WO2016151488A1

WO2016151488A1 - Integrated method and apparatus for the production of aryl carbonates

Info

Publication number: WO2016151488A1
Application number: PCT/IB2016/051615
Authority: WO
Inventors: Sergio Ferrer NADAL
Original assignee: Sabic Global Technologies B.V.
Priority date: 2015-03-23
Filing date: 2016-03-22
Publication date: 2016-09-29
Also published as: CN107428670A; KR20170129909A

Abstract

In an embodiment, a method for producing an alkyl aryl carbonate, comprises providing a purified dialkyl carbonate stream and a first purified alkanol stream; reacting the purified dialkyl carbonate stream to produce a diaryl carbonate stream, and (i) an aromatic alcohol stream and a second dialkyl carbonate stream, or (ii) a second dialkyl carbonate stream, and separating an aromatic alcohol from the second dialkyl carbonate stream to produce an aromatic alcohol stream comprising the aromatic alcohol; directing a first portion of aromatic alcohol stream to a dialkyl carbonate purification unit; reacting the second dialkyl carbonate stream, the second portion of aromatic alcohol stream, and a first aromatic alcohol feed stream to produce an alkanol stream, and an alkyl aryl carbonate stream; and purifying the alkanol stream and the first portion stream in the dialkyl carbonate purification unit to provide the purified dialkyl carbonate stream and the first purified alkanol stream; wherein purifying comprises extracting the dialkyl carbonate with the aromatic alcohol.

Description

INTEGRATED METHOD AND APPARATUS FOR THE PRODUCTION OF ARYL CARBONATES

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of European application number 15382137 filed on March 23, 2015. The related application is incorporated herein in its entirety by reference.

BACKGROUND

[0002] The present disclosure relates generally to a method and an apparatus for the production of aryl carbonates, such as alkyl aryl carbonates and diaryl carbonates, and especially to a method and an apparatus for the production of aryl carbonates.

[0003] Diaryl carbonates such as diphenyl carbonate (DPC) are important reactants in the production of polycarbonates. Polycarbonates can be manufactured by polymerization of an aromatic dihydroxy compound such as bisphenol A (BPA), with a diaryl carbonate such as DPC. Polycarbonates are useful materials valued for their physical and optical properties. As the uses for polycarbonates have increased, the efficient production of diaryl carbonates has become of greater significance. A phosgene-free process involves first reacting a dialkyl carbonate such as dimethyl carbonate (DMC) with an aromatic alcohol such as phenol in the presence of a transesterification catalyst, to produce an alkyl aryl carbonate (e.g., phenyl methyl carbonate (PMC)) and an aliphatic monohydric alcohol (alkanol) (e.g., methanol or ethanol). In the second step, two molecules of the alkyl aryl carbonate undergo a disproportionation reaction to produce one molecule of diaryl carbonate (e.g., DPC) and one molecule of the starting material dialkyl carbonate (e.g., DMC).

[0004] Phosgene-free industrial processes for producing the dialkyl carbonate starting material include oxidative carbonylation of an alkanol, alkyl nitrate carbonylation, direct synthesis from C(¾, and epoxide carbonylation of an alcohol. In the epoxide carbonylation process, an alkylene oxide (e.g., ethylene oxide) is reacted with carbon dioxide in the presence of a catalyst to produce an alkylene carbonate (e.g., ethylene carbonate or propylene carbonate), which is then transesterified with an alkanol (e.g., methanol or ethanol) to produce the dialkyl carbonate (e.g., dimethyl carbonate) and an alkylene glycol (e.g., ethylene glycol), which itself is a valuable by-product. [0005] Despite intensive work to develop and improve these phosgene-free industrial processes, there remains a continued need for methods and apparatuses for the production of diaryl carbonates that have reduced energy consumption while still producing high quality diaryl carbonates, particularly, DPC. It would be a further advantage if the methods and apparatuses could be adopted with lower investment costs.

BRIEF DESCRIPTION

[0006] Disclosed herein is a method and a system for making an aryl carbonate.

[0007] In an embodiment, a method for producing an alkyl aryl carbonate, comprises reacting an alkylene carbonate and an alkanol in the presence of a first transesterification catalyst in a dialkyl carbonate reactor to produce a first dialkyl carbonate product stream comprising a dialkyl carbonate and unreacted alkanol, and an alkylene glycol product stream comprising an alkylene glycol and unreacted alkanol; purifying the first dialkyl carbonate product stream in a dialkyl carbonate purification unit to provide a purified dialkyl carbonate stream and a first purified alkanol stream; reacting the purified dialkyl carbonate stream in the presence of a second transesterification catalyst in a diaryl carbonate reactor to produce a diaryl carbonate product stream comprising a diaryl carbonate product by disproportionation, and (i) an aromatic alcohol product stream comprising an aromatic alcohol product, a second dialkyl carbonate product stream comprising the dialkyl carbonate and an alkyl aryl ether, or (ii) a second dialkyl carbonate product stream comprising the dialkyl carbonate, an aromatic alcohol product, and an alkyl aryl ether, and separating the aromatic alcohol product from the second dialkyl carbonate product stream to produce an aromatic alcohol product stream comprising the aromatic alcohol product; directing an amount (X wt%) as a first portion stream of aromatic alcohol product stream to the dialkyl carbonate purification unit and directing an amount (100 wt%-X wt%) as a second portion stream of the aromatic alcohol product stream to an alkyl aryl carbonate reactor, wherein X wt% is greater than 0; reacting the second dialkyl carbonate product stream, the second portion stream, and a first aromatic alcohol feed stream in the presence of the second transesterification catalyst in an alkyl aryl carbonate reactor to produce an alkanol product stream comprising an alkanol product and unreacted dialkyl carbonate, and an alkyl aryl carbonate product stream comprising an alkyl aryl carbonate product and unreacted aromatic alcohol; and purifying the alkanol product stream and the first portion stream in the dialkyl carbonate purification unit to provide the purified dialkyl carbonate stream and the first purified alkanol stream; wherein purifying comprises extracting the dialkyl carbonate with the aromatic alcohol.

[0008] In another embodiment, a system for production of an alkyl aryl carbonate comprises a dialkyl carbonate reactor, an alkyl aryl carbonate reactor, a dialkyl carbonate purification unit, and a diaryl carbonate reactor. The dialkyl carbonate reactor comprises an alkanol inlet, an alkylene carbonate inlet, an alkylene diol outlet, and a first alkanol/dialkyl carbonate outlet in fluid communication with a dialkyl carbonate inlet of a dialkyl carbonate purification unit. The dialkyl carbonate purification unit comprises the dialkyl carbonate inlet, a first purified alkanol outlet, a purified dialkyl carbonate outlet; and an unit aromatic alcohol inlet. The diaryl carbonate reactor comprises a purified dialkyl carbonate inlet in fluid communication with the purified dialkyl carbonate outlet, an alkyl aryl ether/dialkyl carbonate outlet in fluid communication with an alkyl aryl ether/dialkyl carbonate inlet of the alkyl aryl carbonate reactor, an aromatic alcohol outlet in fluid communication with the unit aromatic alcohol inlet of the dialkyl carbonate purification unit and optionally with a reactor aromatic alcohol inlet of the alkyl aryl carbonate reactor, and a diaryl outlet. The alkyl aryl carbonate reactor comprising the reactor aromatic alcohol inlet, the alkyl aryl ether/dialkyl carbonate inlet in fluid communication with the alkyl aryl ether/dialkyl carbonate outlet of the diaryl carbonate reactor, a second alkanol/dialkyl carbonate outlet in fluid communication with an alkanol/dialkyl carbonate inlet of the dialkyl carbonate purification unit, and an alkyl aryl carbonate outlet.

[0009] In yet another embodiment, a system for production of an alkyl aryl carbonate comprises a dialkyl carbonate reactor, an alkyl aryl carbonate reactor, a dialkyl carbonate purification unit, a diaryl carbonate reactor; and an aromatic alcohol separation unit. The dialkyl carbonate reactor comprises an alkanol inlet, an alkylene carbonate inlet, an alkylene diol outlet, and a first alkanol/dialkyl carbonate outlet in fluid communication with a dialkyl carbonate inlet of a dialkyl carbonate purification unit. The dialkyl carbonate purification unit comprises the dialkyl carbonate inlet, a first purified alkanol outlet, a purified dialkyl carbonate outlet; and an unit aromatic alcohol inlet. The diaryl carbonate reactor comprises a purified dialkyl carbonate inlet in fluid communication with the purified dialkyl carbonate outlet, the alkyl aryl ether/dialkyl carbonate outlet in fluid communication with a separation inlet of the aromatic alcohol separation unit, the aromatic alcohol separation unit having an aromatic outlet in fluid communication with the unit aromatic alcohol inlet and an a separated alkyl aryl ether/dialkyl carbonate outlet in fluid communication with the reactor aromatic alcohol inlet, and a diaryl outlet. The alkyl aryl carbonate reactor comprising the reactor aromatic alcohol inlet, a second alkanol/dialkyl carbonate outlet in fluid communication with an alkanol/dialkyl carbonate inlet of the dialkyl carbonate purification unit, and an alkyl aryl carbonate outlet.

