2019年12月23日星期一

Cyclohexanone Catalytic Reaction by Sodium Tungstate and Hydrogen Peroxide Mixed

Cyclohexanone is an important chemical raw material, widely used in fibers, synthetic rubber, industrial coatings, pharmaceuticals, pesticides, organic solvents and other industries.

Cyclohexanone is the main intermediate for the synthesis of caprolactam and adipic acid, and it is also a raw material for the preparation of spices, rubber antioxidants, adhesives, vinegar and fruit preservative phenolic phenol, and can also be used as fine chemical auxiliaries.

cyclohexanone production plant image

The traditional way to produce cyclohexanone is to produce cyclohexanol by hydrogenation of cyclohexanol, and then to reduce the cyclohexanol to the ring chamber by chemical method. There are two conventional preparation methods: One is in zinc catalyzed by 400 to 500 °C under oxidative dehydrogenation to cyclohexanone; The other was prepared by adding chromic acid catalyst with bleaching powder as oxidizing agent under weak acid condition. Among them, there is a problem, that is, there is no ideal catalyst, or the reaction conditions are harsh; or chromic acid is a toxic carcinogen, polluting the environment.

With the further study of sodium tungstate, the scholars found that the synthesis of adipic acid with cyclohexanone can be successfully catalyzed by sodium tungstate and hydrogen peroxide, scholars try again, using sodium tungstate as the main compound of hydrogen peroxide (H2O2), adding oxalic acid or phosphomolybdic acid and other acidic oxidant, made of tungstate compound catalytic agent. Through the catalysis of sodium tungstate composite catalyst, the synthesis process of the ring tunnel is quite smooth, the conclusion is that when the reaction temperature is 80 °C and the reaction time is 6h, only a small amount of tungstic acid compound catalyst mixture is used, the cyclohexanone yield is 98.2%, and the efficiency is 20% higher than the traditional chromic acid oxidizer.

Practice has proved again that sodium tungstate and hydrogen peroxide mixture can not only catalyze the synthesis of adipic acid from cyclohexanone, it also catalyzes the synthesis of cyclohexanol by cyclohexanone and may be a good catalyst for this type of chemical material, the most important thing is that sodium tungstate combined with hydrogen peroxide is not only effective, but also environmentally friendly, and can provide a better production environment for enterprises and society.

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Tin Removal From Waste Tungsten Alloy Recycle

With the shortage of tungsten ore resources, the utilization of tungsten resources becomes more and more urgent.

Waste tungsten alloy is one of the main sources of tungsten recovery, according to statistics, about 35% of the tungsten in Europe and America developed from waste tungsten alloy recycling. With the emphasis on tungsten resources in China, the recycle rate of tungsten resources in China has been increasing year by year, and it has reached 20%.

In the tungsten recycling process, the sodium carbonate melting method of waste tungsten recycle process technology is more mature and wide applicability of the program, but it is inevitable that the leaching process in recycling of waste tungsten, scrap tin, phosphorus, chromium, molybdenum and other impurities may also enter coarse sodium tungstate solution, thus affecting the purity of tungsten products. The main impurities of the waste alloy are different, the treatment method varies according to material, here to introduce tin removal from crude sodium tungstate solution method of tin rich impurities.

 impurities removal in sodium tungstate solution image

In the alkaline process, the purification of sodium tungstate from waste alloy is usually made by magnesium ammonium phosphate method or phosphorus arsenic magnesium salt method. In the impure sodium tungstate solution, a small amount of soluble magnesium salt is added to produce ammonium phosphate, and generated magnesium salt or phosphorus arsenic magnesium salt, so as to remove arsenic and phosphorus.

In the impure sodium tungstate solution, a small amount of soluble magnesium salt is added to produce ammonium phosphate, magnesium salt or phosphorus arsenic magnesium salt, so as to remove arsenic and phosphorus. In the process of pH, silicon can simultaneously remove from the solution, but it can not effectively remove tin and tin, the best filtering stage only in the crude sodium tungstate solution phase, the follow-up process is very difficult to deal with.

