ALKYLENE GLYCOL ACETATES

TECHNICAL FIELD

[0001] The invention relates to a system and process for efficiently producing alkylene glycol monoacetates and diacetates. Using the system and process disclosed herein, acetaldehyde is oxidized to produce a mixture of peracetic acid, acetic acid, and water. This mixture is used to oxidize an alkylene (e.g. , ethylene), in the presence of a catalyst, to produce alkylene glycol acetates (e.g. , ethylene glycol acetate).

BACKGROUND

[0002] Alkylene glycol acetates are useful for a variety of industrial processes. For example, ethylene glycol diacetate (EGD) is used extensively as a solvent for thermoplastic acrylic coatings, lacquers, resins, and printing inks. EGD also finds use in the manufacturing of perfumes and as a slow release acetic acid source in silicate foundry core-binding applications. Ethylene glycol monoacetate (EGM) also finds use in a variety of applications. For example, EGM finds use as a coolant in low-temperature freezing processes, such as those used for the production of frozen foods. See, e.g. , U.S. Patent No. 4192760, the contents of which are incorporated by reference in their entirety.

[0003] Alkylene glycol acetates are also useful intermediates in various synthetic processes. For example, ethylene glycol diacetate can be converted to vinyl acetate with a conversion rate of about 70% and a selectivity of over 85%. In turn, vinyl acetate may be used as a starting material for manufacturing a wide variety of industrial and consumer products, non-limiting examples of which include paints, adhesives, coatings, insulation, among others.

[0004] For these reasons, conversion of an alkylene to the corresponding vicinal diacetate and/or oc-hydroxy acetate (monoacetate) is a useful synthetic transformation. Therefore, new methods for carrying out such conversions efficiently and with low-cost materials are desirable.

SUMMARY

[0005] Disclosed, in various embodiments, are processes and systems preparing alkylene glycol mono- and di-acetates.

[0006] A process for preparing alkylene glycol mono- and di-acetates, comprises: oxidizing acetaldehyde in an ethyl acetate solvent with an oxygen or oxygen- containing gas in the presence of a first catalyst to produce non-aqueous peracetic acid; removing said ethyl acetate solvent from the peracetic acid by entrainment with water; and concentrating the peracetic acid; and reacting an alkylene with said peracetic acid in the presence of a second catalyst to produce the alkylene glycol mono- and di-acetates.

[0007] A system for preparing alkylene glycol mono- and di-acetates, the system comprises: sources effective to deliver acetaldehyde, oxygen, oxygen-containing gas, and a solvent, respectively, to an explosion suppression chamber; a bubble column reactor in fluid communication with the explosion suppression chamber; and reactant sources in fluid communication with the bubble column reactor; a solvent recovery column, and in communication with the solvent recovery column, a source effective to deliver water to the column, and conduit(s) for recovering solvent and circulating the solvent back to the bubble column reactor; a recovery column equipped with a decanter to recover water and circulate back to recovery column; a catalytic reactor, and in communication with the catalytic reactor, a source effective to deliver an alkylene to the catalytic reactor for oxidation using peracetic acid; and a separation unit comprising separate outlets and conduits for removal of product(s) from acetic acid and for recycling of byproducts; wherein the bubble column reactor comprises an outlet and conduits in communication with the product recovery column, the product recovery column comprises an outlet and conduits in communication with the catalytic reactor, and the catalytic reactor comprises an outlet and conduits in communication with the separation unit.

[0008] These and other features and characteristics are more particularly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The following is a brief description of the drawings wherein like elements are numbered alike and which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same

[0010] FIG. 1 is a flow chart showing an exemplary system for carrying out the disclosed sequence of reactions.

DETAILED DESCRIPTION

[0011] The invention provides a process and system for preparing alkylene glycol mono- and diacetates by reaction of an alkylene with peracetic acid (PAA, also known as peroxyacetic acid), and a catalyst. The peracetic acid is produced via a nonaqueous route, by oxidation of acetaldehyde with an oxygen-containing gas (e.g. , purified oxygen and/or air) in the presence of the solvent ethyl acetate (EtOAc) and a catalyst. The system and process provide access to alkylene glycol mono- and diacetates using low-cost materials (acetaldehyde, oxygen/air, ethyl acetate, plus catalysts) with good selectivity and minimal production of byproducts, where the byproducts that are produced (such as acetic acid) can be recycled to provide additional starting material (i.e., acetaldehyde).

