Preparation of mixed valence (Cr (IV) and Cr (VI)) chromate Ca5Cr3O12Method (2)
阅读说明：本技术 一种制备混合价态（Cr(Ⅳ)和Cr(Ⅵ)）铬酸盐Ca5Cr3O12的方法 (Preparation of mixed valence (Cr (IV) and Cr (VI)) chromate Ca5Cr3O12Method (2) ) 是由 毛林强 王嘉 胡林潮 张文艺 彭明国 于 2020-11-11 设计创作，主要内容包括：本发明提供了一种制备混合价态(Cr(Ⅳ)和Cr(Ⅵ))铬酸盐Ca-5Cr-3O-(12)的方法,制备流程为：将CaCrO-4与CaO混合均匀,在氧气与氮气的混合气氛(氧气分压为10kPa-15kPa)中进行高温煅烧,使混合物中的部分Cr(VI)还原为Cr(Ⅳ),从而生成Ca-5Cr-3O-(12),使用去离子水、有机酸(如稀醋酸或甲酸)对获得的产物进行洗涤后将滤渣加热、干燥,以便去除水分和其他杂质。本发明采用还原方法制备Ca-5Cr-3O-(12),工艺简单,所需原料均可购买获得或在实验室制备,成本较低,并且制备的Ca-5Cr-3O-(12)纯度可达80～97％,收率达到90％左右。(The invention provides a method for preparing mixed valence (Cr (IV) and Cr (VI)) chromate Ca 5 Cr 3 O 12 The preparation process comprises the following steps: adding CaCro 4 Mixing with CaO, calcining at high temperature in a mixed atmosphere of oxygen and nitrogen (oxygen partial pressure of 10kPa-15kPa) to reduce part of Cr (VI) in the mixture to Cr (IV), thereby generating Ca 5 Cr 3 O 12 The obtained product is washed with deionized water and organic acid (such as dilute acetic acid or formic acid), and the residue is heated and dried to remove water and other impurities. The invention adopts a reduction method to prepare Ca 5 Cr 3 O 12 Simple process, available raw materials or laboratory preparation, low cost and prepared Ca 5 Cr 3 O 12 The purity can reach 80-97%, and the yield can reach about 90%.)
1. Preparation of mixed valence (Cr (IV) and Cr (VI)) chromate Ca5Cr3O12The method comprises the following steps:
step one, CaO and CaCrO are mixed4Stirring and mixing the two raw materials, and mixing the mixed raw materials by using a ball mill to fully and uniformly mix the raw materials and the ball mill;
step two, after uniformly mixing the raw materials, calcining the raw materials in the mixed atmosphere of oxygen and nitrogen, wherein the calcining temperature needs to reach 1300-1400 ℃;
step three, cooling the product obtained after calcination in a mixed atmosphere, washing the cooled product with deionized water, washing with acid with the pH of 5-6, washing the filter residue with deionized water after repeated acid washing, and filtering;
step four, drying the filter residue obtained in the step three in a drying oven, and obtaining high-purity Ca after the drying is finished5Cr3O12And (5) producing the product.
2. Preparation of mixed-valence (Cr (IV) and Cr (VI)) chromates Ca according to claim 15Cr3O12The method of (2), characterized by: the raw materials used in the step one are CaO and CaCrO4The mass percentage of CaO in the raw material is 30-50%.
3. Preparation of mixed-valence (Cr (IV) and Cr (VI)) chromium according to claim 1Acid salt Ca5Cr3O12The method of (2), characterized by: in the second step, the oxygen partial pressure in the mixed atmosphere of oxygen and nitrogen is 10kPa-15 kPa; the calcination time is as follows: 3-6 h.
4. Preparation of mixed-valence (Cr (IV) and Cr (VI)) chromates Ca according to claim 15Cr3O12The method of (2), characterized by: the acid washing liquid used for purifying the calcined product in the third step is dilute acetic acid or formic acid; the solid-liquid mass ratio of the calcined product to the acid washing solution is 1: 15.
5. preparation of mixed-valence (Cr (IV) and Cr (VI)) chromates Ca according to claim 15Cr3O12The method of (2), characterized by: and step four, drying the obtained filter residue in an oven at the drying temperature: 200 ℃ and 300 ℃, and drying time: 5-8 h.
Technical Field
The invention relates to the field of preparation of chromium salt, in particular to a method for preparing mixed valence (Cr (IV) and Cr (VI)) chromate Ca5Cr3O12The method of (1).
