Process for the production of methyl glycolate

Abstract

The present invention relates to a process for producing a feedstock chemical. More specifically, the present invention relates to a process for producing methyl glycolate, processes for producing compounds from methyl glycolate, and compounds obtained or obtainable from said processes. The process of the invention comprises the step of simultaneously separating methyl glycolate as a crude methyl glycolate stream and light components as a light fraction from an esterification reaction. The process of the invention may be used to produce methyl glycolate which may be converted into polyglycolic acid, glycolic acid, or monoethylene glycol.

Description

[0001] P102650GB01

[0002] Process and Product

[0003] Field of the Invention

[0004] The present invention relates to a process for producing a feedstock chemical. More specifically, the present invention relates to a process for producing methyl glycolate, glycolic acid, monoethylene glycol, and polyglycolic acids. In other aspects the present invention relates to methyl glycolate, glycolic acid, monoethylene glycol, and polyglycolic acids obtained or obtainable from the process.

[0005] Background of the Invention

[0006] There are clear environmental drivers to reducing or eliminating the use of non-degradable plastics in single-use application. Over the coming years, legislation is likely to lead to a significant increase in demand for biodegradable polymers, especially for single use applications.

[0007] Methyl glycolate and glycolic acid may be formed as important intermediates in the formation of a multitude of products, including polyglycolic acids and monoethylene glycol.

[0008] Polyglycolic acid, and its derivatives, have been identified as being a promising biodegradable material for single use applications; having attractive physical properties and process economics. One route to producing polyglycolic acids is from the polymerisation of glycolic acid or methyl glycolate.

[0009] Mono ethylene glycol is typically industrially produced from ethylene via an ethylene oxide intermediate. The ethylene oxide reacts with water to produce mono ethylene glycol.

[0010] However, other routes are available, including the hydrogenolysis of dimethyl oxalate (DMO), obtained for example via the oxidation of carbon monoxide with methyl nitrate, or the hydrogenation of methyl glycolate.

[0011] Methyl glycolate can be obtained for example by reacting 1 ,2-diols, or a 1 ,2-diol and a primary alcohol, with oxygen. Methyl glycolate can also be obtained from the esterification of glycolic acid with methanol.

[0012] Processes for the production of glycolic acid, methyl glycolate, and mono ethylene glycol are offered by Johnson Matthey Davy Technologies and involve the reaction of formaldehyde with carbon monoxide to produce glycolic acid in the presence of a catalyst. Light components (e.g. formaldehyde and water) may be removed to yield a crude glycolic acid.P102650GB01

[0013] The glycolic acid may be esterified with methanol to produce methyl glycolate. Methyl glycolate may be esterified to produce polyglycolic acid or hydrogenated to form mono ethylene glycol. Alternatively, methyl glycolate may be converted back to a purified glycolic acid, as described in WO2018 / 051115A1, before being polymerised to form polyglycolic acid or hydrogenated to form mono ethylene glycol. W02019002839A1 describes a process for producing and purifying mono ethylene glycol.

[0014] Typically, when producing methyl glycolate, following glycolic acid formation, the steps of light component removal (e.g. formaldehyde and water), esterification with methanol, and recovery of methyl glycolate are carried out as three distinct stages. In particular, the esterification reaction to produce methyl glycolate may be carried out at elevated temperatures and increased pressures to prevent the volatilisation of reagents (e.g. methanol). However, doing so increases the capital and operational cost of the plant, requiring a larger number of vessels arranged in series. These costs are compounded by the need for highly expensive protective coatings (e.g. zirconium coatings) on process equipment to prevent corrosion.

[0015] There remains a need for improved processes for the production of methyl glycolate and glycolic acid as important intermediates in the production of mono ethylene glycol and polyglycolic acids.

[0016] Summary of the Invention

[0017] Accordingly, the present invention provides a process for producing methyl glycolate which can be implemented at lower capital and operational costs, and which provides improved selectivity to methyl glycolate by reducing the formation of by-products.

