Method for simultaneously preparing calcium propionate and magnesium hydroxide from natural dolomite

Abstract

The invention discloses a method for simultaneously preparing calcium propionate and magnesium hydroxide from natural dolomite, which comprises the following steps: adding dolomite powder into a propionic acid aqueous solution, stirring for 1-6 hours at 10-90 DEG C, then filtering, and collecting filtrate A; adding calcium hydroxide into the filtrate A, standing at 10-90 DEG C for 10-50 minutes, then filtering, and respectively collecting precipitates and filtrate B; drying the precipitate to obtain magnesium hydroxide, and drying the filtrate B at low temperature to obtain calcium propionate; according to the method, natural dolomite is directly acidified by using propionic acid, the total yield of calcium propionate is increased by adding calcium hydroxide to neutralize excessive propionic acid, waste of propionic acid is avoided, and calcium hydroxide precipitates magnesium ions, so that calcium propionate and magnesium hydroxide products are obtained through separation; compared with the prior art, the raw material cost is lower, natural dolomite does not need to be calcined, the process is simple, energy consumption is low, preparation conditions are green and mild, and the method has industrial application prospects.

Description

Technical Field

[0001] This invention relates to a method for simultaneously preparing calcium propionate and magnesium hydroxide from natural dolomite. Background Technology

[0002] Dolomite (CaMg(CO3)2) is a highly valuable calcium and magnesium mineral, abundant in China and with broad application potential. As a rich mineral resource in my country, the key issue in its application is how to separate calcium and magnesium from dolomite to prepare calcium and magnesium products. Current processes for simultaneously preparing calcium and magnesium chemical products from dolomite suffer from incomplete calcium and magnesium separation and complex procedures, leading to a waste of dolomite resources. CN120504334A discloses a calcium and magnesium separation process for dolomite tailings, which involves high-temperature calcination of dolomite for digestion, followed by further separation. This method is simple to operate, but requires high-temperature calcination and has high energy consumption.

[0003] Calcium propionate has excellent preservative properties and is widely used as a feed preservative, in food, grains, and fruits for preservation. In addition, calcium propionate can also be used as a calcium fortifier in the feed and food industries to supplement the calcium needs of livestock during feeding, thus providing both nutritional fortification and preservative functions.

[0004] Magnesium hydroxide is an important inorganic chemical product. It exhibits excellent buffering capacity, reactivity, adsorption capacity, and thermal decomposition properties. It can be used as a chemical material and intermediate, as well as in environmental protection applications such as flame retardants, acidic wastewater neutralizers, and heavy metal wastewater precipitants. It is also a crucial raw material for the production of magnesium oxide. As an inorganic flame retardant, magnesium hydroxide demonstrates excellent thermal stability, complete acid dissolution, and good carbonization of substrates, while also being environmentally friendly and cost-effective. Due to its large specific surface area and strong adsorption capacity, magnesium hydroxide can serve as a high-performance additive, adsorbing and removing heavy metal ions from industrial wastewater, thus achieving environmental protection goals.

[0005] Currently, the preparation methods for calcium propionate generally include the following: First, using a soluble calcium source, such as calcium chloride or calcium hydroxide, to react with propionic acid to obtain calcium propionate, followed by heating or adding ethanol to precipitate the calcium propionate. This method is relatively complex in operation and has a long production time, making it unsuitable for large-scale production. Second, producing propionic acid through microbial fermentation, followed by calcification to obtain calcium propionate. This method is also complex. Third, directly preparing calcium propionate from natural calcium sources, such as eggshells, seashells, or mineral calcium carbonate, through high-temperature calcination followed by acidification with propionic acid. CN102675082B discloses a method for preparing calcium propionate using eggshells, employing a physical method of adding water and stirring to separate the shell membrane, and using a two-stage neutralization reaction method to prepare calcium propionate from eggshell powder. This method is complex, the eggshell raw material is difficult to recover, and the calcination process consumes a large amount of energy.