[0010] The above described and other features are exemplified by the following figures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The following Figures are exemplary and non-limiting embodiments, wherein:

[0012] FIG. 1 schematically depicts an embodiment of a prior art plant design for the production of dialkyl and diaryl carbonates;

[0013] FIG. 2 schematically depicts an embodiment of a plant design for the production of dialkyl carbonates, alkyl aryl carbonates, and diaryl carbonates; and

[0014] FIG. 3 schematically depicts an embodiment of a plant design for the production of dialkyl carbonates, alkyl aryl carbonates, and diaryl carbonates.

DETAILED DESCRIPTION

[0015] As described above, the epoxide carbonylation process, for example, can be used to produce a dialkyl carbonate, where an alkylene oxide is reacted with carbon dioxide in the presence of a catalyst to produce an alkylene carbonate that can then be transesterified with an alkanol to produce the dialkyl carbonate and an alkylene glycol. The dialkyl carbonate can then be reacted with an aromatic alcohol in the presence of a transesterification catalyst to produce an alkyl aryl carbonate and an alkanol. Disproportionation of the alkyl aryl carbonate can then be used to produce a diaryl carbonate. An exemplary prior art system 100 is shown schematically in FIG. 1, and comprises a dialkyl carbonate reactor 110 that carries out transesterification of the alkylene carbonate in stream I with an alkanol in stream J to produce a dialkyl carbonate stream A; an alkyl aryl carbonate reactor 140 for carrying out the transesterification of dialkyl carbonate to produce an alkyl aryl carbonate stream B; and a diaryl carbonate reactor 180 for carrying out the disproportionation of alkyl aryl

polycarbonate to produce a diaryl carbonate stream C. The various limitations and conditions associated with these processes have resulted in relatively complex apparatuses to carry them out. [0016] For example, because the yield of the transesterification reaction is strongly limited by the equilibrium conversion, a molar excess of alkanol is typically used to overcome this thermodynamic limitation. The unreacted alkanol in dialkyl carbonate stream A can be recovered as a distillate stream D in a separate distillation unit 120 and recycled, but needs to be of high purity. Even further, distillation to purify the alcohol and produce dialkyl carbonate stream H cannot be efficiently accomplished at atmospheric pressure where the alkanol and the dialkyl carbonate form an azeotrope at low temperature and pressure (e.g., methanol or ethanol and dimethyl carbonate form an azeotrope at 63 degrees Celsius (°C) and 1 bar(absolute (abs))). Therefore, operating at a higher pressure is required in order to enrich the methanol or ethanol content in the purification column, as described, for example, in US 8,049,028. Another example is in the transesterification of the dialkyl carbonate stream with an aromatic alcohol to produce the alkyl aryl carbonate. In that process, the dialkyl carbonate stream H is transesterified in a alkyl aryl carbonate reactor 140, and a byproduct stream E comprising unreacted dialkyl carbonate, alkanol, and is distilled in high-pressure distillation column 150, again under pressure, to recover relatively pure alkanol stream F and unreacted dialkyl carbonate stream G. In some embodiments, byproduct stream E further comprises the aromatic alcohol in trace amounts (less than or equal to 2 weight percent (wt )), or larger amounts, for example, 5 to 30 wt of the byproduct stream E.

[0017] Processes and apparatuses for the production of alkyl aryl carbonates were discovered that can improve the overall efficiency of the process, including reducing energy consumption and initial capital costs. In particular, the improvement can comprise an integration of the dialkyl carbonate and alkyl aryl carbonate production processes by merging the purification columns used in the production of the dialkyl carbonate and the alkyl aryl carbonate plants to a single distillation column. In other words, output streams from the dialkyl carbonate production column and from the alkyl aryl carbonate production column distillates are sent to a single separation unit. Outputs obtained from this unit are a dialkyl carbonate -rich stream that can advantageously be directly used in the production of the alkyl aryl carbonate and a purified alkanol. The purity of the alkanol can be adjusted by adjusting the operating conditions of the separation unit. The number of distillation columns needed to purify the products and recycle the unreacted reactants can therefore be reduced. When used in the production of diaryl carbonates, the overall process is more efficient, and has reduced costs. [0018] It was also discovered that the process for the production of alkyl aryl carbonates can comprise directing a purified dialkyl carbonate stream from a dialkyl carbonate purification unit to a diaryl carbonate reactor and that the diaryl carbonate reactor can further purify an aromatic alcohol product stream comprising an aromatic alcohol. At least a portion of the aromatic alcohol from the diaryl carbonate reactor can be added to the single diaryl carbonate purification unit and an alkyl aryl carbonate reactor. In this manner, the aromatic alcohol produced in the diaryl carbonate reactor can be used to break the azeotrope formed between the dialkyl carbonate and the alkyl alcohol that are otherwise difficult to separate.

[0019] A more complete understanding of the components, processes, and apparatuses disclosed herein can be obtained by reference to the accompanying FIG. 2 and FIG. 3, which are schematic representations based on convenience and the ease of demonstrating the present disclosure, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments. Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure.

[0020] FIG. 2 and FIG. 3 schematically depict systems 200 and 300 comprising three reactors (e.g., reactive distillation columns), and one dialkyl purification unit for purification the distillate from two different reactive columns. Previously, two or more columns were typically required, one in a dialkyl carbonate production facility and one in an alkyl aryl carbonate or diaryl carbonate production facility. It is noted that it will be appreciated by persons skilled in the art that the positioning of the various streams/lines as described herein as being, e.g., in the "top", "middle", "bottom", or "side" of a particular column is relative because the actual position at which material is to be introduced or recovered is dependent on the conditions being maintained in the particular column. For example, a stream entering the "bottom" of a column can actually enter several stages above the sump including the reboiler of the column, and a line/stream exiting the "top" of the column can actually exit several stages below the top stage including the condenser of the column. Thus, such terms herein are included for ease of reference to describe a general orientation regarding various columns and lines/streams and such terms are not meant to be limiting to one exact location. Also, although for illustrative purposes, FIG. 2 and FIG. 3 and the accompanying descriptions can depict singular vessels, such as reaction vessels, purification vessels, or mixing vessels, it is understood that multiple vessels in series or parallel can be used where suitable.

[0021] The system 300 as shown in FIG. 3 is similar to that of system 200 except that FIG. 3 illustrates that an aromatic alcohol can be separated from the diaryl carbonate reactor 380 can be used to break the azeotropic mixture of dialkyl carbonate and the alkanol entering dialkyl carbonate purification unit 360. This aromatic alcohol can operate in a loop that can cycle around first portion stream 30, purified dialkyl carbonate stream 16, and aromatic alcohol product stream 28. It is noted that instead of removing aromatic alcohol product stream 28 from a middle portion of diaryl carbonate reactor 380, the aromatic alcohol can be removed with the second dialkyl carbonate product stream 34 and can then be separated in a further separation unit, for example, a distillation column. It is further noted that while FIG. 3 illustrates that both purified dialkyl carbonate stream 16 of dialkyl carbonate purification unit 360 is fed to the diaryl carbonate reactor 380 and that diaryl carbonate reactor 380 purifies aromatic alcohol product stream 28 that only one or the other of the conditions can be applied to system 200.

[0022] The reactors 210, 310, 240, 340, 280, and 380 can each independently be a reactive distillation column and can each have a rectification section and a reaction section in which a chemical reaction occurs. In general, the reaction section of the column can be furnished with packings or fixed internals ("internals" referring herein to the part in the distillation column where gas and liquid are actually brought into contact with one another) to provide at least one reactive distillation stage. For example, the reaction section of a reactive distillation column can provide greater than or equal to 5, such as 5 to 60, reactive stages, specifically, greater than or equal to 10, such as 10 to 40, distillation stages. Known dumped packings and/or arranged packings can be employed. Specifically, packings having a large surface area, good wetting and residence time of the liquid phase, such as, for example, Novolax rings, CY packings, can be used. Fixed internals, such as tray columns also can be employed, and specific examples include sieve trays, valve trays, and bubble-cap trays.

[0023] The systems 200 and 300 as shown in FIG. 2 and FIG. 3, respectively, further contain a dialkyl carbonate purification unit 260, dialkyl carbonate purification unit 360, and an optional alkylene glycol purification unit 230, 330. Each of the purification units can each independently be a high-pressure distillation column. These columns can carry out a separation of materials based upon boiling point, without driving a concurrent chemical reaction. The dialkyl carbonate reactor 210, alkyl aryl carbonate reactor 240, and diaryl carbonate reactor 280 and dialkyl carbonate purification unit 260 and alkylene glycol purification unit 230 can be interconnected by a series of feed/recycle lines, which serve to transport streams comprising reactants and/or products. The dialkyl carbonate reactor 310, alkyl aryl carbonate reactor 340, and diaryl carbonate reactor 380 and dialkyl carbonate purification unit 360 and alkylene glycol purification unit 330 can be interconnected by a series of feed/recycle lines, which serve to transport streams comprising reactants and/or products. The direction of flow for each line is indicated in the figures. Various valves, heaters, and other fittings can optionally be included with the feed/recycle lines shown in the figures in adapting the design to a particular installation.

[0024] FIG. 2 and FIG. 3 can be used in accordance with a method to produce diaryl carbonate, specifically, DPC, according to embodiments disclosed herein. Although the description of the process is directed to a continuous process, any one or more of the steps can be conducted batch-wise. In the operation of the process, alkylene carbonate stream 18 comprises an alkylene carbonate such as ethylene carbonate or propylene carbonate (EC) and alkanol stream 20 comprises an alkanol such as methanol or ethanol, which can be fresh, recycled, or a combination thereof. When the catalyst is homogeneous, the catalyst can feed together with the alkylene carbonate or the alkanol, or fed in at a position different from both. When the catalyst is heterogeneous, the catalyst can be packed in a desired amount at a desired position of the rector. In an embodiment, the catalyst is a heterogeneous catalyst immobilized on a catalyst bed.

