Sulfonation, sulfation, and sulfamation

[0002] This is a divisional application of Ser. No. 09/848,842, filed May 4, 2001, now allowed as U.S. Pat. No. 6,384,271.

[0003] The invention relates to a process for sulfonating, sulfating, or sulfamating an organic compound.

[0004] Sulfonation of organic compounds represents a major synthetic reaction. Sulfonations commonly use sulfuric acid and sulfur trioxide as the sulfonating agents. While sulfur trioxide presents major problems in terms of corrosivity, toxicity, and the consequences of leakage, it provides certain advantages. For example, sulfonation with sulfur trioxide can result in different and advantageous ratios of sulfonated isomers compared with the use of sulfuric acid and avoid safety problem with handling sulfuric acid.

[0005] The importance of the ratio of sulfonated isomers is conveniently described by the synthesis of p-cresol, extensively used in disinfectants and in the manufacture of resins. The sulfonation of toluene provides essentially a mixture of o- and p-toluene sulfonic acids, which are fused with sodium hydroxide to yield the corresponding o- and p-cresols (o- and p-methylphenols). Since the o-cresol is largely an unwanted byproduct, maximizing the ratio of para:ortho is highly advantageous in terms of ease of purification of the desired p-cresol, minimizing byproduct and waste streams, and minimizing energy use in the purification steps. The term regiospecificity is used to describe the ability of, in this application, a sulfonating agent, to affect the para:ortho ratio.

[0006] The sorption of sulfur trioxide by some basic organic compounds is well known. For instance, certain polyvinylpyridine resins form addition compounds with sulfur trioxide that can be used in sulfation reactions. See U.S. Pat. No. 3,057,855 disclosing use of a sulfur trioxide-poly(2-vinylpyridine) polymer for sulfation. See also W. Graf, in Chemistry and Industry, p 232, 1987 disclosing a pyridine-sulfur trioxide complex bound to a cross-linked polystyren for the sulfation of alcohols and amines. However, the sulfur trioxide is sufficiently deactivated in the complexes that it does not sulfonate aromatics. Furthermore, U.S. Pat. No. 4,490,487 discloses SO₃adducts with imides and the use of the adducts as sulfonating agents for aromatic compounds.

[0007] In all such complexes or adducts, SO₃is deactivated. Some deactivate SO₃enough that they become somewhat unreactive to sulfonate compounds that are relatively resistant to sulfonation. For instance, the sulfur trioxide-pyridine complexes described above have uses limited to the sulfation of alcohols, sugars, polysaccharides, etc.

[0008] It would be desirable to develop new sulfur trioxide complexes in which the sorbent is substantially insoluble to facilitate product isolation, which sulfonate aromatic compounds in a regiospecific manner, and which provide a more active solid sulfonating, sulfating, and sulfamating agent effective in a wider range of sulfonation, sulfation, and sulfamation processes.

[0009] An advantage of the invention is that it can be used industrially for the manufacture of detergents, dye intermediates, and sulfonated oils. For example, detergents can be made by using the SO₃complexes disclosed below for either sulfating alcohols or sulfonating polyalkyl benzenes. Another advantage is that the use of the SO₃complexes provides substantial safety and product isolation advantages over the prior art.

[0010] A process comprises contacting an organic compound with sulfur trioxide under a condition sufficient to effect the sulfonation, sulfation, or sulfamation of the organic compound in which the organic compound is selected from the group consisting of an aromatic compound, alcohol, carbohydrate, amine, amide, protein, and combinations of two or more thereof; and the sulfur trioxide is present in a complex comprising an inorganic support selected from the group consisting of zeolite, silicalite, silica, titanosilicate, borosilicate, clay, and combinations of two or more thereof.

[0011] According to the invention, any organic compounds that can be sulfurized with SO₃can be used. The term “sulfurized” refers to being added a sulfur atom or sulfur-containing functionality. Examples of suitable organic compounds include, but are not limited to, aromatic compounds, alcohols, carbohydrates, amines, amides, proteins, or combinations of two or more thereof.

