Liquid Phase Dehydration of Tertiary Butyl Alcohol

Patentamt Europaisches ||| || 1 1| || || || || || || || ||| ||| || (19) J European Patent Office

Office europeen des brevets (1 1 ) EP 0 712 824 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publicationation and mention (51) Int. CI.6: C07C 1 1/09, C07C 1/24 of the grant of the patent: 08.09.1999 Bulletin 1999/36

(21) Application number: 95308249.2

(22) Dateof filing: 17.11.1995

(54) Liquid phase dehydration of tertiary butyl alcohol Verfahren zur Dehydratisierung in der Flussigphase von tert-Butylalkohol Procede pour la deshydratation en phase liquide d'alcool tert-butylique

(84) Designated Contracting States: (72) Inventor: Gupta, Vijai P. BE DE FR GB IT NL Berwyn, PA 1931 2 (US)

(30) Priority: 21.11.1994 US 342560 (74) Representative: Cropp, John Anthony David et al (43) Date of publication of application: MATHYS & SQUIRE 22.05.1996 Bulletin 1996/21 100 Grays Inn Road London, WC1X8AL(GB) (73) Proprietor: ARCO Chemical Technology, L.P. (56) References cited: Greenville, Delaware 19807 (US) EP-A- 0 082 937 US-A- 2 377 026 US-A-4 155 945

CM CO CM Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in o a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. Q_ 99(1) European Patent Convention). LU Printed by Xerox (UK) Business Services 2.16.7/3.6 1 EP 0 712 824 B1 2

Description tion of the condensed mixture of tertiary butyl alcohol, water and isobutanol and/or secondary butanol is [0001] The present invention relates to the liquid required to fall within specified limits as set out below. phase dehydration of tertiary butyl alcohol to form iso- [0007] A key feature is regulation of the composition butylene wherein the dehydration is carried out in a boil- 5 from the dehydrator such that the phase separation nec- ing reactor, a vapor stream including dehydration essary to the invention can be accomplished. products is removed and cooled, isobutylene is sepa- [0008] The invention will now be described with refer- rated, and the remaining product mixture is phase sep- ence to a preferred embodiment and with the aid of the arated into an organic phase which is recycled and an accompanying drawings in which: aqueous phase which is purged. 10 Figure 1 illustrates schematically practice of the Description of the Prior Art invention. Figure 2 is a phase diagram on which is delineated [0002] The dehydration of tertiary butyl alcohol to pro- the area within which the composition of condensed duce isobutylene is a known reaction. In general, the is mixture of water, reaction is carried out in the vapor phase at very high temperatures of the order of 370°C or so which requires tertiary butyl alcohol and isobutanol and/or secondary the use of expensive heaters and other costly hardware butanol which is necessary for successful practice of and which results in high energy consumption. the invention must lie. [0003] Liquid phase dehydration systems are also 20 known. U.S. Patents 3,510,538, 4,165,343 and Detailed Description 4,155,945 describe such systems. Generally, a ben- zene or xylene azeotroping agent is used to remove [0009] The liquid phase dehydration of the tertiary water from the liquid reaction system. butyl alcohol is carried out at conditions which are gen- [0004] However, the aromatic azeotroping agents are 25 erally known for this reaction. Broadly, temperatures in expensive and tend to react to some extent with isobuty- the range of about 70-200°C, preferably 120-160°C are lene, and the relatively heavy products have to be employed. It is generally desirable to operate at super- purged from the system resulting in product yield loss atmospheric pressure sufficient to maintain the reaction and possible catalyst loss, especially when a soluble mixture in the liquid phase while permitting vaporization catalyst such as para toluene sulfonic acid is employed. 30 of product water and isobutylene along with tertiary [0005] The present invention provides a process for butyl alcohol, isobutanol and/or secondary butanol and the liquid phase dehydration of tertiary butyl alcohol to removal of the same from the reaction zone. Generally, isobutylene which comprises pressures ranging from 207-2758 kPa gauge (30-400 psig), preferably 345-1724 kPa gauge (50-250 psig) are i) subjecting a liquid dehydration reaction mixture 35 employed. comprising tertiary butyl alcohol; isobutanol and/or [0010] An acidic catalyst is employed in accordance secondary butanol; water; and isobutylene, the rel- with known procedures. Sulfonic acid cation exchange ative amounts of the components of the reaction resin catalysts can be employed as can sulfuric acid. mixture being effective to provide the condensed However, it is especially preferred to use organic sul- mixture defined in ii), to catalytic liquid phase dehy- 40 fonic acid catalysts and para toluene sulfonic acid dration conditions; (PTSA) or methane sulfonic acid are especially useful. ii) separating a vapour mixture comprised of iso- [001 1 ] The amount of catalyst is not critical; it is pre- butylene, water, tertiary butyl alcohol and isobuta- ferred in the case of soluble catalysts to operate with nol and/or secondary butanol and cooling the catalyst amounts below the solubility limit, e.g. 0.1-4.0 vapour mixture to condense tertiary butyl alcohol, 45 wt%, based on the entire reaction mixture. water and isobutanol and/or secondary butanol, the [001 2] A problem with prior liquid phase tertiary butyl condensed mixture of tertiary butyl alcohol, water alcohol dehydration procedures has been the difficulty and isobutanol and/or secondary butanol having a in removing the relatively high boiling water of dehydra- composition in the area XYZ of Figure 2; and recov- tion, which, if not removed, effectively interferes with the ering isobutylene; so desired dehydration. The use of costly and reactive sol- iii) phase separating the condensed tertiary butyl vents such as xylene has not been entirely satisfactory. alcohol, water and isobutanol and/or secondary [001 3] Now in accordance with the present invention, butanol into an organic-rich upper phase and a the dehydration is carried out with continuous removal water-rich lower phase; and of a reaction vapor mixture containing the water and iso- iv) recycling the organic-rich phase to the dehydra- 55 butylene products of reaction, this vapor mixture having tion step. a composition which after condensation and separation of isobutylene will undergo phase separation into an [0006] In accordance with the invention, the composi- organic-rich phase and an aqueous phase which con-

