GB2068404A - Process for bleaching oils and fats - Google Patents

Abstract

A process for bleaching oils and fats, especially vegetable and animal products such as palm oil, coconut oil, sal oil, bay tree leaf oil, rice bran oil and tallow, comprises treating the oil or fat with a polar bleaching agent, for example, hypochlorite, peroxide, peroxyacid, in the presence of a phase transfer catalyst. The catalyst is preferably cationic and may be a quaternary ammonium compound, for example, tetra-n-butyl ammonium hydroxide, tetra-n-octyl ammonium bromide or di(hydrogenated tallow alkyl)dimethyl ammonium chloride. Oils and fats bleached by this method may be used for soap-making.

Description

SPECIFICATION Process for bleaching naturally-occurring oils and fats The present invention relates to a process for bleaching naturally-occurring oils and fats, and has especial applicability to the bleaching of certain oils and fats used as raw materials in soap-making, for example, palm oil, coconut oil, tallow and rice bran oil.

These oils are generally fairly highly coloured and for aesthetic reasons require bleaching before they can be used in soap-making. Some commercially significant vegetable oils are highly coloured owing to the presence of chromophoric impurities: one which is particularly highly coloured is palm oil, which has been estimated to contain up to about 0.2% of the red pigment beta-carotene. Palm oil is derived from the pericarp (the thick fibrous outer layer) of the fruit of the oil palm, elaeis guineensis, and contains about 48% of hexadecanoic (palmitic) acid and about 38% of oleic acids.Decolorisation of palm oil is currently carried out using an adsorbent solid material, sulphuric acid-activated Fuller's earth, and high levels of this material (up to about 12% by weight) are required for adequate bleaching, both because of the high concentration of coloured impurities and because of the hydrophobic nature of the oil. The earth bleach adsorbs approximately its own weight of oil, which is lost, so that the current process is expensive both in terms of catalyst consumption and in terms of oil loss. The disposal of the spent earth also presents a problem.

Sal and rice bran oils, which are important raw materials for soap in the Indian sub-continent, are currently bleached with chlorine dioxide. This is a hazardous reagent which can present process control difficulties. Neem, another important Indian oil, is bleached using sodium chlorite and mild acid.

It has now been found that oils and fats can be successfully bleached with milder aqueous bleaching agents such as hypochlorite and peroxide, in the presence of a phase transfer catalyst.

The action of polar bleaching agents such as hypochlorite on these oils in the absence of a catalyst is slow and incomplete because of the hydrophobic nature of the oils. The reaction (oxidation or reduction of the coloured impurity) probably takes place in the organic phase and the bleaching agent in the aqueous phase cannot easily penetrate the organic phase to reach the reaction site.

A phase transfer catalyst is a charged compound which also possesses significant oil solubility.

Such a material can assist in a reaction between a charged species and a hydrophobic substrate in an organic phase by carrying the charged species, for example, as an ion pair, into the organic phase.

The use of phase transfer catalysts for oxidising hydrophobic substances such as amines, amides, alcohols and organic compounds containing an activated doubled bond is described in an article in Tetrahedron Letters, 1976,20, p. 1641-1644 and in United States Patent No. 3,996,259. Other articles on Phase transfer catalysis appear in Angewandte Chemie International 1977, 16, p.493--505; Aldrichimica Acta 1976, 9, p.3 5-45; and J. Chem. Ed. 1978, 55, p.429-433.

Clearly, a phase transfer catalyst must be of appropriate charge type for the polar reaction species involved. For a bleaching process involving an anionic species such as hypochlorite ion, hydroperoxide ion or a peroxoacid anion, the catalyst cannot itself be anionic, and an anionic surface-active agent will have no phase-transfer catalytic effect on such a reaction.

Japanese Patent No. 3633/1950 to Nojima and Ishikawa discloses a process for the decolorisation of rice bran oil in which a small proportion of the oil is either sulphonated or saponified and the oil is then bleached with hydrogen peroxide. the sulphonate or carbonoxylate present here is anionic and is thus not of the appropriate charge type to behave as a phase transfer catalyst.

In its broadest aspect the present invention provides a process for bleaching an oil or fat, which comprises treating the oil or fat with a polar bleaching agent in the presence of a phase transfer catalyst.

