US3306760A

US3306760A - Process for carrying out gas phase reactions

Info

Publication number: US3306760A
Application number: US421862A
Authority: US
Inventors: Zirngibl Hans; Brandle Karl; Beumer Peter; Weidmann Walter
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1964-01-04
Filing date: 1964-12-29
Publication date: 1967-02-28
Anticipated expiration: 1984-02-28
Also published as: DE1442690A1

Description

Feb. 28, 1967 ZlRNGlBL ET AL 3,306,?60

PROCESS FOR CARRYING OUT GAS PHASE REACTIONS Filed Dec. 29, 1964 7 I i J J FIG? MLH. L Y y x ,v 7 7 ,/'7 6 2 2 s F l W INVENTORSI PETER BEUMER, WALTER WEIDMANN.

A TTORNEY /-M Z/PNG/BL, KARL BRANDLE,

United States Patent 12 Claims. (61. 106-288) This invention relates to a continuous process for carrying out exothermic or weakly endothermic reactions between reaction components in gaseous and/or vapour phases and/ or solid phases for the production of finely divided inorganic solid substances. By reaction of preferably vaporizable metalor semi-metal halides with, for example, air, oxygen, water or ammonia, it is possible to obtain oxides, nitrides or borides etc. in finely divided form.

Numerous processes are known, for example, for burning titanium tetrachloride. One principle of the process consists in the introduction of the reaction components into the combustion chamber through nozzles or tubes fitted concentrically one within the other. However, such an arrangement has the disadvantage that only small space by volume productions are possible, since these burners cannot be given arbitrary dimensions. The production of relatively large quantities of a substantce consequently necessitates a relatively large number of juxtaposed burners of complicated design. A second disad vantage of this method is that solid deposits of the reaction products are formed at the outputs of the burners by partial reaction of the gases so that it is necessary to interrupt the reaction from time to time and dismantle the burner assembly. To prevent crust formation at the burner, it has been proposed to add sand to the reaction components or to introduce concentric tubes into the gasconducting pipes. These tubes contain a suspension of sand in gas and terminate just before the nozzle so that the propellant gas projects the sand against the nozzle wall and keeps this wall free from growths or clogging substances.

In another process for overcoming these difficulties the burner is modified. The nozzles ejecting the oxidizing gas are positioned in regular formation around the chloride vapour supply pipe. However, the nozzles vary by a small angle both axially and radially from the parallel position in relation to the inlet pipe for the totanium tetrachloride, in such a way that the oxidizing gas performs a spinning movement around the titanium tetrachloride vapour and the mixing then takes place. The crust formed on the supply pipes can however be expelled only to some extent.

The problem of crust formation becomes even more critical when carbon monoxide is also burnt. In this case a certain water content in the gas mixture is necessary. It has been proposed by means of a curtain of protective gas to ensure that the moist gas component does not come into contact with the titanium tetrachloride before the combustion zone, since otherwise deposits are formed on the pipes or tubes due to the hydrolysis reaction which takes place more quickly than the oxidation with oxygen.

To avoid crust formation on the walls of the reactor, inert materials are also used, which are introduced with the gases into the combustion chamber, or porous wall material is employed, through which inert gases or carbon monoxide can be forced.

The aforesaid steps proposed to overcome the danger of crust formation require a complicated construction of the burner or of the nozzle assembly. In addition, it

"ice

is uneconomical to use relatively large quantities of inert gas, as propellant gas for sand, as protective gas during the additional combustion of carbon monoxide or as protective gas when porous pipes are installed.

In another process described the reaction is carried out in a bed of inert material. However, this process has the essential disadvantage that the reaction product is very strongly deposited on the inert material and the bed must be continually renewed. The losses of titanium dioxide are considerable. In order to recover the titanium dioxide as tetrachloride the discharged bed material must be chlorinated or coarse titanium dioxide is used as inert material and the discharge is employed for ceramic purposes. In addition, also in this process, crust formation occurs at the inlet openings of the reaction gases which are situated in or beneath the fluidized bed.

