CA1105712A - Controlled carbo-chlorination of kaolinitic ores - Google Patents
Controlled carbo-chlorination of kaolinitic oresInfo
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- CA1105712A CA1105712A CA300,834A CA300834A CA1105712A CA 1105712 A CA1105712 A CA 1105712A CA 300834 A CA300834 A CA 300834A CA 1105712 A CA1105712 A CA 1105712A
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- chlorination
- ore
- boron
- carbo
- clay
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Abstract
Abstract A novel improvement in the process for the carbo-chlorination of kaolinitic ores is provided wherein the improvement comprises adding catalytic amounts of boron chloride to the carbo-chlorination step which results in the catalyzed and controlled chlorination of alumina and silica. Preferably, about 0.3 to 5.0 percent of boron chloride per volume of chlorine is added to the chlorina-tion step and in combination with from 5 to 40 percent or more of reductant carbon to provide a conjoint action wherein preferential chlorination of alumina over silica is obtained at low levels of boron chloride and reductant and total chlorination of both alumina and silica are ob-tained at high boron chloride and reductant levels.
Description
Back~round of the Invention .
The present invention relates ~o the controlled production of aluminum ch`loride and silicon chlori~e in the carbo-chlorina~ion o~ kaolinitic ores. Kaolinitic ore S is de~ined as an ore containing a substantial proportion o~ kaolin. More specifically, the instant invention is primarily concerned with the rapid and preferential carbo-chlorination of al.umina over silica in the kaolinite in the ore, by controlling the levels of boron chloride and reductant yresent during the carbo-chlorination step.
Prior Art .
Thcre have been some references in the prior art to the carbo-chlorination of kaolinitic ores. A distinct characteristic disadvantage of the.se prior art techniques, however, is the act that silicon tetrachloride is normally produced at essentially the same rate and yield as aluminum chloride. This imposes a considerable economic burdell upon these processes for ~he following reasons: (a) carbon is consumed in the carbo-chlorination of the silica; (b) the silicon tetrachloride is very volatile so it ordinarily would be recovered by costly refrlgeration of ~he gases;
and ~c) the recovery of chlorine frorn the sili~on tetra~
chloride by oxldation with oxyg~n is an expensive step.
These prior art limitations have been recognized and are evident by the fact that there has been no con~ercially practiced process for producing aluminum chloride from kaolinitic ores such as clay.
There have been effor~s, however, to develop car-- - , .
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bo-chlorination processes wherein the chlorination of s:ilica is suppressed. See, for example, U.S. Patent Number l,866,731 and British Patent Mumber 305,578, which describe processes ~or the preferential carbo-chlorination of alwnina over silica in clay by recycling large amounts oE sllicon chloride with the chlorine which is taught as suppressing the Eormation oE additional sllicon chloride.
This prior art has apparently never been used commercially, pres~ably because it appears to be i.noperative according to actual laboratory tests and, even if workable, such pro-cesses would require heavy capital costs which must be borne for refrigeration and other equipment to cool the product gases to the very low temperatures necessary to condense out and thus separate and recycle the volatile silicon chloride.
The prior art further discloses, in various forms and fashions, the use of alkali metal compounds as cata lysts for the carbo-chlor-Lnation of aluminous ores, For example, in an article by Ya, E~ Seferovich, J, Chem. Ind.
(Moscow) l934, N, lO, 62-64, the use of alkali metal salts like sodium tetraborate is taught as catalyst during clay carbo-chlorination. This and the other prior art does not teach, however, the use of boron chlorlde gas or boron oxide a~ a catalyst for clay arbo-chlorina~ion, nor has it been recognized that the control of the ratio of alu-mina versu~ silica in carbo- hlorinat~on of clay is p~ssi-ble through con~rol o the amounts and ratio of the reduc-tant to boron chloride and th~ir synergistic action.
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A primary object of the present lnvention is to provide a carbo-chlorination process for the controlled chlorination of alumina over silica in kaolinitic ores to produce alumillum chloridc by substan~ially lncreaslng the ratio of alumlna chlorina~ion tv silica chlorination and whlle maintaining a rapid reaction rate and good percentage of conversion of alumina.
Secondarily, by adjusting the reaction conditions, the silica can be chlorinated in amounts from close to zero up to about equal to that of the chlorinatlon of the alu-mina.
The aluminum chlorlde can be subsequently electro-lyzed to aluminum metal; or used to make aluminum metal by the Toth Aluminum Process, or readily oxidized to aluminum oxide and thereafter converted to aluminum ~etal pursuant to the present well known Hall co~mercial process, or it can be sold as such for many other uses.
A further advantage o the present invention is that i~ allows recycling o~ the gaseous boron chloride carbo~chlorination catalyst by reacting it with clay and/
or reductant, or by dissolving i.t in solven~s like TiC14 followed by vaporization and collection of the B513 vapors.
A furthe* object is to permit the utiliza~ion of low grade bauxite or inexpensive and domestically available kaolinitic ore like clay for producin~ aluminum chloride in a manner which is quicker, less expensive, and does not rely upon imported ores as compared to the traditional Bayer process.
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Another ~dvantaye o.f this inven-tion is the energy savings from: (1) the unexpected important reduction in carbon cons~ ption throucJh the preponderant production of CO2 instead of CO; (2) in tlle satisfactory U9e 0.~ lower carbo-chlorination temperatLIre; (3) the reduction in carbo-chlorination o:E silica with attendant reduction in carbon cons~ption and refrigera-tion-condensation of SiCl~.