[0012] In one aspect, the invention provides a process for preparing alkylene glycol mono- and di-acetates, the process comprising the steps of (a) oxidizing acetaldehyde in an ethyl acetate solvent with an oxygen-containing gas in the presence of a catalyst (non-aqueous); (b) removing said ethyl acetate solvent by entrainment with water, effective to produce a peracetic acid product mixture containing predominantly peracetic acid with smaller amounts of acetic acid and water (this small amount of water helps in a following reaction to convert feedstock to glycol acetates) and (c) reacting an alkylene with the peracetic acid product mixture in the presence of a catalyst. Optionally, the process may further comprise conversion of the acetic acid in the product of (c) to acetaldehyde and recycling the acetaldehyde to step (a). The non-aqueous production of PAA gives superior control, not only to achieve high concentration of PAA, but also to selectively produce mono- or di- ethyl glycol acetates via a secondary reaction.

[0013] In one aspect, the invention provides a process for preparing alkylene glycol mono- and di-acetates. The process includes oxidizing acetaldehyde in an ethyl acetate solvent with oxygen or oxygen-containing gas in the presence of a catalyst. Optionally, a solvent recovery column is used to remove the ethyl acetate solvent by entrainment with water, thereby producing a peracetic acid product mixture containing predominantly peracetic acid with smaller amounts of acetic acid and water. It is useful to add a stabilizer at this stage to stabilize the PAA, as well as a catalyst (e.g., tri-octyl phosphate). The peracetic acid product is further reacted with an alkylene in the presence of a catalyst. Optionally, the process may include the recovery of acetic acid in the peracetic acid product mixture and conversion to acetaldehyde for use in producing the peracetic acid, as described above.

[0014] In another aspect, the invention provides a system for preparing alkylene glycol mono- and di-acetates. In certain implementations of the invention, the system includes a bubble column reactor equipped with reactant sources that are in fluid communication with the reactor. The sources deliver acetaldehyde, an oxygen-containing gas, and a solvent, respectively, to the bubble column reactor. A small portion of the reaction mixture may be circulated as secondary control on reactor temperature, if desired. The system further includes a solvent recovery column and a water sources that delivers water to the column. The system is also equipped with one or more conduits for recycling solvent, such as ethyl acetate, back to the bubble column reactor. If desired, a film- or tray-type evaporator may be attached downstream of the solvent recovery column in order to get rid of dissolved gases and acetaldehyde. The system includes a catalytic reactor and an alkylene source that delivers an alkylene (e.g., ethylene) to the catalytic reactor as well as a source for adding other materials, such as water. The system may include a separation unit, which is provided with separate outlets and conduits for removal of product(s) and for recycling of byproduct. Optionally, the system further includes, in fluid communication with the conduit for recycling, a hydrogenation reactor effective to convert acetic acid to acetaldehyde, and conduits effective to transfer the acetaldehyde to the bubble column reactor.

[0015] The oxidation of acetaldehyde to peracetic acid can be catalyzed by UV radiation, by ozone, by metal salts, predominantly cobalt and iron compounds, such as cobalt or iron acetate (see e.g. , GB Patent No. 1374297), or by strong acids, as described, for example, in U.S. Patent No. 4,024, 180. See also H. Klenk et ah , "Peroxy Compounds, Organic", in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley- VCH Verlag GmbH & Co., pp. 325-260. Non-limiting examples of preferred catalysts for the oxidation of acetaldehyde to peracetic acid include cobalt acetate, tri-octyl phosphate, alkaline-metal supported zeolites, and alkaline-earth-metal supported zeolites.

[0016] The oxidation of acetaldehyde to peracetic acid is preferably carried out with ethyl acetate as a solvent. After the oxidation reaction is complete, the ethyl acetate solvent is removed to form a mixture that contains predominantly peracetic acid with smaller amounts of acetic acid and water. The peracetic acid product mixture preferably contains peracetic acid at a concentration of 51% to 99%, 55% to 95%, 60% to 85%, 65% to 80%, or 70% to 75% by weight, with the remainder predominantly acetic acid and water. Optionally, the peracetic acid product mixture may contain between about 2% and about 20% by weight water. In general, any known method that is appropriate for the removal of the ethyl acetate solvent may be used. For instance, the removal of the ethyl acetate solvent may be accomplished by entrainment with water, as described herein.