[0025] The alkylene carbonate and the alkanol can be fed continuously to dialkyl carbonate reactor 210, 310, which as shown is a reactive distillation column.

Transesterification is carried out in the presence of the catalyst to produce a diol, specifically, ethylene glycol, and a dialkyl carbonate, specifically, dimethyl carbonate. It is appreciated that the conditions in reactors, such as temperature, pressure and molar ratio of reactant feeds can be selected and optimized to reduce or otherwise control the concentration of the products without undue experimentation.

[0026] A high boiling point reaction mixture (alkylene glycol product stream 22) containing the diol can be continuously withdrawn from a lower portion of the dialkyl carbonate reactor 210, 310 in a liquid form, and a low boiling point reaction mixture (first dialkyl carbonate product stream 2) containing the dialkyl carbonate product and unreacted alkanol can be continuously withdrawn from an upper portion of the column 210, 310 in a gaseous form. [0027] First dialkyl carbonate product stream 2 can be fed to dialkyl carbonate purification unit 260, 360 (e.g., a distillation column as described in more detail below) where it is separated into a column top component (first purified alkanol stream 12) containing the alkanol as a main component and a column bottom component (purified dialkyl carbonate stream 16) containing the dialkyl carbonate as a main component. The first purified alkanol stream 12 can optionally be recycled to the dialkyl carbonate reactor 210, 310 and purified dialkyl carbonate 16 can be to the alkyl aryl carbonate reactor 240 (as illustrated in FIG. 2) or the diaryl carbonate reactor 380 (as illustrated in FIG. 3).

[0028] Optionally, alkylene glycol product stream 22 can be fed to alkylene glycol purification unit 230, 330 to provide a purified alkylene glycol stream 8 and a second purified alkanol stream 14. Here, unreacted alkanol can be separated from produced diol and recycled, for example, to the dialkyl carbonate reactor 210, 310.

[0029] The reaction to produce an alkyl aryl carbonate, specifically, a methyl phenyl carbonate, can be carried out in alkyl aryl carbonate reactor 240, 340, for example, a reactive distillation column as shown. First aromatic alcohol feed stream 24 can comprise a transesterification catalyst and an aromatic alcohol such as phenol that can be fresh, recycled, or a combination thereof. For example, recycled aromatic alcohol (dialkyl carbonate product stream 26) can be used in addition to or in place of the fresh aromatic alcohol. The other starting material, dialkyl carbonate (purified dialkyl carbonate stream 16) can comprise a recycled material from the dialkyl carbonate purification unit 260.

[0030] Purified dialkyl carbonate stream 16 can be fed to, for example, the bottom of alkyl aryl carbonate reactor 240, specifically, to the reboiler. Purified dialkyl carbonate stream 16 can be a liquid or a vapor, depending upon the type of reboiler used. For example, if an external reboiler, e.g., a kettle reboiler, is used, purified dialkyl carbonate stream 16 can enter alkyl aryl carbonate reactor 240 as a vapor.

[0031] First aromatic alcohol feed stream 24 can be fed as a liquid into, e.g., the middle section of alkyl aryl carbonate reactor 240, 340 more specifically, at a location at or near the top of the reactive distillation section. The feed rate streams entering alkyl aryl carbonate reactor 240, 340 can be such that the molar ratio of dialkyl carbonate to aromatic alcohol introduced into alkyl aryl carbonate reactor 240, 340 is 0.1 and 10, specifically, 0.5 and 5, and, more specifically, 0.5 and 3.

[0032] Alkyl aryl carbonate reactor 340 can operate at in the presence of excess phenol. For example, the feed rate streams entering alkyl aryl carbonate reactor 340 can be such that the molar ratio of dialkyl carbonate to aromatic alcohol introduced into alkyl aryl carbonate reactor 340 is 1 :3 to 1 : 1.5, specifically, 1 :2.5 to 1 : 1.5. In this manner, it was surprisingly found that the alkyl aryl carbonate reactor 340 could operate at reduced pressures of 50 to 150 kiloPascal (kPa)(g), specifically, 80 to 125 kPa(g). Alkyl aryl carbonate reactor 340 can operate at a temperature greater than or equal to 140 degrees Celsius (°C), 140 to 500°C, specifically, 200°C to 450°C, and, more specifically, 350°C to 350°C.

[0033] The dialkyl carbonate can be provided in excess through purified dialkyl carbonate stream 16 because the dialkyl carbonate can serve as both a reactant and as a stripping agent, which facilitates removal of the alkanol produced in the transesterification reaction. This removal can increase the rate of production of alkyl aryl carbonate in alkyl aryl carbonate reactor 240, 340. The transesterification reaction can be carried out in alkyl aryl carbonate reactor 240, 340 at, for example, a temperature greater than or equal to 100°C, specifically, greater than or equal to 130°C, and, more specifically, greater than or equal to 140°C. Examples of temperature ranges for carrying out the reaction include, 100°C to 300°C, specifically, 110°C to 270°C, and, more specifically, 120°C to 250°C. The operating pressure at the top of alkyl aryl carbonate reactor 240, 340 can be greater than or equal to 0.5 bar(guage (g)) (50 kPa(g)), specifically, greater than or equal to 2 bar(g) (200 kPa(g)), and, more specifically, greater than or equal to 3 bar(g) (300 kPa(g)).

[0034] Reactant products and unreacted starting materials can be removed from alkyl aryl carbonate reactor 240, 340 in a continuous manner through alkanol product stream 10 and alkyl aryl carbonate product stream 4. Alkanol product stream 10, which can be drawn from the top of alkyl aryl carbonate reactor 240, 340 can comprise unreacted dialkyl carbonate and the alkanol produced in the transesterification reaction, as well as other reactants and by-products, such as the aromatic alcohol. In an embodiment, the alkyl aryl carbonate reactor 240, 340 has a rectification section and a reaction section. The rectification section is an upper section of the reactor 240, 340 above the feeding point of at least one of the reactants, and can comprise, for example, packing or trays. A chemical reaction is generally thought not to occur in the rectification section. The presence of a rectification section can affect the amount the aromatic alcohol in alkanol product stream 10.

Alternatively, alkanol product stream 10 can optionally pass first to an optional rectification column (not shown) for processing and recovery. The rectification section and the optional rectification column also can be furnished with packings or fixed internals to provide, for example, greater than or equal to 3, specifically, greater than or equal to 5, more specifically, 5 to 50, distillation stages. For example, dumped packings and/or arranged packings can be employed. The temperature profile of the optional rectification column (not shown in FIG. 2 and FIG. 3) can be greater than or equal to 10°C, specifically, greater than or equal to 50°C. Examples of temperature ranges for the temperature profile in the optional rectification column are 10°C to 200°C, specifically, 50°C to 110°C. The operating pressure in the optional rectification column can be greater than or equal to 0.1 bar(g) (10 kPa(g)), specifically, greater than or equal to 0.5 bar(g) (50 kPa(g)). Examples of pressure ranges include 0.1 to 10 bar(g) (1000 kPa(g)), specifically, 0.5 to 3 bar(g) (50 to 300 kPa(g)).

[0035] Alkyl aryl carbonate product stream 4, which can be drawn from, e.g., the bottom of alkyl aryl carbonate reactor 240, 340 such as from the reboiler of alkyl aryl carbonate reactor 240, 340 can comprise the alkyl aryl carbonate produced in alkyl aryl carbonate reactor 240, 340 in combination with unreacted starting materials, alkyl aryl ether, and catalyst. As shown in FIG. 2 and FIG. 3, the alkyl aryl carbonate product stream 4 is suitable for use in the production of diaryl carbonates as described next. However, it is to be understood that the alkyl aryl carbonates produced as described herein can be used for other purposes, for example, as a solvent or in the manufacture of other compounds or polymers. In the manufacture of a diaryl carbonate such as DPC, alkyl aryl carbonate product stream 4 can enter the diaryl carbonate reactor 280, 380 e.g., a reactive distillation column as shown, to produce the product diaryl carbonate (e.g., diphenyl carbonate) by disproportionation of the alkyl aryl carbonate. Diaryl carbonate reactor 280, 380 can be operated under conditions effective to further drive the reaction toward the desired diaryl carbonate product, while separating other materials from the product, which can be used for recycle.

[0036] Alkanol product stream 10 comprises an azeotropic mixture of dialkyl carbonate and essentially all of the alkanol produced in the process, as well as aromatic alcohol in trace or greater amounts as described above. Alkanol product stream 10 can be fed to the dialkyl carbonate purification unit 260, 360 where the alkanol is separated as a column top component (first purified alkanol stream 12) and the dialkyl carbonate is separated as a column bottom component (purified dialkyl carbonate stream 16).