[0018] In a first aspect, the present invention provides a process for producing methyl glycolate, the process comprising the steps of:

[0019] i) providing a glycolic acid stream comprising glycolic acid and water;

[0020] ii) combining the glycolic acid stream with a methanol stream comprising methanol; iii) reacting the glycolic acid in the glycolic acid stream with the methanol in the methanol stream in an esterification reaction in the presence of a catalyst to produce methyl glycolate and light components comprising methanol; and iv) simultaneously separating the methyl glycolate as a crude methyl glycolate stream and the light components as a light fraction from the esterification reaction.P102650GB01

[0021] It has surprisingly been found that methyl glycolate can be produced from the esterification reaction between glycolic acid and methanol whilst employing simultaneous separation of the methyl glycolate and the light components comprising methanol. It has surprisingly been found that the presence of methanol in the simultaneous separation increases the ease by which methyl glycolate can be recovered from the esterification reaction by lowering the temperature at which the methyl glycolate may be volatilised. Moreover, it has surprisingly been found that where simultaneous separation is used the esterification reaction may be carried out at a lower temperature, resulting in the formation of fewer by-products and impurities. This result is particularly surprising given that removal of methanol from the esterification reaction would be expected to decrease conversion of glycolic acid to methyl glycolate.

[0022] Without being bound by any sort of theory, it is believed that the presence of methanol facilitates and improves the separation of the crude methyl glycolate from the esterification reaction by acting as (in addition to a reagent in the esterification reaction) a stripping agent in the simultaneous separation. Despite methanol being removed from the esterification reaction during the simultaneous separation, it is believed that the process of the first aspect of the invention may operate under high methanol and low methyl glycolate conditions. This is believed to drive the equilibrium esterification reaction towards the desired, methyl glycolate, product and may compensate for the use of a lower temperature than those typically used.

[0023] It is a further surprising advantage of the process of the first aspect of the invention that methyl glycolate may be produced in the esterification from a crude glycolic acid stream. That is, methyl glycolate may be produced without the need to first purify the crude glycolic acid stream. Accordingly, the purification of the methyl glycolate product may be simplified, and may be implemented and operated at lower cost by the removal of expensive purification equipment, such as distillation columns.

[0024] In a second aspect of the invention there is provided a process for producing a polyglycolic acid from the methyl glycolate produced using the process of the first aspect of the invention.

[0025] In a third aspect of the invention there is provided a process for producing monoethylene glycol from the methyl glycolate produced using the process of the first aspect of the invention.P102650GB01

[0026] In a fourth aspect of the invention there is provided polyglycolic acid produced using the process of the second aspect of the invention.

[0027] In a fifth aspect of the invention there is provided monoethylene glycol produced using the process of the third aspect of the invention.

[0028] In a sixth aspect of the invention there is provided a process for producing purified glycolic acid from the methyl glycolate produced using the process of the first aspect of the invention.

[0029] In a seventh aspect of the invention there is provided purified glycolic acid produced using the process of the sixth aspect of the invention.

[0030] Brief Description of the Drawings

[0031] Figure 1 shows the amount of methyl glycolate and methyl methoxyacetate (MMA), in weight percent, produced as a function of esterification reaction temperature in degrees Celsius.

[0032] Detailed Description

[0033] Preferred and / or optional features of the invention will now be set out. Any aspect of the invention may be combined with any other aspect of the invention unless the context demands otherwise. Any of the preferred and / or optional features of any aspect may be combined, either singly or in combination, with any aspect of the invention unless the context demands otherwise. Lower and / or upper limits of any ranges disclosed herein are envisaged to be combinable with one another to provide new ranges, whether explicitly stated or not.

[0034] The process of the first aspect of the invention is a process for producing methyl glycolate.