[0017] The peracetic acid/acetic acid/water mixture is reacted with an alkylene in the presence of an epoxidation catalyst in order to form the desired alkylene glycol mono- and diacetates. Without wishing to be limited by theory, it is believed that the reaction proceeds via formation of a three-member cyclic ether known as an epoxide. In its broadest implementation, the invention contemplates the use of any alkylene that has a double bond available for reaction with peracetic acid. If desired, the alkylene may be a C ₂ - Ci ₂ alkylene, C ₂ - Cio alkylene, C ₂ - Cg alkylene, or C ₂ - C ₆ alkylene. In certain cases, the alkylene may be a C ₂ , C ₃ , C ₄ , Cs _, or C ₆ alkylene. In one embodiment, the alkylene is ethylene. The chemical reaction sequence, where the alkylene is ethylene, can thus be represented schematically as follows:

EtOAc

[0018] In certain implementations, a linear alkylene is reacted with the peracetic acid/acetic acid/water mixture. In most cases, the linear alkylene chosen will contain a single double bond, although the use of linear alkylenes with two or more double bonds are expressly contemplated by the invention. In certain instances, a branched alkylene may be used in addition to, or instead of, a linear alkylene. When a branched alkylene is used, it is often desirable to choose one in which the branching hydrocarbon groups are sufficiently small or sufficient far from the C=C / peracetic acid reaction site in question that they do not provide any significant steric hinderance to the reaction. The invention also contemplates the use of mixtures of alkylenes.

[0019] Optionally, the alkylene oxidation reaction employs a catalyst. In certain cases, the catalyst is an osmium catalyst, such as Os0 ₄ , or a Pd(II) (palladium) catalyst. See, for example, S.D.R. Christie et al., Synthesis 2008, 1325-1341; KH Jensen et al., Org. Biomol. Chem., 2008, 6, 4083-4088. If desired, manganese (II) catalysts can be used to form an epoxide intermediate. See, e.g., Garcia-Bosch, A. Company, X. Fontrodona, X. Ribas, M. Costas, Org. Lett., 2008, 10, 2095-2098; A. Murphy, G. Dubois, T. D. P. Stack, J. Am. Chem. Soc, 2003, 125, 5250-5251. As will be appreciated by those of skill in the art, the epoxide intermediate can be ring opened (e.g., under acidic conditions) to produce the desired alkylene glycol mono- and diacetates. Particularly preferred catalysts for alkylene oxidation in the current process include organometallic Pd- based sulfonated ketones, Pd(OAc) ₄ , Pd(OAc) ₂ .

[0020] The invention provides systems for preparing alkylene glycol mono- and di-acetates using the method described herein. In certain implementations, the system comprises a bubble column reactor equipped with reactant sources that are in fluid communication with the reactor. The system may also comprise a coolant circulation jacket and a high-speed motor drive stirrer to reduce the formation of potentially explosive gas pockets in reaction zone and to improve gas-liquid interaction at the same time. Optionally, instead of injecting acetaldehyde and oxygen with recycling stream directly into the reactor, these streams are pre-mixed at an appropriate ratio by intermediate mixer, which helps to minimize the potential for explosion.

[0021] A non-limiting example of such a system is provided in FIG. 1. Feed acetaldehyde 10 and oxygen (or an oxygen-containing gas, such as air) 11, is charged to explosion suppression chamber 1, where they are mixed in appropriate fashion with recycle stream 20, which is a combination of stripping streams 27, 24, 43; and are injected at 12 to bubble column reactor 2. The reactor 2 is jacketed 13 for cooling, and equipped with motor driven agitator 15 to achieve homogeneous mixture of gases and liquid in order to enhance oxygen absorption. The reactor 2 material is circulated through line 16 using pump 17 attached to the cooler 18 to control reactor temperature (optional to the scale of the reactor). The product of the reactor 2 is transferred via line 19 to a constant liquid level separator 3 equipped with heater 21. Stripping gases 43 are recycled back to the reactor 2 and product 22 is sent to solvent recovery column 4 with injection 23 of stabilizer / inhibitor / high boiling inert liquid. In certain preferred embodiments, the invention uses the solvent ethyl acetate 14, a homogeneous or heterogeneous catalyst (e.g., metal salt, such as cobalt or iron acetate) an operating conditions as described herein for per- acetic acid production.. Use of bubble column reactors is known in the art and described, for example, in U.S. Patent No. 3,963,773; 1,049,159; see also "Bubble Column Reactors" in Chemical Reactor Modeling, HA Jakobsen, Springer, 2008, pp 757-806. The bubble column 2 is typically operated at a pressure of 0.05 MegaPascals (MPa) to 6 MPa (0.5 to 60 bar), preferably 0.075 MPa to 4 MPa (0.75 to 40 bar); and most preferably 0.1 MPa to 2 MPa (1 to 20 bar). A useful temperature is in the range of 40 - 100 °C, more preferably 45 - 90 °C, and most preferably 50 - 80 °C. The ethyl acetate solvent 14 used in connection with the oxidation of the acetaldehyde may be fresh solvent, but in certain preferred implementations is comprised of at least some solvent that is recovered downstream of the bubble column reactor. For example, the product of the bubble column reactor 2, which includes PAA and some acetic acid, acetaldehyde, catalyst, inhibitor, may be sent to solvent recovery column 4, where ethyl acetate striped off 25 and heated in heater 26 is recovered by entrainment with water 24; the recovered ethyl acetate can then be recycled 27 as indicated in FIG. 1. Preferably, at least some of the water is cycled back

