MXPA02006924A - Method of preparing compounds using cavitation and compounds formed therefrom. - Google Patents

Abstract

Nanostructured materials and processes for the preparation of these nanostructured materials with a high degree of phase purity using cavitation are described. Preferably, the method comprises mixing a metal containing a solution with an agent that precipitates and passives the mixture in a cavitation chamber. The chamber is made up of a first element to produce cavitation bubbles, and a second element that creates an area of sufficient pressure to collapse the bubbles. The process is used for the preparation of catalysts and piezoelectric and semiconductor materials.

Description

METHOD OF PREPARATION OF COMPOUNDS USING CAVITATION AND COMPOUNDS PREPARED FROM IT Data from the Related North American Application This application claims the priority benefit of the US Provisional Patent Application Serial No. 60 / 176,116 filed on January 14, 2000.

Description of the Invention Cavitation is the formation of bubbles and cavities within a liquid stream that results from a pressure drop located in the liquid flow. If the pressure at some point decreases to a magnitude below which the liquid reaches the boiling point for this fluid, then cavities and bubbles filled with steam are formed. As the liquid pressure increases, vapor condensation occurs in the cavities and bubbles, and they collapse, creating large pressure pulses and high temperatures. Cavitation involves the complete sequence of events beginning with the formation of bubbles until the collapse of the bubbles. Cavitation has been studied for its ability to mix materials and aid in chemical reactions. There are several different ways to produce cavitation in a fluid. For example, a propulsive blade moving at a critical speed through water can result in cavitation. If a sufficient pressure drop occurs on the surface of the blade, cavitation will result. Similarly, the movement of a fluid through a restriction such as an orifice plate can also generate cavitation if the pressure drop through the orifice is sufficient. These methods are commonly referred to as hydrodynamic cavitation. Cavitation can also be generated in a fluid by the use of ultrasound. A sound wave consists of compression and decompression cycles. If the pressure during the decompression cycle is sufficiently low, bubbles may form. These bubbles will grow during the decompression cycle and will contract or even implode during the compression cycle. The use of ultrasound to generate cavitation to improve chemical reactions is known as sonochemistry. U.S. Patents Nos. 5,810,052, ,931,771 and 5,937,906 to Kozyuk, all of which are hereby incorporated in their entirety for reference thereto, describe the improved device and the methods capable of controlling the many variables associated with cavitation.

Metal-based materials have many industrial uses. Relevant with the present invention are those solid state metal based materials such as catalysts, piezoelectric materials, superconductors, electrolytes, ceramic based products, and oxides for uses such as recording media. While these materials have been produced through normal co-precipitation media, U.S. Patents 5,466,646 and 5,417,956 to Moser describe the use of shear stress followed by cavitation to produce metal-based materials of high purity and improved nanosize. While the results described in these patents are improved over past methods of preparation, the inability to control the effects of cavitation limits the results obtained.

