BACKGROUND OF THE INVENTION Field of the Invention:

The present invention relates to linear alkylbenzene sulfonic acid compositions and methods for preparing such compositions having low color. It also relates to neutralized linear alkylbenzene sulfonic acid compositions, i.e., linear alkylbenzene sulfonates and methods for preparing such compositions having low color.

Description of the Related Art

Known methods for preparing linear alkylbenzene sulfonic acids or sulfonates involve sulfonation of a linear alkylbenzene starting material to produce a sulfonic acid intermediate shown m Scheme I below

Scheme I : The Sulfonation of Linear Alkylbenzene

Sulfonating agent

wnereiπ R is typically C]_-22 linear cr brancneα aikyi. The linear alkylbenzene sulfonic acid is subsequently optionally bleached and/or neutralized.

Conventional methods for preparing the starting linear alkylbenzene material typically involve a Friedel-Crafts alkylation of benzene with a chloroparaffin, n-paraffin or olefin in the presence of a suitable catalyst. More speci ically, traditional methods have typically involved the use of chloroparaffins to alkylate benzene in the presence cf

an aluminum trichloride catalyst. This methodology, in addition to producing the desired alkylbenzene product, yields a variety of byproducts. Among these byproducts are branched alkylbenzenes (also known as 2-phenyl isomers), dialkylbenzenes, diphenylalkanes, alkyl indanes, alkyl tetralines and alkylated poly-aromatics, such as naphthalene and anthracene derivatives. Also, trace amounts of organochlorides and aluminum trichloride catalyst residues may be present . Modern methods for preparing the starting linear alkylbenzene typically involve a Friedel-Crafts alkylation of benzene with an olefin or n-paraffin in the presence of a suitable catalyst; modern methods omit the usage of chloroparaffins . More specifically, modern methods typically involve the use of n-paraffms or olefins to alkylate benzene in the presence of an aluminum trichloride catalyst cr the use of n-paraffms or olefins to alkylate benzene in the presence of a hydrogen fluoride (HF) cr other catalyst sucr. a solid zeolite-oaseα catalyst. These metnoαoioαies produce the αesireα alkylbenzene product m hign overa-1 conversion v-itr signif cantly less formation of the previously mentioned byproducts .

Conventional sulfonation processes involve reaction of the linear alkylbenzene with a sulfatmg agent, e.g., SO3, SO2-SO3, oleum, or H2SO4, etc., to produce the desired sulfonic acid.

To achieve maximum conversion of the linear alkylbenzene starting material to the desired sulfonic acid, at least a 1:1 ratio of sulfonating agent to alkylbenzene is required. However, sulfonation of a linear alkylbenzene starting material

derived from benzene and chloroparaffins with such an amount of sulfonating agent typically yields linear alkylbenzene sulfonic acids products having high, unsuitable amounts of color, as compared to sulfonation of a linear alkylbenzene starting material derived from benzene and n-paraffins or olefins.

To address these problems a variety of bleaching methods have been αeveloped. These methods have typically involved contacting a linear alkylbenzene sulfonic acid product with a bleaching agent such as hydrogen peroxide or the like. Alkylbenzene sulfonic acids, derived from chloroparaffins and benzene, which nave been treated with hydrogen peroxide, are describee in U.S. Patent No. 2,806,055, U.S. Patent No. 2,827,484, U.S. Patent No. 2,858,276 and U.S. Patent No. 3,997,575. While reducing the color in a sulfonic acid product derived from a linear alkylbenzene prepared from chloroparaffin sources, sulfonic acid products of sufficiently low color to satisfy commercial demands r.ave not ceer. rea.;:eα. In a d on, si i ican color reduction .r. . ΓJ1:;Γ.:; _CIo product derived from a linear i yloer.zer.e source, _r. w.-i cr. a sufficient excess cf sulfonating aαer.t is ise _.α. creater thar. 1:1 ratio of sulfonating agent tc linear alkylbenzene; sucπ that no un-reacted linear alkylbenzene remains to satisfy commercial demands has not been realized. Finally, significant color reduction in a sulfonic acid product derived from a linear alkylbenzene source, in which the sulfonation reaction to produce such a sulfonic acid product is carried out at a reaction rate of one and one-half to four times that taught in the art of sulfonation, has not been realized. In summary,

there exists a need for a method capable of providing very low colored sulfonic acid products in high yields.

When treating a linear alkylbenzene with a sulfonating agent according to traditional methods, a typical molar ratio of sulfonating agent to linear alkylbenzene is from about 1.00:1.00 to about 1.04:1.00. A more preferred range of sulfonating agent to linear alkylbenzene is from about 1.01:1.00 to 1.02:1.00. A slight excess of sulfonating agent is generally believed to be necessary to drive the reaction to completion, i.e. to obtain a high level of conversion of linear alkylbenzene to linear alkylbenzene sulfonic acid.

Conventional methods for maximizing the conversion of linear alkylbenzene to linear alkylbenzene sulfonic acid typically include: (1) increasing the molar ratio of sulfonating agent to linear alkylbenzene, < 2 ι providing an aging step for the sulfonic acid product after tne sulfonation reaction has taxen place. Eacn of these retrocs r.as cee round to nave α ceieteric s effect e s_.lfor.-_- J:.J __c_, _.e. the color of the sulfonic acid pro uc: ιncre__s__- __5 --ac o: tnese metnoos is employee. Usually a comoma o*. _: tnese retnoos _s employed. As the ratio of sulfonating reagent to linear alKylbenzene increases, the color of the sulfonic acid product increases. Aging of linear alkylbenzene sulfonic acid typically involves heating the acid to a temperature of about 40-60°C for a period of time of about 2-20 minutes. As the aging process at any elevated temperature for any reasonable period of time is employed, tne color of the sulfonic acid product increases.

