CN1608044A - 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

The preparation method of dialkyl carbonate and the purposes in preparation diaryl carbonate and polycarbonate thereof

Background of invention

So polycarbonate resin is the material with practical value because of its physics and optical property.The preparation method of polycarbonate resin comprises interfacial and scorification.In interfacial, for example, in the United States Patent (USP) 4,360,659 of Sikdar, bis-phenol and carbonyl chloride reaction in the presence of solvent.At scorification, for example, in the United States Patent (USP) 3,153,008 of Fox, bis-phenol and diaryl carbonate reaction.Because scorification avoids using phosgene and solvent, so scorification is preferred at present.

The scorification of polycarbonate synthesis needs the industrial effective method for preparing diaryl carbonate.Known have several different methods that prepare diaryl carbonate, and the example of these class methods has the method for describing in the United States Patent (USP) 4,182,726 of Illuminati etc.In this method, by dialkyl carbonate and aryl hydroxides prepared in reaction diaryl carbonate (referring to following scheme I).

United States Patent (USP) 4,182,726 also shown diaryl carbonate can with dihydric phenol (dihydricphenol) prepared in reaction polycarbonate (referring to following scheme II).

The preferred method for preparing dialkyl carbonate, shown in following scheme III, for example at the United States Patent (USP) 4,218,391 and 4,318 of the United States Patent (USP) 5,527,943 of Rivetti etc. and Romano etc., described in 862.

United States Patent (USP) 5,527,943 (hereinafter to be referred as ' 943 patents) have also been described the known disadvantages according to the dialkyl carbonate method of scheme (III), promptly generate water byproduct.Equally, can in reaction mixture, add hydrochloric acid (HCl) continuously to keep the mol ratio between needed chlorine (chloride) and the copper.Therefore, in the air-flow of outflow reactor, find HCl, Catalysts Cu Cl and water usually.Hydrochloric acid and cupric chloride have severe corrosive under the situation of water because existing, must use the equipment that forms by corrosion resistant material so be equipped with the reaction member of the chemical workshop (plant) of dialkyl carbonate with this legal system, for example glass lined reaction vessel (glass-lined reaction vessel).Because corrosion resistant apparatus costs an arm and a leg, use this kind equipment as few as possible so wish chemical workshop.

The typical workshop of carrying out the dialkyl carbonate preparation according to scheme III comprises three unit: the reaction member that raw material is converted to dialkyl carbonate, the separating unit that separates dialkyl carbonate from unreacted monomer and by product removes and anhydrates and the further clean unit that separates dialkyl carbonate.From ' 943 patent as can be known, behind reaction member, from the materials flow (process stream) of technological process, remove HCl immediately, this moment, the amount of needed corrosion resistant apparatus can minimize, and this has got rid of the necessity at the corrosion resistant material of the separation in workshop and clean unit use costliness.' 943 patent also proposes, by the gas-liquid mixture that reaction is generated be exposed to by in the technological process liquid (process fluid) one of during the liquid formed flows, can finish and behind reaction member, from materials flow, remove HCl and possible halogenation mantoquita immediately.' 943 patent also shows, for fear of before removing HCl, reheating mixture, (acidremoval section) is preferred before in the depickling unit regulates employed operational condition so that the gaseous mixture that comes out can condensation or only is condensed into an insignificant degree (col.3, lines 17-30) from reactor.

In view of above situation, although preferably build such workshop, wherein removing hydrochloric acid and any halogenation mantoquita behind reaction member from materials flow is separating and clean unit corrodes avoiding, but be similar to the technology described in the patent of ' 943, promptly the technology of removing HCl and mantoquita by processing vaporization raw material from reaction mixture in using adverse current azeotropic fluidic pillar can not prevent the separation in downstream and the corrosion of clean unit.

Therefore, need a kind of method for preparing dialkyl carbonate, it can discern and eliminate remaining corrosion source.

The invention summary

A kind of method for preparing dialkyl carbonate can alleviate the above-mentioned of prior art and other defective and shortcoming, and it comprises: make alkanol, oxygen, carbon monoxide and catalyst reaction form the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide; From mixture, remove alkyl chloroformate then.

After a large amount of the effort, inventor of the present invention finds that synthetic can formation of dialkyl carbonate causes insoluble corrosive alkyl chloroformate by product.For example, form in the reaction of methylcarbonate (hereinafter to be referred as " DMC "), can form by product methyl-chloroformate (hereinafter to be referred as MCF) at methyl alcohol, carbon monoxide and oxygen.Because this MCF can enter separation and clean unit by taking off the HCl post, there, MCF and methyl alcohol and/or water react lentamente and form corrosive HCl, so before entering separation and clean unit, determine to need the step of removing MCF.

Other embodiment that hereinafter description is comprised preparation dialkyl carbonate ester apparatus.

The accompanying drawing summary

Fig. 1 is this diagram of installing first embodiment.

Fig. 2 is the sketch that is subjected to the corrosive comparison unit easily.

Fig. 3 is the sketch of device embodiment, comprises 2 storage vessels (holding vessel) 120 in the device in the fluid channel 110.

Fig. 4 is the sketch of device embodiment, comprises 4 storage vessels 120 in the device in the fluid channel 110.

Fig. 5 is the sketch of device embodiment, comprises a tubular portion (section) 130 in the device in the fluid channel 110.

Fig. 6 is the sketch that comprises the device embodiment of ion exchange resin bed 190.

Fig. 7 is the sketch of device embodiment, comprises first gas-liquid separator 90 and second gas-liquid separator 100 in the device in the fluid channel 110.

Fig. 8 is the sketch of device embodiment, and fluid channel 110 is before first gas-liquid separator 90 in the device.

Fig. 9 is the sketch of device embodiment, and fluid channel 110 is after azeotropic post 180 in the device.

Figure 10 is a function with type of device (Fig. 2 and Fig. 3) and time, the scatter diagram of chlorine (chloride) concentration of azeotropic post 180 bottoms.

Figure 11 be with Fig. 3 corresponding device thereof in, be function with time, enter scatter diagram with the methyl-chloroformate concentration of effluent fluid passage 110.

DESCRIPTION OF THE PREFERRED

An embodiment is such method, and it comprises: make alkanol, oxygen, carbon monoxide and catalyst reaction form the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide; From mixture, remove alkyl chloroformate then.

Employed alkanol in this method is not particularly limited, suitable alkanol comprise contain 1～12 carbon atom primary, the second month in a season and the tertiary alcohol, preferably contain the primary alkanol of 1～6 carbon atom, the utmost point is preferably methyl alcohol.

Can provide oxygen in any form, be preferably gaseous form.Suitable oxygen source comprises, for example, air and contain the oxysome that contains at least about the 95wt% molecular oxygen is preferably the oxysome that contains that contains 99wt% molecular oxygen at least.The suitable oxysome that contains can be to buy on the market, for example, and available from air goods (AirProducts).

Carbon monoxide preferably contains 95wt% at least to contain 90wt% at least, to be preferably, and more preferably contains the gas supply of the carbon monoxide of 99wt% at least.The suitable gas that contains carbon monoxide can be bought from the market, for example, and available from the air goods.

Appropriate catalyst comprises that those contain iron, copper, nickel, cobalt, zinc, ruthenium, rhodium, palladium, silver, cadmium, rhenium, osmium, iridium, platinum, gold and mercury etc. and comprise the combination one of at least of above-mentioned metal.Preferred catalyzer can comprise copper.Extremely preferred catalyzer comprises that mol ratio is about 0.5 to about 1.5 cupric ion and chlorion.In this scope, mol ratio is preferably at least about 0.8.In this scope, mol ratio is preferably about at the most 1.2 equally.Extremely preferred catalyzer comprises cuprous chloride and cupric chloride, with cuprous chloride for more extremely preferred.In the operating process of this method, can keep suitable chlorine ion concentration by adding hydrochloric acid (HCl).

Fig. 1 graphic extension contains the dialkyl carbonate plant 10 of reaction member 20, separating unit 30 and the clean unit 40 of connection.With reference to figure 1, the catalyzed reaction of alkanol, oxygen and carbon monoxide can be carried out in single reactor 50 or 2 or a plurality of reactor 50.Should select to carry out the condition of this step reaction so that the maximum production of dialkyl carbonate, the minimum degradation of dialkyl carbonate simultaneously.Preferably under about 50 ℃～about 250 ℃, in single reactor 50, carry out this reaction.In this scope, temperature is preferably at least about 100 ℃.In this scope, temperature is preferably about at the most 150 ℃ equally.The pressure of reactor 50 preferably be maintained at about 15 to (bargauge) between about 35 pressure (barg); In this scope, pressure is preferably at least about 20barg; In this scope, pressure is preferably 28barg at the most equally.Under the situation of two reactor system, catalyzer can recycle between container (tank).Although catalyst concn is should be enough high producing acceptable output, catalyst concn should be lower than and not cause catalyzer to solidify in reactor 50 or the concentration of occluding device.Reactant alkanol, oxygen and carbon monoxide are separately preferably with (about 0.5 to about 0.7): (about 0.04 to about 0.06): the mol ratio of (about 0.8 to about 1.2) adds.Extremely preferred alkanol: oxygen: the mol ratio of carbon monoxide is (about 0.6): (about 0.05): (about 1).

The kind that will depend on catalyzer with respect to the employed catalytic amount of reactant.For example, when catalyzer comprises CuCl, extremely preferred catalyst concn be in every liter of reaction mixture about 140 grams to 180 gram catalyzer.In operating process, from catalyst container 60 (catalyst tank), add catalyzer during beginning.In reaction process in order to keep Cu near 1.0: the Cl mol ratio, enough HCl preferably are added to the reactor 50 from hydrochloric acid container 70.HCl concentration is preferably determined and control continuously by adding HCl.Usually, the mass ratio of HCl charging and whole liquid feedings is about 6 * 10 ^-4To about 8 * 10 ^-4

Reaction generates the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide.This mixture also comprises remaining methyl alcohol and oxygen and such as the by product of alkyl chloride and dialkyl ether.This mixture takes out from reactor 50 with the form of gas usually.Term " steam " is meant the gaseous state organic constituent of mixture, for example Zheng Fa dialkyl carbonate, alcohol, alkyl chloroformate etc. and be meant water vapour.That is to say that term " steam " is meant to have the fluid that is at least-50 ℃ of boiling points under a normal atmosphere.On the contrary, " gas " is meant gasiform oxygen, carbonic acid gas, carbon monoxide and optional nitrogen.That is to say that term " gas " is meant the fluid that has less than-50 ℃ of boiling points under a normal atmosphere.First gas-liquid separator 90 is supplied with in steam condensation at least in part in condenser 80 then.This device can randomly use single gas-liquid separator or use a plurality of (promptly at least 2; Preferably about at the most 5) gas-liquid separator.The pressure that keeps first gas-liquid separator 90 be reactor 50 pressure about 10% within, preferred within about 1%.Capable of circulation from first gas-liquid separator 90 effluent air, for example reuse excessive carbon monoxide.This mixture is delivered in second gas-liquid separator 100, second gas-liquid separator 100 less than the pressure of reactor 50 pressure about 20% (for example preferably has, preferably less than 3 pressure, more preferably about 0.2 pressure) with preferred acquisition, weight by residual gas in the mixture, at least about 90%, at least 95% separation more preferably.In a utmost point embodiment preferred, from mixture, remove all gas basically.The waste gas of from second gas-liquid separator 100, removing also capable of circulation.Before entering first gas-liquid separator 90 and between first gas-liquid separator 90 and second gas-liquid separator 100, the form that steam in the mixture is preferably partial condensation (promptly, at least about 10% condensation), more preferably be the form (that is, at least about 90% condensation) of total condensation.

In the embodiment depicted in fig. 1, can be single liquid phase from second gas-liquid separator, 100 effusive mixtures.After flowing out from second gas-liquid separator 100, mixture can continue the fluid channel 110 by remove alkyl chloroformate from mixture.Be understood that term about a certain particular chemical kind " is removed (remove) " and " removing (removal) " comprises any chemistry or the physical method that reduce this kind concentration in the mixture.Available any method is removed alkyl chloroformate from condensation product, some preferable methods comprise heating, pressure boost, the increase residence time, add polar solvent, absorption, membrane sepn (comprising that gas separates with liquid membrane), pervaporation (pervaporating), by ion exchange resin, be exposed to stoichiometry reagent and be exposed to catalytic reagent etc. and comprise combination at least a in the above-mentioned technology.In preferred embodiments, by from mixture, removing alkyl chloroformate with water (referring to scheme IV) or alcohol (referring to plan V) reaction.

Also can preferably remove alkyl chloroformate and need not to make mixture to pass through ion exchange resin, reason is to install and use this resin costliness.Also can preferably from mixture, remove at least about 50%, more preferably at least about 90%, also more preferably at least about 95%, even more preferably at least about 99% alkyl chloroformate.In one embodiment, also can preferably reduce the concentration of alkyl chloroformate in the mixture extremely less than about 500ppm, more preferably less than about 100ppm, also more preferably less than about 30ppm.In any one embodiment of these embodiments, also can preferably remove less than about 10%, more preferably remove less than about 5%, also more preferably remove dialkyl carbonate less than about 1%.Although this method can be called " removing less than about 10% said dialkyl carbonate ", be understood that the concentration that does not need to reduce on the contrary even increase dialkyl carbonate.For example, if because other reaction, it is faster than decomposing dialkyl carbonate that alkyl chloroformate and methyl alcohol reaction form the plan V of dialkyl carbonate, and then the concentration of dialkyl carbonate can increase.

The methylcarbonate method of the factors vary by utilization being comprised temperature, the residence time, water concentration and methanol concentration and concentration of hydrochloric acid is carried out dynamics research widely, and inventor of the present invention has been found that the rate of decomposition of methyl-chloroformate can use following formula (1) expression

-r _MCF=(k ₁[H ₂O]+k ₂[MeOH]) MCF] (1) r wherein _MCFIt is the mole velocity of variation of methyl-chloroformate (MCF) in the per unit volume; [H ₂O], [MeOH] and [MCF] be respectively the instantaneous concentration (instantaneousconcentration) of water, methyl alcohol and methyl-chloroformate, unit is the mole number of per unit volume; k ₁And k ₂Be temperature variant rate constant, it is respectively according to formula (2) and (3):

${\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A0282032200281.png"\; state="\{\{state\}\}">k</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A0282032200281.png"\; state="\{\{state\}\}">k</figure-callout>}}_1^0{e}^{-6381/T}---\left(2\right)$

$k_2=k_2^0{e}^{-7673/T}---\left(3\right)$

Wherein ${\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="A0282032200281.png"\; state="\{\{state\}\}">k</figure-callout>}}_1^0=2.09\&times;{10}^9\mathrm{mL}/\mathrm{mol}-\min ,$ $k_2^0=4.14\&times;{10}^{10}\mathrm{mL}/\mathrm{mol}-\min ,$ T is an absolute temperature, and unit is K.

As a rule, suppose the concentration of water and methyl alcohol and solution density constant basically be effective.Within these total dynamics constraint conditions, can use different kinetics expression formulas to represent various process and type of device.Those of ordinary skill in the art, after the knowledge that has possessed relevant chemical reaction that the application provides and rate constant, can derive these expression formulas easily, for example, in batch process (batch process), the speed that methyl-chloroformate decomposes can be expressed as the function of the residence time, as the formula (4):

-d[MCF]/dt=(k ₁[H ₂O]+k ₂[MeOH]) [MCF] (4) wherein t be the residence time, unit is minute.Residence time t may be defined as the full time that a mean molecule is consumed in fluid channel 110.In batch process, by comprising water concentration ([H ₂O]), keep mixture under methanol concentration ([MeOH]), temperature (T) and the situation of the residence time (t), can remove at least about 50% methyl-chloroformate, therefore according to formula (5), the value of parameter X is less than about 0.9,

Wherein water concentration and methanol concentration are expressed as mol/mL, and thermometer is shown as absolute temperature K, and the residence time is expressed as minute.The X value can be preferably less than about 0.5, be more preferably less than approximately 0.2, also be more preferably less than approximately 0.1, even be more preferably less than approximately 0.05, still be more preferably less than about 0.01.Water concentration can be between about 0.1～about 50mol/L.In this scope, water concentration can be preferably at least about 0.5mol/L, more preferably at least about 1mol/L.Equally in this scope, water concentration can preferably about at the most 30mol/L, more preferably about at the most 20mol/L, also more preferably about at the most 10mol/L, even more preferably about at the most 5mol/L.Methanol concentration can be between about 1～about 25mol/L.In this scope, methanol concentration can be preferably at least about 5mol/L, more preferably at least about 10mol/L.Equally in this scope, methanol concentration can preferably about at the most 20mol/L, more preferably about at the most 18mol/L.The residence time can be between about 0.5～about 10 hours.In this scope, the residence time can be preferably at least about 1 hour, more preferably at least about 2 hours.Equally in this scope, the residence time can preferably about at the most 8 hours, more preferably about at the most 6 hours.Temperature can be between about 30～about 130 ℃.In this scope, temperature can be preferably at least about 40 ℃, more preferably at least about 50 ℃, also more preferably at least about 60 ℃.Equally in this scope, temperature can preferably about at the most 110 ℃, and more preferably about at the most 100 ℃, also more preferably about at the most 90 ℃.

Under the limit of desirable stable state plug flow reactor and suppose that the density of mixture is under the situation of constant, the methyl-chloroformate rate of decomposition can be according to formula (3) expression, and wherein t represents the residence time, and unit is minute.

For desirable stable state continuous stirred tank reactor (CSTR) (CSTR), the concentration of methyl-chloroformate is represented by formula (6):

[MCF]=[MCF] _T=0(1/ (1+kt)) (6) are [MCF] wherein _T=0Be the starting point concentration of methyl-chloroformate, unit is mol/mL; T is the residence time, and unit is minute; K is represented by formula (7):

K=k ₁[H ₂O]+k ₂[MeOH] (7) are k wherein ₁, k ₂, [H ₂O] and [MeOH] definition is as above.

In another embodiment of relevant batch reactor (batch reactor), the method for removing alkyl chloroformate from mixture is included in the starting point concentration ([MCF] that comprises methyl-chloroformate _T=0), water concentration [H ₂O], keep mixture under methanol concentration [MeOH], temperature (T) and the situation of the residence time (t), therefore according to the value of formula (8) calculating parameter Z less than about 5 * 10 ^-6, preferably less than about 1 * 10 ^-6, be more preferably less than about 5 * 10 ^-7, even preferably less than about 5 * 10 ^-8,

Wherein the starting point concentration of methyl-chloroformate, water concentration and methanol concentration are expressed as mol/mL; Thermometer is shown absolute temperature K; The residence time is expressed as minute.Temperature in this expression formula, the residence time, methanol concentration and water concentration are as above-mentioned.Although the starting point concentration of methyl-chloroformate will depend on reactor condition, it typically is about 5 * 10 ^-3～about 5 * 10 ^-1Mol/L.In this scope, the starting point concentration of methyl-chloroformate can be at least about 1 * 10 ^-2Mol/L.Equally in this scope, the starting point concentration of methyl-chloroformate can about at the most 1 * 10 ^-1Mol/L.

In a preferred embodiment of relevant batch reactor, the method for removing alkyl chloroformate is included in and comprises methylcarbonate starting point concentration ([DMC] _T=0), water starting point concentration [H ₂O] _T=0, methyl alcohol starting point concentration [MeOH] _T=0, hydrochloric acid starting point concentration ([HCl] _T=0), treating mixture under temperature (T) and the situation of the residence time (t), therefore according to the value of formula (9) calculating parameter X at least about 0.9,

According to the value of formula (10) calculating parameter Y at least about 0.9,

$Y=\frac{(1-\frac{{\left[H_{2}O\right]}_{t=0}}{{\left[\mathrm{DMC}\right]}_{t=0}})}{(1-\left(\frac{{\left[H_{2}O\right]}_{t=0}}{{\left[\mathrm{DMC}\right]}_{t=0}}\right)\left(\exp \left((6.6\&times;{10}^{10})\right(\exp (-6636/T)){\left[\mathrm{HCl}\right]}_{t=0}{\left[\mathrm{DMC}\right]}_{t=0}(\frac{{\left[H_{2}O\right]}_{t=0}}{{\left[\mathrm{DMC}\right]}_{t=0}}-1)t\right)))}---\left(10\right)$

Wherein, methylcarbonate starting point concentration, water starting point concentration, methyl alcohol starting point concentration and hydrochloric acid starting point concentration are expressed as mol/mL, and thermometer is shown absolute temperature K, and the residence time is expressed as minute.The Y value is preferably at least about 0.95, more preferably at least about 0.99.The suitable analysis technology of determining the starting point concentration of water in the reaction mixture, methyl alcohol, hydrochloric acid and methylcarbonate is as known in the art.Term " starting point concentration " is meant the concentration of species before having a mind to remove alkyl chloroformate.The concentration identical (under common reaction conditions, the concentration of water and methyl alcohol is big, and is in removing the process of alkyl chloroformate, constant basically) of the starting point concentration of water and methyl alcohol and above-mentioned water and methyl alcohol.The methylcarbonate starting point concentration can be between about 0.5～about 10mol/L.In this scope, initial concentration of dimethyl carbonate solution can be preferably at least about 1mol/L, more preferably at least about 2mol/L.Equally in this scope, the methylcarbonate starting point concentration can preferably about at the most 8mol/L, more preferably about at the most 6mol/L.HCl concentration depends on the kind and the concentration of the catalyzer that uses in the mixture.Although the hydrochloric acid starting point concentration will depend on the kind and the concentration of catalyzer, it typically is about 1 * 10 ^-3～2 * 10 ^-1Between the mol/L.In this scope, the hydrochloric acid starting point concentration can be preferably at least about 5 * 10 ^-3Mol/L is more preferably at least about 1 * 10 ^-2Mol/L.Equally in this scope, the hydrochloric acid starting point concentration can be preferably about at the most 1 * 10 ^-1Mol/L, more preferably about at the most 7 * 10 ^-2Mol/L.

Available, for example, in batches, semi-batch or successive mode operate this method.

In specific embodiments shown in Figure 1, mixture by first interchanger (the first heatexchanger) 140 with the temperature of regulating mixture between about 30～about 130 ℃.In this scope, temperature can be preferably at least about 40 ℃, more preferably at least about 50 ℃.Equally in this scope, temperature can preferably about at the most 80 ℃, more preferably about at the most 70 ℃.A kind of known equipment that is used to heat chemical reaction flow described in term " interchanger ", exchanging heat between thermal source (for example, steam) and cold chemical reaction flow usually, but be understood that the well heater (for example, electric heater) that also comprises other form equivalence.Condensation product can enter fluid channel 110, increases the mixture residence time under this condition as the decomposition that minimizes dialkyl carbonate in the decomposition that maximizes alkyl chloroformate simultaneously.Condensation product can preferably keep total condensation in fluid channel 110.Because under this method working conditions, at least some alkyl chloroformates (for example, methyl-chloroformate) are more stable in gas phase than in liquid phase, so preferably keep the condensation product total condensation.

The residence time and temperature are preferably fully removed a large amount of alkyl chloroformates preventing the corrosion of unacceptable downstream in fluid channel 110, but they can not be excessive and cause output and the productive rate that unnecessarily reduces required dialkyl carbonate product.Fig. 2 shows the simplification artwork representative of comparison technology.In this technology, mixture directly flows out from first gas-liquid separator 90, enters first interchanger 140, enters depickling post 160 then.Three specific embodiments of fluid channel 110 are shown in Fig. 3,4 and 5.In preferred embodiments, remove alkyl chloroformate, more preferably remove at least about 80% at least about 50%.In a more preferred embodiment, the all wts of mixture is a benchmark behind the alkyl chloroformate to remove, reduce alkyl chloroformate concentration extremely by weight less than about 500ppm, more preferably by weight less than about 100ppm, also more preferably by weight less than about 30ppm.The preferred fluid channel 110 of selecting is so that the total residence time between reactor 50 and the depickling post 160 is between about 0.5～about 10 hours.In this scope, the residence time can be preferably at least about 1 hour, more preferably at least about 2 hours.Equally in this scope, the residence time can preferably about at the most 8 hours, more preferably about at the most 7 hours.

In one embodiment, as shown in Figure 3, fluid channel 110 comprises 2 storage vessels 120.This storage vessel 120 for example, can be kept mixture about 2 hours under about 55 ℃ of temperature.Each storage vessel 120 can preferably have the length-volume ratio (L/V) less than 5, is more preferably less than about 2.Although in this figure, shown 2 storage vessels 120, but the number of storage vessel 120 is not particularly limited in the convection cell passage 110, it can preferably use at least 2 storage vessels 120, comprise 3,4,5,6 or the configuration (configuration) of more storage vessels 120 also preferred.

In another embodiment, as shown in Figure 4, fluid channel 110 comprises 4 storage vessels 120.This storage vessel 120 for example, can be kept mixture about 4 hours under about 70 ℃ of temperature.Each storage vessel 120 can preferably have the length-volume ratio (L/V) less than 5, is more preferably less than about 2.

In also having an embodiment, as shown in Figure 5, fluid channel 110 comprises that L/V is at least 5, preferably at least about 10 part.For the sake of simplicity, this part can be called tubular portion 130.The tubular portion 130 of this L/V of having＞5 can promote the piston flow of mixture by fluid channel 110, thereby effectively utilizes the residence time to remove alkyl chloroformate.In this embodiment, mixture the residence time of the crevice of one or more L/V of having＞5 preferably account in the fluid channel 110 whole residence time at least about 50%, more preferably account in the fluid channel 110 whole residence time at least about 80%.

Refer again to Fig. 1, after mixture flows out fluid channel 110, can randomly be formed up to the mixture of small part vaporization by second interchanger 150.Second interchanger 150 can have the residence time less than 10 minutes.Under situation, also can finish pervaporation step (for example, making condensation product) by remaining on the depickling post 160 of lower pressure by the pressure that reduction is applied on the condensing mixt without interchanger.Then, can randomly handle vaporization mixture, preferably it is injected in the depickling post 160 to remove HCl.Depickling post 160 also can help to be removed any catalyzer of carrying under one's arms (for example, CuCl), otherwise catalyzer can cause downstream corrosion.In depickling post 160, the condensation product of vaporization can preferably meet with by adverse current fluid pipeline 170 and be conducted to elevated adverse current liquid in the post (for example, going up several the 3rd (upper third)).This adverse current liquid can be caught remaining HCl and other reactant that can remove and be circulated to reactor 50 from depickling post 160 bottoms.Can be from this dialkyl carbonate ester mixture of top removal of depickling post 160, and randomly make this mixture by azeotropic post 180.As shown in Figure 6, after depickling post 160 or relatively any downstream position of depickling post 160 also can comprise optional ion exchange resin bed 190.In clean unit 40, after water is removed, comprise that optional ion exchange resin bed is favourable from dialkyl carbonate product stream.In a preferred embodiment, this device does not comprise ion exchange resin bed 190.

In a preferred embodiment, this method comprises, components are benchmark to remove behind the hydrochloric acid all, reduces in the mixture concentration of hydrochloric acid to less than about 1 * 10 ^-3Mol/L is more preferably less than about 5 * 10 ^-4Mol/L, even be more preferably less than about 1 * 10 ^-4Mol/L.

In a preferred embodiment, the part of the separating unit 30 in azeotropic post 180 downstreams and to purify that subelement 40 need not be corrosion resistant.The evaluation method selecting optimal equipment of azeotropic post 180 upstreams is corrosion resistant; For example, it can be glass lined.Term " corrosion-resistant " be meant describe a kind ofly under about 50～about 135 ℃ of temperature, can resist 500ppm HCl in the reaction mixture, in short period relatively (for example, six months) do not have substantive corrosive material.Enamelled vessel, ward off the container of precious metal (for example tantalum) and can be considered to corrosion resistant material, but do not think withstand corrosion with the common stainless steel that improves erosion resistance through modification such as the special steel of HASTELLOY  and CHROMALLOY .Azeotropic post 180 can be prepared by corrosion resistant material to small part.In a preferred embodiment, the bottom of azeotropic post 180 can be equipped with by corrosion resistant steel, and the top of post can be by common stainless steel preparation.

In an embodiment of this device, shown in Fig. 1 and 3-6, in fluid channel 110, remove alkyl chloroformate.

In another embodiment of this device, as shown in Figure 7, this mixture stops the sufficiently long residence time to remove alkyl chloroformate in gas- liquid separator 90 and 100 under enough temperature.In other words, fluid channel 110 comprises gas-liquid separator 90 and 100.For example, mixture can be retained in the condensation mutually of gas-liquid separator until by decomposing to reach basically with water and methyl alcohol reaction.In this embodiment, first interchanger 140 and storage vessel 120 can be unnecessary.

In another embodiment of this device, as shown in Figure 8, can remove alkyl chloroformate in the fluid channel before being arranged in gas- liquid separator 90 and 100 110.In this embodiment, one of above-mentioned technology of removing alkyl chloroformate can be used in the upstream in gas- liquid separator 90 and 100.

In another embodiment of this device, as shown in Figure 9, can before removing alkyl chloroformate, from mixture, remove hydrochloric acid.In this embodiment, in gas phase rather than in the liquid phase, remove alkyl chloroformate.For example, with reference to figure 9, fluid channel 110 is after azeotropic post 180; For example, fluid channel 110 can be inserted in the azeotropic post vapour outlet pipeline 210.In this embodiment, can omit first interchanger 140 and storage vessel 120 shown in Figure 3.In this embodiment, fluid channel 110 can preferably include the device (for example, ion exchange resin, absorbent bed, vapor phase film etc.) that is fit to remove alkyl chloroformate from vapor phase, and alkyl chloroformate need not condensation.

Embodiment preferred is a kind of preparation method of dialkyl carbonate, and it comprises: make alkanol, oxygen, carbon monoxide and catalyst reaction form the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide; Under about 50～about 80 ℃ of temperature, make this mixture by fluid channel 110 then, the residence time is about 1～about 10 hours.

Another preferred embodiment is the device of preparation dialkyl carbonate, and it comprises: make alkanol, oxygen, carbon monoxide and catalyst reaction form the facility (means) of the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide; From this mixture, remove the facility of alkyl chloroformate.

Another preferred embodiment is the device of preparation dialkyl carbonate, and it comprises: make alkanol, oxygen, carbon monoxide and catalyst reaction form the reactor of the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide; Be used to remove the fluid channel 110 of alkyl chloroformate.

Dialkyl carbonate according to this method preparation is used to prepare diaryl carbonate.For example, the preparation of diaryl carbonate can be by dialkyl carbonate and aryl hydroxides reaction (seeing such scheme I).Can make this diaryl carbonate form polycarbonate (seeing such scheme II) with the dihydric phenol reaction successively.For example, can make methylcarbonate and phenoxide (phenoxide) reaction according to this method preparation form diphenyl carbonate, it forms polycarbonate with bisphenol-a reaction successively.

Hereinafter will further set forth the present invention by non-restrictive example.

Embodiment 1

The workshop of construction shown in sketch 2, and operation generates methylcarbonate.In azeotropic post 180, observe corrosion damage with the downstream.From extensive experimentation, being determined to corrosion damage is to be caused by the methyl-chloroformate by acid separation column.More specifically, find that methyl-chloroformate exists with 300ppm concentration by weight in azeotropic post 180.

Embodiment 2-5

Under four kinds of different conditions, the decomposition kinetics of research methyl-chloroformate.Determine that the process of methyl-chloroformate is as follows in the sample.In embodiment 2, toward be furnished with thermometer, condenser and sampling port the 250mL flask in add the 32mL methylcarbonate, contain target 63mL methyl alcohol and 5mL water in the 50mg biphenyl of 10ml methylcarbonate.(available toluene replacement methanol/water solution).The homogeneous phase solution that generates is placed oil bath, and solution temperature is held constant at 50 ℃.In time zero, with in the pure methyl-chloroformate adding solution of 81.7 microlitres (1000ppm is benchmark with weight).Take out sample in different time sections, and by making methyl-chloroformate and the reaction of diisobutyl amine in the sample make it cooling (quench), to convert methyl-chloroformate to N, N '-carboxylamine diisobutyl methyl esters (N, N '-diisobutyl methylcarbamate).Use standard silver nitrate drips of solution setting analysis N then, the content of N '-carboxylamine diisobutyl methyl esters is quantitatively to draw the chloride ion content that exists.Then, go out the content of methyl-chloroformate by the chloride ion content deducibility of analyzing original sample.Because after the derivatization, each equivalent of methyl-chloroformate discharges an equivalent of chlorion, so the difference of cl concn equals the concentration of methyl-chloroformate.In addition, can use gas-chromatography by using interior mark, direct analysis N, N '-carboxylamine diisobutyl methyl esters.

Following Table I shows under the different condition, observed decomposition rate constant (k) under 50 ℃.Embodiment 2 is consistent with the above embodiments.Embodiment 3 has added hydrochloric acid, and it is present in the real reaction mixture usually.The effect of a small amount of sodium bicarbonate of embodiment 4 tests.In embodiment 5, it is constant that the ratio of methylcarbonate and methyl alcohol keeps, but the content of water is increased to 10% from 5%.Summed up in the following Table I of test-results.

Table I

	???DMC ??(wt％)	??MeOH ?(wt％)	???H 2O ??(wt％)	Temperature (℃)	??????k ???(min -1)
						Embodiment 2	????45	???50	????5	???50	????0.043
Embodiment 3 *	????45	???50	????5	???50	????0.043
						Embodiment 4 **	????45	???50	????5	???50	????0.480
Embodiment 5 ***	????43	???47	????10	???50	????0.055

^*Identical with embodiment 2, difference is that it also contains 1000ppm HCl, and the waste gas that this and reactor 50 come out is similar.

^*Identical with embodiment 2, difference is, adds the 1.6 normal sodium bicarbonates that have with respect to 1000ppm MCF.

^{* *}Identical with embodiment 2, difference is that the percentage composition of water increases to 10%, but the ratio of DMC/MeOH remains unchanged, and just reduces on the whole.

Methyl-chloroformate concentration is linear to the logarithmic graph of time, the match single order kinetic model that is as the criterion.Even also observe this behavior under the situation of hydrochloric acid existing, therefore this method can be used for determining the concentration of methyl-chloroformate in the particular sample.Comparing embodiment 2 and 5 shows when the water-content of analytical sample changes 2 times, only observes velocity coefficient k and has less variation.Comparing embodiment 2 and 3 shows that unexpectedly the HCl of adding does not influence observed methyl-chloroformate rate of decomposition.Comparing embodiment 2 and 4 expressions are even a spot of alkali increases above 10 times speed of reaction.Yet, in fact preferably avoid using the alkaline condition, this is because they also can increase the rate of decomposition of methylcarbonate.

Embodiment 6, comparative example 1

These tests show, 110 pairs of fluid channels reduce to react the methyl-chloroformate that generates HCl in the downstream units in workshop concentration is effective.With reference to figure 1,,, obtain two kinds of samples to the sampling of technological process fluid at the different positions of the dimethyl carbonate plant that contains configuration (promptly consistent configuration) with Fig. 3 with first interchanger 140 and 2 storage vessels 120.Before first interchanger 140, take first sample (comparative example 1) immediately.Take second sample (embodiment 6) in second storage vessel, 120 backs (after being fluid channel 110).Sample is taken in the laboratory, determined that its chlorinity is the function in sampling time.The result as shown in Table II.The content substantially constant of the data presentation chlorion of embodiment 6, this shows the species that are not easy to generate chlorine in the sample, for example methyl-chloroformate.On the contrary, the data presentation chloride ion content of comparative example 1 increases as time passes, and is consistent with the existence of methyl-chloroformate in the initial sample, and decomposes to form unnecessary chlorion along with the time.Therefore, these data jointly show, under the situation that lacks fluid channel 110, a large amount of chlorions form the downstream units (after the depickling post 160) that can occur in the workshop, and cause corroding, but existing 110 pairs of fluid channels to decompose alkyl chloroformate before depickling post 160 is that chlorion is effectively, thereby prevents the downstream corrosion.

Table II

Time (hour)	Chlorine ion concentration (ppm)
				Embodiment 6	Comparative example 1
??????0	????374	????189
			??????2	????408	????312
??????4	????374	????339
			??????8	????372	????368
??????10	????372	????357
			??????25	????381	????368

Embodiment 7, comparative example 2

For comparative example 2, according to the conditional operation of describing in the following Table III according to the dimethyl carbonate plant shown in the sketch 2.The workshop of describing in detail among this workshop and Fig. 1 is similar, and difference is to lack first interchanger 140 and fluid channel 110.In azeotropic post 180, observe corrosion with the downstream.Then, this workshop is modified to and comprises first interchanger 140, and adding has 2 storage vessels 120 to prolong the residence time (that is the configuration of Fig. 3).Figure 10 represents the residual chlorine ion found from the sample that take out azeotropic post 180 bottoms, compare measuring result in time with 3 configurations with Fig. 2.The residual chlorine ion is determined by using above-mentioned silver nitrate titration.The average chlorine ion concentration of Fig. 2 configuration data is 671ppm, and the standard deviation of chlorine ion concentration is 370ppm; Yet the average chlorine ion concentration of Fig. 3 configuration data is 35ppm, and the standard deviation of chlorine ion concentration is 25ppm.Therefore, compare with Fig. 2 configuration, the chloride ion content of these data presentation Fig. 3 configuration significantly reduces.Measurable, for using 4 storage vessels 120 with Fig. 4 that 70 ℃ of following residence time of 4 hours are provided and 6 configuration, this reduction will in addition bigger.Figure 11 represents to enter and flows out the measuring result of concentration of methyl-chloroformate of the fluid channel 110 of Fig. 3.In other words, use "+" some expression and that indicate " MCF enters the fluid channel " corresponding to when mixture just enters fluid channel 110, to the measurement of mixture among Figure 11; By weight, the mean value of these points is 930ppm (ppmw), and standard deviation is 412ppmw.With " ■ " expression and point of indicating " MCF effluent fluid passage " corresponding to when the mixture outflow fluid channel 110, to the measurement of mixture; The mean value of these points is 45ppmw, and standard deviation is 77ppmw.These data clearly illustrate that according to the device of Fig. 3 effective to the concentration of the methyl-chloroformate in the remarkable minimizing process stream.

Table III

Condition	Embodiment 7 (Fig. 2 configuration)	Comparative example 2 (Fig. 3 configuration)
			??????MeOH/O 2/ CO mass ratio	?????0.7/0.06/1	??????0.7/0.06/1
Catalytic amount	Fixing	Fixing
			Temperature of reaction (℃)	????????133	?????????133
Reaction pressure (barg)	????????23	?????????23
			Preceding residence time heater temperature (℃)	????????60	?????????--
Acid post charging carburettor temperature (℃)	????????90	?????????90
			Between flushed channel and sour post, do not comprise both the residence time (hour)	????????2	????????0.03

Table IV

Configuration	Average chlorine ion concentration ± standard deviation (ppm)
		Fig. 3 (comparison)	671±370
Fig. 2 (invention)	35±25

Although the present invention describes according to preferred embodiment, those of ordinary skill in the art should be understood that without departing from the present invention, can make various modifications or its element is made identical replacement the present invention.In addition, under the situation that does not break away from its essential scope, can make multiple modification to be fit to the specific situation and the material of religious doctrine of the present invention.Therefore, the present invention is not that plan is restricted to enforcement optimal mode of the present invention with disclosed specific embodiments.But the present invention will comprise the whole embodiments that fall in the claim scope of appending.

Among the present invention in this scientific and technical terminology that is not specifically defined, can be at Grant and Hach ' sChemical Dictionary (5 ^ThEd., McGraw-Hill finds the explanation in Inc.).

Quote the patent of all references and other reference as a reference in this integral body.

Claims (42)

1. method for preparing dialkyl carbonate, it comprises:

Make alkanol, oxygen, carbon monoxide and catalyst reaction form the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide;

From said mixture, remove alkyl chloroformate.

2. according to the said method of claim 1, wherein said alkanol comprises the alkanol that contains 1～12 carbon atom.

3. according to the said method of claim 1, wherein said alkanol comprises the primary alkanol that contains 1～6 carbon atom.

4. according to the said method of claim 1, wherein said alkanol comprises methyl alcohol.

5. according to the said method of claim 1, wherein said alkanol, said oxygen and said carbon monoxide are with (about 0.5 to about 0.7 alkanol): (about 0.04 to about 0.06 oxygen): the molar ratio reaction of (about 0.8 to about 1.2 carbon monoxide).

6. according to the said method of claim 1, said catalyzer comprises a kind of metal in chosen from Fe, copper, nickel, cobalt, zinc, ruthenium, rhodium, palladium, silver, cadmium, rhenium, osmium, iridium, platinum, gold and the mercury, and comprises the combination one of at least of above-mentioned metal.

7. according to the said method of claim 1, wherein said catalyzer comprises copper.

8. according to the said method of claim 1, wherein said catalyzer comprises chlorion.

9. according to the said method of claim 1, wherein said catalyzer comprises that mol ratio is about 0.5 to about 1.5 chlorion and copper.

10. according to the said method of claim 1, wherein said reaction is carried out in single reactor 50.

11. according to the said method of claim 1, wherein said reaction is carried out in corrosion resistant reactor 50.

12., also comprise and from said mixture, remove carbonic acid gas and carbon monoxide according to the said method of claim 1.

13., wherein from said mixture, remove at least about 90% said carbonic acid gas with at least about 90% said carbon monoxide according to the said method of claim 12.

14. according to the said method of claim 12, wherein said carbonic acid gas and the carbon monoxide removed comprises and makes said mixture by a plurality of gas-liquid separators.

15. according to the said method of claim 14, wherein said reaction is carried out under first pressure, and said a plurality of gas-liquid separators comprise first gas-liquid separator of the pressure with said first pressure of about 10% and have second gas-liquid separator less than the pressure of about 20% said first pressure.

16., wherein from said mixture, remove said alkyl chloroformate at least about 80% according to the said method of claim 1.

17., wherein from said mixture, remove said alkyl chloroformate at least about 90% according to the said method of claim 1.

18., wherein from said mixture, remove said alkyl chloroformate at least about 95% according to the said method of claim 1.

19., wherein from said mixture, remove said alkyl chloroformate at least about 99% according to the said method of claim 1.

20. according to the said method of claim 1, the wherein said alkyl chloroformate of removing comprises and removing less than about 5% said dialkyl carbonate.

21. according to the said method of claim 1, the wherein said alkyl chloroformate of removing comprises and removing less than about 1% said dialkyl carbonate.

22. according to the said method of claim 1, the wherein said alkyl chloroformate of removing comprises that the concentration that reduces said alkyl chloroformate is extremely less than about 500ppm by weight.

23. according to the said method of claim 1, the wherein said alkyl chloroformate of removing comprises that the concentration that reduces said alkyl chloroformate is extremely less than about 100ppm by weight.

24. according to the said method of claim 1, the wherein said alkyl chloroformate of removing comprises that the concentration that reduces said alkyl chloroformate is extremely less than about 30ppm by weight.

25. according to the said method of claim 1, wherein said remove alkyl chloroformate comprise use be selected from heating, pressure boost, the increase residence time, add polar solvent, absorption, membrane sepn, pervaporation, by ion exchange resin, be exposed to stoichiometry reagent and be exposed in the catalytic reagent at least a technology and comprise combination at least a in the above-mentioned technology.

26., also comprise and remove hydrochloric acid according to the said method of claim 1.

27. according to the said method of claim 26, the wherein said hydrochloric acid of removing comprises that the reduction concentration of hydrochloric acid is extremely less than about 1 * 10 ^-3Mol/L.

28. according to the said method of claim 26, also be included in and remove before the said hydrochloric acid, the said mixture of vaporizing.

29. according to the said method of claim 28, wherein said vaporization comprises the said mixture of heating, reduces to be applied to pressure on the said mixture or both.

30. according to the said method of claim 26, the wherein said hydrochloric acid of removing comprises and makes said mixture by depickling post 160.

31. according to the said method of claim 26, the wherein said hydrochloric acid of removing comprises and makes said mixture by depickling post 160 and ion exchange resin.

32. according to the said method of claim 1, wherein said method is operate continuously.

33. a method for preparing dialkyl carbonate, it comprises:

Make alkanol, oxygen, carbon monoxide and catalyst reaction form the mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide;

The concentration that reduces said alkyl chloroformate in the said mixture is removed less than about 10% said dialkyl carbonate simultaneously to less than about 500ppm by weight;

From said mixture, remove hydrochloric acid.

34. a method for preparing dialkyl carbonate, it comprises:

Make alkanol, oxygen, carbon monoxide and catalyst reaction form first mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide;

From said first mixture, remove alkyl chloroformate to form second mixture;

From said second mixture, remove hydrochloric acid.

35. according to the said method of claim 34, wherein said first mixture comprises the steam of dialkyl carbonate and the steam of alkyl chloroformate.

36., also comprise said dialkyl carbonate steam of condensation and said alkyl chloroformate steam according to the said method of claim 35.

37. according to the said method of claim 36, said dialkyl carbonate steam of wherein said condensation and said alkyl chloroformate steam generate single liquid phase.

38. according to the said method of claim 34, the wherein said alkyl chloroformate of removing comprises at least one gas-liquid separator of use.

39. a method for preparing dialkyl carbonate, it comprises:

Make alkanol, oxygen, carbon monoxide and catalyst reaction form first mixture that contains dialkyl carbonate, alkyl chloroformate, hydrochloric acid, water, carbonic acid gas and carbon monoxide;

From said first mixture, remove hydrochloric acid to form second mixture;

From said second mixture, remove alkyl chloroformate.

40. a method for preparing methylcarbonate, it comprises:

Methyl alcohol, oxygen, carbon monoxide and copper catalyst are combined to form first mixture that contains methylcarbonate steam, methyl-chloroformate steam, hydrochloric acid, water, carbonic acid gas and carbon monoxide;

From said first mixture, remove said carbonic acid gas of part and the said carbon monoxide of part to form second mixture;

At least said dialkyl carbonate steam of partial condensation and said alkyl chloroformate steam are to form the 3rd mixture;

From said the 3rd mixture, remove at least about 90% said methyl-chloroformate and be less than about 1% said methylcarbonate to form 4 mixture;

From said 4 mixture, remove hydrochloric acid.

41. a method for preparing diaryl carbonate, it comprises makes dialkyl carbonate and aryl hydroxides reaction, and wherein dialkyl carbonate is according to the said method preparation of claim 1.

42. a method for preparing polycarbonate, it comprises makes diaryl carbonate and dihydric phenol reaction, and wherein diaryl carbonate is according to the said method preparation of claim 41.

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