800 mL of deionized water, stir evenly to obtain a salt solution with a mass percentage concentration of 15%.
[0069] 2) Filter impurities: Filter the above salt solution to remove insoluble impurities.
[0070] 3) Remove sodium nitrite: Add 225 mL of 25% ammonia water to the filtered salt solution, while stirring the solution, control the pH value of the solution between 8 - 10. Sodium nitrite reacts with ammonia water to generate nitrogen and water.
[0071] 4) Precipitate magnesium hydroxide: Heat the salt solution pretreated in step 3) to 65 °C, stir evenly; slowly add 150 mL of 1 mol / L sodium hydroxide solution, control the pH value of the solution between 10 - 11.
[0072] 5) Filter and wash: Filter the generated magnesium hydroxide precipitate, wash it with deionized water multiple times to remove residual chloride ions and sodium ions.
[0073] 6) Dry magnesium hydroxide: Dry the washed magnesium hydroxide at 110 °C until constant weight.
[0074] 7) Mix: Mix the dried magnesium hydroxide with hydrated basic magnesium carbonate in a mass ratio of 1:1.5. The particle size range of hydrated basic magnesium carbonate is 10 μm - 20 μm.
[0075] 8) Dry the mixture: Dry the mixture at 110 °C for 2.5 hours to remove the surface moisture and crystal water of hydrated basic magnesium carbonate until constant weight.
[0076] 9) Calcinate: Calcinate the dried product, the specific process is as follows:
[0077] Heating stage: Raise the temperature to 400 °C at a heating rate of 3 °C / min.
[0078] Constant temperature stage: Maintain at 400 °C for 3 hours.
[0079] Cooling stage: Naturally cool to room temperature.
[0080] 10) Crush and screen: Crush and screen the calcined product to obtain the finished product of highly active magnesium oxide.
[0081] Comparison table of performance indicators of magnesium oxide products in the examples
[0082]
[0083]
[0084] Specific surface area and activity
[0085] In Example 2, due to low-temperature calcination (400 °C) and a higher proportion of magnesium hydroxide (1:1.5), the hydrated basic magnesium carbonate and the gases (CO2, H2O) generated by the decomposition of magnesium hydroxide cooperate to form pores, resulting in more mesoporous structures, significantly enhancing the specific surface area and iodine adsorption activity.
[0086] Purity and loss on ignition
[0087] The high-temperature constant-temperature stage (450 °C × 2 h) in Example 1 is more conducive to the complete decomposition of carbonate and hydroxyl groups in the precursor, but may sacrifice some porosity.
[0088] Particle size control
[0089] In Tube Example 2, the raw material particle size is larger (10 - 20 μm), but the low-temperature slow heating rate (3 °C / min) reduces particle sintering, and the final product is finer instead.
[0090] Example 1 is suitable for fields with high requirements for purity and alkalinity, such as refractory materials and pharmaceutical-grade MgO.
[0091] Example 2 is suitable for scenarios requiring high specific surface area and activity, such as environmental adsorbents, catalyst carriers, or rubber flame retardants.
[0092] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and basic spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor, characterized in that, The specific steps include: 1) Dissolve industrial salt in deionized water and stir evenly to obtain a salt solution; 2) Filter to remove insoluble impurities; 3) Add ammonia water to the filtered salt solution while stirring the solution, control the pH value of the solution between 8 and 10, and sodium nitrite will react with ammonia water to generate nitrogen and water; 4) Heat the salt solution pretreated in step 3) to 60 - 80 °C and stir evenly; slowly add sodium hydroxide solution and control the pH value of the solution between 10 and 11; 5) Filtration and washing: Filter the generated magnesium hydroxide precipitate and wash it with deionized water multiple times to remove residual chloride ions and sodium ions; 6) Dry the washed magnesium hydroxide at 100 - 120 °C until constant weight; 7) Mixing: Mix magnesium hydroxide with basic magnesium carbonate hydrate with a mass ratio of 1:(1 - 2); 8) Drying: Dry the mixture at 100 - 120 °C to remove the surface moisture and crystal water of basic magnesium carbonate hydrate, and the drying time is 2 - 3 hours until constant weight; 9) Calcination: Calcinate the dried product; 10) Obtain the finished magnesium oxide product after pulverization and screening.
2. The method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor according to claim 1, characterized in that, The particle size range of the basic magnesium carbonate hydrate is 0.5 μm to 23 μm.
3. A method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor according to claim 1, characterized in that, The mass percentage concentration of the salt solution is 10% - 20%.
4. A method for preparing highly active magnesium oxide using hydrated magnesium carbonate as a precursor according to claim 1, characterized in that, In step 3), 10 - 15 mL of 25% ammonia water is added per 1 g of industrial salt.
5. A method for preparing highly active magnesium oxide using magnesium carbonate hydrate as a precursor according to claim 1, characterized in that, Step 9) Calcination heating process: Heating-up stage: Raise the temperature to 400 - 500 °C at a heating rate of 3 - 5 °C / min; Constant-temperature stage: Keep at 400 - 500 °C for 2 - 3 hours; Cooling-down stage: Naturally cool to room temperature.