WO2024110798A1 - Method for reprocessing polytetramethylene ether glycol - Google Patents

Abstract

The disclosed process relates to a process for conversion of polytetramethylene ether glycol to tetrahydrofuran, comprising the steps of: a) introducing a stream comprising polytetramethylene ether glycol to a strong acid catalyst capable of converting polytetramethylene ether glycol to tetrahydrofuran and water; b) operating said process in a reactor under operating conditions sufficient to effect acid-catalyzed depolymerization of polytetramethylene ether glycol to tetrahydrofuran and water; and c) recovering the tetrahydrofuran.

Description

METHOD FOR REPROCESSING POLYTETRAMETHYLENE ETHER GLYCOL

RELATED APPLICATIONS

[0001] This international PCT patent application claims priority to United States Provisional Patent Application No. 63/426,794, filed on November 21, 2022, which is incorporated herein by reference in its entirety.

RELEVANT FIELD

[0002] The disclosed process relates to a process for converting polytetramethylene ether glycol (“PTMEG”) to tetrahydrofuran (“THF”) in the presence of a strong acid catalyst.

BACKGROUND

[0003] Polytetramethylene ether glycol (PTMEG) is a major component in a wide variety of polyurethanes, polyesters, and polyamide elastomers. PTMEG also reacts with isocyanates or organic acids to form elastomers. Primary end-uses include spandex, castable polyurethanes, thermoplastic polyurethanes, polyurethane coatings and sealants. PTMEG is a polymer of tetrahydrofuran (THF), made via THF polymerization and methanolysis reactions.

[0004] Current processes for manufacturing THF use a reaction mixture comprising 1,4- butanediol (“BDO”) in the presence of an acid catalyst in liquid form, for example, sulphuric acid, in a distillation reaction zone. This acid catalyst is necessary to accomplish dehydration of the BDO and ring closure. However, the presence of this acid catalyst has destructive effects on process components.

[0005] As an alternative to the use of an acid catalyst such as sulphuric acid, US2016214952A1 and its Chinese counterpart CN105531266B in the name of the present applicant disclose an improved process for manufacturing THF from a reaction mixture comprising BDO in the presence of a strong acid catalyst in a reaction vessel comprising a distillation reaction zone, wherein the acid catalyst is suspended in a vapor-rich region in the distillation reaction zone. This improved process advantageously allows for cheaper process vessels and dramatically reduces tar formation.

[0006] In downstream processing reactions, THF may be subsequently converted to polytetramethylene ether acetate (“PTMEA”) by ring opening polymerization with a superacid (typically an acid that is stronger than the acid strength of 100% sulphuric acid), allowing for a low residence time. As shown in Figure IB, the product molecular weight is controlled by the addition of acetic anhydride which, coupled with the low residence time, allows for quick transitions between product grades. The PTMEA is then converted to PTMEG in a reactive distillation column by strong base transesterification in a methanolysis reaction, as shown in Figure 1C.

[0007] The resulting PTMEG polymer contains molecules of varying chain lengths, with a broad molecular weight distribution. The typical average molecular weight distribution is between 150 and 3000 daltons. Different end-uses of PTMEG require PTMEG with different average molecular weight distributions. For example, some applications require PTMEG with an average molecular weight distribution of only 250 daltons (Mn~250), whilst other applications require PTMEG with an average molecular weight distribution of 2000 daltons (Mn~2000). Process conditions can be altered to result in synthesis of PTMEG with different defined average molecular weight distributions.

[0008] For a given PTMEG polymer with a particular average molecular weight distribution, the molecular weight of the oligomers therein may still vary considerably. If the polymer contains too high a percentage of short chain oligomers, it can have a harmful and detrimental effect on the properties of the end product.

[0009] In addition, sometimes the step of conversion of THF to PTMEA (see Figure IB) inadvertently results in formation of PTMEA with an incorrect molecular weight, typically greater than the required average molecular weight, such that PTMEG derived from this PTMEA falls outside the narrow molecular weight distribution that is ideal for use in the target downstream spandex and polyurethanes markets. Whole batches of the PTMEG resulting from this PTMEA are rarely reprocessed, and consequently are wasted.

[0010] Accordingly, in light of current practices, there is a need for processes that reprocess the PTMEG that falls outside the desired average molecular weight distributions.

