THEIR PREPARATION

FIELD OF THE INVENTION

[001] The presently described technology relates generally to the sulfonation of alkyl aromatic compounds and mixtures thereof, such as, for example, detergent-range linear alkylbenzenes, wherein the sulfonation is achieved utilizing sulfur trioxide (SO ₃ ) with conversion of aromatic feedstock, preferably high conversion, and with reduced levels of sulfone formation relative to conventional and known processing. More specifically, the presently described technology relates to the use of neutralized salts of sulfonated products of alkylaromatic feedstock as sulfone inhibitors in the SO ₃ sulfonation of the alkylaromatic feedstock. In some preferred embodiments, the feedstock for the preparation of the sulfone inhibitors is the same feedstock that is to be sulfonated in the presence of the sulfone inhibitor.

BACKGROUND OF THE INVENTION

[002] The SO ₃ sulfonation of alkylaromatic feedstocks, for example detergent-range linear alkylbenzenes (LAB), is typically conducted on continuous processing equipment such as falling film reactor units. These reactors provide a means of controlling the intimate contact of feedstock with gaseous SO ₃ diluted in dry air, thereby providing short mass diffusion lengths and rapid heat removal. Such processing also enables high throughput while maintaining product quality. The application of falling film sulfonation to the conversion of alkylaromatic feedstocks into alkylaryl sulfonic acids has been described by W. H. de Groot in Sulphonation Technology in the Detergent Industry, Kluwer Academic Publishers, Dordrecht, The Netherlands: 1991 ; and G. P. Dado, et. al. in Sulfonation and Sulfation, Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed, Wiley-lnterscience, Hoboken, NJ: 2005.

[003] The initial contact of gaseous SO ₃ with alkylaromatic feedstocks results in acid products that are comprised of sulfonic acids, pyro-acids (e.g., transient adducts of sulfonic acids and SO ₃ ), unreacted aromatic feedstock, unsulfonatable feedstock components (e.g., parrafins), sulfuric acid or H ₂ SO ₄ -oleum, sulfonic anhydrides, and sulfones. Sulfonic anhydrides are formed in reactions that are formally the conversion of two moles of LAB plus three moles of SO ₃ to produce one mole of sulfonic anhydride plus one mole of sulfuric acid. Sulfones are formed in reactions that are formally the conversion of two moles of LAB plus two moles of SO ₃ to produce one mole of sulfone plus one mole of sulfuric acid. The initially produced acid derived from a detergent linear alkylbenzene feedstock in a commercial SO ₃ sulfonation process may be comprised of, for example, about 85-92% of sulfonic acid. The higher the level of free oils, including unreacted aromatic feedstock, unsulfonatable components, and sulfones, the more limited the degree of conversion of the alkylaromatic feedstock to sulfonates. Sulfones and other free oil components can impart deleterious effects to the properties and performance of sulfonates by, for example, decreasing viscosities and decreasing formulation stability.

[004] In commercial practice, it is common for an acid aging step to be conducted after the initial contact of SO ₃ with aromatic feedstock. This aging step provides time for the reactions between pyro-acids and oleum with unreacted aromatic feedstock to increase overall conversion to sulfonic acid product. It has been demonstrated that the level of sulfonic anhydrides decrease substantially during acid aging, but that sulfones levels decrease only very minimally. In addition, after acid aging, a small amount of water, for example, about 0.3 to 1 % by weight, is typically added to the acid composition in order to hydrolyze any remaining sulfonic anhydrides to sulfonic acids and to stabilize the product against color degradation. It has been reported that treatment of aged acid with water can, under certain conditions, result in a modest 25% decrease in sulfones. See, e.g.. Moreno, et. al., A contribution to understanding secondary reactions in linear alkylbenzene sulfonation. J. Surf. Del, 2003, 6, 137.

[005] Sulfone generation during the processing of linear alkylbenzene sulfonic acid is known to be promoted by excessive temperature during processing. In addition, the generation of sulfones has been shown under certain conditions to increase as the molar amount of SO ₃ relative to aromatic feedstock approaches and surpasses one equivalent (See Moreno et al., 2003). As a result, the conversion of linear alkylbenzene feedstocks to sulfonic acid products in commercial practice of SO ₃ sulfonation represents a compromise between achieving high conversion of feedstock, sulfone generation, and color development. Typical finished products are comprised of about 95-98% of sulfonic acid, about 0.9-2% of total free oil including sulfone, and about 0.5-1.2% of sulfone.

[006] Because sulfones do not function as "actives" in alkylaryl sulfonates, the generation of these species represents a limit in the degree of conversion that can be realized from alkylaromatic feedstocks. Therefore, it is economically desirable to decrease the amount of sulfone generated while maximizing the conversion of the underlying feedstock. Furthermore, free oils, in general, and sulfones, in particular in alkylaryl sulfonates, can have a significant impact on the physical properties and/or performance of the sulfonates. For example, increasing levels of free oil have been shown to result in decreasing viscosities for 25% by weight solutions of sodium linear alkylbenzene sulfonate. See, e.g., A. Moreno, et. al., Influence of unsulfonated material and its sulfone content on the physical properties of linear alkylbenzene sulfonates, J Am. Oil Chem. Soc. 1988, 65, 1000. Within this same study, it was further shown that increasing levels of sulfones within the free oil fraction of the sulfonates result in increasing solution viscosities.

[007] The successful and economic incorporation of anionic surfactants such as alkylaryl sulfonates into cleaning products such as heavy duty liquid laundry detergents and light duty liquid dish washing detergents is typically influenced by the ability to build viscosity in the formulation so as to meet consumer expectations. A low cost and desirable approach for increasing viscosity, especially in low actives formulations, is by the addition of salts such as magnesium sulfate or sodium chloride. However, the presence of free oils, including sulfones, can have a substantial negative impact on the ability to increase formulation viscosity through the addition of salts. Alkylaryl sulfonates that are manufactured by sulfonation processes utilizing oleum can be produced with low free oil and very low sulfone levels as compared to continuous processing with gaseous SO ₃ . These sulfonates can demonstrate acceptable viscosity increase in economy detergent formulations by the addition of salts, whereas sulfonates produced by commercial SO ₃ sulfonation methods may not demonstrate acceptable viscosity building properties. However, the use of oleum processing to produce alkylaryl sulfonates requires equipment specific to the process and can generate considerable amounts of sulfuric acid by-product that must either be disposed of or recycled back to the oleum supplier. It would be desirable to identify process methods that could enable the production of high viscosity- building alkylaryl sulfonates on standard commercial SO ₃ processing equipment.

[008] Various ways in which the generation of sulfones can be inhibited during the sulfonation of aromatic compounds with SO ₃ are known to one familiar with this technology. For example, inorganic sulfates such as sodium sulfate, carboxylic acids, anhydrides, and peracids can be used to reduce the generation of sulfone in the SO ₃ sulfonation of benzene. See, e.g.. E. E. Gilbert, Sulfonation and Related Reactions, lnterscience Publishers, New York: 1965, pp 69-70, and references therein. Similarly, the use of organic oxygenated compounds such as carboxylic acids, carboxylic anhydrides, percarboxylic acids, carboxylic esters, phosphate esters, ketones, and ethers; and amides are reported to reduce the generation of sulfone in the SO ₃ sulfonation of aryl and short alkyl chain alkylaryl compounds. See, e.g.. U.S. patent 3,829,484. These known approaches to sulfone inhibition are problematic for large scale continuous SO ₃ sulfonation of alkylaromatic feedstocks on falling film reactors for two reasons. First, inhibitors such as sodium sulfate are insoluble in typical alkylaromatic feedstocks suitable for continuous SO ₃ sulfonation, thereby rendering viable processing and needed contact time with conventional equipment difficult or unfeasible. Second, inhibitors such as acetone are highly volatile in the context of continuous SO ₃ sulfonation conditions, resulting in the high potential for excessive "pluming," loss of the inhibitor from the reaction liquid, and possible safety concerns.