Background
The chromium salt is one of important raw materials in chemical industry in China, wherein the Cr (III) salt and the Cr (VI) salt are most widely applied, the Cr (III) salt is widely applied to industries such as leather tanning, ceramic pigment, electroplating and the like, and the Cr (VI) salt is widely applied to industries such as electroplating, production of various chromium salts, manufacture of preservatives and the like. With the development of research on chromium-containing materials, the properties of some other Cr salts (such as Cr (IV) and Cr (V) salts) in valence state gradually attract the attention of researchers, and related research on the application of the Cr salts is favored. However, the properties of the chromium salt in the valence state between Cr (iii) and Cr (vi) are often not stable enough, and compared with the extensive research and literature of Cr (iii) and Cr (vi), the chromium salt in the intermediate valence state has less and less research data, which results in that the chromium salt cannot be produced in large quantities.
Ca known at present5Cr3O12The preparation method is that Cr is added2O3And CaO, and then the chromium salt is calcined at about 1300 ℃, and the chromium salt is generated by utilizing the characteristic that Cr (III) can be oxidized at high temperature under the action of alkaline earth metal. Firstly, the method needs to add a large amount of CaO, and the finished product contains a plurality of CaO impurities. And because the high-temperature oxidation method is adopted, the calcining temperature span is large, Cr (III) can be oxidized into other chromium salts with different valence states in the process, a mixture product with complex components is obtained, and Ca is removed from the product5Cr3O12Additionally contains Cr5O12、Ca3(CrO4)2、Ca5(CrO4)3O0.5And a plurality of chromium salts, wherein Ca5Cr3O12The content of (A) is less than 50%, and the yield is low. And the effect of removing some chromium salt contained in the product by washing with deionized water and organic acid is not ideal, and a large amount of residue still exists, so that Ca5Cr3O12The purity of the product is not satisfactory.
In addition, there are few documents and patent documents describing Ca5Cr3O12The preparation method of (1). In the invention, CaCrO is utilized4The high-temperature reduction reaction with CaO generates less impurities and Ca in the temperature range5Cr3O12High yield, and the excessive CaO and some trace impurities in the calcined product are separatedWashing the water and the organic acid to remove the water and the organic acid to finally obtain high-purity Ca5Cr3O12。
Disclosure of Invention
In view of the above-mentioned disadvantages of the prior art, the object of the present invention is to provide a method for preparing Ca with high purity and low impurity content5Cr3O12The method of (1).
In order to achieve the purpose, the invention adopts the following technical scheme:
preparation of mixed valence (Cr (IV) and Cr (VI)) chromate Ca5Cr3O12The method comprises the following steps:
step one, CaO and CaCrO are mixed4The two raw materials are stirred and mixed, wherein the weight percentage of CaO in the raw materials is 30-50%, the mixed raw materials are mixed by a ball mill, the two raw materials are fully and uniformly mixed, and the ball milling time is about 5-11 hours.
Step two, after the raw materials are uniformly mixed, calcining for 3-6 hours in the mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure in the mixed gas is 10-15 kPa), wherein the calcining temperature needs to reach 1300-1400 ℃.
Under the conditions of mixed atmosphere of oxygen partial pressure of 10kPa-15kPa and calcination temperature of 1300-1400 ℃, the generation of other chromium salt impurities can be avoided, and the Ca content is improved5Cr3O12Thereby being beneficial to the subsequent purification work and obtaining Ca with higher purity5Cr3O12The product of (1).
And step three, cooling in a mixed atmosphere of oxygen and nitrogen (oxygen partial pressure is 10-15 kPa) after calcining, washing the cooled product with deionized water, then washing with dilute acetic acid (or formic acid) with pH of 5-6, fully stirring and mixing the product and organic acid during washing, controlling the solid-liquid mass ratio of the product to the organic acid to be about 1:15, standing for 1-2 hours after stirring to separate the upper layer from the lower layer, and separating by using a suction filter to retain filter residues. And (3) pickling the filter residue once again according to the process, washing the filter residue with deionized water, and filtering.
Step four, obtaining the product in the step threeThe filter residue is dried in an oven at the temperature of 200-300 ℃ for 5-8 hours so as to remove redundant moisture, and high-purity Ca can be obtained after the drying is finished5Cr3O12And (5) producing the product.