SUMMARY

[0011] The embodiments disclosed herein provide an improved process for conversion of polytetramethylene ether glycol to tetrahydrofuran. Disclosed herein are methods for introducing a stream comprising polytetramethylene ether glycol to a strong acid catalyst capable of converting polytetramethylene ether glycol to tetrahydrofuran and water; operating said process in a reactor under operating conditions sufficient to effect acid-catalyzed depolymerization of polytetramethylene ether glycol to tetrahydrofuran and water; and recovering the tetrahydrofuran.

[0012] There exists a known problem that sometimes the step of conversion of THF to PTMEA inadvertently results in PTMEG of an incorrect molecular weight, such that PTMEG derived from this PTMEA falls outside the narrow molecular weight distribution that is required for use in the downstream spandex and polyurethanes markets. There exists a need to provide a solution to reprocess this PTMEG that falls outside the desired molecular weight distribution. [0013] Embodiments herein provide solutions to overcome this problem through the provision of a strong acid catalyst which can be used in certain reaction conditions to depolymerize PTMEG to THF and water. Such a strong acid catalyst is known to convert BDO to THF and water (see Vaidya et al, Applied Catalysis A: General 242 (2003), 321-328, and U.S. Patent Application Publication No. 2016/0214952A1 and its Chinese counterpart CN105531266B in the name of the present applicant which disclose an improved process for manufacturing THF from a reaction mixture comprising BDO in the presence of a strong acid catalyst). However, surprisingly, there have been no suggestions or prior motivations to use the strong acid catalyst in an alternative reaction to convert polytetramethylene ether glycol to tetrahydrofuran and water.

[0014] In a first aspect herein, there is provided a process for conversion of polytetramethylene ether glycol to tetrahydrofuran, comprising the steps of: a) introducing a stream comprising polytetramethylene ether glycol to a strong acid catalyst capable of converting polytetramethylene ether glycol to tetrahydrofuran and water; b) operating said process in a reactor under operating conditions sufficient to effect acid-catalyzed depolymerization of polytetramethylene ether glycol to tetrahydrofuran and water; and c) recovering the tetrahydrofuran.

[0015] In an embodiment of the process, the strong acid catalyst is a solid catalyst.

[0016] In an embodiment of the process, the solid catalyst is selected from the group consisting of a polymer-based acid resin, a mineral-based supported acid catalyst and combinations thereof.

[0017] In an embodiment of the process, the solid catalyst is an acidic resin catalyst.

[0018] In an embodiment of the process, the acidic resin catalyst has an acid equivalency of between 1 and 10.

[0019] In an embodiment of the process, the strong acid catalyst has a residence time of between 5 minutes and 60 minutes, and preferably between 10 minutes and 30 minutes. [0020] In an embodiment of the process, the strong acid catalyst is contained within a fixed bed or a fluidized bed within the reactor.

[0021] In an embodiment of the process, the strong acid catalyst is slurried.

[0022] In an embodiment of the process, the ratio of solid catalyst to reactor liquid inventory is 5wt% to 90wt%, and preferably 10wt% to 30wt%.

[0023] In an embodiment of the process, the reactor comprises one or more tubular-shaped vessels.

[0024] In an embodiment of the process, the reactor is operated at a temperature of from 80°C to 150°C, and preferably 90°C to 120°C.

[0025] In an embodiment of the process, the reactor is operated at 0.3 bara to 5 bara, preferably atmospheric pressure.

[0026] In an embodiment of the process, the tetrahydrofuran and water produced is 90±10/99.9±0.1, weight/weight, tetrahydrofuran/water.

[0027] In an embodiment of the process, there is a further step (d) of recycling at least a portion of the tetrahydrofuran into upstream processing reactions for synthesis of polytetramethylene ether glycol.

[0028] In an embodiment of the process, step (d) recycles at least a portion of the tetrahydrofuran as a feed into the tetrahydrofuran polymerization stage for converting tetrahydrofuran to polytetramethylene ether acetate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present application is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements and in which: [0030] Figure l is a representation of the reactions showing conversion of BDO to THF (Figure 1 A); THF to PTMEA (Figure IB) and PTMEA to PTMEG (Figure 1C).

[0031] Figure 2 is a schematic representation of a configuration of a distillation process.