2 3 EP 0 712 824 B1 4 tains the water of dehydration. The organics-rich phase composition is well removed from the Plait point Q and can be recycled to the dehydration while the aqueous an especially preferred composition is that designated phase can be purged after recovery of any organics, if by X'Y'Z' in Figure 2. Because isobutanol and second- desired. ary butanol behave similarly in the system, they are [0014] Practice of the invention is especially useful for s treated in the phase diagram as a single component. the dehydration of tertiary butyl alcohol which is formed [0023] Composition of the reaction mixture compo- in the oxirane propylene oxide/tertiary butyl alcohol nents after isobutylene separation is regulated by the process. Small amounts of isobutanol, isopropanol, composition of the feed and recycle streams to zone 1 sec.-butanol, and the like are formed as impurities in the as well as by the conversion of tertiary butyl alcohol in oxirane process, thus providing a source for the materi- w zone 1 and is readily determined and regulated during als used in the invention. practice of the invention. [001 5] Practice of the invention can be described with [0024] Generally, it is advantageous and preferred to reference to accompanying Figure 1 . Referring to Fig- maintain a liquid dehydration reaction mixture composi- ure 1 , the tertiary butyl alcohol feed stream is continu- tion by weight of about 5 to 30% tertiary butyl alcohol, ously passed to dehydrator 1 via line 2 wherein the 15 30 to 70% isobutanol and/or secondary butanol, 5 to feedstream is subjected to reaction conditions effective 35% water and less than 5% isobutylene. for the liquid phase dehydration of tertiary butyl alcohol [0025] The following example illustrates the invention. to isobutylene and water. Dehydrator 1 can be a contin- Referring to Figure 1 , a tertiary butyl alcohol feedstream uous stirred tank reactor (CSTR) or any equivalent passes to dehydrator 1 via line 2 at the rate of 2041 apparatus for carrying out this reaction. 20 Kg/hr (4,500 Ibs/hr). This stream comprises by weight [001 6] A vapor mixture comprised of product isobuty- 94.5% tertiary butyl alcohol, 1 .1% water, and 4.4% isob- lene and water together with unreacted tertiary butyl utanol. In dehydrator 1 , tertiary butyl alcohol is dehy- alcohol and also containing isobutanol and/or second- drated in the liquid phase to isobutylene and water at ary butanol is separated via line 3 and passed to heat 160°C and 1379 kpa (200 psia); para toluene sulfonic exchanger 4 wherein the vapor mixture is cooled to a 25 acid catalyst is used, the catalyst is present in a concen- temperature effective to condense the non-isobutylene tration of about 2.5wt% based on the liquid reaction mix- components. ture. [001 7] The cooled mixture is passed via line 5 to sep- [0026] A reaction vapour mixture is continuously aration zone 6 which for purpose of illustration is shown removed via line 3 in amount of 4450 kg/hr (9,810 as only a single zone where in actuality it can be plural- 30 Ibs/hr), this mixture comprised by weight of 1 1 .5% terti- ity of zones. ary butyl alcohol, 32.4% isobutylene, 22% water and [001 8] From zone 6, product isobutylene vapor is sep- 34% isobutanol. arated via line 7. This product stream can, if desired, be [0027] Steady state composition of the liquid reaction treated for the separation of small amounts of water and mixture in dehydrator 1 by weight is 1 5% tertiary butyl organics contained therein (not shown). 35 alcohol, 22.5% water, 62.5% isobutanol and a trace of [001 9] The liquid components of the dehydration reac- isobutylene. tion mixture are phase separated in zone 6 into an [0028] The reaction vapor mixture is cooled in heat upper organic-rich phase which is concentrated in unre- exchanger 4 to about 32°C and pressure is lowered to acted tertiary butyl alcohol as well as in isobutanol 137.9 kPa (20 psia). The cooled mixture passes via line and/or secondary butanol and a lower water-rich phase 40 5 to separation zone 6 and a product isobutylene vapor which contains the net water produced in the tertiary stream is separated from liquid condensation products butyl alcohol dehydration reaction. and is removed via line 7 at the rate of 1 480 kg/hr (3,263 [0020] The tertiary butyl alcohol containing organics- Ibs/hr). This stream comprises by weight 96.4% isobuty- rich phase passes via line 8 back to dehydration zone 1 lene, 1.1% water, 1.1% tertiary butyl alcohol and 1.4% while the water-rich phase is separated via line 9 and 45 isobutanol. the net dehydration water purged after recovery of con- [0029] The liquid reaction mixture components, after tained organics (not shown). separation of the isobutylene vapor stream, comprise by [0021 ] In order to successfully carry out the invention weight about 0.6% isobutylene, 16.7% tertiary butyl it is essential that the lower water-rich layer removed via alcohol, 32.4% water and 50.3% isobutanol. Referring line 9 contain the water formed by the dehydration reac- so to Figure 2, it can be seen that this composition is well tion since recycle of such water via line 8 would cause a within area XYZ of the phase diagram. This mixture is water build-up in dehydrator 1 which ultimately would separated in separator 6 into an upper organic-rich layer prevent further tertiary butyl alcohol dehydration. and a lower water-rich layer. [0022] For effective phase separation of the dehydra- [0030] The organic-rich layer is removed via line 8 and tion reaction mixture components after isobutylene sep- 55 passed to dehydrator 1 at the rate of 2447 kg/hr (5,394 aration, it is essential that the composition of these Ibs/hr), the composition by weight of this stream being components be within the two phase region defined in 19.3% tertiary butyl alcohol, 0.7% isobutylene, 20.5% the phase diagram of Figure 2 by XYZ. Preferably the water and 59.5% isobutanol.

