TWI250977B - Method for preparing a dialkyl carbonate, and its use in the preparation of diaryl carbonates and polycarbonates - Google Patents

Abstract

Unexpected corrosion of downstream sections of a dialkyl carbonate manufacturing apparatus has been traced to alkyl chloroformate impurities, which slowly decompose to yield hydrochloric acid. An improved process and apparatus for dialkyl carbonate synthesis reduce corrosion by physically removing or chemically decomposing the alkyl chloroformate impurities within the corrosion-resistant upstream sections of the apparatus.

Description

1250977 A7 _ B7___ V. INSTRUCTIONS (1) Background Polycarbonate is a valuable material with great physical and optical properties. The method of preparing the polycarbonate resin includes an interfacial method and a melting method. In the interfacial method described in, for example, U.S. Patent No. 4,360,096, the disclosure of which is incorporated herein by reference. The bisphenol is reacted with a diaryl carbonate in the melting process described in U.S. Patent No. 3,1,5,008, the entire disclosure of which is incorporated herein. Melt processes are currently preferred because of the need to avoid the use of phosgene and the use of melt processes for the synthesis of polycarbonates which require an efficient process for the industrial manufacture of diaryl carbonates. There are several known methods for making diaryl carbonate. An example of such a method is described in U.S. Patent No. 4,1,82,726 to I. In this method, the diaryl carbonate is obtained by reacting a diester carbonate with an aryl hydroxide (refer to the following flow chart. I----------- Note on the back side of this page), 11 + 2ΑγΟ· rct + 2R0·

0R (I) aw, 〇Ar t· Ministry of Economic Affairs Zhici Property Bureau employee consumption cooperative printed US Patent No. 4,182 also proved that diaryl carbonate can react with dihydric phenol to produce polycarbonate (refer to the following Flow chart π). Np + nHO-Ar'-OH ArO ΌΑγ -Ar-0&quot; 2nArOH (Π) This paper scales the Chinese national standard WCNS) Α4ϋ7^χ29_ϋ -4- Ministry of Economic Affairs Intellectual Property Bureau staff levy cooperative printing 1250977 A7 B7____ five </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; 4,3 1 8,862. 0Cue] Catalyst II ROH + CO + 1/202-^ U + H2 〇 (III) R〇' 'OR US Patent No. 5,527,943 (Γ 943) also describes the flow chart (ΠΙ) of the dialkyl carbonate method known Disadvantages: It produces by-product water. Moreover, it is possible to continuously add hydrochloric acid (HC1) to the reaction mixture to maintain the desired chlorine to copper molar ratio. Therefore, HC1, CuCl catalyst and water are generally found in the stream leaving the reactor. Hydrochloric acid and copper chloride are extremely humus-free in the presence of water, so in the reaction zone of the chemical equipment for the manufacture of dialkyl carbonate by such a method, a corrosion-resistant material such as a container lined with glass is used. . Because corrosion resistant equipment is expensive, it is desirable to use it as little as possible in less equipment. A typical apparatus for preparing a dialkyl carbonate according to Scheme III may contain three stages: a reaction section for converting a feedstock to dialkyl carbonate for separating the dialkyl carbonate from unreacted monomers and by-products. a separation section of the ester, and a purification section for removing water and further separating the dialkyl carbonate. The 343 patent teaches to minimize the amount of corrosion resistant equipment required to remove HC1 from the process stream immediately after the reaction zone. This situation eliminates the need to use expensive corrosion resistant materials in the separation and purification sections of the apparatus. The 34 3 patent further suggests that the step of removing HC1 and possibly the copper halide salt from the stream immediately after the reaction zone can be applied to the Chinese National Standard (CNS) A4 by the gas-liquid mixture obtained by the reaction. Specifications (210X 297 metric tons) (Please read the notes on the back and fill out this page)

-5- 1250977 A7 B7 Ministry of Economic Affairs Zhici Property Bureau employee consumption cooperative printing 5, invention description (3) is achieved by a liquid flow composed of a program fluid. The '943 patent also states that the operating conditions employed are preferably adjusted such that the gas mixture from the reactor does not condense prior to the acid removal zone, or only condenses to a negligible extent to avoid removal of HC1. The necessity to reheat the mixture before (column 3, lines 17 to 30). In light of the foregoing, it is desirable to construct an apparatus in which HC1 and any copper halide salts can be removed after the reaction zone to avoid corrosion in the separation and purification sections. However, the same technique as described in the '343 patent... the removal of HC1 and copper salts by evaporation of the feed in a countercurrent azeotropic fluid treatment column from the reaction mixture does not prevent corrosion in the downstream separation and purification sections. . There is therefore a need for a dialkyl carbonate process that confirms and eliminates the source of additional uranium. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other prior art deficiencies and disadvantages are alleviated by a process for preparing a dialkyl carbonate comprising reacting an alkanol, oxygen, carbon monoxide, and a catalyst to form a dialkyl carbonate. a mixture of alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide; and removing alkyl chloroformate from the mixture. After considerable efforts, the inventors have discovered that the synthesis of dialkyl carbonate forms a by-product of alkyl chloroformate, causing problematic corrosion. For example, in the reaction of methanol, carbon monoxide and oxygen to form dimethyl carbonate (hereinafter referred to as "DMC"), methyl chloroformate (hereinafter referred to as "MCF") by-product may be formed. The MCF can pass through the HC1 removal column and enter the separator and purification section (please read the notes on the back and fill out this page)

This paper. The scale applies to China National Standard (CNS) Λ4 specification (210X 297 mm) -6 - 1250977 A 7 B7 Ministry of Economic Affairs Intellectual Property Bureau employee consumption cooperative printing 5, invention description (4), here with methanol And/or water slowly reacts to form corrosive H C1. Therefore, it was determined that after the separation and purification sections, several steps of removing the MCF were required. Other specific examples are described below, including apparatus for preparing dialkyl carbonate. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a first specific example of the apparatus. Figure 2 is a simplified illustration of a corrosion-resistant control device. Figure 3 is a simplified illustration of one embodiment of the device in which the fluid channel 110 includes two storage containers 120. Figure 4 is a simplified illustration of one embodiment of the apparatus wherein the fluid passage 11 includes two storage containers 120. Figure 5 is a simplified illustration of one embodiment of the device in which the fluid passage 110 includes a tubular section 130. Figure 6 is a simplified illustration of one embodiment of the apparatus including an ion exchange resin bed 190. Figure 7 is a simplified illustration of one embodiment of the apparatus wherein the fluid passage 110 comprises a first gas-liquid separator 90 and a second gas-liquid separator 100. Figure 8 is the apparatus. A simplified illustration of a specific example in which fluid channel 110 is before the first gas-liquid separator 90. Figure 9 is a simplified illustration of one embodiment of the apparatus in which the fluid channel Π0 is after the azeotrope column 180. (Please read the precautions on the back and fill out this page.) Clothing. The standard paper size applies to the Chinese National Standard (CNS) Λ4 specification (210X297 public f) -7- 1250977 B7 V. Invention description (5) Figure 10 is a total The chlorine concentration of the bottom material of the boiling column 180 is a plot of the device type (Figs. 2 and 3) and time. Figure 11 is a graph showing the concentration of methyl chloroformate entering and leaving the fluid channel 110 as a function of time as corresponding to the apparatus of Figure 3. Main component control device 20 Reaction zone 3〇 Separation section 40 Purification section 50 Reactor 6 Catalytic tank 7 Hydrochloric acid tank 80 Condenser 90 First gas-liquid separator 100 Second gas-liquid separator]1 〇Fluid channel 12〇Storage container 130 Tubular section 14〇First heat exchanger 150 Second heat exchanger!60 Acid removal tower 17〇Line azeotrope This paper scale applies to China National Standard (CNS) A4 specification (2丨0X29*7 mm) ------------- (Please read the notes on the back and fill out this page again)

