Ammonium Metatungstate Prepares Tephra Contained Tungsten Trioxide Denitration Catalyst

Tephra is defined as the gravel and mineral particles which are erupted from a volcano and the granule less than 2 mm in diameter. At the explosive of the volcanic activity, the solid rocks and lava are broken down into the fine particles and formed to volcanic ash. In the mix materials of some pozzolana, there are active ingredients, such as a certain number of active silica, activated titanium oxide.

The coal takes the domination of China's energy structure, and one of the main sources of air pollution is the nitrogen oxide which is produced by the consumption of coal; the nitrogen oxide will not only cause acid rain, photochemical smog and other issues which damages to the global environment, but also seriously endanger human health. Conventional manufacturing of honeycomb catalyst is taking tungsten trioxide and nanoscale titanium dioxide as the main raw material, and mixing with water, binders, extrusion aid, reaming, lubricants, glass fibers and so on to fully kneaded to obtain a plastic pug, then extruded to wet honeycomb catalyst, finally get the molded catalyst after drying and calcining.

tephra and denitration catalyst

Study has found that the tungsten trioxide denitration catalyst containing tephra which the components include: nano titanium dioxide powder 72~81, volcanic tephra 5~15, ammonium metatungstate 0.9~3, ammonium metavanadate 0.7~2, monoethanolamine 2~6, carboxymethyl cellulose 2, Polyoxyethylene of 2, 1~3 lanthanum nitrate (Remarks: the unit is part). The preparation method is as follows:

1. Mix the monoethanolamine, deionized water and ammonium metavanadate together, and fully dissolved by heating and stirring to prepare a solution of ammonium metavanadate;

2. Respectively dissolve lanthanum nitrate and ammonium metatungstate in water at room temperature, continually stirring for 1 hour to obtain the solution of ammonium metatungstate and lanthanum nitrate;

3. Mix the tephra, nano titanium dioxide with deionized water, ammonium metavanadate and ammonium metatungstate solution, polyethylene oxide, lanthanum nitrate solution for high-speed mixing evenly, then standing for 1-12 hours to obtain pug;

4. Warmed and dried the pug;

5. Calcine the dried pug, which is obtain the tungsten trioxide denitration catalyst products containing tephra after calcined at a maximum temperature of 600°C for 30 hours.

Studies have shown that it can reduce the high amount of conventional titanium dioxide by adding volcanic tephra, thereby reducing costs; tungsten trioxide decomposed from the calcination of ammoniummetatungstate in the production process; the cost will be reduced, compared with directly using nanoscale titanium dioxide which containing tungsten trioxide as a raw material; the added polyethylene oxide in calcined product improving pore volume and distribution of the products, increasing the specific surface area, thus to effectively improve the denitration performance; therefore, we will know this kind of tungsten trioxide denitration catalyst containing tephra has a low manufacturing cost, high specific surface area of catalyst products, wide operating temperature, and has the advantage of good catalytic denitration performance at the same time.

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Ammonium Metatungstate Prepare WO3 Contained De-Dioxin and Denitration Catalyst

Dioxin refers to the collectively chlorine-containing organic compounds which contain one or two oxygen-bond connecting with two benzene rings, the carcinogen with most toxic, very stable and difficult to break down, besides, the dioxin has reproductive, immunity and endocrine toxicity. The main active ingredients of de-dioxin catalyst are titanium dioxide, vanadium pentoxide, tungsten trioxide, cobalt oxide and other transition metal oxides, or a noble metal (platinum, gold, etc.). The researches on an efficient, economic catalyst with both functions of de-dioxin and denitration catalyst is very necessary.

honeycomb denitration catalyst

Waste hydrodesulfurization catalyst generated by the refinery contains a lot of metals, such as aluminum, tungsten, nickel, cobalt, vanadium, which is a relatively inexpensive resource. The recycling of it can not only recycle the useful resources, but also reduce the environmental pressure, and thus become a hot topic. Experiments have shown that the waste hydrodesulfurization catalyst can be used to prepare tungsten trioxide contained of de-dioxin and denitration catalyst, and prepared as follows:

1. Waste hydrodesulfurization catalyst is carried out a pretreatment by washing with deionized water and drying;

2. Mix the carrier-titanium dioxide and the active ingredient-tungsten trioxide. The ammonium metatungstate and titanate are mixed according to mass ratio of 1: 9 to give a suspension, then filtered and the wet powder is calcined, to obtain the titanium dioxide loading with tungsten trioxide;

3. Ball grinding to mix the waste hydrodesulfurization catalyst and the carrier to obtain a raw material mixed powder, adding oxalic acid (or citric acid) and water to mix uniformly at the same time;

4. Dry and calcine the semi-finished products o give the finished-products--tungsten trioxide catalyst with the function of both de-dioxin and denitration.