3 5 EP 0 712 824 B1 6

[0031 ] The water-rich layer is removed via line 9 at the nol and/or secondary butanol has a composition in rate of 523 kg/hr (1,153 Ibs/hr), the composition by the area X'Y'Z' of Figure 2. weight of this stream being 4.6% tertiary butyl alcohol, 0. 05. isobutylene, 88.2% water and 7.1% isobutanol. Patentanspruche 5 Comparative Example 1 . Verfahren zur Dehydratisierung von tertiarem Butyl- alkohol zu Isobutylen in der flussigen Phase, bei [0032] By way of contrast, in a similar operation dem man except that the condensed reaction mixture components after isobutylene separation had the composition w i) ein flussiges Dehydratisierungs-Reaktions- by weight of 59.9% tertiary butyl alcohol, 0.4% isobuty- gemisch, das tertiaren Butylalkohol, Isobutanol lene, 27.9% water and 1 1 .7% isobutanol, a phase sep- und/oder sekundares Butanol, Wasser und Iso- aration could not be obtained as the composition was butylen enthalt, katalytischen Dehydratisie- well outside area XYZ of Figure 2. rungsbedingungen in der flussigen Phase [0033] When the condensed reaction mixture compo- is aussetzt, wobei die relativen Mengen der Kom- nents are recycled to dehydrator 1 , water rapidly builds ponenten des Reaktionsgemischs wirksam up in the dehydrator with separation into two liquid das in ii) definierte kondensierte Gemisch zur phases. Upon purging water from the dehydrator to pre- Verfiigung stellen; vent this build-up, catalyst is also purged causing the dehydration reaction to cease. 20 ii) ein aus Isobutylen, Wasser, tertiarem Butyl- alkohol und Isobutanol und/oder sekundarem Claims Butanol bestehendes Dampfgemisch abtrennt und dieses kuhlt, urn tertiaren Butylalkohol, 1 . A process for the liquid phase dehydration of terti- Wasser und Isobutanol und/oder sekundares ary butyl alcohol to isobutylene which comprises 25 Butanol zu kondensieren, wobei das kondensierte Gemisch aus tertiarem Butylalkohol, i) subjecting a liquid dehydration reaction mix- Wasser und Isobutanol und/oder sekundarem ture comprising tertiary butyl alcohol; isobuta- Butanol eine Zusammensetzung im Bereich nol and/or secondary butanol; water; and XYZ von Fig. 2 aufweist, und Isobutylen isobutylene, the relative amounts of the compo- 30 gewinnt, nents of the reaction mixture being effective to provide the condensed mixture defined in ii), to iii) den kondensierten tertiaren Butylalkohol, catalytic liquid phase dehydration conditions; Wasser und Isobutanol und/oder sekundares ii) separating a vapor mixture comprised of iso- Butanol in eine an organischen Substanzen butylene, water, tertiary butyl alcohol and isob- 35 reiche obere Phase und eine wasserreiche utanol and/or secondary butanol and cooling untere Phase trennt und the vapor mixture to condense tertiary butyl alcohol, water and isobutanol and/or second- iv) die an organischen Substanzen reiche ary butanol, the condensed mixture of tertiary Phase zum Dehydratisierungsschritt zurucklei- butyl alcohol, water and isobutanol and/or sec- 40 tet. ondary butanol having a composition inn the area XYZ of Figure 2; and recovering isobuty- 2. Verfahren nach Anspruch 1 , bei dem das f lussige lene; Dehydratisierungs-Reaktionsgemisch 5 bis 30 iii) phase separating the condensed tertiary Gew.