(19) TZZ¥Z_T

(11) EP 3 095 774 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.: 23.11.2016 Bulletin 2016/47 C07C 29/20 (2006.01) C07C 45/00 (2006.01) B01J 8/06 (2006.01) (21) Application number: 15168940.3

(22) Date of filing: 22.05.2015

(84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • TINGE, Johan Thomas GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO 6135 KR Sittard (NL) PL PT RO RS SE SI SK SM TR • MARTENS, Wilhelmus Rudolf Maria Designated Extension States: 6135 KR Sittard (NL) BA ME Designated Validation States: (74) Representative: Cohausz & Florack MA Patent- & Rechtsanwälte Partnerschaftsgesellschaft mbB (71) Applicant: CAP III B.V. Bleichstraße 14 6135 KR Sittard (NL) 40211 Düsseldorf (DE)

(54) A PROCESS FOR THE PRODUCTION OF A MIXTURE COMPRISING CYCLOHEXANONE AND CYCLOHEXANOL

(57) Acontinuous processfor the productionof a mix- for the hydrogenation of benzene; a chemical plant suit- ture comprising cyclohexanone and cyclohexanol by hy- able for the hydrogenation of phenol comprising a mul- drogenation of phenol, which process is performed in a ti-tubular reactor; cyclohexanone prepared in a chemical chemical plant comprising a multi-tubular reactor char- plant comprising a multi-tubular reactor; and a process acterised in that said multi-tubular reactor has been used for constructing such a plant. EP 3 095 774 A1

Printed by Jouve, 75001 PARIS (FR) 1 EP 3 095 774 A1 2

Description cyclohexane product (99.5% or higher) the effluent of the first benzene hydrogenation reactor is often, optionally [0001] The present invention relates to a continuous after cooling, fed to a second benzene hydrogenation process for the production of a mixture comprising cy- reactor. clohexanone and cyclohexanol by hydrogenation of phe- 5 [0004] Typically, the first benzene hydrogenation re- nol, which process is performed in a chemical plant com- actor is a (vertical) multi-tubular catalytic reactor with cat- prising a multi-tubular reactor; to such a chemical plant alytic material arranged in the tubes and a coolant which in which the reactor is applied; to the cyclohexanone that circulates externally around the tubes, that is fed with a is produced in such process; and to a process for con- gaseous mixture comprising hydrogen and benzene. In structing such a plant. 10 this first reactor the vast majority of the fed benzene is [0002] Cyclohexanone is an intermediate in the pro- converted into cyclohexane. Heat of reaction is removed duction of, amongst other compounds, adipic acid and by indirect cooling with a coolant. In general, the coolant caprolactam. These are monomers commonly used in is a liquid, which is optionally evaporated. In case liquid the production of polyamide-6,6 and polyamide-6, re- water is applied as coolant then steam is optionally ob- spectively. A major process for the production of cy-15 tained by evaporation of liquid water within the shell of clohexanone for use in producing caprolactam is based the reactor. As used herein, a coolant is a heat carrier on selective oxidation of cyclohexane, using atmospheric that is used for cooling purposes. oxygen. Oxidation of cyclohexane yields a mixture of cy- [0005] One alternative process for the production of clohexanol and cyclohexanone and the precursor cy- cyclohexanone is by the catalytic reduction of phenol with clohexyl hydroperoxide which is then thermally and/or 20 hydrogen, for example using a palladium-comprising het- catalytically decomposed to produce additional cy- erogeneous catalyst. The reduction of phenol with hy- clohexanol and cyclohexanone, and a variety of by-prod- drogen can be performed in the vapour phase (also often ucts. Cyclohexanone may be separated by distillation called: gas phase) or in the liquid phase, described