The proposed modification of this process, in which the gases are heated in a fluidized bed but are injected at such a velocity into the bed that the reaction takes place, at least in part, above the fluidized bed, avoids deposition of the final products on the inert material only partially.

The present invention relates to a process for carrying out exothermic or weakly endothermic chemical reactions between gases and/or vapours or between gases and/or vapours and solid phases, with preheating of the reactants, and/ or in the presence of an exothermic chemical auxiliary reaction in the reaction chamber, wherein one or more reaction components are introduced at least in part through a supply container for abrasive granules, which container is connected to the lower part of a vertical reactor which opens conically in an upward direction and the other reaction component or components are injected into the reaction zone at a point where the container widens transversely of the other upwardly flowing reaction components above the supply container, and wherein the reaction is effected substantially above the container of the inert material.

The present process avoids the difliculties and disadvantages previously described. The reaction can take place continuously without any crust formation at the gas inlet openings and without any substantial deposits of the reaction products on the inert bed material, especially if the following conditions are applied:

(a) The velocity of the reaction components introduced through the supply container is kept below the velocity of the abrasive granules necessary for the suspending, preferably between 0.5 to 6 times the loosening velocity.

(b) The laterally introduced reaction components are injected through nozzles in a cross direction to the upwardly streaming reaction components, which nozzles are set from 10 to to a tangent to the reactor and inclined upwardly or downwardly by from 0 to 25 relatively to the horizontal, the injection velocity amounting to at least 5 times the suspending velocity of the abrasive granules.

(c) The preheating of the reactants flowing through the bed of the abrasive granules is adjusted to obtain a temperature in these reactants higher than that of the laterally entering reactants.

The process is especially suitable for the production of finely divided metal oxides of titanium dioxide and silicon dioxide by combustion of the corresponding metal halides in vapour form, preferably as the chlorides, in a stream of air, oxygen or oxygen enriched air at temperatures from 800 to 1300 C., the preferred temperature for the combustion of TiCl to TiO and C1 being in the range from 950 to 1150 C.

The new process is more fully explained below by ref erence to the thermal decomposition of titanium tetrachloride with air or oxygen.

The reactor is made of ceramic material (see FIGURES 1, 2 and 3) and comprises a cylindrical supply container 3 for the abrasive granules, a reaction zone or combustion chamber 4 widening to form a funnel above the container and a following vertically arranged cylinder 6, which is the residence zone or secondary reaction zone. One or more of the gaseous or vaporous reaction components is supplied through the abrasive granules, but at a velocity Which is below the velocity necessary to suspend the inert material. The velocity is preferably from 0.5 to 6 times the loosening velocity. A number of nozzles open laterally into the reaction zone. The other gaseous or vapour reactants or a suspension of solid substances in gas are injected through the nozzles. They are homogeneously mixed with the stream of gas or vapour entering the bed and simultaneously react with them. It is an essential feature of the process that the reaction should take place entirely above the bed of the abrasive granules. The solid, finely divided titanium dioxide is ejected by the constant gas stream upwardly through a wide pipe, the walls of which can be kept at temperatures below 1000 C. At the outlet from the reactor, it can be further cooled by cold return reaction gas or other inert gases and/or a sand cooler and be separated by conventional methods, for example, by cyclones and dust filters from the reaction gas.

The oxidizing gas or gas mixture is advantageously injected into the conical reaction chamber through nozzles arranged in annular formation transversely of the direction of flow of the gas from the bed. The nozzles are directed radially towards one another and are set at an angle from 10 to 80 relatively to a tangent to the chamber in order to cause the generation of a rotational movement in the gas, which produces a return suction. In addition the nozzles are directed upwardly or downwardly in relation to a horizontal plane, possibly at a small angle of from 0 to The gases or when using solid reactants, preferably the solid suspensions, are injected at a velocity which is several times the suspending velocity of the inert material being used. The velocity should be at least five times the suspending velocity, but preferably the velocity is 10 times this value. However, the velocity can be even higher.

