2019年10月23日星期三

Monoalkyl Phosphate Preparation by Cesium Phosphotungstate

Monoalkyl phosphate is an important surfactant, widely used in chemical fiber, textile, leather, plastics, paper making and cosmetics. 

Monoalkyl phosphate usually synthesized by the esterification of phosphoric acid with aliphatic alcohols by esterification. The commonly used phosphorus agents are three oxychloride (POCl3) and phosphoric acid.

When phosphorus oxychloride is used as an agent for HCL, it is easy to cause environmental pollution, when phosphoric acid is used as a phosphate agent, although it is environmentally friendly, it is difficult to synthesize monoester, diester and three ester because of the low activity of phosphoric acid. Is there a way to improve the activity of phosphoric acid to help balance the benefits of the environment?

monoalkyl phosphate preparation image

Cesium phosphotungstate is a kind of heteropoly acid. It is a new type of multifunctional catalyst. It has not only oxidation reduction property, but also high catalytic activity and good stability, it can be used for homogeneous and heterogeneous reactions, and even can be used as phase transfer catalyst, the most important thing is that it is pollution-free to the environment. Some scholars have studied the synthesis of mono twelve alkyl phosphate by the direct esterification of lauryl alcohol and 85% phosphoric acid with cesium phosphotungstate as catalyst. Through investigation, we found that cesium phosphotungstate in the reaction process showed very high activity during the catalytic reaction, under the catalytic action of cesium phosphotungstate, the selectivity of MAP is 90% with the attraction between lauryl alcohol and phosphoric acid, a single twelve alkyl phosphate has been successfully synthesized. The effect is not weaker than three phosphorus oxychloride (POCl3). The most important is that it is safer and more environmentally friendly with phosphoric acid.

Over the years, cesium phosphotungstate has been recognized more and more by virtue of its excellent catalytic performance and non-toxic and harmless strength. So, when you're not satisfied with the catalytic effect of a certain chemical, you might be able to try cesium phosphotungstate.

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The PK Between Tungsten Trioxide and Titanium Dioxide Photocatalytic Performance

Photocatalysis is a photochemical reaction in the presence of a catalyst, it is a new science and technology.

Common photocatalysts include metal oxides (TiO2, ZnO, Fe2O3, Bi2O3, WO3) and metal sulfides (CdS, MoS2, MoSe2). Titanium dioxide TiO2 is the most white thing in the world, 1 grams of titanium dioxide can paint more than 450 square centimeter area to white. So it's the best paint for making white oil paint. The most well-known is that semiconductor photocatalysis performance of TiO2. TiO2 photocatalysis is widely used because of its high activity, photochemical stability, non-toxic and cheap.

Tungsten trioxide TiO2 is a kind of tungsten compounds that are widely used, It can be used not only for hard alloys, but also for dyes, the most commendable thing is that tungsten trioxide also with excellent photocatalytic performance. Like TiO2, WO3 also has high activity, photochemical stability, non-toxic and so on. If you compare the two, who can be better?

tungsten trioxide and titanium dioxide image

According to the data, TiO2 was the first compound to enter the field of photocatalysis, in 1972, the Japanese discovered that light irradiated TiO2 particles could cause water to undergo a sustained redox reaction, and began the history of photocatalysts. For a long time, TiO2 has been the preferred material for photocatalysis. Until 1983, the scholars in China used WO3 to treat printing and dyeing wastewater for the first time, and achieved very good results. Since then, WO3 has been discovered in application field and application, and gradually catch up from behind, outshining TiO2. How can WO3 compete with TiO2?

TiO2 was used as photocatalyst for a long time. But there are two fatal problems with the performance of TiO2, first, TiO2 has a narrow range of absorption of sunlight, which limits its use of solar energy. Second, photocatalytic reaction efficiency is low, generally not greater than 1%. With the increasingly serious problem of environmental water pollution, TiO2's capacity is too poor, TiO2's weaknesses are the strengths of WO3. From the performance point of view, the activity of WO3 photocatalytic degradation on organic pollutants is higher, the absorption and utilization on sunlight is better.

Tungsten trioxide has better chemical compatibility, WO3 can be mixed with ZnO, Bi2O3, rare earth La, Eu, Y and other elements to form a tungstate photocatalyst, not only pollution control, but also classify the printing and dyeing wastewater, antibiotic wastewater, metal wastewater targeted governance. Therefore, ignoring the price factor, the performance of WO3 undoubtedly has stronger competitiveness.

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Cesium Tungsten Bronze

Cesium tungsten bronze (CsxWO3) is synthesized by solid phase method or liquid phase method with cesium carbonate and sodium tungstate as raw materials.