According to the present invention, then, there is provided a process for preferentially chlorinating alumina and suppressing the chlorination of silica in a kaolinitic ore consisting of the steps of: drying and oomminuting a kaolinitic ore to form a powdered ora; calcining the powdered ore at a temperature of from about 700 C to 900C to remove water of composition; and carbochlorinating the powdered ore at a temper-ature of ~rom about 600C to 950C to produce aluminum chloride by exposiny the calcined ore to a chlorinating agent in the presence of a carbonaceous reductant in an amo~mt of from abou-t 5% to 40% by weight of the dry ore and boron chloride in an ~nount of from about 0~3~ to 4.0% by volume of the chlorinating agent to preferentially chlorinate alumina and suppress chlorin-ation of silica~ ~
The controlled carbo-chlorin~tion of alumina and silica in kaolinitic ores is achieved by adjusting the levels of reductant between about 5% and 40% or more by weight of dry clay and the level o~ boron chloride between 0.3% to 5.0% by volume of the gaseous chlorinating agent which normally will be dry chlorine. The preferred embodi.ment of the instant invention involves the u~a of lower levels of boron chloride combined with lower levels of reductant such that the carbo-chlorination reac-t-ion is controlled to provide for the preferential chlorination of alumina over silica and simultaneously give a good yieldof chlorinated alumina.
A preferred process sequence utilizing kaolin clay is to initially clry and comminute the clay followed by cal-cination of the clay in the temperature range o~ about 700 C to 900C and in the p.resence of a properly prepared solid reducing agent, the reducing agent being present in an amount of from about 10% to 40~ of fixed carbon, based on the weight of the . dry ore. In this way, the solid reductant and the clay are calcined simultaneously.
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Following calcination, the reaction mixture is then carbo-chlorinated in the temperature range of 600C to 950C, using dry chlorine to which is added about 0.3% to 2.5%
by volume of boron chloride. The addltion o the solid carbon reductant after clay calclnation also gives good resultq, but the solid reducitlg agent then loses the benef-Lt o:E the additional calcination that removes water and other objectionable volatile matter.
The most salient feature of the present invention is the fact that carbo-chlorinating the clay in the pre-sence of limited amounts of reducing agent and limited amounts o~ boron chloride provides for the controlled and preferential chlorination of alumina over si.lica in kao-linitic ores such that good yields of alumLnum chloride are realized while simultaneously maintaining low yields of sillcon chloride, In the case o~ kaolin clay, the yield of aluminum chloride is in the order of 50-90%, while the yields of silicon chloride are generally 0~30%.
The low levels of silicon chloride produced by way of the present discovery results in reduced levels o~ re-ducing agent required for kaolin clay chlorination, For example, when carbon is used as the reducing agen~, only 5% or less carbon (based on weight of dry clay) is consumed in order to achieve a high yield of aluminum chlorîde in-stead of the 30-40% commonly consumed in the prior art when alumina and silica are chlorinated abou~ equally. This substantially reduced carbon consumptlon is further brought about by the fact th~ boron chloride catalyzed clay carbo-chlorination o the pxesent invention produ~es essentially ' . :
-C2 rather than C0. The permissible ~se of lower tempera-tures also results in energy savings.
The amount of silica to alumina that is chlori-nated can be unexpectedly controlled. The amount of boron chloride added to the chlorine can be increased above about
The present invention relates ~o the controlled production of aluminum ch`loride and silicon chlori~e in the carbo-chlorina~ion o~ kaolinitic ores. Kaolinitic ore S is de~ined as an ore containing a substantial proportion o~ kaolin. More specifically, the instant invention is primarily concerned with the rapid and preferential carbo-chlorination of al.umina over silica in the kaolinite in the ore, by controlling the levels of boron chloride and reductant yresent during the carbo-chlorination step.
Prior Art .
Thcre have been some references in the prior art to the carbo-chlorination of kaolinitic ores. A distinct characteristic disadvantage of the.se prior art techniques, however, is the act that silicon tetrachloride is normally produced at essentially the same rate and yield as aluminum chloride. This imposes a considerable economic burdell upon these processes for ~he following reasons: (a) carbon is consumed in the carbo-chlorination of the silica; (b) the silicon tetrachloride is very volatile so it ordinarily would be recovered by costly refrlgeration of ~he gases;
and ~c) the recovery of chlorine frorn the sili~on tetra~
chloride by oxldation with oxyg~n is an expensive step.
These prior art limitations have been recognized and are evident by the fact that there has been no con~ercially practiced process for producing aluminum chloride from kaolinitic ores such as clay.
There have been effor~s, however, to develop car-- - , .
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.
, . , ~ .. . .
. . :
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bo-chlorination processes wherein the chlorination of s:ilica is suppressed. See, for example, U.S. Patent Number l,866,731 and British Patent Mumber 305,578, which describe processes ~or the preferential carbo-chlorination of alwnina over silica in clay by recycling large amounts oE sllicon chloride with the chlorine which is taught as suppressing the Eormation oE additional sllicon chloride.
This prior art has apparently never been used commercially, pres~ably because it appears to be i.noperative according to actual laboratory tests and, even if workable, such pro-cesses would require heavy capital costs which must be borne for refrigeration and other equipment to cool the product gases to the very low temperatures necessary to condense out and thus separate and recycle the volatile silicon chloride.
The prior art further discloses, in various forms and fashions, the use of alkali metal compounds as cata lysts for the carbo-chlor-Lnation of aluminous ores, For example, in an article by Ya, E~ Seferovich, J, Chem. Ind.
