Européisches Patentamt
`
`(19) 0’» European PatentOffice
`
`Office européen des brevets
`
`(11) Ver6ffentlichungsnummer:
`
`(11) Publication number:
`
`(11) Numéro de publication:
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`EP 1 720 821 A0
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`Internationale Anmeldung veroffentlicht durch die
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`Weltorganisation fUr geistiges Eigentum unter der Nummer:
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`wo 2005/085166 (art. 158 des EPU).
`
`International application published by the World
`
`Intellectual Property Organisation under number:
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`WO 2005/085166 (art. 158 Of the EPC).
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`Demande internationale publiée par I’Organisation
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`Mondiale de la Propriété sous |e numéro:
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`WO 2005/085166 (art. 158 de la CBE).
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`(19) 0’» European PatentOffice
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`Office européen des brevets
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`(11) Ver6ffentlichungsnummer:
`
`(11) Publication number:
`
`(11) Numéro de publication:
`
`EP 1 720 821 A0
`
`Internationale Anmeldung veroffentlicht durch die
`
`Weltorganisation fUr geistiges Eigentum unter der Nummer:
`
`wo 2005/085166 (art. 158 des EPU).
`
`International application published by the World
`
`Intellectual Property Organisation under number:
`
`WO 2005/085166 (art. 158 Of the EPC).
`
`Demande internationale publiée par I’Organisation
`
`Mondiale de la Propriété sous |e numéro:
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`WO 2005/085166 (art. 158 de la CBE).
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`Document made
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`available under
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`the
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`Patent Cooperation Treaty (PCT)
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`International application number: PCT/USOS/006092
`
`International filing date:
`
`24 February 2005 (24.02.2005)
`
`Document type:
`
`Certified copy of priority document
`
`Document details:
`
`Country/Office: US
`Number:
`10/708,420
`
`Filing date:
`
`02 March 2004 (02.03.2004)
`
`Date of receipt at the International Bureau:
`
`31 March 2005 (31.03.2005)
`
`Remark:
`
`Priority document submitted or transmitted to the International Bureau in
`compliance with Rule l7.l(a) or (b)
`
`
`
`World Intellectual Property Organization (WIPO) - Geneva, Switzerland
`Organisation Mondiale de la Propriété Intellectuelle (OMPI) - Geneve, Suisse
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`[E'NI’I' ED :‘H‘ES DIS {E‘AI :1 1% NT 0 I?" if 303‘! M. E RC}:
`
`United States Patent and "l'mdmnark Office
`
`
`
`
`
`
`
`March 16, 2005
`
` THIS IS TO CERTIFY THAT ANNEXED HERETO IS A TRUE COPY FROM
`THE RECORDS OF THE UNITED STATES PATENT AND TRADEMARK
`OFFICE OF THOSE PAPERS OF THE BELOW IDENTIFIED PATENT
`
`APPLICATION THAT MET THE REQUIREMENTS TO BE GRANTED A
`FILING DATE.
`
`
`APPLICATION NUMBER: 10/708,420
`FILING DATE: March 02, 2004
`RELATED PCT APPLICATION NUMBER: PCT/U505/06092
`
`
`
`(Twfified by
`
`
`w.»I...-
`\
`
`“wwwb
`
`
`
`1.5 mlw Secretary {if {Timmwrce
`for Imeflcctmxl 'l’mpcrty
`
`
`and Dimmrr of the [Emmi Siat‘es
`Patel}! and ‘1‘mdermrk Office
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`
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`Wmmmmmmm\\\\\fix\\
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`000003
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`Exh. 1014
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`TRANSMITTAL
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`Electronic Version v1.1
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`Stylesheet Version v1.1.0
`
`Title 9“
`lnventlon
`
`REMOVAL OF PERMANGANATE REDUCING COMPOUNDS FROM
`METHANOL CARBONYLATION PROCESS STREAM
`
`Registered Number: 44680
`
`Application Number :
`Date :
`
`First Named Applicant:
`Confirmation Number:
`
`Attorney Docket Number:
`
`Mr. Mark O. Scates
`
`I hereby certify that the use of this system is for OFFICIAL correspondence between patent
`applicants or their representatives and the USPTO. Fraudulent or other use besides the filing
`of official correspondence by authorized parties is strictly prohibited, and subject to a fine
`and/or imprisonment under applicable law.
`
`, the undersigned, certify that l have viewed a display of document(s) being electronically
`|
`submitted to the United States Patent and Trademark Office, using either the USPTO provided
`style sheet or software, and that this is the document(s) I intend for initiation or further
`prosecution of a patent application noted in the submission. This document(s) will become
`part of the official electronic record at the USPTO.
