DESC:

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patent Rules, 200 3
COMPLETE SPECIFICATION
[See Section 10 and Rule 13]

1. TITLE OF THE INVENTION

ENVIRONMENT FRIENDLY PROCESS FOR MAKING HIGH-PURITY ALUMINA

2. APPLICANTS

(a) SARASWATI PIGMENTS PVT. LIMITED
(b) an Indian company,
(c) of Plot No. L/1216/3, Phase IV – G.I.D.C., Naroda, Ahmedabad, 382330, Gujarat, INDIA,

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in
which it is to be performed.

FIELD OF THE INVENTION

The present invention relates to a process for manufacturing of aluminium oxide or alumina. More particularly, the present invention relates to an improved environment-friendly process for manufacturing of high-purity aluminium oxide or alumina from aluminium hydroxide recovered from waste containing aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt etc. from the waste effluents of chemical industries.

In particularly, the present invention relates to a process for manufacturing of alumina from aluminium hydroxide recovered from waste containing aluminium chloride from the waste effluent of chemical industries.

BACKGROUND OF THE INVENTION

Aluminium oxide commonly referred to as alumina, is industrially significant as it is extensively utilized in the production of aluminium metal, as an abrasive due to its hardness, and as a refractory material due to its high melting point.

Alumina is one of the most cost effective and widely used material in the field of engineering ceramics. The raw materials from which this high performance technical grade ceramic is made being readily available and reasonably priced. This results in good value for the cost in fabricated alumina shapes. With an excellent combination of properties and an attractive price, it is no surprise that fine grain technical grade alumina has a very wide range of applications.

Alumina possesses strong ionic interatomic bonding giving rise to the typical characteristics. It can exist in several crystalline phases which all revert to the most stable hexagonal alpha phase at elevated temperatures. The phase of alpha phase alumina is the strongest and stiffest of the oxide ceramics. The high hardness, excellent dielectric properties, refractoriness and good thermal properties make alumina the material of choice for a wide range of applications.

High purity alumina is usable in both oxidizing and reducing atmospheres over a temperature of 1925°C. Weight loss in vacuum ranges from 10–7 to 10–6 g/cm2.sec over a temperature range of 1700° to 2000°C. It resists attack by all gases except wet fluorine and is resistant to all common reagents except hydrofluoric acid and phosphoric acid. Elevated temperature attack occurs in the presence of alkali metal vapors particularly at lower purity levels.

The composition of the ceramic body can be changed to enhance particular desirable material characteristics. An example would be additions of chrome oxide or manganese oxide to improve hardness and change color. Other additions can be made to improve the ease and consistency of metal films fired to the ceramic for subsequent brazed and soldered assembly.

Over 90% of the aluminium oxide, normally termed Smelter Grade Alumina (SGA), produced is consumed for the production of aluminium, usually by the Hall–Héroult process. The remainder, normally called specialty alumina is used in a wide variety of applications which reflect its inertness, temperature resistance and electrical resistance.

Being fairly chemically inert and white, alumina is a favored filler for plastics. Aluminium oxide is a common ingredient in sunscreen and is sometimes present in cosmetics such as blush, lipstick, and nail polish. Many formulations of glass have aluminium oxide as an ingredient.

Aluminium oxide catalyzes a variety of reactions that is industrially useful. In its largest scale application, aluminium oxide is the catalyst in the Claus process for converting hydrogen sulfide waste gases into elemental sulfur in refineries. It is also useful for dehydration of alcohols to alkenes.

Aluminium oxide serves as a catalyst support for many industrial catalysts, such as those used in hydrodesulphurization and some Ziegler-Natta polymerizations.

Aluminium oxide is widely is also used to remove water from gas streams.

Aluminium oxide is also used for its hardness and strength. It is widely used as an abrasive, including as a much less expensive substitute for industrial diamond. Many types of sandpaper use aluminium oxide crystals. In addition, its low heat retention and low specific heat make it widely used in grinding operations, particularly cutoff tools. As the powdery abrasive mineral aloxite, it is a major component, along with silica, of the cue tip "chalk" used in billiards. Aluminium oxide powder is also used in some CD/DVD polishing and scratch-repair kits. Its polishing qualities are also behind its use in toothpaste.