[0032] Figure 3 is a graphical representation of the THF/water evolution rate as a function of temperature at a particular catalyst weight fraction with PTMEG having an average molecular weight distribution of 2000 daltons.

[0033] Figure 4 is a graphical representation of the THF/water evolution rate as a function of temperature at a particular catalyst weight fraction with PTMEG having an average molecular weight distribution of 250 daltons. [0034] Figure 5 is a graphical representation of the THF/water evolution rate as a function of catalyst weight fraction temperature at a particular reaction temperature with PTMEG having an average molecular weight distribution of 2000 daltons.

[0035] Figure 6 is a graphical representation of the THF/water evolution rate as a function of catalyst weight fraction temperature at a particular reaction temperature with PTMEG having an average molecular weight distribution of 250 daltons.

DETAILED DESCRIPTION

[0036] [0007] The detailed description that follows describes exemplary embodiments and the features disclosed are not intended to be limited to the expressly disclosed combination(s). Therefore, unless otherwise noted, features disclosed herein may be combined together to form additional combinations that were not otherwise shown for purposes of brevity. Unless otherwise defined, all scientific and technical terms used herein are intended to have the same meaning as would be understood by a person of skill in the art to which this disclosure relates. The materials, methods, and examples are illustrative only and not intended to be limiting. The word “comprise” and variations such as "comprises" or "comprising" are understood to mean the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0037] Unless specifically stated otherwise or obvious from the context used herein, the terms “about” and “approximately” are understood as lying within a range of normal tolerances in the art, for example within 2 standard deviations of the mean. “About” and “approximately” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”

[0038] The term "PTMEG", as used herein, means polytetramethylene ether glycol (CAS No. 25190-06-1). PTMEG is also known as polyoxybutylene glycol or poly(tetrahydrofuran) or PTMG. PTMEG is represented by a molecular formula; H(OCH2CH2CH2CH2)nOH ((C4H8O)n), wherein n is a numerical value between 1 to 100. [0039] The term "PTMEA", as used herein, means the diacetate of polytetramethylene ether glycol (CAS No. 26248-69-1) represented by the formula (C4H8O)n, also known as polytetramethylene ether acetate.

[0040] The term “BDO” as used herein represents 1,4-butanediol, also known as 1,4-butylene glycol, having the formula HOCH2CH2CH2CH2OH (CAS No. 110-63-4).

[0041] The term “THF” as used herein represents tetrahydrofuran, also known as cyclotetramethylene oxide, represented by the formula C4H8O. Percentages used herein are in weight % unless otherwise indicated.

[0042] The term “PBAT”, as used herein, means polybutylene adipate terephthalate (CAS No. 60961-73-1).

[0043] The present disclosure provides, in a first aspect, a process for conversion of polytetramethylene ether glycol to tetrahydrofuran, comprising the steps of: a) introducing a stream comprising polytetramethylene ether glycol to a strong acid catalyst capable of converting polytetramethylene ether glycol to tetrahydrofuran and water; b) operating said process in a reactor under operating conditions sufficient to effect acid-catalyzed depolymerization of polytetramethylene ether glycol to tetrahydrofuran and water; and c) recovering the tetrahydrofuran.

[0044] In upstream processing reactions for synthesis of PTMEG, BDO is converted to THF in a ring closure reaction (Figure 1A), with subsequent conversion of THF to PTMEA Figure IB) and finally to PTMEG (Figure 1C).

[0045] Current processes for converting BDO to THF deploy an acid catalyst in liquid form, for example, sulphuric acid, in a distillation reaction zone. This acid catalyst is necessary to accomplish dehydration of the BDO and ring closure. However, the presence of this acid catalyst necessitates the use of high-grade materials to avoid corrosion of the process vessels due to the strong acidity of the hot process liquor. Further, this process disadvantageously generates an accumulating high concentration of an acidic black viscous tar which represents a yield loss and operational problems.

