Distillation Process for Recovery of Methyl Isobutyl Ketone

Distillation process for recovery of methyl isobutyl ketone US 4163696 A ZUSAMM!"ASSU!#  There is disclosed an azeotropic distillation process process for separating toluene from methyl isobutyl ketone (MIBK) in a spent liquor mixture ! toluene azeotrope former" preferably methanol" is added to the liquor in an amount su#cient to form an azeotrope $ith all of the toluene present in the mixture The methanol is added in an amount of at least about %&%" typically an excess amount of about ' to about &' parts by $eight of methanol per * part by $eight of toluene  The resulting azeotrope azeotrope of methanol and toluene is then separated separated by distillation from the MIBK The methanol may be subsequently reco+ered from the toluene by extraction $ith $ater ,ther toluene azeotrope formers may be utilized

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A!S(')*+(%) -hat is claimed is.  In a distillation process for separating a mixture of methyl isobutyl ketone (MIBK) and toluene" the impro+ement $hich comprises adding methanol to the mixture prior to distillation to form an azeotrope of toluene and methanol and then distilling the mixture to separate and reco+er one fraction of the MIBK and another fraction of said azeotrope % The process of claim  $herein at least about %&% parts by $eight $e ight of methanol is added per * part by $eight of toluene ' The process of claim  $herein the methanol is added to the spent liquor mixture in an amount at least su#cient to form an azeotrope $ith all of the toluene present in the mixture  The process of claim  $herein the methanol is added to the spent liquor mixture in excess of the amount su#cient to form an azeotrope $ith all of the toluene present in the mixture / The process of claim  $herein the methanol is added to the spent liquor mixture in an amount of from f rom about ' to about &' parts by $eight of methanol per * part by $eight of toluene & The process of any of claims " '"  / or % $herein the methanol is separated and reco+ered from the azeotrope by extraction $ith $ater

0 The process of claim / $herein all of the methanol" including the excess and the azeotrope amount" is reco+ered by extraction $ith $ater 1 !n azeotropic distillation process for separating a mixture of MIBK and toluene" $hich process comprises adding methanol to the mixture in an amount su#cient to form an azeotrope $ith all of the toluene present in the mixture and then distilling the mixture to separate the azeotrope and the MIBK 2 The process of claim 1 $herein the methanol is added to the spent liquor mixture in excess of the amount su#cient to form an azeotrope $ith all of the toluene present in the mixture * The process of claim 1 $herein the methanol is added to the mixture in an amount of from about ' to about &' parts by $eight of methanol per * part by $eight of toluene  The process of any of claims 1" 2 or * $herein the methanol is separated and reco+ered from the azeotrope by extraction $ith $ater % The process of claim 2 $herein all of the methanol" including the excess and the azeotrope amount" is reco+ered by extraction $ith $ater

$S*+'%$U!# 3I456,4789 ,: T;9 I<=9 by $eight MIBK" %> by $eight toluene" and %> by $eight ; % , requires a distillation column of at least /& theoretical plates and a re?ux ratio of %0 ;o$e+er" since the resulting o+erhead contains 112> by $eight toluene" &*&%> by $eight MIBK" and 22> by $eight ; % ," it is apparent that the separation of toluene from MIBK by simple distillation is not feasible 47MM!8@ ,: T;9 I<=9
!lso preferably" the process is one $herein the methanol or other toluene azeotrope former is added to the spent liquor mixture in an amount at least su#cient to form an azeotrope $ith all of the toluene present in the mixture 39458ICTI,< ,: T;9 38!-I by $eight MIBK" %> by $eight toluene" and %> by $eight $ater" the sol+ent is dehydrated $ith drying agents such as sodium hydroxide" sodium sulfate" silica gel" etc The dry sol+ent is then fed into a distillation column $ith about %/ parts by $eight of methanol per 21 parts by $eight of dry sol+ent TolueneEmethanol azeotrope along $ith excess methanol distills oF as o+erhead at a temperature of &*%G to &G 5 The boiling temperature diFerence bet$een the azeotrope and the MIBK is about /&G to /0G 5 This makes the separation of these streams easy and possible ! portion of the azeotrope is returned to the column as re?ux $hile the remaining liquid is further processed as described hereinafter -ith proper design and operation" about * to %* theoretical plates in the column and a re?ux ratio of about * to /" a good separation of at least 2/> by $eight of MIBK is feasible Methanol is reco+ered from the azeotrope by extraction $ith $ater Cure toluene is reco+ered by distilling the ra#nate $hile methanol is reco+ered by distilling the extract  The azeotrope former is added to the spent liquor mixture in an amount su#cient to form an azeotrope $ith all of the toluene in the mixture -ith methanol as the azeotrope former" the methanol is added in an amount of at least about %&% parts by $eight per * part by $eight toluene In practice the methanol is added in excess of the required azeotrope forming amount $ith both the excess methanol and the azeotrope being reco+ered together as the distillation o+erhead fraction Creferably the methanol is added in an excess amount of about ' to about &' parts by $eight methanol per * part by $eight toluene  The follo$ing example" discussed $ith reference to the process ?o$ diagram in the dra$ing" represents the best embodiment and mode kno$n to and contemplated by the in+entor in the practice of this in+ention This example and embodiment illustrates the in+ention in terms of a continuous azeotropic distillation and extraction process 9H!MC69