in, from the mixture comprising cyclohexanol, cyclohex- for example, Musser. The hydrogenation of phenol is anone, unreacted cyclohexane and by-products. Cy-25 known to be highly exothermic. A mixture comprising cy- clohexanol may also be recovered by distillation and op- clohexanol, cyclohexanone, unreacted phenol and by- tionally converted to cyclohexanone by dehydrogena- products is produced. Separation of cyclohexanone from tion. Chemical processes for the production of cyclohex- this mixture may be made by distillation. Cyclohexanol anone and cyclohexanol by oxidation of cyclohexane are may also be recovered by distillation and optionally con- known in the art (see for example Michael Tuttle Musser; 30 verted to cyclohexanone by dehydrogenation. Unreacted Cyclohexanol and Cyclohexanone in Ullmann’s Encyclo- phenol is removed by distillation and recycled in the proc- pedia of Industrial Chemistry Published Online: 15 OCT ess. 2011 DOI: 10.1002/14356007.a08_217.pub2 Copyright [0006] Typically, a phenol hydrogenation reactor is a © 2002 by Wiley-VCH Verlag GmbH & Co. KGaA) (Muss- (vertical) multi-tubular catalytic reactor with catalytic ma- er). 35 terial in the tubes and a coolant which circulates exter- [0003] Typically, cyclohexane is produced from hydro- nally around the tubes, that is fed with a gaseous mixture genation of benzene. Hydrogenation of benzene to cy- comprising hydrogen and phenol. In this reactor the vast clohexane can be carried out in the vapour phase (also majority of the fed phenol is converted into cyclohex- often called: gas phase) or in the liquid phase, in the anone. Heat of reaction is removed by indirect cooling presence of catalytic material and hydrogen. In general, 40 with a coolant. In general, the coolant is a liquid, which in these hydrogenation processes a heterogeneous cat- is optionally evaporated. In case liquid water is applied alyst is used, for example Raney nickel or a supported as coolant then steam is optionally obtained by evapo- catalyst with nickel, palladium, or platinum as catalytic ration of liquid water within the shell of the reactor. The material. The hydrogenation of benzene to cyclohexane reactor temperature is generally controlled to be in the is known to be highly exothermic. High temperatures can 45 range of from 100 to 250°C. lead to thermodynamic limitations on benzene conver- [0007] Chemical plants for the production of a mixture sion, thermal cracking and increased by-product forma- comprising cyclohexanone and cyclohexanol by reduc- tion and because of that the reactor temperature is gen- tion of phenol, and chemical plants for the production of erally controlled to be in the range of from 150 to 350°C. cyclohexane by reduction of benzene are known in the Present industrial processes for the production of cy- 50 art, also described in, for example, Musser. The starting clohexane through the catalytic hydrogenation of ben- materials, intermediates, products, by-products and cat- zene differ principally in their methods for the removal of alysts used in such a plant for the production of a mixture the heat of reaction. This is done by indirect cooling with comprising cyclohexanone and cyclohexanol based on a liquid in a jacketed reactor; or by vaporization of feed hydrogenation ofphenol are vastly different tothose used and recycle of product in a vapour phase, or by a multi- 55 in a plant for the production of cyclohexane based on reactor process with intercooling between reactors. Still hydrogenation of benzene. Accordingly, the apparatus another process uses a catalyst slurry with a liquid pump- required for the hydrogenation of phenol is different to around for indirect cooling. In order to produce high purity that required for the hydrogenation of benzene.