[0035] Methyl glycolate may synonymously be referred to as methyl 2-hydroxyacetate, methyl 2-hydroxyethanoate, and methyl hydroxyacetate. The structure of methyl glycolate is shown in the below scheme.

[0036]

[0037] P102650GB01

[0038] The process of the invention may be a continuous process for producing methyl glycolate. A continuous process will be understood to differ from a batch or standalone process by virtue of the continuous addition and removal of reagents and products.

[0039] The process of the invention comprises the step of providing a glycolic acid stream. The glycolic acid stream comprises glycolic acid and water.

[0040] Glycolic acid may be present in the glycolic acid stream in an amount of from 50 wt% to 75 wt%, such as 60 wt% to 70 wt%, relative to the glycolic acid stream.

[0041] The glycolic acid stream comprises water. Water may be present in the glycolic acid stream in an amount of from 5 wt% to 30 wt% water, such as from 10 wt% to 20 wt% water, relative to the glycolic acid stream.

[0042] The glycolic acid stream may comprise other components such as diglycolic acid.

[0043] The process of the invention comprises the step of combining the glycolic acid stream with a methanol stream comprising methanol.

[0044] The methanol stream may comprise methanol and trace impurities such as water.

[0045] Preferably, the methanol stream may comprise methanol in an amount of 99.5 wt% or greater, such as 99.7 wt% or greater. The methanol stream may be derived from a recycle from elsewhere in the process. Accordingly, the methanol stream may further comprise trace recycle components such as water, methyl formate, and / or dimethoxy methane.

[0046] The process of the invention comprises the step of reacting the glycolic acid in the glycolic acid stream with methanol in the methanol stream in the presence of a catalyst in an esterification reaction to produce a methyl glycolate and light components comprising methanol.

[0047] The esterification reaction will be understood to be the reaction between the glycolic acid and the methanol to form the methyl glycolate and water in the presence of the catalyst.

[0048] The catalyst may preferably be an acid catalyst. The catalyst may be a catalyst suitable for catalysing the esterification reaction of glycolic acid with methanol to produce methyl glycolate. In preferred processes of the invention the catalyst may be an acid catalyst selected from sulfuric acid (H2SO4), triflic acid, sulfonic acids (e.g. methylsulfonic acid),P102650GB01

[0049] ethanesulfonic acid, para-toluene sulfonic acid, perfluorooctanesulfonic acid, phosphorus based acids (e.g. as phosphonic acid and ethyl phosphonic acid), and hydrochloric acid, preferably sulfuric acid. In preferred processes of the invention the catalyst in the esterification reaction may be the same catalyst used in the preparation of the glycolic acid in the glycolic acid stream.

[0050] The catalyst may be present in the glycolic acid stream or may be added to the esterification reaction separately. For example, the catalyst may be provided in the glycolic acid stream and may be the same catalyst used in the preparation of the glycolic acid in the glycolic acid stream.

[0051] The relative molar flow rate of the methanol stream to the glycolic acid stream to the esterification reaction may be from 1.1 : 1 to 20: 1 , for example from 1.1:1 to 15: 1 , 1.1:1 to 10:1, or 1.1:1 to 5:1.

[0052] The methanol stream of the process of the first aspect of the invention functions as a reagent in the esterification reaction and as a stripping agent in the simultaneous separation of the methyl glycolate. Consequently, the flow rate, in moles of methanol per hour, of the methanol stream may be higher than the stoichiometry required by the esterification reaction. Consequently, methanol may be present in the esterification reaction in an excess relative to the stoichiometric requirement.

[0053] In addition to methyl glycolate, other components may be present in the esterification reaction. The other components may be by-products formed during the esterification reaction, by-products formed in an upstream process, or unreacted components from an upstream process (e.g. from the production of the glycolic acid). The other components may include dimethyl ether, dimethoxy methane, methoxyacetic acid, methyl methoxyacetate, dimethylester diglycolic acid, diglycolic acid, formic acid, formaldehyde, oligomers of glycolic acid, and methyl formate.

