WO2015095879A1

WO2015095879A1 - Method of manufacturing 2-methyl-1, 3-dioxolane in a solid state polycondensation process

Info

Publication number: WO2015095879A1
Application number: PCT/US2014/071956
Authority: WO
Inventors: Clive Alexander Hamilton; Robert Edward Neate
Original assignee: Invista Technologies S.A.R.L.
Priority date: 2013-12-18
Filing date: 2014-12-22
Publication date: 2015-06-25

Abstract

The invention relates to a method for producing 2-methyl-1,3-dioxolane from a polyester solid state polymerization system. The method comprises using an acid catalyst to effectuate the conversion of acetaldehyde present within the system to 2-methyl-1,3-dioxolane, which can be readily removed in the ethylene glycol stream.

Description

METHOD OF MANUFACTURING 2~METHYL-1,3-DIOXOLANE IN A SOLID STATE

POLYCONDENSATION PROCESS

FIELD OF THE INVENTION

The invention is related to methods for manufacturing 2-methyl-1,3-dioxolane ("MDO"). It is also related to systems implementing such methods in a solid state polycondensation process.

BACKGROUND OF THE INVENTION MDO is a heterocyclic acetal that is used as a comonomer in the preparation of acetal

(polyoxymethylene) resins. These copolymers have a better hydro lytic stability than the homopolymers. MDO can be manufactured using several techniques (See U.S. Patent No. 3027352), including acetalization of aldehydes and ketalization of ketones with ethylene glycol. One source of aldehydes, acetaldehyde, is the transesterification of vinyl ester end groups from PET production.

Polyester resins such as poly(ethyIene terephthalate) (PET) resins are widely produced and used, for example, in beverage and food containers, thermofoiming applications, textiles, and engineering resins. Generally, the production of PET is based on a reaction between tereplithalic acid and/or dimethyl terephthalate with ethylene glycol (via esterification and/or transesterification, respectively). The resulting bis-hydroxyethyl terepthalate pre-polymers are then joined by means of polycondensation reactions to give a polymeric product.

Melt polycondensation alone is generally not capable of producing polyesters such as bottle-grade PET resin with the desired properties. Therefore, a two-stage process is generally employed, wherein the pre- polymers are subjected to melt polycondensation to achieve a certain intrinsic viscosity; subsequently, the resin is subjected to a process known as "solid state polycondensation" ("SSP"). The SSP process is specifically designed for the development of higher molecular weight polymeric products having increased intrinsic viscosities. The SSP process results in further increasing the molecular weight of the melt-polymerized PET by polycondensation of the polymer chains with each other.

Various byproducts can be produced during the production of PET, including, but not limited to, polycondensation cleavage products. One common side reaction that may occur during the polycondensation reaction is the production of acetaldehyde (AA) by transesterification of vinyl ester end groups of the PET. The presence of AA is often of significant importance in PET production and its content is rigorously controlled for certain uses. As an example, when PET is used to produce bottles as containers for beverages, AA in the bottle can migrate to the beverage, causing an undesirable flavor in the beverage (which is particularly noticeable in water). It is therefore desirable to minimize the content of AA in the final PET product.

Generally during the SSP process, reaction byproducts such as AA are removed via a process gas that is at least partially re-circulated through the system. The process gas takes up impurities {e.g., reaction byproducts) from the system and the impurity-rich gas is subsequently purified to remove those impurities and render the gas available for reuse in the system. Various means are known for purifying process gases. One common gas purification system utilizes a gas scrubber containing an aqueous or organic fluid that is brought into contact with the impurity-rich gas and which purifies the gas via a liquid-gas exchange process. This process, however, does not convert the A A into a useful product.

BRIEF SUMMARY OF THE INVENTION

The problem with the known methods of making MDO is that a separate process-step is required. Further, the problem of known PET polycondensation methods is that the AA is still present in the overall system and must be subsequently removed. Therefore, it would be advantageous if the manufacture of MDO could be combined with the removal of AA, thereby eliminating AA and creating additional value in running a SSP process.

The inventors have found that acetaidehyde (AA) (as may be present in the process gas circulating within a solid state polycondensation (SSP) system for the production of polyethylene terepthalate (PET)) and ethylene glycol (EG) (as may be present as a washing liquid in a gas scrubber for the process gas) reversibly react to fonn 2-methyl-1,3-dioxolane ("MDO") and water. This reaction does not interfere with the overall SSP process. Advantageously, according to the present invention, a catalyst can be incorporated within the gas scrubber to facilitate this reaction to form MDO. The conversion of AA to MDO is beneficial as it effectively results in removal of AA from the system and creates a stream of MDO for use in manufacturing other chemicals.

