Title of Invention

PROCESS FOR PREPARATION OF HYDROXAMIC ACID FLOTATION COLLECTOR AND USES THEREOF

Abstract Present invention relates to the process for preparation of hydroxamic acid flotation collector and uses thereof. Hydroxamic acid salts are prepared by reaction of an ester of fatty acid (C6-C22) with a salt of hydroxylamine and a base under aqueous alcoholic conditions using ultrasonic energy and the hydroxamic acid salts are acidified further in presence of water/oil to isolate free hydroxamic acids (C6-C22) as pure solids/organic solutions.
Full Text THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(Section 10; rule 13)
1. TITLE OF THE INVENTION:
"PROCESS FOR PREPARATION OF HYDROXAMIC ACID FLOTATION COLLECTOR AND USES THEREOF"
2. APPLICANT (S)
Name : Tata consultancy Services Ltd.
Nationality: An Indian Company
Address : Air India Building, 11th floor, Nariman Point, Mumbai - 400 021
3. PREAMBLE TO THE DESCRIPTION
The following specification describes the invention.
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TECHNICAL FIELD OF THE INVENTION
Present invention relates to the process for preparation of hydroxamic acid flotation collector and uses thereof. Hydroxamic acid salts are prepared by reaction of an ester of fatty acid (C6-C22) with a salt of hydroxylamine and a base under aqueous alcoholic conditions using ultrasonic energy and the hydroxamic acid salts are acidified further in presence of water/oil to isolate free hydroxamic acids (Q-C22) as pure solids/organic solutions.
BACKGROUND OF THE INVENTION
Mineral ores such as iron ore, copper ore are obtained from deposits referred to as either high or low-grade deposits. Froth flotation is a process for recovering and concentrating minerals from ores. In a froth flotation process, the ore is wet ground to obtain a pulp. Additives such as collectors, frothers, depressants, activators, etc. are added to the pulp to assist in separating valuable minerals from undesirable gangue portions of the ore in subsequent flotation steps. The pulp is then aerated to produce froth at the surface. The materials which adhere to the bubbles or froth are collected as concentrates. Flotation collectors are the key to flotation process. These performance chemicals such as alkyl hydroxamates selectively adsorb on one of the constituents of the ore and assist in bubble - particle attachment and thus cause flotation separation. The froth product or the reject product or both can then be further processed to obtain the desired grade of the final product, such as by additional flotation stages. Generally, the ore is initially floated to produce a rougher concentrate, the rougher concentrate thereafter being re-floated to further separate the minerals therein and thus enhance the product grade. Typical mineral flotation collector agents include sulfydryl coilector agents such as xanthate and fatty acid based collector agents such as sodium oleate.
Hydroxamic acids and their salts (hereinafter referred to as hydroxamates) are used in collection of minerals such as pyrochlore, muscovite, phosphorite, hematite, pyrolusite, rhodonite, rhodochrosite, chrysocolla, malachite, bornite, calcite, gold and other
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precious metals. Hydroxamates are particularly useful in froth flotation of copper minerals particularly oxidized copper minerals.
Hydroxamic acids and its salts are widely used in mineral processing industry as collectors for separation of minerals by for froth flotation method. A recent review by Fuerstenau and Pradip (Mineral flotation with Hydroxamate collectors, Reagents in the Mineral Industry, Eds. M. J. Jones and R. Oblatt, Inst. Mineral. Met., London, 1984, pp. 161-168) summarizes the flotation application of hydroxamic acids. Hydroxamic acids are found to be more selective than conventional collectors used in the mineral flotation such as fatty acids, amines, petroleum sulfonates and sulfates. However, full commercial utilization of their potential remains unexploited due to the non-availability of a simple yet cost effective method for their production.
The standard laboratory synthetic procedure (Organic Synthesis, Vol. II, pp.67) comprises of a reaction of potassium hydroxide and hydroxylamine hydrochloride in anhydrous methanol. The potassium chloride is then filtered off, and filtrate reacted with methyl caprylate/caprate and allowed to stand at room temperature for 24 hours. The solid potassium salt of hydroxamic acid was isolated by filtration. The process however, is not suitable for industrial scale production due to expensive raw materials, low yields and usage of flammable solvents.
The method described by Gorlovski et al (Vses. Soveshch. Po Sintetich. Zhirozamenitelyam, Poverkhnostnoaktivn, Veschestvam I moyushchim Sredstvam, 3rd, sb., Shebekino, 1965, 297-29: Chem. Abst. 66.4983h, 1967) employs the reaction of methyl ester of a C7-9 carboxylic acid with an aqueous solution of hydroxylamine sulfate and sodium hydroxide at a molar ration of 1:1.22:2.2 at a temperature of 55°C or below to produce sodium salt of hydroxamic acid.
Shchukina et a/(Khim. Prom., Moscow, 1970, 49, pp 220) reported 72-78 % conversion of methyl ester when reacted with hydroxylamine sulfate and sodium hydroxide at 25-60°C. A simple lab method for the reagent designated as IM-50 (containing C7.9
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hydroxamic acids) is also reported by Shchukina et al (Sin. Primen Noykh Proverkh, veshchestv, 1973, pp. 123-131: Chem. Abst. 80,1974, 95199k).
While these reports certainly represent advancement of the art, there are still many drawbacks regarding industrial production.
PRIOR ART References:
US Patent no. 3,933,872 U.S. patent no. 4,629,556 U.S. Patent no. 4,871,466 U.S. Patent no. 5,237,079 U.S. Patent no. 6,145,667 U.S. Patent no. 6,409,022 U.S. Patent no. 6,739,454 U.S. Patent no. 7,007,805
Other references:
1. Fuerstenau, D. W., and Pradip, Reagents in the Minerals industry, IIM Proceedings (M. J. Jones, and R. Oblatt, Eds.), p. 161,1984.
2. Fuerstenau, D. W., Pradip, Khan, L A., and Raghavan, S., Proceedings, XIV International Mineral Processing congress, Toronto, Canada, IV 6.1-12,1983.
3. Fuerstenau, D. W., and Pradip, Intl. J. Mineral Processing32,1 (1991).
4. Ravishankar, S. A., Pradip, Deo M. G., Kulkarni R. A., and Gundiah, S., Bulletin of Material Science 10(5), 423 (1988).
5. Das, K. K., and Pradip, Proceedings, Interfacial Phenomena in Biotechnology and Materials Processing (Y. A. Attia, B. M. Moudgil and S. Chander, Eds.), p. 305. Elsevier, 1988.
6. Pradip, Trans. Indian Inst, of Metals 40(4), 287 (1987).
7. Pradip and N.C. Chaudhari, Trans. Indian Institute of Metals, 50(5), (1997), pp 383-390.