The principle of the invention is to utilize CaCrO4Reducing a part of Cr (VI) into Cr (IV) by the reduction reaction with CaO in a high-temperature oxygen-deficient environment. In order to drive the reduction of Cr (VI) into Cr (IV), a mixed gas of nitrogen and oxygen with the oxygen partial pressure lower than that of air is adopted, and the oxygen partial pressure in the mixed gas is 10kPa-15 kPa. In order to provide a stable alkaline environment during the calcination and allow the CaCrO in the raw material mixture4The reaction is complete, and a large amount of CaO is added into the raw materials, so that a part of CaO remains after the high-temperature calcination, and most of the residual CaO can be removed by washing with dilute acetic acid (or formic acid). Trace calcium acetate or calcium formate generated in the acid washing process can be removed through washing with deionized water, and the generated Ca can be further purified5Cr3O12Detected, prepared Ca5Cr3O12The purity can reach 80-97%, and the yield can reach about 90%.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention provides Ca for preparing mixed valence (Cr (IV) and Cr (VI)) chromate5Cr3O12The method has the advantages that raw materials required by the reaction can be purchased or prepared in a laboratory, and the reaction process is convenient to control.
(2) The invention provides Ca for preparing mixed valence (Cr (IV) and Cr (VI)) chromate5Cr3O12The method of (1) is characterized in that the raw material generates less impurities in the high-temperature calcination temperature range, and the prepared Ca5Cr3O12The purity is high.
(3) Compared with the traditional Cr2O3The invention provides a CaCrO method4The CaO method adopts special oxidizing atmosphere and different reaction paths, and the obtained product has high yield, the purity can reach more than 90 percent, and the yield can reach about 90 percent.
Drawings
Figure 1 shows the hairPreparation of mixed-valence (Cr (IV) and Cr (VI)) chromates Ca5Cr3O12Process flow diagram of
Detailed Description
The invention is further described below with reference to examples, which are intended to illustrate the invention without further limiting it.
Example 1
CaO and CaCrO4The mixture is mixed by a ball mill, the mass percent of CaO in the raw materials is 40 percent, and the CaCrO4The mass percent of the raw materials is 60 percent, the mixed raw materials are calcined in a mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure is 10kPa) in an atmosphere box furnace at high temperature, the calcining temperature is 1300 ℃, and the calcining time is 5 hours. And cooling the calcined product in a mixed atmosphere, washing the product with deionized water, and then washing the cooled product with formic acid with the pH value of 5, wherein the solid-to-liquid ratio of the acid to the washed sample is 1: and 15, standing for 1h, separating by using a suction filter after the product is layered, pickling the filter residue once again according to the above process, washing the filter residue by using deionized water, and filtering. Drying the filter residue obtained after suction filtration in an oven for 5h, maintaining the drying temperature at 200 ℃, and obtaining the product which is Ca with the purity of 91 percent5Cr3O12Product, using raw material CaCrO4Calculation of Ca for reference5Cr3O12The target yield of (2), Ca was calculated from the actual amount of produced5Cr3O12The yield thereof was found to be 92%.
Example 2
CaO and CaCrO4And mixing the mixture by using a ball mill, wherein the mass percent of CaO is 30%, and calcining the mixed raw materials at the high temperature of 1400 ℃ for 6h in an atmosphere box furnace in the mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure is 15 kPa). And cooling the calcined product in a mixed atmosphere, washing the product with deionized water, and then washing the cooled product with formic acid with the pH value of 6, wherein the solid-to-liquid ratio of the acid to the washed sample is 1: standing for 1h, separating by using a suction filter after the product is layered, and allowing the filter residue to flow according to the aboveAnd after acid washing once again, washing the filter residue with deionized water and filtering. Drying the filter residue obtained after suction filtration in an oven for 5h, maintaining the drying temperature at 250 ℃, and obtaining a product which is Ca with the purity of 89%5Cr3O12Product, Ca5Cr3O12The yield thereof was found to be 92%.
Example 3
CaO and CaCrO4And mixing the mixture by using a ball mill, wherein the mass percent of CaO is 50%, and calcining the mixed raw materials at a high temperature of 1400 ℃ for 8h in an atmosphere box furnace in a mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure is 13 kPa). And cooling the calcined product in a mixed atmosphere, washing the product with deionized water, and then washing the cooled product with acetic acid with a pH value of 5, wherein the solid-to-liquid ratio of the acid to the washed sample is 1: and 20, standing for 1h, separating by using a suction filter after the product is layered, pickling the filter residue once again according to the above process, washing the filter residue by using deionized water, and filtering. Drying the filter residue obtained after suction filtration in an oven for 6h, maintaining the drying temperature at 300 ℃, and obtaining the product which is Ca with the purity of 86 percent5Cr3O12Product, Ca5Cr3O12The yield thereof was found to be 90%.
Comparative example 1
Comparative example 1 is different from example 1 in that: the calcination temperature was varied.