(Moscow) l934, N, lO, 62-64, the use of alkali metal salts like sodium tetraborate is taught as catalyst during clay carbo-chlorination. This and the other prior art does not teach, however, the use of boron chlorlde gas or boron oxide a~ a catalyst for clay arbo-chlorina~ion, nor has it been recognized that the control of the ratio of alu-mina versu~ silica in carbo- hlorinat~on of clay is p~ssi-ble through con~rol o the amounts and ratio of the reduc-tant to boron chloride and th~ir synergistic action.
; ~ 3 .- - : , ., - . -:
A primary object of the present lnvention is to provide a carbo-chlorination process for the controlled chlorination of alumina over silica in kaolinitic ores to produce alumillum chloridc by substan~ially lncreaslng the ratio of alumlna chlorina~ion tv silica chlorination and whlle maintaining a rapid reaction rate and good percentage of conversion of alumina.
Secondarily, by adjusting the reaction conditions, the silica can be chlorinated in amounts from close to zero up to about equal to that of the chlorinatlon of the alu-mina.
The aluminum chlorlde can be subsequently electro-lyzed to aluminum metal; or used to make aluminum metal by the Toth Aluminum Process, or readily oxidized to aluminum oxide and thereafter converted to aluminum ~etal pursuant to the present well known Hall co~mercial process, or it can be sold as such for many other uses.
A further advantage o the present invention is that i~ allows recycling o~ the gaseous boron chloride carbo~chlorination catalyst by reacting it with clay and/
or reductant, or by dissolving i.t in solven~s like TiC14 followed by vaporization and collection of the B513 vapors.
A furthe* object is to permit the utiliza~ion of low grade bauxite or inexpensive and domestically available kaolinitic ore like clay for producin~ aluminum chloride in a manner which is quicker, less expensive, and does not rely upon imported ores as compared to the traditional Bayer process.
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Another ~dvantaye o.f this inven-tion is the energy savings from: (1) the unexpected important reduction in carbon cons~ ption throucJh the preponderant production of CO2 instead of CO; (2) in tlle satisfactory U9e 0.~ lower carbo-chlorination temperatLIre; (3) the reduction in carbo-chlorination o:E silica with attendant reduction in carbon cons~ption and refrigera-tion-condensation of SiCl~.
According to the present invention, then, there is provided a process for preferentially chlorinating alumina and suppressing the chlorination of silica in a kaolinitic ore consisting of the steps of: drying and oomminuting a kaolinitic ore to form a powdered ora; calcining the powdered ore at a temperature of from about 700 C to 900C to remove water of composition; and carbochlorinating the powdered ore at a temper-ature of ~rom about 600C to 950C to produce aluminum chloride by exposiny the calcined ore to a chlorinating agent in the presence of a carbonaceous reductant in an amo~mt of from abou-t 5% to 40% by weight of the dry ore and boron chloride in an ~nount of from about 0~3~ to 4.0% by volume of the chlorinating agent to preferentially chlorinate alumina and suppress chlorin-ation of silica~ ~
The controlled carbo-chlorin~tion of alumina and silica in kaolinitic ores is achieved by adjusting the levels of reductant between about 5% and 40% or more by weight of dry clay and the level o~ boron chloride between 0.3% to 5.0% by volume of the gaseous chlorinating agent which normally will be dry chlorine. The preferred embodi.ment of the instant invention involves the u~a of lower levels of boron chloride combined with lower levels of reductant such that the carbo-chlorination reac-t-ion is controlled to provide for the preferential chlorination of alumina over silica and simultaneously give a good yieldof chlorinated alumina.
A preferred process sequence utilizing kaolin clay is to initially clry and comminute the clay followed by cal-cination of the clay in the temperature range o~ about 700 C to 900C and in the p.resence of a properly prepared solid reducing agent, the reducing agent being present in an amount of from about 10% to 40~ of fixed carbon, based on the weight of the . dry ore. In this way, the solid reductant and the clay are calcined simultaneously.
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Following calcination, the reaction mixture is then carbo-chlorinated in the temperature range of 600C to 950C, using dry chlorine to which is added about 0.3% to 2.5%
by volume of boron chloride. The addltion o the solid carbon reductant after clay calclnation also gives good resultq, but the solid reducitlg agent then loses the benef-Lt o:E the additional calcination that removes water and other objectionable volatile matter.
The most salient feature of the present invention is the fact that carbo-chlorinating the clay in the pre-sence of limited amounts of reducing agent and limited amounts o~ boron chloride provides for the controlled and preferential chlorination of alumina over si.lica in kao-linitic ores such that good yields of alumLnum chloride are realized while simultaneously maintaining low yields of sillcon chloride, In the case o~ kaolin clay, the yield of aluminum chloride is in the order of 50-90%, while the yields of silicon chloride are generally 0~30%.
The low levels of silicon chloride produced by way of the present discovery results in reduced levels o~ re-ducing agent required for kaolin clay chlorination, For example, when carbon is used as the reducing agen~, only 5% or less carbon (based on weight of dry clay) is consumed in order to achieve a high yield of aluminum chlorîde in-stead of the 30-40% commonly consumed in the prior art when alumina and silica are chlorinated abou~ equally. This substantially reduced carbon consumptlon is further brought about by the fact th~ boron chloride catalyzed clay carbo-chlorination o the pxesent invention produ~es essentially ' . :
-C2 rather than C0. The permissible ~se of lower tempera-tures also results in energy savings.
