A PROCESS FOR THE PREPARATION OF INTERNAL OLEFIN SULPHONATES

Abstract: The invention relates to a process for the preparation of internal olefin sulphonates which comprises reacting in a film reactor an internal olefin having from 8 to 26 carbon atoms with a sulphonating agent, in a mol ratio of sulphonating agent to internal olefin of 1:1 to 1.25:1 while cooling the reactor with a cooling means having a temperature not exceeding 35 °C, and allowing to neutralize and hydrolyze the reaction product of the sulphonating step and further to internal olefin sulphonates which have a high content of beta-hydroxy sulphonates compared with the usually described products.

Description: The invention relates to a process for the preparation of internal olefin sulphonates and to internal olefin sulphonates as novel products. It is generally known that internal olefins are more difficult to sulfonate than alpha-olefins (see "Tenside Detergents" 22 (1985) 4, pp 193-195). In the article, entitled "Why internal olefins are difficult to sulphonate", the authors state that by the sulfonation of various commercial and laboratory-produced internal olefins, using falling film reactors, internal olefins gave conversions of below 90% and further they state that it was found necessary to raise the SO₃ : internal olefin mol ratio to over 1.6:1 in order to achieve conversions above 95%; furthermore the resulting products were very dark in colour and had high levels of di- and polysulphonated products. In the US Patent Specifications 4,183,867 and 4,248,793 are disclosed processes, carried out in a falling film reactor, for the preparation of light-colored internal olefin sulphonates, however the amounts of unreacted internal olefins are still between 10 and 20 per cent and at least 20 per cent respectively in the disclosed processes and special measures must be taken to remove the unreacted internal olefins. The internal olefin sulphonates containing between 10 and 20 per cent and at least 20 per cent of unreacted internal olefins (also called free oil) must be purified before being used. Consequently the preparation of internal olefin sulphonates having the desired light colour and with the desired low free oil content offers substantial difficulties. It is an object of the invention to prepare internal olefin sulphonates with a low free oil content, with a light colour and avoiding the purification step. Applicant has now found a process for the preparation of internal olefin sulphonates which comprises reacting in a film reactor an internal olefin having from 8 to 26 carbon atoms with a sulphonating agent, in a mol ratio of sulphonating agent to internal olefin of 1:1 to 1.25:1 while cooling the reactor with a cooling means having a temperature not exceeding 35 °C, and directly neutralizing the obtained reaction product of the sulphonating step and, without extracting the unreacted internal olefin, hydrolyzing the neutralized reaction product. The invention furthermore relates to the internal olefin sulphonates having from 8 to 26 carbon atoms characterized by containing at least 10% by weight of beta-hydroxy sulphonates, preferably at least 25% by weight of beta-hydroxy sulphonates, more preferably at least 50% by weight of beta-hydroxy sulphonates. Especially preferred are internal olefin sulphonates having from 50 to 90% by weight of beta-hydroxy sulphonates, even more preferred are internal olefin sulphonates having from 60 to 85% by weight of beta-hydroxy sulphonates. In the preparation of sulphonates derived from internal olefins, the internal olefins are reacted with a sulphonating agent, preferably sulphur trioxide, with the formation of beta-sultones and some alkene sulphonic acids. The reaction products are neutralized and hydrolyzed. Under certain circumstances, for instance ageing the beta-sultones are converted into gamma-sultones, which on their turn may be converted into delta-sultones. After neutralization and hydrolysis the gamma-hydroxy sulphonates and delta-hydroxy sulphonates are obtained respectively. A disadvantage of the gamma-and delta-sultones is that they are more difficult to hydrolyze than beta-sultones. An advantage of the beta-sultones is that hydrolysis proceeds easier than with gamma- and delta-sultones. The beta-sultones, after hydrolysis, give beta-hydroxy sulphonates. The internal olefin sulphonates containing more then 10% by weight of beta-hydroxy sulphonates are novel products. The internal olefins used as starting material in the present invention are those having 8 to 26 carbon atoms, preferably 13 to 22 carbon