MXPA99001170A - Stable dispersions of metal passivation agents and methods for making them - Google Patents

Abstract

A process for passivating contaminating metal on a hydrocarbon cracking catalyst is provided. The catalyst is contacted within a hydrocarbon catalytic cracking unit with a stabilized dispersion. The dispersion comprises a fluid vehicle, a dispersion agent, and finely milled particles of one or more metals or metal compounds for passivation of metal-contaminated cracking catalysts. The dispersion is preferably produced by a process wherein an agitated media mill is loaded with comminuting media, fluid vehicle, dispersion agent and particles of a metal or metal compound for passivation of metal-contaminated cracking catalysts. The comminuting media, fluid vehicle, and particles are then agitated until the particles are reduced in size by at least 10%and have a volumetric average particle size of less than 0.5 microns.

Description

STABLE DISPERSIONS OF METAL PAS3LVATION AGENTS AND METHODS TO PREPARE THEM. • 5 FIELD OF THE INVENTION.

The present invention relates to stable dispersions of finely divided particles of metals and metal compounds that provide passivating properties of metals to zeolites containing cracking catalysts. The present invention also relates to several • grinding processes to reduce such metals and metal compounds in size to disperse them in water and / or organic liquids. fifteen BACKGROUND OF THE INVENTION.

High-boiling components of crude oil are unsuitable for inclusion in gasoline and other liquid hydrocarbon fuels. Accordingly, the oil refinery industry has developed processes for cracking or breaking down these high molecular weight, high boiling components into 25 smaller molecules with a lower boiling point. A REF .: 29419 cracking process widely used for this purpose is known as catalytic fluid cracking (FCC). The FCC process has reached a state of high advance, and some variations have been developed, but the unifying feature of these variations is that the vaporized hydrocarbon feed is cracked by contact at a high temperature with a cracking catalyst. After reaching the desired degree of molecular weight and reducing the boiling point, the catalyst is separated from the desired products. If the catalyst is reused again and again to process additional feeds, which is usually the case, coke and heavy metals are deposited on the catalyst. The catalyst used is typically regenerated by contact with an oxygen containing gas, under conditions where at least a portion of the coke is converted to carbon oxides, and the regenerated catalyst is recycled to the reactor for contact with fresh feed. As heavy metals accumulate on the catalyst, they eventually accumulate to the point that they unfavorably alter the composition of the catalyst and / or the nature of its effect on the feed. For example, such metals cause an increase in the formation of coke and hydrogen gas, therefore decreasing the production of the desired gasoline. In addition, these metals affect both the activity and the selectivity of cracking catalyst. Regeneration does not solve the problems caused by these polluting metals. Heavy metals capable of adversely affecting the catalytic cracking process include platinum, palladium, chromium, nickel, copper, cobalt, vanadium and iron. Unfortunately, nickel, copper, vanadium, cobalt and iron are usually present as contaminants in hydrocarbon feeds that They are catalytically cracked. Additional information regarding the catalytic cracking of hydrocarbons and their challenges can be found, for example, in US Pat. Nos. 4,454,025 and 4,363,720, which are incorporated herein by reference. The ability of various metals and metal compounds to act as metal passivating agents against the adverse effects of transition elements such as nickel, vanadium, cobalt, copper, iron and other heavy metals contaminants on zeolite containing cracking catalysts is known in art. Such passivating agents are used to improve or restore metal-contaminated zeolite cracking catalysts. The treatment of zeolite cracking catalysts with such metal passivating agents that provide numerous benefits in catalytic cracking, including higher feed oil conversion, higher gasoline production, higher isobutylene production, lower production of high cycle oils, lower generation of coke and / or lower generation of hydrogen gas. Commercially used metal passivation aqens come in various manners, including solutions of organometallic complexes and aqueous suspensions of colloidal solid particles in a suspending agent. In aqueous suspensions, the solid particles are typically prepared by chemical precipitation or by ion exchange chemistry. See, for example, US Patent No. 4,933,095 of Johnson et al, the description of which is incorporated as a reference. These passivating agents are used by direct introduction of them at a carefully controlled rate into the hydrocarbon catalytic cracking unit, which typically includes a cracking reactor and a catalyst regenerator. For example, they can be introduced into the catalytic cracker, the hydrocarbon feed, or the regeneration zone. Successful introduction requires that