The amount of silica to alumina that is chlori-nated can be unexpectedly controlled. The amount of boron chloride added to the chlorine can be increased above about
2,5% and the amount of fixed carbon i.n reducing agent can be increased above about 20% up to and above 40% until the silica and alumina are chlorinated in about equal amounts.
The boron chloride catalysis in clay carbo-chlo-rination permits the use of carbon monoxide as the sole reductant. Fur~hermore, this process can advantagcously use high ash coals and cokes, especially lignites, because the process recovers the alumina values in the ash. More-over, the process can be carried out at essentially atmos-pheric pressure which represents a preferred embodiment of the present invention. In general, pressures less than 50 psia are satisfactory.
To demonstrate the uniqueness of the present in-vention, t~e following working examples are presented using dry kaolin clay containing 37.8% A1203, 43,~ Si~2 1.5% Fe203, 1.8% TiO2, and 13,6~/~ bound H20 and wherein all parts are by weight unless otherwise specified. The re-actions were typically carried out in either shallow boats or in a fluid bed type of reactor in which khe rea tant gases were blown through a powder bed. For shallow boat reactions, the reactor consisted of a horizontal 25 mm O.D. fused quartz tub~ with external heating means into which was placed a shallow quartz boat containing about one gram of reaction mass. Fluid bed reactions were carried out in a 40 mm O.D. vertical quartz tube having , ~ ~J~
a quartz distributor plate and external heating means.
Typically, the fluid bed reactions were conducted using about: 20 to 40 grams of reaction mass. In both the shal-low boat and fluld bed reactions, the chlorination pro-ducts were collected in cooled condensers downstream ofthe chlorination reactors. The flow rate of chlorination gases into the reactors was about 250 cc/min. for shallow boats and for the ~luid bed reactors The following Table I gives the conditions and results of the examples according to the instant inven tion.
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r r' ~ U _ ,, ~ __ _ _ _ _ . _ ~_ _ _ _ _ _ __ N _ _ _ _ __ r.~ _ N N N r~ N t~l O N N N
~7 _._ r ~ r 1 O r 1 N O __ r~ r.1 Xr~ ~ I` O "0~ O N O r~
U ~1 ~ ~ _ __ N _ N _ ~ _ __ _ ~ h G ¦ N 1 Z ~ ~ ¦ ~ ;2S Z Z ~4 1 N~ 1 _ __ _ __ _ _ _ _ rl hl a z hl Z ~i X X ~; X Z Z
__ _ __ _ _ __ H¦ ~ ~ ~
~;1 _ _- _ _ _ . ~ ~ Pq ~ ~ ~ ~I~a _ __ _ _ ._. _ _ _ _ _ ____ __ _ _ _ ._ __ __ ~ 1~ ~IN ~ r~lN UIN ~ Nl ~IO ~IN ~!IN ~;!IN
: _ ~ ___ _ ~ _ ~O ~ ~ ~ ~ p,10, ~ ~ z ~1~0 ~ z z~
f l i~ ~OD N ~ ~ N æ r~l r~ N U~
'" ~3 __ _ __ _ f!- 0~ O O ¦ o CA U; r~ O
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- , , Examples 1 5 Reference is made to I'able I and specifically to examples 1-5, which were all carried out in shallow boats.
Dried kaolinitic clay in the amount of about 1.2 grams was calcined in the temperature range of 700C to 900C for 20 to 45 minutes under a p-~rge of argon (Ar) or C02 The clay was mixed with petroleum coke (PC) or sub-bitumino~s char (SBC) in an amount of from 10% to 100% by weight o~
fixed carbon (dry clay basis) either before calcination or after calcination, but before carbo chlorination. The re-sulting clay-carbon mixtures were all carbo-chlorinated at 700C for 30 minutes under 250 cc/mln~ flow rate of chlo-rine and from 0 to 10 cc/min. flow rate of boron trichlo-ride ga~.
It has been determined through statistlcally de-signed screening tests that the only ma~or effects of variables of those shown in Table I in examples 1-5 are those due to le~rel of carbon and level of BC13 added to the reaction and the ratios thereof, Therefore, the other variables, as listed in the tables, would not signiflcantly affect the results repor-ted in columns 17 an~ 18. It is thus the purpose of examples 1-5 to illustrate thc singu-lar and conjoint effects of carbon and BC13 levels upon the chlorination conversion o al~mina and ~illca in clay.
Example 1 is presentcd as-being illustrative of a typical prior art reaction mix~ure containing no BC13 and 20%
; fixed carbon by weight o clay ~stoichiometrlc for essen-tially tota]. conversion of A1203 and SiO2 to form C02).
As can ~e seen, the reaction resulted in only 17.0% Al203 : , . -. .
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: . ' and 13.7% SiO2 conversions. By comparison in examples 2 and 3, the carbon level was decreased to 10% and, upon the introduction of BCl3 ~o ~he chlorination reaction, the level o~ Al203 conversion increased markedly and th~ level of S102 conversion decreased below the det~ctable level, Surprisingly, however, in examples 4 and 5, wherein the carbon level was increased to lOOa/o by weight, the lntroduc-tion of BC13 increased the chlorination conversion of b~h Al203 and SiO2, such that at high levels of BC13 essen-tially total clay chlorination is obtained. Thus, based on the data presented in examples 1-5, it is obvious that BCl3 has a cataly~ic effec~ on clay carbo-chlorination and that, through proper control of the levels oE BCl3 and carbon added to the reaction, it is possible through un-expected con~oint action to provide for either highly seleo-tive chlorination of A1203 over SiO2 or for the total chlo-rination of both A1203 and SiO2, It is ~urther noteworthy to point out that in examples 4-5 the carbon oxide rea~tion products contained 80-100% C02 and 20-0% C0.