[0006] There are many methods for preparing magnesium hydroxide, including physical pulverization, direct precipitation, magnesium oxide hydration, electrochemical methods, ultrasonic chemistry, and microwave-assisted methods. Most of these methods require sophisticated equipment, yield products with low purity, and thus have high production costs. Traditional methods for preparing magnesium hydroxide from dolomite mainly include carbonization, ammonium leaching, acid hydrolysis, ion exchange resin methods, and brine methods. Pressurized carbonization requires high-pressure equipment, resulting in large investments, relatively low production capacity, and low purity of the byproduct calcium salt. The one-step ammonium sulfate leaching method has inherent drawbacks such as long production cycles, high costs, and difficulty in controlling sulfate ion levels, leading to potential exceedances. Ion exchange resin methods have improved calcium-magnesium separation, but due to resin costs and regeneration issues, they have not fundamentally reduced production costs. While direct hydrochloric acid hydrolysis is simple to operate and has high calcium-magnesium resource utilization, it causes severe equipment corrosion and environmental pollution. Compared to traditional acid hydrolysis methods, this invention uses a milder propionic acid solution, reducing equipment corrosion and environmental impact.

[0007] Therefore, it is necessary to develop a green, low-energy-consumption method for preparing high-value-added calcium propionate and magnesium hydroxide, which can effectively solve the problems of incomplete calcium-magnesium separation, high production costs, and unstable product quality in existing technologies. This invention uses dolomite as both a calcium and magnesium source to simultaneously prepare calcium propionate and magnesium hydroxide, providing a novel method for separating calcium and magnesium from dolomite to produce these high-value-added products. Currently, there are no reports on the direct acidification of dolomite with propionic acid to separate calcium and magnesium ions using calcium hydroxide precipitation to prepare calcium propionate and magnesium hydroxide. Summary of the Invention

[0008] To address the problems of complex processes, cumbersome steps, requirement for specific equipment, high energy consumption, wastewater pollution, high production costs, and low added value of dolomite products in the current production of calcium propionate and magnesium hydroxide, this invention provides a method for simultaneously preparing calcium propionate and magnesium hydroxide from natural dolomite.

[0009] The technical solution of the present invention is as follows: A method for simultaneously preparing calcium propionate and magnesium hydroxide from natural dolomite includes: Dolomite powder is added to a propionic acid aqueous solution and stirred at 10-90°C (preferably 45-75°C) for 1-6 hours (preferably 2.5-5.5 hours). The mixture is then filtered, and filtrate A is collected. Calcium hydroxide is added to filtrate A and allowed to stand at 10-90°C (preferably 50-80°C) for 10-50 minutes. The mixture is then filtered, and the precipitate and filtrate B are collected separately. The precipitate is dried to obtain magnesium hydroxide, and filtrate B is dried at low temperature to obtain calcium propionate. in, Dolomite powder is obtained by crushing, grinding, sieving and drying natural dolomite; The preferred molar ratio of dolomite powder to propionic acid and calcium hydroxide is 1:1~1.8:1~1.5; The preferred volume fraction of the propionic acid aqueous solution is 5-10%, and the liquid-to-solid ratio of the propionic acid aqueous solution to the dolomite powder is 10-30:1, mL / g; Specifically, the precipitate drying conditions were: 95℃ for 12 hours; the filtrate B low-temperature drying conditions were: -60℃ for 24 hours. The labels “Filtrate A” and “Filtrate B” have no special meaning; they are simply used to distinguish the filtrates obtained in different operational steps.

[0010] The beneficial effects of this invention are as follows: This invention utilizes propionic acid to directly acidify natural dolomite, and then adds calcium hydroxide to neutralize excess propionic acid to increase the total yield of calcium propionate, thus avoiding the waste of propionic acid. At the same time, calcium hydroxide precipitates magnesium ions, thereby separating calcium propionate and magnesium hydroxide products.

[0011] Compared with existing technologies, the raw material cost of this invention is lower, and there is no need to calcine natural dolomite. The process is simple, energy consumption is low, and the preparation conditions are green and mild, which has promising prospects for industrial application. Detailed Implementation

[0012] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention described above, but all such modifications and substitutions fall within the protection scope of the present invention.

[0013] In the following embodiments, The natural dolomite comes from Qingyang County, Anhui Province; Propionic acid was sourced from Sinopharm Chemical Reagent Co., Ltd., and its content was ≥99.8%. The calcium hydroxide is from Sinopharm Chemical Reagent Co., Ltd., and its content is ≥95%.