Aluminium oxide flakes are used in paint for reflective decorative effects, such as in the automotive or cosmetic industries.

Aluminium oxide has been used in a few experimental and commercial fiber materials for high-performance applications (e.g., Fiber FP, Nextel 610, Nextel 720). Alumina nanofibers in particular have become a research field of interest.

The high purity aluminum oxide or alumina powder can be used to make; translucent tubes for high-pressure sodium lamps, sapphires for watch covers, high-strength ceramic tools, abrasives for magnetic tape, manufacturing light emitting diodes as a substrate for GaN, silicon microchip wafers for optic- electronics, windows and cowls for aircrafts, protective windows for car headlamps, cell phones and other electronic devices, stop signals, surgery scalpels, micro-optical elements of medical fiber-optic probes, optical scanners for bar codes, ultraviolet CD and DVD optical systems, prisms, lenses, optical plates, optical systems of visual and IR diapasons, cell phone, mobile devices and fiber-optic system display windows, equipment for chemical manufacturing in aggressive and high-temperature environments: tubes, crucibles, funnels, chemical glassware, abrasives, battery components, bearings and jewelry stones etc.

Currently, the Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide). Bauxite, the most important ore of aluminium, contains only 30–54% aluminium oxide, (alumina). The rest being a mixture of silica, various iron oxides, and titanium dioxide. The aluminium oxide must be purified before it can be refined to aluminium metal.

In the Bayer process, except for SiO2, the other components of bauxite do not dissolve in base. Upon filtering the basic mixture, Fe2O3 is removed. When the Bayer liquor is cooled, Al(OH)3 precipitates, leaving the silicates in solution.

NaAl(OH)4 ? NaOH + Al(OH)3

The solid Al(OH)3 Gibbsite is then calcined (heated to over 1100°C) to give aluminium oxide:

2?Al(OH)3 ? Al2O3 + 3?H2O

Using aluminum as the starting raw material for manufacturing high purity aluminum oxide is very difficult due to the fact that it is difficult to control the reaction rate of the acid with the aluminum.

Many chemical industries are the manufacturer of copper phthalocyanine green and blue (hereinafter referred to as CPC Green and CPC Blue). The raw materials for CPC Green Plant are aluminium chloride, cupric chloride, crude CPC Blue, chlorine, caustic soda. During the course of manufacture of CPC green, mother liquor emerges. This mother liquor of the CPC Green mainly contains aluminium chloride, copper etc. and is treated with sodium sulphide or zinc metal or aluminium metal or iron metal to get copper as copper sulphide or as copper metal. The resultant clear mother liquor which is free from copper and other impurities are neutralized with Soda Ash solution to get aluminium hydroxide slurry. This slurry is filtered, washed and to get aluminium hydroxide wet cake.

At present, there is no existing environment friendly method by which one can utilize the aluminium hydroxide as recovered in CPC green manufacturing, to produce high purity alumina.

Thus, there is a constant need for a low-cost and environment friendly process, which uses less energy, to make high purity alumina.

SUMMARY AND OBJECTS OF THE INVENTION

A process for the preparation of high-purity aluminium oxide (AL2O3) from the waste containing aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt is provided. The said process comprises the preparation of an aqueous slurry which comprises 2 to 25 wt. % of aluminium hydroxide, wherein the said aluminium hydroxide is recovered from hydrolyzing the waste containing aluminium chloride, aluminium sulfate, aluminium carbide, sodium aluminate or any other aluminium salt with soda ash. The aqueous slurry so obtained is subjected to hydrothermal treatment at a temperature in the range of 200°C to 1250° C, not being limited to, for at least 4 hours. The reaction mixture containing the dry powder of aluminium oxide is obtained by centrifugation or filter pressing or any other conventional means and methods. The product i.e. high-purity aluminium oxide is finally obtained by drying the reaction mixture by spin flash drying or any other conventional methods.

