GB2155474A - Process for the continuous reaction of organic compounds with sulfur trioxide - Google Patents

Abstract

Diluted gaseous sulfur trioxide is reacted with a liquid sulfonatable or sulfatable compound or mixtures thereof, e.g. an alkyl benzene or fatty alcohol, by: (a) diluting said SO3 with a gas relatively inert with respect to the sulfonation reaction within a volume ratio of SO3:inert gas of from 1:5 to 1:50, (b) forming a reactant liquid comprising said sulfonatable organic compound or mixtures thereof and its sulfonation derivative which has been recycled, (c) passing said reactant liquid through a shear-producing means to establish a zone of turbulent flow, the temperature of said reactant liquid in said zone of turbulent flow being from 90 DEG F (32.2 DEG C) to 130 DEG F (54.4 DEG C). (d) introducing said diluted SO3 gas into said zone of turbulent flow at a temperature of from 80 DEG F (26.7 DEG C) to 130 DEG F (54.4 DEG C) to form a dispersion of said diluted SO3 gas in said reactant liquid at a gas to liquid volume ratio of from 5:1 to 30:1, (e) maintaining contact of said reactant liquid and said diluted SO3 gas for a period of at least 1.5x10<-3> seconds to form a reaction liquid and a gas phase containing essentially no SO3, (f) separating a major portion of said gas phase from the reaction liquid, (g) removing a portion of the reaction liquid as sulfonated product, the weight ratio of sulfonated product removed to the remainder of the reaction liquid being in the range of from 1:25 to 1:500, (h) recycling said remainder of said reaction liquid and adding said sulfonatable organic compounds or mixtures thereof at a rate of from 100% to 105% of the stoichiometric equivalent of the rate of SO3 addition in step (d) to form monosulfonates of the sulfonatable organic compound or mixtures thereof. f

Description

SPECIFICATION Process for the continuous reaction of organic compounds with sulfur trioxide Field of the Invention This invention relates to a process and apparatus for the continuous sulfation and sulfonation of organic compounds with sulfur trioxide. More particularly, this invention relates to a process and apparatus wherein gaseous sulfur trioxide diluted with an inert gas is reacted under conditions characterized by a high level of turbulence at the point of contact with a liquid organic sulfatable or sulfonatable compound or mixtures thereof. The process is additionally characterized by the use of a dominant bath recycle cooling system as hereinafter described. The process results in a high yield of the desired reaction product or mixture of products without discoloration or other undesirable side reactions.

In this specification and claims the terms "sulfonation", and the related terms such as "sulfonating", "sulfonate", "sulfonatable" and "sulfonated", are used sometimes in a generic sense as applying both to true sulfonation and to sulfation, and sometimes in a specific sense limited to true sulfonation.

Where the context in which the term "sulfonation" or related terms is used does not require the specific sense, it is to be construed generically.

Sulfur trioxide is a preferred sulfonating agent because it reacts in substantially stoichiometric quantities, and its reactions do not produce by-products which may necessitate further processing for separation from product. For example, sulfur trioxide is preferred over sulfuric acid or oleum sulfonating agents which ordinarily are used in stoichiometric excess thereby providing dilute sulfuric acid by-product which is sometimes separated from product before further processing or which require an agent such as sodium hydroxide for neutralization. Chlorosulfonic acid sulfonating agents upon reaction produce hydrochloric acid which ordinarily requires further process.

ing for its disposal.

While sulfur trioxide is an effective sulfonating agent, it is so highly reactive and its reactions are so exothermic that charring of the reaction mixture often results, accompanied by contamination and discoloration of product.

It is an object of this invention to provide a novel sulfonation process and apparatus employing gaseous sulfur trioxide.

It is a further object of this invention to provide a sulfonation process which is economical and readily practiced.

It is a further object of this invention to provide a sulfonation process and apparatus for the reaction of gaseous sulfur trioxide with liquid organic sulfonatable compounds whereby charring is eliminated or significantly reduced thereby providing flexibility in producing product.

U.S. Patent 4,226,796 issued October 7, 1 980 to Akred et al, discloses a continuous sulfonation process that includes a recycle cooling system and a high level of turbulence at the point of contact of the feedstock and undiluted sulfur trioxide. A static mixer without moving parts is preferred to produce the required turbulence. A recycle ratio of 40:1 to 2000:1 is specified.