2 3 EP 3 095 774 A1 4

[0008] Nowadays, due to severe reduction of the phe- sumption per unit weight of cyclohexanone produced nol price compared to the benzene price, the process for may be reduced. the production of a mixture comprising cyclohexanone [0013] Typical carbon efficiency of hydrogenation of and cyclohexanol by reduction of phenol with hydrogen phenol to cyclohexanone is higher than 98 % and in gen- is more economic regarding raw materials costs and en- 5 eral even higher than 99 %, while the carbon efficiency ergy costs than the process for producing a mixture com- of oxidation of cyclohexane to cyclohexanone is typically prising cyclohexanone and cyclohexanol by the hydro- from 75 % to 90 %. A yet further advantage of operating genation of benzene followed by the oxidation of the ob- a plant according to the present invention is that less tained cyclohexane. So, for current producers of mixtures starting material is required to produce a given amount of cyclohexanone and cyclohexanol that apply the proc- 10 of cyclohexanone. Further, the amount of by-products ess of hydrogenation of benzene followed by the oxida- and therefore waste produced per unit weight of cy- tion of the obtained cyclohexane it is advantageous to clohexanone produced may be reduced. switch to the process of producing a mixture comprising [0014] The production of cyclohexanone by the oxida- cyclohexanone and cyclohexanol by hydrogenation of tion of cyclohexane is typically subject to stringent safety phenol. An option for switching to the process based on 15 regulations because of the risk of ignition of explosive the hydrogenation of phenol is to build a new plant. A cyclohexane-oxygen mixtures, for example a large safety major drawback of this approach are the high investment circle must be in place. Yet, a further advantage of the costs for such a new plant. In particular a reactor suitable process of the present invention is that the risk of explo- for the hydrogenation of phenol is typically complex and sion of cyclohexane-oxygen mixtures is avoided, be- therefore expensive. 20 cause no cyclohexane is used in the process of the plant [0009] The present inventors have discovered a meth- for the hydrogenation of phenol. Thus the associated od to significantly reduce the investment costs of a plant safety measures are not required. for the production of a mixture comprising cyclohexanone [0015] The present invention therefore also provides and cyclohexanol based on the reduction of phenol. They a chemical plant suitable for the production of a mixture have developed a process for the production of a mixture 25 comprising cyclohexanone and cyclohexanol by hydro- comprising cyclohexanone and cyclohexanol by hydro- genation of phenol, which chemical plant comprises a genationof phenol; basedon theequipment of a chemical multi-tubular reactor characterised in that said multi-tu- plant used to produce a mixture comprising cyclohexane bular reactor has been used for the hydrogenation of ben- from the hydrogenation of benzene. More specifically, zene. the present invention provides a continuous process for 30 [0016] Typically, in the process of the present invention the production of a mixture comprising cyclohexanone said chemical plant for the hydrogenation of phenol com- and cyclohexanol by hydrogenation of phenol, which prises one or more of the following units: a partial con- process is performed in a chemical plant comprising a denser unit suitable for condensing cyclohexanol and cy- multi-tubular reactor characterised in that said multi-tu- clohexanone from the gaseous mixture comprising cy- bular reactorhas been used for thehydrogenation ofben- 35 clohexanone and cyclohexanol, a distillation column suit- zene. able for distilling overhead components having a lower [0010] Such a process is useful to a company which boiling point than cyclohexanone, a distillation column operates a plant for the hydrogenation of benzene to from suitable for the separation of cyclohexanone with a purity cyclohexane, who wishes to discontinue use of such of more than 99 wt.%, a distillation column suitable for plant. It is also useful to a company who wishes to con- 40 distilling overhead components having a higher boiling struct a plant for the production of a mixture comprising pointthan cyclohexanone, acyclohexanol hydrogenation cyclohexanone and cyclohexanol. reactor, wherein cyclohexanol is converted into cy- [0011] As used herein, "has been used" includes that clohexanone and hydrogen. the multi-tubular reactor was designed for the hydrogen- [0017] Typically, in the chemical plant of the present ation of benzene and/or installed in a plant for the hydro- 45 invention the chemical plant further comprises a distilla- genation of benzene. tion column suitable for the separation of cyclohexanone [0012] Processes based on oxidation of cyclohexane from a mixture of cyclohexanone and cyclohexanol with to produce essentially pure cyclohexanone are known to a purity of more than 99 wt.%. consume large amounts of energy, typically supplied in- [0018] The present invention further provides cy- dustrially as steam and electricity. Specific steam con- 50 clohexanone prepared in a chemical plant, in which sumptions of more than 5 tons of steam per ton of purified chemical plant a mixture comprising cyclohexanone and cyclohexanone are known. Large quantities of steam are cyclohexanol is produced through a continuous process consumed in heating cyclohexane fed to the (first) oxi- for the hydrogenation of phenol, which chemical plant dation reactor; the removal of unreacted cyclohexane, comprises a multi-tubular reactor characterised in that distillative purification of cyclohexane and the dehydro- 55 said multi-tubular reactor has been used for the hydro- genation of cyclohexanol. A further advantage of a proc- genation of benzene. ess of constructing a plant to carry out a different process [0019] A chemical plant includes all apparatus neces- according to the present invention is that the energy con- sary to manufacture or otherwise process the chemicals