SUMMARY OF THE INVENTION One embodiment of the present invention is directed to a process for producing solid state materials based on metal of nanostructured size and with high phase purity using cavitation to create high shear stress and take advantage of the energy released during the collapse of the bubbles. The process generally comprises the steps of: mixing a metal-containing solution with a precipitating agent to form a mixed solution that precipitates a product; passing the mixed solution at elevated pressure and at a speed within a cavitation chamber, wherein the cavitation chamber has means to create a cavitation zone and means to control the zone, and where the cavitation of the mixed solution occurs, forming a precipitated product cavitated; removing the cavitated precipitated product and the mixed solution from the cavitation chamber; and separating the precipitated cavitated product from the mixed solution. The present invention preferably employs an apparatus for cavitation similar to the apparatus described in U.S. Patent No. 5,937,906 to Kozyuk. The present invention is particularly suitable for producing nanofase solid state materials such as metal oxides and metals supported on metal oxides. The synthesis of nanostructured materials with high phase purity is important to obtain pure metal oxides and metals supported on metal oxides for applications in catalytic and electronic processing and structural ceramics. The synthesis of such materials by cavitation results in nanostructured materials with high phase purity. Although it is not desired to limit by theory, it seems that the high shear force causes the multimetals to be well mixed leading to the nanostructured particles and with high phase purity, and the high temperatures in if you result in the decomposition of the metal salts in finished metal oxides or metals supported on metal oxides. The present invention can decompose at least some of the metal salts, and preferably all the metal salts. The present invention allows the formation of these materials frequently without the requirement of post-synthesis thermal calcination to obtain the finished metal oxides. Conventional synthesis methods require high temperature calcination to decompose intermediate metal salts such as carbonates, hydroxides, chlorides, etc. The ability to synthesize advanced materials by cavitation requires the equipment used to generate the cavitation to have the ability to vary the type of cavitation that is being instantaneously applied to the stream of the synthesis process. This "controlled cavitation" allows the efficient modification of the cavitation conditions to satisfy the specifications of the desired material to be synthesized. The importance of the method is a capacity to vary the size of the bubbles length of the cavitation zone, which results in a collapse of bubbles necessary to produce pure phase nanostructured materials. The desired type of bubble collapse provides a local shock wave and releases energy to the local environment through the walls of the collapsing bubbles which provide the shear stress and local heating required to synthesize pure nanostructured materials. The cavitation method allows precise adjustment of the cavitation type to synthesize pure metal oxide materials as well as metals supported on metal oxides, and suspensions of pure reduced metals and metal alloys. An additional capability of the method, which is important for the synthesis of materials for catalysts and advanced materials for electronics and ceramics, is the ability to systematically vary grain sizes by a simple alteration of the process conditions that lead to the cavitation Another aspect of the present invention is the formation of simple metal oxides to vary the grain sizes of 1-20 nm, and multimetal metal oxides to vary the grain sizes and as single phase materials without the presence of any of the components of Individual metallic oxide of the desired pure materials located on the surface of the desired pure material. In addition, synthesis of reduced metals supported on metal oxides in grain sizes of 1-20 nm and the ability to vary grain sizes between 1-20 mm is also possible. Due to these unique capabilities, compared to conventional synthesis methods, the methods and compositions formed with it function roughly as high quality catalysts, capacitors, piezoelectrics, novel titanias, metal oxides that conduct oxygen and electricity, fine grains of suspensions of finely divided reduced metals, and superconductors.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates the variation in voltage and grain size of a piezoelectric as a function of orifice size, - Figure 2 illustrates a XRD comparison of a piezoelectric prepared in accordance with the present invention and by the classic preparation, - Figure 3 illustrates the XRD of finely dispersed silver on aluminum oxide synthesized in accordance with the present invention; Figure 4 illustrates the effect of High Pressure versus Low Pressure in the cavitation process of the present invention on the synthesis of Figure 5 illustrates the effect of High Pressure versus Low Pressure in the cavitation process of the present invention on the synthesis of CUo, 22Z 0.68Ala.iOx with respect to [%] of Tension versus Crystalline Size in ntn; Figure 6 illustrates the effect of High Pressure versus Low Pressure in the cavitation process of the present invention on the distortion of the Cuo.22Zn0.63Al0.iOx framework as it relates to the C-axis versus orifice size; Figure 7 illustrates the relative Intensity of 2% Pd formed by the cavitation process of the present invention and calcined at 1095 degrees Celsius.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus used in the present invention consists of a pump for raising the pressure of the liquid that is fed into the apparatus, and a cavitation zone within the apparatus. The cavitation zone generally comprises a side-by-side flow channel having a flow area, internally containing at least a first element that produces a local constriction of the flow area, and having an outlet downstream of the local constriction; and preferably a second element that produces a second local constriction located at the outlet, where a cavitation zone is formed immediately after the first element, and a high pressure zone is created between the cavitation zone and the second local constriction. The liquid is preferably pressurized before entering the flow channel from side to side. A local constriction in the channel creates an increase in the speed of the liquid flow to some minimum velocity, creating a sufficient pressure drop to allow cavitation to occur. On average, and for most hydrodynamic liquids, the minimum speed is 16 m / sec. or older. The element or elements that produce the local constriction can take many different forms. They can be of the shape of a cone, or spherical or helical shape, or they can be located in the center of the flow channel. It is possible to use a crosshead, post, propeller, nozzle, or any other attachment that produces a minor loss of pressure. One or more holes or baffles are preferred. By varying the size of the hole, the apparatus is able to better control the size of the cavitation bubbles that are formed. The hole may have one or more circular, or grooved openings. The cavitation bubbles are then transported by the liquid flow immediately into a cavitation zone, comprising numerous cavitation bubbles. The cavitation bubbles flow with the liquid into a high pressure zone. By having a second element in the flow channel downstream of the cavitation zone, an inverse pressure is created to form the high pressure zone. The second element can also take many forms, but a similar element in operation is preferred to a control valve. By controlling the pressure in this area the apparatus is able to determine the length of the cavitation zone and determine when the collapse of the bubbles will occur. Upon entering the high pressure zone, the cavitation bubbles collapse, resulting in high pressure inclusions with the formation of shock waves emanating from the point of each collapsed bubble. Under the high temperatures and pressures caused by the collapse of bubbles, the liquid at the boundary of the bubble, and the gas inside the bubble itself, suffer chemical reactions that depend on the materials in the diet. These reactions can be oxidation, disintegration or synthesis, to name a few. In another aspect of the invention, the second element may be the first element of a second cavitation zone. In this form, two or more cavitation zones can be placed in series to produce a multi-phase apparatus. Each cavitation zone is controllable depending on the first element selected for the next cavitation zone, the distance between each first and second element, and the second end element on the end of the multi-phase apparatus. In yet another aspect of the invention, the second element may be as simple as an extended length of the channel, a deviation or elbow in the channel, or other piece of process equipment. The second element must provide some inverse pressure to create the high pressure and cavitation zones. The desired cavitated products are removed after the liquid by suitable separation techniques, such as vacuum filtration, filtration and evaporation. Before or after removing the cavitated products, the liquid can be recirculated back to the cavitation chamber. The recirculation of the unfiltered product can occur many times. Where multi-phase cavitation chambers are used, recirculation may be to one or more of the chambers. As the length of the recirculation period increases, the resulting final product generally has a higher degree of phase purity and smaller particle size. The nanostructured materials of the present invention are typically prepared by precipitating the desired product from a solution containing metal. The metal-containing solution is usually aqueous, but may be non-aqueous. At least one component of the metal-containing solution must be in the liquid state and be capable of creating cavitation. Other components may be different liquids, solids, gases, or mixtures thereof. Liquid components can be materials that are commonly thought of as liquids, or they can be materials that are commonly thought of as solids or gases that are processed in their liquid state. Examples of such materials are molten metals and molten minerals, as long as the vapor pressure is sufficiently low enough to generate bubbles, and liquid carbon dioxide. Most metals are in the form of salts. However, in the case of some precious metals, the metal can be added in the form of an acid such as chloroplatinic acid. Examples of suitable salts include nitrates, sulphates, acetates, chlorides, bromides, hydroxide, oxylates and acetylacetonates. The metal can be cobalt, molybdenum, bismuth, lanthanum, iron, strontium, titanium, silver, gold, lead, platinum, palladium, yttrium, zirconium, calcium, barium, potassium, chromium, magnesium, copper, zinc, and mixtures of same, although any other metal may find use in the present invention. For example, iron oxide can be made of hydrated ferric nitrate, barium titanate of a mixture of barium acetate in water and titanium tetraisopropoxide in isopropyl alcohol, and a ceramic such as lanthanum nitrate of lanthanum. Complex metal catalysts such as iron molybdate and bismuth can be formed using the appropriate metal salts. A class of metals typically suitable for piezoelectric materials is lanthanum, titanium, gold, lead, platinum, palladium, yttrium, zirconium, zinc and mixtures thereof. A class of metals typically suitable for superconductors is strontium, lead, yttrium, copper, calcium, barium and mixtures thereof. The solution within which the salt dissolves will depend on the particular metal salt. Suitable liquids include water, aqueous nitric acid, alcohols, acetone, hydrocarbons and the like. The precipitating agent can be selected from any suitable basic material such as sodium carbonate, ammonium carbonate, potassium carbonate, ammonium hydroxide, alkali metal hydroxide or even water where the metal salt reacts with water. Any liquid that causes the desired metal salt to precipitate from the solution due to the insolubility of the metal salt in the liquid can be a precipitating agent. In the modalities where recirculation occurs, it is desirable that the pH of the mixed solution be maintained on the basic side, usually between 7.5-12. However, the range is dependent on the precise material that is synthesized. In the case of preparing catalysts, a support can be added directly to the solution containing the metal, the precipitating agent or both. Suitable supports include alumina, silica, titania, zirconia and aluminosilicates. The support can also be added in the form of a salt, such as alumina by being added as hydrated aluminum nitrate where the support itself precipitates in the form of nanostructured grains under cavitation conditions. Zeolites such as ZSM-5, type X, type Y, and type L can be prepared using the process of the present invention. Metal charged zeolitic catalysts typically contain a metal component such as platinum, palladium, zinc, gallium, copper or iron. The metal salt solution, the precipitating agent and a silica source can be premixed to form a zeolite gel before passing into the cavitation chamber. Where the gel requires heat to form, the mixture can be recycled in the cavitation chamber until the gel is formed and the synthesis results. Alternatively, after cavitation, the well dispersed gel can be placed in a conventional autoclave where hydrothermal synthesis is carried out. This method will result in much finer grain zeolites after conventional hydrothermal treatment. The process of the present invention has applicability in catalysts, electrolytes, piezoelectrics, superconductors and zeolites as examples of nanostructured materials. The following examples show the benefit of the process present in the production of high purity nanosize products. Two apparatuses were used in these examples. The Model CaviPro ™ 300 is a two-stage orifice system that operates up to 26,000 psi with a nominal flow rate of 300 ml / min and more. The CaviMax ™ CFC-2h is a single orifice system that operates up to 1000 psi with a nominal flow rate of several liters per minute. These devices are obtained from Five Star Technologies Ltd, Cleveland, Ohio. Modifications were made to the peripheral elements of these devices, such as heat exchangers, cooling jacket, manometers and wetted materials, depending on the application contained in the examples.