Summary of the Invention The process aspect of the invention is a continuous process for sulfonating a liquid sulfonatable organic compound or mixtures thereof by reacting said compound or mixtures thereof with gaseous S03 comprising: a) diluting said S03 with a gas relatively inert with respect to the sulfonation reaction within a volume ratio range of 503:inert gas of from about 1:5 to about 1:50, preferably from about 1:10 to about 1::20, b) forming a reactant liquid comprising said sulfonatable organic compound or mixtures thereof and its sulfonation derivative which has been recycled, c) passing said reactant liquid through a shear-producing means to establish a zone of turbulent flow, the temperature of said reactant liquid in said zone of turbulent flow being from about 90"F to about 1 30'F, d) introducing said diluted SO3 gas into said zone of turbulent flow at a temperature of from about 80"F to about 130"F to form a dispersion of said diluted S03 gas in said reactant liquid at a gas to liquid volume ratio of from about 5:1 to about 30:1, preferably from about 10:1 to about 25::1, e) maintaining contact of said reactant liquid and said diluted SO3 gas for a period of at least about 1.5 X 10-3 seconds to form a reaction liquid and a gas phase containing essentially no SO3, f) separating a major portion of said gas phase from the reaction liquid, g) removing a portion of the reaction liquid as sulfonated product, the weight ratio of sulfonated product removed to the remainder of the reaction liquid being in the range of from about 1:25 to about 1:500, preferable from about 1:40 to about 1:200, most preferably from about 1:40 to about 1::100, h) recycling said remainder of said reaction liquid and adding said sulfonatable organic compounds or mixtures thereof at a rate of from about 100% to about 105% of the stoichiometric equivalent of the rate of SO3 addition in step (d) to form monosulfonates of the sulfonatable organic compound or mixtures thereof.

Preferred embodiments and additional aspects of the invention are described hereinafter.

Detailed Description of the Invention The Sulfonatable Organic Compound The invention is not limited to the preparation of any particular type of sulfonates so long as an organic compound to be sulfonated is capable of reaction with sulfur trioxide within the specified ranges of process conditions. The preparation of materials which in acid or more typically in water-soluble salt form are non-soap anionic surface active agents (hereinafter anionic surfactants) is a particularly useful embodiment of the invention.

Anionic surfactants include the salts of the sulfation or sulfonation products of hydrocarbons, alcohols and alkyl phenols. The designation sulfation refers to reaction of the -SO3H radical at a hydroxy site of an alcohol or alkyl phenol to provide the structure -C-OSO3H .

I The designation sulfonation refers to reactions which result in the structure -C-SO3 H I in which there is a carbon to sulfur bond. In the process of the invention designated sulfonation, the two reactions will occur simultaneously when the sulfonatable organic compounds are a mixture of one or more hydrocarbons and one or more alcohols or alkyl phenols.

Any organic compound or mixture of compounds which is liquid under the temperature and pressure conditions of the reaction herein and which is sulfonatable can be used in the process of this invention. Sulfonatable organic compounds which are normally solid under reaction conditions can also be employed herein provided they are dissolved in an inert solvent which is liquid under reaction conditions.

According to Schwartz and Perry, "Surface Active Agents", Interscience, New York, 1949, sulfonatable compounds include, for example, compounds having an alcoholic hydroxyl, compounds having an olefinic linkage and compounds having an aromatic nucleus.

Preferred organic sulfonatable compounds within the above described classes and used in the process of this invention include, for example, alkyl aryl hydrocarbons, higher olefins, higher fatty alcohols, condensation products of higher fatty alcohols and ethylene oxide, condensation products of alkyl phenols and ethylene oxide, and higher fatty acids.

Sulfonatable alkyl aromatic compounds include mononuclear (e.g., benzene and toluene) or polynuclear (e.g., naphthalene and anthracene) organic compounds. More particularly included as examples are the higher alkyl aryl hydrocarbons having an alkyl constituent containing 9 to 1 8 carbon atoms, for example, those alkyl aryl hydrocarbons derived from- benzene, toluene and naphthalene.

The alkyl substituent can be straight (linear) or branched chain in structure and comprises such groups as decyl, dodecyl, tridecyl, pentadecyl, octadecyl, mixed chain alkyls, e.g., those derived from kerosene, fatty materials, polymers of lower olefins, cracked wax olefins and the like. Examples of this class are the higher alkyl benzenes wherein the alkyl group is about 1 2 to 1 5 carbon atoms, e.g., tetrapropylene and pentapropylene benzene. The linear alkyl benzenes are especially preferred.