Examples 6 and 7 Example 6 illustrates the process of the present invention to achieve selective chlorination o A1~03 over SiO2 in clay using a fluid bed type reactor and carbon mon-~ oxide as the reducing agent. As ean be seen in Table I, :~ ~ 25 chlorine at 250 cc/min., carbon monoxide at 250 cc/min., and BC13 at 5 ec/min. were mixed and reacted wi~h calcined clay at 900C for 25 minutes, resulting in 6~.1% A1203 and 4.g% SiO2 conversions . Similarly, example 7 was carried Jl . .
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out in a fluid bed reactor, however, using petroleum coke as solid reduc~ant added to the calcination step and re-sulting in 65.0% A1203 and 1!~,7% SiO2 conversions. Exam-ples 6 and 7 further illustra~e the controlled clay carbo-chlorination obtained through use of moderate levels of reducing agent and BC13 in the process of the present in-vention.
E mele Lignite coal contailing about 48% fixed carbon was mixed together with dry clay and a binder to provide 10%
fixed carbon by weight of the dry clay. The resulting bound mixture was calcined at 750C for 30 minutes in a shallow boat and therea~ter was carbo-chlorinated at 625C
for 45 minutes, using a 250 cc/min. flow of chlorlne and BC13 at 5 cc/min. The carbo-chlorination reaction resulted in 72,1% A1203 and 12,0% SiO2 conversions and illustrat.es the combined calcination of clay and coal and the utiliza-tion of low reaction temperatures.
Examples 9 and 10 In practicing the process of the p~esent invention, ~` it ma~ be necessary or desirable to recycle at least part of the BC13 reactlon cat lyst in some form other than BC13.
For example, an oxidatîon or scrubbing step may be uqed to treat some of the carbo-chlorination reaction off gases containing BC13, theréby producing either boron oxide or boric acid, which would be recycled to the calcination or carbo-chlorination ~-tep. Example 9 illustrat~s the case in .
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which boric acid is added to the clay before calcination, and example 10 illustrates ~he case in which boron oxide is added to the clay a~ter calcination but before carbo-chlorination, As can be seen from the results summarized in Table I, either me~hod of recycling wherein BC13 is produced in sltu during carbo-chlorination of the clay glves controlled chlorination of alllmina and silica in ~he clay.
Examples 11-15 (See Table II) In addition to the possible necessity of recy-cling BC13 in the form of an oxida~ion or scrub product, it may also be necessary to provide BC13 make-up for that BC13 that is lost during processing. The BC13 could be produced by chlorinating any suitable boron containing com-polmd and thereafter the BC13 could be added to the clay carbo chlorination reaction as needed for make-up, Alter-natively, the BC13 make-up could be produced in situ by adding small amounts of boron compounds to the clay ~o be carbo-chlorinated, In examples 11-15, small amounts of the boron compounds listed in Table II were added to clay to provide the equivalent o 2,5~/o B203 by weight o~ dry clay, The clay-boron compound mix~ures were prep~red, :~ calcined, and carbo-chlorinated in a manner similar to that given for example 9, and the ehlorination results are sum-marized in Table II.
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~ABLE II
% Conversion Example No. Boron Compound A123 Si2 11 Borax 64.8 33.5 12 Boron Sulfide 72.7 29.6 13 Boron Phosphate 64.1 7.9 14 Calcium Borate 61.9 39.9 Ammonium Borate 52.2 8.8 ~ 8 can be seen from the above results, the addi-tion of a boron compound to the clay carbo-chlorination reaction i9 a viable method for generating BC13 in situ and - thus providing for the controlled chlorination of alumina and silica in clay. However, these compounds have the dis-advantage of consuming chlorine by reaction with the other elements of the compounds.
Example 16 Dried clay was calcined in a fluid bed reactor under an air purge at 700C and was subsequently ground to -75:~m~45:ilm particle size. Calcined petroleum coke of the same particle size was ground together with the clay and the resulting mixture was carbo-chlorina~ed in a ~hallow boat at 700C for 160 minu~es under a 1OW of 2S0 c /min.
.
chlorine and 5 cc/min. BC13~. Upon analysis, i~ wa~ found that ~1%~ 03 and 35% SiO2~had been ch1 orinated and that, of the lG~L by weight of fixed carbon added to the reaction, only ~.1% was consumed.
The present process offers as a distinguishing featu~e the utilization of relatively short reaction times ~ ,., . . . . . .
' - - ' ' ' - . , . . . ;~ ---when viewed in perspective of the prior art of chlorination reactions involving similar ores. In the presence of boron chloride, the benefit of such short reaction times, coupled with the control of and the important reduction in amount of silicon chloride produced hereby and the high efElciency of carbon utilization, renders ~he pre~ent novel process espe-cialLy ~ttrac.tive commercially for the productlon of alumi-num chloride and subsequently alumina and aluminum from ordinary kaolin clay.
In addi~ion to alumina and silica, other compo-nents in clay are also carbo-chlorinated to produce valua-ble chloride by-products. Specifically, the titania values in clay are chlorinated essentially to completion to pro-duce TiC14. As was shown in the examples, the chlorinationof silica can be maintained at essentially zero, ~owever, at the expense of lower alumina convèrsions of 50% to 65%.