[0037] Two streams can be removed from diaryl carbonate reactor 280 and two or three streams can be removed from diaryl carbonate reactor 380. For example, at least three streams can be removed from diaryl carbonate reactor 380: diaryl carbonate product stream 6, aromatic alcohol product stream 28, and second dialkyl carbonate product stream 34. One of the streams is a diaryl carbonate product stream 6, which can be removed from the bottom of diaryl carbonate reactor 280, 380, and can comprise essentially all of (for example, greater than or equal to 99 wt%) the diaryl carbonate produced together with residual catalyst, some unreacted alkyl aryl carbonate, and high-boiling by-products. The diaryl carbonate product stream 6 can optionally be further distilled and purified if additional purification is desired. Moreover, because the reactions in the process are carried out using starting materials and catalyst not containing a halogen, the dialkyl carbonate produced in the process can be manufactured to not contain halogen. For example, the dialkyl carbonate in diaryl carbonate product stream 6 can have a concentration of greater than or equal to 97 wt , or greater than or equal to 99 wt , or greater than or equal to 99.9 wt , with a halogen content of 0.5 parts per million by weight (ppm) or less, or 0.1 ppm by weight or less, or 1 part per billion by weight (ppb) or less.

[0038] Dialkyl carbonate product stream 26, 34 can be removed from the top of diaryl carbonate reactor 280, 380, respectively and can comprise essentially all (for example, greater than or equal to 99 wt%) of the unreacted aromatic alcohol starting material, some dialkyl carbonate, and some by-product alkyl aryl ether. In an embodiment, dialkyl carbonate product stream 26, 34 is recycled to the alkyl aryl production alkyl aryl carbonate reactor 240, 340 separately, or combined with first aromatic alcohol feed stream 24.

[0039] Diaryl carbonate reactor 280, 380 can be operated at a temperature greater than or equal to 90°C, specifically, greater than or equal to 100°C, and more specifically, greater than or equal to 110°C. Examples of temperature ranges include 100°C to 140°C, specifically, 120°C to 250°C, and 110°C to 240°C. The operating pressure in column 280, 380 can be greater than or equal to 10 mbar(g) (1 kPa(g)), specifically, greater than or equal to 50 mbar(g) (5 kPa(g)), and more specifically, greater than or equal to 100 mbar(g) (10 kPa(g)). Examples of pressure ranges include, 50 mbar(g) to 3 bar(g) (5 to 300 kPa(g)), 50 mbar(g) to 1 bar(g) (5 to 100 kPa(g)), and 200 mbar(g) to 900 mbar(g) (20 to 90 kPa(g)).

[0040] Both of first dialkyl carbonate product stream 2 from dialkyl carbonate reactor 210, 310 and alkanol product stream 10 from alkyl aryl carbonate reactor 240, 340 are directed to the same purification unit, in particular dialkyl carbonate purification unit 260, 360 that separates the dialkyl carbonate and alkanol to produce first purified alkanol stream 12 and purified dialkyl carbonate 16.

[0041] In an embodiment, dialkyl carbonate purification unit 260, 360 is a continuous multi-stage distillation column comprising a stripping section and an enrichment section. The continuous multi-stage distillation column can comprise trays or packings as the internal (i.e., the part in the distillation column where gas and liquid are actually brought into contact with one another) in each of the stripping section and the enrichment sections. Examples of the trays include a bubble-cap tray, a sieve tray, a ripple tray, a ballast tray, a valve tray, a counterflow tray, a Unifrax tray, a Superfrac tray, a Maxfrac tray, a dual flow tray, a grid plate tray, a turbogrid plate tray, a Kittel tray, or the like. Examples of the packings include random packings such as a Raschig ring, a Lessing ring, a Pall ring, a Berl saddle, an Intalox saddle, a Dixon packing, a McMahon packing or Heli-Pak, or structured packings such as Mellapak, Gempak, Techno-pack, Flexipac, a Sulzer packing, a Goodroll packing or Glitschgrid. A multi-stage distillation column having both a tray portion and a portion packed with packings can also be used. The internal in both the stripping section and the enrichment section of the continuous multi-stage distillation column can be a tray. Sieve trays each having a sieve portion and a downcomer portion can be used, for example, a sieve tray having 150 to 1200 holes per meter squared (holes/m²) in the sieve portion, or 200 to

1100 holes/m 2 , or 250 to 1000 holes/m 2 in the sieve portion, where the cross-sectional area per hole of each sieve tray is 0.5 to 5 centimeters squared (cm²), or 0.7 to 4 cm², or 0.9 to 3 cm².

[0042] Effective conditions for operation of the continuous multi-stage distillation column can vary depending on the form of the internals in the distillation column and the number of stages, the type, composition and amount of the feed streams 2 and alkanol product stream 10, the purity of the dialkyl carbonate to be obtained through the separation, and so on. For example, the column bottom temperature can be 150 to 250°C, or 170 to 230°C, or 180 to 220°C. The column bottom pressure varies depending on the composition in the column and the column bottom temperature used, but continuous multi-stage distillation column dialkyl carbonate purification unit 260, 360 is generally operated under an applied pressure, for example, 1 bar to 15 bar. The reflux ratio for the continuous multi-stage distillation column can be 0.5 to 5, or 0.8 to 3, or 1 to 2.5.

[0043] When feeding first dialkyl carbonate product stream 2 and alkanol product stream 10 to dialkyl carbonate purification unit 260, 360 the streams can be fed separately, or combined before entering the column. Any of the feed streams can be fed in a gaseous form, or in a liquid form. In an embodiment, the feed(s) are heated or cooled to a temperature close to the liquid temperature in the vicinity of the feeding inlet of dialkyl carbonate purification unit 260, 360 for example, within 1 to 10°C. The position at which the feed(s) are introduced to the column can be between a stripping section and an enrichment section. The alkyl aryl carbonate reactor 240, 340 can be equipped with a reboiler for heating the distillate, and a refluxing apparatus.

[0044] The concentration of the alkanol in first purified alkanol stream 12 exiting dialkyl carbonate purification unit 260, 360 can greater than or equal to 80 wt , or greater than or equal to 85 wt , or greater than or equal to 90 wt based on the total weight of first purified alkanol stream 12. The concentration of the dialkyl carbonate in stream 16 exiting dialkyl carbonate purification unit 260, 360 can be greater than or equal to 97 wt , or greater than or equal to 99 wt , or greater than or equal to 99.9 wt . The content of unreacted alkanol in stream 16 can be less than or equal to 3 wt , or less than or equal to 1 wt , or less than or equal to 0.1 wt .

[0045] FIG. 3 illustrates that purified dialkyl carbonate stream 16 of dialkyl carbonate purification unit 360 can be fed to the diaryl carbonate reactor 380. Purified dialkyl carbonate stream 16 can be a liquid or a vapor, depending upon the type of reboiler used. For example, if an external reboiler, e.g., a kettle reboiler, is used, purified dialkyl carbonate stream 16 can enter diaryl carbonate reactor 380 as a vapor. The concentration of the dialkyl carbonate in purified dialkyl carbonate stream 16 exiting dialkyl carbonate purification unit 360 can be greater than or equal to 50 wt , or greater than or equal to 60 wt , or greater than or equal to 70 wt . The content of unreacted alkanol in stream 16 exiting dialkyl carbonate purification unit 360 can be less than or equal to 50 wt , or less than or equal to 40 wt , or less than or equal to 30 wt .

[0046] Diaryl carbonate product stream 6 can be removed from the bottom of diaryl carbonate reactor 280, 380. As is described above, diaryl carbonate product stream 6 can comprise essentially all of the diaryl carbonate produced together with residual catalyst, unreacted alkyl aryl carbonate, and high-boiling by-products. The diaryl carbonate product stream 6 can optionally be further distilled and purified if additional purification is desired.

[0047] Second dialkyl carbonate product stream 34, can be removed from the top of diaryl carbonate reactor 380 and can comprise dialkyl carbonate and some by-product alkyl aryl ether, for example, anisole. Second dialkyl carbonate product stream 34 can be recycled to the alkyl aryl carbonate reactor 340 separately, or combined with first aromatic alcohol feed stream 24. First aromatic alcohol feed stream 24 can comprise an alkyl aryl ether and can be recycled to a bottom inlet of alkyl aryl carbonate reactor 340 separated from the aromatic alcohol inlet (first aromatic alcohol feed stream 24). [0048] All or a portion of aromatic alcohol product stream 28 can be directed to one or both of dialkyl carbonate purification unit 360 and alkyl aryl carbonate reactor 340. For example, 0 to 100 wt , specifically, 50 to 100 wt , more specifically, 80 to 100 wt of aromatic alcohol product stream 28 can be directed as first portion stream 30 to dialkyl carbonate purification unit 360. 0 to 100 wt , specifically, 0 to 50 wt , more specifically, 20 to 50 wt of the aromatic alcohol product stream 28 can be directed as second portion stream 32 to alkyl aryl carbonate reactor 340. It is noted that second portion stream 32 can be added directly to alkyl aryl carbonate reactor 340 or can be combined with first aromatic alcohol feed stream 24 prior to entering alkyl aryl carbonate reactor 340 and that first portion stream 30 can be added directly to dialkyl carbonate purification unit 360 or can be combined with one or more entering streams prior to entering dialkyl carbonate purification unit 360. For example, aromatic alcohol can be added as second aromatic alcohol feed stream 38. When dialkyl carbonate purification unit 360 is an extractive distillation column, the aromatic alcohol fed to the dialkyl carbonate purification unit 360 from stream 30 can act as the solvent to extract the dialkyl carbonate as it moves through the column. Stream 30 can be fed into the top of the dialkyl purification column where the aromatic alcohol can flow down the column and be collected from the bottom along with extracted dialkyl carbonate.