8. Pradip, K K Das, B. Suresh, P. Umasundari and R. Vishwanathan, Proceedings, International Conference on Recent Advances in Metallurgical Processes (ICRAMP-97) (1997), (Eds.) D H Sastry, E S Dwarakadas, G N Iyengar and S. Subramanian, New Age International (P) Limited, New Delhi, India (1997) V-l, pp 33-40.
9. Pradip, Singh, R., Das, K. K., Sankar, T. A. P., Sunilkumar, T. S., Narsimhan, D., and Rao, N. K., Proceedings, XVII International Mineral Processing congress, Dresden, Germany, IV, 151, 1991.
10. Pradip, K. K. Das and R. Singh, Flotation of Complex Sulfide Ores, In Selected Topics in Mineral Processing, (Eds.) Pradip and R. Kumar, Wiley Eastern, New Delhi, India, (1995), pp 118-147.
11. Pradip, Bulletin of Material Science19(2), 267 (1996).
12. Sreenivas, T., and Manohar, C, Mineral Processing and Extractive Met Review 19, 461 (1999) and 20, 503 (2000).
13. Hu, Y., Wang, D., and Xu, Z., Minerals Engineering 10(6), 623 (1997).
14. Quast, K. B., AusIMM Proceedings No 1, p. 7,1999.
15. Fuerstenau, M. C, Harper, R. W., and Miller, 3. D., Trans. SME-AIME 247, 69 (1970).
16. Peterson, A. D., Fuerstenau, M. C, Rickard, R. S., and Miller, 3. D., Trans. SME-AIME232, 388 (1965).
17. Le Normand, 3., Salman, T., and Yoon, R. H., Canadian Metallurgical Quarterly 18,125 (1979).
18. Bogdanov, O. S., Yeropkin, Y. I., Koltimora, T. E., Khobotova, N. P., and Shtchukina, N. F., Proceedings, X International Mineral Processing congress, London, IMM, 553, 1973.
19. Lee, J. S., Nagaraj, D. R., and Coe, 3. E., Minerals Engineering 11(10), 929 (1998).
20. Pavez, O., Brandao, P. R. G., and Peres, A. C. E., Minerals Engineering'9(3), 357 (1996).
21. Assis, S. M., Montenegro, L C. M., and Peres, A. C. E., Minerals Engineering 9(1), 103 (1996).
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22. Yoon, R. H., Nagaraj, D. R., Wang, S. S., and Hilderbrand, T. M., Minerals Engineerings, 457 (1992).
Alkyl hydroxamates are a relatively novel and extremely useful family of flotation collectors. Novel applications of these flotation collectors are being reported recently. For example, in US Patent no. 4,629,556 Purification of kaolin clay by froth flotation using hydroxamate collectors is disclosed. An improved flotation process for removal of colored titaniferous impurities from kaolin clay uses as collector a hydroxamate compound, or a mixture of compounds, having the formula ##STR1## in which R is an alkyl, aryl, or alkylaryl group having 4-28, and preferably 6-24 carbon atoms, and M represents an alkali metal, an alkaline earth metal or hydrogen. The process does not require the use of activators to make the collector adsorb selectively on the colored impurities.
In U.S. Patent no. 7,007,805 a hydroxamate composition for collection of minerals by froth flotation, the composition including an aqueous mixture of hydroxamate wherein the pH of the composition is at least 11 and a method of collecting mineral values from an aqueous ore slurry by froth flotation is disclosed.
In US Patent No. 3,933,872 A method for the preparation of fatty hydroxamates is disclosed, wherein an agitated anhydrous slurry of hydroxylamine sulfate and a lower alkanol solution of a lower ester of a C.sub.6 -C.sub.22 fatty acid is reacted with dimethylamine to provide the corresponding hydroxamic acid which is subsequently neutralized with dimethylamine or an alkali metal base to yield, respectively, the ammonium or alkali metal salt thereof. The said process suffers due to its longer reaction time, poor yields and usage of flammable solvents.
In U.S. Patent no. 4,871,466 A method for the production of alkyl or alkaryl hydroxamic acids and/or salts wherein a C.sub.8 -C.sub.22 alcohol is employed with water as the solvent is disclosed as well as the resultant salt and/or acid solutions per se and their use in the flotation of non-sulfide minerals, preferably clay. However, the final product contains un-reacted ester as well.
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In U.S. Patent no. 5,237,079 A method for the production of alkyl or alkaryl hydroxamic acids and/or salts wherein a C.sub.8 -C.sub.22 alcohol is employed with water as the solvent is disclosed as well as the resultant salt and/or acid solutions per se and their use in the flotation of non-sulfide minerals, preferably clay.
In U.S. Patent no. 6,145,667 Collector compositions of a mixture of a C.sub.6 to C.sub.22 fatty hydroxamic acid and oil for use in the removal of impurities from mineral ores by the froth flotation method is disclosed. The collectors are prepared by reacting an ester of a C.sub.6 to C.sub.22 fatty acid with a hydroxylamine salt and a base in the presence of an oil and water to produce an alkyl hydroxamate salt; acidifying the alkyl hydroxamate salt, forming an organic layer and an aqueous layer, wherein the organic layer contains a C.sub.6 to C.sub.22 fatty hydroxamic acid substantially free of starting esters and hydrolysis and transesterification products of the ester; and separating the organic layer from the aqueous layer to provide a collector composition of the C.sub.6 to C.sub.22 fatty hydroxamic acid and the oil.
In U.S. Patent no. 6,409,022 Collector compositions of a mixture of a C.sub.6 to C.sub.22 fatty hydroxamic acid and oil for use in a method for the removal of impurities from mineral ores by the froth flotation method is disclosed. The collectors are prepared by reacting an ester of a C.sub.6 to C.sub.22 fatty acid with a hydroxylamine salt and a base in the presence of an oil and water to produce an alkyl hydroxamate salt; acidifying the alkyl hydroxamate salt, forming an organic layer and an aqueous layer, wherein the organic layer contains a C.sub.6 to C.sub.22 fatty hydroxamic acid substantially free of starting esters and hydrolysis and transesterification products of the ester; and separating the organic layer from the aqueous layer to provide a collector composition of the C.sub.6 to C.sub.22 fatty hydroxamic acid and the oil.
