DE102004033621A1 - Preparation of crystalline photo-catalytic titanium dioxide sol/gel, useful for spraying coating surfaces, comprises diluting titanium complex in acidic liquid; adding ammonia water; purifying; deforming; and adding oxidizing agent - Google Patents

Abstract

Titanium dioxide for photocatalysts is usually obtained by chemical synthesis. Often the titanium dioxide is ground. Neither the desired particle size nor the required crystal structure can be guaranteed. The product is therefore usable only for dyes, cosmetics and the like. A photocatalytic effect can not be determined. DOLLAR A Based on titanium complexes, titanium hydroxide or titanic acid is produced by dissolving, diluting, neutralizing and purifying in defined acids and then converted into crystalline nanoparticles of sol / gel particle size, which has photocatalytic and self-cleaning properties. In addition, there is still a deformation and a forming process. DOLLAR A The product thus produced is suitable for the spray coating of surfaces which are intended to be dirt-repellent and self-cleaning.

Description

BACKGROUND OF THE INVENTION

Field of the invention

The The present invention relates to photocatalysts and more particularly to a Method for Synthesis of Photocatalytic Titanium Dioxide Sol / Gel with particle sizes in the nanometer range. The titanium dioxide prepared by the process described herein Sol / gel becomes diverse used, e.g. For electrical household appliances, Lighting Equipment Air purifiers, Kitchen appliances, Bathroom facilities, Exterior walls, furniture, automotive interiors, as well Wastewater and waste air treatment plants. In the present invention Chemical processes are used to solubilize titania sol / gel solution a particle size of 2 nm to obtain 50 nm at a titanium dioxide content of 0.5% to 10%.

since In the seventies of the twentieth century arose size Number of documents over Methods for producing semiconducting titanium dioxide. In most These documents are normal chemical products, in particular Titanium dioxide particles, named as starting material. They are both the photochemical as well as the semiconductor-physical reactions described. Sequence and efficiency of reactions are determined by crystal structure and particle size.

As from the published According to documents, titanium dioxide is known by most Process for the preparation of titanium dioxide photocatalysts by gained chemical synthesis. In a not inconsiderable Number of cases The titanium dioxide is ground (e.g., in the P-25 milling process of Degussa Co.). With this method you can but neither the desired uniformity the particle size (10 nm to 500 nm), yet the required crystal structure can be guaranteed. The product is therefore for Dyes, cosmetics, correction fluids and the like used. A photocatalytic effect can not be determined. Also Process improvements, such as ultrasonic milling, ultrasonic vibration and grind with support by acidic liquids, which leads to an improvement in size and uniformity lead the titanium particles, are limited in their effectiveness because they do not make the crystal structure crucial can improve. The Product usability remains limited.

The The most widely used chemical synthesis method is liquid synthesis. The prior art is chemical vapor deposition (CVD), in which a photocatalytic titanium dioxide film of high stability and purity arises. The manufacturing costs are high and therefore only for special applications justified. The method is not suitable for mass production.

at liquid synthesis one differentiates between methods with organic solvents and Water-based methods. For the production of titanium dioxide photocatalysts become methods Water-based preferred.

at the methods with organic solvents Ti-oxyalkyl [Ti (OR) 4] is used with various solvents, as that ever after the heating process titanium dioxide powder or a titanium dioxide film is formed. One of these conventional methods is in Japanese Patent. 4-83537, in which Ti-oxyalkyl in ethylene glycol is heated, described. In Japanese Patent No. 7-10037 will Ti-oxyalkyl heated in aminoalcohol to obtain titanium dioxide. There Ti-oxyalkyl is expensive and the process at high temperature and be carried out under high pressure must be the products thus produced mostly as catalysts in industry and not used in the general area.

The Water-based synthetic methods are mostly in Japanese patents or reports, such as in Japanese Patent No. 7-171408. Here, a binder is added to a titanium tetrachloride solution and the whole thing heated. In Japanese Patent No. 6-293519 becomes a Titanium tetrachloride solution heated to a maximum pH of 3, resulting in the formation of a titanium dioxide Sol / gels leads. The disadvantage of this method is the high residual content of chloride, which makes the sol / gel unstable and easy to precipitate. In Japanese Patent No. 9-71418 hydrogen peroxide solution is added to titanium hydroxide. The pH is kept between 6 and 8 and the temperatures are lower. In Japanese Patent No. 62-252319, hydrogen peroxide solution is added Added titanium hydroxide. The pH is between 2 and 6, the temperature low and the reaction runs slowly. The particle size in the Titanium dioxide sol / gel prepared in this way is approx. 10 nm. Because the particles predominantly non-crystalline, the product is indeed for surface treatment however, is not an efficient photocatalyst. In Japanese Patent No. 7-28614 Pertitanic acid is heated and Japanese Patent No. 285993 hydrogen peroxide solution is added to titanium hydroxide and then raising the reaction temperature to titania sol / gel to create. The resulting products show the photocatalytic Effect. Due to the properties of the hydrogen peroxide is the concentration of titanium dioxide sol / gel is limited to values below 2%. This stands in the way of a general application.