[009] There is therefore still an understood need in the art of an unforeseen or unrecognized method for the sulfonation of alkylaromatic feedstocks that can utilize gaseous SO ₃ in standard commercial equipment such as falling film reactors, that can produce a product with substantially reduced total free oil and sulfone content, and that can produce a product that will build acceptable viscosity in low actives economy formulations by the addition of salts.

SUMMARY OF THE INVENTION

[010] The present technology provides in general, one or more methods for preparing alkylaryl sulfonic acid compositions (e.g., alkylaryl sulfonates) by gaseous SO ₃ sulfonation that result in the compositions having reduced total free oils and sulfones compared to such compositions prepared by conventional and known processes. In accordance with such method(s), neutralized salts of sulfonated products of alkyl aromatic feedstock are used as sulfone inhibitors in the SO ₃ sulfonation of the alkylaromatic compounds.

[011] In one aspect, the present technology provides a method for preparing alkylaryl sulfonates by gaseous SO ₃ sulfonation and with reduced total free oils and sulfones comprising the steps of:

a) providing at least one alkylaryl sulfonic acid; b) at least partially neutralizing the sulfonic acid with at least one base to obtain at least one sulfonate salt or a mixture of sulfonate salts and un-neutralized sulfonic acid; c) providing at least one alkylaromatic feedstock; d) dissolving the sulfonate salt or mixture of sulfonate salt and un-neutralized sulfonic acid in the alkylaromatic feedstock to obtain a modified feedstock; and e) sulfonating the modified feedstock with gaseous SO ₃ to obtain a sulfonated reaction product.

[012] In some aspects, step (d) comprises dissolving about 0.01 to about 50 percent by weight of the sulfonate salt or mixture of sulfonate salt and un-neutralized sulfonic acid in the alkylaromatic feedstock to obtain a modified feedstock.

[013] In another aspect, the present technology provides a method for preparing alkylaryl sulfonate by gaseous SO ₃ sulfonation having reduced total free oils and sulfones comprising the steps of:

a) providing at least one alkylaryl sulfonic acid; b) providing at least one alkylaromatic feedstock; c) dissolving the at least one alkylaryl sulfonic acid in the alkylaromatic feedstock; d) at least partially neutralizing the sulfonic acid with at least one base to obtain at least one modified feedstock; e) sulfonating the modified feedstock with gaseous SO ₃ to afford a sulfonated reaction product. [014] In some aspects, step (c) comprises dissolving about 0.01 % to about 50% by weight of the at least one alkylaryl sulfonic acid in the alkylaromatic feedstock.

[015] In another aspect, the present technology provides a method for preparing alkylaryl sulfonate by gaseous SO ₃ sulfonation and with reduced total free oils and sulfones comprising the steps of:

a) providing at least one alkylaromatic feedstock; b) partially sulfonating the feedstock to a conversion of about 0.01 % to about 50% percent to at least one sulfonic acid component; c) at least partially neutralizing the at least one sulfonic acid component of the partially sulfonated feedstock with at least one base to obtain at least one modified feedstock; and d) sulfonating the modified feedstock with gaseous SO ₃ to afford a sulfonated reaction product.

[016] In additional aspects, the present technology provides a method for preparing alkylaryl sulfonic acid compositions, e.g., alkylaryl sulfonates, by gaseous SO ₃ sulfonation and with reduced total free oils and sulfones which comprises the additional step of digesting the mixture of sulfonated reaction product for about 0.5 to about 90 minutes at a temperature of about 25 ^Q C to about 80 ^Q C in order to promote the conversion of sulfonic anhydrides and unreacted alkylaromatic compounds to sulfonic acid.

[017] In additional aspects of the present technology, the described method for preparing alkylaryl sulfonic acid compositions by gaseous SO ₃ sulfonation and with reduced total free oils and sulfones comprises the additional step of treating the digested sulfonated reaction product with about 0.02% to about 2% (wt/wt) of water in order to hydrolyze remaining sulfonic anhydrides and to stabilize the product against color degradation.

DETAILED DESCRIPTION OF THE INVENTION

[018] The alkylaryl sulfonates of the present technology are prepared by sulfonating alkylaromatic compounds by utilizing sulfur trioxide (SO ₃ ) as the sulfonation agent. An important aspect of the presently described technology for sulfonating alkyl aromatic feedstocks in the presence of neutralized sulfonates is the solubility of the neutralized sulfonates in the feedstock. The methods of the present technology utilize mixtures of alkylaromatic feedstocks and sulfonate salts that have low viscosity, are homogeneous and are suitable for processing on commercial continuous SO ₃ sulfonation equipment, for example falling film reactors, with little or no modification to said equipment. In some preferred embodiments of the methods of the present technology, the sulfone inhibitor is comprised of a partially neutralized alkylaryl sulfonic acid, i.e., a mixture of sulfonic acid and sulfonate salts. In one embodiment of the present technology, the sulfone inhibitor is prepared by partially or fully neutralizing an alkylaryl sulfonic acid with a base and then dissolving the obtained product into an alkylaromatic feedstock prior to sulfonation of the feedstock. In another embodiment, the sulfone inhibitor is prepared in situ in an alkylaromatic feedstock prior to sulfonation of the feedstock by dissolving an alkylaryl sulfonic acid in the feedstock and partially or fully neutralizing the acid by addition of a base.

[019] In an alternative embodiment, the sulfone inhibitor may not be fully soluble in the alkylaromatic feedstock but is sufficiently well dispersed so as to afford the desired sulfone inhibition and ability to be processed on standard continuous SO ₃ sulfonation equipment. The sulfone inhibitor may be prepared by partially or fully neutralizing an alkylaryl sulfonic acid with a base and then sufficiently dispersing this obtained product into an alkylaromatic feedstock prior to sulfonation of the feedstock.

[020] In another embodiment, the present technology provides a method for preparing alkylaryl sulfonate by gaseous SO ₃ sulfonation and with reduced total free oils and sulfones. The method includes providing at least one alkylaromatic feedstock and partially sulfonating the feedstock to a conversion of about 0.01 % to about 50% percent of at least one sulfonic acid component. The method further includes at least partially neutralizing the sulfonic acid components of the partially sulfonated feedstock with at least one base to obtain at least one modified feedstock and sulfonating the modified feedstock with gaseous SO ₃ to afford a sulfonated reaction product. [021] The present technology provides a method for preparing alkylaryl sulfonic acid compositions by gaseous SO ₃ sulfonation and with reduced total free oils and sulfones. In one embodiment, the method comprises the steps of providing at least one alkylaryl sulfonic acid and at least partially neutralizing the at least one sulfonic acid with a base to obtain a sulfonate salt or a mixture of sulfonate salt and un-neutralized sulfonic acid. The method further includes the step of providing an alkylaromatic feedstock and dissolving about 0.01 % to about 50% by weight, alternatively about 0.1 % to about 50%, alternatively about 0.5% to about 30%, alternatively about 1 % to about 20% of the sulfonate salt or mixture of sulfonate salt and un-neutralized sulfonic acid in the alkylaromatic feedstock to obtain a modified feedstock. Alternatively, the sulfonate salt or mixture of sulfonate salt and un-neutralized sulfonic acid dissolved can be about 0.01 % to about 40% by weight, alternatively about 0.01 % to about 30%, alternatively about 0.01 % to about 20%, alternatively about 0.01 % to about 10%, alternatively about 0.01 % to about 5%, alternatively 0.1 % to about 40% by weight, alternatively about 0.1 % to about 30%, alternatively about 0.1 % to about 20%, alternatively about 0.1 % to about 10%, alternatively about 0.1 % to about 5%, alternatively about 0.5% to about 50%, alternatively about 0.5% to about 40% by weight, alternatively about 0.5% to about 30%, alternatively about 0.5% to about 20%, alternatively about 0.5% to about 10%, alternatively about 0.5% to about 5 %m alternatively about 1 % to about 50%, alternatively about 1 % to about 40% by weight, alternatively about 1 % to about 30%, alternatively about 1 % to about 25%, alternatively about 1 % to about 20%, alternatively about 1 % to about 10%, alternatively about 1 % to about 5%, 2.5% to about 50%, alternatively about 2.5% to about 40% by weight, alternatively about 2.5% to about 30%, alternatively about 2.5% to about 25%, alternatively about 2.5% to about 20%, alternatively about 2.5% to about 10%, alternatively about 2.5% to about 5%, and can be any percentage in between these values and can be, for example, in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9 or 1.0 % and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). Sulfonating the modified feedstock with gaseous SO ₃ produces a sulfonated reaction product.

