Preparation and Application of Potassium Carbonate_Industrial Additives

Background and overview^[1]

Potassium carbonate is also called potassium alkali and alkali sand, and impurities are called potassium alkali, bead ash, etc. Colorless crystals or white particles. Due to the hydrolysis of carbonate, the aqueous solution becomes alkaline and insoluble in ethanol and ether. Deliquescent. Potassium carbonate has high thermal stability and does not decompose at 1000°C. Cooling its saturated aqueous solution can precipitate the glassy crystal hydrate K₂CO₃·3H2O, with a relative density of 2.043. It loses crystal water at 100°C and decomposes when exposed to acid. Carbon dioxide is released. Potassium carbonate is mainly used in the glass industry, and can also be used as analytical reagents, fluxes, potassium fertilizers, and raw materials for the preparation of other potassium compounds. Potassium carbonate is an important basic inorganic chemical raw material. It is mainly used in the production of glass, welding rods, printing and dyeing of vat dyes and whitening of ice dyes, industrial desulfurization of nitrogen fertilizers, removal of hydrogen sulfide and carbon dioxide from industrial gases, fire extinguishing agents, and also It has important uses in industrial fields such as ink, explosives, electroplating, tanning, medicine, ceramics, building materials, and crystal. In industry, potassium carbonate is prepared by passing carbon dioxide into potassium hydroxide solution.

Preparation^[2]

The reported production processes for potassium carbonate mainly include plant ash method, Lublan method, organic amine method, Engel salt method, nickel ammonia complex method, ion exchange method and ion membrane-fluidized bed method. Among them, the plant ash method and the Lublan method have been eliminated, and the organic amine method, Engel salt method and nickel ammonia complex method are still in the research and development stage, and the technology maturity is far from enough. At present, the main methods for producing potassium carbonate in domestic and foreign industries are ion exchange method and ion membrane-fluidized bed method. Under the current market conditions, when these two methods are used to produce potassium carbonate, the price of raw material potassium chloride accounts for more than 50% of the total cost of potassium carbonate. Therefore, the development of the potassium carbonate industry is completely controlled by the upstream potassium chloride market. Finding cheap potassium-containing resources to produce potassium carbonate is of great significance to the sustainable development of the entire potassium carbonate industry and extended downstream industries. Insoluble potassium resources represented by potassium feldspar are extremely abundant and widely distributed. They have always been considered the most important cheap alternative raw material for the production of potassium salts. Technological methods for producing potassium carbonate using insoluble potassium resources as raw materials have been reported at home and abroad. There are three main methods: acid method, soda ash sintering method and limestone sintering method.

The limestone sintering method is a process used by the former Soviet Union to comprehensively produce alumina, sodium carbonate, potassium carbonate and cement using nepheline raw materials. This method is the only industrialized technology for the development and utilization of insoluble potassium resources at home and abroad. The process of this method is that the ore amino resin raw materials and limestone ingredients are sintered at high temperature to generate clinker whose main phases are calcium orthosilicate and sodium (potassium aluminate); dilute sodium hydroxide solution is used to dissolve the clinker Sodium aluminate (potassium) and calcium orthosilicate are separated as filter residues for the production of cement; sodium aluminate (potassium) solution is acidified by CO2, and aluminum hydroxide is precipitated to produce alumina; sodium carbonate (potassium) solution is concentrated by evaporation , sodium carbonate and potassium carbonate are crystallized from saturated polyester, and the purity of potassium carbonate can reach up to 98.5%.