Also suitable are long chain olefins containing 8 to 24 carbon atoms. These olefins can be straight or branched chain and contain one or more olefinic linkages. The olefinic linkages can be found at any position. For example, random olefins wherein the olefinic linkages are randomly distributed over the chain length are suitable employed herein. Preferred olefins are olefins with the olefinic linkage at the alpha position such as, for exmaple, 1-dodecene, 1-tridecene, or 1-octadecene.

Sulfatable higher fatty alcohols include straight and branched chain fatty alcohols including those from natural sources, e.g., coconut oil and tallow, and those from synthetic sources. These alcohols preferable range in chain length from 8 to 24 carbon atoms. Specific examples are dodecanol, hexadecanol, octadecanol and the like. Also suitable are the ethylene oxide condensates of such fatty alcohols, e.g., condensates resulting from reaction with from 1 to about 10 moles of ethylene oxide per mole of alcohol.

Also suitable are condensation products of alkyl phenols with ethylene oxide, e.g., 1 to 10 moles. Preferred alkyl phenols are those wherein the alkyl ranges from about 8 to about 18 carbon atoms, e.g., nonyl phenol and tridecyl phenol, containing from about 6 to about 8 moles of ethylene oxide.

Sulfonatable higher fatty acids are exemplified by those ranging from about 10 to about 20 carbon atoms in chain length which are preferably from natural sources. Specific examples are the individual acids, e.g., lauric, palmitic and stearic acids and the mixtures of acids derived from coconut oil and tallow.

The sulfates or sulfonates of the above organic compounds as formed by the process of this invention, particularly in their neutralized form, are useful as detergents, emulsifiers and surfactants, particularly in the washing of textiles and other fabrics.

Examples of sulfonatable lower alky aryl hydrocarbons are toluene and xylene. The sulfonates of toluene and xylene are useful hydrotroping agents.

The sulfonated products resulting from the process of this invention are most usefui if they are neutralized after reaction by well known means with any of the usual neutralization reagents, e.g., sodium, potassium, magnesium, or ammonium hydroxide, sodium or potassium carbonate, triethanolamine and the like.

The Sulfur Trioxide Any suitable source of gaseous sulfur trioxide can be employed. For example, gaseous sulfur trioxide can be provided by a stabilized liquid sulfur trioxide having more than 99% available S03 content, and offered for sale under the trade name "Sulfan". If this stabilized liquid sulfur trioxide is desired to be employed, it must be transformed into gaseous form for use herein, for example by pumping with a metering pump into a conventional sulfur trioxide vaporizer wherein the liquid is vaporized. The burning of sulfur under conditions to maximize S03 production and minimize SO2 content is also a satisfactory source.

The Inert Gas The inert diluting gas can be, for example, air, nitrogen, carbon dioxide, sulfur dioxide or any other gas which is inert in the reaction medium. Air is a preferred diluting gas because of its availability and low cost. The diluting gas can be simply mixed with the gaseous sulfur trioxide from the vaporizer or other source. Dilute sulfur trioxide can also be obtained from sulfur burning as described hereinbefore or in the form of converter gas from the contact sulfuric acid process. Such converter gas or product of sulfur burning is usually an air-sulfur trioxide mixture containing from about 7% to about 10% sulfur trioxide by volume.

The inert gas must be relatively free of moisture, preferably having a water content no greater than the equivalent of a - 60"F dew point.

The Process As outlined hereinbefore, the advantages of sulfonation with sulfur trioxide include speed and completeness of the reaction, and the absence of by-products. Other related advantages include a reduced usage of total sulfur and neutralization materials.

Relative to sulfonation processes utilizing sulfur trioxide presently used or described, the present invention provides simplicity, low cap ital cost, compactness, and minimal pressure and vacuum requirements.

Use of a dominant bath recycle cooling system is known. The present invention utilizes this system, but also effectively accomplishes other process conditions in a simple and efficient matter.

A most important condition of the present invention is the passage of reactant liquid comprising the sulfonatable organic compounds through a zone of turbulent flow and the introduction of the diluted S03 gas into this zone so as to produce a rapid and essentially even dispersion of small bubbles of diluted 803 across the stream of reactant liquid. This condition is preferably accomplished by a mechanical shear producing means, most preferably by an in-line mixer.

