US2392316A - Oxidation process - Google Patents

Description

Jan. 8,v 1946. c; DREYFUS 'l OXIDATION PROCESS Filed sept. 5, 1942 (INVENTOR.

mm .mn b f b Imm SEIU Zorro/um .mufcmnm s mv Emmen? m mm om K mm Nm kCamille DrjeHf-us BY\ 9 ATfroRNEY'Sv Patented Jan. 8, 1946 UNITED STATES PATENT OFFICE oxmnrrofn mtoenss Camille Dreyfus, New York, N. Y. Application September 5, 1942, Serial No. 457,381 1 Clam. (ci. lzoo- 533) This invention 'relates tothe oxidation 'of hydrocarbons and relates more particularly 'to the Aoxidation of unsaturated hydrocarbons. 1

An lobject of rnyinyention is to oxidize unsaturated hydrocarbons to produce valuable oxygen- 1 trial heating media `since the gaseous combustion f vreaction may 'be leasily and accurately controlled. While the gas mixtures are valuable las heating media, they Aareeven more valuable as a raw material for the manufacture of -various oxygenu,

1ated organic compounds.

I have now discovered lthat unsaturated aliphatic `gaseous hydrocarbons may be oxidized at' elevated temperatures zand pressures Zwith Tree oxygen to yield valuable foxygenatedorganic compounds. "The products which may 'be obtained in Vaccordance ywith vmy invention are, "for example, ethylene oxide, acetaldehyde, ethyl falcohol, acetic acid, formaldehyde, methyl 'alcohol, acetone and Ahigher =ketones and alcohols.

`The gaseous mixtures containing Aunsaturated aliphatic gaseous hydrocarbons vremployed in accordance with `my -no'vel process may b obtained from any suitable source. Preferably, the `gaseous mixtures employed are those obtainable 5by cracking saturated lhydrocarbons and 1mixtures of said hydrocarbons, Jeither 1in the liquid or vapor phase, which produces a mixture oi gases vpredominantly unsaturated in character, containing substantial quantities of ethylene vand higher iunsaturated aliphatic hydrocarbons. 'The charging Astock supplied to the cracking unit lmaybe either liquid or gaseous infcharacter. 'The conditions of 4operation-in rthe cracking unit may be vared'to handle the diierent Itypes of charging Ystock and to crack them vto maximum yields of unsaturated aliphatic hydrocarbon gases. :The cracking unit may operate at temperatures fof from 1000 to 2000'-F. and thepressure mayrange ,from subatmospheric pressures of from yabout d. vpound per 'square inch wabsolute to "super-atmos- -pheric pressures of 15 to 200 pounds per square inch absolute.

vIn carrying out the oxidation of the gaseous unsaturated aliphatic hydrocarbons, ;Eree oxygen may be employed. y Preferably, I employ air as the source of oxygen Ialthough any mixture com prisi-ng oxygen and .suitable inert diluents vxis suitable. The oxidation reaction may be 4carried out at temperatures of from 400v to 800 F. while the pressure employed maybe fromslightly above atmospheric pressure to pressures of `500 pounds per square 'inc-h gauge.

For the oxidation reaction, the ratio Iof roxy,- lgen employed -to the `volume yof gaseous unsaturated hydrocarbon employed, Jmay wary. .Satis- Afacto-ry results Amay be' Aobtained if, for each wolume of lgaseous hydrocarbon added -to thesys tem, there are added from 3 to ll0 -Vrvolumes of air While lat the `same time from 20 'to 80 Volumesof unreacted hydrocarbon gas are recycled. Op-y timum results are obtained Whenthere are added to the -systemabout 7 volumes of air lfor each -vol `urne of gaseous 'hydrocarbon and 50 "volumes of lgaseous hydrocarbons are recycled.

After the oxidation reaction the oxygenated products, together with the 11n-reacted gases, are passed -to an absorption system wherein the oxygenated products are separated. The absorption #system also -may voperate under pressure. =The unreacted hydrocarbon gases are removed 4lrom the ga-ses 'which remain and are recycled to the 'oxidation zone. -The nitrogen, carbon monoxide, carbon dioxide and oxygen `which remain :after reiriovalfof the hydrocarbon gases are then-#vented 'to the atmosphere.

AThe Aprocess -of my invention will V-now lbe-described with're'ference to the accompanyingfdrawing.