atoms. Examples of the internal olefins are those having the general formula wherein each of the groups R₁, R₂, R₃ and R₄ independently are linear or branched alkyl groups or hydrogen and the total number of carbon atoms of R₁, R₂, R₃ and R₄ is from 6 to 24, with the proviso that at least one of R₁ and R₂ and one of R₃ and R₄ is an alkyl group. The sulphonation of the internal olefins is preferably carried out with sulphur trioxide in a film reactor. Preferred is the falling film reactor. The cooling means, which is preferably water, has a temperature not exceeding 35 °C, especially a temperature in the range of from 0 °C to 25 °C. Depending upon the circumstances lower temperatures may be used as well. In the process according to the invention it is preferred that the reaction mixture from the film reactor is not aged during a long time. The reaction mixture may be aged during a short period, but better is to age not at all, since then the highest percentage of beta-hydroxy sulphonates may be obtained. For that purpose the reaction mixture is led to a neutralization hydrolysis unit. The neutralization/hydrolysis is carried out with a water soluble base, such as sodium hydroxide or sodium carbonate. Also the corresponding bases derived from potassium or ammonium are suitable. The neutralization of the reaction product from the falling film reactor is generally carried out with excess of base, calculated on the acid component. Generally neutralization is carried out at a temperature in the range of from 0 °C to 80 °C. Hydrolysis may be carried out at a temperature in the range of from 100 °C to 250 °C, preferably 130 °C to 200 °C. The hydrolysis time generally may be from 5 min to 4 hours. Alkaline hydrolysis may be carried out with hydroxides, carbonates or bicarbonates of (earth) alkali metals. As has already been explained above the beta-sultone of an internal olefin is converted in the process according to the invention into beta-hydroxy sulphonate according to the equation. wherein R₁, R₂, R₃ and R₄ have the above significance. It has been found that the amount of beta-hydroxy sulphonate is dependent on the amount of beta-sultone. Under the rather mild reaction circumstances the beta-sultones are readily formed and since the slow-ageing step is generally avoided, gamma- and delta-sultones are formed only to a minor extent. The process according to our invention may be carried out batchwise, semi-continuously or continuously. The reaction is generally performed in a falling film reactor which is cooled by flowing a cooling means at the outside walls of the reactor. At the inner walls of the reactor the internal olefin flows in downward direction. SO₃ is diluted with a stream of nitrogen, air or any other inert gas into the reactor. The concentration of SO₃ generally lies between 2 and 4 per cent by volume on the volume of the carrier gas. In the preparation of internal olefin sulphonates, derived from olefins with more than 14 carbon atoms, it is required that in the neutralization/hydrolysis very intimate mixing of the reactor product and the aqueous base is achieved. This can be done by e.g. efficient stirring, the addition of a polar cosolvent (lower alcohol) or a phase-transfer agent. The general analytical procedures are given in the footnotes of the Table. More details of the procedures used can be found in "Technical Bulletin Shell Chemical Company" SC-181-77, entitled "Alpha olefin sulphonates analysis procedures", May 1976. The following examples illustrate the invention. EXAMPLE 1-7 The sulphonation of a mixture of C₁₃₋₁₄-internal olefins was carried out in a stainless steel reactor, having a diameter of 0.9 cm and a length of 2 m. The sulphur trioxide was prepared by reacting sulphur dioxide with oxygen (dry air) over a vanadium pentoxide catalyst at about 450 °C. The reactor was cooled by flowing water of low temperature along the outside of the stainless steel reactor tube. The C₁₃₋₁₄-internal olefins flowed along the inner part of the reactor walls as a flowing film in downward direction and they reacted with the sulphur trioxide. The reaction product was subsequently conducted to a stainless steel autoclave, equipped with a magnetical stirrer, and which autoclave had been charged with an aqueous sodium hydroxide solution. The mixture was well stirred in the autoclave. The autoclave was then closed and heated to the desired temperature and kept at that temperature for the desired period of time. Subsequently the autoclave was cooled to ambient temperature and the contents were analyzed by appropriate means. The cooling water, cooling