[0046] However, literature teaches that the same chemistry (i.e. dehydration of the BDO and ring closure) can be carried out with a solid acid catalyst (see Vaidya et al, Applied Catalysis A: General 242 (2003), 321-328), wherein the reaction takes place on the surface of the catalyst rendering the mixture pH neutral. [0047] U.S. Patent Application Publication No. 2016/0214952A1 and its Chinese counterpart CN105531266B in the name of the present applicant disclose an improved process for manufacturing THF from a reaction mixture comprising BDO in the presence of a strong acid catalyst in a reaction vessel comprising a distillation reaction zone, wherein the acid catalyst is suspended in a vapor-rich region in the distillation reaction zone. This improved process advantageously allows for cheaper process vessels and dramatically reduces tar formation.

[0048] There has been neither any motivation nor suggestion to use this strong acid catalyst in any other reaction step as depicted in Figure IB or 1C, either a forward or reverse reaction step. [0049] Once formed, THF is converted to polytetramethylene ether acetate (“PTMEA”) by ring opening polymerization with a superacid (typically an acid that is stronger than the acid strength of 100% sulphuric acid), allowing for a low residence time (see Figure IB). The product molecular weight is controlled by the addition of acetic anhydride which, coupled with the low residence time, allows for quick transitions between product grades. The PTMEA is then converted to PTMEG in a reactive distillation column by strong base transesterification in a methanolysis reaction.

[0050] The PTMEG polymer contains molecules of varying chain lengths, with a broad molecular weight distribution. The typical average molecular weight distribution is between 150 and 3000 daltons. Different end-uses of PTMEG require PTMEG with different average molecular weight distributions. For example, some applications require PTMEG with an average molecular weight distribution of only 250 daltons (Mn~250), whilst other applications require PTMEG with an average molecular weight distribution of 2000 daltons (Mn~2000). Process conditions can be altered to result in synthesis of PTMEG with different defined average molecular weight distributions.

[0051] For a given PTMEG polymer with a particular average molecular weight distribution, the molecular weight of the oligomers therein may still vary considerably. If the polymer contains too high a percentage of short chain oligomers, it can have a harmful and detrimental effect on the properties of the end product.

[0052] After removal of the methanolysis catalyst from the PTMEG, the oligomers and low molecular weight fractions are removed from the product in a narrowing step deploying at least one short-path distillation evaporator (as previously reported, for example, as described in US5282929A). The final product has a narrower molecular weight distribution that is better suited for use in the downstream spandex and polyurethanes markets. The low molecular weight fractions removed from the product in this narrowing step are typically reprocessed in the BDO to THF ring-closure reaction step (as shown in Figure 1 A) reactor at around 5wt% on BDO basis with sulphuric acid.

[0053] In addition, as in any continuous manufacturing process, off-spec material can occasionally be generated as a consequence of, for example, process upset, instrument failure/drift such that the color or the molecular weight may not be correct. Therefore, occasionally the step of conversion of THF to PTMEA (see Figure IB) inadvertently results in formation of PTMEA with an incorrect molecular weight, typically greater than the required average molecular weight, such that PTMEG derived from this PTMEA falls outside the narrow molecular weight distribution that is ideal for use in the target downstream spandex and polyurethanes markets. Sometimes this material can be blended back into the process but often is considered to be waste material.

[0054] In the present disclosure, it was unexpectedly found that the strong acid catalyst that can be used in an improved process in a reaction mixture for converting BDO to THF can also be used to depolymerize PTMEG to THF (and water). Specifically, this strong acid catalyst can be advantageously used in a reprocessing step to depolymerize (i) fractions of PTMEG that have been removed in one or more narrowing steps and (ii) fractions of off-spec PTMEG, typically with an average molecular weight greater than that required for a specific end-use; and convert these fractions of PTMEG to THF.

[0055] As previously mentioned, the fractions of PTMEG that have been removed in one or more narrowing steps are currently subsequently reprocessed in the BDO to THF ring-closure reaction step (as shown in Figure 1 A). This reduces, or even eliminates, the current wastage of PTMEG that falls outside the range of desired molecular weights.

[0056] However, growing interest in the biodegradable polymer polybutylene adipate terephthalate (“PBAT”) for environmental conservation reasons has led to an increase in the number of manufacturing plants producing PBAT. PBAT plants produce THF as a by-product and as a consequence, there are increasing quantities of THF from sources other than from BDO manufacturing plants. This greater availability of THF has opened up options for using the THF as a stream for feeding into THF polymerization processes (see Figure IB) to produce PTMEG, instead of the traditional routes to make PTMEG from BDO.

