2020年9月15日星期二

Green Catalytic Activity of Phosphotungstic Acid for Four Hydrogen Sulfide

Four hydrogen sulfide is a chemical intermediate of nitro spray paint, rubber and other solvents, so is often used in the protection of hydroxyl groups.

The catalysts, Lewis acid and ion exchange resin used in the preparation of the four - hydrogen catalyst, all of which have good catalytic effect. However, there are some shortcomings in these methods, such as longer reaction time, reflux, solvent, complex catalyst preparation procedure and unsatisfactory yield.

Phosphotungstates have copper phosphotungstic acid, zinc phosphotungstate and aluminum phosphotungstate. As a kind of heteropoly acid salts, phosphotungstates are widely used as catalysts. It has been proved by experiments that the catalytic activity of phosphotungstic acid for the catalytic hydrogenation of four hydrogen peroxide is better than that of the four hydrogenation of alcohol, thus, a green environmental reaction route is provided for the four hydrogen alkylation reaction better than other methods.

green catalytic activity of phosphotungstic acid for four hydrogen sulfide image

The results show that there are three kinds of phosphotungstates such as copper phosphotungstate, zinc phosphotungstate and aluminum phosphotungstate, which have good catalytic effect on tetrahydropyran. In the reaction catalyzed by copper tungstate, the reaction time of secondary alcohol and tertiary alcohol is longer, and the activity of Bibb alcohol is relatively low; the reaction of aluminium tungstate catalyzed alcohol (except n-butanol, SEC butyl alcohol and tert butyl alcohol) is in progress, the catalytic activity of alcohol is very high, and the structure of alcohol has little effect on the catalytic effect; And zinc phosphotungstate as a catalyst, regardless of which structure of the alcohol structure of its activity are very high.

It can be seen that phosphotungstic acid can provide a simple, new and efficient and environmentally friendly reaction pathway for the protection of hydroxyl groups, which is the effective catalyst for tetrahydropyran.

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Pesticide Pollution Treatment by Potassium Phosphotungstate

Chlorothalonil is an efficient fungicide absorbed in organic pesticide, organic compounds but it is also easy to cause pollution of soil.

In the process of agricultural operations, the land often contains chlorothalonil which is difficult to degrade, not only the soil ecological structure is affected, but it is often washed by rainwater to enter the river or infiltrate the ground water, causing serious pollution.

In recent years, with the tungsten based photocatalyst for environmental, economic, effective and has become a new method for the treatment of organic wastewater, some scholars have found that most of the organic pesticides is easily degraded and mineralized into H2O and CO2 and other small molecules, so the photocatalytic degradation of chlorothalonil is feasible.

.degradation of chlorothalonil by phosphotungstic acid image

Tungsten photocatalysts mainly consist of tungstate and tungsten heteropoly acids, the commonly used method is to use a combination of loading and photocatalyst to form a new composite preparation for photocatalytic work, a common load has cloth, holes, sieves, or other chemicals. Some scholars believe that phosphotungstic acid has good degradation effect on chlorothalonil, and in order to verify his opinion, potassium chloride is used to degrade phosphotungstic acid.

During the experiment, he added potassium chloride and phosphotungstic acid to 2.5:1 in proportion to H3PW12O40 water solution and stirred it to produce a white precipitate, continue to stir 10h until the precipitation is complete, centrifugal separation, washed with deionized water, white precipitate to no Cl, and then dried, baking at 300 hours, made into potassium tungstate.

Through the contrast test of two chlorothalonil solution showed that potassium phosphotungstate catalyst of chlorothalonil solution has good photocatalytic effect, not only this, have the effect of all similar pesticides, and very small amount of it. It is estimated that 1 grams of potassium phosphotungstate degradable 10L chlorothalonil solution (5mg/L), light degradation time is 4 hours, the degradation rate is 86.22%, the effect is ideal. And the use is also very convenient, that is, before the allocation of pesticides, according to the proportion of phosphorus potassium tungstate stirring can be used.

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Photocatalytic Activity of Bismuth Tungstate Upgraded by Polyester Fiber

Bismuth tungstate (Bi2WO6) is the most common Aurivillius type oxide and is a hot spot in the field of photocatalysis.

Most of the traditional photocatalytic reactions are carried out in the suspensions of bismuth tungstate catalyst powders. Although they have high photocatalytic activity, bismuth tungstate powders are easy to agglomerate and difficult to separate and recover. In practice, it was recognized that some measures had enabled bismuth tungstate to work, and some scholars had thought of loading bismuth tungstate onto the cloth.

bismuth tungstate photocatalysis image

Of course, loading bismuth tungstate on cloth is not a simple mix, and it also requires a series of chemical procedures that combine bismuth tungstate with cloth to function. Acrylic, polyester fiber and so on, have the same effect at last, and their main difference is synthetic method.