EXAMPLE 1 This example illustrates that controlled cavitation allows the synthesis of an important hydrodesulfurization catalyst for use in environmental cleaning of gasoline in a substantially improved phase purity compared to conventional preparations. The preparation of cobalt molybdate with a Mo / Co ratio of 2.42 was carried out in the CaviPro ™ processor. Different orifice sizes were used for the experiment at a hydrodynamic pressure of 8,500 psi. In each experiment, 600 ml of 0.08M ammonium hydroxide in isopropanol was placed in the tank and recirculated. While this precipitating agent was recirculated, a mixture of 3.43g (0.012 mole) of CoN03 · 6H20 and 5.05g (0.029 mole) (NH4) 6 was introduced. 7024 · 4H20 was dissolved in 50ml of distilled water for 20 minutes. After the salt solution had been added, the resulting suspension was immediately filtered under pressure and dried for 10 hours at 110 ° C. The XRD analyzes were recorded after calcination in air at 325 ° C. The conventional preparation of cobalt molybdate with a Mo / Co ratio of 2.42 was carried out by classical synthesis. In each experiment, 600 ml of 0.08 M ammonium hydroxide in isopropanol was placed in a well-stirred container. While this precipitating agent was stirred, a mixture of 3.43g (0.012 mole) of CoN03 · 6H20 and 5.05g (0.029 mole) (NH4) 6Mo7C > 24 | 4H20 dissolved in 50 ml of distilled water for 20 minutes. After the salt solution had been added, the resulting suspension was immediately filtered under pressure and dried for 10 hours at 110 ° C. The XRD analyzes were recorded after calcination in air after 325 ° C. The XRD pattern of the material after calcining in air indicates, by the high intensity of the reflection at 26.6 degrees 20 in all the synthesis using cavitation process, the formation of a high fraction of cobalt molybdate. In addition, the XRD of the conventional method showed a much lower intensity peak at 26.6 degrees 20 as well as strong reflections at 23.40 and 25.75 degrees 20 due to separate phase Mo03. Thus the present process produced a catalyst of higher purity than that found in the prior art.

Example 2 The catalyst of Example 1 was repeated, but at a hydrodynamic pressure greater than 20,000 psi. The XRD standards showed even higher phase purity compared to the cavitation preparation in Example 1 and much better purity compared to the classical synthesis.

Example 3 The catalyst of Example 1 was prepared using a CaviMax processor at a lower pressure. The hole used was 0.073 inches in diameter at 580 psi of discharge pressure. Reverse pressure varied between 0-250 psi. The phase purity of the cobalt molybdate was almost as high as that observed in Example 2 and much better than that observed in Example 1. It was much better than the conventional preparation that did not use hydrodynamic cavitation. The XRD data shows that the application of all backward pressures resulted in a higher purity phase of cobalt molybdate compared to the conventional preparation.