In one aspect of the invention is provided a method of manufacturing 2-methyl-l ,3-dioxoJane ("MDO") in a polyester solid state polycondensation process, comprising: (a) introducing a process gas inlet stream from a polyester polycondensation process comprising a first concentration of acetaidehyde into a gas scrubbing unit; (b) introducing a liquid ethylene glycol inlet stream into the gas scrubbing unit; (c) contacting the process gas inlet stream with the liquid ethylene glycol inlet stream in the presence of one or more acid catalysts in the gas scrubbing unit, wherein the acetaidehyde reacts with the ethylene glycol to form 2-methyI-1,3-dioxolane during said contacting step, the contacting step producing a liquid ethylene glycol outlet stream containing 2-methyl- 1,3-dioxolane; (d) removing at least part of the ethylene glycol outlet stream from the gas scrubbing unit; and (e) separating the 2-methyl-1,3-dioxolane from the removed ethylene glycol.

In some aspects, the process gas is selected from the group consisting of nitrogen, argon, carbon dioxide, and mixtures thereof, in some aspects, the method can further comprise recycling and/or using the purified process gas stream, for example, as a process gas stream in a further method of preparing a high molecular weight polymer. In other aspects, the ethylene glycol stream after removal of MDO can be recirculated back to the gas scrubber. The acid catalysts used in the method can vary and can be, in certain embodiments, homogeneous or heterogeneous acid catalysts. For example, the acid catalysts can be selected from the group consisting of mineral acids, sulfonic acids, carboxylic acids, and mixtures thereof. In some specific embodiments, the one or more acid catalysts are selected from the group consisting of a boron trihalide, an organoborane, an aluminum trihalide, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluene sulfonic acid, trifluoromethanesulfonic acid, a boric acid, hydrochloric acid, hydroiodic acid, hydrobromic acid, perchloric acid, nitric acid, sulfuric acid, fluorosulfuric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, carbonic acid, formic acid, benzoic acid, and mixtures and derivatives thereof. In certain embodiments, the one or more acid catalysts comprise a solid support having an acidic functionality attached thereto, wherein the acidic functionality is selected from the group consisting of a boron trihalide, an organoborane, an aluminum trihalide, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluene sulfonic acid, trifluoromethanesulfonic acid, a boric acid, hydrochloric acid, hydroiodic acid, hydrobromic acid, perchloric acid, nitric acid, sulfuric acid, fluorosulfuric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, carbonic acid, formic acid, benzoic acid, and mixtures and derivatives thereof.

In certain aspects, the temperature at which the contacting step is conducted is about 50 °C or less. The

MDO separation step, in certain aspects, comprises neutralizing the ethylene glycol, filtering the ethylene glycol, distilling the ethylene glycol, or a combination thereof. In further aspects, the clean ethylene glycol outlet stream may be used as a reactant to produce poly(ethylene terephthalate) via melt condensation polymerization.

In another aspect of the invention is provided an apparatus for manufacturing MDO comprising: a housing enclosing a chamber adapted to provide contact between a process gas and a scrubbing liquid, the chamber containing one or more solid acid catalysts; a supply of process gas from a polyester solid state polycondensation process comprising acetaldehyde; a first inlet in fluid communication with the chamber and in fluid communication with the supply of process gas comprising acetaldehyde and adapted to introduce the process gas comprising acetaldehyde into the chamber; a supply of ethylene glycol; a second inlet in fluid communication with the chamber and in fluid communication with the supply of ethylene glycol and adapted to introduce the ethylene glycol into the chamber; a first outlet in fluid communication with the chamber and adapted to remove an ethylene glycol stream containing 2-methyl-1,3-dioxolane from the chamber; and a separation device for receiving the ethylene glycol stream containing 2-methyl-1,3-dioxolane.

In certain aspects, the one or more acid catalysts are heterogeneous acid catalysts, present in a packed tray within the manufacturing unit. The operation of the unit can vaiy and may comprise, for example, a centrifugal-type scrubber, spray scrubber, impingement-type scrubber, packed tower-based scrubber, venturi- type scrubber, eductor venturi-type scrubber, film tower-based scrubber, scrubber with rotating elements, or a combination thereof. BRIEF DESCRIPTION OF THE DRAWING

Having thus described the invention in general terms, reference will now be made to the accompanying drawing, which is not necessarily drawn to scale, and wherein:

FIG. 1 is a depiction of an apparatus for manufacturing MDO according to the invention; and

FIG. 2 is a depiction of an exemplary SSP system according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. As used in the specification, and in the appended claims, the singular forms "a", "an", "the", include plural referents unless the context clearly dictates otherwise.