SUMMARY OF THE INVENTION

Processes for preparing linear alkylbenzene have been developed that avoid the use of chloroparaffins, but instead use olefins or n-paraffins as the source of the alkyl group. Such processes involve Friedel-Crafts alkylation of benzene with an olefin in the presence of a suitable HF or solid catalyst. These processes produce alkylbenzene having greatly decreased amounts of undesirable byproducts.

It has been surprisingly discovered that sulfonation of alkylbenzenes produced by a reaction between an olefin or n- paraffin and benzene followed by suosequent treatment with a protic reagent and hydrogen peroxide produces linear alkylbenzene sulfonic acids having greatly decreased color, i.e., the amount of color reduction is suostantial, with formation of colorless sulfonic acids in some cases.

Accordingly, the invention provides processes for preparing linear alkylbenzene sulfonic ac αs. T e retr.co comprises treating _α linear alr-.ylcer.:er.'- _Λ _t:. _ z__. : ::._: ir.d agent to yield a sulfonation product. The -.near ai.-.y.cer.zer.e utilized is produced by a reaction cetweer. o.efir. or paraffin and Denzene. The resulting linear alkylbenzene sulfonic acid is contacted with a protic reagent ano hydrogen peroxide. The contacting is typically for a time and temperature sufficient to produce a linear alkylbenzene sulfonic acid having a greatly reduced color. Sulfonation products prepared according the inventive method typically have Klett colors less than 15. In certain embodiments of the inventive method, the sulfonation products have Klett colors less than about 2.

^■ o-

The invention further provides sulfonation products that are neutralized to provide a salt of the sulfonic acid (i.e. a sulfonate) .

It has been discovered that neutralizing a sulfonic acid product previously bleached with hydrogen peroxide provides an unexpected amount of Klett color reduction to the final sulfonate product. Thus, the invention also encompasses a process for reducing the Klett color in a linear alkylbenzene sulfonic acid product that has previously been treated with a protic reagent and hydrogen peroxide, the process comprising contacting a sulfonic acid product with a neutralizing agent.

Further, the invention encompasses a process for reducing the Klett color in a linear alkylbenzene sulfonate product that has previously been treated with a protic reagent, hydrogen peroxide, and a neutralizing agent, the process comprising contacting a sulfonate product with a reducing aαent, such as sodium hypochlorite, to produce a sulfonate with a additional unexpected amount cf Klett color reduction.

The invention furtner provides sulfonic acid compositions comprising from aoout 55 percent to

99 percent by weight linear alkylbenzene sulfonic acid ana about 0.5 percent to 15 percent by weight water. Water is present in such compositions to destroy undesirable sulfonic acid anhydrides which are formed during the sulfonation process. Water is also present in such compositions to provide color stability to the sulfonic acid products.

The invention further provides linear alkylbenzene sulfonic acid compositions comprising from about 85 percent to 99 percent by weight linear alkylbenzene sulfonic acid and

about 0.5 percent to 15 percent by weight water and preferably about 0.01 to about 0.5 percent by weight un-reacted linear alkylbenzene.

In a more preferred embodiment, the invention further provides linear alkylbenzene sulfonic acid compositions comprising from about 85 percent to 99 percent by weight linear alkylbenzene sulfonic acid and about 0.5 percent to 15 percent by weight water and preferably about 0.01 to about 0.2 percent by weight un-reacted linear alkylbenzene. The invention further provides linear alkylbenzene sulfonic acid compositions prepared by rapid sulfonation conditions. When employing continuous falling film sulfonation, irrigation rates above 45 are considered rapid to one skilled in the art. Standard irrigation rates from about 30 to 45 are common for continuous falling film sulfonation. The standard definition of irrigation rate "I.R." ^V for falling

I.R. = pounos AB/hour per tuoe P X D

wnere LAB is linear alkylbenzene, P is 3.14, and D is the tube diameter of the falling film reactor. Irrigation rate is independent of tube length or the number of tubes in a reactor. The compositions sulfonated under rapid conditions comprise from about 85 percent to 99 percent by weight linear alkylbenzene sulfonic acid and about 0.5 percent to 15 percent by weight water and preferably about 0.01 to about 0.5 percent by weight un-reacted linear alkylbenzene.

In a more preferred embodiment, the invention further provides linear alkylbenzene sulfonic acid compositions prepared by rapid sulfonation conditions. These compositions comprise from about 85 percent to 99 percent by weight linear alkylbenzene sulfonic acid and about 0.5 percent to 15 percent by weight water and preferably about 0.01 to about 0.2 percent by weight un-reacted linear alkylbenzene.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, linear alkylbenzene (LAB) means an alkylbenzene having a straight or branched chain alkyl group of from about 8 to 22 carbon atoms. Linear alkylbenzene sulfonic acid or sulfonate (LAS) means an alkylbenzene sulfonic acid or sulfonate having a straight or branched chain alkyl group of from about 8 to 22 carbon atoms.