[0012] The aromatic compound is preferably an activated aromatic compound. An activated aromatic compound has no substituents on the arylene ring or contains at least one electron-donating group on the arylene ring. Examples of electron-donating groups include alkyl, alkoxy, alkylthio, hydroxy, amino, amide such as —NHCOCH₃, phenyl, or combinations of two or more thereof. Specific examples of activated aromatic compounds include, but are not limited to, benzene, naphthalene, biphenyl, toluene, aniline, benzylamine, methylaniline, dimethylaniline, diphenylamine, triphenylamine, anisidines, acetanilide, benzanilide, toluidine, phenol, hydroxymethyl benzene, biphenyl, or combinations of two or more thereof. Many of these compounds such as, for example, aniline, benzylamine, methylaniline, dimethylaniline, toluidine, phenol, and hydroxymethyl benzene can also be sulfated or sulfamated. The presently preferred aromatic compound is toluene. See generally, Everett Gilbert, in “Sulfonation and Related Reactions”, Interscience Publishers, John Wiley and Sons, 1965, p. 65.

[0013] The process of the invention is also useful for selectively sulfonating an aromatic compound. The term “selective or selectively” used herein, unless otherwise indicated, refers to the sulfonation of suitable aromatic compound to produce substantially higher para:ortho ratio. Such selective sulfonation is also referred to as improving “regiospecificity”, which is disclosed in the BACKGROUND OF THE INVENTION section.

[0014] For example, with sulfonation of toluene using the invention process, the toluene sulfonic acid produced has an enhanced para:ortho ratio. Also, sulfonation of biphenyl, biphenyl-4-sulfonic acid production is enhanced. Further for example, selective sulfonation suppresses undesired multiple sulfonations in reactive aromatic compounds such as naphthalene.

[0015] Wishing not to be bound by theory, the mechanism for the regiospecificity is believed to be due to steric restrictions for a reaction within the inorganic support or sorbent pores. The pore dimensions are believed to orient the organic molecule as it contacts the sulfur trioxide. For instance, in the sulfonation of biphenyl, the biphenyl enters the pore constrained or oriented to present the 4-position to the reactant SO₃. The pore dimension creates a constraint against presentation of the 2-position to the sorbed reactant; a constraint that is absent in conventional fluid phase reactions.

[0016] The preparation of p-cresol via the sulfonation of toluene and subsequent alkali metal hydroxide fusion discussed above is an example of sulfonation, which improves regiospecificity of the sorbed sulfur trioxide. The higher ratio of p-toluene sulfonic acid to o-toluene sulfonic acid results in a higher yield of the desired p-cresol and reduced isolation costs. A second example is the sulfonation of biphenyl, to give a sulfonation more regiospecific in the production of the preferred biphenyl-4-sulfonic acid, a source of various 4-substituted biphenyl compounds, including 4-phenylphenol.

[0017] Any alcohols that are substantially liquid or are soluble in an inert solvent under ambient conditions can be used. Examples of suitable alcohols include, but are not limited to, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, octanol, decanol, or combinations of two or more thereof.

[0018] Any carbohydrates that are substantially soluble in a solvent, which is inert to SO₃such as super critical CO₂, can be used in the invention. Examples of suitable carbohydrates include, but are not limited to, glucose, fructose, sucrose, or combinations of two or more thereof.

[0019] Similarly, proteins suitable for use in the invention are substantially soluble in an inert solvent. Examples of suitable proteins also include peptides containing the repeat units of (C(O)N(R))_nwhere R is hydrogen or a hydrocarbyl radical having 1 to about 10 carbon atoms per radical; and n can be a number from 2 to about 30.

[0020] Any amines and amides that can be sulfonated or sulfamated can be used in the invention. Examples of suitable amines include, but are not limited to, methylamine, ethylamine, propylamine, dimethylamine, ethylenediamine, tetraethylenediamine, ethanolamine, isobutylamine, those aromatic amines disclosed above, or combinations of two or more thereof.

[0021] Examples of suitable amides include, but are not limited to, acetamide, acrylamide, benzamide, formamide, propionamide, butyramide, valeramide, stearamide, succinimide, those aromatic amides disclosed above, or combinations of two or more thereof.