Example 4 Example 1 was repeated using a CaviMax ™ processor at a pressure of 200-660 psi and using orifice sizes of 0.073, 0.075, 0.089, and 0.095 inches in diameter. All phase purities of the catalysts were improved. The use of an orifice diameter of 0.095 inches at 280 psi resulted in a superior quality of hydrodesulfurization catalyst compared to all other diameters as well as conventional synthesis.

Example 5 This example illustrates the ability of the present invention to synthesize high phase purities of cobalt molybdate supported on gamma-alumina. The preparation of cobalt molybdate deposited on gamma-alumina with a Mo / Co ratio of 2.42 was carried out in the CaviPro ™ processor. A cavitation generator having orifice sizes of 0.009 / 0.010 inch in diameter was used for the experiment in a hydrodynamic pressure range of 4., 000, 7,000, and 8,000 psi. In each experiment, 600 ml of an ammonium hydroxide solution in 0.0102% isopropyl alcohol (IPA) was placed in the tank along with 5.0 g of gamma-alumina, and the suspension was recirculated through the processor. While this precipitating agent was recirculated, 0.859 g (0.00295 mole) of Co (NO) 3-6H20 and 1262 g (0.000715 mole) of (NH4) 6 ?? 024 * 4H20 dissolved in 50 ml of water were introduced for 20 minutes. . After all the salt solutions had been added, the resulting suspension was recirculated through the processor for an additional 5 minutes. The suspension was immediately filtered under pressure and dried for 10 hours at 110 ° C. The XRD analyzes were recorded after calcination in air at 350 ° C for four hours. At all pressures the experiment resulted in higher phase purities of the precursor of the active hydrodesulfurization catalyst, cobalt molybdate, as compared to the conventional synthesis of the same catalyst. In addition, for this catalyst, the optimum conditions for the generation of the smallest nanostructured grains of the catalyst resulted from the synthesis at 4,000 psi of low pressure.

Example 6 The catalyst of Example 5 was prepared using silica instead of alumina. The preparation of cobalt molybdate deposited on Cabosil (silica) with a Mo / Co ratio of 2.42 was carried out in the CaviPro processor. Different orifice sizes were used for the experiment in a hydrodynamic pressure range of 10,000 psi. In each experiment 600 ml of ammonium hydroxide in isopropyl alcohol (IPA) 0.0102% was placed in the tank together with 5. Og of Cabosil, and the suspension was recirculated through the processor. While this precipitating agent was recirculated, 0.859 g (0.00295 mole) of CoN03-6H20 and 1262 g (0.000715 mole) of (NH4) sMo7024 | 4¾0 dissolved in 50 ml of water were introduced for 20 minutes. After all the salt solutions had been arranged, the resulting suspension was recirculated through the processor for an additional 5 minutes. The suspension was immediately filtered under pressure and dried for 10 hours at 110 ° C. The XRD analyzes were recorded after calcination in air at 350 ° C for four hours. The cavitation synthesis resulted in higher phase purity for the cobalt molybdate deposited on silica compared to the conventionally prepared catalyst, and the use of a set of holes of 0.006 and 0.014 inches in diameter led to finer nanostructured grains of the catalyst.

Example 7 The present invention was used to synthesize bismuth beta-molybdate (BÍ2 or 20g) which is typical of the family of catalysts used for partial hydrocarbon oxidations such as the conversion of propylene to acrolein or ammoxidation of propylene into acrylonitrile. This synthesis used a CaviMax ™ processor with four different orifice sizes in a low pressure mode. The synthesis of this material was carried out as follows. 450 ml of IPA was used as the precipitating agent, and placed in the reservoir. While this precipitating agent was recirculated, 12.83g, 0.0264 moles of Bi (N03) 3 · 5H20 dissolved in 50ml of 10% HN03, and 4.671g, 0.00378 moles of (NH4) e 7024 | 4H20 dissolved in 50 was introduced. My distilled water for 20 minutes. After all the salt solutions had been added, the resulting suspension was recirculated through the processor for an additional 2 minutes. The suspension was immediately filtered under pressure and dried for 10 hours at 110 ° C. The XRD analyzes were recorded after calcination in air after 350 ° C.

Table 1: Variation of the Grain Sizes The cavitation synthesis resulted in very pure phase bismuth beta-molybdate. In addition, the XRD patterns showed that the grain size of the particles could be varied over a wide range of sizes in nanometers by changing the hole sizes. Since it is well known in the catalytic literature that catalyst grains in nanometers often result in greatly accelerated reaction rates, the ability of cavitation synthesis to vary this grain size is of general importance for various catalytic reactions other than the partial oxidation of hydrocarbons.

EXAMPLE 8 This example shows that the present invention as applied to the synthesis of complex metal oxides such as perovskites and metal oxides AB03 results in exceptionally high phase purities. The synthesis of La, 7Sr.3Fe03 was done using a CaviMax ™ processor and using orifice sizes of 0.073, 0.081, 0.089, and 0.095 inch in diameter. 600 ml of a 1M solution of Na 2 CO 3 was placed in distilled water in the tank, and the suspension was recirculated through the processor. While this precipitating agent was recirculated, La (N03) 36H20 (7999 g, 0.0185 mole), Fe (N03) 3-9H20 (10.662 g, 0.0264 mole) and Sr (N03) 2 (1.6755 g, 0.00792 mole) were dissolved in 100 ml of distilled water and this solution was introduced for 20 minutes. After all the salt solutions had been added, the resulting suspension was recirculated through the processor for an additional 5 minutes. The suspension was immediately filtered under pressure and dried for 10 hours at 110 ° C. The XRD analyzes were recorded after calcination in air at 60 ° C, The XRD data showed that an orifice size of 0.095 inches in diameter resulted in the synthesis of pure phase nanostructured perovskite La0.8Sro, 2Fei, o03.ox, as a nanostructured material of 18 nm and the phase purity was much better than that obtainable by conventional synthesis. Parallel experiments using the CaviPro ™ processor using orifice assemblies of 0.006 / 0.008, 0.006 / 0.010, 0.006 / 0.012 and 0.006 / 0.014 inches in diameter all resulted in very pure phases of the desired perovskite containing few separate phase impurities. These results were superior to both of the conventional syntheses and the CaviMax ™. The importance of this type of perovskite material is for the oxidation of CO in automotive exhaust pipe applications, for solid state oxygen conductors for fuel cell applications, and for dense catalytic inorganic membranes used for oxygen transport in the change of methane form to syngas.