`The vcharge stock, which is cracked to yield the gaseous `-mixture `of unsaturated aliphatic hydrocarbons, is caused to `enter Lthe system through a line l. The Lstock fis forced in under the desired pressure bya pump! 2 `which --may be -either -a liquid pump or a gas compressor, vde'penizling upon `Whether or |not the charging rstock is liciu'id 'vor gaseous 4'in nature. When l'the cracking unit is loperated under sub-atmospheric pressures, `the pump xmay-be 4eliminated for ibyepassed. 4From pump'2, the chargingstocklis passed through :a line s3 tothe Vcracking furnace 4 -where it lenters coils t'5 and-6 and is #heated ito cracking temperature. The vcracking temperature zwill :vary der pending -upon the naturefof the scharging stock.

From 'the lfurnace, the v`cracked mixture r-itlows throughaline -1 to a fractionating ftower matter having been quenched by a portion of the resid` ual product from the bottom of the fractionating tower 8. The quenching liquid is drawn through a line 9 and forcedby a pump Ill through a cooler II and into line 1. This quenching operation serves to arrest the cracking reaction and to reduce the temperature at the base of the fracl Y. tionati-ng tower. Heavier residual liquid products formed Vin the cracking operation are removed from the baseof thetower through line I2v which is providedwith 'a valve I3. The cracked gaseous mixture passes' overhead from the tower through line I4, enters a condenser I5 and is collected in a receiver I6. A portion 'of this gaseous mixture condenses and accumulates at the base of rel, ceiver I6. This liquid Vis returned to the top of the fractionating tower as a reux mediumv through pump I1 and line lI8. Any excessliquid j condensation product accumulating in the ,re` ceiver I6 may be removed from the systemy V.through line I9 which isprovided with avalve 20.

This excess liquid may be returned to vthe charg-` ing .stock andY recycled through r the process to AHThe cracking unit may operate under sub-atmospheric or super-atmospheric pressures. Whengoperating under vsuper-atmospheric pres- 'surethe pressure'r is controlled by valve 2| with Vvalve 22 closed and valve A23 open. When opering zone lfor further vcracking by meansof a compressorj21l through lines 2,84 and V429 in order to increasethe proportion of unsaturated hydro-v carbonsin the gases.V Y

' 'Phe-gaseous mixture ofk unsaturated aliphatic hydrocarbonsfrom holder l26 is charged tothe oxidizing section through line30 by means of a dizingwzone On the upstream side ofthe prescompressor 3I which compresses the gas frornithe gas holder pressure'to therhigher operating p ressure required4 inthe oxidizing section. The charge ofgasis joined byv recycle gas which enters through a line 32. Air is forced into the mixed gases inline by a compressor 33, the air entering through a line 34. The mixture of charge gas, cycle gas, and airV is then passed to4 the furnaceg35. where itenters coils 36 and is brought lupto optimum reaction temperature. The oxidizing reaction is continued inthe reactionchamber 31 located just beyond the furnace discharge. rThe Yreaction chamber 31 is so designed as to provide a variable' volume and in this wayY the reaction time may be controlled.V The smaller theY volume provided, the Yshorter will be the Areaction period since, with a given volumetric velocity, the reacting gases will pass through y the reaction chamber after being subj'ectedto the reaction conditions for only a relatively short period-,of time. ,The greater the volume provided, with the same volumetric velocity, the longer will be lthe reaction time, due to the more extended period during which the 4reacting gases are subjected tov reaction conditions. As the hoil gas mixture leaves the. reaction,r chamber, it is quenched .bythe injection. of cold liquid at 3 8 Y throughjline .39v andthe whole mixture Vis cooled in a cooler 40 andy ows through a line 4I to a separator42. A portion of ithellquid condensate Vis returned through al line 43 by-a'pump 44 to enter at 38 and to quench the hot gases leaving the reaction chamber 31. Y

The reaction chamber of variable volume may comprise a reactor containing a movable piston which is adjustable so that the volume of the reaction chamber may be increasedor decreased.

A variable effective volume may also be obtained f of Vthe reaction chamber may be. varied. If, for example, the discharge port furthest from the inlet is opened and the others closed, the reactclosest to the inlet is opened and the remainder closedrthe reacting gases will be in the reaction chamber foronly a relatively limited period and the reaction .time will be quiteshort. n'

The liquefied portion of the products in separator Y42 is withdrawnl through a line 45 provided with a valve 46 and directed to a recovery stage (not shown). This product contains formaldehyde and a small 'amount Vof recoverable volatile products in water solution. The volatile products are removed fromV this solution and the formaldehyde may be concentrated to a suitable concentration of commercial utility.