Briefly, the present invention provides a method for manufacturing 2-methyI-1,3-dioxolane ("MDO") in a polyester solid state polycondensation (SSP) system using process gas containing acetaldehyde. According to the invention, the manufacture of MDO is facilitated by means of an ethylene glycol washing liquid in the presence of an acid catalyst, wherein the acid catalyst functions to convert acetaldehyde to MDO which can be more readily removed from the SSP system in the ethylene glycol stream. Further, the invention provides an apparatus for manufacturing MDO, which is equipped to receive the process gas and a washing fluid and bring the gas and fluid into contact with one another, wherein the gas purification system also contains one or more acid catalysts.

hi particular, the SSP process is commonly used to produce high molecular weight polyethylene terephthalate (PET), which is known to produce acetaldehyde (AA) as an undesirable byproduct. The AA content in the final PET resin produced via SSP is advantageously minimized, as AA can subsequently leach out of PET, and has been noted to negatively impact the taste of beverages and/or foods contained in PET containers. The inventors have found that AA present in the process gas can reversibly react with EG present in the gas scrubber to form 2-methyl-1,3-dioxolane ("MDO") and water. According to one aspect of the disclosed processes, one or more acid catalysts are incorporated within the gas scrubber to promote and/or enhance this reaction of AA and EG to form MDO. It is noted that, although the present disclosure focuses on methods and systems for the production of PET, it may be applicable to the production of other polymers, such as other polyesters, as well. In particular, it may be applicable to the production of various polymers wherein AA is produced as an undesirable reaction byproduct. By converting the AA to MDO, the SSP gas can be provided in a cleaner form {i.e., with decreased AA content), such that it can be more readily re-used in the SSP process. Using this cleaner SSP gas may effectively reduce AA contamination in the PET preparation process and thereby reduce the AA content of the subsequently produced PET. Additionally, by converting the AA to MDO, the limit on AA content in the PET resin introduced to the SSP process can be increased (i.e._t the specifications on the input material can be loosened), as the process may, in certain embodiments, be capable of more effectively decreasing the AA content throughout the SSP process. Further, by converting the AA to MDO, it may be possible to provide smaller, more efficiently designed scrubbers for use in the SSP system.

By "promoting" or "enhancing" the conversion of AA to MDO is meant that a greater percentage of AA is converted to MDO than would occur in the absence of an acid catalyst. For example, a catalyst can, in some embodiments, increase the rate of and/or percent conversion of AA to MDO. In some embodiments, a catalyst can shift the equilibrium of a reversible reaction to the product side. Although not intending to be limited by theory, it is believed that protonation of the carbonyl oxygen of AA by an acid catalyst may promote nucleophilic attack by a hydroxyl group on the EG at the carbonyl carbon of AA, driving the conversion to MDO.

The means by which catalysis of the conversion of AA to MDO is effected by an acid catalyst according to the present invention can vary. In certain embodiments, a catalyst is incorporated within a MDO manufacturing apparatus. Figure 1 provides a schematic depiction of a MDO manufacturing apparatus 10, exemplified in the form of a gas scrubber unit. Although Figure 1 depicts a general gas scrubber setup, it is to be understood that a variety of gas scrubbers are known in the art and can be modified for use according to the present invention. Scrubbers can vary widely in size, capacity, operation, and complexity, and all such types are intended to be encompassed by the disclosure provided herein. Generally, scrubbers are designed so as to bring a dirty process gas into intimate contact with a washing fluid that can remove certain contaminants therefrom (e.g., by adsorption). Certain scrubbers operate by means of directing dirty process gas through a tortuous path (e.g., using baffles and other restrictions) and/or provide for some degree of turbulence to ensure significant contact with a washing fluid, wherein contaminants are removed by contact between the gas and the washing fluid. The washing fluid may be flowed, e.g., concurrently to the process gas within the scrubber or counter- currently to the process gas within the scrubber (as shown in Figures 1 and 2), although the scrubber may operate in other ways. Scrubbers may be, for example, centrifugal-type scrubbers, spray scrubbers, impingement-type scrubbers, packed towers, venturi-type scrubbers, eductor venturi-type scrubbers, film towers, scrubbers with rotating elements, or scrubbers comprising multiple of these and other types. Although many types and design configurations of gas scrubbers are known and intended to be included within the present disclosure, exemplary types and design configurations are described for example, in U.S. Patent Nos. 3,581,474 to Kent; 3,656,279 to Mcilvaine et al; 3,680,282 to Kent; 3,690,044 to Boresta; 3,795,486 to Ekman; 3,870,484 to Berg; 5,185,016 to Carr; 5,656,047 to Odom et al; 6,102,990 to Kemanen et al ; 6,402,816 to Trivet et al; and U.S. Patent Application Publication Nos. 2007/01 13737 to Hagg et al, which are incorporated herein by reference.

