2019年3月28日星期四

Cesium Tungstate, Small Figure Large Application

Cesium tungstate is a new type of heat insulation material.

At present, some famous coating companies in Japan, Germany and the United States all develop the transparent coating of cesium tungstate, which has a great market prospect.

The thermal insulation properties of cesium tungstate reflect its near infrared absorption properties, the results show that cesium tungstate not only has a strong absorption property in the near infrared region (800~1100 nm), at the same time, the visible light region (wavelength 380~780 nm) has a strong transmittance, and has a strong shielding property in the ultraviolet region (200~380 nm). Compared with similar chemicals, cesium tungstate has the best absorption performance. Therefore, it is used to make insulation glass, heat insulation automobile film and heat insulation coating.

cesium tungstate heat protecting glass image

Similar to other tungstate product, method of preparation of nanometer cesium tungstate with chemical vapor transport method, thermal plasma method, solid-state reaction, hydrothermal / solvothermal process, in recent years also use low-temperature synthesis method to produce. However, there is no method to meet the requirements of perfection, so the manufacturing cost of cesium tungstate is higher.

But expensive prices do not prevent people from using cesium tungstate as a standard for improving living conditions. Especially in recent years, the hottest real estate industry, as a kind of green energy saving and environmental protection material, the development of transparent heat insulation is out of control. Many new residential concept, special glass will require the use of transparent insulation material. Commonly used transparent heat insulation materials include tin doped indium oxide (ITO), antimony doped tin oxide (ATO), aluminum doped zinc oxide (AZO) and cesium tungstate, the above materials have a common point, that is "expensive", but cesium tungstate is the cheapest and most powerful of its kind, so who does not choose it?

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How Cesium Phosphotungstic Catalyzed Swida Wilsoniana Fruit Oil

Biodiesel refers to oil crops, oil plants and algae and other aquatic plants oil and animal fats, waste food oil as raw oil by transesterification process made of methyl or ethyl ester of fuel.

It is environmentally friendly and clean energy. Swida wilsoniana fruit oil as raw material and diesel combustion performance similar to bio diesel, is a safe, clean biomass fuel oil. 

Method for producing bio diesel are generally homogeneous alkaline and acid catalysis method, homogeneous acid process can produce a large amount of acidic waste water, no environmental significance, homogeneous alkaline law is prone to saponification reaction, which leads to difficult separation of bio diesel products. So, in addition to the above two methods, is there a better solution?

After repeated attempts, Li Nian, a scholar at the Central South University, found that cesium phosphotungstic could be a catalyst for this problem and has done a test for it. Cesium phosphotungstic is one of tungsten heteropoly acids and is often used as an industrial petrochemical catalyst.

swida wilsoniana image

During the experiment, he took a certain amount of swida wilsoniana fruit oil and cesium phosphotungstic catalyst, added to the drying, and equipped with magnetic stirring, a thermometer and condenser tube in three flasks, when the oil phase temperature rises to the set reaction temperature, a certain amount of methanol and cosolvent (THF) are added to prepare the esterification reaction at constant temperature. After the reaction is completed, the solid catalyst is removed by centrifugal separation, and the liquid is placed in a separating funnel to be placed statically, and the product is automatically layered: The upper layer is bio diesel, and the lower layer is glycerin and unreacted methanol.

The results show that the solid cesium phosphotungstic has stronger catalytic activity than the traditional acid method, as a solid catalyst, cesium phosphotungstic can catalyze the preparation of biodiesel. It has the advantages of high efficiency, green and environmental protection, moreover, the temperature of ester exchange reaction is not too high, so it is more suitable for industrialization promotion of biodiesel.

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Catalytic Synthesis of Levulinic Acid by Phosphotungstic Acid

Levulinic acid, also known as fructose, is the basic raw material for the synthesis of various light chemical products, and has high activity.

High value-added products can be produced by chemical reactions such as esterification, halogenation, hydrogenation, oxidative dehydrogenation and condensation. They are widely used in organic synthesis, industry, agriculture and pharmaceutical industry.

Although levulinic acid is good, the preparation method is relatively troublesome. There are many problems in the preparation of traditional acid process, such as corrosion of equipment, serious pollution, complex treatment process and difficult separation of products. To solve these problems, scientists are trying to find the appropriate solid acid catalyst to replace the traditional acid catalyst. However, a variety of solid acid catalysts have been tried with little success until the appearance of phosphotungstic acid.

levulinic acid preparation image

Phosphotungstic acid is a kind of heteropoly acid. Because of its excellent catalytic properties and environmental friendliness, it has attracted more and more attention of researchers. It is a new environmentally friendly green catalyst, phosphorus salts include phosphotungstic acid, silver, cesium phosphotungstic, zinc tungstate and copper tungstate. They are generally Keggin structures.

Some scholars used silver tungstate to catalyze the conversion of levulinic acid to glucose, in the process, a certain amount of tungstate catalyst was added into glucose solution and placed in a high pressure reactor at 550 °C. The rotational speed was 400r/min, and the reaction temperature was 180 °C for 2h, after the reaction is finished, remove the reactor and cool down to room temperature. The reaction liquid is filtered by 0.22 m microporous filter membrane to form levulinic acid.