3 5 EP 3 095 774 A1 6 desired. This includes units for one or multiple chemical nylcyclohexanol, 4-phenylcyclohexanol, cyclohexyl phe- or physical operations, for example, heating up, cooling nylether, benzofuran, 2,3-dimethylbenzofuran, 3-methyl- down, mixing, distillation, extraction and reaction. It in- 4-octanone, 4-methyl-3-octanone, 3-methyl-3-oc- cludes all auxiliary equipment, for example reflux units, tanone, methyl-isopropylcyclohexanol, methyl-isopro- coolant supply, pumps, heat exchangers and pipework. 5 pylcyclohexanone and 1-(4-methylpentane-2-yl)-ben- The exact apparatus depends amongst others on type zene-phenol. and purity of the starting material(s) and the desired end [0026] Typically, in the process of the present invention product(s), but also on the scale and type of process. the molar ratio of cyclohexanone to cyclohexanol in the [0020] By a continuous process for the hydrogenation mixture comprising cyclohexanone and cyclohexanol of phenol is meant a process in which phenol and hydro- 10 that is produced is more than 4 to 1. Preferably, the molar gen are fed without interruption and whereby a hydro- ratio of cyclohexanone to cyclohexanol in the mixture genated product or a mixture of hydrogenated products comprising cyclohexanone and cyclohexanol that is pro- of phenol are withdrawn without interruption. A continu- duced is more than 6 to 1. More preferably, the molar ous process for the hydrogenation of phenol may be at ratio is more than 10 to 1; yet more preferably, the molar a constant rate or may fluctuate in rate over time. A con- 15 ratio is more than 15 to 1. tinuous process for the hydrogenation of phenol may be [0027] Typically, in the process of the present invention interrupted for a certain period of time due to e.g. a proc- cyclohexanone is separated from the mixture comprising ess disturbance, a maintenance activity, or for economic cyclohexanone and cyclohexanol that is produced. More reasons. preferably, cyclohexanone with a purity of more than 90 [0021] The chemical plant is preferably of industrial 20 wt.% is separated; even more preferably, cyclohexanone scale. By industrial scale is meant a hydrogenation rate with a purity of more than 98 wt.% is separated. Typically, of phenol of at least 1,000 kg of phenol per hour; more the separation of cyclohexanone is performed by distil- preferably, at least 2,000 kg of phenol hour; even more lation, crystallization, extraction and/or a combination preferably, at least 4,000 kg of phenol per hour; and most thereof. preferably, at least 6,000 kg of phenol hour. 25 [0028] Typically, in the process of the present invention [0022] By hydrogenation of benzene is meant that ben- from the mixture comprising cyclohexanone and cy- zene and hydrogen are partly or completely converted clohexanol that is produced, cyclohexanone with a purity and whereby a hydrogenated product or a mixture of hy- of more than 99 wt.% is separated by distillation. drogenated products of benzene are formed. [0029] Typically, the hydrogenation of phenol whereby [0023] As used herein, a mixture comprising cyclohex- 30 a mixture comprising cyclohexanone and cyclohexanol anone and cyclohexanol that is produced in a process is produced is performed in a chemical plant comprising for the hydrogenation of phenol is the mixture of com- a multi-tubular reactor. The number of reactor tubes in pounds resulting from the hydrogenation of phenol. Typ- the multi-tubular reactor is typically more than 5. Prefer- ically, this comprises cyclohexanone, cyclohexanol, at ably, it is more than 10. More preferably, it is more than least one characteristic by-product and (unreacted) phe- 35 25. The number of reactor tubes is typically less than nol. The phenol content of this mixture is typically at least 100,000. Preferably, it is less than 50,000. More prefer- 0.02 wt.%. Preferably, it is at least 0.03 wt.%; more pref- ably, it is less than 20,000. erably, at least 0.1 wt.%. The phenol content is prefera- [0030] Typically, in the process of the present invention bly, less than 50 wt.%; more preferably, less than 20 the number of reactor tubes in said multi-tubular reactor wt.%; most preferably, less than 10 wt.%. The mixture is 40 is from 25 to 20,000. typically gaseous. [0031] The internal diameter of the shell of the multi- [0024] Typically, the mixture comprising cyclohex- tubular reactor is typically more than 50 mm. Preferably, anone and cyclohexanol that is produced comprises one it is more than 100 mm. More preferably, it is more than or more of the following components: phenol, 2-phenyl- 200 mm. The internal diameter of the shell of the multi- cyclohexanol, 3-phenylcyclohexanol, 4-phenylcyclohex- 45 tubular reactor is typically less than 10 m. Preferably, it anol, cyclohexyl phenylether, benzofuran, 2,3-dimethyl- is less than 8 m. More preferably, it is less than 6 m. benzofuran, 3-methyl-4-octanone, 4-methyl-3-oc- [0032] Typically, in the process of the present invention tanone, 3-methyl-3-octanone, methyl-isopropylcy- the internal diameter of the shell of said multi-tubular re- clohexanol, methyl-isopropylcyclohexanone and 1-(4- actor is from 0.2 to 6 m. methylpentane-2-yl)-benzene-phenol. In addition , the 50 [0033] The internal diameter of the reactor tubes is typ- gaseous mixture comprising cyclohexanone and cy- ically more than 2 mm. Preferably, it is more than 5 mm. clohexanol that is produced might also comprise (uncon- More preferably, it is more than 10 mm. The internal di- verted) hydrogen and inert components like nitrogen and ameter of the reactor tubes is typically less than 500 mm. methane. Preferably, it is less than 250 mm. More preferably, it is [0025] Typically, in the process of the present invention 55 less than 120 mm. the mixture comprising cyclohexanone and cyclohexanol [0034] Typically, in the process of the present invention that is produced also comprises phenol and at least one the internal diameter of the reactor tubes in said multi- compound selected from 2-phenylcyclohexanol, 3-phe- tubular reactor is from 10 to 120 mm. Preferably, all re-