The MDO manufacturing apparatus shown in Figure 1 is configured with a gas inlet, through which dirty process gas 20 (e.g., from the SSP process) enters the unit. It is noted that although the gas inlet is shown on the bottom of the unit, the dirty process gas may enter from the top or side of the unit. The dirty process gas generally comprises various byproducts of the polycondensation reaction, including, but not limited to, cleavage products such as water, ethylene glycol, methyl dioxolane, and aldehydes (e.g., acetaldehyde). The process gas entering the scrubber (e.g., the process gas of the SSP system) can vary, but is generally a gas that is inert or relatively inert under the conditions within the system. For example, the process gas may, in some embodiments, comprise nitrogen, argon, helium, carbon dioxide, or mixtures thereof.

The temperature of the process gas (if discharged from the polyester melt phase reactor) prior to entering the MDO manufacturing apparatus can vary from about 100°C to greater than 250°C, including from 100°C to about 500°C, from about 100°C to about 400°C, from about 100°C to about 300°C, from about 100°C to about 200°C, and from about 250°C to about 310°C. If the process gas is discharged from a condensing system for reaction by-products of a polyester melt phase reactor, than the temperature can vary from about 0°C to about 100°C, including 0°C to about 50°C.

Within the unit, the dirty process gas (containing aldehydes) comes into contact with the washing liquid containing ethylene glycol (EG). A clean EG supply 30 is in fluid contact with the unit, takes up aldehydes in the dirty process gas, and the reaction of EG and aldehydes produces: (1) an MDO stream 40, comprising EG and MDO; and (2) a clean process gas stream 50. in other embodiments, the ethylene glycol / MDO stream can be recirculated back to the gas scrubber to react with more acetaldehyde. hi some embodiments, a portion of the recycled ethylene glycol stream can be purged to control the concentration of MDO in the unit. In certain embodiments, the glycol is supplied from the glycol-driven ejector system of a melt phase polyester process. This reduces emissions from the melt phase polyester process. The emissions reduction can vary from 30% - 100%, including 30% - 90%, 30% - 80%, 30% - 70%, 30% - 60%, 30% - 50%, 40% - 90%, 40% - 80%, 40% - 70%, 40% - 60%, 50% - 80%, and 50% - 70%, compared to a scrubbing unit not using the process described in the various aspects. The ethylene glycol / MDO stream 40 can go to a separation device to separate out the MDO.

According to the invention, various acid catalysts can be incorporated within the gas scrubber.

Homogeneous acid catalysts, heterogeneous acid catalysts, or a combination thereof can be used. Acid catalysts that may be used according to the invention to promote the reaction of A A and EG to fonn MDO include, but are not limited to, Lewis acids and Bronsted acids. Acid catalysts may be, for example, mineral (i.e., inorganic) acids, sulfonic acids, or carboxylic acids. Certain specific acids include, but are not limited to, boron trihalides, organoboranes, aluminum trihalides, other various metal cations or compounds (which generally can serve as Lewis acids only after dissociating a Lewis base bound thereto); methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluene sulfonic acid (TsOH), trifiuoromethanesulfonic acid, boric acids, hydrochloric acid, hydroiodic acid, hydrobromic acid, perchloric acid, nitric acid, sulfuric acid, fluorosulfuric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, carbonic acid, formic acid, and benzoic acid.