Klett color is defined by the equation (1000) (D)/2, where

D is the optical density of the material Deing measured at a given concentration. The Klett color of the sulfonic acids and sulfonates described herein are measured at a 5 weignt percent concentration in water.

The present invention provides methods for preparing linear alkylbenzene sulfonic acid and salts of these acids. Surprisingly, the methods result in linear alkylbenzene sulfonic acid and salt products having substantially reduceα amounts of color and/cr substantially reduced cr non-existent amounts of un-reacted i.e. un-sulfonatedι ..near alkvlbenzene.

The present invention also provides metnoos for preoarinα sue. .inear alkylbenzene sulfonic aciαs and sulfonates at greatly increased rates.

Accordingly, the present invention encompasses processes for preparing linear alkylbenzene sulfonic acids (I) and linear alkylbenzene sulfonates (II) of the formulas

(I) (II) where R represents branched or straight chain alkyl having i-22 carbon atoms; and

M represents an alkali metal, ammonium, or organic ammonium cation, or mixtures thereof.

In general terms, the present invention is depicted in

Scheme II below:

Scheme II

Sulfonating Agent

\\ Protic Reagent/

Hydrogen

Peroxide

("very light") ("light")

wherein dark colored acid is defined as material having a Klett color of greater than 30; light colored material is defined as having a Klett colcr of from about 10 to about 30; and very

.1αn . mate a. s r.av ιa a r. ett co or of rcm aoou aDOut

Linear Alkvlbenzene

The starting linear alkylbenzenes to be sulfonated according to the present invention are encompassed by the following formula:

where R represents branched or straight chain alkyl having 8-22 carbon atoms.

The starting linear alkylbenzene for use in this invention is preferably derived from the reaction of benzene and n- paraffins and/or olefins in the presence of a Friedel Crafts alkylation catalyst, such as hydrogen fluoride or aluminum chloride.

Sulfonation

In general, sulfonation of linear alkylbenzene starting material with a sulfonating agent in accordance with the principles of the invention is accomplished by treating the linear alkylbenzene starting material with a sulfonating agent. The sulfonating agent may be liquid or gaseous. Preferably, the starting linear alkylbenzene is m the liquid pnase. The treatment step typically occurs at a temperature from about 0°C to about 90°C and somewhat more preferably from about 25°C to about 50°C.

Various sulfonating agents are suitac., ::r use .r. tne invention. Representative suifonat:r.. _ er.t_ r.r.ude, :or example, 503, Ξθ2~SC3, H2SG , oieur : ;__t ;r. : su.rur tπoxioe m concentrated sulfuric acid , r-C _^ -C, ≤u.rarr.io ac d, trial ylamine-sulfur complexes, alkyiaryl sulfonate-sulfur trioxice complexes and mixtures thereof. Sulfur trioxide (SO3) is a preferred sulfonating agent because of its vigorous reactivity. Sulfur trioxide also produces less byproducts than other sulfonating agents.

It has been unexpectedly found that a linear alkylbenzene sulfonic acid, which is essentially free of un-reacted, i.e. un-sulfonated linear alkylbenzene, can be produced by employing a molar ratio of sulfonating agent to linear alkylbenzene of

greater than about 1.04:1.00, in combination with an aging step at an elevated temperature.

It has been also found than a linear alkylbenzene sulfonic acid which is essentially free of un-reacted linear alkylbenzene can be produced by employing a molar ratio of sulfonating agent to linear alkylbenzene of about 1.1:1.0 without the need of an aging step.

Typically, a sulfonation reaction is relatively fast and quite exothermic. Accordingly, care must be taken to avoid over-sulfonation in localized areas (i.e. charring) to adequately control the exotherm and to insure good contact between the reactants. Suitable methods of treating the linear alkylbenzene starting material with a sulfonating reagent include continuous agitation (batch sulfonation) methods, or oy contacting a gas stream containing the sulfonating agent against a moving surface film (continuous falling film sulfonation) of linear alkylbenzene under turbulent conditions wnereby the various molecules are vigcrous v stirred or intermixed within the reaction mass. Both cater and continuous -netnoos of sulfonation require that the exterior walls c: tne reaction vessel be cooled, for example, with a heat-exchange medium, providing a heat sink for the exothermic reaction conditions.

When employing continuous sulfonation, a relatively rapid addition of sulfonating agent, for example, SO3 in air, is desirable. One type of sulfonation which allows for such a rapid addition of sulfonating agent is falling film sulfonation. When practicing falling film sulfonation, SO3 is normally introduced in a pressurized gas stream as a gas in a

gas (i.e., SO2, air, nitrogen or other relatively inert gas) in a so-called falling film reactor. Thus, in falling film sulfonation, the linear alkylbenzene is formed into a relatively thin film traveling down the interior walls of a tube reactor with the gas stream contacting thereon. Alternatively, a so-called wiped film reactor may be utilized so that a relatively thin film of linear alkylbenzene is contacted by the gas stream, mechanically wiped from the reactor walls at the area of contact and re-oeposited downstream on freshly cooled reactor walls.