the reactor, had an inlet temperature of 8 °C and an outlet temperature of 13 °C, flowing countercurrently with the feed/SO₃ stream. Hydrolysis took place during 1 h at 160 °C with 20% molar excess of NaOH (calculated on product as out of the reactor) to obtain active material in an almost quantitative yield. In example 5 the cooling water had an inlet temperature of 10 °C and an outlet temperature of 15 °C, while in examples 6 and 7 the inlet temperature was 12 °C and the outlet temperature 17 °C. In example 5 hydrolysis took place at 140 °C during 1 h. The free oil content, the Na₂SO₄ content and the residual sultones content are calculated on amount of active material. In example 7 after the sulphonation, but before neutralization/hydrolysis, the product was aged during 30 min at 30 °C. In the following Table the results are shown. EXAMPLE 8 The sulphonation of C₁₈-internal olefin was performed in a glass reactor, having a diameter of 0.5 cm and a length of 1 m. The sulphonation reaction was performed in the same way as described in the previous examples under the following conditions: cooling water temperature 15 °C SO₃/feed ratio, mol/mol 1,2 SO₃ in N₂, % vol. 3 feed rate, mol/h 1.5 neutralization, NaOH on acid product, mol/mol 1.4 hydrolysis time, h, 1 hydrolysis temp., °C, 160 The neutralization and hydrolysis were carried out with NaOH in a water/ethanol solution (vol/vol, 75:25). The product contained 1.6% by weight of free oil and 2.4% by weight of Na₂SO₄ (calculated on amount of active material). 80% by mol of the product was identified as beta-hydroxy sulphonate. EXAMPLE 9 The sulphonation of C₁₈-internal olefin was carried out under the same conditions as disclosed in example 8. The neutralization and hydrolysis (1h at 160 °C) were carried out with an aqueous sodium hydroxide solution in the presence of an amount of C₁₃₋₁₄-internal olefin sulphonate (10% by weight on acid intake). The product contained 7.9% by weight of free oil and 3.9% by weight of Na₂SO₄. The product had a colour index of 200 (according to Klett). EXAMPLE 10 The sulphonation of C₁₈-internal olefin was carried out under the same conditions as disclosed in example 8. The neutralization and hydrolysis (1 h at 160 °C) were carried out with an aqueous sodium hydroxide solution under vigorous stirring of the obtained mixture. The product contained 7.4% by weight of free oil and 5.4% by weight of Na₂SO₄. The product had a colour index of 140 (according to Klett). EXAMPLE 11 The sulphonation of C₁₈-internal olefin was carried out under the same conditions as disclosed in example 8. The neutralization and hydrolysis (1 h at 160 °C) were carried out with an aqueous sodium hydroxide solution in the presence of an amount of DOBANOL 91-10 (5% by weight on acid intake). DOBANOL 91-10 is an alcohol mixture of primary, linear C₉, C₁₀, and C₁₁ alcohols (weight ratio: 18/50/32) that is ethoxylated to an averaged ethylene oxide number of 10. The product contained 5.5% by weight of free oil and 4.8% by weight of Na₂SO₄. EXAMPLE 12 The sulphonation of C₁₈-internal olefin was carried out under the same conditions as disclosed in example 8. The neutralization and hydrolysis (1 h at 160 °C) were carried out with an aqueous sodium hydroxide solution under vigorous stirring and, at the same time, in the presence of an amount of DOBANOL 91-10 (5% by weight on acid intake). The product contained 3.1% by weight of free oil and 4.6% by weight of Na₂SO₄. EXAMPLE 13 The sulphonation of C₁₃₋₁₄-internal olefins was carried out in the reactor as described in example 8. The sulphonation reaction was performed under the following conditions: cooling water temperature, °C 15 SO₃/feed ratio, mol/mol 1.1 SO₃ in N₂, % vol. 2.8 feed rate, mol/h 1.5 neutralization, NaOH on acid product, mol/mol 1.2 hydrolysis time, h 1 hydrolysis temp., °C 160 The product contained 2.1% by weight of free oil and 2.4% by weight of Na₂SO₄. The product ( not bleached) had a colour index of 90 (according to Klett). EXAMPLE 14 Sulphonation The sulphonation of an internal olefin mixture containing internal olefins in the C₁₅-C₁₉ range (≦ C₁₄ 2%; C₁₅ 25%; C₁₆ 26%; C₁₇ 24%; C₁₈ 18%; ≧ C₂₀ 5% by weight; purity: ca. 98%; remaining 2%: paraffins) was carried out under the same sulphonation conditions as disclosed in example 8. Continuous neutralization The acid product mixture from the falling film sulphonation reactor was directly pumped continuously into a continuously stirred tank reactor (CSTR) near and at the level of the 6-(flat-)bladed impeller (diameter: 35 mm). At the same time aqueous caustic (1.2 eg as