In Taiwanese patent no. 135895 becomes one added organic acid to titanium tetrachloride and the whole heated to a temperature of at least 70 ° C, wherein sharp-edged titanium dioxide (anatase) is formed. The titania sol / gel produced in this way has the correct crystal structure and particle size, but a high content of chloride (more than 10 g / l), which has a negative influence on the stability.

in the Taiwanese Patent No. 349981 titanium tetrachloride reacts with aqueous ammonium solution at a pH between 2 and 6. The breakdown product (titanium hydroxide or titanic acid) is filtered and washed. After that it is at low temperature (5 ° C to 8 ° C) hydrogen peroxide added and stirred for a long time, non-crystalline titanium dioxide, which is not related with this invention is to disperse. In the Taiwanese patent No. Titanium sulfate is heated to 393342 to obtain titanium dioxide. After that becomes mono-protonic acid (eg nitric acid) added to remove sulfate residues and to dissolve the titanium dioxide so that smaller particles are formed. This procedure is also in unrelated to the present invention. The Taiwanese Patent No. 443992 describes a process for producing a titanium dioxide film in place a sol / gel. In the French Patent No. 2551743 produces alkaline earth titanium dioxide. This is for the present invention irrelevant.

SUMMARY OF THE INVENTION

The present invention relates to a method for producing nanometer-scale crystalline photocatalytic titanium dioxide sol / gel having the following steps:
Dissolving and diluting a titanium complex in a defined acidic liquid to obtain a dilute titanium solution.

Neutralize by adding ammonia water of a defined concentration to the diluted one Titanium solution, wherein a prescribed speed is maintained to to adjust the pH between 5 and 9.

Clean by filtering off the titanium hydroxide from the solution and washing the filter cake thus obtained.

strain by mixing the titanium hydroxide with deionized water and Agitate until a homogeneous mixing is achieved and subsequent addition of oxidizing agent or an inorganic acid.

formation the solution over a certain time at a defined temperature to a sol / gel.

attitude the pH of the sol / gel to the prescribed value, filter and packaging the sol / gel as a product.

The The method described in this invention avoids the disadvantages the synthesis based on an aqueous solution such as. the high chloride content, the low stability and the unsuitable crystallization mode. It therefore provides an applicable manufacturing method for photocatalytic Titanium Dioxide Sol / Gel with the process steps diluting, neutralizing, Change in appearance, Forming and packaging.

For the dilution process dilute hydrochloric acid is used, if titanium tetrachloride serves as starting material and dilute sulfuric acid at Titanium sulfate as starting material. The concentration of the acid is below 4 mol / l. The diluted one Titanium complex has a concentration of between 5% and 10% (weight). The agitation speed is between 30 l / min and 600 l / min and the temperature between 4 ° C and 30 ° C. The reaction time is 1 h to 4 h.

At the Neutralization process is the concentration of ammonia water (ammonium hydroxide) 10% to 25%. The feeding speed of ammonia water is 1 ml / min to 30 ml / min, depending on pH of the solution. While of the neutralization process is at a rate of 120 l / min to 1200 l / min agitated. The reaction time is 1 h to 4 h at a temperature of max. 20 ° C. The addition of ammonia water is stopped when a pH of 5 to 9 has been reached. In the neutralization process of the Titanium complex in the aqueous solution in titanic acid or titanium hydroxide, which are filtered out to a white powder to obtain. The filter cake is then at least five times Give amount of tap or soft water and agitate for a specific amount Time in it evenly distributed. After that, with a dehydrator, drained a compression filter, a vacuum filter or a centrifuge. This Cleaning process is repeated at least three times.

Thereafter, the filter cake is placed in deionized water and evenly distributed by stirring. Then, at least one defined oxidizing agent or at least one defined inorganic acid is added to initiate the strain-changing process. For this purpose, perchloric acid, periodic acid, potassium permanganate, sodium permanganate, nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, hydroiodic acid and hydrobromic acid are available. If the product is to be sprayed directly onto a surface, the oxidizing agents are preferred. If the target is a film or if a higher concentration is to be achieved in further steps, inorganic acids or a mixture of these and oxidizing agents is preferred. The amount to be added is 1 ml / l to 200 ml / l, the temperature is between 10 ° C and 95 ° C depending on the additive and the agitation speed is 30 l / min to 300 l / min for 10 min to 120 min. Depending on the product application and the environment, inorganic lye is selected. For the formation of the titania sol / gel is heated to 50 ° C to 95 ° C. Thereafter, it is filtered and packaged.