Surprisingly it was observed that, using the precautions described, depending on the velocity used for the laterally entering gases in relation to the cross sections and depending on the spacing of the injection device from the bed of the abrasive granules, a more or less large part of this bed is continuously forced upwardly through the cone and into the vertical reaction tube. This material then rotates around the wall and the gas components are mixed in periods of time which are in the order of second and less. The instantaneous mixing of the reaction components is further enhanced by the fact that a return vortex dependent on the tangential inlet velocity is set up by the widening cone in the mixing chamber. Since the reaction Walls are kept cold and in addition the abrasive granules are kept in circulatary or helical motion around the reactor walls, no crust formation is produced on the walls of the reactor. As already mentioned, the reaction products do not form or clog on the granules, as was observed with former fluidized bed processes. Consequently, the granules do not have to be withdrawn from the reactor for cleansing purposes. It is merely necessary for the losses occurring owing to abrasion to be replaced at intervals.

With the process described above residence times of the reaction products in the reaction chamber of less than 5 seconds and preferably from 0.1 to 1 second are maintained.

In one special embodiment the abrasive granules are continuously withdrawn and fed in again into the reactor to introduce seeding or modifying agents in the simplest possible and most economic manner into the reaction system.

Returned reaction gas or an inert gas can be admixed with the reactant gases.

Some of the nozzles can also be used for introducing a stream of titanium tetrachloride vapour.

The preheated titanium tetrachloride, possibly mixed with proportions of air, oxygen, inert gases, returned reaction gas or additional combustion gas, is advantageously introduced through the bed of the abrasive granules. Preferably a ratio by volume of O :TiCl of between 1.1 and 1.3 is applied. The granules of the bed have a specific gravity from 2 to 5, a grain diameter of from 0.1 to about 4 mm. and are preferably spherical in form and comprise substances with high resistance to abrasion, which are compactly sintered or obtained from melts, for example, oxides such as A1 0 SiO TiO ZrO corresponding mixed oxides or ZrSiO Instead of inert material, it is possible to employ minerals to introduce modifying and seeding agents, for example, strongly burnt mixed oxides or naturally occurring minerals such as zirconium silicate and feldspar, in the required grain size from 0.4 to 3 mm, especially when the preheated titanium tetrachloride is conducted through the inert material. It is obviously also possible to use a mixture of inert material with a material which reacts with the preheated titanium tetrachloride.

In another particular embodiment, 0.5 to 2.5% by weight of aluminum oxide as aluminum chloride and/or about 0.5% by weight of SiO in the form of SiCl are added to the titanium tetrachloride prior to heating or to the supply container containing the inert material granules or to the oxygen-containing gas. Steam which acts as a seeding or nucleus former can be added too and is mixed with the oxidizing gases. In this case, the steam can be introduced into the preheated air by burning substances containing hydrogen in a quantity of 0.05 to 5 mol-percent, preferably from 1 to 3 mol-percent, calculated on the titanium dioxide.

In addition, it is possible to admix hydrogen in small quantities with the preheated titanium tetrachloride and to use the formed sub-halides as nuclei. Hydrogen, possibly with nitrogen as a diluent, is introduced through an inlet into the supply container of the abrisive granules so that from 0.1 to 10% by weight and preferably from 0.5 to 5% by weight of the titanium tetrachloride are reduced to the sub-chloride. The sub-chloride is carried into the reaction zone with the stream of hot titanium tetrachloride.

In one preferred embodiment, the titanium tetrahalide is preheated by resistance or radiation heating or a blown are using the Schonherr principle or by high frequency. It is introduced from below into the furnace through the inert or other material or a mixture of both. The temperature of the titanium tetrahalide is adjusted sufficiently high on the one hand to reach the required temperature in the reaction zone and on the other hand to allow the oxygen-containing gas to be preheated to a temperature below 800 C. and preferably below 500 C. The reaction temperature is preferably from 950 to 1100 C. It is sufficient to preheat the titanium tetrahalide to from 800 to 1000 C., if the oxygen-containing gas is in the region of 500 C.

Another embodiment of the invention is provided when the titanium tetrahalide is not preheated but wherein a quantity of, for example, carbon monoxide, is added sufficient to achieve the reaction temperature. In this particular embodiment, the titanium tetrahalide can also be introduced through the lateral inlets. Also in this case, the reaction takes place in the middle of the furnace and not on the abrasive granules.