In U.S. Patent no. 6,739,454 Collector compositions of a mixture of a C.sub.6 to C.sub.22 fatty hydroxamic acid and oil for use in a method the removal of impurities from mineral ores by the froth flotation method is disclosed. The collectors are prepared by reacting an ester of a C.sub.6 to C.sub.22 fatty acid with a hydroxylamine salt and a base in the presence of an oil and water to produce an alkyl hydroxamate salt; acidifying
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the alkyl hydroxamate salt, forming an organic layer and an aqueous layer, wherein the organic layer contains a C.sub.6 to C.sub.22 fatty hydroxamic acid substantially free of starting esters and hydrolysis and transesterification products of the ester; and separating the organic layer from the aqueous layer to provide a collector composition of the C.sub.6 to C.sub.22 fatty hydroxamic acid and the oil. The process requires 3-4 hours of stirring, some times even higher temperature (40-55°C) for complete conversion of esters to hydroxamates in particularly for longer chain length acids. Russian patent No. 390,074 (Chem. Abst. 85, 1976, 66277g) discloses synthesis of a solution of mixed hydroxamic acids (C3.13) in hydrocarbons and its use as a flotation agent. The salts of hydroxamic acids are formed by reacting corresponding esters with hydroxylamine sulfate in aqueous alkaline medium. The salts are neutralized with mineral acid in the presence of a hydrocarbon to obtain a solution of free hydroxamic acids. Due to incomplete conversion of starting ester, the product contains significant amount of un-reacted ester.
As the above list of publications and patents clearly indicates that alkyl hydroxamates are important family of flotation collectors. Improvements in their industrial production are still required so as to reduce costs. For example, all the methods require longer reaction time 3-24 hours and suffer from lower product yields with increasing chain lengths. Some times processes require higher temperatures for completion.
Some of the methods use long chain alcohols which may interfere with the flotation performance of hydroxamates. Use of another surfactant (as disclosed U.S. patent Nos. 6,145,667, 6,409,022 and 6,739,454) may also affect the performance of hydroxamates.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the preferred embodiment
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SUMMARY OF THE INVENTION
The present invention comprises of a more efficient method for preparing hydroxamic acid collectors and their use in mineral flotation. The hydroxamic acids described in the invention are prepared by reacting an ester of a C6-C22 fatty acid with a hydroxylamine salt and a base in the aqueous alcoholic medium such as in water and methanol, under ultrasonic conditions, at ambient temperature (15-30°C) to produce an alkyl hydroxamate salt. The alkyl hydroxamate salt is then acidified with a mineral acid in presence of water/oil to furnish free alkylhydroxamic acid as a solid/organic solution respectively. Pure hydroxamic acid is isolated from the reaction mixture either as free solid by filtration or as an organic solution in oil by phase separation. The product is considerably free of starting ester or any other impurities.
DETAILED DESCRIPTION OF THE INVENTION
Now the objects, features and advantages of the present invention will become apparent from the following detailed description.
The present invention describes a process for the production and use of hydroxamic acid flotation collectors. The collectors are prepared by reacting an ester of a C6-C22 fatty acid with a hydroxylamine salt and a base in the aqueous alcoholic medium under ultrasonic conditions, at ambient temperature (15-30°C) to produce an alkyl hydroxamate salt. The alkyl hydroxamate salt is then acidified with a mineral acid in the presence of water/oil to obtain the free alkylhydroxamic acid "as a solid/organic solution respectively. The product is isolated from the reaction mixture either as free solid by filtration or as an organic solution in oil by phase separation. The solid hydroxamic acid or solution can then be used directly in the froth-flotation of minerals.
The hydroxamic acids are produced in high yields, typically greater than 90% and are free of any impurities such as starting ester, transesterification products, hydrolyzed carboxylic esters, alcohols etc. As a result performance of these collectors in flotation is considerably enhanced as compared to those reported in the prior art.
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As compared to all the references cited in the prior art, the process disclosed in the invention is very rapid (only one hour is required for complete conversion) and involves no heating thereby considerably saving the cost of manufacture. Further, no additional filtration step is required to separate the byproduct K2S04 or Na2S04 as disclosed in some of the prior arts. Use of ultrasonic energy leads to better mixing of reagents, higher conversion of reactants and considerably reduced reaction time. In addition, no additional surfactants/chemicals as disclosed in the prior art are required to facilitate the conversion. Moreover, since reaction takes place in aqueous alcoholic environment, there are no risks involved in handling lower alcohols at the industrial scale.
The process disclosed in the invention comprises of the reaction of ethyl or methyl ester of a fatty acid having 6 to 22 carbon atoms, preferably at least 8 carbon atoms, with hydroxaylamine salt and alkali metal hydroxide in aqueous alcoholic solution under ultrasonic conditions at ambient temperature. The reaction scheme is shown below:

wherein R is a C6.22 alkyl, C6-10 aryl or C7-14 alkaryl group;
M is an alkali metal cation, R' is methyl or ethyl, and X is a halide, sulfate, bisulfate,
phosphate, nitrate or similar anion.
The esters useful for making hydroxamic acid collectors include methyl and ethyl esters of caproic acid (C6), enanthic acid (C7), caprylic acid (C8), pelargonic acid (Cg), capric acid (Cm), undecanoic acid (Cn), lauric acid (Ci2), tridecanoic acid (Ci3), myristic acid (CH), pentadecanoic acid (Ci5), palmitic acid (Ci6), margaric acid (Ci7), stearic acid (Ci8), oleic acid, benzoic acid, naphthoic acid, cyclohexyl carboxylic acid, cyclopentyl carboxylic acid, salicylic acid, ethylbenzoic acid and rice bran fatty acids (a commercial source of fatty acids).
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Hydroxylamine salts, such as hydrochloride or sulfate are used. The alkali metal salts include sodium hydroxide (NaOH), potassium hydroxide (KOH) and the like. The mineral acid used for acidification can be hydrochloric, sulfuric, nitric etc.
The reaction temperature ranges from 15-30°C. The alcohol used belongs to lower alcohols, preferably methanol or ethanol. The amount of water in alcohol varies from about 10-50%.
The ultrasonic energy (750 watt, 20±3 KHz) is supplied through an ultrasonic cleaner bath filled with water. Said ultrasonic energy is supplied through an ultrasonic cleaner bath within a range of 20 to 80 KHz filled with water.
The oil used for preparing hydroxamic acid organic solution can be any suitable oil such as aromatic hydrocarbons, mineral oil fractions, kerosene, light paraffin oil and petroleum fractions.
Complete conversion of starting ester is achieved in very short time (about 1 hour) irrespective of the size of hydrocarbon chain of the starting ester. The yields of free hydroxamic acids are in the range of 25-95% more preferably from 70-90%. TTie free hydroxamic acids are also obtained as an organic solution in oil where the oil is preferably selected from the group consisting of hydrocarbon, vegetable, plant and animal oils. Preferred hydrocarbon oils include but are not limited to aliphatic hydrocarbons, aromatic hydrocarbons, mineral oil fractions, kerosene, light paraffin and petroleum fractions. The composition of hydroxamic acid in oil is 10-70 % by weight.
After the reaction is complete hydroxamic acid salts thus formed are acidified in presence of water/oil using dilute mineral acid preferably hydrochloric acid and free hydroxamic acid is used as such or with other reagents in froth flotation of minerals. The above described hydroxamic acid collectors are useful in the froth flotation of minerals.
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Synthesis Examples:
The following formulation examples illustrate a process for preparation of hydroxamic acid flotation collector and uses thereof. The present invention, however, is not limited to the following exemplified compositions.
Example 1
A suitable two-neck reaction vessel, equipped with a mechanical stirrer and a thermometer, was charged with methanol (3164 parts), sodium hydroxide (1000 parts) and water (400 parts). To this methanolic sodium hydroxide solution, a solution of hydroxylamine sulfate (1107 parts) in water (1600 parts) is added slowly with stirring at the room temperature. The reaction mixture was stirred further for 15 minutes and then cooled to 15-20°C in an ice/water bath and methyl caprylate (1580 parts) was added drop wise with stirring. The reaction mixture was ultrasonicated at the room temperature in an ultrasonic bath (750 watts, 20 kHz) for 45 minutes. The completion of reaction was determined by TLC (thin layer chromatography), which showed the absence of methyl ester in the reaction mixture. The reaction mixture was diluted with water (4000 parts) and acidified with 2000 