When employing continuous falling film sulfonation of linear alkylbenzene under turbulent conditions, tne color quality and composition of the linear alkylbenzene sulfonic acid product is effected by the rate of sulfonation and the control of the resulting exotherm, i.e. the efficiency of the heat sink provided. Irrigation rates from aoout 30 to 45 are common. When irrigation rates aoove 4: are emclcveo, tne color quality of tne linear alkylbenzene _ulfor.ιo _cιc crcαuct normally is degraded, as it is very ciffic-.t to crevice tne necessary heat sink to counter act the increase ir. exotnerr of tne reaction at such high irrigation rates. Sulfonation at high irrigation rates is not typically practiced since such irrigation rates produce linear alkylbenzene sulfonic acid with unacceptable color. However, the need for an aging step can be omitted at high irrigation rates because the extreme exotherm in the reactor provides the necessary temperature for a sufficient period of time to maximize the conversion of linear alkylbenzene to linear alkylbenzene sulfonic acid.

It has been found than linear alkylbenzene sulfonic acids can be produced by employing irrigation rates of 45-100; irrigation rates of greater than 100 are also possible. It has also been found than a linear alkylbenzene sulfonic acid, which is essentially free of un-reacted, i.e., un-sulfonated linear alkylbenzene can be produced by employing a molar ratio of sulfonating agent to linear alkylbenzene, of greater than 1.04:1.00, in combination with the high irrigation rates described above. An aging step for this process is often not required.

In batch mode sulfonation embodiments, a solvent may optionally oe present during the treating step to both reduce the viscosity of the reaction mixture and to function as another heat sink for the reaction. Presently, preferred solvents are sulfur dioxide, αioxane, dimethyl formamiαe, C_j to C20 hydrocarbons, nitroparaffins, acetomtriie, chlcroalkyls, carDoxylic acids, straight or crancned a ..ary. s-_.fonate compounds, naving 1 to 16 aικy. car e _:cr_ , ^* c._er.e, ourre e, xyiene, olefins, paraffins, ana mixtures tneree:. ..lt e _^ t cemo couna by any particular theory, tne ::_ve".:: _::._ zeα may reduce tne viscosity of the reactants/reaction products ana are liquid under reaction conditions. Some solvents sucn as, for example, sulfur dioxide may be gaseous even at relatively low temperature so that super-atmospheric pressure may be required to maintain such solvents in liquid form. Generally pressures of up to about 100 p.s.i. or more are utilized. When solvents are present during the treating step, the amount of solvent may be present from about 0.01 percent to about 1000 percent by weight, based on the weight of the linear alkylbenzene, and

somewhat more preferably, the amount of solvent may be present from about 10 percent to about 1000 percent by weight, on the same basis.

A presently preferred solvent is sulfur dioxide, because it complexes with sulfonating agents, particularly SO3.

Because of the difficulty of working with liquid sulfur dioxide, it is preferred to minimize the amount of sulfur dioxide utilized for the sulfonation reaction and to recycle the same where practical. Further, in certain embodiments of the invention, the treating step may occur in the presence of a sulfonatable agent capaole of reacting and/or complexmg with any free and/or complexed SO3. Without being bound by any particular theory, these sulfonatable agents likewise may function as aids in controlling the viscosity of the reactants/reaction products, and as heat sinks for the exotherm of the sulfonatior reaction. The sulfonation agents aiso tend to minimize .ocalizeo over- s_-ifonation e: the . near ai y.cenzen _r.α ™-edirat-_ tr.c reactivity ef the sulfonating agent re.ative to t e -.near ≤iky benzene. Presently preferred sulfonatac.- aαents cacao.e cr reaction and/or complexmg with any free and/or compiexeo sulfonating agents are linear or branched alkylaryl compounds, toluene, cumene, xylene, olefins, unsaturated esters, ammonia, organic ammonia derivatives, water and mixtures thereof. In embodiments where such sulfonatable agents are present during the treating step, the amount of sulfonatable agent present (if any) during the treating step may range from about 0.01 percent to about 1000 percent by weight, based on the weight of the sulfonating agent utilized. In preferred embodiments, the

amount of sulfonatable agent present during the treating step may range from about 10 percent to about 100 percent by weight, on the same basis. Further, in more preferred embodiments of the invention, both a sulfonatable agent capable of reacting and/or complexmg with any free and/or complexed sulfonating agent, as well as the earlier described solvents may be present in equal or different amounts during the treating of linear alkylbenzene with a sulfonating agent, the aging step, the bleaching step and the neutralization step. Further, during the practice of certain embodiments of the invention, matrix sulfonation may also be utilized. Matrix sulfonation involves pre-mix g of linear alkylbenzene and a sulfonatable agent moderator prior to treating with the sulfonating agent and subsequently allowing the sulfonation to occur. Examples of sulfonatable agent moderators include, but are not _imited to, pyridine, dimethyl ormamide, and trimet.nyiamine. Such a method moderates the attac-. of tne sulfonation agent en tne reeostoc. oorco-e^to, "inir.zes loca.izeo over-sulfonation cr tne ..near J.- ..cenzene, ano minimizes tne production cf unαesireα c_.crcα_::s and ceicr oodies.

Further, during sulfonation of linear alkylbenzenes, loop sulfonation may be practiced. During loop sulfonation, the treating step is repeated a number of times, either in a continuous loop-type re-circulating system or in batch re- sulfonation whereby additional sulfonating agent is added to an initially sulfonated intermediate reaction product. During sulfonation of linear alkylbenzene with particular sulfonating agents, whether "neat" or in the presence of a solvent, diluent

or other material, the reaction is conducted under sulfonation conditions, especially as described above.