Some scholars used polyester as the carrier of bismuth tungstate and prepared them by hydrothermal method, the polyester fabric was treated with acetone and ethanol at 50 °C for 30 min and 80 °C by ultrasonic cleaning. Then soak 40 min in butyl acrylate and dry. Twelve sodium sulfate and Bi2WO6 powder were dissolved in 50 mL deionized water, and then 2 h at room temperature and then removed and dried to obtain the load polyester fabric.

The results show that Bi2WO6 loaded polyester fabric has better UV resistance and water repellency than Bi2WO6 powder alone. The photocatalytic results show that the Bi2WO6 load of polyester fabric on the degradation of methylene blue was significantly higher than that of Bi2WO6 powder, the degradation efficiency of methylene blue reached 92%, this is because the load after Bi2WO6 got a stable platform, can play a balanced effect.

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Graphene, Bismuth Tungstate, Titanium Oxide

Bismuth tungstate is a popular new visible light catalyst, especially petal shaped bismuth tungstate.

It has good light absorption and high stability, and has broad application prospects in the field of photocatalysis.

The scholars in our country believe that the proper doping of bismuth tungstate, the preparation of semiconductor compound and assistant modification are effective ways to improve the photocatalytic property of bismuth tungstate.

treatment of methyl wastewater image

In recent years, graphene has brought tremendous changes to the material industry because of its unique two-dimensional structure, large specific surface area and high electron transmission rate. It has been recognized as the "king of new materials", Chinese scholars believe that graphene as an efficient electronic additive, and Bi2WO6 composite catalyst, will greatly improve its light capture electronic capabilities, thereby enhancing catalytic capacity. However, scholars believe that only graphene is not enough, and the number of photocatalytic holes will also be increased to improve the cavity manufacturing capacity of bismuth tungstate.

In the photodegradation process, the main active species, HO, is obtained by the reaction of holes and H2O. In recent years, adding cavity additives into photocatalyst is a popular method. Amorphous oxide amorphous TiOis a common assistant, and TiO2 is also a photocatalyst. It is found that the amorphous TiO2 film can be applied to the surface of BiVO4 and GaAs electrodes to transfer the photogenerated cavity rapidly.

With bismuth tungstate (Bi2WO6) as the main catalyst, graphene (rGO) is an electron assistant, and TiO2 (TIO2) is a hole assistant, three Musketeers combined to degrade methyl wastewater. Ti (IV) -rGO/Bi2WO6 has been prepared by hydrothermal impregnation deposition method to degrade methylene orange. The test concluded that the catalytic rate of composite catalyst are pure Bi2WO6, Ti (IV) Bi2WO6 / rGO/Bi2WO6, 88 times, 67 times and 17 times, enhance the photocatalytic performance is mainly due to the Ti (IV) and rGO double additive synergistic effect, rapidly capture and transfer of photogenerated holes and electrons promote separation between them, thus effectively reducing the recombination of photogenerated carriers.

From the cost point of view, bismuth tungstate is the most expensive, followed by graphene, titanium dioxide is the cheapest, they reduce the use of bismuth tungstate, cost a great deal of medicine, and the effect is greatly increased. Therefore, the use of new additives to modify the photocatalytic materials will be most likely to become mainstream methods in the future.

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2020年8月11日星期二

Ultrafine Ammonium Metatungstate Acquisition Strategy

Ammonium metatungstate (AMT) is one of the most important raw materials and precursors for the preparation of WC.

spray drying method image

The structure and properties of WC are affected by the physical and chemical properties of precursor. The particle size and structure of precursor will greatly influence the process of reduction and carbonization in the late stage, and then affect the catalytic activity of WC catalyst.

In order to obtain precursor with good particle size and good structure, spray drying is usually used. Spray drying has many advantages, such as simple process, no pollution, homogeneous composition, and suitable for mass production.

The basic principle of spray drying method is ammonium metatungstate solution by spray drying, in a few seconds, water quickly evaporated into powder, physical and chemical properties of homogeneous granular, hollow spherical or spherical solid products.

Many scholars have found that in the spray drying process, the concentration of ammonium tungstate solution has an important influence on the morphology of ultrafine tungsten powder, and so does ammonium metatungstate.

