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Office europeen des brevets (fi) Publication number : 0 569 248 A2

@ EUROPEAN PATENT APPLICATION

@ Application number : 93303549.5 @ Int. CI.5: C07D 301/19, C07D 301/22

(22) Date of filing : 07.05.93

(30) Priority : 08.05.92 US 880836 @ Inventor : Dubner, Walter S. P O Box 1737 Wilmington, Delaware 19899 (US) @ Date of publication of application : 10.11.93 Bulletin 93/45 (74) Representative : Cropp, John Anthony David MATHYS & SQUIRE 10 Fleet Street @) Designated Contracting States : London, EC4Y 1AY (GB) BE DE FR GB IT NL

(7i) Applicant : ARCO Chemical Technology, LP. 3 Christina Centre, Suite 902, 201 N. Walnut Street Wilmington, Delaware 19801 (US)

(54) Improved process for the co-production of propylene oxide and monomer.

(57) In the co-production of propylene oxide and styrene monomer, there is produced a sodium-containing heavy residue stream previ- ously suitable only as a low grade fuel. In accordance with the invention, the heavy resi- due stream is contacted with aqueous acid, and the resulting mixture is phase separated into an aqueous sodium-containing phase and an organic phase reduced in sodium, and at least a portion of the organic phase reduced in sodium is converted to styrene monomer.

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UJ Jouve, 18, rue Saint-Denis, 75001 PARIS 1 EP 0 569 248 A2 2

Background of the Invention form a practice of the invention.