4 7 EP 3 095 774 A1 8 actor tubes in the multi-tubular reactor have (almost) the the hydrogenation is carried out in the presence of a sup- same internal diameter. ported palladium catalyst. [0035] In the tubes in the multi-tubular reactor heat is [0044] The support may in principle be any support ca- generated due to hydrogenation of phenol, thereby heat- pable of supporting one or more catalytically active met- ing up the mixture of components in the tubes. Heat of 5 als for the hydrogenation of phenol. Suitable supports in the mixture of components is removed by indirect cooling particular may be selected from the group of alumina, witha coolant. The temperatureof themixture comprising activated carbon, titanium oxide, calcium carbonate and cyclohexanone and cyclohexanol that is discharged from carbon black. Another support that may be used is silica. the multi-tubular reactor is typically more than 60 °C. Pref- [0045] Typically, in the process of the present invention erably, it is more than 80 °C. More preferably, it is more 10 the hydrogenation is carried out in the presence of a sup- than 100 °C. The temperature of the mixture comprising ported palladium catalyst. cyclohexanone and cyclohexanol that is discharged from [0046] In general, the per pass conversion of phenol the multi-tubular reactor is typically less than 260 °C. in the reaction unit is more than 90 %. Optionally, unre- Preferably, it is less than 240 °C. More preferably, it is acted hydrogen gas and inerts are separated off from the less than 220 °C. 15 reaction mixture. Usually, unreacted hydrogen gas is re- [0036] Typically, in the process of the present invention used in the phenol hydrogenation process. the temperature of the mixture comprising cyclohex- [0047] As used herein, the meaning of an "essentially anone and cyclohexanol that is discharged from the mul- pure" component is that the content of the component is ti-tubular reactor is from 100 to 220 °C. at least 98 wt.%. Preferably, it is at least 99 wt.%; more [0037] Typically, in a multi-tubular reactor wherein20 preferably, at least 99.5 wt.%; even more preferably, at phenol is hydrogenated heat is removed by a coolant. least 99.9 wt.%. Usually, as coolant aqueous or organic solvents or mix- tures thereof are applied. Typically, in the process of the FIG. 1 shows a plant for the production of cyclohex- present invention water is applied as coolant in the multi- ane. tubular reactor. 25 FIG. 2 shows a plant according to the present inven- [0038] By absorbing heat the coolant that is charged tion, for the production of cyclohexanone. to the multi-tubular reactor is heated up, evaporated (partly or completely) or a combination thereof. Prefera- [0048] FIG. 1 shows a plant for the production of cy- bly, at least 10 wt.% of the coolant that is charged to the clohexane by first hydrogenating benzene in the vapour multi-tubular reactor is evaporated. More preferably, at 30 phase to form a hydrogenated mixture and then separat- least 50 wt.%. Even more preferably, at least 90 wt.%. ing a hydrogen-comprising flow from the hydrogenated [0039] Typically, in the process of the present invention mixture. The benzene hydrogenation is carried out in a water is applied as coolant in the multi-tubular reactor two-reactors-in-series process with as first hydrogena- and more than 90 wt.% of the water evaporated. tion reactor a multi-tubular reactor. [0040] The hydrogenation of phenol with hydrogen can 35 [0049] Gaseous benzene is fed to the first hydrogen- be performed in the gas phase or in the liquid phase. ation unit [A] through line [1]. The first hydrogenation unit Preferably, the hydrogenation of phenol with hydrogen [A] comprises one or more multi-tubular reactors with is performed in the gas phase. Typically, a process for benzene hydrogenation catalyst inside the tubes and in- the hydrogenation of phenol that is performed in the gas direct cooling with a coolant. Coolant is fed through line phase is charged with a gaseous mixture comprising the 40 [a] and after being heated discharged through line [b]. raw materials phenol and hydrogen as feed. Preferably, Hydrogen gas is fed through line [2]. The resulting gas- the phenol content of the mixture comprising the raw ma- eous first hydrogenated mixture which comprises cy- terials phenol and hydrogen that is charged as feed to clohexane and unconverted benzene is fed through line the multi-tubular reactor is at least 5 wt.%. More prefer- [3] to the second hydrogenation unit [B]. Optionally, this ably, at least 15 wt.%. Even more preferably, at least 25 45 mixture is cooled before being fed to the second hydro- wt.%. genation unit [B] (not shown in FIG. 1). Optionally, addi- [0041] Typically, in the process of the present invention tional hydrogen is fed to the second hydrogenation unit a mixture comprising phenol and hydrogen, in which the [B] (not shown in FIG. 1). In the second hydrogenation phenol content is more than 25 wt.%, is charged as feed unit [B] unconverted benzene is hydrogenated into cy- to the multi-tubular reactor. 50 clohexane. The second hydrogenation unit [B] comprises [0042] The hydrogenation catalyst may in principle be one or more benzene hydrogenation reactors. Optional- any (supported) hydrogenation catalyst capable of cata- ly, the second hydrogenation unit [B] is cooled (not shown lysing the hydrogenation of phenol. Usually, the catalyst in FIG. 1). The gaseous second hydrogenated mixture comprises one or more catalytically active metals select- is removed to hydrogen separation unit [C] through line ed from palladium, platinum, ruthenium, rhodium, iridium, 55 [4]. From hydrogen separation unit [C] a gaseous hydro- rubidium and osmium. Palladium, platinum or a combi- gen-comprising flow and a cyclohexane-comprising flow nation thereof are preferred catalytically active metals. are separately discharged through line [5] and line [6], [0043] Typically, in the process of the present invention respectively. Hydrogen separation unit [C] might com-