[0022] The organic compounds disclosed herein can be used in the presence of a solvent, if needed. A suitable solvent is inert to SO₃and the organic compound. Suitable solvents can include, but are not limited to, methylene chloride, perfluorooctane, 1,2-dichloroethane, nitrobenzene, and liquid or supercritical carbon dioxide, or combinations of two or more thereof.

[0023] Sulfur trioxide can be incorporated into or supported on an inorganic support to produce a SO₃-inorganic support complex (hereinafter referred to as SO₃complex) by any means known to one skilled in the art such as, for example, impregnation, sorption, or combinations thereof. The presently preferred method is a sorption process in which SO₃is sorbed into the support.

[0024] The term “sorbed” used herein refers to a composition of an inorganic support and SO₃exhibiting a partial vapor pressure of SO₃less that of sulfur trioxide itself, e.g., at 24° C. a partial vapor pressure of less than about 0.3 atmosphere (29 kPa).

[0025] The SO₃complexes can be produced by sorbing sulfur trioxide into or onto an inorganic support. Any fluid containing 1 to about 100 weight % SO₃can be used. The fluid can be gas, liquid, or combinations thereof such as nitrogen or SO₃, if pure is SO₃used, and the preferred purity is from about 98 to 100%. Any source of SO₃of adequate purity can be used, typically a container of pure liquid SO₃is used. The SO₃, as vapor or liquid, is passed at a preferred temperature range of 35° C.-90° C. through a bed of an inorganic support to produce a SO₃complex. The inorganic support can be heated up to 150° C. during the sorption or optionally heated and then cooled to increase sorption. The sorption process can be carried out with a suitable inorganic support in any suitable container or vessel inert to SO₃. Steel or stainless steel cylinders, which can be lined with an inert lining such as poly(tetrafluoroethylene), are preferred. Optionally an inert carrier gas may be used to move the sulfur trioxide into the sorbent. In a typical sorption step, for instance, dry nitrogen can be passed through liquid sulfur trioxide maintained at about 20° C. to about 50° C., preferably about 35° C., to provide a stream containing about 50% by volume of SO_3.

[0026] The term “inert fluid or gas” refers to a fluid or gas that is unreactive with SO₃, support, or container, such as nitrogen. When an inert gas is used, the purity of the SO₃is described exclusive of the carrier gas. Optionally SO₃can be sorbed under a positive pressure to accelerate sorption.

[0027] Sulfur trioxide suitable for use in the invention can be incorporated in or supported on an inorganic support. Examples of such inorganic supports include, but are not limited to, zeolites, silicalites, silicas, titanosilicates, borosilicates, clays, aluminophosphates, or combinations of two or more thereof.

[0028] Molecular sieves, both natural and synthetic, are well known in the art. See, e.g., R. Szostak, Molecular Sieves—Principles of Synthesis and Identification, Van Nostrand Reinhold (1989). The inorganic molecular sieves used for incorporating or supporting sulfur trioxide include various silicates (e.g., titanosilicates, borosilicates, silicalites, low alumina-containing zeolites such as mordenite and ZSM-5, and high alumina-containing zeolites such as 5A, NaY and 13X). The preferred molecular sieves are either acidic or are non-acidic silicates.

[0029] Zeolites are available from various sources. A comprehensive listing of zeolites vendors is contained in “CEH Marketing Research Report: Zeolites” by M. Smart and T. Esker with A. Leder and K. Sakota, 1999, Chemical Economics Handbook-SRI International.

[0030] Examples of suitable zeolites include, but are not limited to, mordenite, Y, X, 5A, US-Y, DA-Y, ZSM-5, ZSM-11, beta, L, ferrierite, and clinoptilolite. Examples of suitable titanosilicates are TS-1, TS-2, and Ti-beta. Examples of suitable clays are montmorillonite, kaolin, and talc. Examples of suitable borosilicates are boralite-A, boralite-B, boralite-C, and boralite-D. Examples of suitable aluminophosphates are AIPO₄-5, SAPO-5, AlPO₄-11, SAPO-34, and combinations of two or more thereof. Silicas include precipitated silica, dried silica, diatomaceous earth, silica gels, and fumed silicas. See also Kirk-Othmer Encyclopedia of Chemical Technology, 3^rdedition, volume 115 (John Wiley & Sons, New York, 1991) and W.M. Meier and D.H. Olson, “Atlas of Zeolite Structure Types”, 3^rdedition (Butterworth-Heineman, Boston, Mass. 1992).