Ministry of Economic Affairs Zhizhi Property Bureau Staff Consumption Cooperative India Yin-8 - Ministry of Economic Affairs Zhici Property Bureau 8 Workers Consumption Cooperative Printed 1250977 A7 _________ B7 V. Invention Description (6) 19 〇 Ion exchange resin bed better specific examples A specific example is a method comprising: reacting an alkanol, oxygen, carbon monoxide with a catalyst to form a mixture comprising dialkyl carbonate, alkyl chloroformate, hydrochloric acid 'water, carbon dioxide, and carbon monoxide; The mixture removes the alkyl chloroformate. The alkanol used in the method is not particularly limited. Suitable alkanols include ~, 2, and 3 (:! to alkanols, preferably 1st to c6 alkanols. More preferred alkanols include methanol. Oxygen can be supplied in any form, in gaseous form Preferably, suitable sources of oxygen include, for example, air and oxygen-containing gases, containing at least about 95 weight percent molecular oxygen, preferably at least about 99 weight percent molecular oxygen. Suitable oxygen containing systems are, for example, sold by Air Products. The carbon monoxide is preferably provided in the form of a gas containing at least about 90 weight percent of one carbon oxide, preferably at least about 95 weight percent, more preferably at least about 99 weight percent. Suitable carbon monoxide gas containing systems are, for example, Ah·Product®. The catalyst system includes iron, copper, nickel, cobalt, zinc, antimony, bismuth, palladium, silver, cadmium, antimony, stagnation, antimony, platinum, gold, mercury, and the like and the foregoing metals. a catalyst for at least one of the compositions. Preferably, the catalyst may comprise copper. More preferably, the catalyst comprises copper and chloride ions, and the molar ratio is about 0.5 to about 1.5. Within this range, at least about 0.8 moles. Better. This Within the enclosure, the molar ratio of up to about 1.2 is also preferred. The preferred catalysts include cuprous chloride (C.uCl). The paper size applies to the Chinese National Standard (CN'S) Α4ϋ (2丨0xY97 mm) &quot; (Please read the notes on the back and then fill out this page) Winter 1250977 A7 B7 Ministry of Economic Affairs Zhici Property Bureau Staff Consumer Cooperative Printed 5, invention description (7) and copper chloride (CuCh), better with cuprous chloride During operation of the program, the appropriate chloride ion concentration can be maintained by the addition of hydrochloric acid (HC1). Figure 1 illustrates a dialkyl carbonate unit 10 with a coupled reaction zone 20, separation section 30, and purification zone. Section 40. Referring to Figure 1, the catalytic reaction of an alkanol, oxygen, and carbon monoxide can be carried out in a single reactor 50 or in two or more reactors 50. The conditions used to carry out this step should be selected to dialkyl carbonate. The yield of the ester is maximized while minimizing the degradation of the dialkyl carbonate. The reaction is preferably carried out in a single reactor 50 at a temperature of from about 50 ° C to about 250 ° C. Within this range, the temperature Preferably at least about 10 CTC. Within this range, up to about 150 ° C Preferably, the reactor 50 is maintained at a pressure of from about 15 to about 35 barg. Within this range, a pressure of at least about 20 barg is preferred. In this range, up to about 28 barg. The pressure is also good. If it is a dual reactor system, the catalyst can be circulated between the tanks. The catalyst concentration should be high enough to produce an acceptable yield, but should be kept below the catalyst solids in the reactor 50. The concentration of the apparatus is set or blocked. The reactant alkanol, oxygen, and carbon monoxide are preferably added to a molar ratio of from about 0.5 to about 0.7: (about 0.04 to about 0.06): (about 0.8 to about 1.2). Preferred alkanol: carbon monoxide molar ratio (about 0.6): (about 0.05): (about 1). The amount of catalyst relative to the reactants depends on the type of the catalyst. For example, when the catalyst system comprises CuCl, the preferred catalyst concentration is from about .140 to about 180 grams per liter of the reaction mixture. The catalyst may be added from the catalyst tank 60 during operation. Preferably, a sufficient amount of HC1 is added to the reactor 50 from the hydrochloric acid tank 70 during the reaction to maintain a molar ratio of Cu:Cl close to 1.0. The concentration of the HC1 is preferably continuously measured and controlled by the addition of HC1. HC1 feed relative (please read the note on the back and fill out this page). Book paper size General Chinese National Standard (CNS) A4 specification (210X297 mm) -10- Ministry of Economic Affairs Zhici Property Bureau S Workers Consumption Cooperative Printed 1250977 ΑΊ __ Β 7 V. Description of the invention (j is preferred, at least about 95 percent is better, at least about 99 percent is better. In one embodiment, it is preferred to reduce the alkyl chloroformate concentration in the mixture to about one hundred Below 500 parts per million, preferably less than about 100 parts per million, more preferably less than about 30 parts per million. In any of the specific examples, the preferred system is shifted. In addition to less than about 1% by weight of dialkyl carbonate, preferably less than about 5 percent, more preferably less than about 1 percent. Although the process can be described as "removing less than about 10 percent of the dialkyl carbonate. Ester", but it is known that the concentration of dialkyl carbonate does not necessarily decrease, and may even increase. For example, if the alkyl chloroformate is reacted with methanol in Scheme V to form a dialkyl carbonate, the dialkyl carbonate is decomposed due to other reactions. Fast rate, the concentration of dialkyl carbonate After various factors including temperature, residence time, water concentration, methanol concentration, and hydrochloric acid concentration, the kinetics of the dimethyl carbonate method was thoroughly investigated, and the rate of decomposition of methyl chloroformate was found to be expressed as (1)-rMcF. = (ki[H20] + k2[MeOH])[MCF] (1) (Please read the notes on the back and fill out this page) where ι·Μυ is per unit volume of methyl chloroformate (MCF) The number of enthalpy changes, [H20], [Me〇H] and [MCF] are the instantaneous concentrations of water, methanol, and methyl chloroformate, expressed in moles per unit volume, while klS k2i is Individual rate constants according to equations (2) and (3) with temperature h = k] V38I/r (7) k2 = k2V7673/r (3) This paper scale applies to Chinese National Standard (CNS) A4 specification (210X 297 mm) ) -13- Ministry of Economic Affairs Zhici Property Bureau g (Industrial Consumer Cooperatives Printing ^ 1250977 A7 B7 V. Invention Description (j where k 1. = 2 · 0 9 X 1 0 m L / γπ ο 1 - mi η ' k 2 2 4 · 1 4 X 1 〇 10 in L / m ο 1 - in i η, and T is the temperature expressed in degrees Kelvin. In many cases, The concentration of water and methanol and the density of the solution are basically constant. Under these general power constraints, different power types can be used for different methods and device types. Those who are familiar with this technology can learn from relevant chemical reactions and The rate constants provided by this application are easily calculated for these expressions. For example, in a batch method, the rate of methyl chloroformate decomposition can be expressed as a function of residence time, expressed in equation (4): ^[MCF] !0t = 〇fii[H20] + Y2[MeOH])[MCF\ (4) where t is the length of stay expressed in minutes. This stay time t can be defined as the total time spent by the average