Example 1 26 kg. per hour of titanium tetrachloride, in which were dissolved 0.9% by weight of aluminum trichloride, were evaporated at a temperature of 450 C. and reacted in an apparatus illustrated in FIGURE 1. The titanium tetrachloride vapour entered at 1 into an entry compartment, passed through the perforated plate 2, flowed through the container 3 with the inert material (abrasive granules), in this case, sand, which was at a temperature of about 600 C., and then entered the conical reaction chamber 4. 13.5 cubic metres of air (at N.T.P.) per hour were first preheated to 1150" C. and then blown through the nozzles 5 into the oxidation zone. Six nozzles with an internal diameter of 10 mm. were used. The discharge velocity of the gases from the nozzles was 40 m./sec. The molar ratio of TiChzO was 1:1.15. Cold inert material was continuously introduced at 7 into the cylindrical residence zone 6 and correspondingly 'hot material was withdrawn through the pipe 8.

The reaction products were discharged through the outlet 9, cooled in a subsequent sand cooler, and titanium dioxide was separated out in a cyclone and dust filter. The waste gas had the following composition: N =63%; Cl =33.6% and O =2.7%, as well as traces of TiCl The yield was 96%. 87% by weight had a particle diameter between 0.2 and 0.3 The brightening power was 790, measured according to DIN 53,192.

Example 2 30 liters per hour of titanium tetrachloride in which were dissolved 0.9% by weight of AlCl were evaporated, preheated to 450 C. and introduced through the container 3 into the reaction chamber. Together with the titanium chloride, 2 cubic metres of carbon monoxide (at H.T.P.) flowed per hour through the bed. Through four nozzles having a diameter of 7 mm. 12 cubic metres per hour of oxygen (at N.T.P.) were injected. The oxygen was preheated to 300 C. The discharge velocity into the chamber was accordingly about 45 m./ sec. The molar ratio of TiCl :O :CO was 1:1.97:0.33. The reaction temperature was adjusted to about 1050 C. 'A product of good pigment quality was obtained in a yield of 94%. The brightening power according to DIN 53,192 was 805. The composition of the waste gas was 74% of C1 17.1% of O and 7.5% of CO as well as traces of TiCl CO and some HCl.

Example 3 29.7 kg. per hour of SiCl preheated to 350 C., were introduced at 1 into the reactor. 22 cubic metres of moist air (at N.T.P.) were brought to 1200" C. and injected through six nozzles (internal diameter 10 mm.) with a velocity of 70 m./sec. The reaction temperature was in the region of 1020 C.

Cooling and separation of the solid reaction product from the waste gases was eifected in the manner described in Example 1. After one hour 9.8 kg. of silicon dioxide were obtained, which corresponds to a yield of 93%. The product was in very finely divided form. The particle diameter was for the major part below 50 III/.0.

Example 4 A reactor according to the invention is illustrated in the accompanying FIGURE 3. 52 kg. per hour of vaporized titanium tetrachloride are introduced into the reactor at 10 at a temperature of 180 to 200 C. and heated by means of radiation heating to about 1000 C. The titanium tetrachloride is then introduced through a distribution grid 2 consisting of graphite and through a supply chamber 3 filled with the abrasive granules made of Bikorit of a grain size of from 0.2 to 0.5 mm. into the reaction furnace 4 proper. The gas velocity in the body chamber, related to empty space, is 0.9 rn./sec. at 1000 C. This velocity is 6 times the loosening velocity. The suspending velocity based on the conditions obtaining here is 2 m./sec. Through a ring pipe and by means of six nozzles with a total cross-sectional areas of 1.2 cm. oxygen-enriched air (407 oxygen) at a temperature of 400 C. is injected tangentially. The angle of the nozzle in relation to a tangent 'to the chamber is 65 and the upward inclination of the nozzles relatively to the horizontal is 10. The gas discharge velocity from the nozzles is m./ sec. at 400 C. At these velocities, the stream of gas sweeps over the entire cross-sectional area of the chamber.