[0054] The light components comprise methanol. The light components may further comprise one or more of the other components from the esterification reaction with a boiling point lower than that of methyl glycolate. For example, the light components may further comprise one or more of water, dimethyl ether, dimethoxy methane, formic acid, formaldehyde, and methyl formate.P102650GB01

[0055] The esterification reaction may preferably be carried out at a temperature of 130 °C or less, 125 °C or less, 120 °C or less, or 115 °C or less, preferably 120 °C or less, or 115 °C or less.

[0056] It has surprisingly been found that the simultaneous separation of the methyl glycolate in the presence of methanol can be carried out at a reduced temperature. Accordingly, where simultaneous separation is used, the esterification reaction may also be run at a lower temperature. The use of a lower temperature in the esterification reaction reduces the formation of undesirable by-products, such as ethers, which complicate downstream purification and recycle processes, and which may constitute a loss of material from the process. Moreover, operating at lower temperatures in the esterification reaction significantly reduces the rate of glycolic acid oligomerisation which can lead to reactor and pipework fouling.

[0057] The esterification reaction may preferably be carried out at atmospheric pressure or an absolute pressure of lower than atmospheric pressure. The esterification reaction may be carried out at an absolute pressure of from 200 mbar or more, 300 mbar or more, or 400 mbar or more. The esterification reaction may be carried out at an absolute pressure of atmospheric pressure or less, 800 mbar or less, 700 mbar or less, or 600 mbar or less. For example, the esterification reaction may be carried out at an absolute pressure of from 200 mbar to 800 mbar, from 300 mbar to 700 mbar, or from 400 mbar to 600 mbar.

[0058] The process of the invention comprises the step of simultaneously separating the methyl glycolate as a crude methyl glycolate stream and the light components as a light fraction from the esterification reaction.

[0059] By “simultaneous separation” and “simultaneously separating” it is meant that the methyl glycolate and the light components are continuously (e.g. concurrently) removed from the esterification reaction whilst the esterification reaction proceeds, preferably as the esterification reaction proceeds in a continuous fashion.

[0060] The simultaneous separation of the crude methyl glycolate stream and the light fraction may be a distillation. The simultaneous separation of the crude methyl glycolate stream and the light fraction may preferably be carried out atmospheric pressure or an absolute pressure of lower than atmospheric pressure. The simultaneous separation may be carried out at an absolute pressure of from 200 mbar or more, 300 mbar or more, or 400 mbar or more. The simultaneous separation may preferably be carried out at atmospheric pressure or an absolute pressure of less, 800 mbar or less, 700 mbar or less, or 600 mbar or less. ForP102650GB01

[0061] example, the simultaneous separation may preferably be carried out at an absolute pressure of from 200 mbar to 800 mbar, from 300 mbar to 700 mbar, or from 400 mbar to 600 mbar.

[0062] The simultaneous separation of the crude methyl glycolate stream and the light fraction may be carried out at a temperature of 130 °C or less, 125 °C or less, 120 °C or less, or 115 °C or less, preferably 120 °C or less, or 115 °C or less.

[0063] Preferably, the esterification reaction and the simultaneous separation may be carried out at the same pressure. Preferably, the esterification reaction may be carried out at the same temperature as the simultaneous separation. Preferably, the esterification reaction and the simultaneous separation may be carried out at the same pressure and the same temperature.

[0064] In preferred processes of the present invention the esterification reaction and the simultaneous separation may be carried out in an apparatus. The apparatus may comprise a reactor vessel in fluid communication with a separation means, such as a distillation column, where both the reactor vessel and the separation means (e.g. a distillation column) may be configured to operate at atmospheric pressure or an absolute pressure lower than atmospheric pressure. The reactor vessel and the separation means may be configured to operate at the same pressure as one another. It may be preferred that the apparatus comprises a reactor vessel and a separation means (e.g. a distillation column) configured to operate at the same pressure (e.g. at atmospheric pressure or a pressure lower than atmospheric pressure) and the same temperature as one another, such as those described hereinabove.

[0065] It has surprisingly been found that where the apparatus, as described hereinabove, is used in the process of the invention that the number of pieces of process equipment which are required to produce methyl glycolate can be reduced.

[0066] Where the separation means is a distillation column, the crude methyl glycolate stream may be recovered from an intermediate position of the distillation column, and the light fraction may be recovered at the top of the distillation column.

[0067] It has surprisingly been found that where the esterification reaction and / or the simultaneous separation may be carried out at pressures lower than atmospheric pressure that the amount of methanol required in the process may be decreased. Accordingly, it may be advantageous to carry out the esterification reaction and / or the simultaneous separation atP102650GB01

[0068] pressures lower than atmospheric pressure as this allows a reduction in the size of the reaction equipment used, and a reduced methanol inventory within the process.

[0069] The crude methyl glycolate stream may comprise methyl glycolate in an amount of from 70 wt% to 90 wt%, such as from 75 wt % to 85 wt%, relative to the crude methyl glycolate stream. The crude methyl glycolate stream may comprise impurities such as water, methanol, methyl methoxyacetate, and dimethylester diglycolic acid. Impurities may be present in the crude methyl glycolate stream in an amount of 30 wt% or less, such as 25 wt% or less, relative to the crude methyl glycolate stream.

[0070] The light fraction may be further separated. Light compounds from the light fraction such as methanol may be recycled to the esterification reaction and / or to one or more upstream processes.

[0071] The esterification reaction may produce a heavy by-products stream. The heavy by-products stream may comprise one or more of the by-products from the esterification reaction with a boiling point above that of methyl glycolate. The heavy by-products stream may comprise methyl glycolate, glycolic acid, diglycolic acid, methyl methoxyacetate, methoxy acetic acid, dimethylester diglycolic acid and I or ester oligomers of glycolic and diglycolic acids.

[0072] The heavy by-products stream may comprise the catalyst. The process may comprise the steps of recovering the heavy by-products stream comprising the catalyst. The process may comprise the step of returning the heavy by-products stream comprising the catalyst to one or more upstream processes (e.g. the esterification reaction, or a process used to provide the glycolic acid in the glycolic acid stream). The process may comprise the step of recovering the heavy by-products stream as a purge, such as a purge from the esterification reaction. The process may comprise the step of recovering the heavy by-products stream continuously from the esterification reaction, such as recovering the heavy by-products stream continuously as a purge from the esterification reaction. The step of recovering the heavy by-products stream as a purge may typically be carried out before the heavy-by product stream may be returned to the one or more upstream processes. It will be understood that recovering the heavy by-products stream prevents the build-up of the heavy by-products in the process. The process may comprise the step of separating the catalyst from the heavy by-products stream and returning the catalyst to one or more upstream processes (e.g. the esterification reaction, or a process used to provide the glycolic acid in the glycolic acid stream).P102650GB01

[0073] The crude methyl glycolate stream may be further purified, for example by distillation in one or more distillation columns to obtain a methyl glycolate product.

[0074] In preferred processes of the first aspect of the invention, the process may comprise the step of producing a crude glycolic acid stream and feeding the crude glycolic acid stream to the esterification reaction. The crude glycolic acid stream may be fed to the esterification reaction without any intervening purification steps. That is, the crude glycolic acid stream may be fed to the esterification reaction directly after preparation of the glycolic acid. Where the crude glycolic acid stream may be fed to the esterification reaction it will be understood that the glycolic acid stream comprising glycolic acid is the crude glycolic acid stream comprising glycolic acid.