[022] In another embodiment, the method of the present technology comprises the steps of providing at least one alkylaryl sulfonic acid and an alkylaromatic feedstock; dissolving about 0.01 % to about 50% by weight, alternatively about 0.1 % to about 50%, alternatively about 0.5% to about 30%, alternatively about 1 % to about 20%, of the at least one alkylaryl sulfonic acid in the alky I aromatic feedstock; and at least partially neutralizing the sulfonic acid with a base to obtain a modified feedstock. Alternatively, the alkylaryl sulfonic acid can be 0.01 % to about 40% by weight, alternatively about 0.01 % to about 30%, alternatively about 0.01 % to about 20%, alternatively about 0.01 % to about 10%, alternatively about 0.01 % to about 5%, alternatively 0.1 % to about 40% by weight, alternatively about 0.1 % to about 30%, alternatively about 0.1 % to about 20%, alternatively about 0.1 % to about 10%, alternatively about 0.1 % to about 5%, alternatively about 0.5% to about 50%, alternatively about 0.5% to about 40% by weight, alternatively about 0.5% to about 30%, alternatively about 0.5% to about 20%, alternatively about 0.5% to about 10%, alternatively about 0.5% to about 5 %m alternatively about 1 % to about 50%, alternatively about 1 % to about 40% by weight, alternatively about 1 % to about 30%, alternatively about 1 % to about 25%, alternatively about 1 % to about 20%, alternatively about 1 % to about 10%, alternatively about 1 % to about 5%, 2.5% to about 50%, alternatively about 2.5% to about 40% by weight, alternatively about 2.5% to about 30%, alternatively about 2.5% to about 25%, alternatively about 2.5% to about 20%, alternatively about 2.5% to about 10%, alternatively about 2.5% to about 5%, and can be any percentage in between these values and can be, for example, in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9 or 1.0 % and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). The modified feedstock is sulfonated with gaseous SO ₃ to obtain a sulfonated reaction product.

[023] In a further embodiment, the method of the present technology comprises steps of providing an alkylaromatic feedstock and partially sulfonating the feedstock to a conversion of about 0.01 % to about 50% by weight, alternatively about 0.1 % to about 50%, alternatively about 0.5% to about 30%, alternatively about 1 % to about 20% of the at least one sulfonic acid component to obtain a partially sulfonated feedstock. Alternatively, the at least one sulfonic acid is converted at 0.01 % to about 40% by weight, alternatively about 0.01 % to about 30%, alternatively about 0.01 % to about 20%, alternatively about 0.01 % to about 10%, alternatively about 0.01 % to about 5%, alternatively 0.1 % to about 40% by weight, alternatively about 0.1 % to about 30%, alternatively about 0.1 % to about 20%, alternatively about 0.1 % to about 10%, alternatively about 0.1 % to about 5%, alternatively about 0.5% to about 50%, alternatively about 0.5% to about 40% by weight, alternatively about 0.5% to about 30%, alternatively about 0.5% to about 20%, alternatively about 0.5% to about 10%, alternatively about 0.5% to about 5 %m alternatively about 1 % to about 50%, alternatively about 1 % to about 40% by weight, alternatively about 1 % to about 30%, alternatively about 1 % to about 25%, alternatively about 1 % to about 20%, alternatively about 1 % to about 10%, alternatively about 1 % to about 5%, 2.5% to about 50%, alternatively about 2.5% to about 40% by weight, alternatively about 2.5% to about 30%, alternatively about 2.5% to about 25%, alternatively about 2.5% to about 20%, alternatively about 2.5% to about 10%, alternatively about 2.5% to about 5%, and can be any percentage in between these values and can be, for example, in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9 or 1.0 % and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). The method further includes the steps of at least partially neutralizing the sulfonic acid components of the partially sulfonated feedstock with a base to obtain a modified feedstock; and sulfonating the modified feedstock with gaseous SO ₃ to afford a sulfonated reaction product.

[024] Alkylaromatic feedstock: Alkylaromatic feedstocks that are suitable for conversion to sulfonic acid-based components by sulfonation with gaseous SO ₃ may be used and are considered within the spirit and scope of the presently described technology and appended claims. For example, alkylbenzene feedstock that may be used to produce alkylbenzene sulfonate compounds which are known in the art can be used in the practice of the present technology. Alkylbenzene sulfonate compounds having varying molecular weights, alkyl chain length and alkyl chain phenyl location combinations may also be employed. Examples of such compounds may be found in, for example, U.S. Pat. No. 6,617,303; U.S. Pat. No. 3,776,962; U.S. Pat. No. 5,152,933; U.S. Pat. No. 5,167,872; Joseph C Drazd and Wilma Gorman, Formulating Characteristics of High and Low 2- Phvnyl Linear Alkylbenzene Sulfonates in Liquid Detergents. JAOCS, 65(3):398-404, March 1988; Sweeney, W. A. and A.C. Olson, Performance of Straight-Chain Alkylbenzene Sulfonate JAOCS, 41 :815-82, Dec. 1964; Drazd, Joseph C, An Introduction to Light Duty (Dishwashing) Liquids Fart I. Raw Materials. Chenlical Times and Trends, 29-58, Jan. 1985; Cohen, L. et al., Influence of 2-Phenyl Alkane and Tetralin Content on Solubility and Viscosity of Linear Alkylbenzene Sulfonate. JAOCS, 72(1 ):1 15-122, 1995; Smith, Dewey L., Impact of Composition on the Performance of Sodium Linear Alkylbenzene-sulfonate (NaLAS). JAOCS, 74(7):837-845, 1997; van Os, N. M. et al., Alkylarenesulphonates: The Effect of Chemical Structure on Physico-chemical Properties. Tenside Surif Del, 29(3):175-189, 1992; Moreno, A. et al., Influence of Structure and Counterions on Phvsicochemical Properties of Linear Alkylbenzene Sulfonates. JAOCS, 67(8);547-552, August 1990; Matheson, K. Lee and Ted P. Matson, Effect of Carbon Chain and Phenyl Isomer Distribution on Use Properties of Linear Alkylbenzene Sulfonate: A Comparison of 'High' and 'Low' 2-Phenyl LAS Homoloαs. JAOCS, 60(9):1693-1698, Sep. 1983; Cox, Michael F. and Dewey L. Smith, Effect of LAB composition on LAS Performance. INFORM, 8(1 ):19-24, Jan. 1997; U.S. Pat. 5,847,254; U.S. Pat. 6,133,217; U.S. Pat. 6,083,897, each of which is incorporated herein by reference. A description of commercial alkylaromatic feedstocks that are particularly suitable for use in the practice of the presently described technology is provided in R. Modler, R. Gubler, and G. Inoguchi, Linear and Branched Alkylbenzenes in Chemical Economics Handbook, SRI Consulting, 2006.

[025] Some preferred alkylaromatic feedstocks are mixtures comprised of compounds of the general structure:

[026] where R and R' are linear or branch saturated alkyl of about 1 to about 21 carbons, R" is H or CH ₃ , and the total number of carbons in R+R'+R" is from about 8 to about 22. These preferred feedstocks may further comprise minor amounts of diphenyl alkanes, tetralins, indanes, naphthalenes, and/or dialkylbenzenes as well as derivatives thereof.

[027] Alkylaryl sulfonic acid: Alkylaryl sulfonic acids that may be obtained from the sulfonation of any of the indicated alkylaromatic feedstocks may be used within the scope of this invention. These alkylaryl sulfonic acids encompass both the sulfonic acids that may be partially or fully neutralized for the purposes of modifying alkylaromatic feedstock for subsequent sulfonation and the sulfonic acid products that result from this subsequent sulfonation. Some preferred alkylaryl sulfonic acids are mixtures comprised of compounds of the general structure:

wherein R and R' are linear or branch saturated alkyl of about 1 to about 21 carbons, R" is H or CH ₃ , and the total number of carbons in R+R'+R" is from about 8 to about 22.

[028] In some embodiments, the alkylaryl sulfonic acid that is to be partially or fully neutralized for the purposes of producing modified feedstock may be prepared by the reaction alkylaromatic feedstocks with sulfonation reagents including but not limited to SO ₃ , oleum, H ₂ SO ₄ , and chlorosulfonic acid. In some preferred embodiments, the alkylaryl sulfonic acid is produced by falling film sulfonation of alkylaromatic feedstock with SO ₃ . In these embodiments, the molar ratio of SO ₃ to alkylaromatic feedstock (degree of sulfonation, DOS) may be from about 0.001 to about 1.10, alternatively from about 0.01 to about 1.05, alternatively from about 0.1 to about 1.05, alternatively from about 0.2 to about 1.05, and can be any numerical value in between these values and can be, for example, in additional increments of, for example, 0.001 , 0.002, 0.0025, 0.005, 0.0075, 0.01 , 0.02, 0.025, 0.05, 0.075, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). In methods in which partially or fully neutralized alkylaryl sulfonic acid is to be produced in a separate step prior to producing a modified feedstock, it is preferable to limit the molar ratio of SO ₃ to alkylaromatic feedstock to a level less than that which, upon neutralization, results in excessive viscosity that renders handling of the material difficult and impractical, for example, viscosity in excess of about 10,000 centipoise (cP), alternatively in excess of about 8,000 centipoise, alternatively in excess of about 5,000 centipoise, alternatively in excess of about 4,000 centipoise, alternatively in excess of about 3,000 centipoise, alternatively in excess of about 2,000 centipoise, alternatively in excess of about 1 ,000 centipoise, alternatively in excess of about 750 centipoise, or alternatively in excess of about 500 centipoise, and can be in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1.0, 2.0, 5.0, 7.5, 10, 20, 25, 30, 40, 50, 100 centipoise and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). [029] In some embodiments of the present technology, thermal aging of the alkylaryl sulfonic acid that is to be partially or fully neutralized for the purposes of producing modified feedstock can be conducted for the purpose of reducing the amount of incidental H ₂ SO ₄ (sulfuric acid) present in the sulfonic acid. This thermal aging may be conducted at a temperature of from about 20 ^Q C to about 100 ^Q C for a time period of from about 1 minute to 24 hours or more. Not to be bound by any particular theory, it is believed that the presence of excessive amounts of H ₂ SO ₄ in the sulfonic acid may be detrimental upon reaction with a base. First, H ₂ SO ₄ reaction with a base is believed to result in insoluble components (e.g., metal hydrogen sulfate salt) that can interfere with material handling and falling film sulfonation of modified feedstock, thereby necessitating filtration, decantation, or another means of removal of insoluble components from the modified feedstock. Secondly, H ₂ SO ₄ is believed to potentially retard the solid-liquid reaction of sulfonic acid with a base under some conditions. In some embodiments, the alkylaryl sulfonic acid that is to be partially or fully neutralized for the purposes of producing modified feedstock comprises less than about 0.75% H ₂ SO ₄ . Thermal aging of partially sulfonated linear alkylbenzene (for example at 0.80 DOS) is believed to result in gradual consumption of H ₂ SO ₄ in the acid to the point that it is no longer detected by titration. Such aged acid reacts completely with solid bases such as sodium carbonate and produces modified feedstocks that are free of particulate salts.

[030] In additional embodiments, the alkylaryl sulfonic acid that is to be partially or fully neutralized for the purposes of producing modified feedstock may be a sulfonic acid that comprises in excess of about 0.75% by weight of H ₂ SO ₄ . In these embodiments, the subsequently obtained partially or fully neutralized sulfonic acid, or alternatively the further subsequently obtained modified feedstock, may be filtered, decanted, or processed by other means to remove insoluble components so as to improve the handling and falling film sulfonation processing of the modified feedstock.

[031] Base: Any Bronstedt or Lewis base that can be reacted with alkylaryl sulfonic acid to produce a partially or fully neutralized alkylaryl sulfonic acid can be used to prepare one or more modified feedstocks of the present technology, provided that the obtained sulfonate salt is soluble in the alkylaromatic feedstock to a degree sufficient to enable, with or without prior removal of insoluble components, sulfonation of the modified feedstock on commercial continuous SO ₃ sulfonation equipment such as a falling film reactor. Alternatively, the obtained sulfonate salt should exhibit about greater than about 0.01 % solubility (wt/wt), alternative greater than about 0.1 % solubility (wt/wt), alternatively greater than about 0.5% solubility (wt/wt), alternatively greater than about 1 % solubility (wt/wt), and can be any value in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9 or 1.0 % and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). Preferably, the base that is used to partially or fully neutralize alkylaryl sulfonic acid for the purposes of producing one or more modified feedstocks is a member of the group consisting of alkali metal, alkaline earth metal, and ammonium or substituted ammonium salts of hydroxide anion, oxide anion, carbonate anion, and hydrogen carbonate anion, including mixtures thereof; ammonia, and substituted amines. Alkali metals include, but are not limited to, lithium, sodium, potassium, cesium and mixtures thereof. Alkali earth metals include, but are not limited to magnesium, calcium, strontium, barium, and mixtures thereof. Substituted ammonium cations include, but are not limited to, monoethanol ammonium, diethanol ammonium, triethanol ammonium, and mixtures thereof. Substituted amines include, but are not limited to, monoethanolamine, diethanolamine, and triethanolamine. Alternatively, the base is a member of the group containing of sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium hydroxide, ammonium carbonate, ammonium hydrogen carbonate, and ammonia. In some preferred embodiments, the base is substantially free of water. In some alternative embodiments, an aqueous base may be used provided that water is removed from the modified feedstock prior to sulfonation to a sulfonated reaction product.