CaO and CaCrO4And mixing the mixture by using a ball mill, wherein the mass percent of CaO is 40%, and calcining the mixed raw materials at a high temperature of 800 ℃ for 5h in an atmosphere box furnace in a mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure is 10 kPa). And cooling the calcined product in a mixed atmosphere, washing the product with deionized water, and then washing the cooled product with formic acid with the pH value of 5, wherein the solid-to-liquid ratio of the acid to the washed sample is 1: and 15, standing for 1h, separating by using a suction filter after the product is layered, pickling the filter residue once again according to the above process, washing the filter residue by using deionized water, and filtering. Filtering to obtainDrying the filter residue in an oven for 5h, maintaining the drying temperature at 200 ℃, and obtaining a product Ca (OH)2、CaCrO4In admixture with other chromium salt impurities, containing little Ca5Cr3O12。
Comparative example 2
Comparative example 2 differs from example 1 in that: the mixed atmosphere is different.
CaO and CaCrO4And mixing the mixture by using a ball mill, wherein the mass percent of CaO is 40%, and calcining the mixed raw materials at 1300 ℃ for 5h in an air atmosphere by using a muffle furnace. And cooling the calcined product in an air atmosphere, washing the product with deionized water, and then washing the cooled product with formic acid with the pH value of 5, wherein the solid-to-liquid ratio of the acid to the washed sample is 1: and 15, standing for 1h, separating by using a suction filter after the product is layered, pickling the filter residue once again according to the above process, washing the filter residue by using deionized water, and filtering. Drying the filter residue obtained after suction filtration in an oven for 5h, maintaining the drying temperature at 200 ℃, and cleaning to obtain Ca5Cr3O12、Cr5O12、Ca5(CrO4)3O0.5Mixture of several chromium salts, Ca5Cr3O12The purity of (A) is below 70%.
Comparative example 3
Comparative example 3 differs from example 1 in that: the mixed atmosphere is different.
CaO and CaCrO4And mixing the mixture by using a ball mill, wherein the mass percent of CaO is 40%, and calcining the mixed raw materials at the high temperature of 1300 ℃ for 5h in an atmosphere box furnace in the mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure is 30 kPa). And cooling the calcined product in a mixed atmosphere, washing the product with deionized water, and then washing the cooled product with formic acid with the pH value of 5, wherein the solid-to-liquid ratio of the acid to the washed sample is 1:15, standing for 1h until the product is layered, separating by using a suction filter, and pickling the filter residue once again according to the above processThen, the residue was washed with deionized water and filtered. Drying the filter residue obtained after suction filtration in an oven for 5h, maintaining the drying temperature at 200 ℃, and cleaning to obtain Ca as a product5Cr3O12、Cr5O12、Ca5(CrO4)3O0.5Mixture of several chromium salts, Ca5Cr3O12The purity of (D) is less than 65%.
Comparative example 4
Comparative example 4 is different from example 1 in that: the CaO mixing amount is different.
CaO and CaCrO4And mixing the mixture by using a ball mill, wherein the mass percent of CaO is 10%, and calcining the mixed raw materials at the high temperature of 1300 ℃ for 5h in an atmosphere box furnace in the mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure is 10 kPa). And cooling the calcined product in a mixed atmosphere, washing the product with deionized water, and then washing the cooled product with formic acid with the pH value of 5, wherein the solid-to-liquid ratio of the acid to the washed sample is 1: and 15, standing for 1h, separating by using a suction filter after the product is layered, pickling the filter residue once again according to the above process, washing the filter residue by using deionized water, and filtering. Drying the filter residue obtained after suction filtration in an oven for 5h, maintaining the drying temperature at 200 ℃, and cleaning to obtain a product mainly containing CaCrO4、Cr5O12、Ca5Cr3O12Mixture of (2), Ca5Cr3O12The purity of (A) is below 50%.
Comparative example 5
Comparative example 5 differs from example 1 in that: the product is not washed and purified.
CaO and CaCrO4And mixing the mixture by using a ball mill, wherein the mass percent of CaO is 40%, calcining the mixed raw materials at high temperature in an atmosphere box furnace in a mixed atmosphere of oxygen and nitrogen (the oxygen partial pressure is 10kPa), the calcining temperature is 1300 ℃, the calcining time is 5h, and cooling the calcined product in the mixed atmosphere. The products obtained by detection except Ca5Cr3O12Besides, it also contains a large amount of CaO and a small amount of CaCro4Equal chromium salt impurity, Ca5Cr3O12The purity of (A) is below 70%.
The applicant has claimed that: the above description is only for the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the protection scope and the disclosure of the present invention.