Although homogeneous acid catalysts may be effective in enhancing the conversion of AA and EG to MDO, in certain embodiments, one or more heterogeneous catalysts are used (generally in solid form). Heterogeneous acid catalysts generally comprise one or more acid functional groups immobilized on a solid support that is insoluble in the liquid or gas in which the reaction is to be conducted. Heterogeneous catalysts are advantageous in their ease of implementation, ease of removal, and the ability to maintain EG in neutral form. Various acidic functionalities can be provided on solid supports to provide the desired functionality in a solid form, such as those acidic moieities noted above. Various solid supports can be used as well, including, but not limited to, silica, clay, synthetic or natural polymers. Certain exemplary heterogeneous catalysts include Amberlyst™ polymeric catalysts and ion exchange resins, which generally display a sulfuric acid functional group. Other exemplary heterogeneous acid catalysts are described, for example, in U.S. Patent Nos. 5,294,576 to Ho et al; 5,481,0545, 563,313, 5,409,873, and 5,571,885 to Chung et at, 5,663,470, 5,770,539, 5,877,371, and 5,874,380 to Chen et ah; and 6,436,866 to Nishikido, which are all incorporated herein by reference.

The reaction of AA and EG to form MDO has been observed to be temperature dependent if not catalyzed. For this reason, one would not expect significant reaction at typical temperatures within a gas scrubber. A MDO manufacturing device, for example a gas scrubber, may have a temperature of between about 5°C and around 60°C, such as about 8°C at the top, about 12°C in the middle, and about 45°C at the bottom of the scrubber. At ambient temperature, there is generally no appreciable reaction between AA and EG to produce MDO. At elevated temperatures, the reaction is enhanced. Beneficially, an added acidic catalyst allows for an efficient reaction of AA and EG to produce MDO at temperatures typically associated with a gas scrubber. Thus, the high temperatures generally required for reaction of A A and EG in the absence of an added catalyst to form MDO are not required and the methods of the invention can be readily implemented into existing scrubber systems with little to no modification or control of temperature within the scrubber.

It is noted that the reaction of AA and EG to form MDO is reversible and both the forward reaction and the reverse reaction are acid-catalyzed. It is preferr ed that, under the conditions of use, the reaction of AA and EG to form MDO is favored over the reverse reaction. The reverse reaction requires water; therefore, in some embodiments, it may be advantageous to limit the water content in the washing fluid. The latter (reverse) reaction is described in further detail, for example, in U.S. Patent Application Publication No. 201 1/0097243 to Reimann et al, which is incorporated herein by reference. The acidic catalyst can be incorporated within the MDO manufacturing apparatus in various ways. For example, as illustrated in Figure 1, in some embodiments, the apparatus comprises a multi-stage setup (e.g., the 3 -stage setup of Figure 1, comprising stages A, B, and C). In such embodiments, a heterogeneous catalyst may be packed within a vessel (e.g., a packed tray/bed) held within the unit to provide one or more layers of material through which the ethylene glycol washing solution passes. With reference to Figure 1, the catalyst may thus be provided in one or more of the three stages A, B, and C, depicted in scrubber 10 (i.e., at the top, middle, or bottom of the unit). It is noted that multi-stage units can have vaiying numbers of stages and the catalyst can be incorporated within any of these stages. The heterogeneous catalyst can be provided at vaiying levels within the unit; however, it is advantageously toward the bottom of the unit (i.e., a portion of the unit that is at a higher temperature, as increased temperature promotes the conversion of AA and EG to MDO). For example, with reference to Figure 1, although the catalyst can be provided in any one or more of stages A, B, and C, catalyst may be provided, at least in part, in stage C. However, use of an acidic catalyst as described herein allows for the reaction to occur with good conversion of reactants to product, even at lower temperatures than generally required for such a reaction. Other physical means for ensuring contact between the acid catalyst and the dirty ethylene glycol are intended to be encompassed by the present invention as well. Where homogeneous catalysts are used, they may be, in some embodiments, directly added to the EG washing fluid. The amount of catalyst added to the gas scrubber system can vary, but may generally be any amount sufficient to catalyze the reaction of at least a portion, and including at least a substantial portion, of the AA with EG to produce MDO. Specifically, the amount of catalyst can vary from 1 kg per tonne per hour of EG scrubber liquid (1 kg/tph) to 1000 kg/tph; including 2 kg/tph to 100 kg/tph; 2 kg/tph to 10 kg/tph; and 5 kg/tph.