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Ammonium Metatungstate for Tungsten Trioxide Denitration Catalyst with Dioxin Removable

Dioxins are a class of substances with persistent pollution, with its highly toxic, the small amount of them can cause serious damage to health or fatal, so they has become the focus of public attention in recent years. Dioxins are very stable compounds, which appear in a colorless solid at room temperature; it will accumulate in fat after entering human body with its high lipophilicity; In addition, it is extremely difficult to remove once the pollution occurs, because the strong bond between it and the soil or other particulate material.

de-dioxin and denitration catalyst

The most effective way to remove dioxins is still the selective oxidation-reduction, experimental proposed a preparing method of tungsten trioxide denitration catalyst which with dioxin removable; also the anti-sulfur poisoning is improved, and possess the good catalytic activity at the same time. It is prepared as the follow steps:

1. Successively add the equal amount of titanium dioxide powder and carbon nanotubes into the dilute ammonia to form the carrier mixture with stirring well, then transferred to the ultrasonic cleaning machine for an ultrasonic treatment;

2. Dissolve ammonium metavanadate, ammonium sulfate, ammonium metatungstate in the dilute aqueous ammonia in turns to form of a mixed solution of the active ingredient, then thoroughly stirred under heating, transferred into a rotary evaporator furnace for drying to give a mixture of the active ingredient;

3. Successively add the active ingredient mixture, glass fiber, cellulose and polyacrylic acid  into the mixed carrier to form a catalyst mixture, heat with stirring to dry and stop until the catalyst mixture of a moisture content of about 30%;

4. Get the tungsten trioxide denitration catalyst products with dioxins removable by extruding, drying, calcining the catalyst mixture.

This kind of catalyst is constituted by the following components: 1.2% of vanadium pentoxide, 7% of vanadium oxide sulfate, 1.5% of tungsten trioxide, 2.5% of glass fiber, 1.5% of polyacrylic acid cellulose, 1.1% of cerium sulfate, 14% of manganese sulfate, the rests are carriers (titanium dioxide and carbon nanotubes with the mass ratio of 1:1).

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Ammonium Metatungstate for Diesel Engined Car Exhaust WO3 Denitration Catalyst

Oxide catalyst is mainly the vanadium based catalyst, and adding co-agents like tungsten trioxide, such kind of catalyst has a high NOx removal efficiency in the temperature range of 300-400°C with excellent stability. In the past, the catalyst of diesel engined car exhaust is primarily the noble metal catalyst, but its application is limited by high cost. An invention has pointed out that a method for preparing the diesel engined car exhaust tungsten trioxide denitration catalyst which has a high catalytic activity, wide temperature window, as follows:

diesel engined car exhaust WO3 denitration catalyst

1. Calcine carrier of the titanium dioxide at 300-400°C for 2-5 hours;

2. Preparation of the active ingredient solution: dissolve the ammonium metavanadate and ammonium metatungstate in deionized water, then add the appropriate amount of oxalic acid solution and uniformly stirred, to obtain the active catalyst component solution;

3. Impregnation method to load the active component: The carrier is immersed in the calcined active component solution prepared in step 2;

4. Natural drying the catalyst obtained in step 3, then transferred to drying conditions at 80~120°C for 8~12 hours;

5. After drying, the catalyst is calcined at 300~600°C for 2 to 5 hours, then heated to 680-800°C and continually calcined for 2 to 5 hours to obtain the tungsten trioxide denitration catalyst which is suitable for diesel engined car exhaust.

Noted: wherein the carrier is titanium dioxide which takes 90-99.5% of the mass of catalyst; the main active component vanadium pentoxide takes 0.5-10%; additive- tungsten trioxide takes 0.5-10%.

The preparation method of this catalyst without introducing any chemical agent, just by changing the preparation process; by changing the calcining temperature to improve the distribution of the active component in the catalyst support surface, has the advantages of simple operation, excellent repeatability, easy to optimize the size and modifying the conventional catalyst.

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