`
`Submitted By:
`lra D. Finkelstein
`
`Mr.
`
`Elec. Sign.
`
`/idf/
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`Sign. Capacity
`Attorney
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`Documents being submitted:
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`Files
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`us-fee-sheet
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`us-request
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`application-body
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`Comments
`
`
`
`CELAO73-usfees.xml
`us-fee-sheet.xsl
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`us-fee-sheet.dtd
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`CELAO73-usrequ .me
`us—request.dtd
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`us-request.xsl
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`CELAO73-trans.xml
`us-application-body.xsl
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`application-body.dtd
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`wipo .ent
`mathm|2.dtd
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`mathmI2-qname-1.mod
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`isogrk3.ent
`isomfrk.ent
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`isomopf.ent
`isomscr.ent
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`isotech.ent
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`isobox.ent
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`isocyr1 .ent
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`isocyr2.ent
`isodia.ent
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`isolat1 .ent
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`073fig1 .tif
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`073fig2.tif
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`
`
`APPLICATION DATA SHEET
`
`Electronic Version v14
`
`Stylesheet Version v14.0
`
`Title of Invention
`
`REMOVAL OF PERMANGANATE REDUCING COMPOUNDS FROM
`METHANOL CARBONYLATION PROCESS STREAM
`
`Application Type :
`
`regular, utility
`
`
`
`Correspondence address:
`
`Customer Number:
`
`Inventors Information:
`
`Inventor 1:
`
`Applicant Authority Type:
`
`Inventor
`
`Citizenship:
`
`Name prefix:
`
`Given Name:
`
`Middle Name:
`
`Family Name:
`
`Residence:
`
`City of Residence:
`
`State of Residence:
`
`Country of Residence:
`
`US
`
`Mr.
`
`0.
`
`TX
`
`US
`
`Address-1 of Mailing Address:
`
`Celanese Chemicals
`
`Address-2 of Mailing Address:
`
`PO. Box 58190
`
`City of Mailing Address:
`
`State of Mailing Address:
`
`Houston
`
`TX
`
`Postal Code of Mailing Address:
`
`77258-8190
`
`Country of Mailing Address:
`
`US
`
`Phone:
`
`Fax:
`
`E-mail:
`
`Inventor 2:
`
`Applicant Authority Type:
`
`Inventor
`
`Citizenship:
`
`Name prefix:
`
`Given Name:
`
`US
`
`Mr.
`
`000006
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`Exh. 1014
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`
`
`Middle Name:
`
`Family Name:
`
`Residence:
`
`City of Residence:
`
`State of Residence:
`
`Country of Residence:
`
`TX
`
`US
`
`Address-1 of Mailing Address:
`
`Celanese Chemicals
`
`Address-2 of Mailing Address:
`
`PO. Box 58190
`
`City of Mailing Address:
`
`State of Mailing Address:
`
`Houston
`
`TX
`
`Postal Code of Mailing Address:
`
`77258-8190
`
`Country of Mailing Address:
`
`US
`
`Phone:
`
`Fax:
`
`E-mail:
`
`Inventor 3:
`
`Applicant Authority Type:
`
`Inventor
`
`Citizenship:
`
`Name prefix:
`
`Given Name:
`
`Middle Name:
`
`Family Name:
`
`Residence:
`
`City of Residence:
`
`State of Residence:
`
`Country of Residence:
`
`US
`
`Mr.
`
`Raymond
`
`J.
`
`Zinobile
`
`Houston
`
`TX
`
`US
`
`
`
`Address-1 of Mailing Address:
`
`Celanese Chemicals
`
`Address-2 of Mailing Address:
`
`PO. Box 58190
`
`City of Mailing Address:
`
`State of Mailing Address:
`
`Houston
`
`TX
`
`Postal Code of Mailing Address:
`
`77258-8190
`
`Country of Mailing Address:
`
`US
`
`Phone:
`
`Fax:
`
`E-mail:
`
`Attorney Information:
`
`practitioner(s) at Customer Number:
`||||I||||||||||||||||||||||||||||||
`23369
`as our attorney(s) or agent(s) to prosecute the application identified above, and to transact all
`business in the United States Patent and Trademark Office connected therewith.