The titania reacted at these alumina conversions is still essentially 100% and thus compensates for any increased materials and handling costs due ko the lower alumina pro-duction .
The instant invention permits more economicalutilization of previously unusuable inexpensive and abun dant dome~tic ores, such as kaolin clay and low grade bauxites-containing kaolin clay, whereas the present Bayer alumina process requires very 610w (2-3 days~ precipitation of alumina in huge tank farms, resulting in large volume~
of waste "red mud". All of these disadvantages are over-come by the instant invention for producing aluminum chlo-ride, which can simply and economically be oxidized to form .~
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, alumina. Moreover, by using ~aolinitic orPs, the titanium value can be recovered along with the aluminum value, there-by reeing two ma~or industries from their traditional de-pendence on imported ores.
The hardware to perform the instant invention can be batch, semicontinuous or continuous processing apparatus, such as rotary kilns and reactors; fluid, static or moving bed reactors, or horizontal conveyors.
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The boron chloride catalysis in clay carbo-chlo-rination permits the use of carbon monoxide as the sole reductant. Fur~hermore, this process can advantagcously use high ash coals and cokes, especially lignites, because the process recovers the alumina values in the ash. More-over, the process can be carried out at essentially atmos-pheric pressure which represents a preferred embodiment of the present invention. In general, pressures less than 50 psia are satisfactory.
To demonstrate the uniqueness of the present in-vention, t~e following working examples are presented using dry kaolin clay containing 37.8% A1203, 43,~ Si~2 1.5% Fe203, 1.8% TiO2, and 13,6~/~ bound H20 and wherein all parts are by weight unless otherwise specified. The re-actions were typically carried out in either shallow boats or in a fluid bed type of reactor in which khe rea tant gases were blown through a powder bed. For shallow boat reactions, the reactor consisted of a horizontal 25 mm O.D. fused quartz tub~ with external heating means into which was placed a shallow quartz boat containing about one gram of reaction mass. Fluid bed reactions were carried out in a 40 mm O.D. vertical quartz tube having , ~ ~J~
a quartz distributor plate and external heating means.
Typically, the fluid bed reactions were conducted using about: 20 to 40 grams of reaction mass. In both the shal-low boat and fluld bed reactions, the chlorination pro-ducts were collected in cooled condensers downstream ofthe chlorination reactors. The flow rate of chlorination gases into the reactors was about 250 cc/min. for shallow boats and for the ~luid bed reactors The following Table I gives the conditions and results of the examples according to the instant inven tion.
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::
.
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r~ ---r~ H r/ ~1 O O r rJ~ r J ¦ N r i I r~l r~ U N O _ r l r1 __ ,~ O ,1 __ ___ _ _ O O ~ O O O N N O O
r r' ~ U _ ,, ~ __ _ _ _ _ . _ ~_ _ _ _ _ _ __ N _ _ _ _ __ r.~ _ N N N r~ N t~l O N N N
~7 _._ r ~ r 1 O r 1 N O __ r~ r.1 Xr~ ~ I` O "0~ O N O r~
U ~1 ~ ~ _ __ N _ N _ ~ _ __ _ ~ h G ¦ N 1 Z ~ ~ ¦ ~ ;2S Z Z ~4 1 N~ 1 _ __ _ __ _ _ _ _ rl hl a z hl Z ~i X X ~; X Z Z
__ _ __ _ _ __ H¦ ~ ~ ~
~;1 _ _- _ _ _ . ~ ~ Pq ~ ~ ~ ~I~a _ __ _ _ ._. _ _ _ _ _ ____ __ _ _ _ ._ __ __ ~ 1~ ~IN ~ r~lN UIN ~ Nl ~IO ~IN ~!IN ~;!IN
: _ ~ ___ _ ~ _ ~O ~ ~ ~ ~ p,10, ~ ~ z ~1~0 ~ z z~
f l i~ ~OD N ~ ~ N æ r~l r~ N U~
'" ~3 __ _ __ _ f!- 0~ O O ¦ o CA U; r~ O
, ~ __ _ . ~ ~ ~ _ _ : ~ ~ ~ ~; z; ~ z ~ ~z z~ ~ ~: ~ ~z;
~, _ _ . _ _ _ N ~ ~ ~ ~ nl : ' : _ :
~ ~:~ ~ ~ td la :~ ~ ~3~ ~ " ~
: , . . ___-- : _ _ _ b ~ 1 N _ _ _ _ __ CO _ O
- , , Examples 1 5 Reference is made to I'able I and specifically to examples 1-5, which were all carried out in shallow boats.
Dried kaolinitic clay in the amount of about 1.2 grams was calcined in the temperature range of 700C to 900C for 20 to 45 minutes under a p-~rge of argon (Ar) or C02 The clay was mixed with petroleum coke (PC) or sub-bitumino~s char (SBC) in an amount of from 10% to 100% by weight o~
fixed carbon (dry clay basis) either before calcination or after calcination, but before carbo chlorination. The re-sulting clay-carbon mixtures were all carbo-chlorinated at 700C for 30 minutes under 250 cc/mln~ flow rate of chlo-rine and from 0 to 10 cc/min. flow rate of boron trichlo-ride ga~.
It has been determined through statistlcally de-signed screening tests that the only ma~or effects of variables of those shown in Table I in examples 1-5 are those due to le~rel of carbon and level of BC13 added to the reaction and the ratios thereof, Therefore, the other variables, as listed in the tables, would not signiflcantly affect the results repor-ted in columns 17 an~ 18. It is thus the purpose of examples 1-5 to illustrate thc singu-lar and conjoint effects of carbon and BC13 levels upon the chlorination conversion o al~mina and ~illca in clay.