[0049] One or both of first aromatic alcohol feed stream 24 and second aromatic alcohol feed stream 38 can comprise a recovered aromatic alcohol that is recovered from a melt polycarbonate polymerization. The melt polymerization system can comprise a first and a second oligomerization vessel and a first and a second polymerization vessel that are all in series with each other. The recovered aromatic alcohol produced in the first oligomerization vessel can comprise greater than or equal to 99.7 wt , specifically, greater than or equal to 99.9 wt of aromatic alcohol based on the total weight of the recovered aromatic alcohol. A recovered aromatic alcohol can be produced in one or more of the second oligomerization vessel, the first polymerization vessel, and the second polymerization vessel and can be purified to produce a purified recovered aromatic alcohol comprising greater than or equal to 99.7 wt of aromatic alcohol based on the total weight of the purified aromatic alcohol prior to adding to the system.

[0050] One or both of a fresh aromatic alcohol that is not from a polycarbonate polymerization vessel and the recovered aromatic alcohol can be added in one or both of first aromatic alcohol feed stream 24 and second aromatic alcohol feed stream 38. Fresh aromatic alcohol can be added in an amount of less than or equal to 1,000 kilograms per hour (kg/hr), specifically, less than or equal to 500 kg/hr, more specifically, less than or equal to 350 kg/hr. Recovered aromatic alcohol can be added in an amount of 1 to 40 tons per hour (t/hr), specifically, 10 to 30 t/hr, more specifically, 10 to 20 t/hr.

[0051] The purification system for production of an alkyl aryl carbonate can comprise a dialkyl carbonate reactor 310, an alkyl aryl carbonate reactor 340, a dialkyl carbonate purification unit 360, and a diaryl carbonate reactor 380. The dialkyl carbonate reactor 310 can comprise an alkanol inlet, an alkylene carbonate inlet, an alkylene diol outlet, and a first alkanol/dialkyl carbonate outlet. The first alkanol/dialkyl carbonate outlet can be in fluid communication with an inlet of a dialkyl carbonate purification unit 360. The dialkyl carbonate purification unit 360 can comprise a dialkyl carbonate inlet, a first purified alkanol outlet, and a purified dialkyl carbonate outlet.

[0052] The diaryl carbonate reactor 380 can comprise a purified dialkyl carbonate inlet, an alkyl aryl ether/dialkyl carbonate outlet, an aromatic alcohol outlet, and a diaryl outlet. The purified dialkyl carbonate inlet can be in fluid communication with the purified dialkyl carbonate outlet. The alkyl aryl ether/dialkyl carbonate outlet can be in fluid communication with an inlet of an alkyl aryl carbonate reactor 340. The aromatic alcohol outlet can be in fluid communication with an inlet of the dialkyl carbonate purification unit 360 and/or with an aromatic alcohol inlet of the alkyl aryl carbonate reactor 340.

[0053] The alkyl aryl carbonate reactor 340 can comprise an aromatic alcohol inlet, an alkyl aryl ether/dialkyl carbonate inlet, a second alkanol/dialkyl carbonate outlet, and an alkyl aryl carbonate outlet. The alkyl aryl ether/dialkyl carbonate inlet can be in fluid communication with the alkyl aryl ether/dialkyl carbonate outlet of the diaryl carbonate reactor 380. The second alkanol/dialkyl carbonate outlet can be in fluid communication with an inlet of the dialkyl carbonate purification unit 360. The alkyl aryl carbonate outlet can be in fluid communication with an inlet of the diaryl carbonate reactor 380. The aromatic alcohol outlet can be in fluid communication with an inlet of the alkyl aryl carbonate reactor 340. The purified alkanol outlet can be in fluid communication with an inlet of the dialkyl carbonate reactor 310.

[0054] The above-described methods and processes can be used for the production of variety of dialkyl carbonates and diaryl carbonates from an alkylene carbonate, an alkanol, and an aromatic alcohol starting materials.

[0055] Examples of the alkylene carbonate include ethylene carbonate, propylene carbonate, l,3-dioxacyclohexa-2-one, l,3-dioxacyclohepta-2-one, and combination comprising at least one of the foregoing. Ethylene carbonate or propylene carbonate can be particularly advantageous due to ease of procurement, and ethylene carbonate is preferred.

[0056] The alkanols that can be used include all isomers of linear and branched d_i2 aliphatic alcohols and C₄_s cycloaliphatic alcohols, each of which can be unsubstituted or substituted with 1 to 3 halogen, Ci_6 alkoxy, cyano, Ci_6 alkoxycarbonyl, C(,-u

aryloxycarbonyl, Ci_6 acyloxy, or nitro groups, provided that the valence of any substituted carbon is not exceeded. Examples of alkanols include methanol, ethanol, 1-propanol, 2- propanol, allyl alcohol, 1-butanol, 2-butanol, 3-buten-l-ol, amyl alcohol, 1-hexanol, 2- hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, and 4-heptanol, cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol, 3-methylcyclopentanol, 3-ethylcyclopentanol, 3- methylcyclohexanol, 2-ethylcyclohexanol (isomers), 2,3-dimethylcyclohexanol, 1,3- diethylcyclohexanol, 3-phenylcyclohexanol, benzyl alcohol, 2-phenethyl alcohol, and 3- phenylpropanol. In a specific embodiment, the alkanol is methanol, ethanol, 1-propanol, 2- propanol, 1-butanol, 2-butanol, or 3-butanol. Ethanol or methanol can be used, but methanol is preferred.

[0057] A ratio between the amounts of the alkylene carbonate and the alkanol in varies according to the type and amount of the transesterification catalyst and the reaction conditions. To increase the alkylene carbonate conversion, the alkanol is used in an excess of at least 2 times the number of moles of the alkylene carbonate, for example, the molar ratio of the alkanol to the alkylene carbonate is 2 to 20, specifically, 3 to 15, more specifically, 5 to 12. Catalysts for the transesterification are known, and include, for example,

[0058] The transesterification can be carried out in the presence of a homogeneous or heterogeneous catalyst. Examples of the catalyst include alkali metals and alkaline earth metals such as lithium, sodium, potassium, magnesium, calcium, and barium; basic compounds of alkali metals and alkaline earth metals such as hydrides, hydroxides, alkoxides, aryloxides, and amides; basic compounds of alkali metals and alkaline earth metals such as carbonates, bicarbonates, and organic acid salts; tertiary amines such as

triethylamine, tributylamine, trihexylamine, and benzyldiethylamine; nitrogen-containing heteroaromatic compounds such as N-alkylpyrroles, N-alkylindoles, oxazoles, N- alkylimidazoles, N-alkylpyrazoles, oxadiazoles, pyridines, quinolines, isoquinolines, acridines, phenanthrolines, pyrimidines, pyrazine, and triazines; cyclic amidines such as diazobicycloundecene (DBU) and diazobicyclononene (DBN); tin compounds such as tributylmethoxytin, dibutyldiethoxytin, dibutylphenoxytin, diphenylmethoxytin, dibutyltin acetate, tributyltin chloride, and tin 2-ethylhexanoate; zinc compounds such as

dimethoxyzinc, diethoxyzinc, ethylenedioxyzinc, and dibutoxyzinc; aluminum compounds such as aluminum trimethoxide, aluminum triisopropoxide, and aluminum tributoxide;

titanium compounds such as tetramethoxytitanium, tetraethoxytitanium, tetrabutoxytitanium, dichlorodimethoxy titanium, tetraisopropoxytitanium, titanium acetate, and titanium acetylacetonate; phosphorus compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tributylmethylphosphonium halides,

trioctylbutylphosphonium halides, and triphenylmethylphosphonium halides; zirconium compounds such as zirconium halides, zirconium acetylacetonate, zirconium alkoxides, and zirconium acetate; and lead and lead-containing compounds, for example, lead oxides such as PbO, Pb(¾, and Pb₃0₄, lead sulfides such as PbS, Pb₂S₃, and PbS₂, and lead hydroxides such as Pb(OH)₂, Pb₃0₂(OH)₂, Pb₂[Pb0₂(OH)₂], and Pb₂0(OH)₂. Specifically, mentioned catalysts include titanium compounds such as titanium tetraphenoxide, titanium isopropylate, titanium tetrachloride, organotin compounds, and compounds of copper, lead, zinc, iron, and zirconium, and combinations comprising at least one of the foregoing. An amount of the catalyst used can be 0.005 to 20 wt , specifically, 0.01 to 10 wt based on the total weight of the alkylene carbonate and the alkanol.

[0059] Aromatic alcohols for transesterification of the alkyl aryl carbonate include C(,. i2 aromatic alcohols which can be unsubstituted or substituted with 1 to 3 halogen, Ci_6 alkoxy, cyano, Ci_6 alkoxycarbonyl, C -n aryloxycarbonyl, Ci_6 acyloxy, or nitro groups, provided that the valence of any substituted carbon is not exceeded. Examples include phenol o-, m- or p-cresol, o-, m- or p-chlorophenol, o-, m- or p-methoxyphenol, 2,6- dimethylphenol, 2,4-dimethylphenol, 3,4-dimethylphenol, 1-naphthol and 2-naphthol.

Phenol can be specifically, mentioned. The catalysts used in this transesterification include those described above in the process to prepare the dialkyl carbonate. Specifically, mentioned catalysts include titanium compounds such as titanium tetraphenoxide, titanium isopropylate, titanium tetrachloride, organotin compounds, and compounds of copper, lead, zinc, iron, and zirconium, and combinations comprising at least one of the foregoing.