Due to the tangential admission of the oxygen-enriched air and the upwardly widening cone 4, a return vortex is also produced extending from above towards the centre, which contributes to more rapid mixing. For this arrangement of the nozzles and value of the velocity, the granules are rolled upwardly in a spiral motion over the entire cone and for about from 10 to 20 cm. into the vertical shaft. Due to this movement of the granules and due to the cold layer of gas which is applied to the wall, crust formations on the walls are avoided.

The molar ratio of oxygen to titanium tetrachloride is 1.2. The reaction temperature is between 1050 and 1100 C. and the residence time about 1.5 seconds. At the same time, a quantity of aluminum chloride is introduced below the supply container for the inert granules so that the titanium dioxide formed contains 1% of aluminum oxide. The oxygen-containing gases contain steam in a quantity of 2 mol-percent, calculated on the titanium dioxide forming therefrom. The reaction products are discharged through opening 9 and quickly cooled with returned gas to a temperature below 600 C.

Further operations, such as cooling, dust separation etc., are effected by conventional methods, such as water coolers, cyclones and dust filters., The waste gas has the following composition:

The titanium dioxide formed has a maximum brighten: ing power of 770 to 790, measured according to DIN 53,192 and a narrow particle size distribution.

Example 5 The apparatus and also the quantities of the reactants are the same as described in Example 4, but sand is continuously introduced through the opening 7. This sand is mixed with such a quantity of potassium chloride that the pigment formed contains 20 p.p.m. of potassium. The sand runs continuously by way of the opening 8 out of the reaction container.

Example 6 The arrangement of the apparatus and the quantities of the reactants are the same as in Example 4, with the exception of the oxygen-containing gas. In this case, instead of preheating the titanium tetrachloride by electricity, a quantity of carbon monoxide is injected through the opening 1 that the reaction temperature is adjusted to 1050 to 1100 C. The quantity of carbon monoxide is 3 cubic metres per hour (at N.T.P.). An oxygennitrogen mixture at 400 C. is injected at a velocity of m./sec. through the six nozzles. The molar ratio TiCl :=O :CO:N is l:1.45:0.5:1.05. The reaction temperature, residence time and properties of the product are the same as in Example 4. The composition of the waste gas was: 53.3% C1 5.3% 0 28% N 13.4% CO Example 7 The apparatus and also the quantities of reactants introduced and the reaction conditions correspond to those described in Example 4, 'but in this case the addition of water was omitted. Instead, hydrogen (with nitrogen as diluent gas) was injected into the inert material through an additional inlet. The hydrogen then reacts in this chamber with the superheated titanium tetrachloride to from a titanium sub-chloride which acts as a nucleus. The hydrogen is introduced in such quantities that 1.5% of the titanium tetrachloride were reduced.

By the new process finely divided pigments and fillers can be manufactured, whereby the properties particle size, surface area, color etc.-can be well adjusted to the values desired. These properties can be adjusted e.g. by the temperature conditions in the reaction zone, the residence time of the reaction products in the reactor, the ratio of the reactants and by the addition of modifying additives.

The process can be performed continuously since crust formation on the inlet pipes of the reactants or on the walls of the reactor does not occur. Many processes especially for the combustion of TiCl, to TiO have been proposed in the past, but most of these processes had the disadvantage that they could be performed only batch- Wise. Other processes yielded pigments wit-h unsufficient properties or yielded a gaseous by-product containing chlorine in very high dilution, thus rendering the process uneconomic. The new process avoids the aforementioned disadvantages by combination of the following conditions, described by example of the production of TiO from TiCl which process is a preferred embodiment of the invention. However, it is well known to those skilled in the art that the process described is applicable to the production of other metalor metalloid oxides, such as SiO A1 Fe O ZnO etc., i.e., from the corresponding halides of those elements having atomic numbers from 6 to 30.