Some scholars have investigated the effects of different feed concentration, feed rate and the addition of surfactants on the particle size of microspheres under aerobic spray drying conditions. The results show that the feed concentration is 5% at the inlet temperature of 200 °C, the outlet temperature is 90 ~ 100 °C, the air velocity is 550 L· min-1 and the feed rate is 7 m L · min-1 (d50) was 2.26 um. The AMT was prepared by the precursor solution, and the minimum median diameter (d50) was 2.26 um; AMT with solid solution concentration of 50% (WT) is the solid microsphere, and the minimum median diameter (D50) is 6.43 mu m. The greater the solubility, the greater the particle.

From an economic point of view, the concentration of the liquid should be as high as possible, because it can reduce the water content in the solution, thereby reducing the amount of hot air used for evaporating water, and reducing energy consumption. However, the ultrafine ammonium metatungstate precursor can be obtained by analyzing the technical requirements, and the ammonium metatungstate can be obtained with lower concentration.

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How to Extract Rare Element Rubidium with Phosphotungstic Acid

 Rubidium, as a rare and weak alkali metal element, has been widely used in organic catalysts, photomultiplier tubes, special glass and anticancer drugs.

extraction of rare element rubidium by phosphotungstic acid image

Rubidium does not have independent minerals, often and other alkali metals coexist in lithium mica, cesium garnet, lithium cesium garnet, natural carnallite, salt lake brine and underground brine. Because of the coexistence of rubidium and sodium and cesium, which are closely related to the physical and chemical properties, the extraction technology of rubidium is very difficult, which results in a large amount of brine rubidium resources not being rationally utilized.

The common methods for separation of rubidium and cesium are fractional crystallization, precipitation, solvent extraction and ion exchange. In industrial production, precipitation method is used to separate rubidium and cesium, which is mainly used to separate rubidium and cesium from high content solution. Solvent extraction is easy to realize continuous operation and has great potential for application.

Extractant is the most important extractant. Some scholars believe that the salts of heteropoly acids such as phosphotungstic acid and phosphorus molybdate have higher selectivity to rubidium and cesium. However, since the powder is too fine and unsuitable for the continuous operation of the exchange column, it is difficult to be used in the actual production process. Therefore, it is an ideal way to prepare the composite adsorbent by loading the heteropoly acid salt on other carriers.

Some scholars used calcium alginate as carrier and ammonium phosphate as active component to extract rubidium and cesium directly from mother liquor, the research shows that the composite adsorbent can extract Rb+ directly from the mother liquor containing about ten thousand times of impurities. The extraction rate of RbCl is above 92%, the desorption rate is nearly 100%, and it can be reused again and again.

At present, the total reserves of rubidium (excluding rubidium in seawater) are about 10 million 770 thousand tons, of which more than 92% and about 10 million tons exist in Saline Lake, in view of the role of rubidium and the reserves of rubidium, the rubidium resources in the brine of Saline Lake will be the focus of future development, and the solvent extraction method with ammonium phosphotungstate is the most promising method of industrial application.

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Microwave Ultrasonic Method for Customizing Ultrafine Ammonium Paratungstate

Ammonium paratungstate (APT) is the main raw material for the production of tungsten powder, tungsten carbide powder, tungsten wire and tungsten products.

microwave ultrasonic machine image

As everyone knows, the tungsten particle size, crystal morphology of its APT has a great "inherited" relationship, so, if want to produce nanometer tungsten powder and tungsten carbide powder, we first need to prepare ultrafine ammonium paratungstate (APT).

It is an innovative method to prepare superfine ammonium paratungstate (APT) by microwave ultrasonic combined crystallization. Many scholars have shown that compared with traditional heating crystallization, microwave ultrasonic combined crystallization has obvious advantages in speeding up the crystallization rate, refining the particle size and improving the purity of products. So what's the difference between microwave - ultrasonic combined crystallization and traditional evaporation crystallization?

Some scholars have used microwave-ultrasonic combined crystallization method for ultra-fine ammonium paratungstate (APT) preparation test, they used a certain volume of ammonium paratungstate solution placed in the use of XH-300A computer ultrasonic microwave combination synthesis extractor, set the ultrasonic frequency of 25 K Hz, adjust the microwave and ultrasonic power, in the specified value, using ultrasonic wave with microwave heating, at 45, 65, 80, 90, 95 degrees Celsius for evaporation crystallization, after a certain period of time, while the heat filter. After filtration, the filter material was washed with deionized water for 2 to 3 times, and the filtered material was dried in an electric constant temperature oven at 100 °C for 2 h to obtain ultrafine ammonium paramate powder.