In-line mixers can also be variously described as in-line agitators and in-line homogenizers. Preferably the mixer also acts as a pump for the process stream which minimizes pressure and vacuum requirements for raw material, finished product and exhaust gas streams. In general, the diluted S03 gas is introduced into the reactant liquid at pressures below about 30 psig, typically from about 6 psig to about 1 5 psig.

Preferred in-line mixers are pipeline mixers with single or multiple propeller or turbine impeller stages with angled blades mounted radially on an axial shaft. Any design that meets the turbulence and dispersion requirements of the present invention is satisfactory, the essential requirements being introduction of the diluted S03 gas into a zone of turbulence, production of a gas-in-liquid mixture in which the gas phase comprises at least about 80%, preferably at least about 90%, and as much as about 97% of total volume. The average gas bubble diameter in the zone of turbulence is estimated to be not greater than about 500 microns with a substantial number of bubbles having a diameter of about 40 microns as determined by examination of the product stream.This result can be accomplished by peripheral impeller blade speeds of at least about 10 ft./second, preferably from about 50 to about 85 ft./second. A total mechanical shear plus gas versus liquid shear of from about 250 ft./second to about 800 ft./second provides the necessary dispersion of diluted 803 gas in the reactant liquid.

Particulary suitable mechanical in-line mixers are those manufactured by the Greercio Corporation, Hudson, N.H. with impeller diameters of 2 inches to 10 inches and suitably modified to meet requirements of the present invention. These mixers are generally designated "Gifford-Wood" in-line mixers.

In an alternate practice of the process of the invention, a venturi is employed to produce high turbulence at the point of contact of the diluted S03 and reactant liquid. This less efficient system is best employed with removal:recycle ratios not greater than about 1:200, preferably from about 1:300 to about 1:400.

Since the sulfonation reaction proceeds very rapidly, a residence time of from about 1.5 X 10-3 seconds to about 0.75 X 10-4 reduces the concentration of S03 in the gas phase to essentially zero at which point the gas phase is removed by liquid-gas separation means which typically includes a zone of relatively low velocity, preferably laminar flow, for the gravity separation of inert gas and reaction liquid and demisting and/or scrubbing equipment for the inert gas outlet. When a sulfur burner is used to produce diluted SO3, small amounts of SO2 are removed and neutralized in this equipment prior to venting.

The Brinks Mist Eliminator, manufacutred by Monsanto Enviro-Chem Systems, inc., St.

Louis, Missouri is an example of suitable apparatus for use at the inert gas outlet.

Removal of a portion of the reaction liquid as sulfonated product can occur at any point in the process cycle after the reaction is essentially complete. Typically and preferably this occurs at any point between removal of the gas phase and introduction of the sulfonatable organic compound or mixtures thereof.

Because of the effectiveness of the gas-inliquid dispersion means, the sulfonated product steam will typically initially contain about 30% inert gas by volume in the form of bubbles with a diameter of from about 40 microns to about 1 ,000 microns.

Maintenance of the specified temperatures for the practice of the invention can be accomplished by cooling means such as a heat exchanger at any convenient point of the reaction cycle, typically after removal of a portion of the reaction liquid as sulfonated product. Because of the recycling of reactant liquid and the heat loss in the system, a temperature reduction of not more than about lOF', typically from about 3F' to about 5F", is sufficient to maintain temperature control.

EXAMPLE I Sulfonation of C13 Linear Alkyl Benzene Dry air is blown through the four gas injection tubes at a rate of 10 cubic feet/minute (SCFM basic) to prevent the back flow of the liquid C13 linear alkyl benzene. The pilot plant circulating system is filled with 5 gallons of the reactant liquid to a level at the base of the liquid-gas separator. Recycle pumping and inline mixing using a Gifford-Wood mixer are started. The flow of 7.5% S03 by volume in air at a temperature of 1 10'F is commenced.

Reactant liquid temperature is maintained at 11 5'F. The volume ratio of diluted S03 to recycled reactant liquid is maintained at 15:1.

The concentration of sulfonated product is measured by titration with 0.5N KOH and continuously by in-line conductivity measurement. Continuous addition of a stoichiometric amount of C,3 linear alkyl benzene relative to the S03 addition is commenced just before target 98% conversion is achieved. All subsequent operation is continuous with a removal: recycle ratio of 1:50.

Reaction liquid is removed as sulfonated products to maintain a balanced system and then held for 20 minutes outside the recycle loop. 2% water is added for anhydride conversion before continuous neutralization to sodium C13 alkyl benzene sulfonate.