parts of 33 percent hydrochloric acid. The precipitated white shiny flakes of free octylhydroxamic acid were filtered; washed with water and air-dried. The yield of the dried product (m.p. 79-80°C) was 1480 parts (93.7 %). Spectroscopic analysis of the product revealed absence of any impurities including starting methyl ester or carboxylic acid. As shown in Fig. 1, the characteristic IR peaks for alkyl hydroxamate reagents were present at 1620, 1661, 3256 and 974 cm'1. Proton magnetic resonance spectra (Fig. 2) of the hydroxamic acid exhibited peaks corresponding to methyl protons (triplet, δ 0.95), a-methylene protons (triplet, 8 2.05) and central methylene protons (multiplet, δ 1.3-1.6). Mass spectral analysis (Fig. 3) exhibited a peak at M+ - 32, that is for loss of NHOH group confirming the formation of hydroxamic acid. Experimental elemental analysis of the product was C = 60.52%, H = 12.94% and N= 8.69% which compares very well to theoretically computed values of C = 60.34%, H = 10.76.94% and N= 8.79%.
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Example 2
The procedure described in the Example1 was repeated, replacing sodium hydroxide with potassium hydroxide (1000 parts). The yield of free octylhydroxamic acid was 1360 parts (85.5 %).
Example 3
The procedure of Example 1 was repeated. However, before acidification with hydrochloric acid, light paraffin oil (4000 parts) was added. Following phase separation, the hydroxamates content of resulting oil solution was 35.7%, representing a 90.4 % yield of hydroxamic acid.
Example 4-8
The procedure of Example 1 was again followed, except that the methyl caprylate was replaced by an equal amount of methyl caprate (Example 4), methyl laurate (Example 5), methyl myristate (Example 6), methyl stearate (Example 7) and methyl ester of rice bran fatty acids (Example 8). Similar conversions of the methyl esters to corresponding hydroxamic acids were achieved, yields were in the range of 50-95%.
Application Testing:
Alkyl hydroxamates have been found to be highly selective collectors for a wide variety of flotation separation systems such as those containing copper, iron, rare-earths, tin and tungsten minerals and kaolin. The product produced' by this novel route is comparable in properties to alkyl hydroxamates produced by other methods as indicated earlier in background section of this invention. The example presented below emphasizes its utility in flotation of minerals but not limited to only copper ores.
Flotation of copper ore
Sulphide and oxidized copper ores used in this investigation were from Malanjkhand Copper Project, India. The percent copper content of the two ores was: sulphide ore: 0.8%, oxide ore: 1.2%.
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As analyzed by X-ray diffraction (XRD), the sulphide ore essentially contained chalcopyrite & quartz and oxide ore constituted of malachite & quartz. TTie ore samples were stage crushed in jaw crusher and roll crusher with a vibrating screen in closed circuit to produce minus 10-mesh material. The minus 10 mesh crushed samples of the ores were used for subsequent batch (wet) grinding in a laboratory rod mill (14" x 7) for flotation. I kg of ore was ground at 70% pulp density in a rod mill (12 rods, 2 x 33 cm, 13.06 kg) for 40 minutes.
The flotation tests were carried out in a standard four liters capacity Hindustan Dorr Oliver laboratory flotation cell, with 1 kg of ground ore at 70% pulp density. A schematic diagram of the experimental procedure is shown below for better understanding. The experiments were conducted at; a fixed RPM of 1150 and airflow was maintained at 80cc/sec. An aqueous solution of xanthate (obtained from commercial sources) and alkyl hydroxamate (synthesized as per this invention) was added to the pulp as collector. Pine oil was used as mother.