Example 9 This example shows that tension can be systematically introduced into a crystallite in the solid state by the use of the present invention. The example examined the synthesis of titanium dioxide using the CaviMax ™ processor and examined the effect of the voltage introduced into the Ti02 crystal as the orifice size of the cavitation processor was systematically changed. In this synthesis, 100 g (0.27664 mol) of Ti Butoxide was mixed with 2-propanol to give a volume of 0.5 1 (olarity = 0.553 mol / l) in a glove box under nitrogen. This process produced a transparent yellowish solution, which is stable in the air. 750 ml of deionized water was placed for a typical run in the CaviMax tank and circulated. 75 ml of the Ti / 2_Propanol Butoxide solution was added slowly with a feed rate of 4 ml / minute. The solution with the precipitated Ti compound was circulated for an additional 17 minutes. Subsequently, the suspension was filtered under high pressure at 100 psi (6.9 bar). The filtrate was dried at 100 ° C for 2 hours and then calcined at 400 ° C for 4 hours. The XRD data were taken after calcination in air and the tension percent was estimated from the Williamson-Hall method.

Table 2: Cristalito tension As shown in Table 2, the crystallite tension content increased from 0.2% prepared with a small hole (0.073 inches in diameter) to 0.35% prepared with a large hole (0.115 inches in diameter), linear with its diameter. The ability to systematically alter the tension within a crystallite is important because it changes the chemical potential of the atoms on the surface. The applications of this type of control include the application of these materials as photocatalysts or as optical absorbers.

Example 10 The synthesis of 20% w / w of Ag on nanostructured metal silver titania was examined as a function of the orifice size, and the results were compared with the conventional synthesis of such metal-supported materials. In this synthesis, a precipitating agent consisting of 1000 ml of deionized water was recirculated in the CaviMax ™ processor equipped with a 0.075 inch diameter orifice. A solution of 100 ml of titanium (IV) butoxide (Ti [0 (CH2) 3CH3] 4) in isopropyl alcohol (0.63 mol / L Ti) was added to CaviMax ™ at 4 ml / min to form a precipitate. The total time of precipitation plus the additional recirculation was 30 minutes. Subsequently, two solutions were added simultaneously to the recirculating, precipitated titanium suspension. The first solution consisted of a 250ml silver silver acetate solution (AgOOCCH3) in deionized water (0.046 mol / L Ag) that was added at a rate of 10 ml / min. The second feed was a solution of 250 ml of hydrazine (N2H4) in water (0.70 mol / L of N2H4), such that the molar ratio of N2H4 / Ag was 15.0, which was added at a rate of 10 ml / minute.

The total time of addition plus the additional recirculation was 30 minutes. The product was filtered, washed with water to form a wet cake, and then dried in an oven at 110 ° C. A portion of the dried product was calcined in air for 4 hours at 400 ° C. A portion of the dried product was subjected to X-ray analysis and identified as silver on an amorphous titanium support. The X-ray line magnification analysis indicated that the average size of the silver crystallite was 7.4 nm. A portion of the calcined product was subjected to X-ray analysis and identified as silver on titania. All titania was identified as anatase, while rutile was not observed. The X-ray line magnification analysis indicated that the average silver crystallite size was 12.0 nm. Conventional synthesis was performed as above except in a stirred 1500 ml beaker. The grain sizes of the silver particles after drying the samples at 110 ° C are shown in Table 3. This example shows that metal particles deposited on reactive supports such as titania can be synthesized in smaller grain sizes compared to the conventional parallel synthesis. furtherWhen the catalysts were calcined at 400 ° C in air, the silver particles deposited on the conventional catalyst grew to a much larger size than those deposited by cavitation techniques. These types of materials are important as photocatalysts for the destruction of toxins in chemical waste streams.

Table 3: Grain size of 20% p / p Silver over Titania Example 11 2% w / w of silver was synthesized on alpha-alumina using a cavitational synthesis and a conventional synthesis. The synthesis of this material was carried out as follows. A suspension consisting of 5.00 g of aluminum oxide (alpha, A1203) in 1000 ml of deionized water was recirculated in the CaviMax processor equipped with a 0.073 inch diameter orifice. Two solutions were added to the recirculating aluminum oxide suspension. The first solution consisted of a solution mi of silver acetate (AgOOCCH3) and ammonium hydroxide (NH40H) of deionized water. The concentration of the silver was 0.0095 mol / L, and the concentration of the ammonium hydroxide was 0.095 mol / L, so that the molar ratio of NH40H / Ag was 10.0. The silver solution was added to the aluminum oxide suspension at a rate of 4 ml / minute. The second feed was a solution of 100 ml of hydrazine (N2H) in water (0.14 mol / L N2H4), such that the molar ratio of N2H4 / Ag was 15.0, which was added at a rate of 4 ml / minute . The total time of addition plus the additional recirculation was 30 minutes. The product was filtered, washed with water to form a wet cake, and then dried in an oven at 110 ° C. A portion of the dried product was subjected to X-ray analysis and identified as silver on alpha-alumina. Conventional synthesis was performed in the same manner as above except in a beaker at 1500 ml shaken. The data in Table 4 show that the cavitation synthesis using an orifice size of 0.073 inches in diameter and a ratio of NH40H / Ag of 10/1 resulted in much smaller grain sizes of Ag.