28 to the solvent recovery column 4 from decantation unit 5.

[0022] The product 29 exiting the solvent recovery column 4 contains predominantly PAA, with lesser amounts of acetic acid and water. Preferably, the product

29 contains at least 75% PAA by weight and at least 2% water by weight, the remainder being predominantly acetic acid with stabilizer (for example poly phosphoric acid). For example, the mixture may contain between about 70% and 85% by weight peracetic acid and the remainder predominantly acetic acid and water. In selected embodiment, the peracetic acid product mixture contains between about 2 - 20% by weight water.

[0023] Reagent mixture 29 is further refined by passing through film/plate type evaporator 6 to get concentrated PAA 31 and dissolved gases with some water are recycled 30 to recovery column 4. Concentrated PAA 31 is used directly for oxidation of an alkylene 32, such as ethylene, in catalytic reactor 7. Similar to reactor 2, in reactor 7, a portion of reactor mixture is circulated 35 by pump 37 using heater 36 having minimum time lag. The reactor 7 typically operates at about 0.1 MPa - 1 MPa (1 - 10 bar) and about 20 - 40°C. The oxidation of olefins can be carried out in the absence or the presence of oxygen. Effluent 34, containing unreacted alkylene, can be recycled to reactor 7 or used in other downstream units as feedstock. Alkylene oxidation product mixture 38, containing the desired products diacetoxy alkylene glycol and monoacetoxy alkylene glycol, is separated from acetic acid 40 in separation unit 8. The ratio of alkylene glycol monoacetate to alkylene glycol diacetate in the product 39 is typically about 10: 1 to about 1: 10, or about 5: 1 to about 1:5, or about 2: 1 to about 1:2. The amount of monoacetate can be increased if desired by adjusting appropriate the amount of water using stream 33.

[0024] With further reference to FIG. 1, the recovered acetic acid 40 can be converted back to acetaldehyde in unit 9 by hydrogenation 41 and recycled 42 to bubble column reactor 2.

[0025] These and other applications and implementations will be apparent in view of the disclosure. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. While the present device, system, and method have been described with reference to several embodiments and uses, and several drawings, it will be appreciated that features and variations illustrated or described with respect to different embodiments, uses, and drawings can be combined in a single embodiment.

[0026] The process and system disclosed herein includes at least the following embodiments:

[0027] Embodiment 1: A process for preparing alkylene glycol mono- and di- acetates, comprises: oxidizing acetaldehyde in an ethyl acetate solvent with an oxygen or oxygen-containing gas in the presence of a first catalyst to produce non-aqueous peracetic acid; removing said ethyl acetate solvent from the peracetic acid by entrainment with water; and concentrating the peracetic acid; and reacting an alkylene with said peracetic acid in the presence of a second catalyst to produce the alkylene glycol mono- and di- acetates.

[0028] Embodiment 2: The process of Claim 1, wherein the ratio of alkylene glycol monoacetate to alkylene glycol diacetate is about 10: 1 to about 1: 10.

[0029] Embodiment 3: The process of Claim 1 or Claim 2, wherein the first catalyst is selected from iron acetate, cobalt acetate, and an alkaline-metal or alkaline earth metal support zeolite.

[0030] Embodiment 4: The process of any of Claims 1 - 3, wherein the second catalyst is an alkylene oxidation catalyst that comprises osmium, palladium, or manganese. [0031] Embodiment 5: The process of Claim 4, wherein the alkylene oxidation catalyst is selected from an organometallic Pd based sulfonated ketone, Pd(OAc) ₄ , and Pd(OAc) ₂ .