[0060] In an embodiment, the alkylene carbonate is ethylene carbonate or propylene carbonate, the alkanol is methanol or ethanol, and the aromatic alcohol is phenol. The alkyl aryl ether can be methoxybenzene. [0061] The diaryl carbonate produced can be used to manufacture a polycarbonate. In an embodiment, a dihydroxy compound can be used as a reactant with a diaryl carbonate such as diphenol carbonate as a carbonate source.

[0062] Generally, in the melt polymerization process, polycarbonates can be prepared by co-reacting, in a molten state, a dihydroxy reactant and a diaryl carbonate in the presence of a transesterification catalyst. The reaction can be carried out in typical polymerization equipment, such as a continuously stirred reactor (CSTR), plug flow reactor, wire wetting fall polymerizers, free fall polymerizers, wiped film polymerizers, BANBURY mixers, single or twin screw extruders, or a combination of the foregoing. Volatile monohydric phenol is removed from the molten reactants by distillation and the polymer is isolated as a molten residue. Melt polymerization can be conducted as a batch process or as a continuous process. In either case, the melt polymerization conditions used can comprise two or more distinct reaction stages, for example, a first reaction stage in which the starting dihydroxy aromatic compound and diaryl carbonate are converted into an oligomeric polycarbonate and a second reaction stage wherein the oligomeric polycarbonate formed in the first reaction stage is converted to high molecular weight polycarbonate. Such "staged" polymerization reaction conditions are especially suitable for use in continuous polymerization systems wherein the starting monomers are oligomerized in a first reaction vessel and the oligomeric

polycarbonate formed therein is continuously transferred to one or more downstream reactors in which the oligomeric polycarbonate is converted to high molecular weight polycarbonate. Typically, in the oligomerization stage the oligomeric polycarbonate produced has a number average molecular weight of 1,000 to 7,500 Daltons. In one or more subsequent

polymerization stages, the number average molecular weight (Mn) of the polycarbonate is increased to between 8,000 and 25,000 Daltons (using polycarbonate standard). Typically, solvents are not used in the process, and the reactants dihydroxy aromatic compound and the diaryl carbonate are in a molten state. The reaction temperature can be 100°C to 350°C, specifically, 180°C to 310°C. The pressure can be at atmospheric pressure, supra- atmospheric pressure, or a range of pressures from atmospheric pressure to 15 torr in the initial stages of the reaction, and at a reduced pressure at later stages, for example, 0.2 to 15 torr. The reaction time is generally 0.1 hours to 10 hours.

[0063] A transesterification catalyst(s) can be employed in the polycarbonate polymerization. The transeseterification catalyst can comprise an alkali catalyst and a quaternary catalyst. The quaternary catalyst comprises one or both of a quaternary ammonium compound and a quaternary phosphonium compound. The alkali catalyst comprises a source of one or both of an alkali ion and an alkaline earth metal ion.

[0064] Set forth below are some embodiments of the methods for making the alkyl aryl carbonate, the diaryl carbonate, the polycarbonate, as well as apparatuses for use in the methods.

[0065] Embodiment 1 : A method for producing an alkyl aryl carbonate, comprising: reacting an alkylene carbonate and an alkanol in the presence of a first transesterification catalyst in a dialkyl carbonate reactor to produce a first dialkyl carbonate product stream comprising a dialkyl carbonate and unreacted alkanol, and an alkylene glycol product stream comprising an alkylene glycol and unreacted alkanol; purifying the first dialkyl carbonate product stream in a dialkyl carbonate purification unit to provide a purified dialkyl carbonate stream and a first purified alkanol stream; reacting the purified dialkyl carbonate stream in the presence of a second transesterification catalyst in a diaryl carbonate reactor to produce a diaryl carbonate product stream comprising a diaryl carbonate product by disproportionation, and (i) an aromatic alcohol product stream comprising an aromatic alcohol product, a second dialkyl carbonate product stream comprising the dialkyl carbonate and an alkyl aryl ether, or (ii) a second dialkyl carbonate product stream comprising the dialkyl carbonate, an aromatic alcohol product, and an alkyl aryl ether, and separating the aromatic alcohol product from the second dialkyl carbonate product stream to produce an aromatic alcohol product stream comprising the aromatic alcohol product; directing an amount (X wt%) as a first portion stream of aromatic alcohol product stream to the dialkyl carbonate purification unit and directing an amount (100 wt%-X wt%) as a second portion stream of the aromatic alcohol product stream to an alkyl aryl carbonate reactor, wherein X wt% is greater than 0; reacting the second dialkyl carbonate product stream, the second portion stream, and a first aromatic alcohol feed stream in the presence of the second transesterification catalyst in an alkyl aryl carbonate reactor to produce an alkanol product stream comprising an alkanol product and unreacted dialkyl carbonate, and an alkyl aryl carbonate product stream comprising an alkyl aryl carbonate product and unreacted aromatic alcohol; and purifying the alkanol product stream and the first portion stream in the dialkyl carbonate purification unit to provide the purified dialkyl carbonate stream and the first purified alkanol stream; wherein purifying comprises extracting the dialkyl carbonate with the aromatic alcohol.

[0066] Embodiment 2: The method of Embodiment 1, further comprising directing at least a portion of the first purified alkanol stream to the alkyl aryl carbonate reactor, the dialkyl carbonate reactor, or both the alkyl aryl carbonate reactor and the dialkyl carbonate reactor.

[0067] Embodiment 3: The method of any one of the preceding embodiments, further comprising purifying the alkylene glycol product stream in an alkylene glycol purification unit to provide a purified alkylene glycol stream and a second purified alkanol stream.

[0068] Embodiment 4: The method of Embodiment 3, further comprising recycling the second purified alkanol stream to the dialkyl carbonate reactor.

[0069] Embodiment 5: The method of any one of the preceding embodiments, further comprising removing the aromatic alcohol product stream from a middle stage of the diaryl carbonate reactor.

[0070] Embodiment 6: The method of any one of the preceding embodiments, wherein the dialkyl carbonate purification unit is a extractive distillation column, optionally wherein the extractive distillation column is maintained at a temperature of 63 °C to 250°C and a pressure at the top of the column of 100 to 300 kPa(g).

[0071] Embodiment 7: The method of any one of the preceding embodiments, wherein the dialkyl carbonate reactor, the alkyl aryl carbonate reactor, the diaryl carbonate reactor, or a combination comprising at least one of the foregoing is a reactive distillation column; or wherein the dialkyl carbonate reactor, the alkyl aryl carbonate reactor, and the diaryl carbonate reactor are reactive distillation columns.

[0072] Embodiment 8: The method of any one of the preceding embodiments, wherein the dialkyl carbonate reactor comprises a first reactive distillation column maintained at a temperature of 65°C to 150°C, and a pressure at the top of the first reactive distillation column of 50 to 300 kPa(g), and the alkyl aryl carbonate reactor comprises a second reactive distillation column maintained at a temperature of 120°C to 270°C, and a pressure at the top of the second reactive distillation column of 200 to 700 kPa(g).

[0073] Embodiment 9: A method for producing an alkyl aryl carbonate, the method comprising: reacting an alkylene carbonate and an alkanol in the presence of a first transesterification catalyst in a dialkyl carbonate reactive distillation column to produce a dialkyl carbonate and unreacted alkanol; recovering from the dialkyl carbonate reactor a first dialkyl carbonate product stream comprising the dialkyl carbonate and the unreacted alkanol and an alkylene glycol product stream comprising an alkylene glycol and the alkanol, wherein the dialkyl carbonate reactor comprises a reactive distillation column; purifying the first dialkyl carbonate product stream in a dialkyl purification unit to provide a purified dialkyl carbonate stream and first purified alkanol stream; reacting the purified dialkyl carbonate stream in the presence of a second transesterification catalyst in a diaryl carbonate reactor to produce an alkyl aryl carbonate, an aromatic alcohol, an alkyl aryl ether, and an unreacted dialkyl carbonate, wherein the diaryl carbonate reactor comprises a diaryl carbonate reactive distillation column; recovering from the diaryl carbonate reactor a second dialkyl carbonate product stream comprising the unreacted dialkyl carbonate and the alkyl aryl ether, a diaryl carbonate product stream comprising a diaryl carbonate, and an aromatic alcohol product stream comprising the aromatic alcohol; directing 0 to 100 wt% of aromatic alcohol product stream as first portion stream to the dialkyl carbonate purification unit and directing 0 to 100 wt% of the aromatic alcohol product stream as second portion stream to an alkyl aryl carbonate reactor; reacting the second dialkyl carbonate product stream, the second portion stream, and a first aromatic alcohol feed stream in the presence of the second transesterification catalyst in an alkyl aryl carbonate reactor to produce an alkyl aryl carbonate, an alkanol, and unreacted dialkyl carbonate, wherein the alkyl aryl carbonate reactor comprises a reactive distillation column; recovering from the alkyl aryl carbonate reactor an alkanol product stream comprising the alkanol and the unreacted dialkyl carbonate, and an alkyl aryl carbonate product stream comprising the alkyl aryl carbonate; and purifying the alkanol product stream in the dialkyl carbonate purification unit to provide the purified dialkyl carbonate stream and the first purified alkanol stream.