Table 4: Grain Sizes (nm) of the 2% Ag / Al203 Synthesis Example 12 The present invention was used for the synthesis of gold nanostructured particles supported on titanium oxide (Ti02). In this synthesis a precipitating agent consisting of 650 ml of deionized water was recirculated in the CaviMax ™ processor equipped with a 0.075 inch diameter orifice. A solution of 100 ml of titanium (IV) butoxide (Ti [0 (CH2) 3CH3] 4) in isopropyl alcohol (0.88 mol / L Ti) was added to CaviMax ™ at 4 ml / minute to form a precipitate. The total time of precipitation plus the additional recirculation was 37.75 minutes. Immediately afterwards, two solutions were added simultaneously to the precipitated recirculating titanium suspension. The first solution consisted of a 1000ml solution of chloro-uric acid gold (HAuCl4 3H20) in deionized water (0.0073 mol / L Au) which was added at a rate of 4.7 ral / minute. The second feed was a solution of 100 ml of hydrazine (N2H4) in water (0.12 mol / L of N2H4), such that the molar ratio of N2H4 / Au was 16.7, which was added at a rate of 0.4 ml / minute. The total addition time plus the additional recirculation was 3.62 hours. The product was filtered, washed with water to form a wet cake, and then dried in an oven at 110 ° C. A portion of the dried product was calcined in air for 4 hours at 400 ° C. A portion of the calcined product was subjected to X-ray analysis and identified as gold over titania (anatase). Analysis of the magnification of the X-ray line indicated that the average size of the gold crystallite was 7.5 nm, and that the average size of the anatase crystallite was 12.9 nm. The conventional synthesis was prepared in the above manner except in a stirred 1500 ml beaker. The data in Table 5 show that the cavitation process during the synthesis of 2% w / w of gold on titania resulted in the systematic decrease of the grain sizes within the range of very small manometric size. This example shows that the combination of the selection of the orifice size and the parameters of the process allow a control of the grain sizes not possible with the conventional synthesis.

Table 5: Grain size as a function of the volume of the gold solution.

Where the cavitation synthesis gave an Au grain size of 16 nm, the conventional synthesis resulted in a grain size of 25 nm. Where the cavitation synthesis gave an Au grain size of 7.5 nm, the conventional synthesis gave a grain size of 23 nm.

Example 13 The present invention was used to commercially synthesize important piezoelectric solid state materials with very high phase purity at low heat treatment temperatures.

Table 6: Preparation of PZT in different tretinograms Four solutions were prepared to synthesize PZT. 105.95g (0.279 moles) Pb (II) acetate hydrolyzate (PbAc) was dissolved in 1000 ml of purified water. 100 g (0.279 moles) of Ti butoxide (TiBut, 97%) were diluted with 2-propanol at 500 ml. 132.58g (0.279 moles) of Zr-butanol butoxide complex (ZrBut, 80%) was diluted with 2-propanol at 500 ml. 2.74g (0.0285 moles) of ammonium carbonate (Amm) was dissolved for each run in 350 ml of water to give a solution of 0.0814. The detailed stoichiometric information for this series is given in Table 6. The ammonium carbonate solution was placed in the tank and circulated. The Zr and Ti solutions were combined and fed at a rate of 2.5 ml / minute into the reservoir stream at a position just before entry to the high pressure pump. The Pb acetate solution was co-fed at a rate of 5 ml / minute. All the metal-containing components were immediately precipitated and attracted into the high-pressure zone of the cavitation processor and then passed into the cavitation generation zone. All samples were dried overnight and calcined in three stages for four hours at 400 ° C, 500 ° C and 600 ° C. The XRD patterns above a calcination temperature of 500 ° C only form the pure perovskite phase without impurities of lead oxide or zirconium oxide.The XRD standards contain some finer crystallites of this material appearing as a broad band centered on 30 degrees 20. This material disappears from the composition after calcination to 600 ° C. In addition, this material of the present invention showed a much higher phase purity. The data in Figure 1 illustrate that the hydrodynamic cavitation technique allows piezoelectric synthesis in compositions that have a very high degree of stress built into the individual crystallites. In addition, Figure 1 shows that the degree of stress can be systematically introduced into the crystals as a function of the type of orifice used in the synthesis. It was found that the degree of tension introduced by the cavitation was much higher than that found in a 3d classical piezoelectric synthesis method of the same composition. The data in Figure 2 illustrate the advantage of the cavitation process in the PZT synthesis by a direct comparison with a classical co-precipitation synthesis. The upper XRD pattern in Figure 2 resulted from a cavitation preparation after calcination in air at 600 ° C. The lower figure resulted from a classical co-precipitation carried out using the same synthesis procedure except that only high speed mechanical agitation was used in the co-precipitation step rather than the cavitation processing. A comparison of the two XRD patterns shows that the classical pattern has a substantial fraction of lead oxide separated phase while the cavitation preparation has no secondary phase in its composition. This greater purity of phase is exceptionally important in the functioning of the materials as a piezoelectric device.