In general, after the sulfonation step (and the aging step if desired) , linear alkylbenzene sulfonic acids are stabilized with water. The amount of water used is typically about 0.5 to 1.0 percent by weight, based on the weight of the linear alkylbenzene sulfonic acid. The water breaks up undesirable linear alkylbenzene sulfonic anhydrides which may be formed during the sulfonation step.

Bleaching

In general, after the sulfonation step, the resulting dark colored linear alkylbenzene sulfonic acid is contacted with a protic reagent and an oxidizing agent, i.e. hydrogen peroxide, where the contacting is performed at a sufficient temperature ano for a sufficient time to produce a linear alkylbenzene sulfonic acid product r.avi e _. reduced color. Tne cleacr.mα step may ce conducted eitner oefore or after the water staeilizaticr. step. In certain emoooiments of the invention, the . near alkylbenzene sulfonic acid may be treated with an cxiαizmg aαent and a protic reagent in a batch mode, a continuous moαe or a combination thereof. Further, in certain embodiments cf the invention, the linear alkylbenzene sulfonic acid may be treated with a premix of an oxidizing agent and a protic reagent in a batch mode, a continuous mode or a combination thereof.

Representative protic reagents suitable for use in the bleaching step of the invention include, but are not limited

to, water, alcohols of the formula R(OCH2CH2) _n ^0H where to

C20 and n is 0 to about 14, glycerin, ethanolamine, diethanolamine, and triethanolamine. In certain embodiments of the invention, the linear alkylbenzene sulfonic acid is treated with protic reagent in a range of 0.50 percent to about 15.0 percent by weight, based on the weight of the linear alkylbenzene sulfonic acid. Somewhat more preferably, the amount of protic reagent used is 4 percent to 10 percent by weight, on the same basis. The most preferred oxidizing agent is hydrogen peroxide, which may be supplied in various forms and concentrations. The form of choice is an aqueous solution, with a concentration in the range of 0.10 percent to 70 percent, based on the total weight of the solution. A more preferred concentration is in the range of 30 percent to 50 percent, on the same basis. In certain embodiments of the invention, the linear alkylbenzene sulfonic acid is treated with hydrogen peroxide m a range of 0.10 percent to aoout 5.0 percent oy weight, cased on the weiαr.t of tne linear alkyioenzene sulfonic acid. Some wnat more preferably, the amount cf ydrogen peroxide used is aoout C.5 percent to 2.C percent by weight, on the same basis.

In a batcn mode of treatment, the linear alkylbenzene sulfonic acid and protic reagent are contacted at a temperature of about 0°C to about 80°C, for a time sufficient to produce a homogeneous mixture with agitation. In a more preferred mode of treatment, the linear alkylbenzene sulfonic acid and protic reagent are contacted at a temperature of about 25°C to about 50°C, for a time sufficient to produce a homogeneous mixture. The linear alkylbenzene sulfonic acid/protic reagent mixture is

then contacted with hydrogen peroxide at a temperature of about 0°C to about 80°C, for a time sufficient to produce a homogeneous mixture. In a more preferred embodiment, the linear alkylbenzene sulfonic acid/protic reagent mixture is then contacted with hydrogen peroxide at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous mixture; said mixture posses a Klett color of about 8. In a most preferred embodiment, the linear alkylbenzene sulfonic acid/protic reagent mixture is then contacted with hydrogen peroxide at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous mixture with agitation; said mixture posses a Klett color of less than about 2.

In a batch mode of treatment, the linear alkylbenzene sulfonic acid and a protic reagent/hydrogen peroxide pre- mixture solution are contacted at a temperature of about 0°C to about 80°C, for a time sufficient to produce a homoαeneous mixture with agitation. In a still more creferrec mode of treatment, the linear alkylbenzene sulfonic acid and erotic reagent/hydrogen peroxide mixture are contacted at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous mixture; said mixture posses a Klett color of less than about 8. In a most preferred mode of treatment, the linear alkylbenzene sulfonic acid and protic reagent/hydrogen peroxide mixture are contacted at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous mixture; said mixture posses Klett a color of less than about 2.

In a continuous mode of treatment, the linear alkylbenzene sulfonic acid and protic reagent are contacted at a temperature of about 0°C to about 80°C, for a time sufficient to produce a homogeneous mixture. In a more preferred mode of treatment, the linear alkylbenzene sulfonic acid and protic reagent are contacted at a temperature of about 25°C to about 50°C, for a time sufficient to produce a homogeneous mixture. Without isolation, the linear alkylbenzene sulfonic acid/protic reagent mixture is then contacted with hydrogen peroxide at a temperature of about 0°C to about 80°C, for a time sufficient to produce a homogeneous mixture. In a still more preferred embodiment, the linear alkylbenzene sulfonic acid/protic reagent mixture is then contacted with hydrogen peroxide at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous mixture; said mixture posses a Klett color of less than 8. In a most preferred embodiment, the linear alkylbenzene sulfonic acid/protic reagent mixture is contacted with r.yαroαer. peroxide at a temperature cf aDout __5°C to aoout 60°C, for a time sufficient tc produce a nomogenecus mixture; said mixture posses a Klett color cf less than aoout

__ .

In a continuous mode of treatment, the linear alkylbenzene sulfonic acid and protic reagent/hydrogen peroxide pre-mixed solution are contacted at a temperature of about 0°C to about 80°C, for a time sufficient to produce a homogeneous mixture. In a still more preferred mode of treatment, the linear alkylbenzene sulfonic acid and protic reagent/hydrogen peroxide pre-mixed solution are contacted at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous.