4pent sol+ent from a pharmaceutical process" containing 2&> by $eight MIBK" %> by $eight $ater and %> by $eight of toluene and a trace of nonE+olatile organic material is used as feed It is fed into a rectifying column  of approximately / theoretical plates by pump % from tank ' through a dryer  and a heater / The dryer  is packed $ith dehydrating agent" such as silica gel" $hich is used to remo+e $ater from the feed The resulting liquor is allo$ed to preheat to about &*G 5 $ith steam before it ?o$s into column  !t the inlet to column " a stream of azeotrope former methanol is added to the liquor at a rate of %/ parts by $eight methanol per 21 parts by $eight of dry feed !n o+erhead" containing an azeotrope mixture of %0&> by $eight toluene and 0%> by $eight methanol and an excess of methanol" distills oF from column  and ?o$s to condenser & The bottom liquid from column " containing MIBK and impurities" drops into tank 0 !fter the o+erhead +apor has been condensed by condenser &" the condensate drops into tank 1 Cart of the condensate returns to the rectifying column  as re?ux at a rate of re?ux ratio of * to / The remainder of the condensate is sent by pump 2 to the bottom of the extraction column * Indi+idual sol+ent is isolated $ithin the column by countercurrent extraction $ith $ater introduced at the top of column * in the proportion of % parts of $ater to  part of azeotrope" by $eight The lo$er stream" as extract containing methanol and $ater" goes to tank  $hile the upper stream" as ra#nate containing toluene and a small quantity of methanol and $ater" ?o$s to tank %  The reco+ery of pure sol+ent from each of these streams" extract and ra#nate" is done by fractional distillation $ith rectifying column ' and auxiliary equipment including pumps  and /" heat exchangers & and 0 and tanks 1" 2" and %* by much the same procedure as already described" $ith the follo$ing process conditions 7sing heater &" the preheated temperature is &/G 5 for the extract stream and 1/G 5 for the ra#nate stream The column ' is shorter than column " approximately * theoretical plates The methanol is distilled from the ra#nate as a methanolEtoluene azeotrope that after condensation $ith condenser 0 is stored in tank %* for further processing The tolueneE$ater bottom from column ' is sent to tank 2 by pump %1 The $ater bottom in tank 2 is sent to disposal" $hile the upper layer is pure toluene 4imilarly methanol is reco+ered from the extract stream by distillation in the same column ' as o+erhead $hich" after condensation $ith condenser 0" is collected in tank 1 $here the sol+ent $ill nally go to storage The $ater bottom from column  is sent to $aste disposal MIBK is reco+ered from the bottom liquid in tank 0 by azeotropic distillation in column % $ith li+e steam The liquid steam is sent by pump %% into heater %' and preheated to 11G 5 before entry into column % ,+erhead from column %" containing an azeotrope of MIBK and $ater" passes through condenser % $here it condenses by cooling $ith $ater and drops into tank %/ forming t$o layers  The lo$er $aterErich layer is returned to column % as re?ux The upper MIBKE rich layer" after further cooling in cooler %&" ?o$s into tank %0 The column % bottom containing $ater and impurities is sent to $aste disposal !lthough this in+ention has been disclosed and described herein $ith reference to a process for the separation and reco+ery of spent liquor from a pharmaceutical process" it is intended to be utilized for any sol+ent mixture or

solution regardless of source More specically" this process in+ention may be used to isolate sol+ents ha+ing boiling temperature diFerences of *G 5 or less relati+e to the azeotrope :urther" this process is not limited to a continuous process $hich $ill require a steady supply of substantial amount of spent liquor :or small scale operation" a batch process has an ad+antage of reducing the number of equipments of the same process function ,ther modications of the in+ention may be made $ithout departing from the spirit of the in+ention as set forth in the appended claims