EXAMPLE 14 The present invention was used for the synthesis of fine particles of pure metal particles in a suspension in which the grain size can be altered depending on the hole sizes that are used. The data in Table 7 illustrate the ability to form nanostructured grains of finely divided metals typically and commercially used to hydrogenate aromatic and functional groups on organic intermediates in pharmaceutical chemical and fine chemical processes. In this synthesis, 0.465 g of hexachloroplatinic acid was dissolved in 50 ml of isopropanol. The platinum solution was fed to a stirred Erlenmeyer flask, which contains 0.536 g of hydrated hydrazine, 54.7% solution in 50 ml of isopropanol. The feed rate of the platinum solution was 5 ml / minute. Following directly the reduction of platinum, the solution was fed to the CaviPro processor, and processed for 20 minutes, time after which the XRD of the dry powders was measured. Table 7: Effect of pressure and hole sizes in the synthesis of nanostructured platinum. Orifice assembly Pressure Metallic grain size of Pt (nm) .004 / .014 25,000 psi 3.9 .004 / .006 25,000 psi 3.7 .004 / .014 15,000 psi 4.1 .004 / .006 15,000 psi 3.9 classic 14.7 psi 5.4 Example 15 The process of the present invention was used to manufacture the catalysts of silver on alpha-alumina commercially important used in the production of ethylene oxide from the partial oxidation of ethylene. The LOES data in Table 8 illustrate the grain sizes determined with XRD of the silver particles that had been deposited on the alpha-alumina during the cavitation synthesis in which the silver was reduced in a cavitation experiment and then deposited on Alpha-alumina in water using classical techniques. The data shows that changing the hole sizes used in each experiment can alter the grain size of the plate. The characteristics of the different orifice sizes are expressed as the calculated cavitation numbers for each experiment, which is a common reference for the occurrence of cavitation in fluid flow streams. Using this characterization method, the cavitation generated in the metal synthesis stream is greater as the pass cavitation numbers decrease. In this synthesis, 2% silver was prepared on α-alumina by the reduction of silver acetate using hydrazine. This reduction was carried out on the CaviPro ™ processor at a pressure of 15,000 psi, followed by a classical adsorption / deposition of an aqueous suspension of silver particles on an α-alumina support. The number of passes of the medium for each consecutive experiment was set, and the feed flow rates and process time were adjusted accordingly. The total number of passes for this series of experiments remained constant at 1.6. Experiments were carried out by varying the step cavitation number, varying the size of the first hole. The results are shown in Table 8 below.

Table 8: Variation in grain sizes of the silver particles Example 16 The degree of calcination was examined in using the present invention. Four separate samples of solid ammonium molybdate were calcined for four hours in air at 100 ° C, 175 ° C, 250 ° C and 325 ° C respectively. The XRD data was taken afterwards for each sample. A sample of ammonium molybdate was dissolved in water and fed into a solution of isopropyl alcohol (the precipitation agent) just before it was passed into a CaviPro ™ processor using a set of 0.012 / 0.014 inch holes. This sample was then filtered and dried at 100 ° C. The XRD data was then obtained for this sample. A comparison of the XRD standards showed that the sample generated from the present invention had a higher degree of calcination than the sample calcined at 100 ° C, and approximately equal to that of the 175 ° C sample. Considering the millisecond residence time for the present invention compared to 4 hours for the conventional method, the use of the present invention resulted in some in-situ thermal calcination.

B e 17 In order to evaluate the effect of silver concentration on the crystallite size, a series of silver-on-alumina catalysts were synthesized, with various concentrations: 1%, 2%, 5%, 10%, and 15% by weight of Ag on Al203. In this synthesis 20.44 g of aluminum isopropoxide in 100 mL of cyclohexane solution was added to 600 mL of water that was recycled in the CaviMax (0.075"orifice) After processing 5 minutes, hydrazine was added in a proportion of silver to hydrazine 1. After processing five minutes, a solution of 400 ml of silver acetate was fed to CaviMax (40 mL / min.) After the addition of silver acetate, the product was processed for 10 minutes (the total synthesis time was 30 minutes.) The product was filtered under pressure, washed with 150 mL of isopropanol (to remove cyclohexane), and washed twice with 150 mL of di-H20. overnight at 105 ° C. Ag / Al203 samples were calcined for six hours at 400 ° C. After calcination, the samples were analyzed using an XRD. These results are shown in Figure 3. The XRD of the material calcined at 400 ° C does not show virtually any reflection for the metallic silver indicating that the particles are exceptionally well dispersed. The wide envelope that arises near 35 degrees 2 teta could be due to the formation of silver oxide. It is known that silver oxide decomposes at 300 ° C; thus, if all the silver has been converted to silver oxide, it consists of very small grain sizes and must be interacting strongly with the aluminum oxide support. The literature reports that a form of silver oxide at high temperature can be synthesized, but the literature report indicates that this oxide is able to form normally only at temperatures above 1600 K. The exceptional behavior of these materials is that the silver component must be formed in very small grains and have provided a catalytic structure that is very different from the silver-on-alumina forms reported in the literature. It is expected that this catalyst will be very effective in the area of environmental catalysis and useful for the reduction of nitric oxide in hydrocarbons. The fact that a high temperature is obtained from the stable form of the silver oxide in these catalysts can be especially useful for the nitric oxide reduction reaction.