A schematic representation of experimental procedure for flotation tests
The typical flotation results with alkyl hydroxamic acid collector are summarized in Tables 1 and 2. A considerable improvement in grade and recovery was observed when
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hydroxamic acid collector was used along with the conventional sodium isopropyl xanthate (SIPX) collector.
Table 1: Flotation of oxidized copper ore with hydroxamic acid collector synthesized as per Example 1 of this invention.

Experiment no. Feed grade(% Cu) Collector Dosage 1 2.0 SIPX 50 12.55 72
2 2.0 SIPX HXM 30 50 13.77 88
3 2.0 SIPX HXM 30 50 12.10 90
4 2.0 SIPX HXM 30 50 11.42 86
Table 2: Flotation of a 1:3 mixture of oxidized and sulphide copper ore with hydroxamic acid collector synthesized as per Example 1 of this invention.

Experiment no. Feed grade (% Cu) Collector Dosage(g/t) Concentrate grade (% Cu) Recovery
1 1.1 SIPX 50 13.8 83
2 1.1 SIPX HXM 30 25 10.61 92
3 1.1 SIPX HXM 30 25 11.17 91
4 1.1 SIPX HXM 30 25 12.97 89
There is considerable improvement in recovery of copper values when hydroxamate collector was used along with conventional xanthate collector for the flotation of oxidized copper ore.
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Comparison with commercial alkylhydroxamate collectors:
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The flotation results obtained with hydroxamate collector (synthesized by the novel route as disclosed in this invention) vis-a-vis commercial alkylhydroxamtes namely AERO 6493 (from Cytec, USA) and AM2 (from Ausmelt, Australia) are compared in Table 3. A schematic of experimental procedure followed for these flotation tests is shown below for understanding. The rougher concentrates of the four batches of 3: 1 mixtures of sulphide and oxide ores (obtained by the flotation of 1 kg ore as per the experimental procedure discussed in the previous section) were mixed together, cleaned and recleaned in a laboratory batch flotation cell to obtain the final concentrate (recleaner cone.) in order to simulate the plant practice. The corresponding data for current plant practice is also included for comparison.


