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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2020年6月1日星期一

Tungsten Silicate Catalytic Synthesis Cinnamic Acid Isopentyl Acetate

Tungsten silicate is a kind of tungsten heteropoly acid with Keggin structure, recently it is widely used as food additives on catalytic synthesis.

cinnamic acid isopentyl acetate image

Its appearance is white or pale yellow deliquescent crystal. Isopentyl cinnamate is a kind of perfume. It is a colorless viscous liquid with cocoa flavor. It is mainly used in food and daily chemical industry. It is a kind of spice which has a bright future to be developed. The traditional synthesis is catalyzed by sulfuric acid, cinnamic acid and isoamyl alcohol process acetification, the main drawback of this method is the existence of long reaction time, low yield, complex process polluted water on environment, sulfate has strong corrosive effect on equipment.

Tungsten silicate is an environmentally friendly green catalyst, it has the structural characteristics of complexes and metal oxides, it has the acid catalysts function as inorganic acids (such as sulfuric acid) and solid acids (such as molecular sieves). In the food additives industry, it has also been used to replace traditional acid catalysts, both effective and environmentally friendly.

Test method for synthesis of cinnamic acid isopentyl acetate is that get some cinnamic acid and a certain amount of catalyst, water carrying agent (benzene) isoamyl alcohol into three bottles, equipped with water separator, the water separator is equipped with quantitative saturated salt water, heat the reflux with an electric pan,  then begin to steam the water carrying agent and the excess alcohol 15min before stopping the reaction, and cool the product down.

The reaction conditions for tungsten silicate catalytic synthesis of cinnamic acid isopentyl acetate is mild, acetification rate is high, less dosage, recyclable. Therefore, tungsten silicate can be used instead of many kinds of food additives in the synthesis of acid catalysts, which is basically a consensus among many scholars.

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Tungsten Silicate Catalyze Preparing Edible Flavor Octyl Acetate

Tungsten silicate is a tungsten heteropoly acid, its appearance is white or pale yellow deliquescent crystal, soluble in water and alcohol, soluble in crystal water itself.

octyl acetate image

When heated, it has decomposition when under 600~650°C. Tungsten heteropoly acid is often used as a catalyst, so as tungsten silicate.

Octyl acetate exist in citrus oil, green tea leaf oils and so on, it also exist in fruit. Octyl acetate is identified as non-toxic food by FEMA (the flavor and Extract Manufacturers Association). The preparation of octyl acetate can not be separated from the strong acid catalyst. Due to the oxidation and strong dehydration of concentrated sulfuric acid, the esterification rate is reduced, the quality of ester is poor, and the equipment is seriously corroded. A lot of waste liquid is produced in the post-treatment process, which pollutes the environment and so on.

Tungsten heteropoly acid is a kind of green environmental friendly catalyst, in recent years, in the food additives industry, it is widely used to replace traditional acid catalyst, it is efficient and environmentally friendly. Phosphotungstic acid and tungsten silicate is that kind of catalyst.

Method for preparing octyl acetate is that a certain amount of acetic acid, octyl alcohol and tungsten silicate in three bottles, oil bath is heated to a certain temperature, after stirring, reflux, and cooling down the reaction liquid, filtering to remove the catalyst, filtrate analysis by gas chromatography, to test the alcohol conversion rate and selectivity of octyl acetate. The optimum conditions for the preparation and esterification of the catalyst were determined by changing the amount of catalyst, the time of calcination, the molar ratio of acetic acid to octanol, the amount of catalyst, the reaction temperature and time. Through a series of evaluation we conclude that the suitable conditions for the catalytic esterification of tungsten silicate is that ratio of acid to alcohol is 1.3:1, the amount of catalyst 0.2g/0.1mol octanol, reaction time for 1H, reaction temperature is 100~118°C. Under this condition, the esterification rate can reach 99.30%.

Tungsten silicate has good catalytic activity in the synthesis of octyl acetate, it has short reaction time, high esterification rate, no waste acid discharge, simple process, the catalyst can be reused, therefore, tungsten silicate is an excellent catalyst for the synthesis of octyl acetate, it has a good prospect of industrial application.

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Single Layer Tungsten Disulfide Challenge Graphene (1)

Graphene, also called monatomic graphene, is a quasi two-dimensional material with only one atomic layer.

Graphene is one of the newest, most powerful, conductive and thermal conductive materials. The "king of transistors" that is expected to replace silicon in the future. Since the first two-dimensional material graphene was discovered in experiments, two-dimensional electronic materials have been studied for more than 10 years. Two dimensional materials are the thickness of only one atom, also known as a single layer of material, they are several hundred times smaller than the thickness of a sheet of paper. Nano monolayer two tungsten sulfide is also a two-dimensional material, moreover, in the field of semiconductor transistors, single layer two tungsten disulfide has a functional advantage that graphene does not have.

single layer two tungsten sulfide image

Transistors refer to all single elements based on semiconductor material. In a transistor, electrons pass from one end (S) to the other via a channel (D), when the process is complete, the delivery of information is complete. Because the speed of electrons is limited, in modern transistors, they usually run at saturation speed, so the time required is basically determined by the length of the channel. The shorter, the faster.

Now we are mainly producing silicon materials for transistors. In the micron era, the smaller the transistor size, the smaller the channel length and the shorter the electron transmission distance. This represents the faster processor chips, higher integration rates, and lower cost.

But by 2005, Inter and AMD, two computer microprocessors, would no longer boost CPU frequency but switch to multicore architectures, as did the development of mobile microprocessors. The reason is that, first, Moore's law, the higher the processor frequency, the greater the power consumption, when the frequency reaches 5G, the computer is a big stove; Two is the silicon wafer size has reached the limit at 20 nm, reducing the most significance, that is, reducing power consumption, performance is very limited. Thus, since then, CPU turned to multi-core architecture optimization, which is later dual core, quad core, eight core CPU appear reasons.

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【Know Tungsten】Tungsten Powder Export

China is a dominant country of tungsten resources and tungsten powder export, and export control conditions of 4xy3, has canceled export quota in 2016 and transferred to goods of export license administration.

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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...