CN201210557765.6 provides a method for preparing potassium carbonate using potassium feldspar powder, which includes the following steps:

(1) Chemical beneficiation: Mix potassium feldspar powder and alkali mother liquor at the ratio of 1kg:1.5~7.5L to make raw ore slurry. The raw ore slurry reacts at 200~300℃ for 5~240min, and the slurry is obtained after cooling. , filter to obtain desilica liquid and desilica concentrate; add lime milk to the desilica liquid, causticize the reaction at 70~90℃ for 2 hours, filter and wash the filtrate obtained by evaporation and concentration to a predetermined concentration, that is Can be recycled as alkali mother liquor;

The alkali mother liquor is a mixed liquor containing KOH and NaOH;

(2) Ingredients sintering: Desilica concentrate and limestone are mixed and ground into raw meal at a ratio of 1kg:0.5~2kg. The raw meal reacts at a temperature of 1200~1350℃ for 30~180min, and then sintered clinker is obtained after cooling;

(3) Clinker dissolution: The sintered clinker is crushed and ground to obtain sintered clinker powder. The clinker powder and the dissolution liquid are mixed at a ratio of 1kg:2~5L, and reacted at a temperature of 60~95°C for 15~ 120min, filter after the reaction is completed, and obtain the crude dissolution liquid and calcium silicate slag respectively. Calcium silicate slag can be used as a raw material for the production of cement and new building materials;

The dissolution solution is KOH and K₂CO₃ mixture;

(4) Carbon decomposition: Acidification gas CO₂ is introduced into the crude dissolution liquid. During the reaction process, sampling points are designed to monitor changes in the pH value of the solution, and the pH value of the solution is monitored every 30 minutes. Change, start when the pH value of the solution is less than 10, take a sample every 15 minutes, filter the precipitate and detect the content of Al₂O₃ and SiO2 in the solution; when the Al in the solution The reaction ends when the sum of the contents of ₂O₃ and SiO₂ is less than 5g/L, and then filtered to obtain crude potassium carbonate liquid and aluminum hydroxide. ; Aluminum hydroxide can produce refractory materials or enter the Bayer process alumina production system to produce metallurgical grade alumina; the acidified gas refers to a gas with a CO₂ concentration greater than 10%;

(5) Preparation of potassium carbonate: Evaporate and concentrate the crude potassium carbonate liquid once and send it to the primary carbonation tower. Add potassium permanganate solution, introduce acidification gas for primary carbonation to precipitate impurities, and filter to obtain carbonic acid. Potassium refined liquid; potassium carbonate refined liquid is sent to the secondary carbonation tower after secondary evaporation and concentration, and acidification gas is introduced for secondary carbonation to crystallize potassium bicarbonate from the solution. Centrifuge to obtain the potassium bicarbonate. The crystal is calcined at 270~300℃ to obtain the product potassium carbonate.

Apply ^[3]

Rare earth complexes, as a kind of luminescent material, are widely used in fields such as luminescent displays, fluorescent probes, and anti-counterfeiting due to their characteristics of narrow emission peaks, high quantum efficiency, and the fact that the emission peak position does not move with changes in ligands. . CN201510358890.8 uses potassium carbonate of a specific particle size as the core material, and coats the surface of the potassium carbonate with a rare earth complex as a shell material to form a core-shell fluorescent material. There is no second ligand in the core-shell fluorescent material. Its fluorescence emission performance is excellent. At the same time, using cheap potassium carbonate as the core material also reduces the cost of fluorescent materials. When preparing the core-shell composite luminescent material, rare earth binary complexes are difficult to precipitate in the system using conventional methods. The present invention is completed by coating the surface of nanometer potassium carbonate to the greatest extent and effectively precipitating it. The preparation method includes the following steps:

(1) Crush potassium carbonate to obtain nano potassium carbonate;

(2) Add the nanopotassium carbonate obtained in step 1 to the polar organic solvent and disperse it;

(3) Add rare earth salt and ligand, stir and react;

(4) Filter and optionally dry to obtain potassium carbonate-based fluorescent material.

Main reference materials

[1] Encyclopedia of Chinese Middle School Teaching·Chemistry Volume

[2] CN201210557765.6 A method of preparing potassium carbonate using potassium feldspar powder

[3] CN201510358890.8 Potassium carbonate-based fluorescent material and preparation method thereof