For the treatment of tin in crude sodium tungstate solution from waste tungsten alloy recycle, some foreign scholars have proposed the scheme, which can be roughly divided into four stages. (1) Adding ammonium or hydrogen hydroxide to sodium tungstate solution. (2) Adding sulfuric acid, transfer PH to 9.5-10 and stir for half an hour. (3) Adding magnesium chloride into the solution which has been ammoniation and adjusted the pH value, and then the mixture is stirred for a period of about 12 hours to form a slightly soluble tin, arsenic, phosphorus and silicon compounds. (4) Stand aside for about 3 hours. A substance containing tin compounds can be precipitated.

When the insoluble substance is removed, the filter can be used to filter the insoluble matter in the solution and to obtain the purified solution containing tungsten, the content of tin obtained by the purified solution can reach or better than the purity of APT - 0, and it is very economical and feasible to evaluate the content of the waste alloy by the recycling standard of APT.

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Sodium Tungstate Preparation From Scheelite Slime Recycle

Sodium tungstate is an important chemical raw material and an important intermediate product in tungsten metallurgy production.

Generally speaking, industrial production of sodium tungstate mainly uses scheelite concentrate or wolframite concentrate as raw material, and the production cost is higher.

In the tungsten concentrate production process, there are often some tungsten due to process or equipment reasons, lead to part of the tungsten ore grinding machine into powder or no successful flotation into the tailings, forming tungsten fine mud.

scheelite slime recycle image

The conventional recycle process of tungsten slime is tungsten slime - sodium tungstate - ammonium paratungstate. How can the sodium tungstate be recycled more efficiently by using tungsten slime? Compared with wolframite, fine scheelite slime is characterized by lower grade, more impurities, and more calcium containing molybdenum, which is more difficult to purify. In view of the above, we can use hot ball milling alkali decomposition ion exchange APT evaporation crystallization process. It has a strong adaptability to high calcium and low grade ore. It has three main stages:

1. The tungsten fine slime is decomposed by alkali method and hot ball milling, and most impurities are inhibited in the slag, so that the WO3 is transferred into the solution to produce sodium tungstate solution, and most of the impurities (P, As, Si, etc.) are left in the slag. 

2. The obtained sodium tungstate solution is evaporated and crystallized at once, and to recycle the alkali and remove impurities such as P, As, Si etc..

3. Sodium tungstate crystals were dissolved and filtered to obtain sodium tungstate solution. Unlike the sodium tungstate solution obtained from the scheelite concentrate, there is more molybdenum in sodium tungstate solution. The main work of this stage is to remove the molybdenum, can be selected by ion exchange or selective precipitation of tungsten and molybdenum separation. The sodium tungstate solution after molybdenum can be obtained by two times evaporation and crystallization, and can be converted into ammonium tungstate solution by ion exchange method, and then APT is prepared.

4. The above process can effectively deal with low grade and scheelite fine slime containing calcium and molybdenum. Some data show that the process of recycling scheelite fine slime from ore in Hunan, China, has a total recovery rate of 60-70%, and the effect is very good. Moreover, from the cost point of view, the majority of tungsten slime, according to WO3 measurement, the cost is only 60%-70% of the concentrate price. The recycle of tungsten slime is an effective way to reduce the cost of mining and prolong the mining life of the mine.

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2019年12月11日星期三

Chromium Removal From Waste Tungsten Alloy Recycle

With the shortage of tungsten ore resources, the utilization of tungsten resources becomes more and more urgent. Waste tungsten alloy is one of the main sources of tungsten recycle.

According to statistics, about 35% of the tungsten in Europe and America developed from waste tungsten alloy recycling. With the emphasis on tungsten resources in China, the recycle rate of tungsten resources in China has been increasing year by year, and it has reached 20%.

In the waste recycling process of tungsten alloy technology, recycle process of waste tungsten by sodium carbonate smelting process is relatively mature and widely applicable, much as it is used, but a lot of problems also appeared in the actual production, the most troublesome is chromium. During the leaching of waste tungsten alloy by sodium carbonate smelting process, a large amount of chromium impurity elements also enter into sodium tungstate solution, which can not meet the purity of tungsten products.

waste tungsten alloy image

The chemical properties of chromium show that the precipitation of chromium from sodium tungstate solution requires the reduction of Cr6+ to Cr3+, this process can be done by acid and alkali, but in the current industrial atmosphere, the alkaline process has the mass base.