Cesium tungsten bronze is also called cesium tungstate. CsxWO3 is a non stoichiometric functional compound with a special structure of oxygen eight surface, with low resistivity and low temperature superconducting properties. But in recent years, cesium tungsten bronze is popular for its excellent UV and near infrared shielding performance, with high efficiency, insulation and light reflection effect, this makes it good in the manufacture of special glass, high-end insulation film and LCD screen manufacturing.

In recent years, with the increasing popularity of cesium tungsten bronze, more and more scholars have begun to discuss the liquid phase preparation of cesium tungsten bronze. Some scholars have adopted the hydrothermal method to obtain cesium tungsten bronze, sodium tungstate and cesium carbonate were used as raw materials, in the citric acid solution, the CsxWO3 powder with six square Cs0.33WO3 structure was synthesized by hydrothermal method, and the CsxWO3powder was fully ground and dispersed in a citric acid solution, cesium tungsten bronze film was prepared on glass slide by dipping and dipping method. 

future house image

Through the test of cesium tungsten bronze film, we can draw a conclusion, the CsxWO3 powders obtained by hydrothermal method exhibit strong ultraviolet absorption and short wave near infrared absorption performance, moreover, the absorbance in short wave near infrared region increases with the prolonging of reaction time and the increase of citric acid content. The hydrothermal method failed to solve the cost problem more effectively, but the most important advantage of hydrothermal method is low carbon environmental protection, and the process is easier to control than solid phase method. If more details are to be improved, the large-scale application of cesium tungsten bronze will soon be possible. 

In recent years, with the improvement of people's living requirements, the concept of green house has been popular among people, in the near future, nanotechnology will seep into every detail of live, perhaps our walls, windows, doors, and floors can be made of special glass or paint or film to achieve automatic thermostat adjustment. There is no need to open air-conditioning in summer or open heating installation in winter, real energy saving and environmental protection are achieved, and at that time, such as cesium tungsten bronze and other new materials will certainly have unlimited room for development.

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【Know Tungsten】Sodium Tungstate Applications

Sodium tungstate, Na2WO4•2H2O, a tungstate of sodium, is useful as a source of tungsten. It is prepared from tungsten ores to manufacture tungsten by reducing it. It is often found as dihydrate.
sodium tungstate image
sodium tungstate image

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2019年9月19日星期四

Adipic Acid Catalyzed Preparation by Tungstic Acid

Adipic acid is mainly used for nylon 66 engineering plastics and raw materials, and in the production of various ester products.

Adipic acid is also used for polyurethane elastomer material, acidifier various foods and beverages, sometimes its better than citric acid and tartaric acid. Adipic acid has many functions and a huge demand, but it is a big polluter. The industrial process mainly uses nitric acid to oxidize cyclohexanol and cyclohexanone (KA oil). The method has high yield, but nitric acid seriously damages the equipment and produces a large amount of nitrogen oxides which pollute the environment seriously. With the improvement of human environmental protection consciousness, people urgently need to find environmental protection and pollution-free solutions to solve the problem of adipic acid production.

adipic acid producing equipment image

In recent years, Cao Fabin, a scholar, has proposed that adipic acid is used as catalyst to synthesize adipic acid, according to previous experience, he uses tungstic acid and hydrogen peroxide (H2O2) to make an acidic additive of tungstic acid, in the absence of organic solvent and phase transfer agent, catalyzed 30% hydrogen peroxide oxidation of cyclohexanol to synthetic adipic acid. In the research process, Cao Fabin also found that the addition of suitable active agents could help catalyze the catalytic effect of tungstic acid. After comparing the inorganic substances such as phosphoric acid, phosphorous acid, oxalic acid, resorcinol, sulfonic acid and salicylic acid, he thought that it was most suitable for adding sulfonic acid to an acidic additive of tungstic acid.

The final result shows that when the amount of tungstic acid is 2.5mmol, tungstic acid: acid additive: cyclohexanol: when hydrogen peroxide is 1:1:40:176 (molar ratio), in acid additive, the effect of cyclohexanol oxidation with sulfonic acid and salicylic acid is the best, the yield of reactive adipic acid was 87.8% and the purity was 99.9%. It is worth mentioning that, after the synthesis of adipic acid, acid sulfonic acid and salicylic acid can be put into production again and reused fifth times. The yield of adipic acid separation is still up to 81.5%.

China is a major producer of tungsten, it is feasible to produce an acidic additive of tungstic acid to realize the scale production of adipic acid, using tungstic acid catalyst cyclohexanol method not only has high efficiency, but also to achieve cost control, more importantly is environment friendly. Environmental protection is increasingly valued, enterprises can reduce investment in environmental protection because of the new process, and achieve benefits.

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Why Sodium Silicate Is The Most Common Inhibitor of Scheelite Flotation

There are many inhibitors of scheelite flotation, but the most popular and widely used is sodium silicate, which is recognized by industry as the most effective and cost effective inhibitor.