molecule in the fluid channel π 0 . In a batch process, methyl chloroformate has at least about 50 percent by maintaining the mixture at a water concentration ([H20]), a methanol concentration ([Me〇H]), a temperature (T), and a residence time (1). The condition is removed, so that the parameter X / = exPH (2.09xl 〇 V · 638] '7) obtained according to equation (5) is 0] ten (4.14 x 10 丨 V - fine (5) has less than about 0.9値, wherein the water concentration and the methanol concentration are expressed in moles per milliliter, the temperature is expressed in degrees Celsius, and the residence time is expressed in minutes. The X is preferably less than about 0.5, less than about 0.2. More preferably, less than about 0.1 and more preferably less than about 0.05 and more preferably less than about 〇·〇 1. The water concentration may range from about 0.1 to about 50 moles per liter. Within this range, the water-based paper scale applies to the Chinese National Standard (CNS) A4 specification (210X297 mm)' (Please read the note on the back and fill it out) -14- 1250977 A7 ~_ V. Invention Description (j &quot;'--~ The concentration is preferably at least about 0.5 mol / liter, at least about 丨 Mo / liter. In this range, the water concentration is up to about 30 Mo / It is also better, up to about 2 〇 m / liter, preferably up to about 10 m / liter, and up to about 5 m / liter. The methanol concentration can be from about 】 to about 25 m. / liters. In this range, the methanol concentration is preferably at least about 5 moles / liter, more preferably at least about 1 mole / liter. In this range, the methanol concentration is about 2 〇 m / liter is also good ' Up to about 18 m / liter is preferred. The duration of stay may be from about ο" hours to about 1 hour. In this range, the stay may be at least about 1 hour, preferably at least about 2 hours. The stay time is preferably up to about 8 hours, preferably up to about 6 hours. The temperature may be from about 30 to about 130 ° C. Within this range, the temperature may be at least about 40 ° C, preferably at least about 50 ° C. More preferably, it is preferably at least about 60 ° C. In this range, the temperature can be up to about π 0 ° C, preferably up to about 100 t: more preferably up to about 90 ° C. Ideal steady-state piston type In the limit of the flow reactor, assuming that the density of the mixture is fixed, the rate of decomposition of methyl chloroformate can be used to represent the residence time t (in minutes) The formula is expressed as formula (3). The Ministry of Economic Affairs Zhici Property Bureau 8 Workers Consumption Cooperative Printed In the ideal steady-state continuous stirred tank reactor (CSTR), the concentration of methyl chloroformate is expressed as formula (6) [MCF] = [MCF]t=o (l/(l+k〇) (6) where [MCF], = 〇 is the original concentration of methyl chloroformate expressed in moles per milliliter, t is The time of stay is expressed in minutes, and k is expressed by the formula (7). The paper size is applicable to the Chinese National Standard (CIN'S) A4 specification (21〇X 297 mm) -15- 1250977 A7 B7 Qi Qi Zouzhici Property Bureau staff eliminates goods Cooperative printing 5, invention description (dk = ki[//2〇] + k2[A^O&quot;] (7) where kl, k2, [H2〇] and [Me〇H] are as defined above. In another embodiment relating to a batch reactor, the removal of the alkyl chloroformate from the mixture comprises maintaining the mixture at a concentration that includes methyl chloroformate ([MCF]l = 〇), water concentration ( Under the conditions of [H2〇]), methanol concentration ([Me〇H]), temperature ([T]), and residence time (1), the parameter ZZ MMCFU expH (2.09xl〇V- calculated according to the following formula (8) is made. 63_[//2〇] 十(4·ΐ4χΙ〇!ν__η[The secret system has less than about 5x1 (Γ6値, preferably less than about 1x10”, less than about 5xl (T7 is better, less than about 5xl (Ts is better) Wherein the original concentration, water concentration and methanol concentration of methyl chloroformate are expressed in moles per milliliter, the temperature is expressed in degrees Celsius, and the duration of stay is expressed in minutes. The temperature, residence time, The methanol concentration and water concentration are as described above. The original concentration of methyl chloroformate depends on the reaction conditions, but is generally about 5x 1 (T3 mole per liter to about 5x1 (Γ) mole per liter. This range The original concentration of methyl chloroformate can be at least about 1 χ] (Τ2 mol per liter. Within this range, methyl chloroformate The original concentration may also be up to about ixicr] mole per liter. In a preferred embodiment relating to a batch reactor, the removal of the alkyl chloroformate comprises subjecting the mixture to an original concentration comprising methyl chloroformate ([ MCF]t = 〇), original water concentration ([H2〇]....), original methanol concentration (please read the notes on the back and fill out this page) This paper scale applies to China National Standard (CNS) A4 specification (210X297 public) PCT) -16- 1250977 A7 B7 V. Description of invention (j ([MeOH]^.), hydrochloric acid original concentration ([HCl]l = Q), temperature (T), and residence time (1), The parameter calculated by equation (9) ζ X=txV{-[(2^9xlQ9)e^iT\H2〇U (9) has a parameter less than about 0.9, and the parameter γ Υ calculated according to formula (1〇) [ DMC]ls〇[H2〇U [DMC]n exp (6.6xl010)(exp(-6636/7))[7ia]/s0[DMC](=0 [h2〇u [DMC]^ (10) The r^iri% employee consumption cooperative printing system has a enthalpy of less than about 0.9, wherein the original concentration of dimethyl carbonate, the original concentration of water, the original concentration of methanol, and the original concentration of hydrochloric acid are expressed in moles per milliliter, and the temperature With The degree of residence is expressed in minutes, and the Y is preferably at least about 0.95, preferably at least about 0.99. Analytical techniques suitable for the determination of water, methanol, hydrochloric acid and dimethyl carbonate in the reaction mixture. As is well known. "Original concentration" means the concentration of a substance prior to the deliberate removal of the alkyl chloroformate. The original concentration of water and methanol is the same as the concentration of water and moir (the water and methanol concentrations are high under normal reaction conditions and are substantially constant during the removal of the alkyl chloroformate). The original concentration of dimethyl carbonate may range from about 〇 5 to about 10 耳 / liter. Within this range, the original concentration of the dimethyl carbonate is preferably at least about 1 mole/liter, more preferably at least about 2 moles/liter. Within this range, the original concentration of dimethyl carbonate is preferably up to about 8 ml/liter, preferably up to about 6 m/l. The concentration of HC1 in the mixture is applicable to the Chinese National Standard (CNS) A4 specification (21 〇 father 297 gong^*7 17 Ministry of Economic Affairs Zhici Property Bureau Negative Works Cooperatives Printing 1250977 A7 ______B7 ____ V. Invention Description ( ^ depends on the type and concentration of the catalyst used. The original concentration of carbonic acid depends on the type and amount of the catalyst, but generally it is about U10·3 to about 2X1CT1 mole per liter. In this range, the original hydrochloric acid The concentration may be at least about 5 x 1 0. 