[0057] The fractions of PTMEG that have been removed in one or more narrowing steps and which are currently reprocessed in the BDO to THF ring-closure reaction step (as shown in Figure 1A) may be recycled back into the THF polymerization processes (at Figure IB) to produce PTMEG. As more THF is produced in PBAT plants, this shorter and therefore more economical route to produce PTMEG is becoming increasingly desirable compared to the longer route starting from BDO.

[0058] In some embodiments, the acid catalyst can be in the forms of solid, semi-solid, slurried and/or of gel consistency. In one embodiment, the acid catalyst is a solid catalyst. In one embodiment, the solid catalyst is a strongly acidic ion exchange resin. In other embodiments, the solid catalyst can be a mineral-based supported acid catalyst, such as a zeolite. In one embodiment, the solid resin catalyst can be selected from commercially available strongly acidic, cationic polymeric catalysts. Non-limiting examples of such solid acid resin catalyst include Amberlyst™ 35, Amberlyst™ 70, Puralite™ CT and combinations thereof. In some embodiments, the suitable solid acid resin catalyst has an acid equivalency of at least 1, for example from at least 1 to 10, such as from 3 to 10.

[0059] In one embodiment, the process for converting PTMEG to THF uses one or more tubular-shaped vessels. Such one or more tubular-shaped vessels may be arranged into a form resembling a heat exchanger. Examples of the reaction vessels, include, but are not limited to, those with a fixed bed reactor, a structured distillation column packing bed or a fluidized bed; or a continuously stirred tank reactor, a plug flow reactor or a trickle flow reactor. In embodiments wherein the reaction vessel is a plug flow reactor, catalyst is constrained by mesh at the bottom of tubular reactor and by mesh at the top of tubular reactor. The mesh keeps the catalyst at the bottom of the reactor whilst mesh prevents the catalyst jumping from one tube in the reactor to another tube. In yet another embodiment, the reaction vessel is a trickle flow reactor with the liquid flowing down and the vapors flowing up. In a further embodiment, the reactor vessel is a tank with external circulation through a pump.

[0060] With reference to Figure 2, PTMEG was held molten in heated batch in PTMEG reservoir 201 and fed by gravity continuously to distillation reactor 202, the temperature of which is controlled by heating block 203. Reactor 202 contains strong acid catalyst. In this particular embodiment, the strong acid catalyst is in a slurried form. The vapor phase distillate 204 exiting reactor 202 is cooled in condenser 205 and product (THF and water) collected at chamber 206.

[0061] The rate of THF and water production was measured as a function of temperature (Examples 1 and 2; Figures 3 and 4) and catalyst weight fraction (Examples 3 and 4; Figures 5 and 6).

EXAMPLES [0062] The depolymerization of polytetramethylene ether glycol (PTMEG) to tetrahydrofuran (THF) and water was carried out in glassware, at atmospheric pressure, in the presence of presence of a solid acid resin catalyst. The reaction was carried out at several different process temperatures and catalyst weight fractions as described below and was followed by the collection of samples from the vapor phase distillate and the reactor liquid phase as a function of time. The samples were subsequently analysed by Gas Chromatography (GC).

[0063] Examples 1, 2, 3 and 4 employed the DuPont Amberlyst™ 35 solid-acid resin catalyst in the distillation process configuration represented schematically in Figure 2. PTMEG was held molten in heated batch and fed by gravity continuously to the distillation reactor. As the reaction proceeded as a function of temperature (Examples 1 and 2) or catalyst weight fraction (Examples 3 and 4), THF and water vapor were released overhead and condensed. The rate of THF and water evolution was measured periodically by measuring cylinder.

Example 1

[0064] 16g of catalyst (DuPont Amberlyst™) was added to the reactor scheme as represented by Figure 2, along with PTMEG having an average molecular weight distribution of 2000 daltons (Mn~2000). The level in the reactor was maintained at 310mls by gravity feed and adjustment of the reservoir height by lab jack. Heat was applied via an appropriately sized heating block to achieve the desired reaction temperature and the rate of THF and water evolution was recorded. Figure 3 records the THF/water evolution rate as a function of temperature at this particular catalyst weight fraction and with PTMEG having an average molecular weight distribution of 2000 daltons (Mn~2000).