The MDO manufacturing apparatus as described herein is advantageously incorporated within an SSP system for polyester production, although application of the methods of the invention may be useful in other applications utilizing a unit (e.g. gas scrubber) wherein AA is beneficially minimized. The SSP system generally operates according to methods known in the art, as described for example, in U.S. Patent No. 7,819,942 to Christel ei at, which is incorporated herein by reference. Figure 2 of the present application illustrates one exemplary SSP system 6Θ, although the components within the system can vary. Briefly, the SSP process typically begins with the introduction of a substantially amorphous PET base chip, such as a base chip having an intrinsic viscosity of about 0.6 iV. The acetaldehyde content in the base chip can vary, but is advantageously reduced to or maintained at a low level through the SSP process. The base chip is crystallized to about 40 or 45% crystalline content in a crystallizer unit 70 by application of heat. The chip then typically passes through a preheater 80 and then can then be further heated in a reactor unit 90, which generally increases the crystallinity of the PET even further (e.g., to about 65-70% crystalline). It is within the reactor unit that the PET generally exhibits the greatest desirable buildup of intrinsic viscosity. The PET then passes into a cooler 100 to give an SSP PET chip having a higher intrinsic viscosity than the base chip (e.g., about 0.8 iV) and having a relatively low AA content (e.g., about 100 ppm or less, about 50 ppm or less, about 10 ppm or less, about 9 ppm or less, about S ppm or less, about 7 ppm or less, about 6 ppm or less, about 5 ppm or less, about 4 ppm or less, about 3 ppm or less, or about 2 ppm or less, in some embodiments, even lower AA values are obtainable, such as about 1 ppm or less. The reactor units within the SSP system can vaiy and may, in certain embodiments, include devices ranging from fixed-bed, solid-air jet, or fluidized bed reactors, and/or reactors having agitating implements or reactors that move. Various temperatures and pressures can be utilized in the various stages of the SSP process.

Also in Figure 2 is illustrated the MDO manufacturing unit 110, as described in greater detail in reference to Figure 1. Figure 2 illustrates an exemplary flow system of the process gas, which then enters the unit (as "Dirty N2 in"). Ethylene glycol, the reacting fluid cycled through the unit, reacts with the aldehyde in the process gas, providing: (1) a EG and MDO stream; and (2) process gas in "clean" form, at which point it can be subsequently reused (e.g., within the reactor 90, as shown in Figure 2). The unit 110, according to the invention, further comprises an acid catalyst as provided herein. It is to be understood that Figure 2 provides one exemplary system in which an acid catalyst can be used; this disclosure is not intended to be limiting, and the methods and materials described herein can be applied to various methods and systems wherein AA and EG may be present.

In certain aspects, the ethylene glycol containing the MDO can be cleaned for reuse for various purposes. The MDO can be separated, for example, by filtration, decantation, and/or distillation, and the cleaned EG recycled back into the system. Use of a heterogeneous catalyst simplifies the cleanup of EG, as the EG generally is maintained in neutral form. Although homogeneous catalysts can be used according to the invention, their use generally results in the production of acidified glycol, which must be neuti'alized in addition to being filtered and/or distilled. The cleaned EG can beneficially be used, for example, as an input material for melt phase condensation polymerization to produce additional PET. Thus, in certain embodiments, a single EG stream may be used in the various steps in preparing high molecular weight PET. In such embodiments, EG recycled from the SSP process can be fed into a reaction with terephthalic acid and/or dimethyl terephthalate to give PET monomer units which are joined by melt phase condensation polymerization and which may be furtlier subjected to SSP to increase the intrinsic viscosity thereof.

EXPERIMENTAL

The reaction of acetaldehyde (AA) with ethylene glycol (EG) producing 2 methyl, 1,3 dioxolane (MDO) and water was carried out in glassware, under reflux, at atmospheric pressure as a function of temperature. The reaction was followed by extracting samples from the reaction zone via syringe as a function of time. Each sample was quenched in an isopropanol diluent and analyzed by gas chromatography (GC). Comparative examples 1, 2 and 3 illustrate the kinetics of the catalyst-free reaction monitored by following the formation of MDO and consumption of AA at 50°C, then separately at 85°C and 130°C. Example 1 exemplifies the use of a solid acid catalyst, in this case Dow Amberlyst™ 35, at 50°C.

Comparative Example 1

40g of refrigerated acetaldehyde was added to 60g of chilled ethylene glycol in a 250 ml round- bottomed flask and set up for reflux. The flask was heated to 50°C and samples were extracted by syringe as a function of time and diluted tenfold in isopropanoi to quench the reaction. The samples were analyzed by gas chromatography and the results tabulated below.

Table 1: AA and MDO concentrations at 50°C as a function of time

The data illustrates that at 50°C, the % AA decreases slowly and the % MDO rises slowly over the time period displayed.