the dispersion of the passivation agents be stable and that a reasonable viscosity be maintained. However, the above passivating agents are usually expensive to prepare and the preparation routes are usually restricted to make the passivating agents available. In addition, more conventionally available and at a lower cost metal and solid metal compounds that have potential use as effective passivation agents are too large to be conveniently suspended to form stable suspensions. Finally, the suspension agents currently used in connection with the particulate passivating agents tend to act as thickeners of the suspension and consequently decreasing the rate of deposit of the suspension. The use of such suspending agents results in suspensions that have a relatively short half-life and / or are viscous, making it more difficult and expensive to pump them. In view of the foregoing, there is presently a need for a process by which a wide variety of particulate metals and metal compounds useful as metal passivating agents are provided in a stabilized form that is convenient for introduction into the processes catalytic cracking, BRIEF DESCRIPTION OF THE INVENTION According to an embodiment of the present invention, a process for passivating polluting metal from a hydrocarbon cracking catalyst is. provided. The catalyst is contacted with a catalytic cracking unit with a stabilized dispersion. The agent comprises a fluid carrier, a dispersing agent and finely divided particles of one or more metals or metal compounds for passivation catalysts contaminated with metates. The particles have an average volumetric particle size of less than 0.5 microns, preferably less than 0.25 microns, more preferably of 1 micron atoms. Regarding the particle size distribution, it is preferred that at least 99% of the particles have sizes of less than 1 micron, more preferably less than 0.3 microns, The metal or metal compound is preferably selected from the group consisting of antimony , zirconium, tungsten, tin, bismuth, indium, thallium, calcium, tellurium, zinc, cadmium, lithium, germanium, beryllium, magnesium, strontium, aluminum and compounds thereof. More preferably, the metal or metal compound is selected from antimony oxides, bismuth oxides, tin oxides, tungsten oxides and zirconium carbonates, more preferably antimony trioxide. The fluid carrier is preferably selected from the group consisting of hydrocarbon oils, alcohols, ethylene glycol and water. The dispersing agent is preferably selected from the group consisting of cationic surfactants, amphoteric surfactants, non-ionic surfactants, wetting agents and anionic surfactants. If desired, the dispersion may further be provided with an antifreeze preferably selected from the group consisting of ethylene glycol, methanol, ethanol, isopropanol and acetone. The dispersion is preferably produced by a process wherein a stirred medium mill is loaded with a grinding medium, fluid carrier, dispersing agent and particles of a metal or a metal compound for passivation of a catalyst contaminated with metal. The crushing medium, fluid vehicle, and the particles are then stirred until they are reduced in size to at least 10% and have an average volumetric particle size of less than 0.5 microns. At least 99% of the particles are preferably smaller than 1 micron. In the above process the agitated medium mill is preferably operated at an extreme speed in the range of 1000 to 6000 feet per minute. The grinding medium is preferably provided in an amount sufficient to fill approximately 80 to 92% of the volume within the mill. The grinding medium is preferably selected from the group consisting of sand, glass, metal or ceramic beads, more preferably barium titanium, sodium and lead carbonate, borosilicate, carbon steel, stainless steel, tungsten carbide, zirconium silicate, uranium alumina stabilized with zirconium oxide. Accordingly, the present invention provides a cost efficient method for preparing an aqueous and / or organic dispersion of metal passivating agents, with or without antifreeze agents, by reducing the size of the solid particles by mechanical means in an agent of appropriate dispersion. An advantage of the present invention is that dispersions containing a wide variety of particulate passivating agents can be formed. Another advantage of the present invention is that the dispersions can be formed by a less expensive and less complex process than many conventional methods. A further advantage of the present invention is that stable dispersions of metal passivating agents are formed without the use of suspending agents that function using an increased viscosity to slow down the rate of particle deposition. The dispersions of the present invention therefore tend to be less viscous and have a longer half-life than many suspensions of the prior art.

Yet another advantage of the present invention is that the dispersion of the present invention can be easily dosed when added to a catalytic hydrocarbon cracking unit. The foregoing and other embodiments and advantages of the present invention will become more apparent upon viewing the detailed description, examples and claims that follow.