The gaseous portion of the oxidized products leavesseparator 42 through line 41 yand enters an absorber 48 whereV the water-soluble components are absorbed in waterrentering the top of the absorber through line 49. 4'The absorber is operated under a pressure of, for example, pounds per square inch. This pressure vis controlled by the pressure control *valve V50.. lI'fhis valve-likewise controls the pressure on the oxisurercontrol valve 50, a portion of the gas which is unabsorbed is recycled through line 5I, booster the Water-soluble products dissolved therein, is

removedfrom the base of the'rabsorberthroilgh line 53v and valve 54 and is passed' through a heat interchanger 55 and then through a line 56 `into a recovery still 51 for recovery of the volatile products. Stillv51 operates atsubstantially atmospheric pressure.` i The volatile, water-soluble ,products are distilled overheadY through a line 58 and a condenser 59'ar1d collected in the receiver 60. A portion of the vcondensate iromvrthe receiver 60 is returned to the top of the tower for reiiux medium throuh pump 6I and line 62.` Still .51 maybe heated .by any conventional means such as by a steam heating coil. I3.`y A portion of the stripped aqueousresiduefrom the base'of the still is returned byline 64 andr pump.l 65 through heat exchanger 55 and cooler 66.1t`o'the absorber 48'to be used for absorbing more watersolublev products. VExcessstripped watery is removed from the still through line- 61 which is provided with a valve 68. The condensed Ap'rodf uct collected in receiver L6I) is a mixtureof ,ethf ylene oxide, acetaldehyde, ethyl alcohol,Y acetic acid, methyl alcohol,iacetone,and higher alcohols and Aketones, and this mixture is'directed through a line69ftora purication' stage (not shown), where the mixturelmay belseparated intofuseveral individual components in 'anysitablemanner. Y :f as

through pressure control valve 50 contains unconverted hydrocarbon gases, together with nitrogen, carbon monoxide, carbon dioxide and a small amount of oxygen remaining from the air injected into the system. This gas passes through a line 1D to a gas absorption unit. This unit comprises an absorber 1| and a still 12. The entering gas flows upward and counter-current to the downward flow of absorber oil which enters the top of the absorber through line 13. The desired pressure is maintained on the absorber 1| by a pressure control Valve 14 and is held at a point somewhat below the operating pressure in the absorber 48 in order to permit ow of the gas through line to absorber 1|. The downward flowing absorber oil absorbs the hydrocarbon gases. The remaining gas, free of hydrocarbon constituents,l leaves absorber 1| through a vent pipe 15 and is discharged to the atmosphere.

The absorber oil containing the absorbedhydrocarbon gases is discharged from the base of the absorber 1| through line 16 and is forced by a pump |1 through lheat exchanger 18, a preheater 19 and a line 80 into recovery still 12. In this still the dissolved hydrocarbon gases are distilled overhead through linev 8| and enter a condenser 82 where they are cooled and partially liquefied. The partially liquefied product enters a receiver 83 for collection and separation. The temperature of condenser 82 is adjusted so that only that amount of liquid required for reiiux in still 12 is condensed. This liqueed portion is returned as reux to the top of still 12 by a pump 84 through line 85. The balance of the recovered hydrocarbons are discharged as a gaseous mixture through pressure controller 86 and are recirculated to the furnace 35 through line 81. The pressure on still 12 is maintained at a point high enough to return the hydrocarbon gas mixture from receiver 83 back to the oxidizing furnace under its own pressure.

Recovery still 12 may be heated by any convenient means such as a steam coil 88. 'I'he stripped absorption oil is then returned to the top of the absorption tower by a pump 89 through lines 90 and 9|. The oil passes through heat exchanger 18 and a cooler 92 and enters the top of absorber 1| through line 13. Fresh absorber oil may be supplied to the system through a line 93.

The operation of my novel process is relatively simple and produces excellent yields of oxygenated products without the formation of excessive amounts of tar and other products such as carbon monoxide and carbon dioxide.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

Process for the production of oxygenated organic compounds, which comprises mixing one volume of a gaseous unsaturated aliphatic hydrocarbon with about 7 volumes of air and adding to said mixture about volumes of anhydrous unreacted gaseous unsaturated aliphatic hydrocarbon recycle, heating the anhydrous mixture to a temperature of 400 to 800 F. while under a superatmospheric pressure of not more than 5'00 pounds per square inch, passing said reacting mixture to a Vcatalyst-free reaction zone, allowing. the reaction to continue therein to form oxygenated organic compounds, condensing the mixture of gases formed and injecting a portion of the condensate into the gaseous mixture leaving the reaction zone to halt further oxygenation.

CAMILLE DREYFUS,

Nef

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