In a still more preferred embodiment, the linear alkylbenzene sulfonic acid/protic reagent mixture is then contacted with hydrogen peroxide at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous mixture; said mixture posses a Klett color of less than 8. In a most preferred embodiment, the linear alkylbenzene sulfonic acid/protic reagent mixture is then contacted with hydrogen peroxide at a temperature of about 25°C to about 60°C, for a time sufficient to produce a homogeneous mixture; said mixture posses a Klett color of less than about 2.

The bleaching step of the invention has been found to significantly reduce the color of the starting linear alkylbenzene sulfonic acids to a Klett of less than about 15, independent of the mode of sulfonation, the starting color of sulfonic acid, the irrigation rate at which the sulfonic acid was produced (continuous falling film mode) , or the presence or acsence of un-sulfonated linear al yloenzene.

Neutralization The lignt colored linear ai.:yloenzer.e suifen.c acids produced by tne invention may be further converted to linear alkylbenzene sulfonates by a neutralization procedure. This neutralization procedure may take place immediately after the above described bleaching step(s) or at a later time. It has been discovered that neutralization of the bleached linear alkylbenzene sulfonic acid mixture to a pH of about 6.0 or greater affords an additional color reducing effect to the final linear alkylbenzene sulfonate material, as compared to un-bleached linear alkylbenzene sulfonic acid. The color

reduction is typically about 5 to 20 Klett units. Without being bound by any particular theory, it is believed that this effect is an in situ activation of residual hydrogen peroxide.

The above described neutralization can be effected utilizing a solution of base have a cation selected for the group consisting of alkali metals, ammonium cations, organic ammonium cations, and mixtures thereof. The neutralizing agent is selected from, but not limited to, the group consisting of NaOH, MgO, Mg(OH) ₂ , KOH, Ca(OH) ₂ , tπethanolamme, diethanolam e, ammonia, isopropylamine, and mixtures thereof.

All documents, e.g., patents and -journal articles, cited above or below are hereby incorporated by reference in their entirety.

In the following examples, all amounts are stated in percent by weight of active material unless indicated otherwise.

One skilled in tne art will recognize tr.at modifications may be mace in the present invention without neviatir.c rrcr tne spirit or scope of the invention. Tne inventior. . .llustrateo rurtner by the following examples wnicr. are net to oe construed as limiting the invention or scope of the specific procedures or compositions described herein.

EXAMPLE 1

Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques by contacting linear alkylbenzene (LAB) produced by the reaction of an olefm and benzene, with one of the following: Gaseous Sθ3/aιr, SO2/SO3,

H2SO4 or oleum. Approximately lOOg of LAS produced from the above reaction is heated to about 40°C for about 20 minutes

(i.e., aged) to drive the reaction to completion. The LAS acid is then stabilized by the addition of about 0.5 wt. % water. The color of the crude sulfonic acid is deep red, with a Klett of about 40.

The first step of the bleaching process involves combining lOOg of LAS with aDout 6 g of water (6 wt . ^" ) at room temperature (23°C) with mixing, which produces a 20°C exotherm. The temperature of the LAS/H2O slurry is ad]usteα to about 23°C and about 4g of H2O2 in tne form of a 50- active aqueous solution (4 w . ^r ) is added; this additie*" results .r α 5°C exctr.erπ. The -.2O/F C2 treated LA2 .0 ... cr approximately 4 hours at room temoerat-r-ε 2 -2 . - ^~ fter this period of time the sulfonic acio solutic- r.ao __ r .ett of acc _^ t

EXAMPLE 2

Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques by contacting linear alkylbenzene (LAB) produced by the reaction of an olefm and benzene, with one of the following: Gaseous Sθ3/aιr, SO2/SO3,

H2SO4 or oleum. Approximately lOOg of LAS produced from the above reaction is heated to about 40°C for about 20 minutes

(i.e., aged) to drive the reaction to completion. The LAS acid is then stabilized by the addition of about 0.5 wt. % water. The color of the crude sulfonic acid is deep red, with a Klett of about 40. The first step of the bleaching process involves combining lOOg of LAS with about 6 g of water (6 wt . %) at room temperature (23°C) with mixing, which produces a 20°C exotherm. The temperature of the LAS/H2O slurry is adjusted to about 38°C ano about 4g of H2O2 m the form of a 501 active aqueous solution (4 wt . %) is added; this addition results in a 5°C exotherm. The H2O/H2O2 treated LAS is allowed to bleacn approximately 45 minutes at a temperature of about 38 C. After this period of time the sulfonic acid solution had a Klett of about 2.

EXAMPLE 3

Linear alkylbenzene sulfonic acid 'LAS .s crecared using standard sulfonation techniques cy conteot nd .mear al y Denzene \LAB produced by the react er or an o.efin ano oenzene, witn one of the following: Gaseous 22. /air, ΞO2 ΞO3, 2SC_: or oleum. Approximately lOOg of LAS produced from tne aoove reaction is heated to about 40 ^C C for about 20 minutes i.e., aged) to drive the reaction to completion. The LAS acid is then stabilized by the addition of about 0.5 wt . % water. The color of the crude sulfonic acid is deep red, with a Klett of about 40.