DETAILED DESCRIPTION OF THE INVENTION, Grinding wet media is the preferred process for making the passivating agent dispersions of the present invention. Metal passivating agents can be wet milled at levels that are not achievable with dry milling techniques. In general, the fundamental characteristics of material crushed in wet mill, particularly the particle size is determined by various process variables. For example, the type of mill can affect the fundamental characteristics of the crushed materials. The type of mill can also determine how quickly a particular result can be achieved. Other factors also determine the fundamental characteristics of the crushed material, as well as the time and energy required to achieve them. Such factors include the following: (1) In wet milling, smaller media are more efficient at producing finer particles within 10 minutes and less. (2) Heavier media and higher extreme speeds are desired to impart greater energy to the particles that are crushed. (3) Lower fluid viscosities are beneficial in particle grinding. (4) As the particles are reduced in diameter, the area of the exposed surface is increased, and the dispersing agent is used to keep the small particles preventing agglomeration. As used herein, "particle size" refers to the average volumetric particle size measured by conventional particle size measurement techniques such as sedimentation, photon-correlation spectroscopy, flow-field fractionation, disk centrifugation, electron microscopy. transmission, and dynamic light scattering. A dynamic light scattering device such as Horiba LA-900 Laser Scattering Particle Size Analyzer (Horiba Instruments, Irvine, California) is preferred by the present inventors, for its advantages of easy sample preparation and speed. The volumetric distribution of the sample is related to its weight distribution.

Grinding equipment The preferred grinding equipment for the practice of the invention is generally known as wet agitation mills in which the grinding medium is stirred in a grinding chamber. The preferred method of agitation is by means of an agitator comprising a rotating handle, such as those found in attrition mills. The handle may be provided with discs, arms, needles or other attachments. The portion of the attachment that is radially the most remote of the handle is referred to herein as the "end". The mills can be continuous or discontinuous, vertical or horizontal. A ball mill is an example of a rudimentary agitated mill. A horizontal continuous medium mill equipped with an internal screen having a size of perforations that are 1/3 of the average diameter is preferred as an efficient medium mill for the practice of the present invention. High media loads are possible (for example, charges of 92%). An increase in the amount of crushing medium in the chamber will increase the efficiency of the crushing by decreasing the distance between individual particles of the grinding medium and increasing the number of surfaces available to split the material to be crushed. The volume of medium of crushing can be increased until the grinding medium constitutes up to 92% of the volume of the grinding chamber (dead space of the chamber is excluded). At levels substantially above this point, the medium obstructs.

Starting materials.

Colloidal dispersions of passivating agents, including antimony, zirconium, tungsten, tin, bismuth, indium, thallium, calcium, tellurium, zinc, cadmium, lithium, germanium, beryllium, magnesium, strontium, aluminum and mixtures, are produced for the present invention. of two or more of the above metals or their compounds. The particular metal or metal compound used is not critical, as long as such metals or metal compounds are insoluble in the dispersion medium and as long as they can be ground according to the techniques described herein. Friable solids are most preferred. Accordingly, a wide variety of compounds can be used for the practice of the present invention, including metal oxides, carbonates, orthophosphates, sulfides, halides, hydrides, hydroxides, selenides, antimonides, nitrides and sulfates. Most readily available compounds are readily available, cheap, such as oxides, hydroxides and carbonates. Within the ratio, the size of the feed material to be ground is not critical, for example, antimony trioxide can be reduced to about 0.10 microns of average particle size with a stirred medium mill using the process of the present invention, both starting from particles that have a particle size of 4 microns, 2 microns or 0.6 microns. However, the feed material should preferably not be greater than 10% of the size of the grinding medium. Other metal passivating agents can be similarly reduced to an average particle size of 0.25 microns or less in small crushing times. Generally, according to the present invention, the average particle size of ground passivating agents is not greater than 0.5 microns, more preferably 0.25 microns, and more preferably 0.1 microns. Preferably, at least 99% of the ground passivation agent has sizes less than 1 micron, and more preferably, 0.3 microns. Faster milling times can be achieved, if smaller starting materials are used. Therefore, it is preferable to start with particles that are as small as economically possible, to reduce the grinding time. For example, a 0.6 micron antimony trioxide feed material (measured by electron transmission microscopy) can be crushed to a desired size (e.g., 1 micron) in a shorter time than a 4 micron material. For this reason, antimony trioxide having an average particle size of 0.6 microns is preferred to the starting material having a larger particle size. When such material is used, a more tight particle distribution can be achieved, as well as a short grinding time.