`
`000007
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`Exh. 1014
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`
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`Publication Information:
`
`Suggested Figure for Publication - 2
`Suggested Classification -
`Suggested Technology Center -
`Total Number of Drawing Sheets - 2
`
`Assignee 1 :
`
`Organization Name:
`
`Celanese International Corporation
`
`Address-1 of Mailing Address:
`
`1601 W. LBJ Freeway
`
`Address-2 of Mailing Address:
`
`City of Mailing Address:
`
`State of Mailing Address:
`
`Dallas
`
`TX
`
`Postal Code of Mailing Address:
`
`75234-6034
`
`Country of Mailing Address:
`
`US
`
`E-mail:
`
`Phone:
`
`Fax:
`
`000008
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`Exh. 1014
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`000008
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`Exh. 1014
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`Electronic Version
`
`Stylesheet Version v1.1.1
`
`Description
`
`REMOVAL OF PERMANGANATE
`
`REDUCING COMPOUNDS FROM
`
`METHANOL CARBONYLATION PROCESS
`
`STREAM
`
`BACKGROUND OF INVENTION
`
`1. FIELD OF THE INVENTION
`
`[0001] This invention relates to an improved process for the re—
`
`moval of permanganate reducing compounds and alkyl
`
`iodides formed by the carbonylation of methanol in the
`
`presence of a Group VIII metal carbonylation catalyst.
`
`More specifically, this invention relates to an improved
`
`process for reducing and/or removing precursors of per—
`
`manganate reducing compounds and alkyl iodides from
`
`intermediate streams during the formation of acetic acid
`
`by said carbonylation processes.
`
`2. TECHNICAL BACKGROUND
`
`[0002] Among currently employed processes for synthesizing
`000009
`Exh. 1014
`
`000009
`
`Exh. 1014
`
`
`
`acetic acid, one of the most useful commercially is the
`
`catalyzed carbonylation of methanol with carbon monox—
`
`ide as taught in U.S. Pat. No. 3,769,329 issued to Paulik et
`
`al. on Oct. 30, 1973. The carbonylation catalyst contains
`
`rhodium, either dissolved or otherwise dispersed in a liq—
`
`uid reaction medium or supported on an inert solid, along
`
`with a halogen—containing catalyst promoter as exempli—
`
`fied by methyl iodide. The rhodium can be introduced into
`
`the reaction system in any of many forms, and the exact
`
`nature of the rhodium moiety within the active catalyst
`
`complex is uncertain. Likewise, the nature of the halide
`
`promoter is not critical. The patentees disclose a very
`
`large number of suitable promoters, most of which are
`
`organic iodides. Most typically and usefully, the reaction is
`
`conducted by continuously bubbling carbon monoxide
`
`gas through a liquid reaction medium in which the cata—
`
`lyst is dissolved.
`
`[0003] An improvement in the prior art process for the carbony—
`
`lation of an alcohol to produce the carboxylic acid having
`
`one carbon atom more than the alcohol in the presence of
`
`a rhodium catalyst is disclosed in commonly assigned U.S.
`
`Patent Nos. 5,001,259, issued Mar. 19, 1991; 5,026,908,
`
`issuedJun. 25, 1991; and 5,144,068, issued Sep. 1, 1992;
`
`000010
`
`Exh. 1014
`
`000010
`
`Exh. 1014
`
`
`
`and European Patent No. EP 0 161 874 32, publishedJul.
`
`1, 1992. As disclosed therein, acetic acid is produced
`
`from methanol in a reaction medium containing methyl
`
`acetate, methyl halide, especially methyl iodide, and
`
`rhodium present in a catalytically effective concentration.
`
`These patents disclose that catalyst stability and the pro—
`
`ductivity of the carbonylation reactor can be maintained at
`
`surprisingly high levels, even at very low water concentra—
`
`tions, i.e. 4 weight percent or less, in the reaction medium
`
`(despite the general industrial practice of maintaining ap—
`
`proximately 14—15 wt % water) by maintaining in the reac—
`
`tion medium, along with a catalytically effective amount of
`
`rhodium and at least a finite concentration of water, a
`
`specified concentration of iodide ions over and above the
`
`iodide content which is present as methyl iodide or other
`
`organic iodide. The iodide ion is present as a simple salt,
`
`with lithium iodide being preferred. The patents teach that
`
`the concentration of methyl acetate and iodide salts are
`
`significant parameters in affecting the rate of carbonyla—
`
`tion of methanol to produce acetic acid, especially at low
`
`reactor water concentrations. By using relatively high con—
`
`centrations of the methyl acetate and iodide salt, one ob—
`
`tains a surprising degree of catalyst stability and reactor
`
`000011
`
`Exh. 1014
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`000011
`
`Exh. 1014
`
`
`
`productivity even when the liquid reaction medium con—
`
`tains water in concentrations as low as about 0.1 wt %, so
`
`low that it can broadly be defined simply as "a finite con—
`
`centration" of water. Furthermore, the reaction medium
`
`employed improves the stability of the rhodium catalyst,
`
`i.e. resistance to catalyst precipitation, especially during
`
`the product recovery steps of the process. In these steps,
`
`distillation for the purpose of recovering the acetic acid
`
`product tends to remove from the catalyst the carbon
`
`monoxide which in the environment maintained in the re—
`
`action vessel, is a ligand with stabilizing effect on the
`
`rhodium. U.S. Patent Nos. 5,001,259, 5,026,908 and
`
`5,144,068 are herein incorporated by reference.