As described in FlGUR-ES 1 to 3 the process is performed in a reactor made of refractory inert material, said reactor comprising:

(a) A cylindrical container with a distribution grid filled with abrasive granules which granules can be inert to the reactants or otherwise be made of slowly reacting materials which deliver modifying additives, such as alkali or alkaline earth metal ions or zirconium, aluminum and silicon compounds to dote the titanium dioxide during formation;

(b) A mixing and reaction zone situated on the container for the abrasive materials, said reactor being upwardly conically widened and having nozzles arranged in a ring at the narrow end of said reactor and set from 10 to 80 to a tangent to the reactor and furthermore inclined at an angle relative to the horizontal of between 0 and and (c) The following vertically disposed cylinder (the secondary reaction zone) with an outlet for the reaction products.

In a preferred embodiment the preheated T iCl is introduced through the container for the abrasive material, the temperature of the TiCl being in the range of from 800 to 1200 C., preferably from 950 to 1000 C. The preheating can be performed in the first step 'by heat exchange and in the second step by radiation heating, by electrical resistance heating or by an electric are through which theTiCL, is blown, said electric are working with high voltages and low current according to the Well known Schiinherr principle.

The velocity of the TiCl injected into the container is below the velocity necessary for the suspending of the abrasive materials, however higher than the loosening velocity of said material. The loosening velocity is defined as the velocity necessary to fluidize the particles in the bed (container) Without however carrying said particles out of the bed, i.e. the loosening velocity is the fluidizing velocity as opposed to the suspending velocity. The suspending velocity on the other hand is that velocity at which the particles are entrained in a given flow of a gaseous component, i.e., the suspending velocity is defined as the entraining velocity.

Preferably the velocity of the TiCl is from 0.5 to 6 times the loosening velocity of the abrasive materials.

The oxygen-containing gas is introduced tangentially into the conically shaped mixing and reaction zone, in cross direction to the upward-flow of the TiCl and with a velocity being at least 6 times the loosening velocity of the abrasive granules. Thus, mixing and reaction of the TiCl with the oxygen occur in a zone of high turbulence and within fractions of a second. By the turbulence flow of the react-ants some of the abrasive granules are sucked up and rotate helically along the walls of the reactor. Therefore the TiO;; formed is prevented from adhering to the nozzles and walls of the reactor. The oxygen is injected with a temperature of between 20 and 800 C., preferably of between 200 and 500 C.

The TiO formed together with the gaseous reaction products are ejected via the cylindrical second reaction zone through an outlet and separated from said gases after cooling by conventional methods.

The TiCl can be admixed with modifying compounds such as aluminum halides, preferably aluminum trichloride in an amount of between 0.1 to 8% by weight, preferably 0.5 to 3% by weight, calculated as A1 0 with zirconium tetrachloride in an amount mentioned above, With silicon tetrachloride in an amount being in the range of between 0.05 to 2% by weight, calculated as SiO with phosphorus or antimony halides in the same amount as mentioned for the silicon tetrachloride, with alkali or alkaline earth metal compounds in an amount being in the range of between 0.001 to 2% by weight. Furthermore to the TiCL; there may be added hydrogen in an amount to produce 0.1 to 10% by weight, preferably 0.5 to 5% by weight of titanium sub-chloride calculated on the TiCl used.

We claim:

1. In the process for thermal decomposition of halides of elements selected from the group consisting of aluminum, silicon, titanium, zirconium, iron and zinc with an oxygen containing gas in the vapor phase at temperatures substantially between about 800 and 1300 C., whereby to transform said halides into the corresponding solid finely divided oxides, in which such halide and gas reaction components are introduced into a combustion zone having a fluidized bed of abrasive granules maintained therein, the improvement which comprises maintaining such bed of abrasive granules in fluidized condition in a peripherally outwardly confined vertical lower sub-zone of given flow cross-section by introducing one of said reaction components upwardly through such bed of fluidized granules and into a peripherally outwardly confined vertical upper sub-zone contiguous with and flow connected with the upper end of said lower sub-zone and upwardly and outwardly flaring from a lower end flow cross-section corresponding to that of the lower sub-zone to an upper end flow cross-section correspondingly larger than the lower end flow cross-section at a velocity substantially at least as high as the fluidizing velocity for the bed granules yet below the velocity at which such bed granules become upwardly entrained thereby, introducing the other of said reaction components substantially tangentially inwardly into the upper sub-zone from the periphery of said upper sub-zone near the lower end thereof yet above the bed of granules in said lower sub-zone and in cross direction to the upwardly introduced reaction component at a velocity to provide a velocity within the upper sub-zone and reaction zone of at least five times that of the velocity required to entrain said bed granules, whereby to produce an environment of high turbulence immediately above said bed and within said upper sub-zone up into which a portion of said bed granules is drawn by the suction resulting from the attendant turbulent flow and within which said granules rotate helically predominantly along the confining peripheral portions of said upper sub-zone, for intimate contact and homogeneous intermixing of said one reaction component with said other reaction component in the presence of said portion of granules in said upper sub-zone in said environment of high turbulence, and recovering the resultant solid finely divided oxide thereby produced.

