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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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...