Comparative Example 2

20g of refrigerated acetaldehyde was added to 80g of chilled ethylene glycol in a 250ml round-bottomed flask and set up for reflux. The flask was heated to 85°C and samples were extracted by syringe as a function of time and diluted tenfold in isopropanoi to quench the reaction. The samples were analyzed by gas

chromatography and the results tabulated below. Table 2: AA and MDO concentrations at 85°C as a function of time

The data illustrates that at 85°C, the % AA decreases more quickly and the % MDO rises more quickly over the time period displayed than at 50 °C.

Comparative Example 3

95g of refrigerated acetaldehyde was added to 5g of chilled ethylene glycol in a 250 ml round-bottomed flask and set up for reflux. The flask was heated to 130°C and samples were extracted by syringe as a function of time and diluted tenfold in isopropanol to quench the reaction. The samples were analyzed by gas chromatography and the results tabulated below.

Table 3: A A and MDO concentrations at 130°C as a function of time

The data illustrates that at 130°C, the % AA decreases even more quickly and the % MDO rises even more quickly over the time period displayed than at 85 °C.

Example 1

40g of refrigerated acetaldehyde was added to 60g of chilled ethylene glycol in a 250 ml round- bottomed flask, set up for reflux, along with 2.5g of Amberlyst™ 35 solid acid catalyst resin. The flask was heated to 50°C and samples were extracted by syringe as a function of time and diluted tenfold in isopropanol to quench the reaction. The samples were analyzed by gas chromatography and the results tabulated below. Table 4: AA and MDO concentrations at 50°C with added catalyst as a function of time

The data illustrates that at 50°C with Amberiyst™ 35 solid acid catalyst resin added to the reaction, the % AA decreases more quickly and the % MDO rises even more quickly over the time period displayed than where no catalyst is added (Comparative Example 1).

Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing description. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims, Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

THAT WHICH IS CLAIMED:

1. A method for manufacturing 2-methyl- 1 ,3 -dioxolane in a polyester solid state polycondensation

process, comprising:

(a) introducing a process gas inlet stream from a polyester polycondensation process comprising a first concentration of acetaldehyde into a gas scrubbing unit;

(b) introducing a liquid ethylene glycol inlet stream into the gas scrubbing unit;

(c) contacting the process gas inlet stream with the liquid ethylene glycol inlet stream in the presence of one or more acid catalysts in the gas scrubbing unit, wherein the acetaldehyde reacts with the ethylene glycol to form 2-methyl- 1,3 -dioxolane during said contacting step, the contacting step producing a liquid ethylene glycol outlet stream containing 2-methyl- 1,3 -dioxolane;

(d) removing at least a part of the ethylene glycol outlet stream from the gas scrubbing unit; and

(e) separating the 2-methyl- 1 ,3-dioxolane from the removed ethylene glycol.

2. The method of claim 1, wherein the process gas is selected from the group consisting of nitrogen, argon, carbon dioxide, and mixtures thereof.

3. The method of claim 1 , wherein the one or more acid catalysts are homogeneous or heterogeneous acid catalysts.

4. The method of claim 1, wherein the one or more acid catalysts are selected from the group consisting of mineral acids, sulfonic acids, carboxylic acids, and mixtures thereof.

5. The method of claim 1, wherein the one or more acid catalysts are selected from the group consisting of a boron trihaiide, an organoborane, an aluminum trihaiide, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p~toluene sulfonic acid, trifluoromethaiiesulfonic acid, a boric acid, hydrochloric acid, hydroiodic acid, hydrobromic acid, perchloric acid, nitric acid, sulfuric acid, fiuoiosulfuric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, carbonic acid, formic acid, benzoic acid, and mixtures and derivatives thereof.

6. The method of claim 1, wherein the one or more acid catalysts comprise a solid support having an acidic functionality attached thereto, wherein the acidic functionality is selected from the group consisting of a boron trihaiide, an organoborane, an aluminum trihaiide, methanesulfonic acid, etlianesulfonic acid, benzenesulfonic acid, p-toluene sulfonic acid, trifliioromethanesulfonic acid, a boric acid, hydrochloric acid, hydroiodic acid, hydrobromic acid, perchloric acid, nitric acid, sulfuric acid, fluorosulfuric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, carbonic acid, formic acid, benzoic acid, and mixtures and derivatives thereof.

7. The method of claim 1, wherein the one or more solid catalysts is selected from the group consisting of Zirconia, alpha and gamma alumina, and zeolites.