`
`[0004]
`
`It has been found that although a low water carbonylation
`
`process for producing acetic acid reduces such by—
`
`products as carbon dioxide, hydrogen, and propionic acid,
`
`the amount of other impurities, present generally in trace
`
`amounts, is also increased, and the quality of acetic acid
`
`sometimes suffers when attempts are made to increase
`
`the production rate by improving catalysts, or modifying
`
`reaction conditions.
`
`[0005]
`
`These trace impurities affect quality of acetic acid, espe—
`
`cially when they are recirculated through the reaction pro—
`
`000012
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`Exh. 1014
`
`000012
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`Exh. 1014
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`
`
`cess. The impurities that decrease the permanganate time
`
`of the acetic acid include carbonyl compounds and unsat—
`
`urated carbonyl compounds. As used herein, the phrase
`
`"carbonyl" is intended to mean compounds that contain
`
`aldehyde or ketone functional groups, which compounds
`
`may or may not possess unsaturation. See Catalysis ofOr—
`
`ganic Reaction, 75, 369—380 (1998), for further discussion
`
`on impurities in a carbonylation process.
`
`[0006]
`
`The present invention is directed to reducing and/or re—
`
`moving permanganate reducing compounds (PRC"s) such
`
`as acetaldehyde, acetone, methyl ethyl ketone, butyralde—
`
`hyde, crotonaldehyde, 2—ethyl crotonaldehyde, and
`
`2—ethyl butyraldehyde and the like, and the aldol conden—
`
`sation products thereof. The present invention also leads
`
`to reduction of propionic acid.
`
`[0007]
`
`The carbonyl impurities described above, such as ac—
`
`etaldehyde, may react with iodide catalyst promoters to
`
`form multi—carbon alkyl iodides, e.g., ethyl iodide, propyl
`
`iodide, butyl iodide, pentyl iodide, hexyl iodide and the
`
`like. It is desirable to remove alkyl iodides from the reac—
`
`tion product because even small amounts of these impu—
`
`rities in the acetic acid product tend to poison the catalyst
`
`used in the production of vinyl acetate, the product most
`
`000013
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`Exh. 1014
`
`000013
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`Exh. 1014
`
`
`
`commonly produced from acetic acid. The present inven—
`
`tion is thus also directed to removal of alkyl iodides, in
`
`particular C2_12 alkyl iodide compounds. Accordingly, be—
`
`cause many impurities originate with acetaldehyde, it is a
`
`primary objective to remove acetaldehyde from the pro—
`
`cess so as to reduce the alkyl iodide content.
`
`[0008]
`
`Conventional techniques to remove impurities include
`
`treating the acetic acid product with oxidizers, ozone, wa—
`
`ter, methanol, activated—carbon, amines, and the like,
`
`which treatment may or may not be combined with distil—
`
`lation of the acetic acid. The most typical purification
`
`treatment involves a series of distillations of the final
`
`product. It is also known, for example from U.S. Patent
`
`No. 5,783,731, to remove carbonyl impurities from or—
`
`ganic streams by treating the organic streams with an
`
`amine compound such as hydroxylamine, which reacts
`
`with the carbonyl compounds to form oximes, followed by
`
`distillation to separate the purified organic product from
`
`the oxime reaction products. However, the additional
`
`treatment of the final product adds cost to the process,
`
`and distillation of the treated acetic acid product can re—
`
`sult in additional impurities being formed.
`
`[0009] While it is possible to obtain acetic acid of relatively high
`
`000014
`
`Exh. 1014
`
`000014
`
`Exh. 1014
`
`
`
`purity, the acetic acid product formed by the low—water
`
`carbonylation process and purification treatment de—
`
`scribed above frequently remains somewhat deficient with
`
`respect to the permanganate time due to the presence of
`
`small proportions of residual impurities. Since a sufficient
`
`permanganate time is an important commercial test,
`
`which the acid product must meet to be suitable for many
`
`uses, the presence of impurities that decrease perman—
`
`ganate time is objectionable. Moreover, it is not economi—
`
`cally or commercially feasible to remove minute quantities
`
`of these impurities from the acetic acid by distillation be—
`
`cause some of the impurities have boiling points close to
`
`that of the acetic acid product.