The experiment concluded that in the absence of mechanical or magnetic stirring, adding surfactant, in the optimum preparation conditions of APT ultrasonic frequency of 25 K Hz, power 1000 W, microwave power 700 W, temperature 80 °C, ammonium tungstate concentration of WO3212 g/L, CO time 15 min, fine crystal APT-4 with average particle size of 7.6 m, uniform particle size distribution and crystal integrity can be obtained by microwave ultrasonic combined crystallization method.

Microwave ultrasonic assisted evaporation and crystallization can be prepared by micro APT in high temperature and without the addition of surfactant, can influence the crystallization rate and preparation of surfactants micro APT process APT purity to overcome the disadvantages of traditional heating. However, this method is only suitable for small scale production, more suitable for the special needs of the private custom, the main reason is the large microwave - ultrasonic equipment manufacturers almost did not come out, there are also expensive.

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Bismuth Tungstate Photocatalyst Modification

 In recent years, because bismuth tungstate (Bi2WO6) has narrower band gap and wider visible range than titanium dioxide (TiO2), it has a great tendency to replace TiO2.

bismuth tungstate photocatalysis image

However, in practical applications, it was found that bismuth tungate is good, but there are some shortcomings, mainly in its photogenerated electrons and holes easy to complex, quantum efficiency is not high. Therefore, scholars believe that bismuth tungstate should be added with some elements to excite the photocatalytic potential of bismuth tungstate.

Some scholars have made Au (Ag) / Bi2WO6 nanocomposites with bismuth tungstate doped with gold or silver. The results show that the degradation efficiency of RhB solution is 40% using Au (Ag) / Bi2WO6 nano photocatalyst, and the efficiency is 99.2%, higher than that of pure Bi2WO6.

Some scholars have suggested that the Pt/Bi2WO6 composite can be used for photocatalytic degradation of Mo methyl orange by doping bismuth with platinum. The results show that the photocatalytic activity of Mo solution is reduced to 100% by using 0.3Pt/ Bi2WO6 composite photocatalyst, and the photocatalytic activity of the photocatalyst is still active and recyclable.

It is said that the nano crystalline Bi2WO6 powder is mixed with a small amount of TiO2 powder and is hydrothermally mixed. The structure of the photocatalyst is still Bi2WO6 crystal structure, however, the properties of the two compounds show good visible light response range and catalytic activity.

Of course, if you think the doped TiO2 material is too low, then change to the king of new material graphene, it is found that graphene is an excellent conductor, and graphene, as an efficient electron promoter, can be combined with Bi2WO6 catalyst to increase its light capture capability and enhance its catalytic capability. The results show that rGO/Bi2WO6 has a catalytic effect on dye wastewater. The decolorization rate is 92%, which is about 30% higher than that of pure bismuth tungstate.

Recently, some scholars have proposed a more comprehensive doping scheme, which is based on bismuth tungstate as the main catalyst and doped graphene and titanium dioxide. TiO2 assisted Bi2WO6 to generate more holes, and graphene assisted Bi2WO6 to capture electrons. By combining, the potential of bismuth tungstate is fully activated. It not only has a photocatalytic rate of 99% of methyl waste water, but also has strong degradation ability to pesticide wastewater and organic wastewater.

With the development of bismuth tungstate photocatalyst, more bismuth tungstate photocatalytic activity will be improved in the future. In addition, another point to mention is that by chemical methods bismuth tungstate in polyester or acrylic fiber load, it is more favorable for the recovery and reuse of bismuth tungstate photocatalyst in practice.

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2020年7月17日星期五

Nano Tungsten Oxide Expected to Solve the Problem of Lithium-ion Battery Material Shortage

With the vigorous development of the new energy vehicle industry, the demand for power lithium-ion battery continues to heat up, causing many lithium-ion battery materials to face supply shortages. Many people in the industry said that whoever has the upstream lithium resources, nickel resources and cobalt resources will have the initiative to develop power batteries.

In view of the above situation, perhaps tungsten resources can effectively alleviate it. It is reported that in recent years, energy storage scientists have developed a lithium-ion battery using nano tungsten oxide as the electrode material, which has good physical and chemical stability, strong endurance and the advantage of civilian prices, mainly because of the oxidation tungsten powder is easy to prepare and has relatively new photoelectric properties. In addition, China is the country with the most abundant tungsten resources in the world, distributed in 23 provinces and autonomous regions, and its output ranks first in the world, that is, its reserves are four times the combined reserves of other countries in the world. Therefore, tungsten resources are considered by many people as one of the most likely mineral resources to solve the shortage of lithium-ion battery materials in the future.

tungsten trioxide nanoparticles photo

At present, China is the world's largest lithium-ion battery market, and it faces a shortage of various lithium-ion battery materials, such as lithium resources. Domestic lithium resource consumption accounts for more than 40% of the world's total. Although China's lithium resource reserves account for 20% of the world's total, mining is difficult and costly, unable to meet domestic market demand, and has a high degree of external dependence. Therefore, Zheng Mianping, an academician of the Chinese Academy of Engineering, said that lithium raw materials can be extracted by improving the adsorption and membrane technology, precipitation method, ion exchange adsorption method and other methods to improve the recovery rate of lithium metal in the battery.

lithium ion battery photo

In short, there are many ways to solve the shortage of lithium-ion battery materials. Lithium battery companies can choose the appropriate way according to their actual situation.