2. Improvement according to claim 1 wherein silicon tetrachloride is upwardly introduced as said one component and an oxygen-containing gas is peripherally inwardly introduced as said other component, and silicon 9 dioxide is produced by thermal decomposition with said oxygen-containing gas.

3. Improvement according to claim 1 wherein the velocity of the upwardly introduced reaction component is between about 0.5 and 6 times the fluidizing velocity for said granules.

4. Improvement according to claim 1 wherein a metal halide is upwardly introduced as said one component and an oxygen-containing gas is peripherally inwardly introduced as said other component.

5. Improvement according to claim 4 wherein said metal halide is titanium tetrachloride and titanium dioxide is produced by thermal decomposition with such oxygen-containing gas.

6. Improvement according to claim 5 wherein the ratio of oxygen in said oxygen-containing gas to said titanium tetrachloride is between about 1.11.3:1, wherein the residence time in said upper sub-zone is between about 0.1 and 1 second, and wherein prior to introduction said titanium tetrachloride is preheated to a temperature between about 950 and 1000 C. and said oxygen-containing gas is preheated to a temperature between about 200 and 500 C.

7. Improvement according to claim 5 wherein the residence time of said titanium tetrachloride in said upper sub-zone is kept below 5 seconds.

8. Improvement according to claim 5 wherein said titanium tetrachloride is preheated in said upper sub- Zone by burning carbon monoxide admixed therewith in an auxiliary exothermic reaction therein.

9. Improvement according to claim 5 wherein subchloride formation is carried out by introducing a modifying and nucleus-forming agent into said upper subzone.

10. Improvement according to claim 5 wherein subchloride formation is carried out by introducing into said upper sub-zone a modifying and nucleus-forming agent selected from the group consisting of aluminum chloride, zirconium chloride, silicon chloride, steam,

alkaline earth metal salts, and

alkali metal salts, hydrogen.

11. Improvement according to claim 5 wherein subchloride formation is carried out by introducing into said upper sub-zone a modifying and nucleus-forming agent selected from the group consisting of aluminum trichloride calculated as A1 0 in an amount between about 0.1 and 8% by weight, silicon tetrachloride calculated as SiO in an amount of about 0.05 and 2% by weight, steam in an amount between about 0.05 and 5 mol percent and hydrogen in an amount suflicient to produce between about 0.1 and 10% by weight of titanium subchloride based on the TiCL; used.

12. Improvement according to claim 5 wherein subchloride formation is carried out by introducing into said upper sub-zone as modifying and nucleus-forming agent a material containing mixed oxides.

References Cited by the Examiner UNITED STATES PATENTS 2,760,846 8/1956 Richmond et al. 106-300 2,949,347 8/1960 Van Pool 23-288 3,042,498 7/1962 Norman 23-277 3,073,712 1/1963 Wigginton 106-300 3,109,708 11/1963 Walmsley 106-300 3,148,027 9/1964 Richmond 106-300 3,174,873 3/1965 Callow et al. 106-300 3,208,866 9/1965 Lewis et al. 106-300 3,219,420 11/1965 Dielenberg 23-284 3,219,468 11/1965 Evans et al. 106-300 FOREIGN PATENTS 505,775 9/1954 Canada.

860,301 2/1961 Great Britain.

890,226 2/ 1962 Great Britain.