8. The method of claim 1, wherein the temperature at which the contacting step is conducted is about 50 °C or less.

9. The method of claim 1, wherein said separating the 2-methyI-1,3-dioxolane from the removed ethylene glycol comprises a process selected from the group consisting of: filtering, decanting, distillation, or combination thereof.

10. The method of claim 9, wherein the ethylene glycol is recycled back to the gas scrubbing unit after separating the 2-methyl-1,3-dioxolane,

1 1. The method of claim 9, wherein the ethylene glycol is used as a reactant in to produce poly(ethylene terepthalate) via melt condensation polymerization after separating the 2-methyl-1,3-dioxolane.

12. The method of one of claims 1-1 1 wherein the process gas inlet stream is at a temperature from about lOOC to about 500C.

13. The method of claim 12 wherein the process gas inlet stream is at a temperature from about l OOC to about 400C.

14. The method of claim 13 wherein the process gas inlet stream is at a temperature from about lOOC to about 300C.

15. The method of claim 14 wherein the process gas inlet stream is at a temperature from about 250C to about 3 IOC.

16. An apparatus for manufacturing 2-methyl-1,3-dioxolane comprising:

(a) a housing enclosing a chamber adapted to provide contact between a process gas and a scrubbing liquid, the chamber containing one or more solid acid catalysts;

(b) a supply of process gas from a polyester solid state polycondensation process comprising acetaldehyde;

(c) a first inlet in fluid communication with the chamber and in fluid communication with the supply of process gas comprising acetaldehyde and adapted to introduce the process gas comprising acetaldehyde into the chamber;

(d) a supply of ethylene glycol;

(e) a second inlet in fluid communication with the chamber and in fluid communication with the supply of ethylene glycol and adapted to introduce the ethylene glycol into the chamber;

(f) a first outlet in fluid communication with the chamber and adapted to remove an ethylene glycol stream containing 2-methyl-1,3-dioxolane from the chamber; and

(g) a separation device for receiving the ethylene glycol stream containing 2-methyl-1,3-dioxoIane.

17. The apparatus of claim 16, wherein the process gas is selected from the group consisting of nitrogen, argon, carbon dioxide, and mixtures thereof.

18. The apparatus of claim 16, wherein the one or more acid catalysts are homogeneous or heterogeneous acid catalysts.

19. The apparatus of claim 16, where the one or more acid catalysts are heterogeneous acid catalysts, present in a packed tray within the manufacturing apparatus.

20. The apparatus of claim 16, wherein the one or more acid catalysts are selected from the group consisting of mineral acids, sulfonic acids, carboxylic acids, and mixtures thereof.

21. The apparatus of claim 16, wherein the one or more acid catalysts are selected from the group consisting of a boron trihalide, an organoborane, an aluminum trihalide, methanesulfonic acid, ethanesuifonic acid, benzenesulfonic acid, p-toluene sulfonic acid, trifiuorom ethanesuifonic acid, a boric acid, hydrochloric acid, hydroiodic acid, hydrobromic acid, perchloric acid, nitric acid, sulfuric acid, fluorosulfuric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, carbonic acid, fonnic acid, benzoic acid, and mixtures and derivatives thereof.

22. The apparatus of claim 16, wherein the one or more acid catalysts comprise a solid support having an acidic functionality attached thereto, wherein the acidic functionality is selected from the group consisting of a boron trihalide, an organoborane, an aluminum trihalide, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluene sulfonic acid, trifiuoromethanesulfonic acid, a boric acid, hydrochloric acid, hydroiodic acid, hydrobromic acid, perchloric acid, nitric acid, sulfuric acid, fluorosulfuric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, carbonic acid, formic acid, benzoic acid, and mixtures and derivatives thereof.

23. The apparatus of claim 16, wherein the one or more solid catalysts is selected from the group consisting of Zirconia, alpha and gamma alumina, and zeolites,

24. The apparatus of claim 16 wherein the apparatus is a gas scrubbing unit.

25. The apparatus of claim 24, wherein the gas scrubbing unit comprises a centrifugal-type scrubber, spray scrubber, impingement-type scrabber, packed tower-based scrubber, venturi-type scrubber, eductor venturi-type scrubber, film tower-based scrubber, scrubber with rotating elements, or a combination thereof.

26. The apparatus of one of claims 16-25 wherein the separation device is selected from the group consisting of: a filter, a decanter, a distillation column, or combination thereof.