[0074] Embodiment 10: The method of Embodiment 11, further comprising at least one of recycling the first purified alkanol stream to the alkyl aryl carbonate reactor; recycling the first purified alkanol stream to the dialkyl carbonate reactor; purifying the purified alkylene glycol stream in an alkylene glycol purification unit to provide a purified alkane diol stream and a second purified alkanol stream and recycling the second purified alkanol stream to the alkylene glycol purification unit; and recycling the second portion stream to the bottom of the alkyl aryl carbonate reactor.

[0075] Embodiment 11 : The method of any one of the preceding embodiments, further comprising reacting the alkyl aryl carbonate product stream in the diaryl carbonate reactor.

[0076] Embodiment 12: The method of any one of the preceding embodiments, further comprising polymerizing an aromatic dihydroxy compound and the diaryl carbonate in the presence of a catalyst to produce a polycarbonate. [0077] Embodiment 13: The method of any one of the preceding embodiments, wherein the alkylene carbonate comprises ethylene carbonate, propylene carbonate, or a combination comprising one or both of the foregoing, the alkanol comprises methanol, ethanol or a combination comprising one or both of the foregoing, the dialkyl carbonate comprises dimethyl carbonate, diethyl carbonate or a combination comprising one or both of the foregoing, the aromatic alcohol comprises phenol, and the alkyl aryl carbonate comprises methyl phenyl carbonate, ethyl phenyl carbonate, or a combination comprising one or both of the foregoing.

[0078] Embodiment 14: The method of any one of the preceding embodiments, wherein the method further comprises adding a recovered aromatic alcohol in one or both of the first aromatic alcohol feed stream and a second aromatic alcohol feed stream, wherein the recovered aromatic alcohol is recovered from a melt polycarbonate polymerization and comprises greater than or equal to 99.7 wt% of an aromatic alcohol based on the total weight of the recovered aromatic alcohol, wherein if the recovered aromatic alcohol was recovered from one or more of a second oligomerization vessel, a first polymerization vessel, and a second polymerization vessel then the method further comprises purifying the recovered aromatic alcohol prior to the adding.

[0079] Embodiment 15: The method of any one of the preceding embodiments, wherein the diaryl carbonate product comprises a metal compound, wherein the metal compound comprises less than or equal to 500 ppb of molybdenum; less than or equal to 33 ppb of vanadium; less than or equal to 33 ppb of chromium; less than or equal to 75 ppb of titanium; less than or equal to 375 ppb of niobium; less than or equal to 33 ppb of nickel; less than or equal to 10 ppb of zirconium; and less or equal to 10 ppb iron; all based on the total weight of the diaryl carbonate product and the metal compound.

[0080] Embodiment 16: The method of any of the preceding embodiments, wherein X is greater than or equal to 20 wt , specifically, greater than or equal to 50 wt , more specifically, greater than or equal to 90 wt%.

[0081] Embodiment 17: A system for production of an alkyl aryl carbonate comprising: a dialkyl carbonate reactor, an alkyl aryl carbonate reactor, a dialkyl carbonate purification unit, and a diaryl carbonate reactor. The dialkyl carbonate reactor comprises an alkanol inlet, an alkylene carbonate inlet, an alkylene diol outlet, and a first alkanol/dialkyl carbonate outlet in fluid communication with a dialkyl carbonate inlet of a dialkyl carbonate purification unit. The dialkyl carbonate purification unit comprises the dialkyl carbonate inlet, a first purified alkanol outlet, a purified dialkyl carbonate outlet; and an unit aromatic alcohol inlet. The diaryl carbonate reactor comprises a purified dialkyl carbonate inlet in fluid communication with the purified dialkyl carbonate outlet, an alkyl aryl ether/dialkyl carbonate outlet in fluid communication with an alkyl aryl ether/dialkyl carbonate inlet of the alkyl aryl carbonate reactor, an aromatic alcohol outlet in fluid communication with the unit aromatic alcohol inlet of the dialkyl carbonate purification unit and optionally with a reactor aromatic alcohol inlet of the alkyl aryl carbonate reactor, and a diaryl outlet. The alkyl aryl carbonate reactor comprising the reactor aromatic alcohol inlet, the alkyl aryl ether/dialkyl carbonate inlet in fluid communication with the alkyl aryl ether/dialkyl carbonate outlet of the diaryl carbonate reactor, a second alkanol/dialkyl carbonate outlet in fluid communication with an alkanol/dialkyl carbonate inlet of the dialkyl carbonate purification unit, and an alkyl aryl carbonate outlet.

[0082] Embodiment 18: The system of any one of Embodiment 17, wherein the aromatic alcohol outlet is in fluid communication with the reactor aromatic alcohol inlet.

[0083] Embodiment 19: A system for production of an alkyl aryl carbonate comprising: a dialkyl carbonate reactor, an alkyl aryl carbonate reactor, a dialkyl carbonate purification unit, a diaryl carbonate reactor; and an aromatic alcohol separation unit. The dialkyl carbonate reactor comprises an alkanol inlet, an alkylene carbonate inlet, an alkylene diol outlet, and a first alkanol/dialkyl carbonate outlet in fluid communication with a dialkyl carbonate inlet of a dialkyl carbonate purification unit. The dialkyl carbonate purification unit comprises the dialkyl carbonate inlet, a first purified alkanol outlet, a purified dialkyl carbonate outlet; and an unit aromatic alcohol inlet. The diaryl carbonate reactor comprises a purified dialkyl carbonate inlet in fluid communication with the purified dialkyl carbonate outlet, the alkyl aryl ether/dialkyl carbonate outlet in fluid communication with a separation inlet of the aromatic alcohol separation unit, the aromatic alcohol separation unit having an aromatic outlet in fluid communication with the unit aromatic alcohol inlet and an a separated alkyl aryl ether/dialkyl carbonate outlet in fluid communication with the reactor aromatic alcohol inlet, and a diaryl outlet. The alkyl aryl carbonate reactor comprising the reactor aromatic alcohol inlet, a second alkanol/dialkyl carbonate outlet in fluid communication with an alkanol/dialkyl carbonate inlet of the dialkyl carbonate purification unit, and an alkyl aryl carbonate outlet. [0084] Embodiment 20: The apparatus of any one of Embodiments 17-19, wherein the alkyl aryl carbonate outlet is in fluid communication with an alkyl aryl carbonate inlet of the diaryl carbonate reactor.

[0085] Embodiment 21 : The system of any one of Embodiments 17-20, wherein the purified alkanol outlet is in fluid communication with the alkanol inlet of the dialkyl carbonate reactor.

[0086] In general, embodiments can alternatively comprise (e.g., include), consist of, or consist essentially of, any appropriate components herein disclosed. The embodiments can additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objectives of the embodiments.

[0087] As used herein, a trace amount is an amount of less than 0.01 wt% based upon a total weight of the product. All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of "up to 25 wt , or, more specifically, 5 wt% to 20 wt ", is inclusive of the endpoints and all intermediate values of the ranges of "5 wt% to 25 wt ," etc.). "Combination" is inclusive of blends, mixtures, alloys, reaction products, and the like. Furthermore, the terms "first," "second," and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms "a" and "an" and "the" herein do not denote a limitation of quantity, and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. "Or" means "and/or" unless clearly indicated otherwise. The suffix "(s)" as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the film(s) includes one or more films). Reference throughout the specification to "one embodiment", "another embodiment", "an embodiment", and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

[0088] While particular embodiments have been described, alternatives,

modifications, variations, improvements, and substantial equivalents that are or can be presently unforeseen can arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modification variations, improvements, and substantial equivalents.

[0089] What is claimed is:

Claims

1. A method for producing an alkyl aryl carbonate, comprising:

reacting an alkylene carbonate and an alkanol in the presence of a first

transesterification catalyst in a dialkyl carbonate reactor to produce a first dialkyl carbonate product stream comprising a dialkyl carbonate and unreacted alkanol, and an alkylene glycol product stream comprising an alkylene glycol and unreacted alkanol;

purifying the first dialkyl carbonate product stream in a dialkyl carbonate purification unit to provide a purified dialkyl carbonate stream and a first purified alkanol stream;

reacting the purified dialkyl carbonate stream in the presence of a second

transesterification catalyst in a diaryl carbonate reactor to produce a diaryl carbonate product stream comprising a diaryl carbonate product by disproportionation, and (i) an aromatic alcohol product stream comprising an aromatic alcohol product, a second dialkyl carbonate product stream comprising the dialkyl carbonate and an alkyl aryl ether, or (ii) a second dialkyl carbonate product stream comprising the dialkyl carbonate, an aromatic alcohol product, and an alkyl aryl ether, and separating the aromatic alcohol product from the second dialkyl carbonate product stream to produce an aromatic alcohol product stream comprising the aromatic alcohol product;

directing an amount (X wt%) as a first portion stream of aromatic alcohol product stream to the dialkyl carbonate purification unit and directing an amount (100 wt%-X wt%) as a second portion stream of the aromatic alcohol product stream to an alkyl aryl carbonate reactor, wherein X wt% is greater than 0;

reacting the second dialkyl carbonate product stream, the second portion stream, and a first aromatic alcohol feed stream in the presence of the second transesterification catalyst in an alkyl aryl carbonate reactor to produce an alkanol product stream comprising an alkanol product and unreacted dialkyl carbonate, and an alkyl aryl carbonate product stream comprising an alkyl aryl carbonate product and unreacted aromatic alcohol; and

purifying the alkanol product stream and the first portion stream in the dialkyl carbonate purification unit to provide the purified dialkyl carbonate stream and the first purified alkanol stream; wherein purifying comprises extracting the dialkyl carbonate with the aromatic alcohol.