[0031] The pore dimensions that control access to the interior of the zeolite are determined not only by the tetrahedra forming the pore opening, but also by the presence or absence of ions in or near the pore. In the case of zeolite A, for example, access can be restricted by monovalent ions, such as Na⁺ or K⁺, which are situated in or near 8-ring openings as well as 6-ring openings. Access is enhanced by divalent ions, such as Ca²⁺, which are situated only in or near 6-ring openings. Thus, the potassium and sodium salts of zeolite A exhibit effective pore openings of about 0.3 nm and 0.4 nm respectively, whereas the calcium salt of zeolite A has an effective pore opening of 0.5 nm. For this application it is important that the pore opening be of sufficient size (at least 0.5 nm) to allow the ingress and egress of sulfur trioxide. The presence or absence of ions in or near the pores, channels, and/or cages can also significantly modify the accessible pore volume of the zeolite for sorbing materials. To maximize capacity, generally protons or small cations are preferred.

[0032] Preferred inorganic supports include high surface area silicas and high silica-containing molecular sieve materials (Si/Al greater than about 5.1) prepared either by synthesis or modification. These materials include silicalite, mordenite, beta, US-Y, DA-Y, ZSM-5, ZSM-11, borosilicates, titanosilicates and the like. The most preferred materials have a Si/Al ratio of at least about 25. Those with Si/Al ratios in the range from about 1 to about 4.4 can also be used. The amount of sulfur trioxide incorporated or supported is at least about 1%, preferably at least about 3%, and most preferably at least about 5% by weight, based on the weight of the supports. The maximum amount is dependent upon the physical structure of the support used, typically in the range from about 40% to about 60% based on the weight of the support.

[0033] Because these inorganic supports are well known to one skilled in the art, the description of which is omitted herein for the interest of brevity.

[0034] Preferably, the support is in a pelletized, beaded, or extruded and chopped form to facilitate gas or liquid flow through. It can be pelletized, beaded, or extruded using a suitable binder, which is stable to exposure to sulfur trioxide and the sorption/desorption conditions, using any means well known to one skilled in the art. Gamma-alumina, silica, and clays are examples of suitable binders.

[0035] The processes of sulfonation and sulfation can be carried out by any means known to one skilled in the art such as that disclosed in detail in “Sulfonation and Sulfation” in The Encyclopedia of Chemical Technology, 4th edition, Wiley Interscience Publication, John Wiley & Sons, New York N.Y., 1997. Both are methods for the introduction of the SO₃group into organic compounds. In sulfonation, the SO₃group is introduced to produce a sulfonate, where the SO₃group is bound directly to a carbon atom, yielding a C—SO₃—X structure. X can be hydrogen, a metal (sulfonate salt), or halogen (sulfonyl halide). Sulfonation of toluene with sulfur trioxide, as an example, yields toluene sulfonic acid isomers. In sulfation, the SO₃group is introduced to produce a sulfate, where the SO₃group is bound though an oxygen atom to a carbon atom, yielding a C—O—SO₃—X group. For example, sulfation of an alcohol with sulfur trioxide yields the alcohol sulfate. Sulfamation is the sulfonation of the R₂NH group in amines, amides, and proteins to form a R₂NSO₃H group.