[032] Degree of alkylaryl sulfonic acid neutralization: The molar degree of neutralization of the alkylaryl sulfonic acid that is used to produce one or more modified feedstocks of the present technology may be in the range of about 1 % to about 100 %, alternatively between 1 % and 80%, alternatively between 1 % and about 75%, alternatively between about 1 % and about 50%, alternatively from about 5 % to about 100 %, alternatively between about 10% and 100%, alternatively between about 20% and about 100%, alternatively from about 25 % to about 100 %, alternatively between about 30% and about 100%, alternatively between about 40% and about 100%, alternatively between about 50% and about 100%, alternatively between about 25% and about 80%, and can be any percentages in between these values and can be, for example, in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1.0, 2.0%, or 2.5 % and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). In preferred methods, the degree of neutralization is less than that which causes substantial insolubility of the alkylalkyl sulfonic acid salt or other salts in the modified feedstock. In methods of the present technology in which the partially neutralized alkylaryl sulfonic acid is to be produced in a separate step prior to producing a modified feedstock, it is preferable to limit the degree of neutralization to a level less than that which, upon neutralization, results in excessive viscosity that renders handling of the material difficult and impractical, for example, viscosity in excess of about 10,000 centipoise, alternatively in excess of about 2000 centipoise, alternatively in excess of about 1 ,000 centipoise, alternatively in excess of about 500 centipoise and can be in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1.0, 2.0, 5.0, 7.5, 10, 20, 25, 30, 40, 50 centipoise and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc).

[033] Amount of partially or fully neutralized alkylaryl sulfonic acid in alkylaromatic feedstock: The amount of partially or fully neutralized alkylaryl sulfonic acid that is used to produce one or more modified feedstocks of the present technology can be any amount that can enable the desired amount of sulfone inhibition during the sulfonation of the modified feedstock, provided that the modified feedstock, prepared either with or without a step to remove insoluble components, is sufficiently free of solid particulate matter greater than about 50 micrometers in diameter, has a low in viscosity, preferably from about 0.5 centipoise to about 400 centipoise, alternatively from about 1 centipoise to about 200 centipoise, alternatively from about 1 centipoise to about 50 centipoise, and can be in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1.0, 2.0, 5.0, 7.5, 10, 20, 25, 30, 40, 50 centipoise and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc) and is otherwise suitable for processing on continuous gaseous SO ₃ sulfonation equipment. This amount may be from about 0.01 % to about 50% of the total weight of the modified feedstock, alternatively from about 0.01 % to about 30%, alternatively from about 0.01 % to about 20%, alternatively from about 0.01 % to about 10%, alternatively from about 0.01 % to about 5%, alternatively from about 0.1 % to about 50%, alternatively from about 0.1 % to about 40%, alternatively from about 0.1 % to about 30%, alternatively from about 0.1 % to about 20%, alternatively from about 0.1 % to about 10%, alternatively from about 0.1 % to about 5%, alternatively from about 0.5% to about 50%, alternatively from about 0.5% to about 40%, alternatively from about 0.5% to about 30%, alternatively from about 0.5% to about 20%, alternatively from about 0.5% to about 10%, alternatively from about 0.5% to about 5%, alternatively from about 1 % to about 50%, alternatively from about 1 % to about 40%, alternatively from about 1 % to about 30%, alternatively from about 1 % to about 20%, alternatively from about 1 % to about 10%, alternatively from about 1 % to about 5%, and can be any percentages in between these values and can be, for example, in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9 or 1.0 % and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc).. Preferably, the modified feedstock is visually free of solid particulate matter or undissolved material, as may be judged by, for example a lack of turbidity.

[034] Alkylaryl Sulfonic Acid Neutralization Reaction Conditions and Preparation of Modified Feedstock: The neutralization of alkylaryl sulfonic acid for the purposes of producing one or more modified feedstocks of the present technology can be conducted in-situ (i.e., within the bulk of the alkylaromatic feedstock that is to be modified), or in a separate step. Depending on the base that is used in the neutralization reaction, heating of the neutralization reaction mixture from about ambient (about 25 ^" C) to about 150 ^° C, alternatively from about 50 ^° C to about 100 ^° C for reaction times from less than about 1 minute to more than about 24 hours or more, alternatively from less than 1 minute to about 10 hours or more, alternatively from about 15 minutes to about 4 hours, alternatively from about 5 seconds to about 1 minute may be used and can be in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1.0, 2.0, 5.0, 7.5, 10, 20, 25, 30, 40, 50 minutes and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). When the neutralization is conducted in-situ in alkylaromatic feedstock, the alkylaromatic sulfonic acid and base may be added sequentially in any order or alternatively these components may be added concurrently. When the neutralization is conducted as a separate step, the partially or fully neutralized alkylaryl sulfonic acid intermediate may be blended with alkylaromatic feedstock in advance or immediately prior to sulfonation of the modified feedstock. The modified feedstock preferably is homogeneous and can be obtained as such through selection of the degree of sulfonation and neutralization of the alkylaryl sulfonic acid, the amount of partially or fully neutralized alkylaryl sulfonic acid that is used, and/or the selection of cation that is used. Alternatively, one or more homogeneous modified feedstocks of the present technology may be obtained by filtration or decantation of the modified feedstock to remove insoluble material such as inorganic sulfate salts or unreacted solid base. Water may be produced in the neutralization of alkylaryl sulfonic acid with base, the amount being dependent on the base that is used. For example, the reactions of metal carbonates with sulfonic acid can, for example, produce about 0.5 moles of water per mole of sulfonic acid that is neutralized. In another example, the reaction of metal or ammonium hydroxides with sulfonic acid can produce, for example, about 1.0 moles of water per mole of sulfonic acid that is neutralized. In another example, the reaction of ammonia with sulfonic acid produces no water. The amount of water that is present in the modified feedstock preferably should be less than the solubility limit of the water in the modified feedstock. Furthermore, the amount of water should be preferably less than that which will negatively impact the subsequent continuous sulfonation of the modified feedstock. Preferably, for example, the amount of water that is present in the modified feedstock is less than about 1 percent (wt/wt), alternatively less than about 0.5 percent, alternatively less than about 0.1 percent. In some methods, for example methods that utilize aqueous base in the neutralization reaction, excess water may be removed from the modified feedstock by any suitable means. One such means, for example, may be the heating of the modified feedstock under vacuum.

[035] Modified Feedstock Sulfonation: The modified feedstock is sulfonated by any means of continuous gaseous SO ₃ sulfonation to produce a sulfonated reaction product, for example, falling film reaction equipment. The amount of SO ₃ that is contacted with the modified feedstock is affected by the amount of sulfonatable alkylaromatic compounds present in the modified feedstock. The molar ratio of SO ₃ to sulfonatable alkylaromatic compounds is from about 0.9 to about 1.2, alternatively about 0.98 to about 1.10, alternatively from about 1.00 to about 1.07, alternatively from about 1.00 to about 1.05 and can be in additional increments of, for example, 0.01 , 0.02, 0.05, 0.1 , 0.2, 0.25, 0.3. Preferably, the amount of SO ₃ that is used is optimized so as to maximize the conversion of sulfonatable alkyl aromatic compounds while not significantly increasing the generation of by-product sulfones.

[036] Acid aging: The sulfonated reaction product produced from continuous SO ₃ sulfonation of modified feedstock may be subjected to an acid aging step for the purposes of improving the conversion of alkylaromatic compounds to sulfonic acid. This aging can be conducted by digesting the mixture of sulfonated reaction product for about 0.5 to about 90 minutes, alternatively for about 1 minute to about 60 minutes, at temperatures of about 25 ^° C to about 80 ^° C, alternatively of about 30 ^° C to about 60 ^° C and can be in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1.0, 2.0, 5.0 ^° C and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). The digestion can be conducted, for example, in a continuous or batch process.