-% tertiaren Butylalkohol, 30 bis 70 Gew.-% butyl alcohol, water and isobutanol and/or sec- 45 Isobutanol und/oder sekundares Butanol, 5 bis 35 ondary butanol into an organic-rich upper Gew.-% Wasser und weniger als 5 Gew.-% Isobuty- phase and a water-rich lower phase; and len umfaBt. iv) recycling the organic-rich phase to the dehydration step. 3. Verfahren nach Anspruch 1 oder 2, bei dem das 50 kondensierte Gemisch aus tertiarem Butylalkohol, 2. The process of Claim 1 wherein the liquid dehydra- Wasser und Isobutanol und/oder sekundarem tion reaction mixture comprises from 5 to 30 wt% Butanol eine Zusammensetzung im Bereich von tertiary butyl alcohol; from 30 to 70 wt% isobutanol X'Y'Z' von Fig. 2 aufweist. and/or secondary butanol; from 5 to 35 wt% water; and less than 5 wt% isobutylene. 55 Revendications

3. The process of Claim 1 or 2 wherein the condensed 1. Procede pour la deshydratation en phase liquide mixture of tertiary butyl alcohol, water and isobuta- d'alcool de tert. butyle en isobutylene qui comprend

4 7 EP 0 712 824 B1 8

les etapes consistant a:

i) soumettre un melange reactionnel de deshydratation liquide comprenant de I'alcool de tert. butyle; isobutanol et / ou butanol secondaire; s eau; et isobutylene, les quantites relatives des composants du melange reactionnel etant effi- caces pour donner le melange condense defini en ii), a des conditions de deshydratation en phase liquide catalytiques; 10

ii) separer un melange vapeur constitue d'isobutylene, d'eau, d'alcool de tert. butyle et d'isobutanol et / ou de butanol secondaire et refroidir le melange vapeur pour condenser 15 I'alcool de tert. butyle, I'eau et I'isobutanol et / ou le butanol secondaire, le melange condense d'alcool de tert. butyle, d'eau et d'isobutanol et/ ou de butanol secondaire ayant une composition dans la zone XYZ de la Figure 2; et a recu- 20 perer I'isobutylene;

iii) effectuer une separation de phase pour I'alcool de tert. butyle condense, I'eau et I'isobutanol et / ou le butanol secondaire en une 25 phase superieure riche organique et en une phase inferieure riche en eau; et

iv) recycler la phase riche organique a I'etape de deshydratation. 30

2. Procede selon la revendication 1, dans lequel le melange reactionnel de deshydratation est constitue de 5 a 30 % en poids d'alcool de tert. butyle; de 30 a 70 % en poids d'isobutanol et / ou de butanol 35 secondaire, de 5 a 35 % en poids d'eau; et moins de 5 % en poids d'isobutylene.

3. Procede selon la revendication 1 ou 2, dans lequel le melange condense d'alcool de tert. butyle, d'eau 40 et d'isobutanol et / ou de butanol secondaire a une composition dans la zone X'Y'Z' de la Figure 2.

5 IP 0 712 824 B1