[0036] The organic compound to be sulfonated, sulfated, or sulfamated can be contacted with a SO₃complex under a condition sufficient to sulfonate, sulfate, or sulfamate the organic compound. The organic compound can be present as a fluid, vapor, liquid, solution, or combinations thereof both, with or without a solvent disclosed above or in a carrier gas such as nitrogen. For example, sulfonation using the SO₃complexes can be carried out by heating the organic compound alone or in an inert solvent with the SO₃complex to effect reaction. Any of the solvents disclosed above (methylene chloride, perfluorooctane, 1,2-dichloroethane, nitrobenzene, and liquid or supercritical carbon dioxide) can be used. The condition can include a temperature in the range of from about 0 to about 100° C., preferably 20 to 60° C., under a pressure that can accommodate the temperature range for a period of time in the range of from about 1 to about 100 hours, preferably 10 to 50 hours. The molar ratio of sorbed SO₃to the organic compound can be in the range from about 0.01:1 to about 100: 1, preferably 1:10 to 10:1. An excess of organic compound can be used to function as a solvent. An excess of the sorbed SO₃can be used where it is desirable to force complete reaction of the organic compound. A ratio of about 1:1 is generally preferred in a continuous pipeline counter-current reactor.

[0037] When the sulfonation, sulfation, or sulfamation is complete, the product can be isolated conventionally. For instance, the residual inorganic sorbent or support is filtered off, washed with water, and the filtrate extracted with sufficient amount of water to remove the sulfonated, sulfated, or sulfamated product. The sulfonated, sulfated, or sulfamated product can be isolated from the combined extracts conventionally by any means known to one skilled in the art and water can be removed to isolate the product.

[0038] This example shows the sulfonation of toluene using a silica gel/SO₃complex.

[0039] A sample (20 g) of silica gel (Grade 952, a silica gel from Davison Division of W. R. Grace, Baltimore Md.) was placed in a quartz tube in a vertically mounted tube furnace, heated by raising the temperature 60° C. per hour to 600° C. and holding at 600° C. (the drying temperature) for 5 hours under flowing nitrogen. The sample was cooled under flowing nitrogen and then transferred to a dry box. This procedure was repeated as necessary and dried material from each run was combined and mixed thoroughly.

[0040] A polytetrafluoroethylene (PTFE) vessel was loaded with 32.6 g (initial weight) of the dried silica gel and heated to 60° C. Distilled SO₃vapor (at 44° C.) was purged over the solid for 2 hours. The solid was then heated to 78° C. under a dry nitrogen purge for 11.5 hours to remove surface bound SO₃. The final weight of the silica gel/SO₃complex was 36.4 g (11.5% weight gain, 10.4% SO₃loading). The silica gel/SO₃complex was then transferred under anhydrous conditions to the thermogravimetric analysis (TGA) where on average it lost 9.4% of its weight between room temperature and 350° C.

[0041] The silica gel/SO₃(5.0 g, containing 7.5 mmol sulfur trioxide, sorbant quantity/mmol SO₃) was added to toluene (50.0 g, substrate/weight) under nitrogen in a 100-ml round bottomed flask equipped with overhead stirrer and condenser. The solution was then heated to 50° C. for 20 hours (reaction temperature/time). The solution was cooled to room temperature and the silica gel support was filtered from the solution. The gel was washed with 10 ml hot water (60° C.) and the toluene was extracted with the same water solution. The water was analyzed by high pressure liquid chromatography (HPLC) and shown to contain 29% yield p-toluenesulfonic acid (TSA), 4% o-TSA, and 0.7% m-TSA (ratio p/o =7.3) for a total 33.7% yield (product % yield) based on the SO₃in the complex.

[0042] Examples 2-11 were carried out similarly as Example 1. Experimental details of all Examples are shown in Table 1. Product details of these Examples are shown in Table 2. In Table 1, the sorbents and sources are as follows. Examples 1, 9, 10, and 11: silica gel (Grade 952, a silica gel from Davison Division of W. R. Grace, Baltimore, Md.); Examples 2 and 8: silicalite (S-115), from Union Carbide, New York, N.Y.; now UOP, Des Plaines, Ill.; Example 3: H-Beta (SiO₂/Al₂O₃=25) (CP 811BL-25, H-beta (SiO₂/Al₂O₃=25), PQ Corp., Valley Forge, Pa. Example 4: high silica Y-zeolite (CBV-901, a H-SDUSY zeolite (SiO₂/Al₂O₃=150) from Zeolyst International, Valley Forge, Pa. Example 5: H-ZSM-5 zeolite (SiO₂/Al₂O₃=150), from Conteka, Leiden, Netherlands, now Zeolyst International, Valley Forge, Pa.); Example 6: H-ZSM-5 zeolite (SiO₂/Al₂O₃=300) from PQ Corp., Valley Forge, Pa., and Example 7: Zeolite 5A (Molecular Sieve Type 5A), from Linde Division, Union Carbide, New York N.Y., now UOP, Des Plaines, Ill.