[037] Acid product stabilization: The aged sulfonated reaction product may be treated with water in order to hydrolyze remaining sulfonic anhydrides and to stabilize the product against color degradation. The amount of water that can be used is from about 0.02% to about 2% (wt/wt) relative to the total mass, alternatively from about 0.2% to about 1 %.

[038] The incorporation of neutralized alkylaryl sulfonates into alkylaromatic feedstock enables the sulfonation of the feedstock to very high degrees of conversion while inhibiting sulfone generation. Preferably, the molar conversion of alkylaromatic components in the feedstock to sulfonated products is greater than about 99%, alternatively greater than about 99.5%. The resulting sulfonated products are low in free oil as measured by, for example, petroleum ether extraction of neutralized solutions of product in aqueous alcohol. Preferably, the sulfonated products comprise less than about 1.5 percent (wt/wt) of free oil, alternatively less than about 1.2 percent (wt/wt) of free oil, alternatively less than about 1 percent (wt/wt) of free oil, alternatively less than about 0.8 percent (wt/wt) of free oil. The free oils of sulfonated alkylaromatic feedstocks are typically comprised of mixtures of unsulfonated alkyl aromatics and sulfones. Preferably, the sulfonated products comprise less than about 0.8 percent (wt/wt) of sulfones, alternatively less than about 0.6 percent (wt/wt) of sulfones, alternatively less than about 0.5 percent (wt/wt) of sulfones, alternatively less than about 0.4 percent (wt/wt) of sulfones. The low free oil products that can be obtained by the presently described technology exhibit substantially improved viscosity building properties for the purposes of formulating detergents, cleaning products and the like.

[039] The sulfonated reaction products of the present technology can have utility in any known application of linear alkylbenzene sulfonates, branched alkylbenzene sulfonates, or any other sulfonated alkylaromatics, where the reduction of sulfones and unreacted alkylaromatics is of potential benefit. Such benefits can include increased or reduced formulation viscosity, improved formulation stability, improved compatibility or solubility in formulation or in end-use application, and improved properties or performance attributes such as foaming, wetting, or detergency. In addition, these benefits may be uniquely accessible through this technology if low H ₂ SO ₄ levels, not obtainable through oleum- based sulfonation methods, are important to realizing the benefits.

[040] The incorporation of partially or fully neutralized alkylaryl sulfonic acids into alkylaromatic feedstocks may have additional benefits in addition to the sulfonation of these feedstocks. For example, these partially or fully neutralized alkylaryl sulfonic acids might impact color inhibition during sulfonation to afford products with reduced color. Additionally, these partially or fully neutralized alkylaryl sulfonic acids might reduce the extent of excessive color generation that occurs upon sulfonation of alkylaromatic feedstocks with significant molar excess of SO ₃ . Additionally, these partially or fully neutralized alkylaryl sulfonic acids might reduce the rate of color generation that occurs upon acid aging so that more extensive aging may be feasible, enabling still further reductions in sulfones and unreacted alkylaromatics.

[041] The processes of the presently described technology produce alkylaryl sulfonate compositions that are not obtained from either continuous gaseous SO ₃ sulfonation or oleum sulfonation of alkylaromatic feedstock. The alkylaryl sulfonate compositions are comprised of, for example, sulfonic acid, sulfuric acid, unsulfonatable organics such as paraffins, and sulfones, wherein a portion of the sulfonic acid and/or sulfuric acid is neutralized as a salt. The alkylaryl sulfonate compositions may further comprise unreacted alkylaromatic feedstock. In some embodiments, the alkylaryl sulfonate compositions comprise about 3% or less of sulfuric acid, alternatively 2% or less; less than about 0.8% sulfone, more preferably less than about 0.6% sulfone, alternatively less than about 0.5% sulfone, alternatively less than about 0.4% sulfone; and low amounts of total free oil, preferably less than 1.5%, alternatively less than about 1.2%, alternatively less than 1.0%, alternatively less than 0.8% total free oil and include percentages that can be in additional increments of, for example, 0.1 , 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, or 1.0, % and multiplied factors thereof, (e.g. x1 , x2, x10, x100, etc). .

[042] As a non-limiting example, the formation of alkylaryl sulfonic acid via sulfonation of linear alkylbenzene with SO ₃ can be represented by the following formula:

Sulfonation of linear alkylbenzenes is typically accompanied by the formation of sulfonic anhydrides, which can be represented by the following overall net reaction:

3 SO ₃ ->~ + H ₂ SO ₄

In addition, SO ₃ sulfonation of alkylaromatics is accompanied by the formation of aromatic sulfones, which can be represented by the following overall net reaction:

In the non-limiting example of preparing a partially neutralized alkylbenzene sulfonic acid (sulfone inhibitor) by reaction with sodium carbonate, the net stoichiometric neutralization reaction can be represented by the following reaction scheme:

EXAMPLES Example 1

[043] Samples 1 -4 demonstrate the preparation of partially sulfonated, partially neutralized linear alkylbenzene compositions. These compositions can be subsequently dissolved in alkylaromatic feedstocks to prepare modified feedstocks that are suitable for sulfonation with SO ₃ to create alkylaryl sulfonated products.

[044] A detergent-grade linear alkylbenzene feedstock, available commercially from Deten Quimica S. A. as Deten LAB 240, was used in this example. The mole equivalent weight of the feedstock for the purposes of sulfonation was 240. The feedstock was comprised of about 95% linear alkylbenzenes; about 5% other sulfonatable aromatics including dialkyltetralins, dialkylbenzenes, and diphenylalkanes; and less than about 0.1 % unsulfonatable paraffins. The average alkyl chain length of the feedstock was about Cn ₅ , and the 2-phenyl isomer content of the feedstock was about 15%.

[045] The feedstock was sulfonated in a batch reactor as follows. To an addition funnel was dispensed 58.8 grams (0.734 mole) of liquid SO ₃ (stabilized, Aldrich Chemical Company). The addition funnel was then attached to a flash pot comprised of a three neck round bottom flask equipped with a magnetic stir bar, an N ₂ inlet stream, and a gas outlet line. The flash pot was maintained at about 120-160 ^Q C by use of a heating mantel. Infrared heat lamps were used to prevent the SO ₃ from freezing in or on the tip of the addition funnel. The gas outlet line of the flash pot was attached to a 25 ^Q C water-jacketed glass reactor that was designed to deliver the gas from the flash pot to a liquid feedstock via multiple small pin-holes in the bottom of the reactor. The N ₂ flow rate through the reactor was adjusted to about 5 liters per minute and then 213.4 gram (0.889 moles) of linear alkylbenzene feedstock was then added to the water-jacketed reactor. The liquid SO ₃ was placed slowly into the flash pot so as to maintain the reaction temperature in the reaction vessel below about 55 ^Q C. The total SO ₃ addition time was about 30 minutes. An orange sulfonic acid product was obtained, which was stored at ambient temperature. ¹ H NMR analysis (acetone-d6 solvent, RT) indicated a molar conversion of alkylbenzene to sulfonic acid of 81.2 percent. The viscosity of the sulfonic acid product was 425 centipoise (cP) (25 ^Q C, 10 sec ^"1 shear rate, cone and plate geometry). Analysis of the acid by titration with 0.1 N cyclohexylamine in methanol indicated a sulfonic acid content of 2.550 milliequivalents per gram and negligible (undetectable) sulfuric acid content.

[046] Clear and homogeneous partially neutralized mixtures of sodium alkylbenzene sulfonate and alkylbenzene sulfonic acid were obtained from the prepared sulfonic acid by reaction with bases at 80 ^Q C for 4 to 8 hrs as specified in Table 1.

Table 1.