Example 1 is presentcd as-being illustrative of a typical prior art reaction mix~ure containing no BC13 and 20%
; fixed carbon by weight o clay ~stoichiometrlc for essen-tially tota]. conversion of A1203 and SiO2 to form C02).
As can ~e seen, the reaction resulted in only 17.0% Al203 : , . -. .
- . . . . . . . .
, . .. ,: ..,:;~ ,- : : ; ~ -,~, ~ , , .. ~. , .
.
: . ' and 13.7% SiO2 conversions. By comparison in examples 2 and 3, the carbon level was decreased to 10% and, upon the introduction of BCl3 ~o ~he chlorination reaction, the level o~ Al203 conversion increased markedly and th~ level of S102 conversion decreased below the det~ctable level, Surprisingly, however, in examples 4 and 5, wherein the carbon level was increased to lOOa/o by weight, the lntroduc-tion of BC13 increased the chlorination conversion of b~h Al203 and SiO2, such that at high levels of BC13 essen-tially total clay chlorination is obtained. Thus, based on the data presented in examples 1-5, it is obvious that BCl3 has a cataly~ic effec~ on clay carbo-chlorination and that, through proper control of the levels oE BCl3 and carbon added to the reaction, it is possible through un-expected con~oint action to provide for either highly seleo-tive chlorination of A1203 over SiO2 or for the total chlo-rination of both A1203 and SiO2, It is ~urther noteworthy to point out that in examples 4-5 the carbon oxide rea~tion products contained 80-100% C02 and 20-0% C0.
Examples 6 and 7 Example 6 illustrates the process of the present invention to achieve selective chlorination o A1~03 over SiO2 in clay using a fluid bed type reactor and carbon mon-~ oxide as the reducing agent. As ean be seen in Table I, :~ ~ 25 chlorine at 250 cc/min., carbon monoxide at 250 cc/min., and BC13 at 5 ec/min. were mixed and reacted wi~h calcined clay at 900C for 25 minutes, resulting in 6~.1% A1203 and 4.g% SiO2 conversions . Similarly, example 7 was carried Jl . .
~ ; ' ' ': ' ' .
out in a fluid bed reactor, however, using petroleum coke as solid reduc~ant added to the calcination step and re-sulting in 65.0% A1203 and 1!~,7% SiO2 conversions. Exam-ples 6 and 7 further illustra~e the controlled clay carbo-chlorination obtained through use of moderate levels of reducing agent and BC13 in the process of the present in-vention.
E mele Lignite coal contailing about 48% fixed carbon was mixed together with dry clay and a binder to provide 10%
fixed carbon by weight of the dry clay. The resulting bound mixture was calcined at 750C for 30 minutes in a shallow boat and therea~ter was carbo-chlorinated at 625C
for 45 minutes, using a 250 cc/min. flow of chlorlne and BC13 at 5 cc/min. The carbo-chlorination reaction resulted in 72,1% A1203 and 12,0% SiO2 conversions and illustrat.es the combined calcination of clay and coal and the utiliza-tion of low reaction temperatures.
Examples 9 and 10 In practicing the process of the p~esent invention, ~` it ma~ be necessary or desirable to recycle at least part of the BC13 reactlon cat lyst in some form other than BC13.
For example, an oxidatîon or scrubbing step may be uqed to treat some of the carbo-chlorination reaction off gases containing BC13, theréby producing either boron oxide or boric acid, which would be recycled to the calcination or carbo-chlorination ~-tep. Example 9 illustrat~s the case in .
>,; j .: ' . . ' . : : `
....
.
which boric acid is added to the clay before calcination, and example 10 illustrates ~he case in which boron oxide is added to the clay a~ter calcination but before carbo-chlorination, As can be seen from the results summarized in Table I, either me~hod of recycling wherein BC13 is produced in sltu during carbo-chlorination of the clay glves controlled chlorination of alllmina and silica in ~he clay.
Examples 11-15 (See Table II) In addition to the possible necessity of recy-cling BC13 in the form of an oxida~ion or scrub product, it may also be necessary to provide BC13 make-up for that BC13 that is lost during processing. The BC13 could be produced by chlorinating any suitable boron containing com-polmd and thereafter the BC13 could be added to the clay carbo chlorination reaction as needed for make-up, Alter-natively, the BC13 make-up could be produced in situ by adding small amounts of boron compounds to the clay ~o be carbo-chlorinated, In examples 11-15, small amounts of the boron compounds listed in Table II were added to clay to provide the equivalent o 2,5~/o B203 by weight o~ dry clay, The clay-boron compound mix~ures were prep~red, :~ calcined, and carbo-chlorinated in a manner similar to that given for example 9, and the ehlorination results are sum-marized in Table II.
.. ~ 13 .
- ~ .
`~ .
.~ 5~3~
~ABLE II
% Conversion Example No. Boron Compound A123 Si2 11 Borax 64.8 33.5 12 Boron Sulfide 72.7 29.6 13 Boron Phosphate 64.1 7.9 14 Calcium Borate 61.9 39.9 Ammonium Borate 52.2 8.8 ~ 8 can be seen from the above results, the addi-tion of a boron compound to the clay carbo-chlorination reaction i9 a viable method for generating BC13 in situ and - thus providing for the controlled chlorination of alumina and silica in clay. However, these compounds have the dis-advantage of consuming chlorine by reaction with the other elements of the compounds.