The first step of the bleaching process involves combining lOOg of LAS with about 6 g of methyl alcohol (6 wt . °- ) at room temperature (23°C) with mixing, which produces a 15°C exotherm.

The temperature of the LAS/H2O slurry is adjusted to about 38°C and about 4g of H2O2 in the form of a 50% active aqueous solution (4 wt. %) is added; this addition results in a 5°C exotherm. The methyl alcohol/H2θ2 treated LAS is allowed to bleach approximately 45 minutes at a temperature of about 38 C. After this period of time the sulfonic acid solution had a Klett of about 2.

EXAMPLE 4 Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques by contacting linear alkylbenzene (LAB) produced by the reaction of an olefm and benzene, with one of the following: Gaseous Sθ3/aιr, SO2/SO3,

H2SO4 or oleum. Approximately lOOg of LAS produced from the aoove reaction is heated to about 40°C for aoout 2C minutes (i.e., aged) to drive the reaction to completion. The LAS acid is tnen stacil zeo by the addition of aoout C.5 w . water. The color of the crude sulfonic acid is deep red, with a Klett of aoout 50. The first step of tne bleaching process involves con_cιr.ιng lOOg cf LAS with about 6 g of water (6 wt . %) at room temperature (23°C) with mixing, which produces a 20°C exotherm. The temperature of the LAS/H2O slurry is adiusted to about 38°C and about 2g of H2O2 in the form of a 50% active aqueous solution (2 w . %) is added; this addition results a 5°C exotherm. The H2O/H2O2 treated LAS is allowed to bleach approximately 45 minutes at a temperature of about 38 C. After this period of time the sulfonic acid solution had a Klett of about 24.

Neutralization of the sulfonic acid solution is carried out at room temperature (23°C) by sequentially charging a vessel equipped with stirring means with: (1) a sufficient amount of H2O/H2O2 treated LAS and water to prepare a slurry containing 35% by weight of neutralized LAS and (2) a sufficient amount of caustic (NaOH) to neutralize about 75% of the acid in the slurry. This procedure results in a partially neutralized material having an initial pH = 1 -2. The remaining caustic is then added slowly and the pH adjusted to approximately 8.5. This method of neutralization avoids foaming due to hydrogen peroxide destruction. After 24 hours at pH = 8.5 no active peroxide remains and the final 35% active slurry has a color of Klett = 5.

EXAMPLE 5

Linear alkylbenzene sulfonic acid (LAS) s prepared using standard sulfonation techniques by centactmα linear al K . -oenzene LAB) produced θy tne reaction _r .:. .er.r ana cenzene, with one of tne following: Gaseous 21./ air, 223 ΞC3, ^J 2SC-4 or oieum. Approximately lOOg or LAS croαucec rrcr tne acove reaction is heated to aoout 40°C for about 20 minutes

(i.e., aged) to drive the reaction to completion. The LAS acid is then stabilized by the addition of about 0.5 wt. % water.

The color of the crude sulfonic acid is deep red, with a Klett of about 55.

The first step of the bleaching process involves combining lOOg of LAS with about 6 g of water (6 wt. %) at room temperature (23°C) with mixing, which produces a 20°C exotherm. The temperature of the LAS/H2O slurry is adjusted to about 40°C

and about lg of H2O2 in the form of a 50% active aqueous solution (1 wt . %) is added; this addition results in a 5°C exotherm. The H2O/H2O2 treated LAS is allowed to bleach

0 approximately 46 minutes at a temperature of about 40 C. After this period of time the sulfonic acid solution had a Klett of about 14.

EXAMPLE 6

Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques at greatly increased irrigation rates by contacting linear alkylbenzene (LAB) produced by the reaction of an olefin and benzene with gaseous SO3 and air in a falling film reactor. The irrigation rate used is 76. The LAS product produced from the above reaction rates requires no digestion/aging. The resulting LAS acid is stabilized with 0.5 wt . ^" ; water. The color cf the crude sulfonic acid is black in appearance, with a Klett of acout 85.

The first step cr tne _: leaching process involves combining lOOg of LAS with aoout 5 g of water 5 wt . ' • at a temperature of aoout 35°C with mixing, wnicn produces a 18°C exotherm. The temperature of the LAS/H2O slurry is adjusted to about 35°C and about lg of H2O2 in the form of a 50% active aqueous solution

(1 wt. %) is added; this addition results in a 5°C exotherm. The H2O/H2O2 treated LAS is allowed to bleach approximately 21 minutes at a temperature of about 35 C. After this period of time the sulfonic acid solution has a Klett of about 19.

EXAMPLE 7

Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques at greatly increased irrigation rates by contacting linear alkylbenzene (LAB) produced by the reaction of an olefm and benzene with gaseous SO3 and air in a falling film reactor. The irrigation rate used is 76. The ratio of LAB:Sθ3 is about 1:1.09. The LAS product produced from the above reaction rates requires no digestion/aging. The resulting LAS acid is stabilized with 0.5 wt . % water. The color of the crude sulfonic acid is black in appearance, with a

Klett of about 109. The ^-HNMR and GC-MS analysis indicates that the product contains no detectable residual LAB.

The first step of the bleaching process involves combining lOOg of LAS with about 6 g of water (6 wt . %) at a temperature of about 35°C with mixing, whicn produces a 20°C exotherm. The temperature of the LAS/H2O slurry is adjusted to about 35°C and about 2g of H2O2 the form cf a 50- active aqueous solution

2 wt. _.s aooed; th s addition results .- a 5°C exctherr. Tne H2O H2O2 treated LAS is alioweo to cleacπ approximately 20 c rrinutes at a temperature cf aoout 35 Z . After this pence cf time the sulfonic acid solution has a Klett of acout 24.