The production process of alumina of the invention is based on green engineering of waste effluents of the chemical industries. The produced alumina according to the process of the invention has a purity of 98% to 99.50%.

The raw material produced by the method of the present invention have a wide application range and has the advantages of environment-friendly waste recycling and reducing waste generation.

One of the objects of the invention is to provide an improved process for manufacturing of high-purity aluminium oxide or alumina from the waste effluent of chemical industries for example - all kinds of raney nickel waste water, fridle craft reactions including acyalation, fries rearrangements, chlorination of copper phthalocayine etc.

The process of the invention enables various metals, particularly aluminium, and various alloys to be produced in high purity.

Another object of the invention is to provide an improved environment-friendly process for manufacturing of high-purity aluminium oxide or alumina from aluminium hydroxide recovered from waste containing aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt etc. from the waste effluents of chemical industries.

Another object of the invention is to provide an improved process for manufacturing of alumina from aluminium hydroxide recovered from waste containing aluminium chloride from the waste effluent of chemical industries.

Another object of the invention is to provide an improved environment-friendly process for manufacturing of high-purity aluminium oxide or alumina which is cost-effective and free from water pollution.

Another object of the invention is to provide a process for manufacturing of aluminium oxide wherein the process eliminates costly treatment of mother liquor produced during process of CPC green production reducing substantially the cost of the manufacturing process.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates an IR pattern of aluminium oxide prepared according to Example 1 with standard aluminium oxide.

DETAILED DESCRIPTION OF THE INVENTION

Before the present invention is described, it is to be understood that this invention is not limited to particular methodologies and materials described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention.
Before the present invention is described, it is to be understood that unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it is to be understood that the present invention is not limited to the methodologies and materials; since similar or equivalent to those described herein can be used in the practice or testing of the present invention.

The preferred methods and materials are described herein and these may vary within the specification indicated. Unless stated to the contrary, any use of the words such as "including," "containing," "comprising," "having" and the like, means "including without limitation" and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it. Embodiments of the invention are not mutually exclusive, but may be implemented in other combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limiting of the scope of invention. Further the terms disclosed in the embodiments are merely exemplary methods of the invention, which may be embodied in various forms.

It is also understood that the terms "a", "an", "the" and the like are words for the sake of convenience and are not to be construed as limiting terms. Moreover, it will be understood that the illustrations are for the purpose of describing a particular exemplary embodiment of the invention and are not limited to the invention thereto.

The process of the invention is essentially based on the production of high-purity alumina by using mother liquor generated during the manufacturing of Copper Phthalocyanine (CPC) pigments namely CPC Green. However, it is possible to recover aluminium oxide and copper metal from any industrial waste which contains aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt in it, irrespective of source of waste. Thus, the scope of the invention intends to cover the recovery of aluminium oxide and copper metal from any waste which contains aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt in it but free from other impurities by the process of the present invention.

To describe the process at the very beginning, the process of the invention comprises the steps of separating the mother liquor generated during the manufacturing of Copper Phthalocyanine (CPC) pigments namely CPC Green. This mother liquor of the CPC Green mainly contains aluminium chloride, copper etc. and is treated with sodium sulphide or zinc or aluminium or iron to get copper as copper sulphide, or copper metal which is separated out. The resultant clear mother liquor, which is free from copper and other impurities, is neutralized with soda ash solution to get aluminium hydroxide slurry. This slurry is filtered and washed to get wet aluminium hydroxide. The wet aluminium hydroxide, thus, obtained is used for the production of high-purity alumina.

According to one of the embodiments of the invention, there is provided a process for the preparation of high-purity aluminium oxide from the waste containing aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt, said process comprising the steps of:

a. preparing 2 to 25 wt. % of aqueous slurry of aluminium hydroxide, said aluminium hydroxide is recovered from the waste containing aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt by hydrolyzing the waste with soda ash;
b. subjecting the wet aluminium hydroxide obtained in step (a) to carbonization or hydrothermal treatment at a temperature in the range of about 900°C to 1250° C for at least 4 hours; and
c. collecting the dry powder of aluminium oxide obtained in step (b) either by centrifuging or filter pressing the reaction mixture or any other conventional means and methods followed by drying the reaction mixture by spin flash drying or any other conventional methods.