[0075] It has surprisingly been found that the process of the first aspect of the invention allows the use of a crude glycolic acid stream in producing methyl glycolate. Using a crude glycolic acid stream further reduces the number of purification steps, and associated equipment, required by the process. Thus, not only may the process of the first aspect of the invention proceed with reduced impurity formation in the esterification reaction, but it may proceed using a crude glycolic acid stream and operate with fewer process steps.

[0076] In preferred processes of the first aspect of the invention, the process may comprise the step of producing glycolic acid by the reaction of carbon monoxide and formaldehyde in the presence of a catalyst to form the glycolic acid stream or the crude glycolic acid stream. Preferably, the catalyst used to produce glycolic acid from the formaldehyde and the carbon monoxide is the same catalyst as used in the esterification reaction between the glycolic acid of the glycolic acid stream and the methanol of the methanol stream.

[0077] In preferred processes of the first aspect of the invention, the process may comprise the step of purifying the crude methyl glycolate stream to produce a purified methyl glycolate. The step of purifying the crude methyl glycolate stream to produce a purified methyl glycolate may be achieved by any method known in the art, suitably by distillation.

[0078] In a second aspect of the invention there is provided a process for producing polyglycolic acid. Accordingly, in preferred processes of the invention, the process of the first aspect of the invention may comprise the additional step of converting the methyl glycolate to a polyglycolic acid, or a derivative therefore. Methyl glycolate may be converted to a polyglycolic acid, or a derivative thereof, by a catalysed frans-esterification known in the art, for example, frans-esterification using a dioctyl tin catalyst. Alternatively, the methyl glycolateP102650GB01

[0079] may be converted into a glycolic acid solution and the glycolic acid converted to polyglycolic acid, or a derivative thereof, by means of an autothermal polycondensation reaction.

[0080] In a third aspect of the invention there is provided a process for producing mono ethylene glycol from the methyl glycolate produced using the process of the first aspect of the invention. Accordingly, the process of the first aspect of the invention may comprise the further step of converting the methyl glycolate into monoethylene glycol. Methods of producing monoethylene glycol from methyl glycolate are described in W02019 / 002839A1 and US7615671B2, the entire contents of which is incorporated herein by reference.

[0081] In a fourth aspect of the present invention there is provided polyglycolic acid, or a derivative thereof, obtained or obtainable from the process of the second aspect of the invention.

[0082] In a fifth aspect of the present invention there is provided a monoethylene glycol obtained or obtainable from the process of the third aspect of the invention.

[0083] In a sixth aspect of the invention there is provided a process for producing purified glycolic acid from the methyl glycolate produced using the process of the first aspect of the invention. Accordingly, in preferred processes of the invention, the process of the first aspect of the invention may comprise the additional step of contacting the purified methyl glycolate with water, hydrolysing the methyl glycolate to produce glycolic acid and methanol, and separating the purified glycolic acid. A suitable method for converting methyl glycolate to glycolic acid is disclosed in WO2018 / 051115A1, the entire contents of which is incorporated herein by reference.

[0084] In a seventh aspect of the invention there is provided purified glycolic acid produced using the process of the sixth aspect of the invention.

[0085] Examples

[0086] Abbreviations

[0087] MG - methyl glcyolate

[0088] MAA - methoxy acetic acid

[0089] MMA - methyl methoxyacetate

[0090] GA - glycolic acid

[0091] SA - sulfuric acid

[0092] DGA - diglycolic acid

[0093] DMDGA - dimethyl diglycolic acidP102650GB01

[0094] Examples 1 to 3 - Simultaneous Esterification and Separation at Atmospheric Pressure To a reaction vessel, heated to afford an internal process operating temperature of 110 °C to 130 °C and under atmospheric pressure, was continuously fed a glycolic acid stream, of the composition shown in Table 1 and an alcohol steam, introduced into the process liquid via a dip leg I sparge system, consisting of AA grade methanol.

[0095] The resultant vapour stream (hereafter called the overheads stream) was condensed measured, and analysed, with the averaged product composition over the entire test run shown in Table 2.

[0096] To maintain a constant liquid volume in the reaction vessel a continuous liquid purge (hereafter referred to as the bottoms stream) was taken used a peristaltic pump via a submerged dip leg then measured, and analysed, with the averaged product composition over the entire test run shown in Table 2.

[0097] The conversion (wt%) of glycolic acid was taken as:

[0098] 1 - [Mass of glycolic acid out (g IT1) I Mass of glycolic acid in (g IT1)] x 100

[0099] Table 1 - Glycolic Acid Stream Composition

[0100]

[0101] Table 2 - Operating Conditions and Results

[0102]

[0103] P102650GB01

[0104]

[0105] Examples 4 to 7 - Simultaneous Esterification and Separation at Atmospheric Pressure

[0106] To a reaction vessel, heated to afford an internal process operating temperature of 120°C and under a reduced pressure, measured and controlled using a vacuum pump and pressure transducer located directly downstream of the overheads condenser, was continuously fed an glycolic acid stream, of the composition shown in Table 1 and an alcohol steam, introduced into the process liquid via a dip leg I sparge system, consisting of AA grade methanol.

[0107] The resultant vapour stream (overheads stream) was condensed measured, and analysed, with the averaged product composition over the entire test run shown in Table 3.

[0108] To maintain a constant liquid volume in the reaction vessel a continuous liquid purge (hereafter referred to as the bottoms stream) was taken used a peristaltic pump via a submerged dip leg then measured, and analysed, with the averaged product composition over the entire test run shown in Table 3.

[0109] The conversion (wt%) of glycolic acid was taken as:

[0110] 1 - [Mass of glycolic acid out (gtr1) / Mass of glycolic acid in (gh-1)] x 100

[0111] Table 3 - Operating Conditions and ResultsP102650GB01

[0112]

[0113] Examples 1 to 7 show that methyl glycolate can be produced from a ‘crude’ glycolic acid stream in an esterification reaction with simultaneous separation of methyl glycolate.

[0114] Examples 1 to 7 further show that at pressures lower than atmospheric pressure that the amount of methanol in the overheads can be reduced whilst maintaining high levels of conversion, and recovery, of methyl glycolate.

[0115] Example 8

[0116] Example 8 shows the effect of using higher esterification reaction temperatures.

[0117] To a glass reaction vessel, fitted with an overheads vapour condenser and bottoms liquid removal via a submerged dip leg, was continuously added a liquid feed simulating the productP102650GB01

[0118] from an esterification reactor, as shown in Table 4, at a rate sufficient to afford a residence time of 10 minutes in the reactor.

[0119] Table 4 - Feed Composition

[0120]

[0121] Operating under atmospheric pressure the temperature was slowly increased. The resulting overheads were condensed, weighed and analysed by GC. The temperature was then increased and the process repeated.

[0122] The results from this experiment are presented in Figure 1 which shows the weight percentage of methyl glycolate and methyl meth oxy acetate produced as a function of temperature. The concentration of methyl glycolate in the overhead product stream remained relatively constant to 150°C, at higher temperatures the concentration reduced sharply due to increase in unwanted by-products. The concentration of highly undesirable methyl methoxyacetate increased throughout the experiment, reaching 15 wt% at 159 °C.

Claims

P102650GB01Claims1. A process for producing methyl glycolate, the process comprising the steps of:i) providing a glycolic acid stream comprising glycolic acid and water;ii) combining the glycolic acid stream with a methanol stream comprising methanol; iii) reacting the glycolic acid in the glycolic acid stream with the methanol in the methanol stream in the presence of a catalyst in an esterification reaction to produce methyl glycolate and light components comprising methanol; and iv) simultaneously separating the methyl glycolate as a crude methyl glycolate stream and the light components as a light fraction from the esterification reaction.