calculated on acid intake) was also continuously pumped into the CSTR near and at the same level of the impeller. The volume of the CSTR was kept at 500 ml by siphoning off the product at the top of the reactor. Operated in this way the average residence time in the CSTR amounted ca. 20 min. The CSTR was maintained at 30 °C by external cooling/heating whilst the impeller speed was 750 rotations per minute, 1000 rotations per minute and 1500 rotations per minute respectively; in the set-up described the power input due to stirring amounted to ca. 1.2-9.7 kW/m³. In this range the analytical data of the products obtained were independent of the power input. The continuous neutralization was started up with the CSTR filled with C₁₅₋₁₉ internal olefin sulphonates with the following analytical data active matter, AM (%w) : 26-31 free oil (%w on AM) : 6-10 inorganic sulphate (%w on AM) : 3-8 that was obtained from experiments without an aging step between the sulphonation and neutralization step, and containing 70-90% of beta-hydroxysulphonates. By starting up and operating the neutralization reactor continuously in this way, the product formed itself acts as an in situ generated emulsifier. Hydrolysis After the start of the continuous neutralization, samples were taken from the product stream only after waiting for at least 1 hour (i.e. after three residence times) and such samples were hydrolyzed batch-wise for 1 hour at 160 °C. The product contained 6.7% by weight of free oil (of this 6.7%, however, ca. 2% is paraffins; therefore, the actual free oil content calculated on 100% olefin is 4.7% by weight) and 4.9% by weight of Na₂SO₄, calculated on active matter basis as indicated above. The product (not bleached) had a colour index of 500 (according to Klett). Approx. 85% by mol of the product was identified as beta-hydroxysulphonate.

Claims: A process for the preparation of internal olefin sulphonates which comprises reacting in a film reactor an internal olefin having from 8 to 26 carbon atoms with a sulphonating agent, in a mol ratio of sulphonating agent to internal olefin of 1:1 to 1.25:1 while cooling the reactor with a cooling means having a temperature not exceeding 35 °C, and directly neutralizing the obtained reaction product of the sulphonating step and, without extracting the unreacted internal olefin, hydrolyzing the neutralized reaction product. A process as claimed in claim 1, wherein the cooling means is water having a temperature in the range of from 0 °C to 25 °C. A process as claimed in claims 1-2, wherein the sulphonating agent is sulphur trioxide. A process as claimed in one or more of the claims 1-3, wherein the internal olefin comprises from 13 to 22 carbon atoms. A process as claimed in one or more of the claims 1-4, wherein the process is carried out in such a manner that an ageing step is omitted at all. A process as claimed in one or more of the claims 1-5, wherein the reaction is performed in a falling film reactor. A process as claimed in one or more of the claims 1-6, wherein during neutralization/hydrolysis the reaction product of the sulphonating step is intimately mixed with an aqueous base solution. A process as claimed in claim 7 wherein the mixing is effected by stirring, by the addition of a co-solvent or by the addition of a phase-transfer agent. Internal olefin sulphonates having from 8 to 26 carbon atoms characterized in that these internal olefin sulphonates comprise at least 10% by wt of beta-hydroxy sulphonates, on the weight of the total sulphonates. Internal olefin sulphonates as claimed in claim 9, characterized by at least 25% by wt of beta-hydroxy sulphonates. Internal olefin sulphonates as claimed in claim 10, characterized by at least 50% by wt of beta-hydroxy sulphonates. Internal olefin sulphonates as claimed in claim 11, characterized by 50 to 90% by wt of beta-hydroxy sulphonates. Internal olefin sulphonates as claimed in claim 12, characterized by 60 to 85% by wt of beta-hydroxy sulphonates. Internal olefin sulphonates as claimed in one or more of the claims 9-13, characterized in that these internal olefin sulphonates contain an amount of unsaturated sulphonate. Internal olefin sulphonates as claimed in one or more of the claims 9-14, wherein the sulphonates are (earth) alkali metal sulphonates or ammonium sulphonates. Internal olefin sulphonates as claimed in claim 15, wherein the sulphonates are sodium or potassium sulphonates.

Inventors: STAPERSMA, JOHAN, VAN GINKEL, ROELOF
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1989
Main classification: C07C303
IPC codes: C07C303, C07C309