If you want to remove chromium, you have to do it once more, removing impurities is necessary. In general, sodium tungstate crystals need a series of procedures, such as dissolution neutralization purification, removal of sulfide, acid extraction, extraction stripping, APT crystallization, etc.. Some experts believe that the removal of chromium during the curing stage is a wise choice, this is mainly the curing process can be carried out with the removal of chromium and molybdenum removal, this is less than the two stages of reduction, hydrolysis and filtration in the dissolution stage of crude sodium tungstate;

In the process of removing chromium by vulcanizing stage, sodium sulfide 4 times of theoretical quantity is added into the present process of molybdenum removal by sulfuration, besides, the chromium removal was controlled when the reaction pH value was 8-9, by selecting suitable temperature and aging time, better chromium removal effect can be achieved, moreover, it is necessary to add a filtration process on the basis of the original production process to accomplish the task. More importantly, in the curing stage, the APT obtained from chromium treatment can basically achieve the purity of APT - 0. From the recycling standard of waste alloys, this should be a very good result.

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Sodium Tungstate Is Expected To Be a New Drug For Reducing Blood Lipids

Sodium tungstate is a kind of tungstate, and its chemical formula is Na2WO4.

In nature, sodium tungstate appears to be colorless crystalline or white crystalline powder, and sodium tungstate is now known to replace sodium vanadate in the treatment of diabetes. However, with the study of sodium tungstate in the field of medical treatment, some American scholars have suggested that sodium tungstate can also be used to treat hyperlipidemia and obesity.

Hyperlipidemia refers to the high level of blood lipids, can directly cause some serious harm to human health diseases, such as atherosclerosis, coronary heart disease, pancreatitis and obesity, this symptom is more common in the United States, which is related to diet. In medicine, high blood lipids are caused by elevated levels of triglycerides (TG) and total sterols (CHO) in the blood.

drugs image

In order to investigate the possibility of sodium tungstate in the treatment of hyperlipidemia, Chinese medical workers were tested with mice. During the course of the experiment, using poloxamer 407 intraperitoneal injection of rodents caused by elevated blood lipids, obtained hyperlipidemia animal model. Then the mice were divided into 4 groups, which were treated with ionized water, 100mg/Kg sodium tungstate, 200mg/Kg sodium tungstate and bezafibrate tablets (for the treatment of hyperlipidemia). By contrast, the researchers found that sodium tungstate had a hypolipidemic effect on hyperlipidemic Kunming mice, which significantly decreased the levels of serum total cholesterol (CHO) and triglyceride (TG) levels, lipid cholesterol (HDL-CHO) was elevated at the same time as the ester, and the effect of sodium tungstate was better than bezafibrate at 200 mg / kg.

The results showed that sodium tungstate had a hypolipidemic effect on hyperlipidemia, which could significantly reduce the level of serum total cholesterol and triglyceride, and balance the level of high density lipoprotein (HDL). Although sodium tungstate is currently in experimental phase, there is no doubt that sodium tungstate has the potential to develop new lipid-lowering drugs. As we all know, the formation of high blood fat is related to obesity, and the decrease of blood lipid often indicates the success of weight loss, in addition, hyperlipidemia is often associated with diabetes and hypertension. In the future, sodium tungstate can become a new blood lipid lowering drug which can control diabetes and control hyperlipidemia, it may reduce the pain of many patients.

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Sodium Tungstate Can Also Treat Diabetes

Sodium tungstate is a kind of tungstate, and its chemical formula is Na2WO4.

In nature, sodium tungstate is a colorless crystalline or white crystalline powder, and is often used as a plant protection, metal corrosion inhibitor and photocatalytic agent because of its non-toxic and environmental advantages. But is rarely known by people that sodium tungstate can also be used to treat diabetes.

Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia. Hyperglycemia is caused by insulin secretion defects or impaired biological effects, or both. The consequences of diabetes are easy to cause eye, kidney, heart, blood vessels, nerves of chronic damage, dysfunction, such as high blood pressure, stroke, etc., is a healthy killer of middle-aged and elderly people. The traditional compound for the preparation of diabetes is vanadate, which is a simple inorganic vanadium compounds such as sodium vanadate, vanadyl sulfate etc.. Vanadium insulin has been widely used for many years to alleviate the incidence of diabetes and improve the physical condition of the diabetic and mimic the physiological function of insulin, however, vanadium has low toxicity, and long-term use of drugs will inevitably harm the liver, kidney and other organs.

sodium tungstate in the treatment of diabetes image

Many studies have found that sodium tungstate, like vanadate and other trace elements, can promote the synthesis and accumulation of glycogen, promote glycolysis and inhibit gluconeogenesis.

There were medical workers using sodium tungstate and sodium vanadate to compare tests, in animal studies, sodium tungstate can reduce normal blood glucose levels in type 1 and type 2 diabetic rats without causing hypoglycemia, even after a considerable period of withdrawal, the blood glucose levels of the treatment group remained normal or lower than the sodium vanadate control group. Although sodium vanadate has good hypoglycemic effect, but after a period of withdrawal, blood glucose levels rose earlier in animals treated with sodium vanadate. More importantly, although sodium salts are similar in biological properties to vanadate and other trace elements, sodium tungstate is less toxic and highly bioavailable.

Based on the above factors, it can be predicted that tungstic acid has more broad prospects for the prevention and treatment of diabetes than other trace elements, in the near future, with the end of clinical trials, sodium tungstate will bring the gospel to more diabetic patients.

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What You Don't Know About The Applications of Sodium Tungstate

Sodium tungstate is a kind of tungstate, and its chemical formula is Na2WO4.

The appearance is colorless crystalline or white crystalline powder, soluble in water, insoluble in ethanol, slightly soluble in liquid ammonia, when confront a strong acid it is broken down into tungstic acid dissolved in water.

Sodium tungstate, as a raw material for chemical synthesis of tungsten, is an important intermediate in the transformation of tungsten into metals, usually, the intermediate product is broken down by alkaline process, and sodium tungstate is obtained, but in here sodium tungstate refers to crude sodium tungstate containing impurities. It also needs to be obtained by ion exchange, precipitation, extraction and other processes. Finally, APT is obtained by evaporation crystallization. Although sodium tungstate is an intermediate product of tungsten in the process of transformation, we use a lot of sodium tungstate, usually used in industrial products in tungstate refers to chemically pure sodium tungstate, sodium hydroxide is prepared by tungsten trioxide.

sodium tungstate image

Sodium tungstate is not only a chemical product, but also a high-quality semiconductor material. It can be used to control environmental pollution and manufacture new energy materials. The known applications are as follows:

1. Applied in the manufacture of metal tungsten, tungstic acid, tungstate, etc..

2. Applied in mordant, analytical reagent, catalyst, water treatment chemicals, manufacturing fireproof, waterproof materials, as well as dodecatungstophosphate, borotungstate etc..

3. The compound of sodium tungstate and polyaspartic acid can be used as a metal corrosion inhibitor to prolong the service life of metals in corrosive environments such as sea water.

4. Textile agents used as a weighting agent for fabrics. This product is used as a fabric aid and consists of a mixture of sodium tungstate, ammonium sulfate, ammonium phosphate, etc., used for fireproofing and waterproofing of fibers. This kind of fiber can be made of fireproof rayon and rayon, can also be used for leather tanning.

5. The combination of sodium tungstate and hydrogen peroxide can effectively degrade dye wastewater methylene blue.

6. Sodium tungstate can optimize plant nitrogen absorption, improve fruit quality and avoid nitrogen loss.

7. Sodium tungstate can be used to adjust the absorption of NO3- N by Cassia albus, which increases the production of diesel fuel.

8. Sodium tungstate can be made into antifreeze by compounding, so as to prevent the tea plant from "cold disaster".

In addition, some scholars believe that sodium tungstate can promote islet cell proliferation, differentiation and secretion, reduce serum total cholesterol (CHO) and triglyceride (TG) level, and can be used as raw materials for the treatment of diabetes, can also be used for reducing blood lipid and weight loss.

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