2. The method of Claim 1 , further comprising directing at least a portion of the first purified alkanol stream to the alkyl aryl carbonate reactor, the dialkyl carbonate reactor, or both the alkyl aryl carbonate reactor and the dialkyl carbonate reactor.

3. The method of any one of the preceding claims, further comprising purifying the alkylene glycol product stream in an alkylene glycol purification unit to provide a purified alkylene glycol stream and a second purified alkanol stream.

4. The method of Claim 3, further comprising recycling the second purified alkanol stream to the dialkyl carbonate reactor.

5. The method of any one of the preceding claims, comprising removing the aromatic alcohol product stream from a middle stage of the diaryl carbonate reactor.

6. The method of any one of the preceding claims, wherein the dialkyl carbonate purification unit is a extractive distillation column.

7. The method of any one of the preceding claims, wherein the dialkyl carbonate reactor, the alkyl aryl carbonate reactor, the diaryl carbonate reactor, or a combination comprising at least one of the foregoing is a reactive distillation column; or wherein the dialkyl carbonate reactor, the alkyl aryl carbonate reactor, and the diaryl carbonate reactor are reactive distillation columns.

8. The method of any one of the preceding claims, wherein

the dialkyl carbonate reactor comprises a first reactive distillation column maintained at a temperature of 65 °C to 150°C, and a pressure at the top of the first reactive distillation column of 50 to 300 kPa(g), and the alkyl aryl carbonate reactor comprises a second reactive distillation column maintained at a temperature of 120°C to 270°C, and a pressure at the top of the second reactive distillation column of 200 to 700 kPa(g).

9. A method for producing an alkyl aryl carbonate, the method comprising: reacting an alkylene carbonate and an alkanol in the presence of a first

transesterification catalyst in a dialkyl carbonate reactive distillation column to produce a dialkyl carbonate and unreacted alkanol;

recovering from the dialkyl carbonate reactor a first dialkyl carbonate product stream comprising the dialkyl carbonate and the unreacted alkanol and an alkylene glycol product stream comprising an alkylene glycol and the alkanol, wherein the dialkyl carbonate reactor comprises a reactive distillation column;

purifying the first dialkyl carbonate product stream in a dialkyl purification unit to provide a purified dialkyl carbonate stream and first purified alkanol stream;

reacting the purified dialkyl carbonate stream in the presence of a second

transesterification catalyst in a diaryl carbonate reactor to produce an alkyl aryl carbonate, an aromatic alcohol, an alkyl aryl ether, and an unreacted dialkyl carbonate, wherein the diaryl carbonate reactor comprises a diaryl carbonate reactive distillation column;

recovering from the diaryl carbonate reactor a second dialkyl carbonate product stream comprising the unreacted dialkyl carbonate and the alkyl aryl ether, a diaryl carbonate product stream comprising a diaryl carbonate, and an aromatic alcohol product stream comprising the aromatic alcohol;

directing 0 to 100 wt% of aromatic alcohol product stream as first portion stream to the dialkyl carbonate purification unit and directing 0 to 100 wt% of the aromatic alcohol product stream as second portion stream to an alkyl aryl carbonate reactor;

reacting the second dialkyl carbonate product stream, the second portion stream, and a first aromatic alcohol feed stream in the presence of the second transesterification catalyst in an alkyl aryl carbonate reactor to produce an alkyl aryl carbonate, an alkanol, and unreacted dialkyl carbonate, wherein the alkyl aryl carbonate reactor comprises a reactive distillation column;

recovering from the alkyl aryl carbonate reactor an alkanol product stream comprising the alkanol and the unreacted dialkyl carbonate, and an alkyl aryl carbonate product stream comprising the alkyl aryl carbonate; and

purifying the alkanol product stream in the dialkyl carbonate purification unit to provide the purified dialkyl carbonate stream and the first purified alkanol stream.

10. The method of Claim 11, further comprising at least one of

recycling the first purified alkanol stream to the alkyl aryl carbonate reactor;

recycling the first purified alkanol stream to the dialkyl carbonate reactor;

purifying the purified alkylene glycol stream in an alkylene glycol purification unit to provide a purified alkane diol stream and a second purified alkanol stream and recycling the second purified alkanol stream to the alkylene glycol purification unit; and

recycling the second portion stream to the bottom of the alkyl aryl carbonate reactor.

11. The method of any one of the preceding claims, further comprising reacting the alkyl aryl carbonate product stream in the diaryl carbonate reactor.

12. The method of any of the preceding claims, further comprising polymerizing an aromatic dihydroxy compound and the diaryl carbonate in the presence of a catalyst to produce a polycarbonate.

13. The method of any one of the preceding claims, wherein the alkylene carbonate comprises ethylene carbonate, propylene carbonate, or a combination comprising one or both of the foregoing, the alkanol comprises methanol, ethanol or a combination comprising one or both of the foregoing, the dialkyl carbonate comprises dimethyl carbonate, diethyl carbonate or a combination comprising one or both of the foregoing, the aromatic alcohol comprises phenol, and the alkyl aryl carbonate comprises methyl phenyl carbonate, ethyl phenyl carbonate, or a combination comprising one or both of the foregoing.

14. The method any one of the preceding claims, wherein the method further comprises adding a recovered aromatic alcohol in one or both of the first aromatic alcohol feed stream and a second aromatic alcohol feed stream, wherein the recovered aromatic alcohol is recovered from a melt polycarbonate polymerization and comprises greater than or equal to 99.7 wt% of an aromatic alcohol based on the total weight of the recovered aromatic alcohol, wherein if the recovered aromatic alcohol was recovered from one or more of a second oligomerization vessel, a first polymerization vessel, and a second polymerization vessel then the method further comprises purifying the recovered aromatic alcohol prior to the adding.

15. The method of any of the preceding claims, wherein the diaryl carbonate product comprises a metal compound, wherein the metal compound comprises less than or equal to 500 ppb of molybdenum; less than or equal to 33 ppb of vanadium; less than or equal to 33 ppb of chromium; less than or equal to 75 ppb of titanium; less than or equal to 375 ppb of niobium; less than or equal to 33 ppb of nickel; less than or equal to 10 ppb of zirconium; and less or equal to 10 ppb iron; all based on the total weight of the diaryl carbonate product and the metal compound.

16. A system for production of an alkyl aryl carbonate comprising: a dialkyl carbonate reactor, an alkyl aryl carbonate reactor, a dialkyl carbonate purification unit, and a diaryl carbonate reactor;

wherein the dialkyl carbonate reactor comprises an alkanol inlet, an alkylene carbonate inlet, an alkylene diol outlet, and a first alkanol/dialkyl carbonate outlet in fluid communication with a dialkyl carbonate inlet of a dialkyl carbonate purification unit,

wherein the dialkyl carbonate purification unit comprises the dialkyl carbonate inlet, a first purified alkanol outlet, a purified dialkyl carbonate outlet; and an unit aromatic alcohol inlet;

wherein the diaryl carbonate reactor comprises a purified dialkyl carbonate inlet in fluid communication with the purified dialkyl carbonate outlet, an alkyl aryl ether/dialkyl carbonate outlet in fluid communication with an alkyl aryl ether/dialkyl carbonate inlet of the alkyl aryl carbonate reactor, an aromatic alcohol outlet in fluid communication with the unit aromatic alcohol inlet of the dialkyl carbonate purification unit and optionally with a reactor aromatic alcohol inlet of the alkyl aryl carbonate reactor, and a diaryl outlet; and

wherein the alkyl aryl carbonate reactor comprises the reactor aromatic alcohol inlet, the alkyl aryl ether/dialkyl carbonate inlet in fluid communication with the alkyl aryl ether/dialkyl carbonate outlet of the diaryl carbonate reactor, a second alkanol/dialkyl carbonate outlet in fluid communication with an alkanol/dialkyl carbonate inlet of the dialkyl carbonate purification unit, and an alkyl aryl carbonate outlet.

17. The system of any one of Claim 16, wherein the aromatic alcohol outlet is in fluid communication with the reactor aromatic alcohol inlet.

18. A system for production of an alkyl aryl carbonate comprising: a dialkyl carbonate reactor, an alkyl aryl carbonate reactor, a dialkyl carbonate purification unit, a diaryl carbonate reactor, and an aromatic alcohol separation unit;

wherein the diaryl carbonate reactor comprises a purified dialkyl carbonate inlet in fluid communication with the purified dialkyl carbonate outlet, the alkyl aryl ether/dialkyl carbonate outlet in fluid communication with a separation inlet of the aromatic alcohol separation unit, the aromatic alcohol separation unit having an aromatic outlet in fluid communication with the unit aromatic alcohol inlet and an a separated alkyl aryl ether/dialkyl carbonate outlet in fluid communication with the reactor aromatic alcohol inlet, and a diaryl outlet; and

wherein the alkyl aryl carbonate reactor comprising the reactor aromatic alcohol inlet, a second alkanol/dialkyl carbonate outlet in fluid communication with an alkanol/dialkyl carbonate inlet of the dialkyl carbonate purification unit, and an alkyl aryl carbonate outlet.

19. The apparatus of any one of Claims 16-18, wherein the alkyl aryl carbonate outlet is in fluid communication with an alkyl aryl inlet of the diaryl carbonate reactor.

20. The system of any one of Claims 16-19, wherein the purified alkanol outlet is in fluid communication with the alkanol inlet of the dialkyl carbonate reactor.