A 98% conversion of alkyl benzene to alkyl benzene sulfonate is achieved. A Coleman transmission color of 94% through a 25 mm.

cell of 2.5% active solution at a light frequency of 425 cps is obtained.

EXAMPLE II Sulfation of Fatty Alcohol and Alcohol Ethoxylate A 230 molecular weight mixture of a C4 a5 fatty alcohol mixture with an average molecular weight of 230 and an average degree of ethoxylation of 1.0 mole of ethylene oxide per mole of alcohol is sulfated with the same procedure as for the C,3 alkyl benzene in Example 1. The feedstock includes approximately 40-50% of unethoxylated alcohol.

The output of sulfated product from the recirculating system is fed directly to continuous neutralization. This flow rate is remetered because the sulfation system has a free variable surface at the exhaust gas outlet.

A 97-99% conversion of reactant to sulfated product is achieved. At a 7.5% SO3 by volume concentration conversion is 97%; at 4% SO3 by volume, conversion is 99 + %.

Coleman transmission through a 40% solution is in the range of 80-85%.

Similar results are also obtainable if other organic compounds are substituted. For instance, high completeness is also achieved when fatty alcohols such as dodecanol, ethoxylated fatty alcohols such as octadecanol ethoxylated with an average of from 1 to about 5 moles of ethylene oxide per mole of alcohol, ethoxylated alkyl phenols such as nonyl phenol ethoxylated with from about 3 to about 8 moles of ethylene oxide or fatty acids such as stearic acid are substituted in the above examples.

Moreover, similar results are obtainable if mixtures of two or more organic compounds are substituted in the above examples.

The foregoing description has been presented describing certain operable and preferred embodiments of this invention. Other variations will be apparent to those skilled in the art.

Claims (7)

1. A continuous process for sulfonating a liquid sulfonatable organic compound or mixtures thereof by reacting said compound or mixtures thereof with gaseous SO3 comprising: (a) diluting said SO3 with a gas relatively inert with respect to the sulfonation reaction within a volume ratio of 503:inert gas of from 1:5 to 1::50, (b) forming a reactant liquid comprising said sulfonatable organic compound br mixtures thereof and its sulfonation derivative which has been recycled, (c) passing said reactant liquid through a shear-producing means to establish a zone or turbulent flow, the temperature of said reactant liquid in said zone of turbulent flow being from 90"F (32.2"C) to 130"F (54.4"C), (d) introducing said diluted SO3 gas into said zone of turbulent flow at a temperature of from 80"F (26.7"C) to 130"F (54.4"C) to form a dispersion of said diluted SO3 gas in said reactant liquid at a gas to liquid volume ratio of from 5:1 to 30::1, (e) maintaining contact of said reactant liquid and said diluted SO3 gas for a period of at least 1.5 X 10-3 seconds to form a reaction liquid and a gas phase containing essentially no S03, (f) separating a major portion of said gas phase from the reaction liquid, (g) removing a portion of the reaction liquid as sulfonated product, the weight ratio of sulfonated product removed to the remainder of the reaction liquid being in the range of from 1:25 to 1:500, (h) recycling said remainder of said reaction liquid and adding said sulfonatable organic compounds or mixtures thereof at a rate of from 100% to 105% of the stoichiometric equivalent of the rate of S03 addition in step (d) to form monosulfonates of the sulfonatable organic compound or mixtures thereof.

2. A process according to Claim 1 wherein said shear-producing means is an in-line mixer.

3. A process according to Claim 2 wherein said in-line mixer is mechanical with propeller or turbine impellers mounted radially on an axial shaft.

4. A process according to any of Claims 1 to 3 wherein the dispersion of diluted S03 gas in the reactant liquid at the point of introduction of said diluted SO3 is at a gas to liquid volume ratio of from 10:1 to 25:1.

5. A process according to any of Claims 1 to 4 wherein the weight ratio of sulfonated product removed to the remainder of the reaction liquid is in the range of from about 1:40 to about 1:100.

6. A process according to any of Claims 1 to 5 wherein said in-line mixer produces a mechanical shear of at least about 1 Oft./se- cond (3.05 m/sec.).

7. A process according to any of Claims 1 to 6 wherein said dispersion of said diluted S03 gas in said zone of turbulent flow provides an average gas bubbie diameter of not greater than 100 micrometres.