[0014] Example 1 Natural dolomite was ground into powder using an agate mortar and pestle. After thorough grinding, the powder was passed through a 100-mesh sieve to obtain dolomite powder. 3.00 g of dolomite powder, 6 ml of propionic acid, and 80 ml of deionized water were weighed out. The propionic acid was added to the deionized water and mixed thoroughly. The weighed dolomite powder was then added to the propionic acid solution, and the mixture was stirred with a constant-temperature magnetic stirrer at 80°C for 5 hours. After filtration, 3 g of calcium hydroxide was slowly added to the filtrate. After standing at 80°C for 0.5 hours, the mixture was filtered while still hot to obtain a calcium propionate solution and a magnesium hydroxide precipitate. The calcium propionate solution was dried at -60°C for 24 hours to obtain 4.14 g of solid calcium propionate, and the magnesium hydroxide precipitate was dried at 95°C for 12 hours to obtain 0.73 g of solid magnesium hydroxide.

[0015] Example 2 Natural dolomite was ground into powder using an agate mortar and pestle. After thorough grinding, the powder was passed through a 100-mesh sieve. 3.00 g of dolomite powder, 5 ml of propionic acid, and 75 ml of deionized water were weighed out. The propionic acid was added to the deionized water and mixed thoroughly. The weighed dolomite powder was then added to the propionic acid solution, and the mixture was stirred with a constant-temperature magnetic stirrer at 70°C for 5 hours. After filtration, 3.3 g of calcium hydroxide was slowly added to the filtrate. After standing at 60°C for 0.5 hours, the mixture was filtered while still hot to obtain a calcium propionate solution and a magnesium hydroxide precipitate. The calcium propionate solution was dried at -60°C for 24 hours to obtain 3.57 g of solid calcium propionate, and the magnesium hydroxide precipitate was dried at 95°C for 12 hours to obtain 0.71 g of solid magnesium hydroxide.

Claims

1. A process for the simultaneous production of calcium propionate and magnesium hydroxide from natural dolomite, characterized in that, The method comprises: The dolomite powder is added into the aqueous propionic acid solution, stirred at 10-90 ℃ for 1-6 h, then filtered, and the filtrate A is collected; the calcium hydroxide is added into the obtained filtrate A, and the mixture is allowed to stand at 10-90 ℃ for 10-50 min, then filtered, and the precipitate and the filtrate B are collected respectively; the precipitate is dried to obtain the magnesium hydroxide, and the filtrate B is dried at low temperature to obtain the calcium propionate.

2. The method for simultaneous preparation of calcium propionate and magnesium hydroxide from natural dolomite according to claim 1, characterized in that, The dolomite powder is added into the aqueous propionic acid solution, stirred at 45-75 ℃ for 2.5-5.5 h.

3. The method for simultaneous preparation of calcium propionate and magnesium hydroxide from natural dolomite as claimed in claim 1 wherein, The calcium hydroxide is added into the obtained filtrate A, and the mixture is allowed to stand at 50-80 ℃ for 10-50 min. ​ 4. The method for simultaneously producing calcium propionate and magnesium hydroxide from natural dolomite according to any one of claims 1 to 3, characterized in that, The molar ratio of the dolomite powder, the propionic acid and the calcium hydroxide is 1:1-1.8:1-1.

5.

5. The method for simultaneously producing calcium propionate and magnesium hydroxide from natural dolomite according to any one of claims 1 to 3, characterized in that, The volume fraction of the aqueous propionic acid solution is 5-10%.

6. The method for simultaneously producing calcium propionate and magnesium hydroxide from natural dolomite according to any one of claims 1 to 3, characterized in that, The liquid-solid ratio of the aqueous propionic acid solution and the dolomite powder is 10-30:1, mL / g.

7. The method for simultaneously producing calcium propionate and magnesium hydroxide from natural dolomite according to any one of claims 1 to 3, characterized in that, The drying conditions of the precipitate are 95 ℃, 12 h; and the drying conditions of the filtrate B at low temperature are -60 ℃, 24 h.