Example 16 Dried clay was calcined in a fluid bed reactor under an air purge at 700C and was subsequently ground to -75:~m~45:ilm particle size. Calcined petroleum coke of the same particle size was ground together with the clay and the resulting mixture was carbo-chlorina~ed in a ~hallow boat at 700C for 160 minu~es under a 1OW of 2S0 c /min.
.
chlorine and 5 cc/min. BC13~. Upon analysis, i~ wa~ found that ~1%~ 03 and 35% SiO2~had been ch1 orinated and that, of the lG~L by weight of fixed carbon added to the reaction, only ~.1% was consumed.
The present process offers as a distinguishing featu~e the utilization of relatively short reaction times ~ ,., . . . . . .
' - - ' ' ' - . , . . . ;~ ---when viewed in perspective of the prior art of chlorination reactions involving similar ores. In the presence of boron chloride, the benefit of such short reaction times, coupled with the control of and the important reduction in amount of silicon chloride produced hereby and the high efElciency of carbon utilization, renders ~he pre~ent novel process espe-cialLy ~ttrac.tive commercially for the productlon of alumi-num chloride and subsequently alumina and aluminum from ordinary kaolin clay.
In addi~ion to alumina and silica, other compo-nents in clay are also carbo-chlorinated to produce valua-ble chloride by-products. Specifically, the titania values in clay are chlorinated essentially to completion to pro-duce TiC14. As was shown in the examples, the chlorinationof silica can be maintained at essentially zero, ~owever, at the expense of lower alumina convèrsions of 50% to 65%.
The titania reacted at these alumina conversions is still essentially 100% and thus compensates for any increased materials and handling costs due ko the lower alumina pro-duction .
The instant invention permits more economicalutilization of previously unusuable inexpensive and abun dant dome~tic ores, such as kaolin clay and low grade bauxites-containing kaolin clay, whereas the present Bayer alumina process requires very 610w (2-3 days~ precipitation of alumina in huge tank farms, resulting in large volume~
of waste "red mud". All of these disadvantages are over-come by the instant invention for producing aluminum chlo-ride, which can simply and economically be oxidized to form .~
..
. ' ' .
, alumina. Moreover, by using ~aolinitic orPs, the titanium value can be recovered along with the aluminum value, there-by reeing two ma~or industries from their traditional de-pendence on imported ores.
The hardware to perform the instant invention can be batch, semicontinuous or continuous processing apparatus, such as rotary kilns and reactors; fluid, static or moving bed reactors, or horizontal conveyors.
.
t~
' .
.~ ~
Claims (8)
1. A process for preferentially chlorinating alumina and suppressing the chlorination of silica in a kaolinitic ore consisting of the steps of:
drying and comminuting a kaolinitic ore to form a powdered ore;
calcining the powdered ore at a temperature of from about 700 C to 900°C to remove water of composition; and carbochlorinating the powdered ore at a temperature of from about 600°C to 950°C to produce aluminum chloride by exposing the calcined ore to a chlorinating agent in the pres-ence of a carbonaceous reductant in an amount of from about 5%
to 40% by weight of the dry ore and boron chloride in an amount of from about 0.3% to 4.0% by volume of the chlorinating agent to preferentially chlorinate alumina and suppress chlorination of silica.
drying and comminuting a kaolinitic ore to form a powdered ore;
calcining the powdered ore at a temperature of from about 700 C to 900°C to remove water of composition; and carbochlorinating the powdered ore at a temperature of from about 600°C to 950°C to produce aluminum chloride by exposing the calcined ore to a chlorinating agent in the pres-ence of a carbonaceous reductant in an amount of from about 5%
to 40% by weight of the dry ore and boron chloride in an amount of from about 0.3% to 4.0% by volume of the chlorinating agent to preferentially chlorinate alumina and suppress chlorination of silica.
2. The process of claim 1, wherein the chlorinating agent is dry chlorine.
3. The process of claim 1, wherein the carbonaceous reductant is selected from the group consisting of petroleum coke, coal coke and lignite char.
4. The process of claim 1, wherein the carbonaceous reducing agent is added to the ore, and the ore and carbonaceous reductant are calcined simultaneously.
5. The process of claim 1, wherein the carbonaceous reductant is carbon monoxide.
6. The process of claim 1, wherein the boron chloride is procluced in situ by carbo-chlorination of a boron containing compound selected from the group consistiny of boron oxide and boric acid added to the ore.
7. The process of claim 1, wherein the amount of the carbonaceous reductant is from about 5% to 20% by weight of the dry one.
8. The process of claim 1 wherein the boron chloride is produced in situ by carbo-chlorination of a boron containing compound selected from the group consisting of boron sulfide, boron phosphate, calcium borate and ammonium borate added to the ore.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA300,834A CA1105712A (en) | 1978-04-10 | 1978-04-10 | Controlled carbo-chlorination of kaolinitic ores |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA300,834A CA1105712A (en) | 1978-04-10 | 1978-04-10 | Controlled carbo-chlorination of kaolinitic ores |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1105712A true CA1105712A (en) | 1981-07-28 |
Family
ID=4111197
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA300,834A Expired CA1105712A (en) | 1978-04-10 | 1978-04-10 | Controlled carbo-chlorination of kaolinitic ores |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1105712A (en) |
-
1978
- 1978-04-10 CA CA300,834A patent/CA1105712A/en not_active Expired
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