The invention is particularly relevant to the bleaching of naturally-occurring oils, especially those used in soap-making. Examples of vegetable oils to which the invention is applicable are palm oil, coconut oil, bay tree leaf oil, sal oil, neem oil and rise bran oil; an example of an animal product is tallow.

The bleaching agent should be selected according to the chromophoric impurity to be removed. In general, the chromophores present in the oils used for soapmaking, for example, the beta-carotene in palm oil and the chlorophyll in sal oil, are most easily dealt with by oxidation, and therefore oxidative bleaches are appropriate. Examples of suitable oxidative bleaches are salts of hydrochlorous acid, and most preferably sodium hypochlorite; peroxyacids such as peracetic acid also give excellent results.

Other oxidative bleaching agents that may be used include "hyprox" (a sodium hypochlorite/hydrogen peroxide mixture), hydrogen peroxide itself, chlorites, organic chloramines and chlorinated trisodium phosphate.

The use of reductive bleaching agents such as dithionite and borohydride is also within the scope of the invention. These are appropriate when the coloured impurity is reducible, rather than oxidisable, to form a colourless product, for example, fluorenone to fluorenol or azo dyes to diamino compounds.

The bleaching agent will preferably be present in the reaction mixture in an amount of from 0.5 to 10% by weight based on the weight of the oil or fat, the optimum amount depending on the bleaching agent and the oil or fat used. Sodium hypochlorite is preferably used in an amount of from 1.5 to 8.0% by weight, preferably 2 to 4.5% by weight for palm oil and 5 to 7.5% by weight for sal or rice bran oil.

Peracetic acid is advantageously used in an amount of from 3 to 10% by weight, and hydrogen peroxide in the same amount, the percentages being by weight of the oil or fat.

The phase transfer catalysts used according to the present invention will in general be cationic for compatibility with anionic bleaches such as hypochlorite, hydrogen peroxide or peracetic acid, and quaternary ammonium compounds and quaternary phosphonium compounds are especially suitable, quaternary ammonium compounds being preferred on grounds of cost and availability.

These quaternary ammonium compounds preferably have the general formula R,R2R3R4 N+ N in which R1R2R3 and R4 ar; C1 and C22 alkyl groups, the total number of carbon atoms in the R groups being at least 16, and X7 is a monovalent anion, especially halide, or 1/m of an m-valent anion.

For a given total number of carbon atoms in the R groups, four intermediate length chains give better results than one or two long ones. Tetra-n-octyl ammonium bromide is an outstandingly efficient phase transfer catalyst, and tetra-n-butyl ammonium chloride is also effective, but less so than the tetra C8 compound.

Compounds of the type in which two of the R groups are C1 to C3 alkyl, especially methyl, and the other two C10 to C22 are efficient, cost-effective catalysts. An example of this type is di(hydrogenated tallow alkyl) dimethyl ammonium chloride, available commercially as Arquad (Trade Mark) 2HT.

Finally, quaternary ammonium compounds having one long chain and three lower alkyl groups, such as cetyl trimethyl ammonium chloride, are also useful as phase transfer catalysts according to the invention.

The phase transfer catalyst is preferably used in an amount of from 0.2 to 10 mole %; based on the bleaching agent, especially 0.5 to 4 mole %.

The reaction temperature is preferably from 30 to 800 C, from 45 to 60"C being especially preferred for palm oil, and slightly higher temperatures (up to 750C) being preferred for sal and rice bran oils.

The preferred pH is from 7 to 11, preferably from .5 to 9.5.

As well as increasing the rate of bleaching, the presence of the phase transfer catalyst gives a more completely bleached product. It has been found, for example, that palm oil of sufficiently low colour level for soap-making cannot be obtained using hypochlorite unless a phase transfer catalyst is used.

The process of the invention may be carried out as two-stage operation. In the first stage the oil (brought to the preferred temperature of 45 to 600C, for example by steam heating), the bleach and the catalyst may be mixed together in a suitable bleach vessel. The reacted mixture may then be transferred to a settler or a rotating disc separator, where the aqueous phase can be washed out with 20% brine and the bleached oil drawn off for deodorisation (if necessary) and fed to, for example, soap-making plants.

If the oil to be bleached has a high concentration of free fatty acids, as does rice bran oil, it may be advantageous either to distill off these volatile acids or to esterify them (for example, using methanol or ethanol with toluene sulphonic acid as catalyst) before bleaching. This is however by no means essential.

The following Examples illustate the invention.

EXAMPLE 1 Paim oil (25 g) and water (25 g) were placed in a flask together with sodium hypochlorite (2% by weight of the palm oil) and tetra-n-butyl ammonium hydroxide (0.7% by weight of the palm oil). The mixture was then adjusted to pH 9 and the flask and contents placed in a constant temperature water bath to give a reaction temperature of 300 C.

The reaction was continued for one hour, after which time sodium sulphite was added to remove any unused sodium hypochlorite. The bleached palm oil was then extracted with hexane with the addition of salt solution to aid phase separation. The solvent was removed under vacuum, and samples of the bleached palm oil were evaluated in a qualitative manner (visually) and quantitatively (by measurement of the optical density at 446 nm of a 1% solution in hexane using a Pye-Unicam SP 800 spectrophotometer). The results are shown in Table 1.

TABLE 1

Optical Sample Colour density Untreated palm oil Bright orange 1.04 Palm oil bleached without phase transfer catalyst Pale yellow 0.20 Palm oil bleached with phase transfer catalyst White 0.01 The above Example illustrates the increased effectiveness of bleaching reactions applied to palm oil which can be achieved by use of a phase transfer catalyst.

EXAMPLE 2 Palm oil (100 g) was added to a flask containing 100 g of an aqueous solution of sodium hypochlorite (1% by weight based on the palm oil). Tetra-n-butyl ammonium hydroxide (10 mole % based on the bleach, 0.35% by weight based on the oil) was added to the mixture and the contents of the flask were stirred at 500-600 r.p.m. at 30 C for one hour.

A control experiment using identical reaction conditions, except that the catalyst was omitted, was also carried out for comparison purposes.

After the reaction time of one hour had elapsed a solution of sodium sulphite was added to destroy any excess of bleach, the mixture was transferred to a separating funnel and partitioned between ether and saturated sodium chloride solution. The ether layer was removed, dried over anhydrous magnesium sulphate, filtered and concentrated under reduced pressure.

Measurements of the optical density of the bleached and unbleached oils were made at 446 nm on a 1% oil solution in hexane, using a Pye-Unicam SP 800 spectrophotometer. The results were as follows: Optical density Unbleached oil 1.04 Bleached oil (uncatalysed) 0.68 Bleached oil (catalysed) 0.48 The "percentage of bleaching" was calculated according to the following equation: optical density of ~~~~~~~~~ optical density of % bleaching = unbleached oil bleached oil optical density of unbleached oil and was found to be 34.6% for the uncatalysed sample and 53.8% for the catalysed sample.

EXAMPLE 3 The procedure of Example 2 was repeated using various bleach concentrations, reaction temperatures and reaction times. The optical densities were measured, and the percentages of bleaching calculated, as in Example 2. The results are shown in Table 2, from which the improvement obtained by using the phase transfer catalyst can readily be seen.

TABLE 2

Bleach % Bleaching concn. Reaction Reaction temp. (C) time (h) pH uncatalysed catalysed (a) | 1 | 30 | 1 | 9 | 36.2 | 52.9 (b) 1 50 1 9 20.6 32 A (c) 1 1 30 2- 9 34.0 44.0 (d) 1 30 3 9 30.3 67,4 (e) 2 L 30 1 9 88.5 100.0* *The optical density of the bleached oil was outside the detection limits of the machine (#0,01), although the oil was not water-white.

EXAMPLE 4 The procedure of Example 2 was repeated using peracetic acid instead of sodium hypochlorite.

The concentration of peracetic acid used was 2% by weight based on the oil, the catalyst concentration was 10 mole % based on the peracetic acid (0.68% by weight based on the palm oil), the reaction time was one hour, the reaction temperature 50 C, and the pH 9. A corresponding uncatalysed run was also carried out.

Optical densities were measured as in Example 2 and were as follows: Optical density Unbleached oil 1.04 Bleached oil (uncatalysed) 0.74 Bleached oil (catalysed) 0.03 The percentages of bleaching were thus 28.8% (uncatalysed) and 97.1% (catalysed).

EXAMPLE 5 The experiment of Example 4 was repeated at bleach concentrations of 1% and 2%, other conditions remaining the same. The results are shown in Table 3.

TABLE 3

Bleach % Bleaching concn. catalysed %: catalysed (a) 1 29.7 83.2 (b) 2: 28.4' 97.5- EXAMPLE 6 The procedure of Example 2 was repeated using sodium chlorite instead of sodium hypochlorite.

The bleach concentration was 1% by weight based on the palm oil, the catalyst concentration was 10 mole % based on the bleach (0.29% by weight based on the palm oil), the reaction time was one hour, the reaction temperature 300C and the pH was 9. A comparison uncatalysed run was also carried out.

Optical densities and percentages of bleaching were as follows: Optical density % bleaching Unbleached oil 1.04 Bleached oil (uncatalysed) 1.04 0 Bleached oil (catalysed) 0.86 17.3 It will be seen that no measurable bleaching occurred at all unless the phase transfer catalyst tetra-n-butyl ammonium hydroxide was present.

EXAMPLE 7 The procedure of Example 2 was repeated using hydrogen peroxide instead of sodium hypochlorite. The bleach concentration was 1% by weight based on the palm oil, the catalyst concentration was 10 mole % based on the bleach (0.76% by weight based on the palm oil), the reaction time was one hour and the pH was 1 0. The results are given in Table 4.

TABLE 4

Reaction Optical density % bleaching temp.

( C) uncatalysed catalysed uncatalysed catalysed 30 1.0 0.93 3.8 10.6 75 0.83 0.52 20.2 50.0 At both temperatures the use of the catalyst represented a considerably improvement over the uncatalysed reaction, but substantially better results were obtained at 75 C.

EXAMPLE 8 A series of experiments was carried out using the procedure of Example 2, to illustrate the effect of reaction temperature on the colour of the bleached oil in the palm oil/sodium hypochlorite system. In this Example the catalyst used was Arquad (Trade Mark) 2HT (di-(hydrogenated tallow alkyl) dimethyl ammonium chloride). The concentration of sodium hypochlorite usbd was 2.5% based on the palm oil, the catalyst concentration was 2.5 mole % based on the bleach, the pH was 9 and the reaction time was 2 hours. The results are shown in Table 5. The colour was measured using a Lovibond tintometer: R denotes red, Y yellow and B blue. The cell length was 51/4 inches (133.4 mm). The unbleached oil had a colour equivalent to 120 R 273 Y in a Lovibond 1.33.4 mm cell; this value was obtained by scaling-up a reading taken in a smaller cell.

TABLE 5.

Lovibond colour Temperature C uncatalysed catalysed 30 5R 43Y 3.4R 30Y 40 4F 38Y 0.1B 2R 20Y 50 2.8R 23Y 1.5R 15Y 70 1R 28Y 1R 14Y EXAMPLE 9 Using the procedure of Example 2, a series of experiments was carried out to illustrate the effect of hypochlorite concentration on the colour of the bleached palm oil. The catalyst used was Arquad (Trade Mark) 2HT, the pH was 9, and the temperature was 500C. The results are set out in Table 6.

TABLE 6

Catalyst Bleach concn.

concn. (mole % Reaction Lovibond colour (% based based on time on oil) bleach) (hours) uncatalysed catalysed 2;0 2,5- 1 5.7-R 51.5Y 2.6R 15Y 2;5- 2.5 1 3.8R 39 Y 2.1R 25Y 3.0 2.5 1 3.3.R 30 Y 2.3R 20Y 6.0 1.0 2- 2 R 17 Y 1 R 8Y All catalyst levels gave good results.

EXAMPLE 10 The experiments of Example 9 were repeated with varying levels of catalyst to determine the effect of this variable on the product colour. The results are shown in Table 7.

TABLE 7

Hypo- Catalyst chlorite concn.

concn. (mole % Reaction Lovibond colour (% based | based on | Time on oil bleach) thours) uncatalysed catalysed (a) 2.0 (i) 2.5 1 5.7R 51.5R 51.5Y 2.6R 15Y (ii) 5.0 1 7.7R 61 Y 2.9R 21Y (b) 2.5 (i) 1.0 1 5 R 40 Y 3 R 22Y (ii) 2.5 1 3.8R 39 Y 2.1R 25Y (iii) 4.0 1 7.1R 60 Y 29R 22Y (iv) 5.0 1 7.4R 65 V 3.3R 30Y (c) 3.0 (i) 1.0 1 3 R 22 Y 2.4R 15Y (ii) 2.5 1 3.1R 20 Y 2.1R 15Y (iii) 3.0 1 4 R 24 Y 2.3R 13Y (d) 6.0 1.0 | 2 2 . R 17 Y 1 R 8Y In all cases the product produced by the catalysed process was significantly better than that produced by the corresponding uncatalysed process.

EXAMPLE 11 Using the procedure of Example 2, the products produced by the hypochlorite bleaching of palm oil in the presence of three phase transfer catalysts were compared. The hypochlorite concentration was 2.5% based on the oil, the reaction temperature was 500C, the reaction time was one hour, and the pH was 9.0. The results are shown in Table 8.

TABLE 8

Mole%: concn. Lovibond colour (based on Catalyst bleach) uncatalysed catalysed Arquad (Trade Mark) 2;HT 2;S 3.8R 39V 2;1R 25V Tetra-n-octyl ammonium bromide 1,0 3 R 16Y 1.7R 11Y Tetra-n-buty I ammonium hydroxide 10.0 10 R 32Y 5 R 33Y This test demonstrates the superiority of tetra-n-octyl ammonium bromide. The product obtained using Arquad (Trade Mark) 2 HT was, however, acceptable.

EXAMPLE 12.

A series of experiments was carried out, using the procedure of Example 2, to determine the influence of pH and reaction time on the colour of palm oil bleached by the hypochlorite/Arquad (Trade Mark) 2 HT system. The bleach concentration was 2.5% based on the oil and the catalyst concentration was 2.5 mole % based on the bleach. Table 9 shows the effect of reaction time at reaction temperature 500C and pH 9.

TABLE 9

Lovibond colour Reaction time (hours) uncatalysed catalysed 1 3.8R 39Y 2.1R 25V 2- 2.8R 32Y 1.5R 15Y 2 3 R 30Y 1.4R 13Y 3 3 R 34Y 1.6 R 19Y Table 10 shows the effect of pH at one hour reaction time and reaction temperature 500C.

TABLE 10

Lovibond colour pH uncatalysed catalysed 8 23 R 62Y 16 R 60Y 9 3.8R 39Y 2;1 R 25Y 10 | 7.9R 40Y 2.SR 40Y 11 5;2R 26Y 4' R 23Y The results indicate that at 500C a reaction time of two hours and a pH of 9 represent optimum conditions.

EXAMPLE 13 An experiment was carried out to demonstrate that the decomposition of the pigment carotene (the main coloured impurity in palm oil) by hypochlorite is accelerated by Arquad (Trade Mark) 2 HT.

The pigment was dissolved in petrol and reacted with sodium hypochlorite (0.4M) in the presence of 0.002 5M Arquad (Trade Mark) 2 HT at 300C and pH 11.6. A control experiment was also run in which the catalyst was omitted. The reacticns were carried out in dark vessels to avoid photobleaching.

The petrol solution was sampled at regular intervals and the pseudo-first order reaction rate constants were found to be 8.14 x 1 O-6 sec -' for the uncatalysed case and 4.07 x 10-4 sec -1 in the catalysed case, the latter representing an approximately 50-fold rate enhancement.

EXAMPLE 14 Using the procedure of Example 2, samples of palm oil were bleached with peracetic acid and "hyprox" (sodium hypochlorite/hydrogen peroxide), both with and without catalyst. The reaction time was one hour and the catalyst was Arquad (Trade Mark) 2 HT in each case. The results are shown in Table 11.

TABLE 11

Catalyst Bleach concn.

concn. (mole % Lovibond colour (% on on Temp.

Bleach oil bleach) C pH uncatalysed catalysed Per acetic | | | | | | | acid 2- 2;5- 50 9 52.5R 126Y 47R 20Y 3 2;5- 60 9 47 R 120Y 25R 35Y " | 4 | 2.5 | 60 | 9 | 16 R 25Y | 16R 24Y 5 5 | 2.5 60 10 21 R 20Y 19R 17Y " 4. 4.0 80 10 16 R 146Y 5R 21Y - " 5. 2.5 60 9 21 R 20Y 19R 17Y Sodium hypo chlorite 2.5 2.5 50 9 41 R 20Y 2.3R 25Y plus hydrogen 0.25 peroxide It was found that peracetie acid was a considerably less effective bleaching agent than hypochlorite for decolourising palm oil. The "hyprox" gave results comparable with those obtained using hypochlorite alone.

EXAMPLE 15 Using procedures analogous to that of Example 2, samples of coconut oil were bleached with sodium hypochlorite and "hyprox" in the presence of Arquad (Trade Mark) 2 HT. The reaction temperature was 450C in each case.

Table 12 shows the results obtained using a sample of good quality coconut oil of Lovibond colour 3.5R 1 1Y The catalyst concentration was 2.5 mole % based on bleach in each case.

TABLE 12

Bleach concn. Lovibond colour (% on | Time Bleach oil) (hours) pH uncatalysed catalysed NaOCl 2.5 1 9 1 R 4Y 1 R 3Y NaOCI 5.0- 1 9 0.5R 4Y 0;5R 3Y +H2O2 0.5 1 9 0.3R 2Y 0 R 2Y Table 13 shows the results obtained using a sample of Philippines coconut oil of Lovibond colour 10R 50Y.

TABLE 13

Catalyst Bleach concn.

concn. (mole % Lovibond colour (% on on Time Bleach oil) bleach) (hours) pH uncatalysed catalysed NaOCl 2.5 2.5 1 9 3 R 4 Y 2 R 3Y NaOCl 2.5 2.5 2 9 1.5R 3 Y 1.5R 2Y NaOCl 2.5 2.5 1 4 0 R 3.5Y 0 R 2Y NaOCl 2.5 2.5 1 11 5 R 7 Y 5 R 5Y NaOCl 2.5 # 2;;5 1 9 1.5R 3 Y 0;5R 3Y NaOCl 2.5 # 5.0 1 9 3 R 4 Y 0.9R 3Y Even with the more highly coloured Philippines oil most of the bleached samples were of soap-makin-q quality.

EXAMPLE 16 Using a procedure analogous to that of Example 2, a sample of Grade 4 tallow was bleached with sodium hypochlorite (2.5% based on the tallow) in the presence and absence of Arquad (Trade Mark) 2 HT (2.5 mole % based on the bleach). The temperature was 50 C, the reaction time was 2 hours and the pH was 9. The Lovibond colours of the tallow before and after bleaching were as follows: Untreated 52.5R 210Y 210Y 15.2B Bleached (uncatalysed) 8.6R 62Y 2.9B Bleached (catalysed) 5.6R 23Ys 2.68 The use of the catalyst thus effected a considerable improvement in the quality of the product.

EXAMPLE 17 A sample of bay tree leaf oil was bleached, according to a procedure analogous to that of Example 2, with sodium hypochlorite (6% based on the oil) in the presence and absence of Arquad (Trade Mark) 2 HT (2.5% based on the bleach), at 60 C and pH 9 for one hour. The Lovibond colours of the oil were as follows: Uncatalysed 43Y 325Y Catalysed 37.8V 36Y EXAMPLE 18 Samples of sal oil were bleached, by a procedure analogous to that of Example 2, with sodium hypochlorite, in the presence and absence of Arquad (Trade Mark) 2 HT, at 500C and pH 11. The catalyst concentration was 1 mole % based on the bleach. The results are shown in Table 14. TABLE 14'

Reaction Lovibond colour Bleach concn. Time (% of oil) (hours) uncatalysed catalysed 7.5 2 1.5R 6Y 1.5R 5.6R 6 2.25 10.5R 52Y 3.1R 20 Y (3 additions of 2% at 45 minute intervals) A commercial sample that had been bleached with chlorine dioxide had a Lovibond colour equivalent to 50R 36Y in the 133.4 mm cell (scaled-up from a reading taken in a smaller cell). The phase-catalysed bleached product thus represents a substantial improvement.

EXAMPLE 19 Samples of hardened rice bran oil were bleached, using a procedure analogous to that of Example 2, with sodium hypochlorite in the presence and absence of Arquad (Trade Mark) 2 HT. The reaction time was 2 hours. Since rice bran oil is extremely strongly coloured, Lovibond colours in this Example were measured using a 5 mm (±inch) cell. The results are shown in Table 15.

TABLE 15

Catalysed level Lovibond colour Total colour (5R + Y) Bleach level (weight % (Mole % Temp (% on oil) on oil) on bleach) C Uncatalysed Catalysed Uncatalysed Catalysed 5 0.935 50 5.1R 41Y 6R 30Y 66.5 60 7.5 0.56 59 4.4R 74Y 4R 74Y 4R 37Y 96 57 7.5 1.40 50 4.4R 74Y 4.7R 21Y 96 44.5 7.5 0.45 50 - 4.2R 25Y - 46 (3 additions of 2,5% at # 0.45 60 - 5R 23Y - 48.5 45-minute intervals 4.5 0.27 60 - 4R 27Y - 47 (3 additions of 1.5% at # 0.27 60 - 4R 21Y - 51 45-minute intervals) 7.5 0.56 50 - 4.4R 31Y - 53 7.5 0.56 50 5R 26Y - 51 (with addition of nickel # palmitate to give 400 ppm N

Claims (23)

CLAIMS:

1. A process for bleaching an oil or fat, which comprises treating the oil or fat with q polar bleaching agent in the presence of a phase transfer catalyst.

2. A process as claimed in claim 1, wherein the oil or fat is a vegetable or animal product.

3. A process as claimed in claim 2, wherein the oil or fat is a vegetable oil selected from palm oil, coconut oil, rice bran oil, bay tree leaf oil and sal oil.

4. A process as claimed in any one of claims 1 to 3, wherein the bleaching agent is oxidative.

5. A process as claimed in claim 4, wherein the bleaching agent is hypochlorite ion.

6. A process as claimed in claim 4, wherein the bleaching agent is a peroxo compound.

7. A process as claimed in claim 6, wherein the bleaching agent is a per-acid.

8. A process as claimed in any preceding claim, wherein the bleaching agent is used in an amount of from 0.5 to 10% by weight based on the oil or fat.

9. A process as claimed in claim 8, wherein the bleaching agent is a hypochlorite and is used in an amount of from 1.5 to 8.0% by weight based on the oil or fat.

10. A process as claimed in claim 9, wherein the oil or fat is palm oil, and the bleaching agent is sodium hypochlorite and is used in an amount of from 2 to 4.5% by weight based on the palm oil.

11. A process as claimed in claim 9, wherein the oil or fat is sal oil or rice bran oil, and the bleaching agent is sodium hypochlorite and is used in an amount of 5 to 7.5% by weight based on the oil.

1 2. A process as claimed in claim 8, wherein the bleaching agent is a per-acid and is used in an amount of from 3 to 10% by weight based on the oil or fat.

13. A process as claimed in any preceding claim, wherein the phase transfer catalyst is cationic.

14. A process as claimed in claim 13, wherein the phase transfer catalvst is a quaternary ammonium compound.

15. A process as claimed in claim 14, wherein the phase transfer catalyst is a compound of the formula I: R,R2R3R4N+ X- (I) wherein R,, R2, R3 and R4 are alkyl groups each having from 1 to 22 carbon atoms, the total number of carbon atoms in all the R groups being not less than 16, and X- is a monovalent anion or 1/m of an mvalent anion.

1 6. A process as claimed in claim 1 5, wherein the phase transfer catalyst is a compound of the formula I in which at least two of the R groups have at least 4 carbon atoms.

17. A process as claimed in claim 16, wherein the phase transfer catalyst is selected from tetra-noctyl ammonium compounds and tetra-n-butyl ammonium compounds.

1 8. A process as claimed in claim 1 5, wherein the phase transfer catalyst is a compound of the formula I in which R1 and R2, which may be the same or different, are C, to C3 alkyl, and R3 and R4, which may be the same or different are C10 to C22 alkyl.

19. A process as claimed in claim 16, wherein the phase transfer catalyst is selected from di(hydrogenated tallow alkyl) dimethyl ammonium compounds.

20. A process as claimed in any preceding claim, wherein the phase transfer catalyst is used in an amount of from 0.2 to 10 mole % based on the bleaching agent.

21. A process as claimed in claim 20, wherein the phase transfer catalyst is used in an amount of from 0.5% to 4 mole % based on the bleaching agent.

22. A process as claimed in claim 1, carried out substantially as described in any one of Examples 1 to 12 and 13 to 19 herein.

23. A bleached oil or fat whenever produced by a process as claimed in any one of claims 1 to 22.