EXAMPLE 8

Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques at greatly increased irrigation rates by contacting linear alkylbenzene (LAB) produced by the reaction of an olefin and benzene with gaseous SO3 and air in a falling film reactor. The irrigation rate used is 76. The ratio of LAB:S03 is about 1:1.09. The LAS product produced from

the above reaction rates requires no digestion/aging. The resulting LAS acid is stabilized with 0.5 wt. % water. The color of the crude sulfonic acid is black in appearance, with a Klett of about 109. The iHNMR and GC-MS analysis indicates that the product contains no detectable residual LAB.

The first step of the bleaching process involves combining lOOg of LAS with about 6 g of water (6 wt . %) at a temperature of about 38°C with mixing, which produces a 20°C exotherm. The temperature of the LAS/H2O slurry is adjusted to aoout 35°C and about 2g of H2O2 in the form of a 50% active aqueous solution

(2 wt. %) is added; this addition results in a 5°C exotherm. The H2O/H2O2 treated LAS is allowed to bleacn approximately 2C minutes at a temperature of about 35 C. After this period of time the sulfonic acid solution has a Klett of about 24. Neutralization of the sulfonic acid solution is carried out at room temperature ι23°C) by sequential,y cnargmc a vessel equipped with stirring means _ι:h: 1 a sufficient amount of H2O H2O2 treated LAS ano ..attr ^* r rec.re _ s._rr_ containing 35% by weight of neutra..zee LAS a.na 2 a sufficient amount of caustic (NaOH to ne._tra. ze acc_- " or the acid n the slurry. This procedure results in a partially neutralized material having an initial pH = 1 -2. The remaining caustic is then added slowly and the pH adjusted to approximately 8.5. This method of neutralization avoids foaming due to hydrogen peroxide destruction. After 2 hours at pH = 8.5 the final 35% active slurry has a Klett of about 5.

Example 9

Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques by contacting linear alkylbenzene (LAB) produced by the reaction of an olefin and benzene, with one of the following: Gaseous S03/air, SO2/SO3, H2SO4 or oleum. Approximately lOOg of LAS produced from the above reaction is heated to about 40°C for about 20 minutes

(i.e., aged) to drive the reaction to completion. The LAS acid is then stabilized by the addition of about 0.5 wt. % water.

The color of the crude sulfonic acid is light red, with a Klett of about 21.

The first step of the bleaching process involves combining lOOg of LAS with about 5 g of water (5 wt . %) at a temperature of about 37°C with mixing, which produces a 20°C exotherm. The temperature of the LAS/H2O slurry is adjusted to about 37°C and about 0.2g of H2O2 m the form of a 50% active aqueous solution

(0.2 wt . %) is added; this addition results m a 5°C exotherm. The H2O/H2O2 treated LAS is allowed to bleach approximately 3 c nours at a temperature of acout 37 z . After this cencα of time the sulfonic acid solution has a Klett of aoout 14. Neutralization of the sulfonic acid solution is carrieα out at room temperature (23°C) by sequentially cnarging a vessel equipped with stirring means with: (1) a sufficient amount of H2O/H2O2 treated LAS and water to prepare a slurry containing 41% by weight of neutralized LAS and (2) a sufficient amount of caustic (NaOH) to neutralize about 75% of the acid in the slurry. This procedure results in a partially neutralized material having an initial pH = 1 -2. The remaining caustic is then added slowly and the pH adjusted to

approximately 11.0. After 2 hours at pH = 11.0 the final 41% active slurry has a Klett of about 10.

The neutralized product is treated with 400 ppm active NaOCl, and heated to 65°C for 2.5 hours. The color of the resulting material has a Klett of about 5.

Comparative Example

Linear alkylbenzene sulfonic acid (LAS) is prepared using standard sulfonation techniques by contacting linear alkylbenzene (LAB) produced by the reaction of a chloroparaffin and benzene, with one of the following: Gaseous Sθ3/aιr,

SO2/SO3, H2SO4 or oleum. Approximately lOOg of LAS produced from the above reaction is heated to about 40°C for about 20 minutes (i.e., aged) to drive the reaction to completion. The LAS acid is then stabilized by the addition cf about 0.5 wt . 1 water. The color of the crude sulfonic acid is deep red, with a Klett of aoout 65.

The first step cf the bleacninc process inv-.ves "errr nir.e lOOg cf LAS with aDout 6 g of water 1 ..t . _: roerr temperature (23°C) with mixing, whicn produces _ 2C ^C 2 exotr.err. Tne temperature of the LAS/H2O slurry is adjusted to aoout 23°C and aoout 4g of H2O2 in the form of a 50% active aqueous solution (4 wt . %) is added; this addition results in a 5°C exotherm. The H2O/H2O2 treated LAS is allowed to bleach approximately 4 hours at room temperature (23°C) . After this period of time the sulfonic acid solution had a Klett of about 64. Extended bleaching times up to 48 hours produced no further lowering of the sulfonic acid color.

From the foregoing, it will be appreciated that although specific embodiments of the invention have been described herein for purposes of illustration, various modification may be made without deviating from the spirit or scope of the invention.