In accordance with a preferred embodiment of the invention, the step (a) of recovering aluminium hydroxide from the waste of mother liquor includes aluminium chloride which is hydrolyzed with soda ash followed by filtering the hydrolyzed product to obtain wet aluminium hydroxide.

In accordance with a preferred embodiment of the invention, the step (b) of carbonization or hydrothermal treatment at temperature is in the range of, not limited to, 900°C to 1250° C for at least 4 hours.

In accordance with a preferred embodiment of the invention, the waste used in the process is a mother liquor of CPC Green containing aluminium chloride.

The above-discussed process for manufacturing of alumina is very cost-effective as the starting material used i.e. aluminium hydroxide, is recovered from mother liquor of CPC Green or any other waste/liquor containing aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt.

Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified. Thus, these examples are provided for illustrative purposes only and not to be construed as limitations on scope of the process of this invention.

EXAMPLE I

Preparation of aluminium hydroxide and aluminium oxide:

1000 gm of mother liquor containing 36.28 gm aluminium and 3.9 gm copper is treated with 8.0 g of aluminium metal. The precipitated copper as copper metal was removed by filtration. 1000 gm of mother liquor containing 36.28 gm aluminium chloride free from copper was treated with 200 gm soda ash at room temperature. The aluminium hydroxide was precipitated at a pH of 6.5-7.5 to form slurry. The slurry containing aluminium hydroxide and sodium chloride was filtered in filter. The sodium chloride was removed from the cake by washing the same with water. The wet cake of aluminium hydroxide is 360.0 gm is subjected to carbonization at 900°C to 1250° C for at least 4 hours under nitrogen atmosphere. This leads to the production of 65 gm – 100 gm pure Al2O3.

EXAMPLE II

Preparation of aluminium hydroxide and aluminium oxide:

1000 gm of mother liquor containing 14% of aluminium from production of raney nickel catalyst is treated with 100.0 g of formaldehyde (37.0%) at 80°C to 90°C. The reaction is exothermic. The precipitated aluminium hydroxide was removed by filtration. Than washed out of water free from excess alkalinity. The dry cake of aluminium hydroxide is 19.0 gm is subjected to carbonization at 900°C to 1250° C for at least 4 hours under nitrogen atmosphere. This leads to the production of 11.20 gm pure aluminium oxide containing 55.0% of aluminium.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
,CLAIMS:WE CLAIM:

1. A process for the preparation of high-purity aluminium oxide from a waste, the said process comprising the steps of:
a. preparing aluminium hydroxide recovered from a waste containing aluminium chloride, aluminium sulfate, aluminium carbide or any other aluminium salt by hydrolyzing the waste with soda ash;
b. subjecting aluminium hydroxide obtained in step (a) to carbonization treatment at a temperature in the range of 900°C to 1250° C for at least 4 hours.
c. collecting dry powder of aluminium oxide obtained in step (b) and drying the reaction mixture by spin flash drying or any other conventional methods.

2. The process as claimed in claim 1, wherein the step (a) comprises recovering aluminium hydroxide from the waste comprising a mother liquor containing aluminium chloride by hydrolyzing the waste with soda ash followed by filtering the hydrolyzed product to obtain wet aluminium hydroxide.

3. The process as claimed in claim 1 and 2, wherein step (b) of carbonization treatment is carried out at a temperature of 1030°C for at least 4 hours.

4. The process as claimed in any of the preceding claims, wherein the waste used in the step (a) is mother liquor of CPC Green containing aluminium chloride.

5. The process as claimed in claim 1, wherein the step (c) of collecting dry powder of aluminium oxide includes collecting the dry powder either by centrifuging or filter pressing the reaction mixture or any other conventional means and methods.

Dated this 6th day of November 2017.

VAIBHAV VUTTS
of VUTTS & ASSOCIATES LLP
AGENT FOR THE APPLICANTS
IN/PA No.: 1215