Table 3: Comparison of hydroxamic acid collectors (synthesized synthesized as per Example 1 of this invention) with commercially available alkyl hydroxamate collectors.

Currentplantpractice(flotation of Sulphide ore only) Flotation of 3:1 mixtu (pH'9-9.5) -e of sulphide and oxide ore
AM2 (Ausmelt) (US patent # 7007805) AERO 6493 (Cytec) (US patent #6739454) Our sample (synthesized as per Example 1 of this invention)
Dosage(g/t) 22.5 22.5 11.25
Description %Cu %Cu %Fe Insol % Cu %Fe Insol % Cu %Fe Insol
Feed 0.8 0.9 1.2 95.2 0.9 1.2 94.6 0,9 1.2 95.2
Final Tails 0.1 0.1 0.2 98.1 0.1 0.4 97.3 0.1 0.4 97.9
Clean. Tails 4.2 2.8 7.4 83.6 3.1 7.5 81.4 2.4 5,8 84.1
Reclean. Tails 3.3 8.1 15.0 62.1 6.0 14.9 66.5 12.3 17.6 55.4
Rough. Cone. 12.1 12.7 16.3 53.3 17.6 19.4 40.1 20.8 22.9 30.5
Clean. Cone. 22.5 22.2 24.9 24.3 25.9 26.2 16.5 26.1 27.8 15.1
Reclean. Cone. 26.2* 27.3 28.4 10.9 27.8 27.3 11.6 28.0 29.2 9.4
As compared to other commercial samples the dosages required for our sample is much lower. However, it should be noticed that our sample consists of 100% hydroxamate whereas commercial samples obtained from Cytec and Ausmelt have only 50% hydroxamates (as per the supplier's information).
Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter.
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Claim:
1. A process for preparation of hydroxamic acid flotation collector comprising:
reacting an ester of a fatty acid having 6 to 22 carbon atoms, with a
hydroxylamine salt and a base in the aqueous alcoholic medium under ultrasonic
energy, at ambient temperature to produce an alkyl hydroxamate salt;
acidifying said alkyl hydroxamate salt with a mineral acid in the presence of water and/or oil to obtain the free alkylhydroxamic acid as a solid/organic solution;
isolating the said solid/organic solution from the reaction mixture using dilute mineral acid and free hydroxamic acid thus produced is used as such or with other reagents in froth flotation of minerals.
2. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said ester of a fatty acid has 8 carbon atoms.
3. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said dilute mineral acid is hydrochloric acid.
4. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said Hydroxylamine salt is hydrochloride.
5. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said Hydroxylamine salt is sulfate.
6. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said aqueous alcoholic medium has lower alcohols.
7. A process for preparation of hydroxamic acid flotation collector as claimed in claim 6 wherein said lower alcohol is methanol or ethanol.
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8. A process for preparation of hydroxamic acid flotation collector as claimed in claim 6 wherein amount of said water in said alcohol varies from 10-50%.
9. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said alkali metal salts are sodium hydroxide or potassium hydroxide.
10. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said oil is aromatic hydrocarbons; mineral oil fractions, kerosene, light paraffin oil and petroleum fractions.
11. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said mineral acid is hydrochloric acid or sulphuric acid or nitric acid.
12. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said free alkylhydroxamic acid solid/organic solution is isolated as free solid by filtration or as an organic solution in oil by phase separation.
13. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said ambient temperature is 15-30°C.
14. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said esters are methyl and ethyl esters of caproic acid (C6), enanthic acid (C7), caprylic acid (C8), pelargonic acid (C9), capric acid (C10), undecanoic acid (di), lauric acid (da), tridecanoic acid (d3), myristic acid (d4), pentadecanoic acid (C15), palmitic acid (C16), margaric acid (C17), stearic acid (C18), oleic acid, benzoic acid, naphthoic acid, cyclohexyl carboxylic acid, cyclopentyl carboxylic acid, salicylic acid, ethylbenzoic acid and rice bran fatty acids.
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15. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said ultrasonic energy is about 750 watt and 20±3 KHz.
16. A process for preparation of hydroxamic acid flotation collector as claimed in claim 15 wherein said ultrasonic energy is supplied through an ultrasonic cleaner bath within a range of 20 to 80 KHz filled with water.
17. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said free hydroxamic acids are also obtained as an organic solution in oil.
18. A process for preparation of hydroxamic acid flotation collector as claimed in claim 17 wherein said oil selected from the group consisting of hydrocarbon, vegetable, plant and animal oils.
19. A process for preparation of hydroxamic acid flotation collector as claimed in claim 17 wherein said hydroxamic acid in said oil is 10-70 % by weight.
20. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein the yield of said free hydroxamic acids is greater than 90%.
21. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 wherein said process is carried out in less than one hour irrespective of the size of hydrocarbon chain of the starting ester.
22. A process for preparation of hydroxamic acid flotation collector as claimed in claim 1 to claim 21 substantially as herein described with reference to the accompanying specification.