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Niobium Tungsten Oxide Expected to Realize Fast Charge of Lithium-ion Batteries

As the lithium-ion batteries that power most phones, laptops, and electric vehicles become increasingly fast-charging and high-performing, they also grow increasingly expensive and flammable.

In research published recently in Energy Storage Materials, a team of engineers at Rensselaer Polytechnic Institute demonstrated how they could — by using aqueous electrolytes instead of the typical organic electrolytes — assemble a substantially safer, cost-efficient battery that still performs well.

If you were to take a look inside a battery, you’d find two electrodes — an anode and a cathode. These electrodes are immersed in a liquid electrolyte that conducts ions as the battery charges and discharges.

niobium tungsten oxide photo

Aqueous electrolytes have been eyed for that role because of their non-flammable nature and because, unlike non-aqueous electrolytes, they aren’t sensitive to moisture in the manufacturing process, making them easier to work with and less expensive. The biggest challenge with this material has been maintaining performance.

“If you apply too much voltage to water it electrolyzes, meaning the water breaks up into hydrogen and oxygen,” said Nikhil Koratkar, an endowed chair professor of mechanical, aerospace, and nuclear engineering at Rensselaer. “This is a problem because then you get outgassing, and the electrolyte is consumed. So usually, this material has a very limited voltage window.”

In this research, Koratkar and his team — which included Fudong Han, an endowed chair assistant professor of mechanical, aerospace, and nuclear engineering and Aniruddha Lakhnot, a doctoral student at Rensselaer — used a special type of aqueous electrolyte known as a water-in-salt electrolyte, which is less likely to electrolyze.

niobium tungsten oxide structure photo

For the cathode, the researchers used lithium manganese oxide, and for the anode, they used niobium tungsten oxide — a complex oxide that Koratkar said had not been explored in an aqueous battery before.

“It turns out that niobium tungsten oxide is outstanding in terms of energy stored per unit of volume,” Koratkar said. “Volumetrically, this was by far the best result that we have seen in an aqueous lithium-ion battery.”

The niobium tungsten oxide, he explained, is relatively heavy and dense. That weight makes its energy storage based on mass about average, but the dense-packing of niobium tungsten oxide particles in the electrode makes its energy storage based on volume quite good. The crystal structure of this material also has well-defined channels — or tunnels — that allow lithium ions to diffuse quickly, meaning it can charge quickly.

The combination of fast-charging capability and the ability to store a large amount of charge per unit volume, Koratkar said, is rare in aqueous batteries.

Achieving that kind of performance, with a low cost and improved safety, has practical implications. For emerging applications such as portable electronics, electric vehicles, and grid storage, the ability to pack the maximum amount of energy into a limited volume becomes critical.

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Nano Tungsten Oxide in Anti-virus Application

At present, the spreading of COVID-19 is furious in the world. Several previous difficult viruses (such as HIV, HBV, PIV, etc.) have not yet been attacked, and new mutant viruses (such as SARS coronavirus, avian influenza virus, and H1N1 influenza virus, etc.) have appeared in humans, seriously affecting human health. 

Many viruses, such as influenza virus, SARS coronavirus, avian influenza virus, and human immunodeficiency virus, are difficult to control. The main reason is that these viruses are infected on the mucosal surface, the antigenicity is weak, and antigenic mutations and drug resistance mutations are prone to occur. This has led to poor clinical prevention or treatment of these viruses.
tungsten trioxide structure photo
The detection, prevention and treatment of infectious diseases are difficult problems in the medical field. At present, the control of viral infectious diseases is mainly vaccine prevention, but there is no effective treatment strategy for established viral infections. However, with the advancement of medical research, researchers have discovered that there are some antiviral materials in the world, and some have already been clinically applied.

The application research of nano tungsten oxide in biomedicine is currently less. With the development of nano-medical science, some new functions of nano tungsten oxide have been gradually discovered, especially in the field of anti-virus application, showing broad prospects. For example, tungsten oxide nanodisks with specific surface morphology can be well used for antibacterial applications; two-dimensional layered tungsten oxide nanosheets have a plasmon resonance effect, which can absorb near-infrared light, making them suitable for photoacoustic diagnosis and treatment of tumors. Photothermal removal and other biomedical applications have a wide range of applications. Tungsten trioxide nano spheres have great potential for insoluble drug loading and delivery. 2nm-sized tungsten trioxide nanoparticles can be used as biological enzyme catalysts by electron transfer achieves sulfite oxidase activity.

Nano particles such as gold, copper, zinc oxide, and titanium dioxide have antibacterial and antiviral activities. The heavy metals silver, copper, lead, mercury and other salts can react with sulfhydryl groups in proteins or replace metal ions in enzymes, inactivating most enzymes. Therefore, heavy metal ions have a broad spectrum of antibacterial and antiviral activities.

It is worth noting that although metal nanomaterials have excellent antibacterial and antiviral activity, there is still some controversy about their toxicity mechanism, and the release of metal ions will pose a potential threat to the environment and the human body.
graphine oxide structure photo
As a derivative of graphene, graphene oxide is a flake of graphite oxide. Through plaque formation test, indirect immunofluorescence and Westernblot verification, the researchers found that graphene oxide nanomaterials are prevalent to pseudorabies virus (DNA virus) and swine Diarrhea virus (RNA virus) has a good antiviral effect, and this inhibitory effect has a time and dose-dependent effect. In addition, the researchers also found that two-dimensional sheet-like nanomaterials such as molybdenum disulfide and tungsten disulfide also have good antiviral effects, but compared with graphene oxide, their inhibitory effect is reduced.

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Nano Tungsten Oxide Applied in Cobalt-free Lithium Ion Battery

As one of the most hot topics recently, cobalt-free lithium ion battery is considered as an upgraded version of the current commercial ternary lithium ion battery. Because of their higher energy density and lower production costs, they are popular among many battery manufacturers. As a typical transition metal N-type semiconductor material, how should nano tungsten oxide be used in cobalt-free lithium battery?

Nano tungsten oxide can be used as a modifier for the anode material of cobalt-free batteries, and can also be used to produce high-performance anode materials. In terms of cathode materials, the use of WO3 can not only reduce the use of cobalt metal, but also effectively improve the specific capacity and thermal stability of the product. In terms of anode materials, the use of WO3 can significantly improve the rate performance and lithium storage kinetics.

nano tungsten oxide photo

As we all know, the biggest cost of new energy vehicles lies in power batteries. As far as the ternary lithium battery that currently dominates the market, the cobalt contained in it is a very important rare metal with a small distribution area and low output, making the cobalt price center of gravity relative to other rare metals for a long time. All are in a higher position, which greatly increases the production cost of power batteries.

At present, the price range of electrolytic cobalt is between 245~255 thousand RMB/ton, the price range of cobalt powder is between 266~269 thousand RMB/ton, cobalt sulfate is 4.45-4.70 million yuan/ton, cobalt chloride is between 54-57 thousand RMB /ton, tricobalt tetrachloride is between 175,000-180 thousand RMB /ton, cobalt chloride is 174~179 thousand RMB /ton. and cobalt sulfide is between 116~119 thousand RMB /ton.

cobalt free battery photo

In the context of the gradual retreat of subsidies for new energy vehicles in 2019 and the attack of COVID-19 in 2020, the removal of cobalt and chemical conversion have become the common choice of many power battery companies. In February 2020, the concept of Tesla's cobalt-free battery was introduced, and cobalt removal was pushed to the cusp. Various cobalt-free solutions gradually appeared in power battery companies.

Tungsten trioxide nanoparticles are often used by domestic researchers to replace the cobalt element in lithium ion batteries because of their unique physical and chemical properties. This is mainly because tungsten oxide has the characteristics of large specific area, high specific gravity, and good mechanical stability, which can significantly improve the specific energy density and thermal stability of the cathode material. This means that the positive electrode material containing tungsten trioxide is less likely to undergo thermochemical reaction with the electrolyte, thereby reducing the possibility of a sudden rise in partial pressure and temperature in the battery.

In order to further improve the capacity and charge-discharge rate performance of cobalt-free batteries, some researchers have indicated that tungsten trioxide powder can also be used to prepare the anode material. However, it should be noted here that tungsten trioxide needs to be compounded with graphene (RGO), which can significantly improve the overall electrochemical lithium storage performance of the composite material.

Due to the synergistic effect between tungsten trioxide and graphene, the reversible specific capacity of WO3/RGO nanocomposites at 0.1C rate is not only far superior to WO3 and RGO monomers, but also greater than the sum of the two monomers.