`
`[0010]
`
`It has thus become important to identify economically vi—
`
`able methods of removing impurities elsewhere in the
`
`carbonylation process without contaminating the final
`
`product or adding unnecessary costs. U.S. Patent No.
`
`5,756,836, incorporated herein by reference, discloses a
`
`method for manufacturing high purity acetic acid by ad—
`
`justing the acetaldehyde concentration of the reaction so—
`
`lution below 1500 ppm. It is stated that by maintaining
`
`the acetaldehyde concentration below this threshold, it is
`
`possible to suppress the formation of impurities such that
`
`000015
`
`Exh. 1014
`
`000015
`
`Exh. 1014
`
`
`
`one need only distill the crude acetic acid product to ob—
`
`tain high purity acetic acid.
`
`[0011]
`
`European Patent No. EP 0 487 284 Bl, published April 12,
`
`1995, discloses that carbonyl impurities present in the
`
`acetic acid product generally concentrate in the overhead
`
`from the light ends column. Accordingly, the light ends
`
`column overhead is treated with an amine compound
`
`(such as hydroxylamine), which reacts with the carbonyl
`
`compounds to form oxime derivatives that can be sepa—
`
`rated from the remaining overhead by distillation, result—
`
`ing in an acetic acid product with improved permanganate
`
`time.
`
`[0012]
`
`European Patent Application No. EP 0 687 662 A2 and U.S.
`
`Patent No. 5,625,095 describe a process for producing
`
`high purity acetic acid in which it is stated that an ac—
`
`etaldehyde concentration of 400 ppm or less is main—
`
`tained in the reactor by using a single or multi—stage dis—
`
`tillation process to remove acetaldehyde. Streams sug—
`
`gested for processing to remove acetaldehyde include a
`
`light phase containing primarily water, acetic acid and
`
`methyl acetate; a heavy phase containing primarily methyl
`
`iodide, methyl acetate and acetic acid; an overhead stream
`
`containing primarily methyl iodide and methyl acetate; or
`
`000016
`
`Exh. 1014
`
`000016
`
`Exh. 1014
`
`
`
`a recirculating stream formed by combining the light and
`
`heavy phase. These references do not identify which of
`
`these streams possesses the greatest concentration of ac—
`
`etaldehyde.
`
`[0013]
`
`EP 0 687 662 A2 and U.S. Patent No. 5,625,095 also dis—
`
`close management of reaction conditions to control the
`
`formation of acetaldehyde in the reactor. Although it is
`
`stated that formation of by—products such as crotonalde—
`
`hyde, 2—ethylcrotonaldehyde, and alkyl iodides is reduced
`
`by controlling the formation of acetaldehyde, it is also
`
`pointed out that management of reaction conditions as
`
`proposed increases the formation of propionic acid, an
`
`undesirable by—product.
`
`[0014]
`
`More recently, it has been disclosed in commonly as—
`
`signed U.S. Patent Nos. 6,143,930 and 6,339,171 that it is
`
`possible to significantly reduce the undesirable impurities
`
`in the acetic acid product by performing a multi—stage
`
`purification on the light ends column overhead. These
`
`patents disclose a purification process in which the light
`
`ends overhead is distilled twice, in each case taking the
`
`acetaldehyde overhead and returning a methyl iodide rich
`
`residuum to the reactor. The acetaldehyde—rich distillate
`
`is optionally extracted with water to remove the majority
`
`000017
`
`Exh. 1014
`
`000017
`
`Exh. 1014
`
`
`
`of the acetaldehyde for disposal, leaving a significantly
`
`lower acetaldehyde concentration in the raffinate that is
`
`recycled to the reactor. U.S. Patent Nos. 6,143,930 and
`
`6,339,171 are incorporated herein by reference in their
`
`entirety.
`
`[0015]
`
`While the above—described processes have been success—
`
`ful in removing carbonyl impurities from the carbonylation
`
`system and for the most part controlling acetaldehyde
`
`levels and permanganate time problems in the final acetic
`
`acid product, further improvements can still be made. Ac—
`
`cordingly, there remains a need for alternative processes
`
`to improve the efficiency of acetaldehyde removal. The
`
`present invention provides one such alternative solution.