Field of the Invention Detailed Description

The present invention relates to an improved 5 In a first reaction step, ethyl benzene is reacted process for the co-production of propylene oxide and with molecular oxygen at elevated temperature in ac- styrene monomer and especially to improved recov- cordance with known techniques to form ethyl ben- ery of valuable 1-phenyl and styrene from zene hydroperoxide. U.S. Patent 4,066,706 provides heavy residual process streams by acid treatment and a comprehensive description of this reaction. cracking. 10 Suitably, a small amount of alkali is incorporated in the oxidation mixture as provided in U.S. Patent Description of the Prior Art 4,262,143 in order to improve oxidation rate and se- lectivity. An extremely successful process for the co-produc- Ethyl benzene hydroperoxide is reacted with pro- tion of propylene oxide and styrene monomer in- is pylene to form propylene oxide and 1-phenyl ethanol. volves the molecular oxygen oxidation of ethyl ben- U.S. Patent 3,351,635 describes suitable conditions zene to form ethyl benzene hydroperoxide, the cata- and catalysts for this reaction. lytic reaction of the hydroperoxide with propylene to The epoxidation reaction mixture is generally form propylene oxide and 1-phenyl ethanol, and the caustic washed and subjected to a series of distilla- dehydration of the 1-phenyl ethanol to styrene mono- 20 tions in orderto separate materials contained therein. mer. The basic patent describing this process is U.S. Generally, the reaction mixture is first distilled to sep- Patent 3,351,635. arate unreacted propylene overhead from heavier In practice of the process, various distillation components. The separated propylene is convenient- steps are employed in orderto separate unreacted re- ly recycled to the epoxidation step. agents as well as various product streams, and gen- 25 The heavier components are then further distilled erally one or more caustic treatment steps are em- after caustic wash in a series of distillations to sepa- ployed in order to reduce the acidic characteristics of rate unreacted ethyl benzene which can be recycled, various streams. preferably after a caustic wash as described in U.S. In commercial practice of the propylene oxide- Patent 3,439,001 , product propylene oxide, and prod- styrene monomer process there is formed a heavy re- 30 uct 1-phenyl ethanol leaving a heavy organic sodium- sidue stream containing, as a result of one or more containing low value product stream. caustic treatments, relatively high levels of sodium The 1-phenyl ethanol stream is dehydrated to compounds. Heretofore, such heavy residue has product styrene monomer in accordance with known comprised a low value product stream suitable only procedures such as described in U.S. Patent for use as a low grade fuel. 35 3,351,635. In accordance with the present invention, the so- Brief Description of the Invention dium-containing low value organic product stream is treated in order to upgrade the stream and to recover In accordance with the present invention, a proc- valuable products therefrom. ess is provided whereby the low value product stream 40 In one embodiment, the lowvalue product stream is upgraded and valuable products are recovered is thoroughly admixed with aqueous acid, preferably therefrom. The process of the invention involves sulfuric acid, at relatively mild conditions, eg. 20- treating the low value stream with aqueous acid and 100°C, preferably 40-90°C. The resulting mixture is phase separating the resulting mixture into an aqu- separated into immiscible phases, specifically an eous phase containing most of the sodium previously 45 aqueous sodium-containing phase and an organic associated with the low value stream and an organic phase having reduced sodium content. stream phase having reduced sodium content. The re- The organic phase has added thereto a compat- sulting organic stream phase can be directly cracked ible acid catalyst such as p-toluene sulfonic acid and at elevated temperature with the formation of 1-phe- the resulting mixture is cracked at elevated tempera- nyl ethanol and styrene or the organic stream phase 50 ture to form 1-phenyl ethanol and styrene monomer can be passed to a wiped film evaporator where a vol- which products can be separated by distillation from atile stream is separated and cracked to form 1-phe- remaining heavy materials. Conditions for the crack- nyl ethanol and styrene, the heavy stream from the ing include temperatures of 70°C to 300°C, preferably evaporator comprising a useful fuel. 120°C to 220°C and pressures below atmospheric, 55 eg. 100-400m.m.Hg.whichareappropriateforvapor- Description of the Drawing ization of light materials. Product 1-phenyl ethanol and styrene monomer The attached drawing illustrates in schematic from the cracking represent increased yields of de- 2 3 EP 0 569 248 A2 4 sired products of the overall process. Also, the heavy cled to oxidation zone 1 . materials from the cracking are useful as fuel. The bottoms stream from zone 1 1 comprised of 1 - In another , more preferred practice of the inven- phenyl ethanol, and heavies passes tion, the organic phase from the acid