Example 2

[0065] 16g of catalyst (DuPont Amberlyst™) was added to the reactor scheme as represented by Figure 2, along with PTMEG having an average molecular weight distribution of 250 daltons (Mn~250). The level in the reactor was maintained at 310mls by gravity feed and adjustment of the reservoir height by lab jack. Heat was applied via an appropriately sized heating block to achieve the desired reaction temperature and the rate of THF and water evolution was recorded. Figure 4 records the THF/water evolution rate as a function of temperature at this particular catalyst weight fraction and with PTMEG having an average molecular weight distribution of 250 daltons (Mn~250). Example 3

[0066] Varying amounts of DuPont Amberlyst™ was added to the reactor scheme as represented by Figure 2, along with PTMEG having an average molecular weight distribution of 2000 daltons (Mn~2000). The level in the reactor was maintained at 3 lOmls by gravity feed and adjustment of the reservoir height by lab jack. Heat was applied via an appropriately sized heating block to achieve a reaction temperature of 115°C and the rate of THF and water evolution was recorded. Figure 5 records the THF/water evolution rate as a function of catalyst weight fraction temperature at this particular reaction temperature and with PTMEG having an average molecular weight distribution of 2000 daltons (Mn~2000).

Example 4

[0067] Varying amounts of DuPont Amberlyst™ was added to the reactor scheme as represented by Figure 2, along with PTMEG having an average molecular weight distribution of 250 daltons (Mn~250). The level in the reactor was maintained at 310mls by gravity feed and adjustment of the reservoir height by lab jack. Heat was applied via an appropriately sized heating block to achieve a reaction temperature of 115°C and the rate of THF and water evolution was recorded. Figure 6 records the THF/water evolution rate as a function of catalyst weight fraction temperature at this particular reaction temperature and with PTMEG having an average molecular weight distribution of 250 daltons (Mn~250).

[0068] The disclosure provided herein describes features in terms of preferred and exemplary embodiments thereof. Numerous other embodiments, modifications and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure.

Claims

1. A process for conversion of polytetramethylene ether glycol to tetrahydrofuran, comprising the steps of: a) introducing a stream comprising polytetramethylene ether glycol to a strong acid catalyst capable of converting polytetramethylene ether glycol to tetrahydrofuran and water; b) operating said process in a reactor under operating conditions sufficient to effect acid- catalyzed depolymerization of polytetramethylene ether glycol to tetrahydrofuran and water; and c) recovering the tetrahydrofuran.

2. The process of claim 1, wherein the strong acid catalyst is a solid catalyst.

3. The process of claim 2, wherein the solid catalyst is selected from the group consisting of a polymer-based acid resin, a mineral-based supported acid catalyst and combinations thereof.

4. The process of claim 2, wherein the solid catalyst is an acidic resin catalyst.

5. The process of claim 4, wherein the acidic resin catalyst has an acid equivalency of between 1 and 10.

6. The process of claim 1, wherein the strong acid catalyst has a residence time of between 5 minutes and 60 minutes, and preferably between 10 minutes and 30 minutes.

7. The process of claim 1, wherein the strong acid catalyst is contained within a fixed bed or a fluidized bed within the reactor.

8. The process of claim 7, wherein the strong acid catalyst is slurried.

9. The process of claim 2, wherein the ratio of solid catalyst to reactor liquid inventory is 5wt% to 90wt%, and preferably 10wt% to 30wt%.

10. The process of claim 1, wherein the reactor comprises one or more tubular-shaped vessels.

11. The process of claim 1, wherein the reactor is operated at a temperature of from 80°C to 150°C, and preferably 90°C to 120°C.

12. The process of claim 1, wherein the reactor is operated at 0.3 bara to 5 bara, preferably atmospheric pressure.

13. The process of claim 1, wherein the tetrahydrofuran and water produced is 90±10/99.9±0.1, weight/weight, tetrahydrofuran/water.

14. The process of claim 1, further comprising a step (d) of recycling at least a portion of the tetrahydrofuran into upstream processing reactions for synthesis of polytetramethylene ether glycol.

15. The process of claim 14, wherein said step (d) recycles at least a portion of the tetrahydrofuran as a feed into the tetrahydrofuran polymerization stage for converting tetrahydrofuran to polytetramethylene ether acetate.