`
`SUMMARY OF INVENTION
`
`[0016]
`
`In one aspect, the present invention provides a process
`
`for producing acetic acid that includes the following steps:
`
`(a) reacting methanol, methyl acetate, methyl formate or
`
`dimethyl ether with carbon monoxide in a suitable reac—
`
`tion medium that includes a catalyst and an organic io—
`
`dide;(b) separating the products of the reaction into a
`
`volatile product phase that contains acetic acid, methyl
`
`iodide, water, and permanganate reducing compounds
`
`(PRC's), and a less volatile phase containing the catalyst
`
`000018
`
`Exh. 1014
`
`000018
`
`Exh. 1014
`
`
`
`and acetic acid;(c) distilling the volatile product phase to
`
`yield a purified product and a first overhead that contains
`
`organic iodide, water, acetic acid, and unreacted
`
`methanol; (d) distilling at least a portion of the first over—
`
`head to produce a second overhead containing methyl io—
`
`dide, water, C2_ 2 alkyl iodides, PRC's and dimethyl
`
`1
`
`ether;(e) extracting the second overhead with water to
`
`provide a first aqueous extract and a first raffinate; and (f)
`
`extracting the first raffinate with water to provide a sec—
`
`ond raffinate and a second aqueous extract containing
`
`concentrated PRC's for disposal.
`
`[0017]
`
`Preferably, at least a portion of the second raffinate is re—
`
`cycled directly or indirectly to the reactor, as are the bot—
`
`toms from the distillation steps. Most preferably, the sec—
`
`ond overhead contains sufficient dimethyl ether to reduce
`
`the solubility of methyl iodide in the aqueous extracts, as
`
`will be explained further below.
`
`[0018]
`
`In another aspect, the present invention provides an im—
`
`proved method for separating a mixture containing water,
`
`acetic acid, methyl iodide, methyl acetate, methanol, at
`
`least one C2_12 alkyl iodide and at least one permanganate
`
`reducing compound (PRC). The improved method includes
`
`the following steps: (a) distilling the mixture to form a
`
`000019
`
`Exh. 1014
`
`000019
`
`Exh. 1014
`
`
`
`PRC enriched overhead stream containing dimethyl ether;
`
`(b) extracting the overhead stream with water and sepa—
`
`rating therefrom a first aqueous stream containing at least
`
`one PRC; and (c) extracting the extracted overhead stream
`
`with water and separating therefrom a second aqueous
`
`stream containing at least one PRC. Most preferably, the
`
`overhead stream contains sufficient dimethyl ether to re—
`
`duce the solubility of methyl iodide in the aqueous ex—
`
`tracts.
`
`[0019]
`
`In still another aspect, the present invention provides an
`
`improved method for reduction and/or removal of per—
`
`manganate—reducing compounds (PRC's) and C2
`
`2 alkyl
`
`—1
`
`iodide compounds formed in the carbonylation of a car—
`
`bonylatable material such as methanol, methyl acetate,
`
`methyl formate or dimethyl ether to a product of acetic
`
`acid. In the improved method, the methanol is carbony—
`
`lated in a reaction medium containing a catalyst and an
`
`organic iodide; the products of the carbonylation reaction
`
`are phase separated into (1) a volatile phase containing
`
`acetic acid product, organic iodide, water, and at least one
`
`PRC, and (2) a less volatile phase; and the volatile phase is
`
`distilled to yield a purified product and an overhead con—
`
`taining organic iodide, water, acetic acid, and PRC. The
`
`000020
`
`Exh. 1014
`
`000020
`
`Exh. 1014
`
`
`
`improvement includes the steps of (a) distilling at least a
`
`portion of the overhead to provide a PRC enriched over—
`
`head stream containing dimethyl ether; (b) extracting the
`
`PRC enriched overhead stream with water and separating
`
`therefrom an aqueous waste stream containing PRC's; and
`
`(c) extracting the extracted overhead stream with water
`
`and separating therefrom a second aqueous waste stream
`
`also containing at least one PRC. Most preferably, the
`
`overhead stream contains sufficient dimethyl ether to re—
`
`duce the solubility of methyl iodide in the aqueous ex—
`
`tracts.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`[0020]
`
`FIG. 1 illustrates the prior art process, as disclosed in U.S.
`
`Patent No. 6,339,171, for the removal of carbonyl impuri—
`
`ties from an intermediate stream of the carbonylation
`
`process for the production of acetic acid by a carbonyla—
`
`tion reaction.
`
`[0021]
`
`FIG. 2 illustrates a preferred embodiment of the present
`
`invention.
`
`[0022] While the invention is susceptible to various modifications
`
`and alternative forms, specific embodiments have been
`
`shown by way of example in the drawings and will be de—
`
`scribed in detail herein. It should be understood, however,
`
`000021
`
`Exh. 1014
`
`000021
`
`Exh. 1014
`
`
`
`that the invention is not intended to be limited to the par—
`
`ticular forms disclosed. Rather, the invention is intended
`
`to cover all modifications, equivalents and alternatives
`
`falling within the scope of the invention as defined by the
`
`appended claims.
