Ammonium Metatungstate Preparing WO3 Plate SCR Denitration Catalyst--Dry Powder Mixing Method

The main component of tungsten trioxide plate denitration catalyst is just similar to honeycomb denitration catalyst, both are based on vanadium pentoxide, tungsten trioxide as the main active substance, titanium dioxide as the carrier. Compared with cellular, it has a stronger capacity of ash anti-clogging, wear resistance, less consumption under dust and low pressure loss ect.; although its market share is only about 1/3 of the cellular, it will gradually expand with the further launch of high-dust flue gas denitration in China.

plate denitration catalyst

The process that dry powder mixing method prepares tungsten trioxide plate denitration catalyst is as follows:
1. Put the titanium dioxide powder, stearate acid, AK sugars, methyl cellulose into the kneader, stir for about 10 minutes;
2. Add pulp slurry and stir for about 10 minutes;
3. Add silica sol solution and continually stir for 10 minutes;
4. Add the lactic acid, ammonia, ammonium metavanadate and suitable amount of deionized water into the mixed solution prepared above, then stir for about 1 hour for sufficiently reacting;
5. Add glass fiber and tungsten compound containing with tungsten trioxide (ammonium paratungstate, ammonium metatungstate ect.), stirring for about 30 minutes to prepare a catalyst mud;
6. Forming to generate the wet catalyst;
7. Dry the catalyst at 100 °C to remove excess free water;
8. Roasting, the purpose of it is: at the same time titanium dioxide crystal transition does not occurred, decompose the organic matter and active ingredient precursors; studies have shown that the active ingredient precursors and organic substances are decomposed completely at 400°C, the polymerization of vanadium pentoxide has been improved as the temperature increasing, but the titanium dioxide crystalline transition may occur, thus will cause the properties of catalyst reduced; therefore, calcination at the proper temperature, we can finally get the best active tungsten trioxide plate denitration catalyst.

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Titanium Blast Furnace Slag Prepares Ammonium Metatungstate and Tungsten Trioxide Denitration Catalyst

Flue gas denitration refers to the reduction of NOx to N2, thereby removing NOx from the flue gas; it can be divided into wet and dry denitration method according to the press preparation process. Because of the high titanium content (about 20%), titanium blast furnace slag is often used in the preparation of titanium dioxide, and then as a carrier for preparing tungsten trioxide denitration catalyst.

blast furnace slag

The first one preparing method:
1. Crushing the Titanium blast furnace slag, adding the sulfuric acid for leaching out titanium dioxide, then get the solution filtered to obtain the residue and titanium-containing solution;
2. Add the burnability type porous catalyst carrier into the titanium-containing solution obtained in step 1 with stirring; besides, a basic compound is optionally added to adjust the pH value to carry out a hydrolysis;
3. Filtering, washing and drying the material after hydrolysis which is obtained in step 2 to generate the support partial titanate carrier;
4. Load precursor of tungsten source (ammonium paratungstate, ammonium metatungstate) and vanadium source (ammonium metavanadate) to the partial titanate;
5. Roasted to get the vanadium pentoxide-tungsten trioxide-titanium dioxide of SCR flue gas denitration catalyst.

The second preparing method:
1. The titanium blast furnace slag is crushed and then added sulfuric acid for the titanium dioxide leaching, finally filtered to get the residue and titanium-containing solution;
2. Add the burnability type porous catalyst carrier into titanium-containing solution under the condition of stirring, also a basic compound is added selectively to adjust the pH value for the solution hydrolysis, tungsten source precursor (ammonium paratungstate, ammonium paratungstate, etc.) is added during the hydrolysis process;
3. The materials after hydrolysis is filtered, washed and dried to get the get the partial titanate containing tungsten trioxide;
4. The product obtained in step 3 is calcined to generate the final product of vanadium pentoxide-tungsten trioxide-titanium dioxide SCR flue gas denitration catalyst; or calcine the partial titanate containing tungsten-supporting to prepare titanium-tungsten powder, then further loaded the precursor of vanadium source, firing again to prepare the vanadium-tungsten-titanium of SCR flue gas denitration catalyst.

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Ammonium Metatungstate Spray Dryer Wall Sticking Reasons and Solutions

Spray drying is a wide applied process in liquid process shaping and drying industry. It can be used to transform solution, emulsion, suspension and paste liquid into powder and granular solids. When the finished particle size distribution, residual moisture content, density and particle shape must meet with precise standards, spray drying becomes an ideal method. 

ammonium metatungstate

The types and reasons for wall sticking during spray drying were analyzed. There are three types of wall sticking: half wet materials, materials with low melting point, dry powder. The wall sticking of half wet materials is concerned to the structure, fixing and operation of spray drying tower and sprayer, the motion of hot air in tower. The melting sticking occurred when the melting point of materials is lower than the drying temperature. The wall sticking of dry powder is concerned to geometric figure of cyclone chamber, roughness of wall, velocity of air and static charge.

Ammonium metatungstate spray dryer wall sticking solutions include improve the structure and texture of drying tower, use the proper atomizer, proper installation of atomizer, proper operation process, etc.

1. Improve the structure and texture of drying tower. If the design of diameter of dry tower is smaller than the atomizer cone, it will cause a mass amount of wall sticking. In order to prevent wall sticking, the diameter of dry tower should be larger, thus the liquid material will fall down directly without making contact with wall of tower. But the diameter can not be too large because it will increase cost of equipment and occupied area, it also affects flow speed of hot air in the tower and drying quality.
2. Use the proper atomizer. Atomizer is also called nozzle, it is the key part of spray dryer. Its different structure affect the distribution of misty liquid, also diameter and property of micro grains.
3. Installation of atomizer. If there is only one atomizer in the dry tower, the axis of atomizer should be on the center line of tower. If there is more than one atomizer, then the nozzle of atomizers should not be face to face.
4. Proper operation process. For the pheumatic spray drying tower, the process parameter often refers to drying temperature, feeding velocity and pressure of nozzle. Drying temperature includes inlet air temperature and outlet air temperature. Increase inlet air temperature can promote liquid evaporation, which will solidify the liquid before it contacts the wall which will reduce the wall sticking waste rate and increase yield of product. Besides that, temperature also affects the diameter of grains. When the temperature is low, the grain size is bigger which will prolong the drying process. When the inlet air temperature stay the same, raise the outlet air temperature can reduce the temperature differences to fasten drying efficiency.
5. The movement of hot air in the dry tower. The movement of hot air in the dry tower affects wall sticking directly. When the total amount of inlet air stay the same, the proportion of the air for protection atmosphere and air for drying will affects the drying result. If the air is insufficient for drying, then the liquid will stick on the wall before getting dried.
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Ammonium Metatungstate Prepared by Electrodialysis Method

Ammonium metatungstate (AMT) is a tungsten compounds with high molecular weight and water-soluble, which is easily dissolved in water, the solubility of it can reach 100g/mL at room temperature. It can be prepared from the material of ammonium tungstate by the method of Bipolar Membrane Electrodialysis (BEMD).

AMT picture

Electrodialysis method uses the effect of electric field, makes water which is in the two sides of bipolar membrane dissociated into H + and [OH] - then directional moved to both sides of electrode, and entered into the liquid chamber (the salt chamber) and alkali chamber respectively. Electrodialysis method is widely used in the field of chemical, light, metallurgy, papermaking industry and so on.

The preparation process of AMT by the method of electrodialysis which is using ammonium tungstate or ammonium paratungstate as raw materials is performed as bellows:

1. Add ammonium paratungstate into anode chamber, when an electric current passes by, water dissociated into two forms--H+ and [OH]– and directional moved to both sides of electrode under the action of strong electric field, and then respectively enter the liquid chamber (the salt chamber) and alkali chamber;

2. H+ ions enter the salt chamber to combine with WO4- and then will not go into alkali chamber ever again; ammonium ions move to cathode chamber through the exchange membrane, thus cause the concentration of ammonium metatungstate increased;

3. OH- moves into alkali chamber through the anion exchange membrane to combine with ammonium ions which is continually moved in and no longer went into the anode chamber;

4. With the process of electrolysis carrying out, ammonium ions decreased and hydrogen ions increased continually in the salt chamber, thus cause the pH value of the solution in salt chamber decreased continuously;

5. Finally, ammonium metatungstate solution is released from the cathode chamber, and AMT generated.

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Ammonium Metatungstate for WO3-Based Oxidative Desulfurization Catalyst

Oxidative desulfurization process consists of two steps: Firstly, oxidize the organic sulfur compounds in the oil into polar sulfone substance; secondly, separate the sulfone substances to achieve the purpose of desulfurization by adsorption, extraction and distillation methods s. Wherein the transformation of sulfone substance is the key step.

Sulfone is a group organic compound which contains sulfonyl, and often combined S with two carbon atoms (e.g. two hydrocarbons or simple divalent), generally the stable crystalline compounds, can be generated by the oxidation of organic sulfides or other methods.

WO3 desulfurization catalyst photo

Supported WO3-based oxidative desulfurization catalyst is achieving deep desulfurization by the oxidation catalyzed reaction of organic peroxide and sulfur heterocyclic aromatic compounds under mild conditions. The preparation program is under a hydrogen atmosphere or an inert gas atmosphere, plasma treatment supported tungsten trioxide based catalyst.