Example 2

[047] Samples 5-7 demonstrate the preparation of modified feedstocks by dissolution of partially neutralized, partially sulfonated linear alkylbenzenes into linear alkylbenzene feedstock.

[048] In this example, summarized in Table 2, the neutralization reaction products of Samples 2, 3, and 4, referenced as "sulfone inhibitor", were dissolved into Deten LAB 240 linear alkylbenzene feedstock by mixing at ambient temperature to produce clear and homogeneous modified feedstocks that were visually free of solids and that are suitable for sulfonation processing on a falling film reactor.

Table 2.

Example 3.

[049] Sample 8 demonstrates the preparation of a modified feedstock by the in-situ reaction of partially sulfonated linear alkylbenzene and sodium carbonate in linear alkyl benzene feedstock.

[050] To a nitrogen blanketed 250 milliliter reaction flask equipped with overhead mechanical stirrer was added 91.9 grams of Deten LAB 240 linear alkylbenzene, 9.7 grams of partially sulfonated linear alkylbenzene prepared as described in Example 1 , and 0.51 grams of sodium carbonate. With stirring, the reaction mixture was heated to 85 ^Q C for 2 hours to produce a clear and homogeneous modified feedstock, Sample 8, that was free of solids. Qualitatively, the product was of similar viscosity to that of unmodified linear alkylbenzene. Upon storage of Sample 8 for 1 week at ambient temperature (about 25 ^° C), the modified feedstock remained clear, homogeneous, and visually free of solids.

Example 4.

[051] Sample 9 and Comparative Sample A demonstrate the reduction of sulfone generation during the sulfonation of the modified feedstock produced in Example 3 (Sample 8) as compared to the sulfonation of unmodified Deten LAB 240 linear alkylbenzene.

[052] In separate batch reactions, feedstock was sulfonated at 30-40 ^Q C with about 1.03 molar equivalents of gaseous SO ₃ relative to alkylbenzene in the feedstock using a sulfonation method comparable to that described in Example 1. Throughout the gradual addition of SO ₃ , about 1 milliliter aliquots of reaction mixture were pulled from the reactor. These aliquots were digested at 50 ^Q C for 30 minutes and were then analyzed by ¹ H NMR (acetone-d6, RT). The molar conversions of linear alkylbenzene to sulfonated products (sulfonic acid, sulfonic acid anhydride, and sulfone) were calculated from integration data for unreacted linear alkylbenzene (NMR chemical shift of 7.35 to 7.0 parts per million (ppm)) relative to total aromatic protons (about 8.0 ppm to 6.9 ppm). For each sample, the molar conversion of linear alkylbenzene to sulfone was estimated as follows. About 0.5- 0.8 grams of acid sample, 20 milliliter of deionized water, 20 milliliter of ethanol, and 40 milliliter of petroleum ether were added to a flask. After vigorous mixing, the mixture was allowed to stand until two layers had separated. The clear, upper layer of petroleum ether was removed and concentrated by rotatory evaporation to afford an oily extract. This extract was analyzed by ¹ H NMR (acetone d-6, RT). A resolved signal at 7.88 parts per million (ppm) was identified as corresponding to one-half of the protons associated with sulfone, and a resolved signal at 7.79 ppm was identified as corresponding to one-half of the protons associated with sulfonic anhydride. For both of these species, the signals for the other one-half of protons were observed to overlap with proton signals for linear alkylbenzene; the relative molar amount of linear alkylbenzene in the extract was determined by subtracting out the integration values for the resolved sulfone and sulfonic anhydride signals. The relative mole fraction of sulfone to linear alkylbenzene in the extract, in combination with the estimated molar conversion of linear alkylbenzene to sulfonated product, enabled a calculation of the molar conversion of linear alkylbenzene to sulfone.

[053] In Sample 9, the feedstock was the modified feedstock produced in Example 3. In Comparative Sample A, the feedstock was un-modified Deten LAB 240 linear alkylbenzene. Conversion of linear alkylbenzene to sulfone as a function of linear alkylbenzene conversion to sulfonated products is summarized in Table 3. These data demonstrate a substantial reduction in the generation of sulfone in the sulfonation of modified feedstock as compared to un-modified linear alkylbenzene feedstock.

Table 3.

Example 5.

[054] Samples 10-13 and Comparative Sample B demonstrate the preparation of alkylaryl sulfonate compositions by falling film sulfonation of a modified feedstock that was prepared from Deten LAB 240 linear alkylbenzene, and demonstrates the reduced levels of sulfones in the obtained products relative to sulfonic acid produced by commercial falling film sulfonation of un-modified feedstock.

[055] Preparation of Partially Sulfonated Linear Alkylbenzene. Linear alkylbenzene was sulfonated a single-tube falling film reactor at an acid production rate of 84.4 lbs per hour and with a 33 ^Q C cooling water jacket temperature. The SO ₃ to linear alkylbenzene mole ratio was 0.80. Analysis of an acid sample, collected directly off of the falling film reactor, by titration with 0.1 N cyclohexylamine in methanol indicated a total acid content of 2.625 milliequivalents per gram and a sulfuric acid content of 0.65 percent (wt/wt). A total of 153 pounds (lbs) of the continuously produced acid was collected in a 50 gallon reactor equipped with N ₂ headspace sparge.

[056] Preparation of Partially Neutralized. Partially Sulfonated Linear Alkylbenzene. To the 153 lbs of partially sulfonated linear alkylbenzene was added 7.65 lbs of sodium carbonate (granules, anhydrous) with mixing. The reactor was heated with a steam jacket to 93 ^Q C for 9 hours, heating was discontinued, and the reaction mixture was then stirred for an additional 10 hours. The viscous acid product contained a small amount of white solids. Analysis of the product by titration with 0.1 N cyclohexylamine in methanol indicated a total acidity of 1.692 milliequivalents per gram.

[057] Preparation of Modified Feedstock. To a 170 gallon vessel equipped with overhead mechanical stirrer was added 773.7 lbs of Deten LAB 240 linear alkylbenzene and 86.0 lbs of partially neutralized, partially sulfonated linear alkylbenzene. The modified feedstock contained small amounts of white solid granules and very fine crystalline particles. Based on calculation from mole and mass balances, the estimated equivalent weight of linear alkylbenzene in the modified feedstock for the purpose of subsequent sulfonation was 263.3 grams/mole.

[058] Sulfonation of Modified Feedstock. The modified feedstock was sulfonated at several mole ratios of SO ₃ to linear alkylbenzene on a single-tube falling film reactor at an acid production rate of about 85 lbs per hour. Modified feedstock was pumped from the 170 gallon stirred vessel and through a 30 micron filter prior to metering into the falling film reactor. Crude sulfonation product exiting the falling film reactor was digested in a continuous flow reactor. The residence time of the acid in the flow reactor was about 27 minutes and the outlet temperature was about 49 ^Q C. Acid collected from the flow reactor was treated with 0.6 % water (wt/wt acid) in order to hydrolyze sulfonic anhydrides and to stabilize the product. The obtained sulfonate compositions were analyzed for free oil by petroleum ether extractions of approximately 10 gram samples that were dissolved in 50/50 (vol/vol) water/ethanol and neutralized to phenolphthalein endpoint with sodium hydroxide. Following recovery of the extracted oils by rotary evaporation, the mass of free oil obtained allowed for a calculation of free oil as a weight percentage of the sulfonic acid product. The sulfone content of the sulfonate compositions was determined by ¹ H NMR spectroscopy (CDCI ₃ solvent, RT) of the obtained free oils, using isopropyl myristate as an internal standard, and calculating the mass of sulfone based on molar integration of sulfone ¹ H signals at 7.84 ppm relative to molar integration of isopropyl myristate ¹ H signal at about 5.0 ppm. Table 4 summarizes Samples 1 1 -13 and compares the results of these Samples to the analysis results for alkylbenzene sulfonic acid produced from un-modified Deten LAB 240 linear alkylbenzene on a commercial falling film reactor of comparable design to the pilot plant reactor (Comparative Sample B). From the data in Table 4, it is concluded that falling film sulfonation of the modified feedstock affords a sulfonated alkylbenzene composition with reduced sulfones at high conversions of linear alkylbenzene as compared to optimized commercial conversion of un-modified feedstock by falling film sulfonation.