5 9 EP 3 095 774 A1 10 prise a partial condensation unit and one or more distil- chemical plant of FIG. 1 when constructing the chemical lation units. Optionally, the gaseous hydrogen-compris- plant of FIG. 2: lights distillation column [E] together with ing flow discharged through line [5] is fed to the first hy- input line [16] from cyclohexanol dehydrogenation unit drogenation unit [A] (not shown in FIG. 1). [H] and output lines [10] and [11]; and cyclohexanone [0050] Optionally, the cyclohexane discharged5 distillation column [F] together with output lines [12] and through line [6] is fed to cyclohexanone plant based on [13]; and cyclohexanol distillation column [G] together oxidation of cyclohexane (not shown in FIG. 1). with output lines [14] and [15]; cyclohexanol dehydrogen- [0051] FIG. 2 shows a plant according to the present ation unit [H]; phenol distillation unit [I] together with out- invention, for the production of cyclohexanone by first put lines [17] and [18]. Output line [18] is connected to hydrogenating phenol in the vapour phase, then sepa- 10 first hydrogenation unit [A]. Input line [7] is connected to rating cyclohexanone from the resulting mixture compris- the first hydrogenation unit [A]. Input line [8] (feed of hy- ing cyclohexanol and cyclohexanone and finally dehy- drogen gas) is connected to the first hydrogenation unit drogenating cyclohexanol into cyclohexanone. [A]. Input line [8] may be identical to input line [2] of FIG. [0052] Fresh phenol is fed via line [7], hydrogen gas is 1. Accordingly, input line [2] needs not to be replaced. fed through line [8] and a mixture comprising phenol that 15 The benzene hydrogenation catalyst inside the tubes of is distilled overhead in phenol distillation column [I] is fed the more multi-tubular reactor(s) has to be replaced by through line [18] to first hydrogenation unit [A]. First hy- phenol hydrogenation catalyst. drogenation unit [A] comprises one or more multi-tubular [0054] The present invention therefore also provides reactors with phenol hydrogenation catalyst inside the a process for the construction of a chemical plant suitable tubes and indirect cooling with a coolant. Coolant is fed 20 for the production of a mixture comprising cyclohexanone through line [a] and after being heated discharged and cyclohexanol by hydrogenation of phenol, said proc- through line [b]. The resulting mixture of reaction prod- ess comprising: ucts, comprising phenol, cyclohexanol and cyclohex- anone is fed through line [9] to lights distillation column a) disconnecting a multi-tubular reactor suitable for [E]. Optionally, unreacted hydrogen gas and inert gases 25 producing cyclohexane by the hydrogenation of ben- are separated from this mixture (not shown in FIG. 2). A zene from a chemical plant, which plant is suitable mixture of components with boiling points below that of for the production of a mixture comprising cyclohex- cyclohexanone is distilled overhead and removed anone and cyclohexanol by hydrogenation of ben- through line [10]. The bottom product is fed through line zene to form cyclohexane followed by oxidation of [11] to cyclohexanone distillation column [F], where cy- 30 said cyclohexane; and clohexanone is distilled overhead through line [12]. The b) connecting said multi-tubular reactor to said bottom product is fed through line [13] to cyclohexanol chemical plant suitable for the production of a mix- distillation column [G], where a mixture comprising cy- ture comprising cyclohexanone and cyclohexanol by clohexanol and cyclohexanone is distilled overhead and hydrogenation of phenol. passed through line [14] to cyclohexanol dehydrogena- 35 tion unit [H]. Cyclohexanol dehydrogenation unit [H] com- [0055] The present invention is illustrated by, but not prises one or more cyclohexanol dehydrogenation reac- intended to be limited to, the following examples. tors. The resulting mixture comprising cyclohexanone is, after separating of hydrogen gas (not shown in FIG. 2), COMPARATIVE EXPERIMENTA recycled through line [16] to lights distillation column [E]. 40 Optionally, this hydrogen gas is charged to hydrogena- [0056] A continuous process for the production of cy- tion unit [A] (not shown in FIG. 2). The bottom product of clohexane by hydrogenation of benzene was performed [G] comprising phenol is removed through line [15]. Line for a series of years in a chemical plant, comprising: [15] leads to phenol distillation column [I] where a mixture comprising phenol is distilled overhead and fed through 45 - a first hydrogenation unit; line [18] to first hydrogenation unit [A]. The bottom prod- - a second hydrogenation unit; uct is removed from phenol distillation column [I] through - a hydrogen separation unit; line [17]. [0053] According to one embodiment of the present as described above and substantially as depicted in FIG. invention, a chemical plant according to FIG. 2 is con- 50 1. This commercial chemical plant had on average an structed from a chemical plant according to FIG. 1. From hourly output of about 6.6 metric tons of essentially pure a comparison of FIG. 2 with FIG. 1, it can be seen that cyclohexane, which is equivalent to an annual plant out- the following apparatus is disconnected from the chem- put of approximately 53 kta of essentially pure cyclohex- ical plant of FIG. 1 when constructing the chemical plant ane (assuming 8000 effective production hours per year). of FIG. 2: first hydrogenation unit [A] comprising one or 55 [0057] The hydrogenation of benzene in both the first more multi-tubular reactors and optionally hydrogen gas and second hydrogenation unit was performed with 0.3 feed [2]. Further, the following equipment is connected wt.% Pt/Al2O3 as catalyst. In the first hydrogenation unit to the first hydrogenation unit [A] disconnected from the the conversion of benzene into cyclohexane was already