Preparation process are as follows:
1. The equal volume dipping method to prepare supported WO3/SiO2 catalyst: Weigh 0.852g of ammonium metatungstate and dissolved in 9ml of dubbed deionized water to form a solution and dripped drop by drop into the 3g silica with stirring;
2. Static in the room temperature for 12h, and then dried at 120°C for 4 hours;
3. Raise the temperature by the rate of 2V/min to 500 ° C, calcined for 5 hours to obtain the tungsten trioxide silica supported catalyst, wherein the loaded tungsten trioxide amount is 20% of the mass fraction of (of the total catalyst mass meter);
4. Under Ar atmosphere, treating the WO3/SiO2 catalyst with plasma;
Put 2mL of catalyst in the dielectric barrier discharge plasma reactor; control the Ar gas flow rate at 100mL/min under normal pressure; discharge frequency of plasma is about 10kHz; the input voltage of 50 volts; the input power of about 15 watts for 30min, and then get the supported WO3-based oxidative desulfurization catalyst.
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Ammonium Metatungstate for Tungsten Trioxide Based Ultra-Strong Acid Desulfurization Catalyst

The sulfide in the In the fuel will unavoidable release into the air in the form of gas when in the combustion process, which will probably causes a series of issues that destroying ecosystems like acid rain, damaging buildings. As the improving of people's awareness of environmental protection and vehicle fuel emission standards, increasingly strict restrictions on the sulfur content of fuel oil index has been worked out, therefore, the production and using of ultra-low sulfur fuel oil is imperative. In deep desulfurization, the application of traditional method of hydrodesulfurization (HDS) has been limited, because of its disadvantages such as harsh reaction conditions, equipment investment and higher operating costs.

desulfurization catalyst picture

Oxidative desulfurization is using an oxidizing agent to oxidize the sulfur compounds like thiophene in the fuel which are difficult to remove to sulfoxide or sulfone sulfur-containing materials with stronger polar in normal temperature, pressure and the presence of catalyst conditions, and then removing the sulfoxide or sulfone sulfur-containing materials by the methods like extraction, thus to achieve the goal of deep desulfurization. Oxidative desulfurization is considered to be a very attractive desulfurization technology, which usually consists of two steps: first, the fuel sulfide oxidation; second, removing the oxidized sulfur compounds from fuel oil by extraction, adsorption and distillation methods.

 The key of desulfurization method is developing an oxidative desulfurization catalyst with good properties of high desulfurization rate, oil yield, and low cost. Research indicates that a kind of zirconium hydroxide as a carrier, then immerse in the aqueous solution constitute of ammonium metatungstate after finely crushed; the immersion liquid placed in an ultrasonic generator ultrasonic to promote the dipping, evaporating the water, dried, and roasting at the high temperature to generate the WO3/ZrO2 solid ultra-strong acid desulfurization catalyst. This catalyst exhibits good activity and selectivity, and high desulfurization rate when used for the deep desulfurization of diesel fuel.
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Ammonium Metatungstate for Tungsten Trioxide Based Ultra-Strong Acid Desulfurization Catalyst

The sulfide in the In the fuel will unavoidable release into the air in the form of gas when in the combustion process, which will probably causes a series of issues that destroying ecosystems like acid rain, damaging buildings. As the improving of people's awareness of environmental protection and vehicle fuel emission standards, increasingly strict restrictions on the sulfur content of fuel oil index has been worked out, therefore, the production and using of ultra-low sulfur fuel oil is imperative. In deep desulfurization, the application of traditional method of hydrodesulfurization (HDS) has been limited, because of its disadvantages such as harsh reaction conditions, equipment investment and higher operating costs.

desulfurization catalyst picture

Oxidative desulfurization is using an oxidizing agent to oxidize the sulfur compounds like thiophene in the fuel which are difficult to remove to sulfoxide or sulfone sulfur-containing materials with stronger polar in normal temperature, pressure and the presence of catalyst conditions, and then removing the sulfoxide or sulfone sulfur-containing materials by the methods like extraction, thus to achieve the goal of deep desulfurization. Oxidative desulfurization is considered to be a very attractive desulfurization technology, which usually consists of two steps: first, the fuel sulfide oxidation; second, removing the oxidized sulfur compounds from fuel oil by extraction, adsorption and distillation methods.

 The key of desulfurization method is developing an oxidative desulfurization catalyst with good properties of high desulfurization rate, oil yield, and low cost. Research indicates that a kind of zirconium hydroxide as a carrier, then immerse in the aqueous solution constitute of ammonium metatungstate after finely crushed; the immersion liquid placed in an ultrasonic generator ultrasonic to promote the dipping, evaporating the water, dried, and roasting at the high temperature to generate the WO3/ZrO2 solid ultra-strong acid desulfurization catalyst. This catalyst exhibits good activity and selectivity, and high desulfurization rate when used for the deep desulfurization of diesel fuel.
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