treatment is sub- 5 via line 13 to distillation zone 14. The overhead frac- jected to a wiped film evaporation in order to separate tion from zone 14 comprised of 1-phenyl ethanol and up to about 40% by weight of the stream as volatile acetophenone is separated via line 15 and passed to overhead fraction. It has been found that this over- dehydration zone 16 wherein 1-phenyl ethanol is con- head fraction can be passed directly to the 1-phenyl verted to styrene monomer which is recovered via ethanol dehydration step employed in commercial 10 line 27. Unreacted acetophenone is separated and propylene oxide/styrene monomer processes where- passed to a zone (not shown) for con- in components of the volatile overhead are converted version of acetophenone to 1-phenyl ethanol by to styrene monomer at the conditions conventionally known procedures, the 1-phenyl ethanol being recy- employed for the 1-phenyl ethanol dehydration. cled to zone 1 1 . The heavy bottoms from the wiped film evapora- 15 The bottoms stream from zone 14 passes via line tion is, itself, useful as an upgraded fuel by virtue of 1 7 to mixing zone 21 wherein it is mixed with aqueous the low sodium content thereof. sulfuric acid which is introduced via line 22. The acid employed in the heavy organic treat- The admixture from zone 21 passes via line 23 to ment is preferably sulfuric acid. Other less preferred decantation zone 24 wherein the immiscible phases acids are phosphoric acid, oxalic acid and the like. 20 are separated. The aqueous sodium-containing The acid is used in at least an amount sufficient phase is separated by means of line 25 and may be to react with all of the sodium in the heavy organic further treated or discarded. The organic phase sub- stream. In the case of sulfuric acid, sufficient acid is stantially reduced in sodium is removed via line 26 used to form sodium sulfate, ie. 1 mol of sulfuric acid and passes to wiped film evaporator 1 8 wherein up to per mol of contained sodium, and preferably at least 25 40% by weight of the stream is separated as a distil- 2 mols sulfuric acid per mol of sodium are employed late fraction via line 19. This fraction contains various sufficient to form sodium bisulfate. Where other acids 1-phenyl ethanol condensation products, some 1- are used, equivalent amounts are employed. phenyl ethanol, esters and the like. In this embodi- The invention can be described with reference to ment, the distillate fraction passes to dehydration accompanying Figure 1 which is a schematic repre- 30 zone 16 wherein components of the distillate are sentation of a practice of the process. cracked and/or dehydrated to provide supplemental is fed to reactor 1 via line 2 and styrene monomer values. The heavy bottoms from therein oxidized to ethylbenzene hydroperoxide by wiped film evaporator 18 is recovered via line 20 and reaction with molecular oxygen which is introduced represents an upgraded stream suitable as heavy via line 3. The reaction mixture from reactor 1 com- 35 fuel. prised of unreacted ethylbenzene, ethylbenzene hy- droperoxide, 1-phenyl ethanol, acetophenone and Example heavies passes via line 4 to epoxidation reactor 5 wherein the ethylbenzene hydroperoxide is catalyti- The following example, which is described with cally reacted with propylene introduced via line 6 to 40 reference to the accompanying drawing, illustrates form propylene oxide. the invention. The epoxidation reaction mixture is treated with Ethylbenzene is introduced into zone 1 via line 2 aqueous caustic to neutralize acidic materials and to at the rate of 2,680,000 Ibs./hr. and therein is reacted remove the epoxidation catalyst (not shown) and the with molecular oxygen introduced via line 3 at the rate treated epoxidation reaction mixture comprised of un- 45 of 50,000 Ibs./hr. Also contained with the molecular reacted propylene, propylene oxide, ethylbenzene, 1- oxygen are inerts, primarily nitrogen, in amount of phenyl ethanol, acetophenone and heavy materials 164,000 Ibs./hr. passes via line 7 to distillation zone 8. In distillation Oxidation conditions in reactor 1 are 135-145°C zone 8, an overhead mixture of unreacted propylene and 50-55 psig; residence time is 1.45 hr. and product propylene oxide is separated via line 9. so The liquid oxidation reaction mixture comprised This mixture is subsequently resolved (not shown) by weight of about 59% ethylbenzene (EB), 35% into an unreacted propylene fraction for recycle and ethylbenzene hydroperoxide (EBHP), 1.5% 1-phenyl product propylene oxide which is further purified by ethanol (MBA), 2.8% acetophenone (ACP) and 1.7% conventional means. others passes via line 4 at the rate of 467,000 Ibs./hr. A bottoms fraction comprised of ethyl benzene, 1 - 55 to epoxidation zone 5. Propylene is introduced into phenyl ethanol, acetophenone and heavies is re- zone 5 via line 6 at the rate of 580,000 lbs./hr. moved from zone 8 via line 10 and passes to distilla- In zone 5 propylene is catalytically reacted with tion zone 11. An overhead ethyl benzene stream is EBHP in the presence of 22 ppm as molybdenum of separated from zone 11 via line 12 and can be recy- soluble molybdenum compound catalyst at 95-115°C 