3 m / liter, at least about lxl (T2 mol / liter is better. In this range, the original concentration of hydrochloric acid is up to about lxicr1 mol / liter is also good, up to about 7xl0 · 2 mol/liter is preferred. The method can be operated, for example, in a batch, semi-batch, or continuous manner. In the particular embodiment illustrated in Figure 1, the mixture passes through a first heat exchanger 140 to The temperature of the mixture at 30 ° C is adjusted to about 130 ° C. Within this range, the temperature is preferably at least about 40 ° C, more preferably at least about 50 ° C. Within this range, the temperature is preferably up to about 80 ° C, Up to about 70 ° C is better. The term "heat exchanger" is used to heat Well-known devices for the reaction stream are generally carried out by exchanging heat between a source of thermal energy (such as steam) and a stream of chiller chemical reactions, but it is also known to include other types of equivalent heaters (such as electric heaters). It is fed into the fluid passage 110, which is used to increase the residence time of the mixture under conditions which maximize the decomposition of the alkyl chloroformate, which simultaneously minimizes the decomposition of the dialkyl carbonate. The system can remain completely condensed in the fluid channel 110. It is desirable to keep the condensate completely condensed since at least a portion of the alkyl chloroformate (e.g., methyl chloroformate) is in the vapor phase under the conditions used in the process. Stable in liquid phase. The residence time and temperature in fluid channel 1 10 is sufficient to remove sufficient alkyl chloroformate to prevent unacceptable downstream corrosion, but it should not be excessive to cause the desired dialkyl carbonate. The productivity and yield of the product are reduced. Figure 2 shows a simplified flow diagram representing the control method. In this method, the mixture is J---clothes-- (please read the notes on the back first) Fill in this page) --!· The book paper size applies to the Chinese National Standard (CNS) A4 specification (2丨0X297 mm) -18- 1250977 Α7 Β7 V. Invention description (j directly from the first gas-liquid separator 90 Flows to the first heat exchanger 140 and then to the acid removal column 160. Three specific embodiments of the fluid channel 110 are shown in Figures 3, 4 and 5. In a preferred embodiment, at least about 50% by weight of alkyl chloroformate, preferably at least 80%. In a more preferred embodiment, the alkyl chloroformate concentration is reduced to about 500 parts per million by weight based on the total weight of the mixture after removal of the alkyl chloroformate. The parts (ppm) or less are preferably about 1 part by weight to 0 parts by weight or less, more preferably about 30 parts by weight or less. The fluid passage Π0 is selected such that the total residence time between reactor 50 and acid removal column 160 is preferably from about 0.5 to about 10 hours. Within this range, the residence time is preferably at least about 1 hour, preferably at least about 2 hours. Within this range, the maximum stay time is about 8 hours, and the longest time is about 7 hours. Further, in one embodiment, as illustrated in Fig. 3, the fluid passage 110 includes two storage containers 120. These storage containers 120 can, for example, maintain the mixture at a temperature of about 55 ° C for about 2 hours. Preferably, each storage container 120 may have a length to volume (L/V) ratio of less than 5, preferably less than about 2. Although the two storage containers 120 are illustrated in the drawings, the number of storage containers in the fluid passage 11 is not particularly limited. Preferably, at least two storage containers 1 20 can be used, and the structure including 3, 4, 5, 6 or more storage containers 120 is also preferred. In another embodiment, as illustrated in Figure 4, the fluid channel Π0 comprises four storage containers 120. Such storage containers 120 can, for example, maintain the mixture at a temperature of about 70 ° C for a period of about 4 hours. Preferably, each storage container has a length (L/V) ratio of less than 5 and a volume (L/V) ratio of less than about 2. In another embodiment, as illustrated in Figure 5, the fluid channel Η can comprise a segment having an L/V of at least 5, preferably at least about 10. In short, the paper size of this section applies to the Chinese National Standard (CMS) Α4 specification (210X29*7 mm) (please read the note on the back and fill out this page). The Ministry of Economic Affairs Zhici Property Bureau employee consumption cooperative Printed -19- Ministry of Economic Affairs Zhici Property Bureau Staff Consumer Cooperative Printed 1250977 A7_B7_5, invention description (j can mean tubular section 130. The tubular section 130 with L/V>5 can promote the mixture The piston flow through the fluid passage 110, thus effectively utilizing the residence time to remove the alkyl chloroformate. In this particular example, the mixture is in a narrow section of one or more L/V &gt; Preferably, at least about 50 percent of the total residence time in the fluid channel 110 is preferred, and at least about 80 percent of the total residence time in the fluid channel 110 is better. Referring again to Figure 1, after exiting the fluid channel 1 1 0, The mixture may optionally pass through the second heat exchanger 150 to at least partially evaporate the mixture. Such a second heat exchanger 150 may have a residence time of less than 10 minutes. The evaporation step may also be without heat exchange. Love This is accomplished by reducing the pressure applied to the condensed mixture (e.g., by passing condensate into the acid stripper 160 maintained at a relatively low pressure). The evaporated mixture can then be treated to remove HC1 for injection. Preferably, the acid column 160 can also help remove any entrained catalyst (e.g., CuCl) which would otherwise cause downstream corrosion. In addition to the acid column 160, the evaporated condensate will preferably be borrowed. The liquid supplied by the countercurrent liquid line 170 flows countercurrently to a high point in the column (e.g., the third before). The countercurrent liquid can trap residual H C1 and other reactants, which can be moved from the bottom of the acid removal column 1 60. Instead, it is recycled to reactor 50. The dialkyl carbonate mixture can be removed from the top of acid column 160 and, if appropriate, passed into azeotrope column 180. As shown in Figure 6, selectivity can be included after acid column 1 60 removal. Ion exchange resin bed 1 90, or any other location downstream of acid column 160. Preferably, after removal of water from the product dialkyl carbonate stream of purification section 40, a bed of selective ion exchange resin 1 90 is included. In a preferred embodiment, the device does not include Ion exchange resin bed 190. (Please read the back of the note and then fill out this page.) This paper size is applicable to the national standard (CNS) Α4 specification (210X 297 mm) • 20- Ministry of Economic Affairs Intellectual Property Office Consumer Cooperative Printed 1250977 A7 ____ B7_ V. INSTRUCTION DESCRIPTION (^ In a preferred embodiment, the method comprises reducing the concentration of hydrochloric acid in the mixture to a total of about 1 X 1 组成 of the composition after removal of hydrochloric acid • 3 m / liter or less, preferably less than about 5 x 10 4 m / liter, more preferably less than about lxio · 4 m / liter. In a preferred embodiment, the separation section 3 is located downstream of the azeotrope 18 8 and the purification subsection 40 does not require corrosion protection. The equipment upstream of the azeotrope column 180 is preferably resistant to corrosion, for example, it may be provided with a glass liner. The term "corrosion resistance" is used to describe a hydrochloric acid that can withstand 500 ppm of the reaction