In addition, WO3/RGO nanocomposites also have stable cycling performance and good rate performance. After 100 cycles at 0.1C rate, its reversible specific capacity remains at 635mA/g, and the capacity retention rate is 83.4%; at 5C rate, its reversible capacity can still maintain 460mA/g, which is lower than the graphite negative electrode used in commercial lithium batteries. The theoretical specific capacity of the material (372mA/g) is much higher, which also indicates the potential application of the prepared tungsten trioxide/graphene composite material in a new generation of lithium ion batteries.

The vigorous development of cobalt-free batteries may help to further increase the demand for tungsten trioxide.

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2020年6月24日星期三

Photocatalytic Production of Benzoic Acid with Bismuth Tungstate

Benzoic acid is a flake or needle like crystalline with a smell of benzene or formaldehyde, usually made by selective oxidation of toluene.

photocatalytic production of benzoic acid with bismuth tungstate image

Toluene is obtained by a series of oxidation processes. Benzoic acid is an important food preservative, and is also used in medicine, dye carriers, plasticizers, spices and antibacterial agents. In the traditional chemical process, the production of benzoic acid from toluene requires selective oxidation of toluene under severe conditions, such as high temperature, high pressure, and acidic solvents. Generally speaking, the process is costly and polluting.

Tungstate is a kind of photocatalyst which is widely used in industrial wastewater treatment, but some scholars have made use of the principle of petal type bismuth tungstate photocatalyst to produce benzoic acid. Because bismuth tungstate can use oxygen as oxidant to catalyze the oxidation of toluene and its derivatives, thereby simplifying the preparation of benzoic acid and reducing pollution.

In the process of studying the oxidation of benzoic acid by catalytic oxidation of toluene with bismuth tungstate, it is found that the petal like bismuth tungstate powder has the highest activity. By means of X ray diffraction, scanning electron microscopy, UV Vis absorption spectra and experimental results indicate that surface flower like bismuth tungstate powder showed the best activity for the oxidation of toluene and it is likely to be the largest surface area has a relationship. Because Bi2WO6 is excited by light, electrons are excited by light and leave holes that form electron hole pairs, these photogenerated electron hole pairs give rise to stronger oxidation and reduction signals because of their strong redox power, while electrons and holes play a corresponding role in the oxidation of toluene, thus facilitating the reduction.

In recent years, bismuth tungstate has become a new force for environmental protection because of its good photocatalytic performance, but it is rare in the application of catalysts, the reduction of benzoic acid with bismuth tungstate not only provides a new idea for the oxidation and reduction of toluene, but also provides an effective method for the green production of benzoic acid.

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Tungsten Trioxide Helps Catalyze SCR Soot Denitrification Technology

The nitrogen oxides produced by coal combustion as a pollutant will affect human health.

The most harmful is NO2, which mainly affects the respiratory system of human beings, and can cause bronchitis and emphysema.

SCR selective catalytic reduction technology has become the most widely used and most effective flue gas denitrification technology in the world. It has the advantages of low reaction temperature, high purification rate, reliable operation and small two pollution. After its catalysis, the main non-toxic and non polluting N2 and H2O are produced.

SCR soot denitrification technology image

In the SCR soot denitrification technology selective catalytic reduction system, it is generally composed of ammonia storage system, ammonia and air mixing system, ammonia injection system, reactor system and monitoring control system, the thermal power plant, SCR reactor is usually installed in the boiler economizer and air preheater, here for the high dust temperature arrangement, smoke temperature in this region for SCR denitrification reaction, ammonia injection in the appropriate position in the flue between economizer and SCR reactor, and the flue gas mixture after the reaction with NOx catalyst in the reactor. The catalyst is placed in a solid reactor. The catalyst unit is usually vertically arranged and the flue gas flows up and down.

Catalyst is one of the core of SCR technology, its cost is about 20%~40% of the total cost of SCR system, and the performance of catalyst has a direct impact on the removal efficiency of NOx. For SCR systems, the three main commercial catalysts are noble metal catalysts, metal oxide catalysts, and molecular sieve catalysts. At present, metal oxide catalysts are the most widely used in industry because they are the cheapest. In the past, vanadium titanium catalyst is the main catalyst for selective catalytic reduction system of SCR in China. But in recent years, scientists have found that titanium tungsten vanadium catalysts are more active, selective, antioxidant and anti toxic, and they are expected to be the first choice of catalysts.