2. A process according to claim 1, wherein the esterification reaction is carried out at atmospheric pressure or an absolute pressure of from 200 mbar to 800 mbar, from 300 mbar to 700 mbar, or from 400 mbar to 600 mbar.

3. A process according to claim 1 or claim 2, wherein the esterification reaction is carried out at a temperature of 130 °C or less, 125 °C or less, 120 °C or less, or 115 °C or less.

4. A process according to any one of the preceding claims, wherein the simultaneous separation is carried out at atmospheric pressure or an absolute pressure of from 200 mbar to 800 mbar, from 300 mbar to 700 mbar, or from 400 mbar to 600 mbar.

5. A process according to anyone of the preceding claims, wherein the simultaneous separation is carried out a temperature of 130 °C or less, 125 °C or less, 120 °C or less, or 115 °C or less.

6. A process according to any one of the preceding claims, wherein the esterification reaction and the simultaneous separation are carried out under the same pressure.

7. A process according to any one of the preceding claims, wherein the esterification reaction and the simultaneous separation are carried out at the same temperature.

8. A process according to any one of the preceding claims, wherein the esterification reaction and the simultaneous separation are carried out at the same pressure and temperature.P102650GB019. A process according to any one of the preceding claims, wherein the esterification reaction and the simultaneous separation are carried out in an apparatus, wherein the apparatus comprises a reactor vessel in fluid communication with a separation means, and wherein both the reactor vessel and the separation means are configured to operate at atmospheric pressure or an absolute pressure lower than atmospheric pressure.

10. A process according to claim 9, wherein the reactor vessel and the separation means are configured to operate at the same pressure and / or the same temperature.

11. A process according to any one of the preceding claims, wherein the simultaneous separation is a distillation.

12. A process according to any one of the preceding claims, wherein the process comprises the step of producing a crude glycolic acid stream and feeding the crude glycolic acid stream to the esterification reaction.

13. A process according to claim 12, wherein the crude glycolic acid stream is fed to the esterification reaction without any intervening purification steps.

14. A process according to claim 12 or claim 13, wherein the process comprises the step of producing glycolic acid by the reaction of carbon monoxide and formaldehyde in the presence of a catalyst to form the glycolic acid stream or the crude glycolic acid stream.

15. A process according to any one of the preceding claims, wherein the catalyst is an acid catalyst, or a catalyst suitable for catalysing the esterification reaction of glycolic acid with methanol to produce methyl glycolate.

16. A process according to any one of the preceding claims, wherein the catalyst is an acid catalyst selected from sulfuric acid (H2SO4), triflic acid, sulfonic acids (e.g. methylsulfonic acid), ethanesulfonic acid, para-toluene sulfonic acid, perfluorooctanesulfonic acid, phosphorus based acids (e.g. as phosphonic acid and ethyl phosphonic acid), and hydrochloric acid, preferably sulfuric acid.

17. A process according to any one of the preceding claims, wherein the catalyst in the esterification reaction is the same catalyst used in the preparation of the glycolic acid in the glycolic acid stream.P102650GB0118. A process according to any one of the preceding claims, wherein the process comprises the further step of purifying the crude methyl glycolate stream to produce a purified methyl glycolate.

19. A process according to any one of the preceding claims, wherein the process comprises the further step of converting the methyl glycolate to a polyglycolic acid, or a derivative thereof.

20. A process according to any one of claims 1 to 18, wherein the process comprises the further step of converting the methyl glycolate to monoethylene glycol.

21. A polyglycolic acid, or a derivative thereof, obtained or obtainable from the process of claim 19.

22. A monoethylene glycol obtained or obtainable from the process of claim 20.

23. A process according to claim 18 or claim 19, the process comprising the additional steps of contacting the purified methyl glycolate with water, hydrolysing the methyl glycolate to produce glycolic acid and methanol, and separating a purified glycolic acid.

24. A purified glycolic acid obtained or obtainable from the process of claim 23.

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