mixture at a temperature of from about 5 (TC to about 135 °C), substantially not for a relatively short period of time (eg, six months). Corrosive materials. Glass-lined containers, precious metal (eg molybdenum) lined containers and specific steels such as HASTELLOY® and CHROMALLOY® are considered corrosion-resistant materials, while steels that are generally unmodified to promote corrosion resistance are not considered Corrosion resistance. At least a portion of the azeotrope column 180 can be made of a corrosion resistant material. In a preferred embodiment, the bottom of the azeotrope column 180 can be made of anti-corrosion uranium steel, and the top of the tower can generally be In one embodiment of the apparatus of stainless steel crucible, as illustrated in Figures i and 3 to 6, the alkyl chloroformate is removed in the fluid channel 11 。. In another embodiment of the apparatus, as illustrated in Figure 7, The mixture is present in the gas-liquid separation vessels 90 and 100 for a period of time and temperature sufficient to remove the alkyl chloroformate. In other words, the fluid passage 11 comprises a gas-liquid separation vessel 90 and a crucible. For example, Mixed The condensed phase can be maintained in the gas-liquid separation vessel to substantially decompose by reacting with water and methanol. In this specific example, the first heat exchanger 140 and the storage container 120 are not necessarily applicable to the paper scale. Country &amp; Standard (CMS } A4 Specification (21 〇X 别) ~ -21 - ----; -*---一衣 - (Read the first note on the back and fill out this page), 1Τ Economy Ministry of Commerce, Staff and Consumers Cooperatives Print 3⁄4 1250977 A7 B7 V. Inventive Note (j. In another specific example of the device, as illustrated in Figure 8, the alkyl chloroformate can be in the gas/liquid separation The fluid passages 110 before the containers 90 and 100 are removed. In this embodiment, one of the aforementioned techniques for removing the alkyl chloroformate may be employed upstream of the gas-liquid separation vessels 90 and 1 . In another embodiment, the hydrochloric acid can be removed from the mixture prior to removal of the alkyl chloroformate as illustrated in Figure 9. In this embodiment, the alkyl chloroformate is removed under steam rather than the liquid phase. For example, referring to FIG. 9 , the fluid channel 110 can be after the azeotrope column 180 For example, it can be inserted into the azeotrope vapor outlet line 210. In this specific example, the first heat exchanger 140 and the storage container 120 illustrated in Fig. 3 can be omitted. In this embodiment, the fluid channel 1 1 0 It includes a device suitable for removing an alkyl chloroformate from a vapor phase (for example, an ion exchange resin, an absorbent bed, a vapor phase film, etc.), and the alkyl chloroformate does not require cold condensation. A preferred embodiment is a preparation. A method of dialkyl carbonate, comprising: reacting an alkanol, oxygen, carbon monoxide, and a catalyst to form a mixture comprising dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide; The mixture is passed through the fluid passage 1 1 0 at a temperature of from about 80 ° C for a residence time of from about 1 hour to about 10 hours. Another preferred embodiment is a device for preparing a dialkyl carbonate, which comprises reacting an alkanol, oxygen, carbon monoxide and a catalyst to form a dialkyl carbonate, an alkyl chloroformate, hydrochloric acid, water, a device for the mixture of carbon dioxide and carbon monoxide; and a device for removing alkyl chloroformate from the mixture. This paper scale applies to China National Standard (CNS) A4 specification (2) 0X 297 mm)~ (Please read the note on the back and fill out this page) -22- Ministry of Economic Affairs Intellectual Property Bureau 8 Workers Consumption Cooperative Printed 1250977 A7 ______B7 V. Description of the Invention (Another preferred embodiment is a device for preparing a dialkyl carbonate, which comprises reacting a house alcohol, oxygen, carbon monoxide and a catalyst to form a dialkyl carbonate, an alkyl chloroformate a reactor for the mixture of ester, hydrochloric acid, water, carbon dioxide, and carbon monoxide; and a fluid passage 110 for removing the alkyl chloroformate. The dialkyl carbonate prepared by the method can be used to prepare a diaryl carbonate. The diaryl carbonate can be formed by reacting a dialkyl carbonate with an aryl hydroxide (refer to the above-mentioned Scheme I). The diaryl carbonate can be reacted with a dihydric phenol in order to form a polycarbonate ( Referring to the aforementioned flow chart II). For example, the dimethyl carbonate prepared by the method can be reacted with a phenate to form diphenyl carbonate, which can then be reacted with bisphenol A to form a polycarbonate. This is illustrated by the following non-limiting examples.Example 1 An apparatus was constructed according to the simplified Figure 2, operated to produce dimethyl carbonate. Corrosion damage was observed in and downstream of the azeotrope tower 80. After thorough experimentation, it was determined. Corrosion damage is caused by methyl chloroformate passing through the acid separation column. In detail, the azeotrope column 180 is found to contain 300 parts by weight (ppm) of methyl chloroformate in a concentration of parts per million. 2 to 5 The decomposition kinetics of methyl chloroformate were investigated under four different conditions. The method for determining methyl chloroformate in the sample was as follows. For Example 2, 32 ml (mL) of dimethyl carbonate was used. 〇ml contains 50mg of biphenyl standard (please read the note on the back and fill out this page) This paper scale applies to Chinese National Standard (CNS) A4 specification (· 2!0X297 mm) -23- 1250977 A7 B7 V. INSTRUCTIONS (21) Dimethyl carbonate, 63 ml of methanol, and 5 ml of water were added to a 250 ml flask equipped with a thermometer, a condenser, and a sampling port. (Toluene may be used instead of methanol/water solution. ). The formation of a uniform solution is placed In the bath, the temperature of the solution was kept constant at 50 ° C. At time zero, 8 1.7 ml of pure methyl chloroformate was added to the solution (1,000 ppm by weight)*. The sample was taken out and quenched by reacting methyl chloroformate with diisobutylamine in the sample to convert methyl chloroformate to methyl N,N,-diisobutyl carbamate. The amount of the N,N,-diisobutyl carbamic acid methyl ester is titrated using a standard silver nitrate solution to determine the content of ionic chlorine. The amount of methyl chloroformate is inferred by analyzing the ion chlorine of the original sample. The difference in chlorine concentration is equal to the concentration of methyl chloroformate because each equivalent of methyl chloroformate releases one equivalent of ionic chlorine upon derivatization. Alternatively, gas chromatography can be used to directly analyze the guanidinium carbamate, methyl hydrazine-diisobutyl ester, using internal standards. Table I below shows the decomposition rate constant (k) found for different conditions at 50 °C. Embodiment 2 corresponds to the foregoing case. Example 3 adds hydrochloric acid which is usually present in the actual reaction mixture. In Example 4, the effect of a small amount of sodium hydrogencarbonate was tested. In Example 5, the ratio of dimethyl carbonate to methanol was kept constant, but the amount of water was increased from 5 to 10%. The results are shown in Table I below. This paper scale applies to China National Standard (CNS) A4 specification (210X 297 public splash) (please read the notes on the back and fill in this page)

, 1T

-24- 1250977 A7 B7 V. INSTRUCTIONS (

Table I DMC (wt%) MeOH (wt%) H2 〇 (wt%) Temp (°C) k (min*1) Ex. 2 45 50 5 50 0.043 Ex. 3* 45 50 5 50 0.043 Ex. 4* * 45 50 5 50 1 0.480 Ex. 5*** 43 47 10 50 0.055 * Same as in Example 2, the different parts also contain 1 000 ppm of HCl, which is the same as the effluent of reactor 50. μ is the same as in Example 2, except that 1.6 equivalents of NaHCCh ° * * * is added to 1 000 ppm of MCF, which is the same as in Example 2. The difference in water % is 1%, but the ratio of DMC/Me〇H is not Change, only the overall reduction. The plot of the logarithm of methyl chloroformate concentration versus time is a straight line and is suitable for a quasi-first-order dynamic model. This property can be found even in the presence of hydrochloric acid, and therefore, such a method can be used to determine the concentration of methyl chloroformate in a specific sample. A comparison of Examples 2 and 5 shows that the rate constant k was only slightly changed when analyzing a sample in which the water content was changed by a factor of two. Comparison of Examples 2 and 3 It has been unexpectedly shown that the addition of _HC1 does not affect the rate of methyl chloroformate decomposition found. Comparison of Examples 2 and 3 shows that even with a small amount of base, the reaction rate is increased by more than ten times. However, in practice, it is desirable to avoid strong alkali conditions, as it can also be applied to the Chinese National Standard (CMS) Ad specification (210X297 mm) on this paper scale.

Page Order I k Economic Department Intellectual Property Bureau S, / Industrial Consumer Cooperative Printed - 25 - Ministry of Economic Affairs Intellectual Property Bureau S Industrial Consumer Cooperative Printed 1250977 A7 B7 V. Invention Description (can increase the decomposition rate of dimethyl carbonate. Example 6, Comparative Example 1 These experiments show that the fluid channel 11 〇 can reduce the concentration of methyl chloroformate that will react to form HC1 in the downstream section of the apparatus. Referring to Figure 1, the two samples are based on having the first heat. The fluid sample was taken at different points in the dimethyl carbonate equipment of the structure of the exchanger 140 and the two storage vessels 120 (ie, corresponding to the structure of FIG. 3). The first sample (Comparative Example 1) Immediately before the first heat exchanger 140. The second sample (Example 6) is taken after the second storage container 120 (i.e., after the fluid channel 110). Each is brought to the laboratory for sampling. The function of time was used to determine the chlorine content. The results are shown in Table II. The data in Example 6 shows that the concentration of chloride ions is substantially fixed, indicating that the sample does not contain volatile, chlorine-generating substances such as methyl chloroformate. , the data of the control example 1 The chlorine concentration increases with time, which is consistent with the case where the original sample contains methyl chloroformate and decomposes over time to form other chloride ions. Therefore, the data as a whole is shown in the fluid-free channel 1 1 0, at The downstream of the apparatus (after the acid column 160) section substantially forms chlorine, causing corrosion, but the fluid passages 110 can decompose the alkyl chloroformate into chloride ions prior to the acid removal tower 160 to prevent downstream corrosion. (Please read the precautions on the back and fill out this page.) The paper size is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) -26- 1250977 Α7 Β7 V. Invention description (2j

Table II Time (h) Chlorine concentration (ρ ρ ΪΠ ) Ex. 6 C 〇m p. E X. 1 0 374 189 2 408 3 12 4 374 339 8 372 368 10 372 35 7 25 381 368 Example 7, comparison Example 2 In Comparative Example 2, the dimethyl carbonate equipment of Figure 2 was simplified to operate according to the conditions described in Table ΠΙ below. This equipment is the same as that detailed in Figure 1, with no first heat exchanger 140 and fluid passages 110 in different locations. Corrosion was found downstream of the azeotrope column 180. Second, the apparatus is modified to include a first heat exchanger 140, and two storage containers 120 are added to increase the length of stay (i.e., the structure of Figure 3). Figure 10 shows the measurement of residual ionized chlorine found in the sample obtained at the bottom of the azeotrope column 180 at various times, comparing the structures of Figures 2 and 3. The residual chlorine was titrated using a silver nitrate solution as described above. The data in Figure 2 has an average 値 671 pprn chlorine with a standard deviation of 370 ppm chlorine, while the structure of Figure 3 has an average lanthanide of 35 ppm chlorine with a standard deviation of 25 ppm chlorine. The data therefore shows a significant reduction in the chlorine concentration of the structure of Figure 3 relative to the structure of Figure 2. It is predicted that this reduction will be greater in the construction of Figures 1 and 6, wherein four storage containers 1 20 are used to provide a four hour stay in 7 01. Figure Η shows the concentration of Figure 3 and the paper size applies to the Chinese National Standard (CNS) A4 specification (2IOX297 mm) (please read the notes on the back and fill out this page)

Ministry of Economic Affairs, Zhichu Production Bureau, Negative Labor Consumption Cooperative Printed -27-1250977 A7 __ B7 V. Invention Description (^ Measurement of the concentration of methyl chloroformate entering and leaving the fluid channel 1 1 0. In other words, Figure 1 1 The point with "+" and marked "feed to the opposite MCF" corresponds to the measured enthalpy of the mixture entering the fluid channel 110; these points have 93 parts by weight (ppmw) The mean enthalpy and the standard deviation of 412 ppmw. The point marked " " and labeled "MCF from phase 0" corresponds to the measurement 混合物 of the mixture leaving the fluid channel 1 10 ; these points have an average enthalpy of 45 ppmw and 77 ppmw Standard deviation. These data clearly show that the device of Figure 3 can significantly reduce the concentration of methyl chloroformate in the process stream. (Please read the note on the back and fill out this page.) Printed by the Ministry of Economic Affairs, Zhici Property Bureau, Staff Cooperatives III. Condition Example 7 Comparative Example 2 (Structure of Fig. 2) (Structure of Fig. 3) The amount ratio Me〇H/〇2/C〇0.7/0.06/1 0.7/0.06/1 catalyst content fixed fixed reaction temperature (°C ) 133 133 Reaction pressure (barg) 23 23 Temperature (t;) 60 Acid tower feed evaporator temperature fc ) 90 90 Duration between the flash vessel and the acid tower 2 0.03, excluding both (hours) This paper scale applies to the Chinese national standard (CNS M4 specification (210X29*7 mm) -28- 1250977 A7 ___ B7 V. Description of invention (^

Table IV Structure φί勾是农g Deviation (ppm) _一? 13 (Comparative) - 671 ± 370 _i 2 (Invention) _ _ 351 25 Although the present invention has been described with reference to preferred embodiments, it is known to those skilled in the art that various changes can be made and equivalents can be substituted for the elements. Without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the basic scope. Therefore, the present invention is not limited to the specific embodiments disclosed, which are the preferred embodiments of Technical vocabulary not defined in detail in the present invention can be illustrated by Grant and H a c h, s C h e m i c a 1 D i c t i ο n a ι· y, 51 h e d., M c G r a w - H i 11, I n c . All patents and other references listed are incorporated herein by reference. (Please read the notes on the back and fill out this page.) Ministry of Economic Affairs, Intellectual Property Bureau, Staff, F, Co., Ltd., Print Purple, Applicable to China National Standard (CNS), A4 Specification (210X297 mm) -29-

Claims (1)

τ Α8 Β8 C8 D8 VI. Application for Patent Scope Annex 4 第 : Patent Application No. 91 1 1 7682 Application for Patent Application Replacement of the Republic of China on June 10, 1994 Revision % Ministry of Economic Affairs Intellectual Property Office Staff Consumer Cooperative Printed 1 . A method for preparing a dialkyl carbonate, comprising: reacting an alkanol, oxygen, carbon monoxide, and a catalyst to form a mixture comprising a dialkyl carbonate, an alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide; And removing the alkyl chloroformate from the mixture, wherein removing the alkyl chloroformate comprises employing at least one technique selected from the group consisting of heating, increasing pressure, increasing residence time, adding a polar solvent, adsorbing, using a film. Separation, pervaporation, passage through an ion exchange resin, exposure to a stoichiometric reagent, exposure to a catalyst reagent, and a combination of at least one of the foregoing techniques. The method of claim 1, wherein the sterol comprises (:! to an alkanol. 3. The method of claim 1, wherein the alkanol comprises 〇 to C6 - The method of claim 2, wherein the alkanol comprises methanol. The method of claim 2, wherein the alkanol, the oxygen, and the carbon monoxide are ( Approximately to about 0.7 alkanol): (about 〇.〇4 to about 〇.〇6 oxy): (about 0.8 to about oxidized carbon) is reacted at a molar ratio. 6 · The method of claim 丨'where the catalyst system contains (Please read the notes on the back and fill out this page) 1T 1250977 Ministry of Economic Affairs Intellectual Property Bureau Staff Consumer Cooperatives Printed A8 B8 C8 D8 VI. Application for Patent Range 2 Selection of Iron, Copper, Nickel 'Cobalt, Zinc, Antimony, Bismuth, Silver, Cadmium, Chain, Hungry a metal of the group consisting of ruthenium, platinum, gold, mercury, and a composition comprising at least one of the foregoing metals. 7. The method of claim 1, wherein the catalyst comprises copper. 8. The method of claim 1, wherein the catalyst comprises chloride ions. 9. The method of claim 1, wherein the catalyst comprises chloride ions and copper having a molar ratio of from about 0.5 to about 1.5. 1 0. The method of claim 1, wherein the reaction is carried out in a single reactor 50. The method of claim 1, wherein the reaction is carried out in the corrosion resistant reactor 50. 1 2 . The method of claim 1, further comprising removing carbon monoxide and a carbon monoxide from the mixed product. The method of claim 12, wherein at least about 90% of the carbon dioxide and at least about 90% of the carbon monoxide are removed from the mixture. 14. The method of claim 12, wherein the removing the carbon dioxide and carbon monoxide comprises passing the mixture through a plurality of gas-liquid separation vessels. The method of claim 14, wherein the reaction is performed under a first pressure, and the plurality of gas-liquid separation vessels are comprised having a percentage of about 1 〇 of the first pressure. The first gas-liquid of pressure (please read the note on the back and fill out this page) This paper scale applies to China National Standard (CNS) Α4 specification (210X297 mm) -2- Ministry of Economic Affairs Intellectual Property Bureau employee consumption cooperative 1250977 A8 B8 C8 D8 VI. Patent Application 3 A separation vessel, and a second gas-liquid separation vessel having a pressure of less than about 20 percent of the first pressure. The method of claim 1, wherein at least about 80% of the alkyl chloroformate is removed from the mixture. The method of claim 1, wherein at least about 90% of the alkyl chloroformate is removed from the mixture. The method of claim 1, wherein at least about 95% of the alkyl chloroformate is removed from the mixture. The method of claim 1, wherein at least about 99% of the chloroformic acid ester is removed from the mixture. 20. The method of claim </RTI> wherein the removing the alkyl chloroformate comprises removing less than 5 percent of the dialkyl carbonate. The method of claim 2, wherein the removing the alkyl chloroformate comprises removing less than 1% of the dialkyl carbonate. 22. The method of claim </RTI> wherein the removing the alkyl chloroformate comprises reducing the concentration of the alkyl chloroformate to less than about 500 parts by weight based on the total weight of the mixture. The method of claim 1, wherein the removal of the chloroformic acid chorus comprises reducing the concentration of the alkyl chloroformate to less than about 1 part per million by weight. The method of claim 1, wherein the removing the alkyl chloroformate comprises reducing the concentration of the alkyl chloroformate to about 3 parts by weight or less. 25 ·If you apply for the method of item 1 of the patent scope, it also includes removing the salt (please read the note on the back and then fill in the page). The paper size applies to the Chinese National Standard (CNS) A4 specification (210X297 mm) -3 - 1250977 A8 B8 C8 D8 Ministry of Economic Affairs Intellectual Property Bureau employee consumption cooperative printed six, the scope of application for patent 4 acid. The method of claim 25, wherein the removing the hydrochloric acid comprises reducing the concentration of hydrochloric acid to about 1 x 10 3 m or less per liter. 2 7 The method of claim 25, further comprising evaporating the mixture prior to removing hydrochloric acid. 28. The method of claim 27, wherein the evaporating less comprises heating the mixture, reducing the pressure applied to the mixture, or both. The method of claim 25, wherein the removing the hydrochloric acid comprises passing the mixture through the acid removal column 160. The method of claim 25, wherein the removing the hydrochloric acid comprises passing the mixture through the acid removal column 160 and the ion exchange resin. 3 1. The method of claim 1, wherein the method is operated continuously. 32. A method of preparing a dialkyl carbonate, comprising: reacting an alkanol, oxygen, carbon monoxide, and a catalyst to form a dialkyl carbonate, an alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide. a mixture; reducing the concentration of the alkyl chloroformate in the mixture to less than about 500 parts by weight based on the total weight of the mixture, and simultaneously removing less than about 1% of the dialkyl carbonate, Wherein reducing the concentration of the alkyl chloroformate comprises employing at least one technique selected from the group consisting of heating, increasing pressure, increasing residence time, adding a polar solvent, adsorbing, using membrane separation, pervaporation, passing through an ion exchange resin. Exposure to a stoichiometric reagent, exposure to a catalyst reagent, and a set of papers including at least one of the foregoing techniques applies to the Chinese National Standard (CNS) A4 specification (210X 297 mm) (please read the back note first) Please fill out this page again) _Package - , 1T -4 - 1250977 A8 B8 C8 D8 VI. Scope of application 5 methods; and remove hydrochloric acid from 5^: mixture. (Please read the note on the back and then fill out this page) 3 3 · A method for preparing a dialkyl carbonate, comprising: reacting an alkanol, oxygen, carbon monoxide, and a catalyst to form a dialkyl carbonate a first mixture of an alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide; removing an alkyl chloroformate from the first mixture to form a second mixture, wherein removing the alkyl chloroformate system comprises employing at least one selected Free technology for the following groups: heating, increasing pressure, increasing residence time, adding polar solvent, adsorption, separation using membranes, pervaporation, passing through ion exchange resins, exposure to stoichiometric reagents, exposure to catalytic reagents And comprising a combination of at least one of the foregoing techniques; and removing hydrochloric acid from the second mixture. 34. The method of claim 33, wherein the first mixture comprises steam of dialkyl carbonate and vapor of alkyl chloroformate. 35. The method of claim 34, further comprising condensing the dialkyl carbonate vapor and the alkyl chloroformate vapor. _ Ministry of Economic Affairs Intellectual Property Office Employees' Consumption Cooperative Printed 36. The method of claim 35, wherein the vapor of the dialkyl carbonate and the vapor of the alkyl chloroformate are condensed to produce a single liquid phase. 37. The method of claim 33, wherein the removing the alkyl chloroformate comprises using at least one gas/liquid separator. a method for producing a dialkyl carbonate, comprising: reacting an alkanol, oxygen, carbon monoxide, and a catalyst to form a dialkyl carbonate, an alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and A-5- The paper size applies to the Chinese National Standard (CNS) A4 specification (210X297 mm) 1250977 A8 B8 C8 D8 々, the patent application scope 6 the first mixture of carbon oxide; the hydrochloric acid is removed from the first mixture to form a second mixture; and removing the alkyl chloroformate from the second mixture, wherein removing the alkyl chloroformate comprises employing at least one technique selected from the group consisting of: heating to increase pressure, increase residence time, add polarity Solvent, adsorption, separation using membranes, pervaporation, passing through an ion exchange resin, exposure to a stoichiometric reagent, exposure to a catalyst reagent, and a combination of at least one of the foregoing techniques. A method for preparing dimethyl carbonate, comprising: combining methanol, oxygen, carbon monoxide, and a copper catalyst to form a vapor comprising dimethyl carbonate, methyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide. a first mixture; removing a portion of carbon dioxide and a portion of carbon monoxide from the first mixture to form a second mixture; at least partially vaporizing the vapor of the dimethyl carbonate and the vapor of the alkyl chloroformate to form a third mixture; Removing at least about 90% of methyl chloroformate and less than about 1% dimethyl carbonate from the third mixture to form a fourth mixture, wherein removing methyl chloroformate comprises employing at least one selected from the group consisting of The composition of the group: heating, increasing pressure, increasing residence time, adding polar solvent, adsorption, using membrane separation, pervaporation, passing through ion exchange resin, exposure to stoichiometric reagents, exposure to catalyst reagents, and A combination method comprising at least one of the foregoing techniques; and removing hydrochloric acid from the fourth mixture. This paper is applicable to China National Standard (CNS) A4 specification (210X297 mm) ~ ' -6 - (*Please read the back of the note and fill in this page) Installed by the Ministry of Economic Affairs, Intellectual Property Bureau, Staff Consumer Cooperatives, Printing 1250977, Ministry of Economic Affairs, Intellectual Property Office, Staff and Cooperatives, Co-operatives, Printing A8, B8, C8, D8, Patent Application No. 7 40. A method for preparing diaryl carbonate, which includes The diacetate is reacted with an aryl hydroxide, which is prepared according to the method of claim 1 of the patent application. A method of producing a polycarbonate comprising reacting a diaryl carbonate with a dihydric phenol, wherein the diaryl carbonate is prepared according to the method of claim 40 of the patent application. This paper size applies to the Chinese National Standard (CNS) A4 specification (210X297 mm) (please read the notes on the back and fill out this page) -7 -