Sodium silicate, commonly known as water glass, the molecular formula Na2SiO3 is a water-soluble silicate, is a kind of mineral binder, non-sulfide ore, especially a typical inhibitor of silicate minerals. Sodium silicate is selected in the floating scheelite and playing two main functions: one is to make the silica gel modified by physical adsorption on mineral surface, two is the adsorption of SiO32-, HSiO3-, OH- and H+ on the surface of quartz and silicate minerals, which increases the electronegativity and hydrophilicity of the mineral surface.

In scheelite flotation process, sodium silicate was inhibited in quartz, calcite and silicate, generally speaking, sodium silicate is selective when used in low dosage, but using too much will lose the selectivity.

water glass image

Therefore, in order to deal with the complex components of scheelite, people will find helper for sodium silicate, and achieve the ideal effect through the collocation of flotation. The main auxiliary of sodium silicate mainly has the following three members:

1. Metal ions such as AL3+, Mg2+, Cu2+, Fe2+, Ca2+, the combination of sodium silicate with these multivalent metal cations can be effective for fluorite and calcite, the main reason is that sodium silicate and metal cation form metal silicate colloid, and the selectivity of adsorption is enhanced.

2. Sodium silicate combined with Na2CO3. This combination can be used for the separation of scheelite from silicate minerals, its main function is CO32-, HCO3- can be preferentially adsorbed to the surface of calcium minerals, prevent the adsorption of sodium silicate, moreover, silicate minerals can be strongly inhibited by sodium silicate.

3. Temperature. The pulp heated 60-80 °C, can be used for separation of scheelite and calcite, the reason is that the sodium silicate can selectively remove the oleate anion on the calcite surface after heating.

Thus, in the process of scheelite flotation, how to use sodium silicate inhibitors is also a skill, whether it is heated flotation or room temperature flotation, according to the characteristics of sodium silicate can make scheelite flotation to achieve a multiplier effect.

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Nano Cesium Tungsten Bronze Preparation by Solvothermal Method

Cesium tungsten bronze (CsxWO3) is synthesized by solid phase method or liquid phase method with cesium carbonate and sodium tungstate as raw materials.

Therefore, cesium tungsten bronze is also called cesium tungstate. Cesium tungsten bronze CsxWO3 has the function of oxygen compounds in eight face special structure, with low resistivity and low temperature superconducting propertiesaterials. It mainly used to make high-temperature insulation coating, building glass, Low-E glass, automobile insulation film, plant planting shed, LCD screen and so on.

Synthetic of cesium tungsten bronze can be obtained by solid phase method and liquid phase method. In the earlier period, most of cesium tungsten bronze was prepared by solid phase synthesis, such as vapor phase reduction and hydrogen reduction, but the synthesis of solid phase is difficult and the cost is too high. Therefore, with the increasing attention of cesium tungsten bronze, more and more scholars began to study the liquid phase preparation of cesium tungsten bronze and find a way to reduce the manufacturing cost.

cesium tungsten bronze image

Scholars dissolved 400kg sorbitol in a jacketed reactor and dissolved it into tungstate and cesium sulfate, the ratio of the mass ratio of tungstic acid to cesium sulfate is 1 : 0.33, the quality of sorbitol is 3 times the total mass of tungstic acid and cesium sulfate, after high speed stirring 30 min, pump into homogeneous machine to carry on the cycle homogenization, after 60 min, the product is pumped into the high temperature reactor which has been heated to 150 °C, and the high pressure reactor speed is set to 180 r/min. When the above material is completely transferred to the autoclave, turn off the valve of the high-pressure reactor, gradually increase the temperature of the reactor to 350 degrees, and keep 600 min for 150 degrees, release the reaction product, adding deionized water to the filter press, washing with deionized water and absolute ethanol until the sulfate content is below 100 mg/kg, and the content of ethanol is more than 80%, the filter cake is placed in a vacuum oven for drying, and then mechanical pulverization and air flow grinding are carried out to obtain the target product - dark blue cesium tungsten bronze nanometer powder.

The cesium tungsten bronze nano-slurry was added to the acrylic emulsion to coat the film, and the functional film with excellent transparent insulation performance was obtained. The results show that the nanometer tungsten bronze powder with good quality can be prepared by solvothermal method. The transmittance of the functional thermal barrier film at 950 nm is 9.2%, the transmittance of visible light at 550nm is 71%, fog is 0.5%, and the film has excellent infrared absorption characteristics, and it is an excellent transparent thermal insulation material.

Unfortunately, scholars do not seem to solve the cost problem of cesium tungsten bronze by using solvent method. Moreover, the organic solvents in solvent thermal process are volatile and the production process will cause environmental pollution. However, it is certain that the quality of cesium tungsten bronze prepared by solvothermal method is better than hydrothermal method. The results show that the nano cesium tungsten bronze film prepared by solvothermal method not only has good heat insulation effect, but also has a long service life, and the service life is more than 20 years.

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