Crushing medium.

Acceptable grinding media for the practice of the present invention include sand, glass beads, metals and ceramics. Preferred glass beads include barium (lead) carbonate titanates (lead-free) and borosilicates. Preferred metals include carbon steel, stainless steel, and tungsten carbide. Preferred ceramics include zirconium oxides stabilized with yttrium, zirconium silicate and alumina. The most preferred grinding media for the purpose of the invention is zirconium oxide stabilized with Itrium. Each type of medium has its own advantages. For example, metals have high specific gravity, which increases the grinding efficiency due to an increased impact. Metals cost little to much, and pollution can be a problem. The glasses are advantageous from the point of view of low cost and the availability of small sizes as low as 0.004 mm. Such small sizes make possible smaller final particle sizes. The specific gravity of the glasses, however, is less than other means and longer grinding times are required. Finally, the ceramics are advantageous from the point of view of their low contact, low porosity and ease of cleaning. The grinding medium used for the reduction of the particle size is preferably spherical. As previously noted, smaller grinding media sizes result in smaller final particle sizes. The grinding medium for practicing the present invention preferably has an average size in the range of 0.004 to 1.2 mm, more preferably 0.012 to 0.2 mm. Using a properly selected grinding media, the milling process of the present invention actually grinds the particles, instead of deagglomerating clumps of particles - a task for which the media mills are normally used.

Fluid vehicles The fluid vehicles in which the particles can be ground and dispersed include water, and organic liquids such as hydrocarbon oils, alcohols and ethylene glycol. In general, while the used fluid vehicle has a reasonable viscosity and does not adversely affect the physical and chemical characteristics of the particles, the choice of fluid is optional. Water is ordinarily preferred. Occasionally, aqueous suspensions also have to rest at ambient temperatures below 0 ° C, so an antifreeze should be introduced into the suspension if required. Preferred antifreezes include ethylene glycol, methanol, ethanol, isopropanol, acetone and mixtures thereof. Ethylene glycol is the most preferred.

Dispersing agents.

The dispersing agents preferably act to wet the newly exposed surfaces when the particles are opened. The dispersing agents also preferably stabilize the resulting slurry of the ground particles by provision of either (1) a positive or negative electrical charge on the ground particle or (2) a spherical block through the use of a very bulky molecule. An electrical charge is preferably introduced by means of anionic and cationic surfactants, while the spherical blocking is preferably performed by polymers absorbed with charges on the particle that repel one another. Zwitterionic surfactants can have both characteristics of anionic and satonic surfactants on the same molecule. Preferred dispersing agents for the practice of the invention include wetting agents (such as Triton X-100 and Triton CF-10, sold by Union Carbide, Danbury Connecticut, and NEODOL 91-6, sold by Shell Chemical) and anionic surfactants (such as TAMOL 731, Tamol 931, ta ol 165 A and TAMOL-SN sold by Rohm and Haas, Philadelphia, Pennsylvania, COLLOID 22/35, sold by Rhone Poulenc, Philadelphia, Pennsylvania, and SURFYNOL CT-131 made by Air Products in Allentown, Pennsylvania). Other anionic surfactants include copolymer salts of acrylic acids such as BYK-156 from Byk Chemie, Wellingford, Connecticut or DURAMAX-3007 from Rohm and Haas. Also preferred are. cationic dispersants (such as DISPERBYKE 182 sold by Byke Chemie); amphoteric surfactants (such as CROSULTAIN T-30 and INCROSOFT T-90, sold by Croda Inc., Parsippany, New Jersey); and non-ionic surfactants (such as DISPERSE-AYD-22 sold by Daniel Products Co., Jersey City, New Jersey, BRIJ-30 sold by IC1 in Wilmington, Delaware and SURFYNOL CT-111 sold by Air Products). For non-aqueous systems, preferred dispersants include phosphoric esters of ethylene oxide adducts (such as PHOSPHA D6N made by Syntron Inc. of Morgantown, North Carolina). The most preferred dispersing agents are anionic surfactants such as TAMOL-SN which can act as both grinding aid and dispersant in aqueous systems Other grinding parameters.

The relative proportions of particles to be crushed, fluid vehicles, grinding media and dispersing agents. they can be optimized by the practice of the present invention. Preferably, the final slurry leaving the mill comprises the following; (1) 10 to 60% by weight, more preferably 15 to 45% by weight, even more preferred approximately 40% by weight of the particle to be ground; (2) 1 to 8% by weight, more preferably 2 to 6%, even more preferably about 4% by weight of dispersing agent; and (3) the fluid vehicle balance. Preferably the loading of the grinding medium as a percentage of the volume of the grinding chamber is from 80 to 92%, more preferably from 85% to 90%. The speed of the agitator controls the amount of energy that is put into the mill. The higher the speed of the agitator, the more kinetic energy is put into the mill. Higher kinetic energies result in an increase in the efficiency of the crushing, due to the highest impact and cut. Therefore, an increase in the RPM of the agitator results in an increase in the efficiency of the crushing. Although it is generally desirable, it is understood by those with knowledge in the subject that an increase in efficiency will be accompanied by a concurrent increase in the temperature of the chamber and the contact relationship. The extreme speed of the agitator represents the maximum speed (and, therefore, kinetic energy) experienced by the particles to be ground. Therefore, mills of larger diameters can impart speeds equal to those of smaller mills at lower RPM. The residence times (referred to globally as retention time) is the amount of time that the material passes in the grinding chamber while it is exposed to the grinding medium. The residence time is calculated by simple determination of the grinding volume that is available for the mill and dividing this figure by the flow ratio through the mill, yield ratio. In general, a certain residence time will be required to achieve the fundamental characteristics of the desired product (for example, final product size). If this residence time can be reduced, a higher performance ratio can be achieved, minimizing capital costs. For the practice of the present invention the residence times may vary, but it is preferably less than 15 minutes, and more preferably less than 10 minutes. Mills of two or more stages in series are usually desirable, particularly when drastic reductions in particle size are necessary to optimize grinding efficiency. The reduction of maximum particle size within a given milling step is typically in the range of about 10: 1 up to as much as 40: 1 and is to some extent dependent on the average size. As a result, the number of milling stages increases while the size reduction requirements increase. Effects similar to those of stage mills can be achieved by using a single mill by collecting the outlet and repeatedly feeding the outlet through the mill. However, the residence time may be longer to reach the final particle size.

ADDITION METHOD The dispersions of the present invention are added to the catalytic cracking unit of hydrocarbons in a controlled manner, preferably by addition of the dispersion in the cracking reactor, both in the feed stream and by introducing a separate stream in the cracking reactor, or by introduction of the dispersion in the catalyst regenerator. As stated above, the dispersions of the present invention are advantageous for this purpose, insofar as they are stable, easily and precisely dosable, have low viscosity, and are economical with respect to other commercially available passivation agents such as organometallic complexes.

EXAMPLES The following examples, as well as the previous description of the invention and its various embodiments, are not intended to be limiting of the invention but rather to illustrate the invention. Those with knowledge of the art can formulate other embodiments included within the scope of the present invention.

EXAMPLE 1 A 10 liter horizontal continuous medium mill (Netzsch, Inc. Exton, Pennsylvania) was filled 90% with YTZ medium (zirconium oxide stabilized with Itrium) with an average diameter of 0.2 mm and a specific gravity of 5.95. (Tosoh Corp., Bound Brook, New Jersey). A 0.1 mm screen was installed inside the mill at the exit. Forty-five pounds of antimony trioxide with an average initial particle size of 2.0 microns (Anzon, Ine, A Cookson Group Company, Philadelphia, Pa.) Were used to make an aqueous paste with 55 pounds of water and 4.5 pounds of TAMOL- SN. The mill was operated at an extreme speed that averaged 2856 feet per minute. After 7.5 minutes of retention time (5 passes through the mill) the average particle size, in volume, was reduced to 0.102 microns and 99.9% of the particles had sizes smaller than 0.345 microns when they were measured in an analyzer of particle size Horiba A 900. The material produced in the middle of the mill showed no signs of depositing overnight. Even after a month of deposit, only a very thin layer appeared on the top. The dispersion appeared to be a uniform gel, which flowed easily by applying a minimum cut.

EXAMPLE 2 The same mill, medium and load as in the example 1 were used. This time the feed of antimony trioxide having a particle size of 0.6 microns was used (Anzon, Inc.). Thirty pounds of antimony trioxide formed an aqueous paste with 70 pounds of water and 1.8 pounds of TAMOL-SN and 0.9 pounds of Triton CF-10. The extreme speed during the run averaged 2878 feet per minute. After 4.8 minutes of retention time in the mill (4 passes), the average particle volume was 0.11 microns and 99.9% of the particles were smaller than 0.31 microns.

EXAMPLE 3 The same mill, medium and load as in Example 1 were used. Thirty pounds of 4 micron antimony trioxide feed material formed an aqueous paste with 70 pounds of water and 2.8 pounds of TAMOL-SN. The extreme speed was 2860 feet per minute. After 7.0 minutes of retention time in the mill (4 passes), the average particle volume was 0.10 microns and 99.9% of the particles were smaller than 1.2 microns.

EXAMPLE 4 The same mill, medium and load as in Example 1 were used. This time zirconium carbonate (MEI, Flemington, New Jersey), with a particle size of 25 microns was used. Twenty pounds of zirconium carbonate formed an aqueous paste with 25 pounds of water and 2.0 pounds of TAMOL-SN. After 80 minutes in recirculation mode (24 turns of feed tanks) the average particle size was 0.112 microns and 99.9% of the particles were smaller than 0.301 microns. The extreme speed was 2820 feet per minute.

EXAMPLE 5 A 0.5 l horizontal continuous medium mill (Netzsch) was filled 90% with YTZ medium (zirconium oxide stabilized with Itrium) with an average diameter of 0.22 mm and a specific gravity of 5.95.

(Tosoh Corp., Bound Brook, New Jersey). A 0.1 mm screen was installed inside the mill at the exit. 500 g of tungsten trioxide (Aldrich Chem Co., Gillingham, United Kingdom of Great Britain) with a particle size average starting 4.1 microns were used to make a slurry with 1000 g of water and 5 g of dispersant Duramax D3007 . The mill was operated at an extreme speed that averaged 1803 feet per minute. After 10 passes through the mill, the paste was then recirculated at a pumping speed of 1.44 liters per minute. After 32 minutes of recirculation, the average particle size was 0.09 microns, with 99.9% of the particles having sizes less than 0.2 microns.

EXAMPLE 6 The same mill, medium and filler as in Example 5 was used. 500 g of bismuth oxide (Aldrich Chem. Co., Gillingham, United Kingdom of Great Britain) with a particle size average starting 4.1 microns were used to make a slurry with 1000 g of water and 5 g of dispersant Duramax D3007 (Rohm and Haas, Philadelphia, Pennsylvania). The mill was operated at an extreme speed that averaged 1803 feet per minute. After one pass through the mill, the average particle size was 0.103 microns, with 99.9% of the particles having sizes less than 0.315 microns.

EXAMPLE 7 The same mill, medium and filler as in Example 5 was used. 1000 g of indium trioxide (Arconium, Providence, Rhode Island) with an average starting particle size of 2.1 microns were used to make an aqueous paste with 1000 g of water and 10 g of Darvan dispersant. The pH was adjusted to 9 to help the dispersion. The mill was operated at an extreme speed that averaged 1803 feet per minute. After five passes through the mill, the paste was then recirculated through the mill at a pumping speed of 1.44 liters per minute. After 45 minutes of recirculation, the average particle size was 0.2 microns, with 99.9% of the particles having sizes smaller than 0.4 microns.

EXAMPLE 8 The same mill, medium and filler as in Example 5 were used. 500 g of tin oxide (Aldrich Chem. Co., Gillingham, United Kingdom) with an average starting particle size of 2.6 microns were used to make an aqueous paste with 1000 g of water and 5 g of Duramax dispersant D3007 The mill was operated at an extreme speed that averaged 1803 feet per minute. After five passes through the mill, the paste was then recirculated through the mill at a pumping speed of 1.44 liters per minute. After 1 hour and 6 minutes of recirculation, the average particle size was 0.098 microns, with 99.9% of the particles having sizes less than 0.210 microns.

EXAMPLE 9 The same mill, medium and load as in Example 5 were used. 500 g of zinc orthophosphate (BDH) with an average starting particle size of 25.5 microns were used to make an aqueous paste with 1300 g of water and 5 g of Duramax D3007 dispersant. The mill was operated at an extreme speed that averaged 1803 feet per minute. After five passes through the mill, the paste was then recirculated through the mill at a pumping speed of 1.44 liters per minute. After 1 hour of recirculation, the average particle size was 0.1 microns, with 99.9% of the particles having sizes less than 0.236 microns.

EXAMPLE 10 (Comparative) This time a dispersion mill model OB- 20 (Kady International, Scarborough, Maine) Kady operating at a tip speed of 9000 feet per minute was used to disperse and deagglomerate a feedstock of antimony trioxide 1.34 microns of average starting particle size with 99.9% of the particles having less than 4.68 microns. As in Example 1, 4.5 pounds of TAMOL-SN dispersant, 45 pounds of antimony trioxide and 55 pounds of water were loaded into the mill. The particle distribution was monitored versus time. After 20 minutes of mixing, the average particle size was 0.988 microns. After 160 minutes the average particle was 1,048 microns. It is believed that some de-agglomeration occurred at the beginning of the run. In contrast to milling wet medium with appropriate medium, even after 160 minutes, no fine particle below 0.2 micron was present. The next day the solids had been deposited approximately 25% from the surface, leaving a clear layer on top. After one week, the solids settled more than 50%.

EXAMPLE 11 (Comparative) The Kady dispersion mill was operated at an extreme speed of 9000 feet per minute was used to disperse and deagglomerate an antimony trioxide feed material of 0.750 microns of average particle size with 99.9% of the particles that they had sizes smaller than 3.95 microns. The amounts of antimony trioxide, TAMOL-SN, and water were the same as those of Example 1. Again, the particle size was monitored versus time. After 45 minutes the average particle size was 0.784 microns with 99.9% of the particles that had sizes less than 3.024 microns. In contrast to grinding wet media with appropriate medium, even after 60 minutes, no fine particles below 0.2 microns were present. The dispersion was not stable and during the night the antimony trioxide solids were deposited approximately one third, leaving a clear layer on top. Based on the comparison of Example 1 with Examples 10 and 11, it is seen that, by grinding wet media (in which the particles are broken at average particle sizes less than 0.11 microns), stable upper dispersions can be produced by the formation of such fine particles.

It is noted that in relation to this date, the best method known to the applicant, to implement said invention is that which is clear from the manufacture of the objects to which it refers.

Having described the invention as above, the content of the following is claimed as property.

Claims (34)

1. A stable dispersion, characterized in that it comprises: a fluid vehicle; a dispersing agent; and finely ground particles of one or more metals or metal compounds for passivation of 10 cracking catalysts contaminated with metals within a catalytic cracking unit of hydrocarbons, said • particles have an average volumetric particle size of less than 0.1 microns and less than 99% of those particles have less than 1 micron.

2. The dispersion of claim 1, characterized in that at least 99% of said particles have sizes less than 0.

3 microns. • The dispersion of claim 1, characterized in that said metal or metal compound is selected from the group consisting of antimony, zirconium, tungsten, tin, bismuth, indium, thallium, calcium, tellurium, zinc, cadmium, lithium, germanium, beryllium, magnesium, 25 strontium, aluminum and compounds thereof.

4. The dispersion of claim 3, characterized in that said metal or metal compound is selected from antimony oxides, bismuth oxides, tin oxides, tungsten oxides and zirconium carbonates.

5. The dispersion of claim 4, characterized in that said metal or metal compound is antimony trioxide.

6. The dispersion of claim 1, characterized in that said fluid carrier is selected from the group consisting of hydrocarbon oils, alcohols and ethylene glycol.

7. The dispersion of claim 1, characterized in that said fluid vehicle is water.

8. The dispersion of claim 1, characterized in that said dispersing agent is selected from the group consisting of cationic surfactants, amphoteric surfactants, and nonionic surfactants.

9. The dispersion of claim 1, characterized in that said dispersing agent is selected from the group consisting of wetting agents and anionic surfactants.

10. The dispersion of claim 1, characterized in that it also comprises an antifreeze.

11. The dispersion of claim 10, characterized in that said antifreeze is selected from the group consisting of ethylene glycol, methanol, ethanol, isopropanol, acetone.

12. A process for producing a stable dispersion, characterized in that it comprises: loading a stirred medium mill with a grinding medium, a fluid vehicle, a dispersing agent and particles of a metal or metal compound for passivation of metal-contaminated cracking catalyst; and stirring said grinding medium, fluid vehicle, and particles until a dispersion is formed, wherein said particles are reduced in size by at least 10% and have an average volumetric particle size of less than 0.1 microns, whereby less 99% of said particles are smaller than 1 micron.

13. The process of claim 12, characterized in that said stirred medium mill is operated at an extreme speed in the range of 1000 to 6000 feet per minute.

14. The process of claim 12, characterized in that said grinding means is provided with an amount sufficient to fill approximately 80 to 92% of the volume within said mill.

15. The process of claim 12, characterized in that said grinding means is selected from the group consisting of sand, glass beads, metals and ceramics.

16. The process of claim 15, characterized in that said communication means is selected from the group consisting of barium titanate, sodium carbonate and lead, borosilicate, carbon steel, stainless steel, tungsten carbide, zirconium silicate, alumina.

17. The process of the rei / indication 16, characterized in that said medium is stabilized with zirconium oxide.

18. The process of claim 12, characterized in that said metal or metal compound is selected from the group consisting of antimony, zirconium, tungsten, tin, bismuth, indium, thallium, calcium, tellurium, zinc, cadmium, lithium, germanium, beryllium, magnesium, strontium, aluminum and compounds thereof.

19. The process of claim 18, characterized in that said metal or metal compound is selected from the group consisting of antimony oxides, bismuth oxides, tin oxides, tungsten oxides and zirconium carbonates.

20. The process of claim 12, characterized in that said fluid carrier is selected from the group consisting of hydrocarbon oils, alcohols and ethylene glycol.

21. The process of claim 12, characterized in that said fluid vehicle is water.

22. The process of claim 12, characterized in that said dispersing agent is selected from the group consisting of cationic surfactants, amphoteric surfactants, and non-ionic surfactants.

23. The process of claim 12, characterized in that said dispersing agent is selected from the group consisting of wetting and wetting agents or anionic surfactant wetting agents.

24. The process of claim 12, characterized in that it also comprises an antifreeze.

25. The process of claim 12, characterized in that said antifreeze is selected from the group consisting of ethylene glycol, methanol, ethanol, isopropanol, acetone.

26. A process for passivating a contaminating metal on a hydrocarbon cracking catalyst characterized in that it comprises contacting said catalyst within a catalytic cracking unit of hydrocarbons with a stable dispersion, said dispersion comprising a fluid carrier, a dispersing agent, and finely particulate ground from one or more metals or metal compounds for passivation of a metal-contaminated cracking catalyst within a catalytic cracking unit for hydrocarbons, said particles having an average volumetric particle size of less than 0.1 microns, and at least 99 % of said particles have a size of less than 1 micron.

27. The process of claim 26, characterized in that at least 99% of said particles have sizes less than 0.3 microns.

28. The process of claim 26, characterized in that said metal or metal compound is selected from the group consisting of antimony, zirconium, tungsten, bismuth tin, indium, thallium, calcium, tellurium, zinc, cadmium, lithium, germanium, beryllium, magnesium. , strontium, aluminum and compounds thereof.

29. The process of claim 28, characterized in that said metal or metal compound is selected from antimony oxides, bismuth oxides, tin oxides, tungsten oxides and zirconium carbonates.

30. The process of claim 29, characterized in that said metal or metal compound is antimony trioxide.

31. The process of claim 26, characterized in that said fluid carrier is selected from the group consisting of hydrocarbon oils, alcohols and ethylene glycol.

32. The process of claim 26, characterized in that said fluid vehicle is water.

33. The process of claim 26, characterized in that said dispersing agent is selected from the group consisting of cationic surfactants, amphoteric surfactants, and nonionic surfactants.

34. The process of claim 26, characterized in that said metal or metal compound is antimony trioxide.