The experimental results show that the synthesis of levulinic acid with phosphotungstic acid catalyst is stronger than other solid catalysts, and it is also non-toxic and environmentally friendly, at the same time, after using the silver can be washed, recycled, reuse, green chemistry catalyst is significance to promote.

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Why Does Tungstate Glow?

Tungstate phosphor is a typical self activated luminescent material.

Without the addition of other activated ions, they can produce high efficiency luminescence under the excitation of UV, X ray and CR. Tungstate matrix has the characteristics of stable luminescence spectrum, wide spectrum of luminescence spectrum and large area of visible light. The higher the purity, the greater the brightness of the luminescence, then, why does tungstate glow?

tungstate LED image

The reason why tungstate will emit light, its roots from tungstate chromium ions, tungstate generally have wolframite structure and scheelite structure, among them, among them, tungstate crystal scheelite structure with a higher density, high-energy particles and high-energy radiation has a high ability to stop, is a good scintillator or X-ray emitter. At low temperature (liquid nitrogen or helium temperature) by ultraviolet short wavelength excitation, will emit green or blue light, it is the main material for the manufacture of high performance nuclear radiation detector and X ray machine.

Some scholars have studied the luminescence principle of tungstic acid by using instruments. It is found that the luminescence spectrum of tungstate is very stable, and the intrinsic luminescence spectrum is very wide and occupies most of the visible region, the cations in tungstate strongly affect the position of the emission band, and with the increase of atomic number of the cation, the peak shift of the emission band is blue, and the bandwidth is 250 - 300nm. The brightness of tungstate with compound purity increases. Some of the tungstate itself does not emit light, but when some rare earth elements are doped, the luminescent properties are activated and emit a special property of light.

The luminescence properties of tungstate, people not only to create a sophisticated medical equipment to save lives, but also produce a colorful LED fluorescent light of life. In addition, the light emitting property of tungstate can degrade many industrial wastewater, and it is also a good assistant to protect the earth and maintain the ecology.

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2019年3月12日星期二

Corrosion Inhibition of Sodium Tungstate Inhibitor On Carbon Steel

In recent years, in order to save fresh water resources and reduce the cost, some of the coastal chemical, metallurgy, electric power and petrochemical enterprises began to use seawater as a type of industrial circulating cooling water.

seawater cooling system image

Although this practice has many advantages, in the sea cl- content is high, easy to produce metal corrosion, metal corrosion is one of the most important destructive factors, which can cause corrosion and perforation of equipment and pipes, cause serious corrosion, and cause enormous economic losses and social harm.

In order to reduce the probability of metal corrosion, it is a simple and effective anti-corrosion method to add inhibitors to circulating cooling water. Only common chromate, nitrite, phosphate and other corrosive agents are toxic preparations, excessive use is tantamount to quenching thirst with poison, research and development of low toxicity, non-toxic and effective corrosion inhibitors have a greater significance.

Sodium tungstate inhibitor is one of inorganic inhibitors. Because of its low toxicity, no harm to environment, human body and crops, and no microorganism breeding, it is also used as metal corrosion inhibitor, however, sodium tungstate is good, but the price is not approachable. Moreover, various industrial applications show that the single use of sodium tungstate inhibitors is not only of large amount, but also of limited effect. Therefore, more scholars have developed many kinds of sodium tungstate composite inhibitors based on sodium tungstate.

Some scholars combine sodium tungstate, twelve sodium benzene sulfonate and triethanolamine, three yuan compound release agent of sodium tungstate was prepared, and a comparative test of carbon steel was carried out in simulated seawater environment, the results show that the surface corrosion of carbon steel sheet without corrosion inhibitor is serious and uneven; The corrosion resistant carbon steel sheet with three yuan of sodium tungstate is intact, the surface is clear and there is no trace of corrosion, and the inhibition efficiency reaches 75%, it is also emphasized that the sodium tungstate three yuan corrosion inhibitor has the advantages of less dosage, low cost and high corrosion inhibition rate, and can meet the requirements of industrial universal use.

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Sodium Tungstate Compound Corrosion Inhibitor Copper Protection

Sodium tungstate is an inorganic inhibitor. It has many advantages, such as low toxicity, no harm to environment, human body and crops, and no microorganism breeding.

submarine fiber image

However, sodium tungstate has its unavoidable defects. First of all, the effect of single sodium tungstate is limited, and it needs to be used to enhance the effect, at the same time, sodium tungstate is more expensive and impractical to use. Therefore, more enterprises are using sodium tungstate and cheaper chemicals to make sodium tungstate composite corrosion inhibitor to realize the function of protecting metal.

Polyaspartic acid (PASP) is a newly found environmental friendly water treatment agent. It has excellent scale inhibition, dispersion and good biodegradability, after polyaspartic acid used efficiently, stably microorganisms, fungi degradation of the final product harmless to the environment, is a very desirable water treating agent.