`
`DETAILED DESCRIPTION
`
`[0023]
`
`Illustrative embodiments of the invention are described
`
`below. In the interest of clarity, not all features of an ac—
`
`tual implementation are described in this specification. It
`
`will of course be appreciated that in the development of
`
`any such actual embodiment, numerous implementation—spe—
`
`cific decisions must be made to achieve the developers'
`
`specific goals, such as compliance with system—related
`
`and business—related constraints, which will vary from one
`
`implementation to another. Moreover, it will be appreci—
`
`ated that such a development effort might be complex
`
`and time—consuming, but would nevertheless be a routine
`
`undertaking for those of ordinary skill in the art having
`
`the benefit of this disclosure.
`
`[0024]
`
`The purification process of the present invention is useful
`
`in any process used to carbonylate methanol (or another
`
`carbonylatable material such as methyl acetate, methyl
`
`formate or dimethyl ether, or mixtures thereof) to acetic
`
`000022
`
`Exh. 1014
`
`000022
`
`Exh. 1014
`
`
`
`acid in the presence of a Group VIII metal catalyst such as
`
`rhodium and an iodide promoter. A particularly useful
`
`process is the low water rhodium—catalyzed carbonylation
`
`of methanol to acetic acid as exemplified in U.S. Patent
`
`No. 5,001,259. Generally, the rhodium component of the
`
`catalyst system is believed to be present in the form of a
`
`coordination compound of rhodium with a halogen com—
`
`ponent providing at least one of the ligands of such coor—
`
`dination compound. In addition to the coordination of
`
`rhodium and halogen, it is also believed that carbon
`
`monoxide coordinates with rhodium. The rhodium com—
`
`ponent of the catalyst system may be provided by intro—
`
`ducing into the reaction zone rhodium in the form of
`
`rhodium metal, rhodium salts such as the oxides, ac—
`
`etates, iodides, etc., or other coordination compounds of
`
`rhodium, and the like.
`
`[0025] The halogen—promoting component of the catalyst system
`
`consists of a halogen compound comprising an organic
`
`halide. Thus, alkyl, aryl, and substituted alkyl or aryl
`
`halides can be used. Preferably, the halide promoter is
`
`present in the form of an alkyl halide in which the alkyl
`
`radical corresponds to the alkyl radical of the feed alco—
`
`hol, which is carbonylated. Thus, in the carbonylation of
`
`000023
`
`Exh. 1014
`
`000023
`
`Exh. 1014
`
`
`
`methanol to acetic acid, the halide promoter will include
`
`methyl halide, and more preferably methyl iodide.
`
`[0026]
`
`The liquid reaction medium employed may include any
`
`solvent compatible with the catalyst system and may in—
`
`clude pure alcohols, or mixtures of the alcohol feedstock
`
`and/or the desired carboxylic acid and/or esters of these
`
`two compounds. The preferred solvent and liquid reaction
`
`medium for the low water carbonylation process is the
`
`carboxylic acid product. Thus, in the carbonylation of
`
`methanol to acetic acid, the preferred solvent is acetic
`
`acid.
`
`[0027]
`
`Water is contained in the reaction medium but at concen—
`
`trations well below that which has heretofore been
`
`thought practical for achieving sufficient reaction rates. It
`
`has previously been taught that in rhodium—catalyzed car—
`
`bonylation reactions of the type set forth in this invention,
`
`the addition of water exerts a beneficial effect upon the
`
`reaction rate (U.S. Patent No. 3,769,329). Thus most com—
`
`mercial operations run at water concentrations of at least
`
`about 14 wt %. Accordingly, it is quite unexpected that re—
`
`action rates substantially equal to and above reaction
`
`rates obtained with such high levels of water concentra—
`
`tion can be achieved with water concentrations below 14
`
`000024
`
`Exh. 1014
`
`000024
`
`Exh. 1014
`
`
`
`wt % and as low as about 0.1 wt %.
`
`[0028]
`
`In accordance with the carbonylation process most useful
`
`to manufacture acetic acid according to the present in—
`
`vention, the desired reaction rates are obtained even at
`
`low water concentrations by including in the reaction
`
`medium methyl acetate and an additional iodide ion which
`
`is over and above the iodide which is present as a catalyst
`
`promoter such as methyl iodide or other organic iodide.
`
`The additional iodide promoter is an iodide salt, with
`
`lithium iodide being preferred. It has been found that un—
`
`der low water concentrations, methyl acetate and lithium
`
`iodide act as rate promoters only when relatively high
`
`concentrations of each of these components are present
`
`and that the promotion is higher when both of these com—
`
`ponents are present simultaneously (U.S. Patent No.