SHORT DESCRIPTION THE DRAWINGS

1 Block diagram of the synthesis of photocatalytic titanium dioxide sol / gel solution according to the present invention

2 Block diagram of the manufacturing process according to the present invention

DETAILED DESCRIPTION THE PREFERRED EMBODIMENT

1 shows the synthesis process for photocatalytic anatase titanium dioxide according to the present invention. The process comprises the following steps:
Dissolve and dilute a titanium complex in a defined acidic liquid to obtain diluted titanium solution (step 100 in 1 , or step 10 in 2 ).

Neutralize by adding ammonia water of a defined concentration at a defined rate to adjust the pH to 5 to 9 (step 120 in 1 , or step 12 in 2 ).

Purify by filtering out the titania from the solution and washing the titania filter cake (step 130 in 1 , or step 13 in 2 ).

Change in shape by administration of the titanium hydroxide in deionized water and agitation of the mixture until a uniform mixing is achieved, with subsequent controlled addition of oxidizing agent or inorganic acid (step 140 in 1 , or step 14 in 2 ).

Forming at a defined temperature for a given time to obtain sol / gel (step 150 in 1 , or step 15 in 2 ).

Adjust the pH of the sol / gel, filter and pack the final sol / gel as product (step 160 in 1 , or step 16 in 2 ). Hereinafter, some preferred embodiments of the present invention are described.

First preferred embodiment

10 One liter of deionized water is added to a 20L reaction tank filled.

The Agitation speed is set to 300 l / min. By a water bath, the temperature in the reaction tank is maintained at 5 ° C to 10 ° C. Then 500 g of 98% titanium tetrachloride are added at a rate of 4 ml / min with the aid of a metering pump. When all the titanium tetrachloride is added was, is still for 2 hours further agitated until the liquid clear and transparent. After that, at an agitation speed of 600 l / min of 20% ammonia water at a rate of 10 ml / min until a pH of 4 was reached. With a reduced rate of 2 ml / min to 4 ml / min will continue Ammonia water is added until the pH is between 7.5 and 8. The solution thus obtained is filtered with a vacuum filter. The titanium hydroxide containing Filter cake comes in a clean tank with 200 l content, in the previously 100 liters of tap or soft water were added. It will for 2 h agitated with 600 l / min until the filter cake evenly with Water was mixed. Thereafter, it is filtered off. This cleaning process becomes three times repeated. Thereafter, the filter cake is placed in the mold change and formation tank containing 20 liters of deionized water are located. The agitation speed is set to 300 l / min and it will be for Stirred for 1 h, so that one uniform mixing takes place. Now 50 ml of perchloric acid (HClO4) into the solution and for Stirred for 80 min. Thereafter, the temperature is at 80 ° C up to 90 ° C raised and for Stirred for 6 h. Then the temperature is lowered and the pH is adjusted. After that becomes the solution packaged as a product. The titanium dioxide obtained in this way Sol / gel is a colorless or yellow-transparent aqueous solution with a pH between 5 and 9. The proportion of titanium dioxide is about 1 % and the size of the needle or platelet-shaped crystalline Particle is between approx. 5 nm and 50 nm. It can be sprayed directly or be processed into a film and has self-cleaning properties. Under the influence of ultraviolet light, it has a sterilizing effect.

Second preferred embodiment

The process is the same as in the first preferred embodiment. However, instead of the perchloric acid (HClO4), 75 g of potassium permanganate (KMnO4) are used for the shaping process. The process conditions remain the same. The titania sol / gel prepared in this way is a yellow-transparent solution with a pH of between 7 and 9. The proportion of titanium dioxide is about 1% and the size of the needle-shaped or platelet-shaped crystalline particles is between about 5 nm and 30 nm It ent holds manganese, which has a cleansing and sterilizing effect. Since the content of potassium is very low, it is suitable for industrial use.

Third preferred embodiment

Of the Process is the same as in the first preferred embodiment, the amount of titanium tetrachloride is however increased to 2.5 l and for become the shape change process 150 ml perchloric acid (HClO4) used. The other conditions are identical to the first one preferred embodiment. The particles produced are the same as in the first preferred Execution, However, the proportion of titanium dioxide in the sol / gel is about 5%. Of the photocatalytic content is high. Except for the prevention of mold, Cleaning and sterilization can be the titania photocatalyst from this version for self-cleaning Walls and sanitary facilities be used.