6 11 EP 3 095 774 A1 12 over 99 %. In the second hydrogenation unit most of the cyclohexanone that was distilled overhead in the cy- remaining benzene was converted. clohexanone distillation column was on average about [0058] The reaction mixture exiting the second hydro- 500 ppm by weight. The bottom flow from the cyclohex- genation unit was cooled down and hydrogen gas was anone distillation column was fed to the cyclohexanol separated from this reaction mixture and the resulting 5 distillation column, where a mixture comprising mainly cyclohexane-comprising flow was used for the produc- cyclohexanol was distilled overhead. This mixture com- tion of cyclohexanone via a cyclohexanone oxidation prising mainly cyclohexanol was fed to the cyclohexanol process. dehydrogenation unit, in which cyclohexanol was con- [0059] The first hydrogenation unit contained one ver- verted into cyclohexanone. Hydrogen gas formed was tical multi-tubular reactor with benzene hydrogenation 10 separated therefrom. The resulting reaction mixture was catalyst inside the tubes and had indirect cooling with a then fed to the lights distillation column. coolant for removal of heat. The vertical multi-tubular re- [0064] The bottom flow of the cyclohexanol distillation actor had an internal diameter of about 2.2 m, containing column was fed to a phenol distillation column where 3528 tubes, each of which have a length of 4 m and an heavies were separated from a mixture comprising main- internal diameter of about 21.4 mm. 15 ly cyclohexanol and phenol. In the cyclohexanol distilla- tion column a mixture comprising phenol was distilled EXAMPLE 1 overhead and fed to the first hydrogenation unit. [0065] Three months after start-up of the plant the fol- [0060] In Example 1 (according to the invention), the lowing results could be obtained: vertical multi-tubular reactor in the first hydrogenation 20 unit, was the same as the vertical multi-tubular reactor The gaseous feed rate charged to the vertical multi- in the first hydrogenation unit in Comparative Experiment tubular reactor in the first hydrogenation unit was A. about 15.3 ton/hr, comprising phenol, hydrogen, ni- [0061] A chemical plant for the production of cyclohex- trogen, cyclohexanol, cyclohexanone and water. anone by hydrogenation of phenol, comprising: 25 The phenol content of this gaseous feed was about 50 wt.%. - a first hydrogenation unit; - a lights distillation column; [0066] A gaseous mixture comprising cyclohexanone - a cyclohexanone distillation column; and cyclohexanol that was produced was discharged - a cyclohexanol distillation column; 30 from the vertical multi-tubular reactor in the first hydro- - a phenol distillation column; and genation unit at a temperature of 183 °C. This gaseous - a cyclohexanol dehydrogenation unit; mixture also comprises phenol, 2-phenylcyclohexanol, 3-phenylcyclohexanol, 4-phenylcyclohexanol, cy- as described before and substantially as depicted in FIG. clohexyl phenylether, benzofuran, 2,3-dimethylbenzo- 2 was simulated in Aspen Plus® chemical engineering 35 furan, 3-methyl-4-octanone, 4-methyl-3-octanone, 3- software. The simulated plant was designed with an iden- methyl-3-octanone, methyl-isopropylcyclohexanol, me- tical vertical multi-tubular reactor in the first hydrogena- thyl-isopropylcyclohexanone, 1-(4-methylpentane-2- tion unit as in Comparative Experiment A. The vertical yl)-benzene-phenol, hydrogen and nitrogen. Analysis multi-tubular reactor in the first hydrogenation unit limited showed that more than 93 mol % of the phenol that was the overall capacity of the plant. 40 fed into the reactor was converted into cyclohexanone [0062] The hydrogenation of phenol in the phenol hy- and cyclohexanol. drogenation unit was performed in the gas phase in the [0067] The hydrogenation rate of phenol was about presenceof a phenol hydrogenationcatalyst. The applied (15.3 ton/hr * 50 wt.% * 93 mol % = ) 7.1 ton/hr. phenol hydrogenation catalyst was supplied by BASF (: [0068] As coolant (liquid) water was fed to the vertical 1 wt.% Pd on alumina support, with 1 wt.% Na (as45 multi-tubular reactor in the first hydrogenation unit at a NaHCO3)added as promoter). The resultinggas mixture, rate of about 4.7 ton/hr. Most of this water (more than comprising phenol, hydrogen gas, cyclohexanol and cy- 99%) left the vertical multi-tubular reactor in the first hy- clohexanone, was partially condensed by cooling and drogenation unit as steam (vapour). separated into a liquid mixture comprising phenol, cy- [0069] As top product from the cyclohexanone distilla- clohexanol and cyclohexanone that was fed to the lights 50 tion column about 7.4 ton/hr of essentially pure cyclohex- distillation column, and a gaseous flow comprising hy- anone (purity > 99.8 wt.%)was obtained. drogen. [0070] Comparison of Comparative Experiment A and [0063] In the lights distillation column, components Example 1 shows that the vertical multi-tubular reactor with boiling points lower than that of cyclohexanone were in the first hydrogenation unit used in the production of distilled overhead. The bottom flow from the lights distil- 55 cyclohexane by hydrogenation of benzene, can be re- lation column was fed to the cyclohexanone distillation used, after replacement of the catalyst, as a vertical multi- column, where essentially pure cyclohexanone was dis- tubular reactor in the first hydrogenation unit for the pro- tilled overhead. The cyclohexanol concentration in the duction of a gaseous mixture comprising cyclohexanone