`
`5,001,259). The concentration of lithium iodide used in
`
`the reaction medium of the preferred carbonylation reac—
`
`tion system is believed to be quite high as compared with
`
`what little prior art there is dealing with the use of halide
`
`salts in reaction systems of this sort. The absolute con—
`
`centration of iodide ion content is not a limitation on the
`
`usefulness of the present invention.
`
`[0029]
`
`The carbonylation reaction of methanol to acetic acid
`
`000025
`
`Exh. 1014
`
`000025
`
`Exh. 1014
`
`
`
`product may be carried out by contacting the methanol
`
`feed, which is in the liquid phase, with gaseous carbon
`
`monoxide bubbled through a liquid acetic acid solvent re—
`
`action medium containing the rhodium catalyst, methyl
`
`iodide promoter, methyl acetate, and additional soluble
`
`iodide salt, at conditions of temperature and pressure
`
`suitable to form the carbonylation product. It will be gen—
`
`erally recognized that it is the concentration of iodide ion
`
`in the catalyst system that is important and not the cation
`
`associated with the iodide, and that at a given molar con—
`
`centration of iodide the nature of the cation is not as sig—
`
`nificant as the effect of the iodide concentration. Any
`
`metal iodide salt, or any iodide salt of any organic cation,
`
`or quaternary cation such as a quaternary amine or phos—
`
`phine or inorganic cation can be used provided that the
`
`salt is sufficiently soluble in the reaction medium to pro—
`
`vide the desired level of the iodide. When the iodide is
`
`added as a metal salt, preferably it is an iodide salt of a
`
`member of the group consisting of the metals of Group IA
`
`and Group ”A of the periodic table as set forth in the
`
`"Handbook of Chemistry and Physics" published by CRC
`
`Press, Cleveland, Ohio, 2002—03 (83rd edition). In partic—
`
`ular, alkali metal iodides are useful, with lithium iodide
`
`000026
`
`Exh. 1014
`
`000026
`
`Exh. 1014
`
`
`
`being preferred. In the low water carbonylation process
`
`most useful in this invention, the additional iodide over
`
`and above the organic iodide promoter is present in the
`
`catalyst solution in amounts of from about 2 to about 20
`
`wt %, the methyl acetate is present in amounts of from
`
`about 0.5 to about 30 wt %, and the lithium iodide is
`
`present in amounts of from about 5 to about 20 wt %. The
`
`rhodium catalyst is present in amounts of from about 200
`
`to about 2000 parts per million (ppm).
`
`[0030]
`
`Typical reaction temperatures for carbonylation will be
`
`approximately 150 to about 250°C, with the temperature
`
`range of about 180 to about 220°C being the preferred
`
`range. The carbon monoxide partial pressure in the reac—
`
`tor can vary widely but is typically about 2 to about 30 at—
`
`mospheres, and preferably, about 3 to about 10 atmo—
`
`spheres. Because of the partial pressure of by—products
`
`and the vapor pressure of the contained liquids, the total
`
`reactor pressure will range from about 15 to about 40 at—
`
`mospheres.
`
`[0031]
`
`A typical reaction and acetic acid recovery system that is
`
`used for the iodide—promoted rhodium catalyzed car—
`
`bonylation of methanol to acetic acid is shown in FIG. 1
`
`and includes a liquid phase carbonylation reactor, flasher,
`
`000027
`
`Exh. 1014
`
`000027
`
`Exh. 1014
`
`
`
`and a methyl iodide acetic acid light ends column 14
`
`which has an acetic acid side stream 17 which proceeds to
`
`further purification. The reactor and flasher are not shown
`
`in FIG. 1. These are considered standard equipment now
`
`well known in the carbonylation process art. The carbony—
`
`lation reactor is typically either a stirred vessel or bubble—
`
`column type within which the reacting liquid or slurry
`
`contents are maintained automatically at a constant level.
`
`Into this reactor there are continuously introduced fresh
`
`methanol, carbon monoxide, sufficient water as needed to
`
`maintain at least a finite concentration of water in the re—
`
`action medium, recycled catalyst solution from the flasher
`
`base, a recycled methyl iodide and methyl acetate phase,
`
`and a recycled aqueous acetic acid phase from an over—
`
`head receiver decanter of the methyl iodide acetic acid
`
`light ends or splitter column 14. Distillation systems are
`
`employed that provide means for recovering the crude
`
`acetic acid and recycling catalyst solution, methyl iodide,
`
`and methyl acetate to the reactor. In a preferred process,
`
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