3 5 EP 0 569 248 A2 6 and 600 psia, residence time being 1.7 hr. line 19. A heavies stream containing 130 ppm sodium The epoxidation reaction mixture passes from is recovered via line 20 at the rate of 4,900 Ibs./hr. and zone 5 via line 7 at the rate of 1,100,000 Ibs./hr. and comprises an upgraded heavy fuel. has a composition by weight of about 25% EB, 6% 5 The vapor mixture from wiped film evaporator 1 8 propylene oxide (PO), 48% propylene, 13% MBA, 2% mainly comprises oxygenated aryl compounds in- ACP and 6% others. The epoxidation reaction mixture cluding 1-phenyl ethanol , 1-phenyl ethanol, 1- is treated with aqueous NaOH (not shown) to neutral- phenyl ethanol and propylene oxide, condensation ize acidic materials and to remove the molybdenum products, esters and the like. This mixture is com- catalyst. The treated mixture is decanted to separate 10 bined with the MBA overhead from distillation column an aqueous phase containing sodium and molybde- 14, and the combined streams from zones 14 and 18 num compounds from the organic reaction mixture are reacted in dehydration and cracking zone 16 at which contains about 100-150 ppm Na by weight. The 200-230°C and 100-300 m.m.Hg. in the presence of mixture passes via line 7 to distillation zone 8 which 50-200 ppm para toluene sulfonic acid catalyst. The actually represents a plurality of columns wherein va- 15 styrene-containing reaction mixture is recovered via rious streams are separated by known means. Over- line 27 at the rate of 16,900 Ibs./hr. The composition head components are removed via line 9 and com- by weight of this stream is about 80% styrene, 5% prise 60,000 Ibs./hr. PO and 528,000 Ibs./hr. propy- MBA, 11% ACP and 4% others, and styrene is recov- lene along with 43,000 Ib./hr. of other light com- ered therefrom by conventional means. pounds which are treated by conventional means. 20 Through practice of this invention, styrene pro- Bottoms from zone 8 passes at the rate of duction is increased by about 0.8% which in a world 490,000 lbs./hr. via line 10 to distillation zone 11. scale unit producing a billion pounds of styrene per The bottoms stream in line 10 has a weight com- year represents $2 million added value at current position of about 57% EB, 35% MBA, 5% ACP and 3% styrene prices. Additionally, the upgraded heavy fuel others. The total sodium content this stream is about 25 is of considerably greater value than the high sodium 112-169 ppm. material produced by prior procedures. Unreacted EB is distilled overhead at the rate of 280,000 Ibs./hr. Bottoms from zone 11 is removed via line 13 at the rate of 204,000 Ibs./hr. and comprises Claims by weight about 83% MBA, 10% ACP and 7% others 30 which are mainly oxygenated aryl compounds. This 1 . A process for the co-production of propylene ox- bottoms stream contains about 275-410 ppm by ide and styrene monomer wherein ethylbenzene weight sodium. is oxidized to ethylbenzene hydroperoxide, said The bottoms stream from zone 11 passes via line hydroperoxide is reacted with propylene to form 13 to distillation zone 14 which actually comprises a 35 propylene oxide and 1-phenyl ethanol, unreacted plurality of separate columns. MBA and ACP are propylene, propylene oxide and 1-phenyl ethanol separated overhead by conventional means at the are separately recovered by distillation leaving a rate of 149,000 Ibs./hr. The composition by weight of heavy residue containing sodium and oxygen- the overhead stream is about 87% MBA, 11% ACP containing organic materials formed in the proc- and 2% others which are mainly oxygenated com- 40 ess, and the 1-phenyl ethanol is dehydrated to pounds. styrene monomer, characterised in that the said A heavy bottoms stream is removed from zone 14 heavy residue is admixed with aqueous acid, the via line 17 at the rate of 7,000 Ibs./hr. The heavies resulting admixture is phase separated into an stream is primarily comprised of oxygenated aryl aqueous sodium-containing phase and an organ- compounds with molecular weights greater than 45 ic phase having a reduced sodium content, and at 225g./mole and contains about 0.7 wt.% sodium. The least a portion of the organic phase having a re- heavy stream passes via line 17 to zone 21 wherein duced sodium content is converted to styrene it is admixed with 1,000 lbs./hr. of 22 wt.% aqueous monomer. sulfuric acid introduced via line 22. The mixture from zone 21 passes via line 23 to so 2. A process as claimed in claim 1 wherein the said decantation zone 24 where the mixture is separated aqueous acid is aqueous sulfuric acid. into aqueous and organic phases. An aqueous phase is separated via line 25 as a waste product stream 3. A process as claimed in claim 1 or claim 2 wherein containing 5.5 wt.% sodium. said organic phase having a reduced sodium con- The organic phase now containing only 40 ppm 55 tent is subjected to wiped film evaporation, up to sodium passes at the rate of 7,100 Ibs./hr. via line 26 40 wt.% volatiles are separated and cracked to to wiped film evaporator 18. From evaporator 18, a form styrene monomer. vapor stream is separated at 175°C and 50 m.m.Hg. and passes therefrom at the rate of 2,200 lbs./hr. via 4 EP 0 569 248 A2