Table 4.

Example 6.

[059] Sample 14 and Comparative Sample C demonstrate the improved ability to build viscosity in water by the addition of MgSO ₄ for sodium linear alkylbenzene sulfonate prepared from the sulfonic acid product obtained in Example 5 (Sample 13), as compared to sodium sulfonate prepared from Comparative Sample B.

[060] Sodium sulfonate stock solutions of pH 7 were prepared by neutralization of sulfonic acid in water by the addition of 50% aqueous NaOH. These stock solutions were used to prepare diluted solutions containing 6.0 wt% sulfonate actives (sodium sulfonate equivalent weight of 342 grams/mole) and varying amounts of MgSO ₄ . The viscosities of these solutions were measured at 25 ^Q C on a TA Instruments AR2000 rheometer using concentric cylinders geometry at 10 sec ^"1 shear rate; results are summarized in Table 5. The data indicate that at equivalent actives concentration, the sodium alkylbenzene sulfonate produced from modified feedstock builds higher viscosity by the addition of MgSO ₄ than can be achieved with sulfonate produced by falling film sulfonation from unmodified feedstock.

Table 5.

Example 7.

[061] Samples 15-20 demonstrate the effect of sulfuric acid in alkylaromatic sulfonic acid on the reaction of the sulfonic acid with solid sodium carbonate. Partially sulfonated linear alkylbenzene was produced via falling film sulfonation at a ratio of 0.80 mole of SO ₃ per mole of linear alkylbenzene as described in Example 5. Acid collected directly off of the sulfonation equipment, which contained about 0.65 percent (wt/wt) H ₂ SO ₄ , was stored in a closed glass jar and allowed to stand at room temperature for two days. Analysis of the acid by titration with 0.1 N cyclohexylamine in methanol indicated a total acidity of 2.539 milliequivalents per gram and negligible (undetectable) sulfuric acid content. This acid was then modified by the addition of varying amounts of 99% sulfuric acid. The obtained modified acid samples were analyzed for total acid content by titration with 0.1 N cyclohexylamine in methanol and were then reacted with 5 weight percent on a (modified) acid basis of solid sodium carbonate in reaction vials at 90 ^Q C, vigorously shaking and venting the vials every 5 minutes. After 1 hour of reaction, unreacted sodium carbonate was allowed to float to the liquid surfaces and the samples were allowed to cool to room temperature. The presence or absence of very fine particulate insoluble salts in the lower acid layer was evaluated on the basis visual observation of turbidity or a substantial lack thereof. Aliquots of the lower sulfonic acid layers were analyzed by titration with 0.1 N cyclohexylamine in methanol to determine the extent of neutralization reaction. Results are summarized in Table 6. These results demonstrate that for Deten LAB 240 linear alkylbenzene sulfonated at a 0.8 degree of sulfonation, the presence of H ₂ SO ₄ at levels greater than -0.5-0.75 percent lead to the generation of insoluble salts, as is evidenced by acid product turbidity. The results further demonstrate that under these conditions, the presence of H ₂ SO ₄ does not result in a significant loss in reactivity in the solid-liquid reaction relative to neutralization of sulfonic acid that is free of detectable H ₂ SO ₄ , as is evidenced by the lack of significant changes in the extents of neutralization reaction.

Table 6.

Example 8.

[062] Sample 21 demonstrates the utility of ammonia gas in the preparation of partially neutralized, partially sulfonated linear alkylbenzene. [063] Partially sulfonated linear alkylbenzene was produced via falling film sulfonation at a ratio of 0.80 mole of SO ₃ per mole of linear alkylbenzene as described in Example 1. Analysis of the acid by titration with 0.1 N cyclohexylamine in methanol indicated a sulfonic acid content of 2.628 milliequivalents per gram and negligible (undetectable) sulfuric acid content. To a nitrogen blanketed 250 milliliter reaction flask equipped with overhead mechanical stirrer was added 72 grams of the partially sulfonated linear alkylbenzene. With stirring, ammonia gas was bubbled into the sulfonic acid mixture until the sulfonic acid content was reduced to about 1.62 milliequivalents per gram. The obtained product (Sample 21 ) was free flowing, clear and free of solids.

Example 9.

[064] Sample 22 demonstrates the sulfonation of a modified feedstock produced from Deten LAB 240 and the product of Example 8 (Sample 21 ).

[065] A modified feedstock was prepared by dissolving Sample 21 into Deten LAB 240 at a 1 :9 ratio (wt/wt). This feedstock was then batch sulfonated as described in Example 4. At 98.7 mole percent conversion of LAB, the conversion of LAB to sulfone was found to be 0.25 mole percent.

Example 10.

[066] Samples 23 and 24 demonstrate the preparation of modified feedstocks from Deten LAB 240 and a partially neutralized product that was derived from commercial alkylbenzene sulfonic acid.

[067] To a nitrogen blanketed 250 milliliter reaction flask equipped with overhead mechanical stirrer was added about 48.7 grams of Deten LAB 240, about 4.0 grams of sodium carbonate, and about 48.7 grams of commercial Cn ₈ alkylbenzene sulfonic acid comprising about 97% sulfonic acid, about 1.3% sulfuric acid, and about 0.3% water. With stirring, the reaction mixture was heated to 85 ^Q C for 2 hours to produce a hazy, low viscosity product that contained very fine particulate material. A portion of the partially neutralized product was filtered to produce a liquid that was free of visual turbidity. Dissolution of the filtered liquid into Deten LAB 240 at a 1 :9 ratio afforded a modified feedstock (Sample 23). Another portion of the partially neutralized product was allowed to stand at ambient temperature for 24 hours to afford a sample wherein the particulate material had fully settled to the bottom of the container. A clear liquid was decanted from this sample and this liquid was dissolved into Deten LAB 240 at a 1 :19 ratio to afford a second modified feedstock (Sample 24).

Example 11.

[068] Samples 25-27 demonstrate the sulfonation of Deten LAB 240 linear alkylbenzene feedstock modified with varying amounts of partially neutralized, partially sulfonated linear alkylbenzene.

[069] In this example, modified feedstocks were prepared by dissolving a partially neutralized, partially sulfonated linear alkylbenzene composition that was comparable to Sample 2 of Example 1 , referenced as "sulfone inhibitor", into Deten LAB 240 linear alkylbenzene. The modified feedstocks were batch sulfonated and the sulfonic acid products were analyzed as described in Example 4. Sample analysis results are summarized in Table 7. These results indicate that relative to Comparative Sample A of Example 4, even low levels of partially neutralized, partially sulfonated linear alkybenzene are effective in reducing the amount of sulfone generated during the sulfonation of LAB.

Table 7.

[070] The present technology is now described in such full, clear and concise terms as to enable a person skilled in the art to which it pertains, to practice the same. It is to be understood that the foregoing describes preferred embodiments of the present technology and that modifications may be made therein without departing from the spirit or scope of the present technology as set forth in the appended claims. Further the examples are provided to not be exhaustive but illustrative of several embodiments that fall within the scope of the claims.