Example 18 Synthesis of Novel Structures for copper-modified zinc oxide useful as a catalyst for the synthesis of methanol. A series of experiments was carried out precipitating Cu0.225Zn0.575Alc.ll to study its influence of cavitation. Therefore, an aqueous solution was prepared by dissolving 37.514 g (0.1 mole) of Al (N03) 3 * 9H20, 60.40 g (0.225 mole) of Cu (N03) 3 * 3H20 and 124.353 g (0.675 mole) of Zn (N03) ) 3 * X H20 in 1000 ml of deionized water. An aqueous solution of 0.553 molar of (NH4) 2C03 and 1.0 molar of Na2C03 solution was used as precipitation agent. The amount of carbonates used was determined experimentally to obtain a pH value of 8. Two different series were made in the CaviPro. The first series was made using (H4) 2C03 at a constant pressure of 10,000 psi with the holes of 6-14, 7-14, 8-14, 10-14 and 12-14 (Denoted as Low Pressure Experiments). The second series was made using Na2C03 at a constant pressure of 20,000 psi with the holes 6-7, 6-10, 6-12 and 6-14 (Denoted as High Pressure Experiments). All samples were washed with water, filtered, dried at 100 ° C overnight and then calcined at 350 ° C for four hours. The X D was taken and the standard investigations were carried out. All X-ray patterns were identified as a mixture of ZnO and CuO. Additionally, residual Na2CO3 was detected for the second series, which was not completely removed with the washing procedure. Figure 4 reveals a typical diffractogram obtained. Another important feature of the experimental results is shown in Figure 5. The data in this figure indicate that the cavitation process experiments resulted in different grain sizes of the active component, CuO, and that the stress in these small grains increased as they decreased the grain sizes. In addition, the materials prepared classically showed a very low degree of tension. The analysis of the grid constants for both oxides shows some very exceptional results for the catalysts for methanol synthesis as judged from the previous literature for the synthesis of this type of catalyst. Figure 6 shows that the trellis spacing for the c-axis direction in CuO has been changed to an exceptionally high value compared to conventional catalysts for the high-pressure experiments. The c-axis of copper oxide is changed in the experiment at high pressure to the same value as that of zinc oxide. This distortion of the unit cell is very exceptional, and causes the much greater voltage detected for the CuO in this system. In addition, this fact is an indication of the epitaxial growth of CuO on ZnO and a novel structure for this type of catalyst. This is potentially important for the activity of this material in the catalysts for methanol synthesis. The epitaxy is the growth of a solid compound (here the CuO) that tries to imitate the structure of the substrate (ZnO). Due to the different preferred geometrical arrangements of the CU2 + (quadratic planar) and Zn2 + (tetrahedral), it is not possible for one or the other species to grow in that form. The transition of ZnO into CuO can be considered as an interlayer, which has in the lower plane Zn atoms. The next plane would be a layer of atoms of 0, followed by the first layer of Cu atoms. In that case, a type of 2-dimensional superetrej can be found. Since this appears to be a novel structure for a catalyst for Cu-Zn-Al-0 methanol synthesis that can be obtained by the cavitation process and in a high pressure cavitation process, it could be important in eventual catalytic evaluations. In addition, the data in Figure 5 show that the copper oxide component can be synthesized in systematically diverse grain sizes.

Example 19 A series of supports of 2% palladium on alumina / zirconia (10% / 90%) was synthesized to produce a catalyst with high surface area, and small metallic crystallite size that is stable up to high temperatures (1200 ° C). It has been suggested that alumina acts as a barrier preventing the phase transformation of the zirconia support, and thereby recovering the small grain crystallite support and the prevention of palladium sintering. Four samples were synthesized in the CaviMax (0.073", 0.081 :, 0.095", and 0.115"), as well as a classical precipitation, adding 100 mL of a palladium nitrate solution and 100 mL of a hydrated hydrazine solution to a Water recirculation of 700 mL of water in CaviMax This mixture was processed for 30 minutes after which a solution of zirconia n-butoxide / aluminum isopropoxide in n-hexane was added to the synthesis solution. it was processed for an additional 20 minutes after which the samples were pressure filtered and washed.The material calcined in air at 1095 ° C using the 0.115"hole in the CaviMax is shown in Figure 7. The important aspect of this The result is that a palladium supported catalyst was synthesized, where calcination at high temperature did not cause the catalyst to densify into a large grain material that would be expected to have a very low surface area. It would be expected that this type of stable high temperature catalyst would have commercial application in combustion turbines used by electricity companies to generate electricity. Although various embodiments of the present invention have been described, it should be understood that modifications and adaptations thereof will occur to those skilled in the art. The compositions of the present invention as well as the methods for forming those compositions can be extended to a number of uses and applications. Other features and aspects of this invention will be appreciated by those skilled in the art when reading and understanding this description. Such characteristics, aspects, and variations and expected modifications of the reported results are clearly within the scope of the invention and the invention is limited only by the scope of the following claims.

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. A catalyst formed by cavitation, characterized in that the cavitation comprises passing a metal-containing solution at elevated pressure and at a velocity within a cavitation chamber, wherein the cavitation chamber creates a controllable cavitation zone to form a cavitated product.
2. 2. The catalyst according to claim 1, characterized in that the high shear stress and at least some in-situ calcination of the metal-containing solution occurs in the cavitation chamber.
3. The catalyst according to claim 1, characterized in that the cavitation chamber comprises a side-by-side flow channel having a flow area, internally containing a first element that produces a local constriction of the flow area and that it has an output downstream of the local constraint; and a second element that produces a second local constriction located at the outlet, where a cavitation zone is formed immediately after the first element, and a high pressure zone is created between the cavitation zone and the second local constriction.
4. The catalyst according to claim 3, characterized in that the velocity of the metal-containing solution passing inside the cavitation chamber is at a speed sufficient to create cavitation bubbles to form downstream of the first element.
5. The catalyst according to claim 1, characterized in that the metal-containing solution is a metal salt solution.
6. The catalyst according to claim 5, characterized in that the metal salt is selected from the group consisting of nitrate, acetate, chloride, sulfate, bromide, and mixtures thereof.
7. The catalyst according to claim 6, characterized in that the metal in the metal-containing solution is selected from the group consisting of cobalt, molybdenum, bismuth, lanthanum, iron, strontium, titanium, silver, gold, lead, platinum, palladium, yttrium, zirconium, calcium, barium, potassium, chromium, magnesium, copper, zinc, and mixtures thereof.
8. 8. A silver catalyst supported on alumina characterized in that it has the properties shown in Figure 3 of the present invention.
9. 9. A CuO composition characterized in that it has the properties shown in Figure 4 of the present invention.
10. 10. A high temperature palladium catalyst characterized in that it comprises a small grain material that is stable at temperatures of less than about 1200 degrees Celsius.