[0043] This example shows sulfonation of toluene using 98% sulfuric acid

[0044] Sulfuric acid (1.0 g, 10.2 mmol) was added to toluene (50.0 g) under the same conditions as Example 1. The analysis by HPLC showed 26% yield p-toluenesulfonic acid, 11% o-toluenesulfonic acid, and 1.3% m-toluenesulfonic acid (ratio p/o=2.4) for a total yield of 38.3%.

[0045] This example shows sulfonation of toluene using sulfur trioxide.

[0046] Sulfur trioxide (0.6 g, 7.5 mmol, stabilized, 99% from Aldrich, Milwaukee, Wis.) was weighed into a 100-ml round-bottom flask in the dry box. Toluene (50 g) was added to the sulfur trioxide via syringe under an inert atmosphere. The solution was stirred at 50° C. for 22 hours under a nitrogen atmosphere before it was cooled to room temperature. A dark colored oil formed at the bottom of the solution. The toluene and oil layer was extracted with three 10-cc portions of distilled water. The analysis by HPLC showed 28% yield of p-TSA and 5.5% o-TSA (ratio p/o=5.1) for a total yield of 33.5%.

[0047] This example illustrates preparation of silica gel/H₂SO₄complex and demonstrates that sulfonation is not effective with a sulfuric acid complex.

[0048] As described in the literature [F. Chavez et al, Synthetic Communications, 24(16), 2325-2339(1994)], silica gel (10 g), sulfuric acid (1.20 g), and acetone (50 g) were stirred in a 100 ml round bottom flask equipped with condenser, magnetic stirrer, and thermocouple at room temperature for 2 hours. The acetone was removed under vacuum and the silica gel was removed under vacuum at 80° C. The TGA analysis showed 1.44 mmol H₂SO₄/g silica.

[0049] Silica gel/H₂SO₄complex prepared as described above (5.0 g, 7.2 mmol) was added under nitrogen to dried toluene (50 g) in a 100-ml round-bottom flask equipped with a magnetic stirrer, condenser, gas inlet, thermocouple, and heating mantle. The solution was heated to 50° C. for 18 hr., cooled to room temperature, and filtered. The toluene was extracted with three 10-ml portions of water. The insoluble support was placed into the thimble of a Soxhlet Extractor with 100-ml water and extracted for 48 hours. The combined water extracts were analyzed by HPLC and shown to contain 0.9% p-TSA, 0.01% o-TSA, and trace m-TSA for a TSA total yield of 0.9%.

[0050] These examples show that silicalite/SO₃reacts with other solvents such as acetonitrile and tetrahydrofuran.

[0051] Comparative Example D was prepared in the same way as Example 8 using the silicalite/SO₃complex prepared as in Example 2, but used dried acetonitrile (50 g) rather than methylene chloride. The HPLC analysis showed 4.2% p-TSA, 0.52% o-TSA, and 0.1% m-TSA for a total TSA yield of 4.8%. Only small amounts of sulfur (1.6%) were left in the zeolite by x-ray fluorescence elemental analysis, indicating complete reaction of the sulfur trioxide.

[0052] Comparative Example E was prepared in the same way as Example 8 using the silicalite/SO₃complex prepared as in Example 2, but used dried tetrahydrofuran (50 g) rather than methylene chloride. The HPLC analysis showed 4.8% p-TSA, 1.2% o-TSA, and 0.09% m-TSA for a total TSA yield of 6.1%. Only small amounts of sulfur (0.9%) were left in the zeolite by x-ray fluorescence elemental analysis indicating complete reaction of the sulfur trioxide. The gas chromatography/mass spectrometric analysis also showed that tetrahydrofuran was sulfonated.

[0053] The results of the examples and comparative examples are shown in Table 2.

[0054] Table 2 shows substantially enhanced para/ortho ratios for the sulfonation of toluene to toluene sulfonic acid using the invention process.