What is the effect of combining sodium tungstate with polyaspartic acid? Some scholars have combined these two methods to study the corrosion inhibition of copper in simulated seawater environment. In marine environment, when the total concentration of inhibitor of 7mg/L, PASP and Na2WO4 complex for copper have inhibition effect, but the effect is weak, however, synergistic effect between sodium tungstate and polyaspartic acid resulted in a good effect on corrosion inhibition, this is because of the weak oxidation of sodium tungstate react with copper, but the film formed by sodium tungstate has defects and pores, the polyaspartic acid, which is just salt with two valence copper ion or cuprous ion in the solution, plays a role in filling pores and repairing defects.

The research shows that the compound inhibitor of sodium tungstate and polyaspartic acid has good corrosion protection effect on copper. It not only improves the efficiency, but also reduces the cost, and has a very broad prospects for promotion.

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Photocatalytic Degradation of Methylene Blue by Sodium Tungstate

Methylene blue is an aromatic heterocyclic compound, used as a chemical indicator, dye, biological dye and drug use, mostly dyes, the methylene blue aqueous solution is blue in an oxidizing environment.

methylene blue wastewater treatment plant image

In industrial applications, methylene blue also produces wastewater which is difficult to degrade. The methylene blue wastewater discharged into rivers, lakes and seas is also a toxic substance.

Then, how to degrade methylene blue wastewater? In theory, the key and core of difficult wastewater treatment technology is the removal of refractory and insoluble matter in wastewater, that is, how to convert non biodegradable soluble chemicals into biochemical substances. In recent years, with the development of photocatalytic technology, more and more photocatalysts have been developed. Sodium tungstate is one of the most widely used photocatalysts, so is sodium tungstate also suitable for the degradation of methylene blue wastewater?

Sodium tungstate is an excellent photocatalyst. Because of its low toxicity, friendly environment and stable photocatalytic properties, sodium tungstate is widely used. Some scholars used sodium tungstate as the main catalyst of the photocatalyst, and the total amount of 30% hydrogen peroxide H2O2 was used to degrade methylene blue, the results showed that the decolorization rate of methylene blue wastewater was 99.8% and almost completely degraded by the combination of sodium tungstate and hydrogen peroxide at the temperature of 60 °C with the ratio of 7:3, the effect of hydrogen peroxide is 30% higher than that of hydrogen peroxide alone, which shows that sodium tungstate has very good photocatalytic activity for methylene blue.

With the rapid development of industry in China, the cost of environmental protection is higher and higher. It is always troublesome to treat wastewater with high difficulty, but with the increasing popularity of the concept of photocatalysis, photocatalyst tungstate slowly make it not trouble, sodium tungstate will also get more and more applications, it has great prospects.

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How Sodium Tungstate Improves The Nannochloropsis Oculata Diesel Production

Nannochloropsis oculata belongs to the category of the true focus algae class, is considered to be an ideal raw material for most potential, to achieve sustainable supply of biodiesel refining.

nannochloropsis image

At present there are about 6 species have been set, namely Cadiz Nannochloropsis oculata, particles of Nannochloropsis oculata and lakes Nannochloropsis oculata, marine Nannochloropsis oculata, focus of Nannochloropsis oculata and saline Nannochloropsis oculata.

The research showed that the key of Nannochloropsis oculata oil is the fatty acid composition, which is closely associated with environmental conditions, nitrogen is a large number of elements needed for microalgae growth, and different nitrogen sources and concentrations have significant effects on the composition of microalgae fatty acids.

Nitrate nitrogen is the most important form of nitrogen in sea water. As the nitrogen fertilizer used in surface plants, nitrate reductase is an important regulating enzyme and a speed limiting enzyme in the process of nitrogen metabolism, it is an important factor affecting plant photosynthesis metabolism. Sodium tungstate Na2WO4 can reduce the activity of nitrate reductase, which is an inhibitor of nitrate reductase.

Why should sodium tungstate be used as an inhibitor of nitrate reductase? As a matter of fact, the main purpose of cultivating microalgae is to produce biodiesel, studies have shown that most of the algae in the nutritional stress conditions can accumulate higher levels of fat, oil is equally consumed in the process of growth, on the one hand, the amount of treatment is increased, on the other hand, the difficulty of making biodiesel is also increased, but correspondingly, the lack of nitrogen absorption can cause malnutrition and decrease the growth rate of algae. Therefore, it is necessary to find a balance between nitrogen metabolism, sodium tungstate is the key factor to achieve the balance of metabolism.

Industrial practice has shown that sodium tungstate is used as a regulator, sodium tungstate replaces the molybdenum reductase coenzyme factor in nitrate in the metabolic process (promoting the absorption of the active factor), thereby controlling or reducing the activity of nitrate reductase, and ultimately inhibiting the absorption of nitrate nitrogen by plants, after the control of nitrogen absorption, the growth rate of microalgae slowed down, but the accumulation of medium and short chain fatty acids began to accelerate.

Sodium tungstate is an environmental regulator, low toxicity, basically do not have to worry about environmental pollution, and less consumption can achieve the effect of nitrogen limit, greatly reduces the production cost of microalgae biodiesel. Nannochloropsis oculata production assistant agent has a great prospect of industry.

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