What is the function of basic cobalt carbonate_Industrial additive

What is the function of basic cobalt carbonate [Overview]

Basic cobalt carbonate [2CoCO₃ calcium carbonate · 3Co( OH) ₂ ·H₂O] is a purple-colored Red crystal or powder. Toxic, irritating to eyes, respiratory system and skin, almost insoluble in water and ammonia, soluble in acid, incompatible with cold concentrated nitric acid and concentrated hydrochloric acid, it begins to decompose when heated to ℃ and releases carbon dioxide. It is widely used in catalysts and raw materials for making cobalt salts, colorants in the ceramic industry, electrochemistry, catalysts, magnetic materials and other fields.

Basic cobalt carbonate is an emerging fine chemical product. It is widely used as a catalyst in the petrochemical industry, a raw material for electroplating and other industries, and its application fields are constantly expanding. , the demand is increasing year by year. As a raw material for cobalt-based catalysts used in petroleum processing, it is of great significance in reducing PM2.5 pollution. For a long time in the past, cobalt nitrate has been the raw material for cobalt-based catalysts used in petroleum processing, making a huge contribution to the development of the petroleum industry. However, when cobalt nitrate is produced, cobalt cake (or cobalt block) is reacted with concentrated nitric acid, which produces a large amount of nitrogen oxide pollution during the production process; cobalt nitrate also produces a large amount of nitrogen oxides during the production of catalysts due to the presence of nitrate radicals. Cause a series of environmental problems. With the strengthening of environmental awareness of the entire society, cobalt nitrate will gradually withdraw from the stage of history. The preparation of basic cobalt carbonate does not require nitric acid. At the same time, since there are no nitrate radicals in the product, no nitrogen oxides are generated during the catalyst preparation process. It is a new environmentally friendly catalyst for petroleum processing.

What is the function of basic cobalt carbonate [Physical and chemical properties] [3]

In the air atmosphere, the thermal decomposition process of basic cobalt carbonate is divided into two stages: the removal of crystal water and the decomposition of anhydrous salt. The final decomposition product is Co₃O₄. At 493~625 K, it is the decomposition process of basic cobalt carbonate anhydrous salt. The mass loss rate of this process is 29.5%, which is consistent with the theoretical mass loss rate. The non-isothermal multiple scan rate method and the model function method were used to calculate the kinetic parameters of the second decomposition stage of the thermal decomposition process of basic cobalt carbonate. The activation energy E is 106.139~144.537 kJ/mol, lg A is 9.396~11.868, and the reaction mechanism nucleation and growth model, the mechanism function is: f(α)=5/2(1−α)[−ln(1−α)]3/5; g(α)= [−ln(1−α) )]2/5.

What is the function of basic cobalt carbonate [Preparation method]

1. Reaction mechanism

Using industrial grade cobalt sulfate and sodium bicarbonate as raw materials, the target product is obtained after neutralization reaction. The reaction equation is as follows: CoSO₄ +NaHCO₃→ 2CoCO₃·3Co( OH) ₂·H₂ O +Na₂SO₄

2. Process improvement experiment

2.1 The influence of the synthesis process and the pH value at the end point on the product. After repeated experiments, a sodium bicarbonate solution with a specific gravity of 1.06 was used as a fixed parameter, and the pH value during the process and the end point pH value were used as variables. The data obtained As shown in Table 1.

Through the above experimental data analysis, when the process parameters are synthesis process pH = 6 ~ 7, synthesis end point pH = 7. 5 ~ 8. 0, and the raw material cobalt sulfate specific gravity is 1. 24, the impurities (especially (Na+) content is the lowest, and the content of cobalt ions in the supernatant liquid in the reactor is also the lowest. The operation of an enterprise is a process of maximizing profits. The production process of products is based on meeting customer requirements. /p>

Improve production efficiency and reduce production costs as much as possible to maximize profits. From the perspective of maximizing the profit of the factory, reaction equipment with the same volume and raw materials with a specific gravity will produce a higher volume of finished products per unit time, so the appropriate process parameters are: synthesis process pH = 6 ~ 7, synthesis end point pH = 7. 5 ~ 8. 0, the specific gravity of raw material cobalt sulfate is 1. 27.

2. 2 Influence of supersaturation state

Through experiments, it was found that the synthesis rate of sodium bicarbonate and cobalt sulfate is closely related to the quality of the final product. The speed of the synthesis reaction is directly reflected in the thickness of the crystal form. The process of product nucleation occurs in the supersaturated state of the product solution. If the nucleation rate is faster than the production rate, the final crystal form will be finer. When the production rate is greater than the nucleation rate, the final crystal form will be finer. Thick,

In industrial crystallizers, most crystal nuclei are generated due to contact nucleation. In this case, the nucleation speed is a function of stirring intensity, suspension density and supersaturation: B = KN’WiMTj ( △cn ) in the formula: W————stirring intensity (stirring edge rate, energy input rate), rpmMT——suspended density, kg/m3

Therefore, in the actual production process of the factory, the suspension density is generally adjusted by adding the amount of seed crystals to the product, and the stirring intensity is controlled, and anhydrous lithium tetraborate is used to control the nucleation rate of the product. According to experiments, when the stirring rate is 25 rpm, the relationship between the amount of seed crystal added and the content of impurities (especially Na+) in the final product is shown in Figure 1.

The data in Figure 1 shows that the addition of seed crystals will have an important impact on the nucleation of supersaturated solutions.��. This method has been widely used in the industry.

What is the role of basic cobalt carbonate [Application and development prospects]

Compared with traditional cobalt nitrate, basic cobalt carbonate has no nitrogen oxide pollution, but the price is about 10% higher than cobalt nitrate. However, with the strengthening of the environmental awareness of the entire society, environmental factors have received more and more attention from everyone. In today’s increasingly serious smog, the impact of environmental factors will definitely exceed the price factor. It is expected that basic cobalt carbonate will gradually replace traditional petrochemical catalysts. Cobalt nitrate has become the mainstream in the market.

What is the function of basic cobalt carbonate [Reference materials]

[1]Wu Qingsheng. Improvement of production process of basic cobalt carbonate[J]. Guangzhou Chemical Industry, 2017, 45(12):171-172+182.

[2]Hu Changwen, Liu Yuansheng, Gong Chuangzhou. Determination of parameters for basic cobalt carbonate industry standards [J]. Fine and Specialty Chemicals, 2015, 23(11):23-25.

[3] Liu Bingguo, Peng Jinhui, Zhang Libo, Zhang Zebiao, Guo Shenghui, Zhang Shimin. Non-isothermal thermal decomposition kinetics of basic cobalt carbonate [J]. Journal of Central South University (Natural Science Edition), 2011, 42(02): 356-360.

[4]Hu Changwen, Liu Yuansheng. Review of production technology of basic cobalt carbonate for petroleum refining catalysts[J]. Fine and Specialty Chemicals, 2015, 23(12):37-38.