[0032] Embodiment 6: The process of any of Claims 1 - 5, wherein said peracetic acid product mixture contains between about 75% and about 95% by weight peracetic acid.

[0033] Embodiment 7: The process of any of Claims 1 - 6, wherein said peracetic acid product mixture contains about 2% to about 20% by weight water.

[0034]

[0035] Embodiment 8: The process of any of Claims 1 - 7, wherein said alkylene is a C ₂ - C ₁₂ alkylene.

[0036] Embodiment 9: The process of Claim 8, wherein said alkylene is a C ₂ - C ₈ alkylene.

[0037] Embodiment 10: The process of Claim 8, wherein said alkylene is ethylene.

[0038] Embodiment 11: The process of any of Claims 1 - 10, wherein said alkylene is a linear alkylene.

[0039] Embodiment 12: The process of any of Claims 1 - 11, wherein said alkylene is a branched alkylene.

[0040] Embodiment 13: The process of any of Claims 1 - 12, further comprising, following reacting an alkylene with said peracetic acid in the presence of a second catalyst to produce the alkylene glycol mono- and di-acetates, conversion of said acetic acid to acetaldehyde.

[0041] Embodiment 14: The process of Claim 13, wherein the acetaldehyde is used as a reagent when oxidizing acetaldehyde in an ethyl acetate solvent with an oxygen or oxygen-containing gas in the presence of a first catalyst to produce non-aqueous peracetic acid.

[0042] Embodiment 15: A system for preparing alkylene glycol mono- and di- acetates, the system comprises: sources effective to deliver acetaldehyde, oxygen, oxygen-containing gas, and a solvent, respectively, to an explosion suppression chamber; a bubble column reactor in fluid communication with the explosion suppression chamber; and reactant sources in fluid communication with the bubble column reactor; a solvent recovery column, and in communication with the solvent recovery column, a source effective to deliver water to the column, and conduit(s) for recovering solvent and circulating the solvent back to the bubble column reactor; a recovery column equipped with a decanter to recover water and circulate back to recovery column; a catalytic reactor, and in communication with the catalytic reactor, a source effective to deliver an alkylene to the catalytic reactor for oxidation using peracetic acid; and a separation unit comprising separate outlets and conduits for removal of product(s) from acetic acid and for recycling of byproducts; wherein the bubble column reactor comprises an outlet and conduits in communication with the product recovery column, the product recovery column comprises an outlet and conduits in communication with the catalytic reactor, and the catalytic reactor comprises an outlet and conduits in communication with the separation unit.

[0043] Embodiment 16: The system of Claim 15, further comprising, in communication with said conduit for recycling of byproduct, a hydrogenation reactor effective to convert acetic acid to acetaldehyde, and conduit(s) for transferring said acetaldehyde to the bubble column reactor.

[0044] Embodiment 17: The system of Claim 15 or Claim 16, wherein the bubble column reactor comprises a packed bed bubble column reactor with one or more distributors.

[0045] Embodiment 18: The system of Claim 17, wherein the bubble column reactor is configured for stirring, pressurizing, and/or internal recycling with a cooler, and optionally is jacketed.

[0046] In general, the invention may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objectives of the present invention. The endpoints of all ranges directed to the same component or property are inclusive and independently combinable (e.g., ranges of "less than or equal to 25 wt%, or 5 wt% to 20 wt%," is inclusive of the endpoints and all intermediate values of the ranges of "5 wt% to 25 wt%," etc.). Disclosure of a narrower range or more specific group in addition to a broader range is not a disclaimer of the broader range or larger group. "Combination" is inclusive of blends, mixtures, alloys, reaction products, and the like. Furthermore, the terms "first," "second," and the like, herein do not denote any order, quantity, or importance, but rather are used to denote one element from another. The terms "a" and "an" and "the" herein do not denote a limitation of quantity, and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. "Or" means "and/or." The suffix "(s)" as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the film(s) includes one or more films).

Reference throughout the specification to "one embodiment", "another embodiment", "an embodiment", and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

[0047] The modifier "about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). The notation "+ 10%" means that the indicated measurement can be from an amount that is minus 10% to an amount that is plus 10% of the stated value. The terms "front", "back", "bottom", and/or "top" are used herein, unless otherwise noted, merely for convenience of description, and are not limited to any one position or spatial orientation. "Optional" or "optionally" means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not. Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs. A "combination" is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0048] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference

[0049] While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.

[0050] I/we claim: