Background technology
Alkylene carbonate is a kind of useful compound as organic solvent or reaction reagent.Especially, it can be used as the solvent of lithium two-pole cell and as the raw material of alkyl carbonate.
For the production of alkylene carbonate, the technology of alkylene oxide and carbon dioxide gas precursor reactant is conventional method, and to being used for such catalyst for reaction and method many reports is arranged.
Common industrial as producing the carbon dioxide that the alkylene carbonate raw material uses, it is the by product carbon dioxide that from the hydrogen production process of the method for producing ammonia, produces, the carbon dioxide that perhaps produces from fermenting process provides, and recovery of such carbonic acid gas process and purification step, its purity is not less than 99.5vol% usually.In addition, the carbon dioxide that further improves its purity on request can have been bought from the market.
The by product that carbonic acid gas also can be used as in the process for ethylene oxide production produces.For the production of oxyethane, can use such method usually, promptly by using silver catalyst to make the ethylene moiety oxidation, the complete oxidation of ethene is to carry out as the side reaction that can produce carbon dioxide when adopting this method.Because carbonic acid gas is harmful to the partial oxidation reaction of ethene, so common carbon dioxide is excluded, the carbon dioxide of eliminating is normally discharged into the atmosphere.
If this d/d by product carbon dioxide gas physical efficiency is used as the raw material of producing alkylene carbonate, very big benefit is not only arranged economically, and also be useful in aspect environment, because this carbon dioxide is greenhouse gases, can be fixed and can not discharges into the atmosphere.Especially, be under the situation of alkylene carbonate at the purpose product, because two kinds of raw materials can obtain from same factory, just might greatly simplify the equipment of the storage and the transportation of raw material.Therefore, very big economic benefit is arranged.
Use the carbon dioxide that produces as by product in the process for ethylene oxide production as producing for example being disclosed in of alkylene carbonate raw material itself, in the Japanese Patent open (KOKAI) 9-67365 number.
In addition, the separation and the recovery method of the by product carbonic acid gas that is produced in the oxirane production technology process for example have been disclosed in, in the Japanese Patent open (KOKAI) 50-40508 number.
The carbon dioxide that produces and reclaim as the by product in the oxirane production technology process is used to produce alkylene carbonate many advantages.But, the carbon dioxide of common this recovery and the carbon dioxide of described industrial use relatively, purity is quite low, contains in a large number usually, generally is not less than the hydro carbons of 1vol.%.In the production process of alkylene carbonate, feed carbon dioxide gas glut reactor, and unreacted carbon dioxide recycles, as impure carbon dioxide gas as described in using, owing to cause that hydro carbons is accumulated in the reaction system in the working cycle of described carbon dioxide, cause the dividing potential drop of carbon dioxide in reactor to reduce.This is harmful to the formation reaction of alkylene carbonate, and quickens undesirable side reaction, thereby influences the quality of product alkylene carbonate.
Take place for fear of such problem, usually the carbon dioxide that must removing contains the raw material alkylene oxide in a large number, yet this can cause the loss of feed carbon dioxide gas and the loss of raw material alkylene oxide, but also is necessary to enlarge the treatment unit of removing gas, and this is disadvantageous economically.
As carbon dioxide being purified to high-purity method, known for example have, the low-temperature distillation method, but this method needs lot of energy, therefore, a large amount of can make the carbon dioxide that raw material uses industrial for obtaining, this method almost can not become a kind of suitable method.
Therefore, the object of the present invention is to provide a kind of carbon dioxide that produces as by product when using ethylene oxidation reactions to produce oxyethane, as the method for raw material production high quality alkylene carbonate.
Specific embodiments
With reference to embodiment of the present invention the present invention is explained below.
[production of oxyethane]
The catalytic vapor phase oxidation that oxyethane generally is to use silver catalyst to pass through ethene is produced.In this method, as in Liv Ullmann technical chemistry complete works, the 5th edition, volume A10, the 117th page of (UllmannsEncyclopedia of Industrial Chemistry 5th Ed., Vol.A10, P.117ff.,) described in, make and mainly contain ethene, oxygen and as the unstripped gas of the methane of carrier gas, flow through fill silver catalyst multitubular reactor to finish reaction.Ethene is approximately 80% to the selectivity of oxyethane, and remaining about 20% ethene by complete oxidation, is made carbon dioxide and water.The oxidizing reaction gas of discharging from reactor comprises the oxyethane of generation, unreacted ethene, carbon dioxide, oxygen, carrier gas etc.Use water as ethylene oxide absorption that absorbent solution makes generation and enter liquid phase in the resorber.Absorb the oxyethane stripping in ethylene in the absorbent solution, reclaim from the aqueous solution of cat head as high density then, the refining product that becomes again further dewaters in distillation tower.Can use product oxyethane as the raw material of producing alkylene carbonate according to method of the present invention.
[recovery of carbon dioxide]
Remove system's (carbon dioxide gas recovery apparatus) absorbing all or part of carbon dioxide of delivering to of oxidizing reaction waste gas that produces behind the oxyethane.
According to Liv Ullmann technical chemistry complete works, the 5th edition, volume A10, the 124th page (UllmannsEncyclopedia of Industrial Chemistry 5th Ed., Vol.A10, P.124ff.,), oxidizing reaction waste gas contains the ethene of the 15~40vol% that has an appointment, and the methane of 1~60vol% and the carbon dioxide of 5~15vol% are although gaseous fraction changes slightly according to the operational condition of equipment.
Carbon dioxide is removed system's (carbon dioxide gas recovery apparatus) and is comprised carbon dioxide resorber, elementary stripper plant and carbon dioxide stripping tower.
Deliver to carbon dioxide and remove the oxidizing reaction waste gas of system, at first import the bottom of carbon dioxide resorber, the carbon dioxide absorption liquid of the aqueous solution by the carbon dioxide containing gas absorption agent is cleaned again, and the most of carbon dioxide in the waste gas is removed thus.As carbon dioxide absorption agent, can enumerate, for example alkaline carbonate such as salt of wormwood, alkanolamine such as diisopropanolamine (DIPA) and amino acid an alkali metal salt, wherein salt of wormwood is particularly preferred.In above-mentioned clean,, also can be dissolved in the absorbent solution slightly with carbon dioxide as the ethene of raw material use and the methane that uses as carrier gas.The oxidizing reaction waste gas that the carbon dioxide gas body burden reduces is discharged from cat head, and removes the oxidizing reaction waste gas of system and mixes with not being sent to carbonic acid gas, after the oxygen and ethene of supplying consumption, sends into oxidation reactor as the oxidizing reaction raw material once more.
The carbon dioxide resorber is at the high pressure that is generally 1.0~2.5MPa, preferred 1.5~2.2MPa, and temperature is generally 30~150 ℃, is preferably and operates under 60~120 ℃.The type that is used for carbon dioxide resorber of the present invention has no particular limits, or uses tray column, or the use packed tower all is possible.Density of carbon dioxide gas from the carbon dioxide absorption liquid that the absorption unit of dioxide carbon bottom is obtained owing to depend on the type of absorption liquid and the service temperature of resorber, can not give clear and definite regulation, yet usually at 3~20wt%.
The carbon dioxide absorption liquid that has absorbed carbon dioxide is sent to elementary stripper plant.As mentioned above, because absorption liquid contains the ethene and the methane of tracer level, to such an extent as to if when this solution is directly handled through the carbon dioxide stripping, ethene and methane can mix in the carbon dioxide of the recovery of purity drop.In elementary stripper plant, partially absorb gas in the carbon dioxide absorption liquid at stripping before the stripping all gas, reduce the lower-boiling impurity gas that is dissolved in the carbon dioxide absorption liquid such as the concentration of hydro carbons whereby.Structure as elementary stripper plant, though might use packed tower or tray column, special distillation tower need be installed, and concerning using simple vacuum flasher, generally be enough, because the solubleness of methane and ethene is far below the solubleness of carbon dioxide.In order to promote stripping, reboiler can be housed.Owing to contain ethene and methane by elementary steam stripped stripping gas, preferably be recycled to oxyethane recovery system (resorber) or ethylene gas phase oxidation step.
Elementary stripper plant 50~150 ℃ of temperature, preferred 95~120 ℃, is operated under pressure 0.1~1.0MPa, the preferred 0.1~0.5MPa usually.When adopting this operation,, thereby make the purity of the carbon dioxide that reclaims from the carbon dioxide stripping tower be not enough to be used for producing alkylene carbonate if when steam stripped gas volume was not enough, then removing of hydrocarbon can not be carried out fully.Simple raising stripping speed also is unfavorable, because this can cause the decline of process efficiency.
In the present invention, be necessary to make finally the purity of the carbon dioxide that reclaims from the carbon dioxide stripping tower be not less than 99.5vol%, preferably be not less than 99.6vol%, more preferably be not less than 99.7%, yet described purity is actually by the hydro carbons removal degree decision of handling by means of the stripping in elementary stripper plant.When control stripping operation so that make stripping amount (A) in the elementary stripper plant, with described stripping amount in elementary stripper plant with from the ratio of the total amount (B) of the carbon dioxide gas scale of construction of carbon dioxide stripping tower recovered overhead (total amount (B) (total amount equal substantially absorbed the carbon dioxide resorber gas volume) (ratio, B/A, stripping rate in the hereinafter referred to as elementary stripper plant), generally will be not less than 2%, preferably be not less than 2.5%, more preferably be not less than 3% o'clock, can obtain good result usually.Yet if the stripping rate is too high, although the purity of carbon dioxide raises, the efficient of carbon dioxide removal process generally speaking reduces.Therefore, the upper limit of stripping rate is set in 10% usually.
The carbon dioxide absorption liquid of discharging from elementary stripper plant is sent into the carbon dioxide stripping tower.This carbon dioxide stripping tower is designed to be fit to abundant stripping and goes out to be dissolved in whole carbon dioxides in the carbon dioxide absorption liquid.The structure type that is used for the present invention's carbon dioxide stripping tower with regard to steam stripping efficiency, is preferably used packed tower or tray column.Stripping preferably is equipped with reboiler or steam is blown into system in the tower in the bottom of carbon dioxide stripping tower, perhaps these two kinds of system in combination are got up to carry out hot stripping.
Stripping in the carbon dioxide stripping tower handles, and normally carries out under the used pressure of elementary stripping being equal to or less than, and preferably be not more than 0.3MPa, and its temperature is generally 50~150 ℃, preferred 80~120 ℃.The carbon dioxide absorption liquid is imported the carbon dioxide stripping tower from its cat head, and heat by heat exchanger or other device, the carbon dioxide of absorption is discharged in the bottom of tower.If necessary, can be blown into that solution carries out stripping to steam so that quicken stripping.
Make the carbon dioxide absorption liquid carry out stripping in the carbon dioxide stripping tower and handle, the carbon dioxide of absorption discharges in tower, makes solution obtain regeneration thus, is re-used as the carbon dioxide absorption liquid and returns in the carbon dioxide resorber.
The high-purity carbon dioxide gas that reclaims from process for ethylene oxide production in a manner described has the enough purity that is suitable as production alkylene carbonate raw material, can be used in this purposes.
[production of alkylene carbonate]
Make the carbon dioxide and the alkylene oxide reaction that from process for ethylene oxide production, reclaim in a manner described, produce alkylene carbonate.
Form catalyst for reaction as alkylene carbonate, can use known catalyzer, for example, halogenide (the U.S. patent 2 of alkali-metal bromide or iodide (Japanese patent laid-open publication gazette (KOKOKU) 38-23175 number), alkaline-earth metal, 667, No. 497), alkylamine, quaternary ammonium salt (U.S. patent 2,773, No. 070), organotin, organic germanium or tellurium compound (Japanese Patent open (KOKAI) 57-183784 number) and halo organophosphorated salt (Japanese Patent open (KOKAI) number 58-126884 number).In these compounds, with regard to active and selectivity, alkali metal halide such as Potassium Bromide and potassiumiodide and halogenated organophosphorated salt are preferred.
As the reactor of producing alkylene carbonate, the combination that is installed in series (the Springmann ∷ Fette Seifen Anstrichemittl of multitubular reactor and condenser has been proposed, Vol.73, pp.396-399,1971), ring-like reactor (Peppel:Industrial and Engineering, Vol.50, pp.767-770,1958), bubble-cap tower reactor (Japanese Patent open (KOKAI) 6-345699 number).Any described device can use, but the bubble-column reactor with outer circulation is particularly preferred, because it is supplied with and prevent that because of cooling causes the uncontrolled reaction aspect be superior to the diffusion of liquid phase carbon dioxide.
Because above-mentioned reaction is thermopositive reaction, so temperature of reaction can be controlled by the removal of heat.Temperature of reaction although change according to used catalyzer, is generally 80~200 ℃, preferred 100~180 ℃.
The speed that alkylene carbonate forms reaction is that therefore, the pressure when reaction is carried out is preferably high as much as possible by the branch pressure-controlled of making the carbon dioxide that raw material uses.Yet the rising of reaction pressure must require withstand voltage corresponding raising with reactor and relevant devices, thereby cause the raising of cost of equipment.The preferable range of reaction pressure is generally 1~10MPa, preferred 1~5MPa.
The carbon dioxide gas scale of construction of supply response device is generally 1~20 times of molar weight of the oxyethylene of supply response device.Carbon dioxide not only can be used as raw material, and can also play the function that side reaction takes place for component distribution that prevention causes because of the stirring of solution in the reactor and heat distribution, causes the carbon dioxide gas scale of construction of supply to surpass the necessary amount of reaction.In order to prevent that by product low-boiling point material and impurity from accumulating and circulation Returning reactor usefulness again in feed carbon dioxide gas, the unreacted that part is removed and the carbon dioxide of remainder.In the checked for impurities semi-invariant, control is removed.The removing amount of clear gas, the flow velocity based on the carbon dioxide of recirculation is generally 0.1~8%, preferred 0.2~5%.
If bring the impurity level of alkylene carbonate production process into when big, can make such impurities accumulation, make troubles to reaction.Although the accumulation of impurity itself is irrefragable to the influence of reaction, more seriously, accumulation strengthens owing to causing the effect that the relative reduction of carbon dioxide dividing potential drop causes main reaction speed to descend.This causes reacting the prolongation of required time and the decline of productivity and quality product.
The reduction of relevant carbon dioxide dividing potential drop, can be from keeping dividing potential drop by improving clearance rate, but this can cause the carbon dioxide that uses as raw material and the loss of alkylene oxide, but also needs to enlarge in proportion to remove gas processing device etc., causes economically unfavorable.Can in the solubility range that allows, consider the productive rate of expectation, use the catalyzer of proper concn according to the activity of catalyst system therefor.Catalyzer is with solvent supply response device, and separate with the alkylene carbonate that produces the reaction back, replenishes insufficient fresh feed more on demand, and circulation is back to reactor and uses.As solvent, wishing to use for purpose product alkylene carbonate is easy and The suitable solvent.
Had enough purity with the alkylene carbonate of catalyst separating, yet, can further make with extra care it by common vacuum distilling system etc. on request in order to reach higher purity.
Illustrated in further detail with reference to embodiment implementing the solution of the present invention, but should be understood that the following example only to be used for explanation and do not constitute limitation of the scope of the invention.
Embodiment 1
Use the production equipment of schedule of operation shown in Figure 1 to react.
(1) reclaims CO from oxyethane (EO) production stage
2:
In following explanation, the flow velocity of material is to import CO
2The weight flow velocity of the oxidizing reaction waste gas in the resorber 1 is represented as 1 weight part.
Reclaiming the oxidizing reaction waste gas (CO that stays behind the oxyethane in the ethylene oxidation reactions gas that obtains in the ethylene catalyst gaseous oxidation step of using silver catalyst
2Concentration: 6vol%, CH
4Concentration: 57vol%, C
2H
4Concentration: 24vol%) 1 weight part imports to through pipeline L1 and to have 3 theoretical plate numbers and at pressure 1.7MPa and temperature is 110 ℃ of down carbon dioxide (CO of operation
2) bottom of resorber 1.From CO
2The top of resorber 1 is through the salt of wormwood (K of pipeline L4 importing as absorption liquid
2CO
3) aqueous solution 7 weight parts.
Having absorbed CO
2Absorption liquid, import to 0.15MPa and 107 ℃ down in the elementary stripper plant (flashing tower) 2 of operation through pipeline L3.After handle reducing hydrocarbon concentration, solution supplied with through pipeline L7 have 5 theoretical plate numbers and at 0.1MPa and the 110 ℃ carbon dioxide (CO of operation down by stripping
2) top of stripping tower 3, CO
2By stripping with reclaimed.In this operation, the gas volume that discharges through pipeline L6 from flashing tower 2 be equivalent to the gas volume that discharges from flashing tower 2 and through pipeline L8 from CO
2The CO that stripping tower 3 reclaims
25.0% (stripping rate: 5.0%) of the summation of amount.
CO by compressor (not shown) compression recovery
2And through pipeline L8 supply carbonic ether formation reactor 4.
Mensuration is contained in the CO of recovery
2In hydrocarbon concentration, found that CH
4Amount be 0.03vol%, and C
2H
4Amount be 0.06vol% (both all calculate by the water of getting rid of), according to this result, can determine CO
2Purity be 99.91vol%.
(2) alkylene carbonate (EC) forms reaction:
In following explanation, the flow velocity of material, is represented as benchmark as 1 weight part with the weight flow velocity of oxyethane.
EC forms the CO that reaction is to use described recovery
2Carry out.The CO of the recovery of the oxyethane (from pipeline L9) of 1 weight part that obtains from ethylene oxidation reactions and 8.2 weight parts
2(from pipeline L8) imports the bottom that the bubble-plate column carbonic ether forms reactor 4.Liquor kalii iodide 0.01 weight part is dissolved in carbonic acid (1,2)-ethyl 0.01 weight part, supplies with as catalyzer (from pipeline L10).Reaction solution is discharged through pipeline L11 with the gas from bubble-column reactor 4 tops, is directed at gas-liquid separator 5, is separated into gas and liquid.Total points is cleared out of system from 0.5% of gas through pipeline L13, and residuum is through pipeline L12, with described steam stripped CO
2After (from pipeline 8) compressed machine (not shown) is mixed, be recycled to EC and form reactor 4.The part of the liquid after the separation (L15) is taken out as product from pipeline L14, and after residuum removes heat by heat exchanger 6, is recycled to the bottom that EC forms reactor 4.The condition of controlling reactor is 180 ℃ and 2PMa.
When operating continuously under these conditions, therefore remaining hydrocarbon constant concentration makes stable operation become possibility at about 4vol% in reactor 4.The reaction solution that reclaims from pipeline L14 makes the alkylene carbonate evaporation under 4KPa and 138 ℃, thus separating catalyst and obtain alkylene carbonate.
Comparative example 1
Preparation is as the CO of unstripped gas
2, its purity is the 98.9vol% (CH that contains 0.37vol% as impurity
4C with 0.74vol%
2H
4).
Except using the CO of above-mentioned preparation
2Form reaction by carrying out EC outward, with embodiment 1 same procedure.When adopting operate continuously,, cause CO because the hydrocarbon concentration in the circulation gas raises
2The corresponding reduction of concentration, hydrocarbon concentration finally reaches 24vol%.Because observed the decline of EO transformation efficiency, make and reach constant so will control the feed rate of raw material.Coloured by the alkylene carbonate that catalyzer and separating of reaction soln obtain, can think that this is that the existence of by product aldehyde cpd causes.
Comparative example 2
Except the clearance rate of circulation gas becomes 10% to keep the CO in the operate continuously by 0.5%
2Beyond the dividing potential drop, undertaken by same program with comparative example 1 regulation.CO
2Concentration remain on 96%, and the quality of product E C is identical with the cardinal principle of embodiment 1, but the EC that removes amount has improved about 10 times.