Some scholars use imported V2O5 - WO3/TiO2 catalyst to test the effect of SCR, with the help of tungsten trioxide, SCR denitration ratio reached 100%, compared with the traditional vanadium and titanium powder, the effect increased by 30%, the effect is very obvious, but the cost has also increased a lot. For some enterprises, environmental protection measures are only a move, and raising environmental costs is tantamount to their lives, which is the biggest obstacle to the commercial popularization of titanium tungsten vanadium SCR catalyst.

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Single Layer Tungsten Disulfide Challenge Graphene (2)

Tungsten and carbon have many similar physical properties, such as high melting point, high hardness, and better conductivity and thermal conductivity.

So foreign scientists first took aim at tungsten. In recent years, foreign scholars through the study found that single layer tungsten disulfide also has excellent semiconductor performance, it not only has excellent characteristics of graphene, there are more excellent than the characteristics of the semiconductor, two tungsten sulfide has a considerable band gap, and it also shows new properties: As the number of atoms increases, the bandgap becomes tunable, and its electron migration rate is better than that of graphene, which is the ideal choice for transistor materials.

single layer two tungsten sulfide image

There is no doubt that the emergence of graphene and other two-dimensional materials to the world's material industry brought about tremendous changes, as China attaches great importance to the material industry, graphene manufacturing technology has achieved many achievements, the cost of graphene has greatly declined, making the use of two-dimensional materials rapidly spread. In many areas, graphene has the advantage of excellent compatibility and cost control, and is "the king of new materials". But in the field of semiconductor such as transistors, high-performance single layer two tungsten sulfide has the absolute strength beyond the performance of graphene.

China is not only a big producer of graphene, but also a major producer of tungsten. Tungsten is an important strategic resource of non renewable. The price of monolayer tungsten disulfide is one to two times higher than that of graphene, which is probably the main reason why monolayer tungsten disulfide is difficult to produce as much as graphene. However, if a single layer of tungsten disulfide and graphene made of composite material? This may be feasible. Looking forward to the future, we can exploit the advantages of raw materials to develop a microprocessor with Chinese proprietary rights. In the future of the intelligent world, we use those than the performance speed is almost a few times or even hundreds of times the computer, mobile phone, or VR equipment, and even intelligent robots, they can be a real Chinese core.

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Catalytic Synthesis Edible Perfume Butyric Acid Vinegar with Tungsten Silicate

Tungstic acid is a tungsten heteropoly acid, with keggin structure, the appearance of white or pale yellow deliquescence crystals, soluble in water and alcohol.

Butyrate but also known as butyl butyrate, can be used as bananas, pineapple and other fruit essence, used in beverages, cakes and bread food. Its traditional synthesis method is under the catalysis of sulfuric acid, esterification by butyric acid and butanol. However, the method has the disadvantages of long reaction cycle and low yield. Meanwhile, sulfuric acid has a strong corrosion on the equipment and produces wastewater that pollutes the environment.

In recent years, in the food additives industry, tungsten silicate and tungsten phosphate have been widely used in place of traditional acid catalysis. They are both effective and environmentally friendly. They are the gospel of the whole food processing industry.

butyric acid butyl vinegar image

The preparation of butyric acid vinegar is the synthesis of butyric acid vinegar by the catalysis of tungsten silicate, the butyric acid and a certain amount of catalyst, with water and butanol added to the three bottles, with water and butanol three neck bottle, equipped with water separator, built-in quantitative saturated salt water, heated to reflux with an electric hot pot, before the reaction stopped 15min, began with water and excess alcohol distillation, the product is then cooled and butyric acid vinegar is obtained.

Tungsten silicic acid has good catalytic properties. Most of the strong acid needed to catalyze the synthesis of food additives, such as butyl acetate butyrate, isoamyl acetate, octyl acetate, levulinic, can be catalyzed by phosphotungstic acid or tungstic acid with Keggin structure. Because the structure of tungsten heteropoly acid of Keggin structure is simple, the structure is determined, and the structure characteristics of complexes and metal oxides are also included, not only with inorganic acids (such as sulfuric acid) and solid acids (such as molecular sieves), it has the essence of acid catalysts, it also has the function of free or oxygen-containing organic compounds (such as alcohols, ethers, etc.) free in and out of the heteropoly phase, which is called "pseudo liquid phase". Therefore, heteropoly acid as an acid catalyst, its acidity is much stronger than inorganic acid, but it is more environmentally friendly.

Therefore, it is necessary to test the synthesis of similar food additives, which can be safely used with phosphotungstic acid and tungstic acid as the catalysts of the two types of heteropolyacid salts.

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Green Catalytic Activity of Phosphotungstic Acid for Four Hydrogen Sulfide

Four hydrogen sulfide is a chemical intermediate of nitro spray paint, rubber and other solvents, so is often used in the protection of hydr...