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Documents:

539-MUM-2007-ANNEXURE 1 TO 2(5-8-2011).pdf

539-MUM-2007-ANNEXURE 1(30-5-2012).pdf

539-MUM-2007-CLAIMS(AMENDED)-(2-8-2013).pdf

539-MUM-2007-CLAIMS(GRANTED)-(30-8-2013).pdf

539-MUM-2007-CLAIMS(MARKED COPY)-(2-8-2013).pdf

539-mum-2007-claims.doc

539-mum-2007-claims.pdf

539-mum-2007-correspondence 1(25-4-2008).pdf

539-mum-2007-correspondence 2(21-3-2007).pdf

539-mum-2007-correspondence 3(25-3-2008).pdf

539-MUM-2007-CORRESPONDENCE(16-7-2013).pdf

539-MUM-2007-CORRESPONDENCE(19-3-2012).pdf

539-MUM-2007-CORRESPONDENCE(27-4-2009).pdf

539-MUM-2007-CORRESPONDENCE(6-8-2009).pdf

539-MUM-2007-CORRESPONDENCE(IPO)-(30-8-2013).pdf

539-mum-2007-correspondence-received.pdf

539-mum-2007-descripiton (complete).pdf

539-MUM-2007-DESCRIPTION(GRANTED)-(30-8-2013).pdf

539-MUM-2007-DRAWING(GRANTED)-(30-8-2013).pdf

539-mum-2007-drawings.pdf

539-mum-2007-form 1(23-3-2007).pdf

539-mum-2007-form 13(8-5-2008).pdf

539-mum-2007-form 13.(8-5-2008).pdf

539-MUM-2007-FORM 18(27-4-2009).pdf

539-MUM-2007-FORM 2(GRANTED)-(30-8-2013).pdf

539-MUM-2007-FORM 2(TITLE PAGE)-(GRANTED)-(30-8-2013).pdf

539-MUM-2007-FORM 26(2-8-2013).pdf

539-mum-2007-form 26(25-3-2008).pdf

539-MUM-2007-FORM 26(6-8-2009).pdf

539-mum-2007-form 3(23-3-2007).pdf

539-MUM-2007-FORM 3(30-5-2012).pdf

539-mum-2007-form 5(23-3-2007).pdf

539-mum-2007-form-1.pdf

539-mum-2007-form-2.doc

539-mum-2007-form-2.pdf

539-MUM-2007-REPLY TO EXAMINATION REPORT(30-5-2012).pdf

539-MUM-2007-REPLY TO EXAMINATION REPORT(5-8-2011).pdf

539-MUM-2007-REPLY TO HEARING(2-8-2013).pdf

539-MUM-2007-REPLY TO HEARING(22-8-2013).pdf


Patent Number 257084
Indian Patent Application Number 539/MUM/2007
PG Journal Number 36/2013
Publication Date 06-Sep-2013
Grant Date 30-Aug-2013
Date of Filing 23-Mar-2007
Name of Patentee TATA CONSULTANCY SERVICES LIMITED
Applicant Address AIR INDIA BUILDING, 11TH FLOOR, NARIMAN POINT, MUMBAI-400 021
Inventors:
# Inventor's Name Inventor's Address
1 PRADIP TATA R&D DESIGN CENTRE, (A DIVISION OF TATA CONSULTANCY SERVICES LTD.) 54B, HADAPSAR INDUSTRIAL ESTATE, PUNE-411013
2 BEENA RAI TATA R&D DESIGN CENTRE, (A DIVISION OF TATA CONSULTANCY SERVICES LTD.) 54B, HADAPSAR INDUSTRIAL ESTATE, PUNE-411013
PCT International Classification Number B03D1/004
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA