GB1585030A - Preparation of salts of secondary monoalkyl sulphuric acids - Google Patents

Description

(54) PREPARATION OF SALTS OF SECONDARY MONOALKYL SULPHURIC ACIDS (71) We, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V., a Company organised under the laws of the Netherlands, of 30 Carel van Bylandtlaan, The Hague, The Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention is concerned with a process for preparing salts of secondary monoalkyl sulphuric acids (MAS) and with the salts so prepared.

MAS, in particular the sodium salts of secondary C8 to C22 monoalkyl sulphuric acids, are well known products which are useful as detergents, and processes for the preparation thereof are described in our co-pending Applications Nos. 49832/76 (Serial No 150001) and 49831/76 (Serial No 1553386). Such processes usually comprise sulphating one or more C8 to C22 olefins, neutralizing the sulphation reaction product and extracting the non-surface active material from the neutralization reaction product.

The Applicants have now found a new improved process for the preparation of MAS.

According to the present invention, a process for preparing salts of secondary monoalkyl sulphuric acids comprises.

(a) sulphating, in a sulphation zone one or more C8 to C22 olefins with sulfuric acid to form a sulphation reaction product; (b) neutralizing, in a neutralization zone, the sulphation reaction product with an aqueous base to form a neutralization reaction product; (c) extracting the neutralization reaction product to form an extractant/non-surface active material extract and an extractant/water/salts of secondary monoalkyl sulphuric acids raffinate; (d) concentrating the raffinate by adding thereto a base to form an extractant/water/ salts of secondary monoalkyl sulphuric acids concentrated raffinate phase and an aqueous base phase; and (e) separating the phases and recycling the aqueous base phase to the neutralization reaction zone.

The reaction condition used in the sulphation reaction may vary between wide limits.

Suitable reaction temperatures are from -20"C to 50"C, preferably from 0 C to 40"C, and suitable residence times are from a few minutes to several hours e.g. from 2 minutes to 10 hours, preferably from 5 minutes to 3 hours. The sulphuric acid used in the process of the present invention may be of any suitable concentration e.g. from 75 to 100%, preferably from 78 to 88%w. Usually an excess of sulphuric acid, on olefin, is used. Suitable amounts are from 1.5 to 8 moles per mole of olefin. The sulphation reaction is preferably carried out in the presence of at least 15% mole, on olefin, of one or more added secondary C8 to C22 alcohols as described in co-pending Application No. 49832/76 (Serial No. 1550001).

After the sulphation reaction, the sulphation reaction product may be de-acidified, before it is neutralized, to remove therefrom unconverted sulphuric acid. The method of de-acidification depends i.a. upon the concentration of the sulphuric acid used in the sulphation reaction. Generally, if sulphuric acid of fairly low concentration, e.g. of below 90%w, is used then the sulphation reaction product readily forms an organic phase and an aqueous sulphuric acid phase from which the latter may be separated. Any sulphuric acid which is still present in the organic phase may then be extracted therefrom by the addition of small amounts of water thereto or be neutralized during the neutralization reaction. The first separated aqueous sulphuric acid phase and the second separated aqueous sulphuric acid phase, if any, and after concentration, if necessary, may be reused in the sulphation reaction. However, if sulphuric acid of fairly high concentration, e.g. of at least 90 %w, then the sulphation reaction product may be de-acidified by adding water, in one or more stages, thereto to form one or more separable aqueous sulphuric acid phases which may also be re-used as described above. As an alternative, or as an additional step, to de-acidification any unreacted sulphur acid in the sulphation reaction product may be removed by de-salting which is the removal of the acid in the form of its inorganic salt as hereinafter described.

The sulphation reaction product, optionally after de-acidification, is then neutralized, in a neutralization zone, to convert the secondary monolkyl sulphuric acids present therein into MAS. Suitably the sulphation reaction product is neutralized by adding thereto aqueous solutions of bases such as amines; or ammonium, alkali metal or alkaline earth metal hydroxides, carbonates or bicarbonates. Alkali-metal hydroxides, in particular sodium hydroxide, are the preferred bases. The amount of base added clearly depends on whether or not the sulphation reaction product has been de-acidified and, if so, to what extent. The aqueous base is at least in part, preferably in whole, that aqueous base phase separated in step(e) as described above. Suitable amounts of base are from 5 to 100 %w on olefins used in the sulphation reaction, of 0.5 to 50%w aqueous solution. In addition to secondary monoalkyl sulphur acids, secondary dialkyl sulphates (DAS) are also formed during the sulphation reaction and it is advantageous that the neutralization of the sulphation reaction product is carried out under conditions such that the DAS present therein is hydrolysed. Suitably a neutralization reaction temperature of from 50 to 1000C and a neutralization reaction time of from 0.5 to 2.0 hours are used. It is possible to neutralize MAS at a lower temperature in which case it is desirable to heat the neutralization reaction product to a higher temperature in order to hydrolyse any DAS present; sufficient base being added to neutralize the acids formed by such hydrolysis.

As explained above the neutralization reaction product may be de-salted before it is extracted. De-salting may be carried out in addition to, or instead of, the de-acidification step referred to above. De-salting results in removal of unconverted sulphuric acid in the form of an inorganic salt e.g. Na2SO4 or an ammonium or amine salt thereof. This may be achieved by treating the neutralization reaction product with various solvents such as lower alcohols e.g. IPA, C4 to C10 ketones and C1 toC6 alkyl acetates at elevated temperature e.g.

at a temperature of from 60 to 100"C. Preferred solvents are IPA, methylisobutyl ketone and ethylacetate. Such salts may then be removed, at least in part, as an aqueous salt phase.

The neutralization reaction product, optionally but preferably after de-salting as described above is then extracted to remove any non-surface active material therefrom.

Such non-surface active material may include secondary alcohols e.g. those added to the sulphation reaction and/or those formed by DAS hydrolysis, olefins, paraffins and various by-products such as polymers. Such non-surface active material is sometimes also referred to an unconverted organic matter.

Preferred extractants are C4 to C10 ketones, in particular C6 ketones such as methylisobutyl ketone and certain acetates, namely Cl to C6 alkyl acetates, in particular methyl, ethyl and isopropyl acetates. Preferably such extractants are used as the sole extractant for the extraction of the non-surface active material. Such extractants are described in our co-pending Application 49831/76 (Serial No 1553386). However, other solvents e.g. lower alcohols, such as alcohol/hydrocarbon mixtures may also be used. If a de-salting step is carried out as described above then preferably the extractant used is the same solvent as is used in the de-salting step.

As a result of the extraction step, the neutralization reaction product is separated into an extract comprising an extractant/non-surface active material extract and an extractant/ water/MAS raffinate. In order to obtain good separation of the product into the desired extract and raffinate phases, especially in the case of the above preferred extractants it is preferred that the product comprises at least 200 %w, more preferably from 300 to 1,000 %w of water based on weight of MAS in the product. Suitable products comprise non-surface active material and MAS in weight ratio of from 1:10 to 10:1 e.g. from 0.25 to 2.5. The products may also comprise inorganic salts e.g. alkali, alkaline-earth or ammonium sulphates in variable amounts. The amount of such salts may be from 0.5 to 100 %w. based on the weight of MAS, but is usually from 1 to 20 %w.

Suitably the neutralization reaction product is contacted, especially insofar as the above preferred solvents are concerned, preferably in counterflow, with from 20 to 500 %w, preferably from 75 to 200 %w of extractant based on the weight of the product. It is important, especially insofar as the use of certain solvents e.g. methylisobutyl ketone is concerned, to carry out the extraction at an appropriate temperature and dilution, since at high temperatures, high concentrations of the MAS and high concentrations of inorganic salts there is an increasing tendency for the methylisobutyl ketone to dissolve both the MAS and the non-surface active material with necessitates a further extraction step to extract the MAS from the non-surface active matter. Suitably the extraction is carried out at a temperature of below 60"C with a neutralization reaction product comprising from 300 to 1,000 %w of water and from 5 to 20 %w of inorganic salt based on the weight of MAS.

Preferably the extraction is carried out at a temperature of below 60"C, more preferably at a temperature of from 30 to 500C. Since it is difficult to separate completely the MAS from the non-surface active material without using a very high number of theoretical extraction stages the raffinate may contain small amounts, usually less than 5 %w, of non-surface active material based on the weight of MAS.

The extract thus obtained may, if desired, be separated into an extractant fraction and a non-surface active material fraction; the former may, where appropriate be recycled to the desalting and/or extraction step and the latter may be recycled to the sulphation reaction zone.

The raffinate thus obtained is concentrated (step(e)) by adding thereto a base of the type described above for the neutralization step. The base may be added as a solid or as an aqueous solution. The amount of base added is preferably that amount which forms an aqueous base phase containing sufficient base to neutralize the sulphation reaction product in step (b) i.e. that amount of base required to neutralize the sulphation reaction product in step (b) together with any base which remains in the concentrated raffinate phase.

However, lesser amounts of base may be added in which case it is necessary to add further amounts of base in step (b). The concentration temperature is suitably at least 600C, preferably of from 70" to 100"C. Under these conditions two phases are readily formed and lower aqueous base phase, which also contains most of the inorganic salt, may be withdrawn and recycled to the neutralization reation zone. The remaining extractant/water/ MAS phase contains less water than the raffinate phase obtained in the extraction step and may be considered to be a concentrated raffinate phase. This phase may be used as such as a detergent but usually the remaining amount of extractant together with some water may be removed e.g. by distillation or evaporation to form a final product comprising from 30 to 60 %w MAS. The concentrated raffinate may also comprise a small amount of the base used in the concentration step which may be neutralized, if desired, with an organic acid. The extractant removed may, where appropriate, be recycled to the de-salting and/or extraction step.

The invention will now be illustrated by reference to the following Example.

Example To a sulphation reaction zone was continuously fed a feedstock comprising C16/Cl8 (1:1 w) olefins 840 g C16/C18 (1:1 w) secondary alcohols 560 g sulphuric acid (84.6 %w) 2647 g The sulphation reaction temperature was 18"C and the residence time was 120 minutes.

The sulphation reaction product was then de-acidified by allowing it to settle and drawing off the lower aqueous phase (2146 g of 82 %w sulphuric acid) which was recycled to the sulphation reaction zone.

The de-acidified sulphation reaction product which had the following composition CL6/C18 olefins 120 g C16/C18 secondary alcohols 526 g C16/C18 sec. alkyl sulphuric acid 894 g di-Cl6/C,8 sec. alkyl sulphate 76 g sulphuric acid 207 g water 20 g was neutralized in a neutralization reaction zone by the addition thereto of an aqueous base comprising.

sodium hydroxide 281 g water 4604 g sodium sulphate 59 g The neutralization reaction temperature was 80 to 85"C and the residence time was 90 minutes.

The neutralization reaction product was then de-salted at a temperature of 80"C by the addition thereto of methylisobutyl ketone (2503 g) which resulted in the formation of a lower aqueous layer containing water (2907 g) and sodium sulphate (286 g) which was withdrawn.

The desalted product comprising CldC18 olefins 120 g C16/C18 alcohols 560 g sodium salt of C16/C18 secon dary alkyl sulphuric acid 1000 g sodium sulphate 73 g water 1841 g methylisobutyl ketone 2503 g was then diluted with water (3659 g) and extracted with methylisobutyl ketone (8396 g) at a temperature of 40"C.

The extract obtained comprised C16/C18 olefins (120 g), C16/C18 secondary alcohols (560 g) and methylisobutyl ketone (8396 g). The olefins and alcohols may be recovered by distilling-off the MIBK and, if desired, be recycled to the sulphation reaction zone; the MIBK may br recycled to the de-salting and/or the extraction zone.

The raffinate obtained comprised the sodium salt of C16/C18 sec. alkyl sulphuric acid (1000 g), sodium sulphate (73 g), water (5500 g) and MIBK (2503 g).

The raffinate was then concentrated at 80"C by the addition thereto of 654 g of a 46 %w aqueous solution of sodium hydroxide which resulted in the formation of a lower aqueous layer comprising water (4604 g), sodium hydroxide (281 g) and sodium sulphate (59 g) which was separated and recycled to the neutralization zone.

The concentrated layer, which comprised the sodium salt of C16/C18 sec. alkyl sulphuric acid (1000 g), sodium sulphate (14 g), water (1249 g), MIBK (2503 g) and sodium hydroxide (20 g), was then evaporated to remove all of the MIBK and 790 g of the water. The thus removed MIBK may if desired by recycled to the de-salting and/or the extraction step.

WHAT WE CLAIM IS: 1. A process for preparing salts of secondary monoalkyl sulphuric acids comprising (a) sulphating, in a sulphation reaction zone, one or more C8 to C22 olefins with sulphuric acid to form a sulphation reaction product; (b) neutralizing, in a neutralization zone, the sulphation reaction product with an aqueous base to form a neutralization reaction product; (c) extracting the neutralization reaction product to form an extractant/non-surface active material extract and an extractant/water/salts of secondary monalkyl sulphuric acid raffinate; (d) concentrating the raffinate by adding thereto a base to form an extractant/water/ salts of secondary monoalkyl sulphuric acids concentrated raffinate phase and an aqueous base phase; and (e) separating the phases and recycling the aqueous base phase to the neutralization reaction zone.

2. A process as claimed in claim 1, wherein the sulphation reaction temperature is from 0 C to 400C.

3. A process as claimed in claim 1 or claim 2, wherein sulphuric acid of from 78 to 88 %w concentration is used.

4. A process as claimed in any one of claims 1 to 3, wherein the sulphation reaction is carried out in the presence of at least 15% mole, on the olefin, of one or more added secondary C8 to C alcohols.

5. A process as claimed in any one of claims 1 to 4, wherein the sulphation reaction

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. sodium hydroxide 281 g water 4604 g sodium sulphate 59 g The neutralization reaction temperature was 80 to 85"C and the residence time was 90 minutes. The neutralization reaction product was then de-salted at a temperature of 80"C by the addition thereto of methylisobutyl ketone (2503 g) which resulted in the formation of a lower aqueous layer containing water (2907 g) and sodium sulphate (286 g) which was withdrawn. The desalted product comprising CldC18 olefins 120 g C16/C18 alcohols 560 g sodium salt of C16/C18 secon dary alkyl sulphuric acid 1000 g sodium sulphate 73 g water 1841 g methylisobutyl ketone 2503 g was then diluted with water (3659 g) and extracted with methylisobutyl ketone (8396 g) at a temperature of 40"C. The extract obtained comprised C16/C18 olefins (120 g), C16/C18 secondary alcohols (560 g) and methylisobutyl ketone (8396 g). The olefins and alcohols may be recovered by distilling-off the MIBK and, if desired, be recycled to the sulphation reaction zone; the MIBK may br recycled to the de-salting and/or the extraction zone. The raffinate obtained comprised the sodium salt of C16/C18 sec. alkyl sulphuric acid (1000 g), sodium sulphate (73 g), water (5500 g) and MIBK (2503 g). The raffinate was then concentrated at 80"C by the addition thereto of 654 g of a 46 %w aqueous solution of sodium hydroxide which resulted in the formation of a lower aqueous layer comprising water (4604 g), sodium hydroxide (281 g) and sodium sulphate (59 g) which was separated and recycled to the neutralization zone. The concentrated layer, which comprised the sodium salt of C16/C18 sec. alkyl sulphuric acid (1000 g), sodium sulphate (14 g), water (1249 g), MIBK (2503 g) and sodium hydroxide (20 g), was then evaporated to remove all of the MIBK and 790 g of the water. The thus removed MIBK may if desired by recycled to the de-salting and/or the extraction step. WHAT WE CLAIM IS:

1. A process for preparing salts of secondary monoalkyl sulphuric acids comprising (a) sulphating, in a sulphation reaction zone, one or more C8 to C22 olefins with sulphuric acid to form a sulphation reaction product; (b) neutralizing, in a neutralization zone, the sulphation reaction product with an aqueous base to form a neutralization reaction product; (c) extracting the neutralization reaction product to form an extractant/non-surface active material extract and an extractant/water/salts of secondary monalkyl sulphuric acid raffinate; (d) concentrating the raffinate by adding thereto a base to form an extractant/water/ salts of secondary monoalkyl sulphuric acids concentrated raffinate phase and an aqueous base phase; and (e) separating the phases and recycling the aqueous base phase to the neutralization reaction zone.

2. A process as claimed in claim 1, wherein the sulphation reaction temperature is from 0 C to 400C.

3. A process as claimed in claim 1 or claim 2, wherein sulphuric acid of from 78 to 88 %w concentration is used.

4. A process as claimed in any one of claims 1 to 3, wherein the sulphation reaction is carried out in the presence of at least 15% mole, on the olefin, of one or more added secondary C8 to C alcohols.

5. A process as claimed in any one of claims 1 to 4, wherein the sulphation reaction

product is de-acidified before it is neutralized.

6. A process as claimed in any one of claims 1 to 5, wherein the sulphation reaction product is neutralized with an aqueous alkali-metal hydroxide.

7. A process as claimed in any one of claims 1 to 6, wherein the neutralization reaction temperature is from 50"C to 1000C.

8. A process as claimed in any one of claims 1 to 7, wherein the neutralization reaction product is desalted before it is extracted.

9. A process as claimed in claim 8, wherein the neutralization reaction product is desalted by treatment with a C4 to C10 ketone at a temperature of from 60"C to 1000C before it is extracted.

10. A process as claimed in any one of claims 1 to 9, wherein the neutralization reaction product which is extracted comprises at least 200 %w of water based on the weight of the salts of secondary monoalkyl sulphuric acids.

11. A process as claimed in any one of claims 1 to 10, wherein the neutralization reaction product is extracted with a C4 to C10 ketone at a temperature of below 60"C.

12. A process as claimed in any one of claims 1 to 11, wherein the extractant/ non-surface active material extract obtained in step (c) is separated and the non-surface active material recycled to the sulphation reaction zone.

13. A process as claimed in any one of claims 1 to 12, wherein the amount of base added to concentrate the extractant/water/salts of secondary monoalkyl sulphuric acids raffinate is the amount which forms an aqueous base phase containing sufficient base to neutralize the sulphation reaction product in step (b).

14. A process as claimed in any one of claims 1 to 13, wherein the concentration temperature is at least 60"C.

15. A process as claimed in any one of claims 1 to 14, wherein the extractant and optionally some water is removed from the concentrated raffinate phase obtained in step (d).

16. A process as claimed in claim 1, substantially as hereinbefore described with particular reference to the Example.

17. Salts of secondary monoalkyl sulphuric acids raffinate whenever obtained by a process as claimed in any one of claims 1 to 16.