HELEN M. MCCARTHY, Acting Primary Examiner.

TOBIAS E. LEVOW, S. E. MOTT, Assistant Examiners.

Claims

1. IN THE PROCESS FOR THERMAL DECOMPOSITION OF HALIDES OF ELEMENTS SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, SILICON, TITANIUM, ZIRCONIUM, IRON AND ZINC WITH AN OXYGEN CONTAINING GAS IN THE VAPOR PHASE AT TEMPERATURES SUBSTANTIALLY BETWEEN ABOUT 800 AND 1300*C., WHEREBY TO TRANSFORM SAID HALIDES INTO THE CORRESPONDING SOLID FINELY DIVIDED OXIDES, IN WHICH SUCH HALIDES AND GAS REACTION COMPONENTS ARE INTRODUCED INTO A COMBUSTION ZONE HAVING A FLUIDIZED BED OF ABRASIVE GRANULES MAINTAINED THEREIN, THE IMPROVEMENT WHICH COMPRISES MAINTAINING SUCH BED OF ABRASIVE GRANULES IN FLUIDIZED CONDITION IN A PERIPHERALLY OUTWARDLY CONFINED VERTICAL LOWER SUB-ZONE OF GIVEN FLOW CROSS-SECTION BY INTRODUCING ONE OF SAID REACTION COMPONENTS UPWARDLY THROUGH SUCH BED OF FLUIDIZED GRANULES AND INTO A PERIPHERALLY OUTWARDLY CONFINED VERTICAL UPPER SUB-ZONE CONTIGUOUS WITH AND FLOW CONNECTED WITH THE UPPER END OF SAID LOWER SUB-ZONE AND UPWARDLY AND OUTWARDLY FLARING FROM A LOWER END FLOW CROSS-SECTION CORRESPONDING TO THAT OF THE LOWER SUB-ZONE TO AN UPPER END FLOW CROSS-SECTION CORRESPONDINGLY LARGER THAN THE LOWER END FLOW CROSS-SECTION AT A VELOCITY SUBSTANTIALLY AT LEAST AS HIGH AS THE FLUIDIZING VELOCITY FOR THE BED GRANULES YET BELOW THE VELOCITY AT WHICH SUCH BED GRANULES BECOME UPWARDLY ENTRAINED THEREBY, INTRODUCING THE OTHER OF SAID REACTION COMPONENTS SUBSTANTIALLY TANGENTIALLY INWARDLY INTO THE UPPER SUB-ZONE FROM THE PERIPHERY OF SAID UPPER SUB-ZONE NEAR THE LOWER END THEREOF YET ABOVE THE BED OF GRANULES IN SAID LOWER SUB-ZONE AND IN CROSS DIRECTION TO THE UPWARDLY INTRODUCED REACTION COMPONENT AT A VELOCITY TO PROVIDE A VELOCITY WITHIN THE UPPER SUB-ZONE AND REACTION ZONE OF AT LEAST FIVE TIMES THAT OF THE VELOCITY REQUIRED TO ENTRAIN SAID BED GRANULES, WHEREBY TO PRODUCE AN ENVIRONMENT OF HIGH TUBULENCE IMMEDIATELY ABOVE SAID BED AND WITHIN SAID UPPER SUB-ZONE UP INTO WHICH A PORTION OF SAID BED GRANULES IN DRAWN BY THE SUCTION RESULTING FROM THE ATTENDANT TURBULENT FLOW AND WITHIN WHICH SAID GRANULES ROTATE HELICALLY PREDOMINANTLY ALONG THE CONFINING PERIPHERAL PORTIONS OF SAID UPPER SUBZONE, FOR INTIMATE CONTACT AND HOMOGENEOUS INTERMIXING OF SAID ONE REACTION COMPONENT WITH SAID OTHER REACTION COMPONENT IN THE PRESENCE OF SAID PORTION OF GRANULES IN SAID UPPER SUB-ZONE IN SAID ENVIRONMENT OF HIGH TURBULENCE, AND RECOVERING THE RESULTANT SOLID FINELY DIVIDED OXIDE THEREBY PRODUCED.