Fourth preferred embodiment

Here 9 l of deionized water are added to a 20 l tank. The Agitation speed is set to 600 l / min. After that is 1 l of sulfuric acid added. This is followed by the addition of 400 g of titanium oxysulfate (TiOSO4). It is being continuously for Continue to agitate for at least 2 hours until everything has gone into solution. Then it will be Add 20% ammonia water at a rate of 10 ml / min. The other process steps and also the final product thus obtained are the same as in the first preferred embodiment.

Fifth preferred embodiment

Of the Process is the same as in the first preferred embodiment. Become for the shape change process but instead of perchloric acid (HClO4) 100 ml to 150 ml of phosphoric acid (H3PO4) is used and the forming temperature is increased to 90 ° C to 95 ° C, at a formation time of 8 h to 12 h. The thus produced photocatalytic Titanium dioxide sol / gel solution is colorless or yellow. The product is the same as the first preferred embodiment, However, because of its low phosphorus content even better cleaning effect.

Sixth preferred embodiment

Of the Process is the same as in the first preferred embodiment, with the difference that the Temperature during the formation is between 70 ° C and 80 ° C and the reaction time extended to 24 hours has been. The resulting photocatalytic titanium dioxide sol / gel solution is the same as in the first preferred embodiment.

Seventh preferred embodiment

Of the Process is the same as in the first preferred embodiment, in the shape changing process however, 10 ml of perchloric acid and 50 ml of phosphoric acid added, the forming temperature is increased to 90 ° C to 95 ° C and the reaction time is 6 h. The product is the same as that of the fifth preferred embodiment.

Eighth preferred execution

Of the Process is the same as in the second preferred embodiment, however, 80 become g potassium permanganate and in addition 150 ml of phosphoric acid added, the forming temperature is increased to 90 ° C to 95 ° C and the reaction time is 8 h. The product is the same as in the second preferred embodiment.

advantages the present invention, the self-cleaning effect, the Sterilization effect in combination with ultraviolet radiation and the good adhesion.

Claims (8)

A method for synthesizing crystalline photocatalytic titanium dioxide sol / gel with particle sizes in the nanometer range, which includes the following steps: Dissolve and Dilute of a titanium complex in a defined liquid acid to add diluted titanium solution receive; Neutralize by adding ammonia water with defined concentration and defined rate of addition to a pH between 5 and 9; Purify by filtration of the titanium hydroxide from the solution and washing the filter cake thus obtained; strain by mixing the washed filter cake with deionized water and agitate the mixture until completely homogeneous with subsequent addition oxidizing agent or inorganic acid; Formation at defined Temperature over a certain time to get sol / gel, adjust the pH, filter and pack as finished product. The method described under 1., in the titanium complex either titanium tetrachloride (TiCl4) or titanium oxysulfate (TiO (SO4)) chosen becomes. The method described in 1., in which hydrochloric acid diluted as liquid acid in the case of titanium tetrachloride and sulfuric acid diluted in the case of titanium oxysulfate, the acid concentration being less than 4 mol / l; the dissolved titanium complex has a concentration of 5% to 10% (weight); the rate of agitation is between 30 l / min and 600 l / min; the temperature is between 4 ° C and 30 ° C; the reaction time is between 1 h and 4 h. The method described in 1., in the the Concentration of ammonia water is between 10% and 25%; the feed of ammonia water depending on the pH of the solution between 1 ml / min and 30 ml / min is; the supply of ammonia water ends when a pH of 5 to 9 is reached; during the neutralization process agitated at a rate between 120 l / min and 1200 l / min becomes; the reaction time is between 1 h and 4 h. The method described in 1., in which the the solution precipitated Titanium hydroxide (or titanic acid) is filtered off and cleaned, wherein for filtering a dehydrator, Pressure filter, vacuum filter or a centrifuge can be used and wherein the filter cake thus obtained four to five times in the three to twenty times Lot of water washed, for Agitated 10 min to 120 min with 120 l / min to 1200 l / min and again is filtered off as well. The method described under 1., in which the filter cake in deionized water and mixed uniformly and then a selected Oxidizing agent or an inorganic acid for initiating a strain process is added; where at least one of the following substances selected becomes perchloric acid, periodic acid, Potassium permanganate, sodium permanganate, nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, hydriodic acid and hydrobromic; in which the addition amount is between 1 g / l and 200 g / l; the Temperature of the deformation process between 10 ° C and 95 ° C is; in which the agitation speed is between 30 l / min and 300 l / min at a reaction time of 10 minutes to 120 minutes. The method described in 1., in which the forming process in a Tank at a temperature between 50 ° C and 95 ° C and an agitation speed from 30 l / min to 300 l / min for 4 hours to 24 hours becomes. The method described under 1., in which the product depending on the application and need is packaged.