7 13 EP 3 095 774 A1 14 and cyclohexanol by hydrogenation of phenol, and that methyl-3-octanone, 3-methyl-3-octanone, methyl- from this mixture essentially pure cyclohexanone can be isopropylcyclohexanol, methyl-isopropylcyclohex- obtained. anone and 1-(4-methylpentane-2-yl)-benzene-phe- nol. 5 Claims 11. A process according to any one of claims 1 to 10, wherein from the mixture comprising cyclohexanone 1. A continuous process for the production of a mixture and cyclohexanol that is produced, cyclohexanone comprising cyclohexanone and cyclohexanol by hy- with a purity of more than 99 wt.% is separated by drogenation of phenol, which process is performed 10 distillation. in a chemical plant comprising a multi-tubular reactor characterised in that said multi-tubular reactor has 12. A chemical plant suitable for the production of a mix- been used for the hydrogenation of benzene. ture comprising cyclohexanone and cyclohexanol by hydrogenation of phenol, which chemical plant com- 2. A process according to claim 1, wherein the internal 15 prises a multi-tubular reactor characterised in that diameter of the shell of said multi-tubular reactor is said multi-tubular reactor has been used for the hy- from 0.2 to 6 m. drogenation of benzene.

3. A process according to claim 1 or claim 2, wherein 13. A chemical plant according to claim 12, which chem- the number of reactor tubes in said multi-tubular re- 20 ical plant further comprises a distillation column suit- actor is from 25 to 20,000. able for the separation of cyclohexanone from a mix- ture of cyclohexanone and cyclohexanol with a purity 4. A process according to any one of claims 1 to 3, of more than 99 wt.%. wherein the internal diameter of the reactor tubes in said multi-tubular reactor is from 10 to 120 mm. 25 14. Cyclohexanone prepared in a chemical plant, in which chemical plant a mixture comprising cyclohex- 5. A process according to any one of claims 1 to 4, anone and cyclohexanol is produced through a con- wherein the temperature of the mixture comprising tinuous process for the hydrogenation of phenol, cyclohexanone and cyclohexanol that is discharged which chemical plant comprises a multi-tubular re- from the multi-tubular reactor is from 100 to 220 °C. 30 actor characterised in that said multi-tubular reac- tor has been used for the hydrogenation of benzene. 6. A process according to any one of claims 1 to 5, wherein the hydrogenation is carried out in the pres- 15. A process for the construction of a chemical plant ence of a supported palladium catalyst. suitable for the production of a mixture comprising 35 cyclohexanone and cyclohexanol by hydrogenation 7. A process according to any one of claims 1 to 6, of phenol, said process comprising: wherein water is applied as coolant in the multi-tu- bular reactor and more than 90 wt.% of the water is a) disconnecting a multi-tubular reactor suitable evaporated. for producing cyclohexane by the hydrogenation 40 of benzene from a chemical plant, which plant 8. A process according to any one of claims 1 to 7, is suitable for the production of a mixture com- wherein a mixture comprising phenol and hydrogen, prising cyclohexanone and cyclohexanol by hy- in which the phenol content is more than 25 wt.%, is drogenation of benzene to form cyclohexane fol- charged as feed to the multi-tubular reactor. lowed by oxidation of said cyclohexane; and 45 b) connecting said multi-tubular reactor to said 9. A process according to any one of claims 1 to 8, chemical plant suitable for the production of a wherein the molar ratio of cyclohexanone to cy- mixture comprising cyclohexanone and cy- clohexanol in the mixture comprising cyclohexanone clohexanol by hydrogenation of phenol. and cyclohexanol that is produced is more than 4 to 1. 50

10. A process according to any one of claims 1 to 9, wherein the mixture comprising cyclohexanone and cyclohexanol that is produced also comprises phe- nol and at least one compound selected from 2-phe- 55 nylcyclohexanol, 3-phenylcyclohexanol, 4-phenyl- cyclohexanol, cyclohexyl phenylether, benzofuran, 2,3-dimethylbenzofuran, 3-methyl-4-octanone, 4-

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Non-patent literature cited in the description

• Cyclohexanol and Cyclohexanone. MICHAEL TUT- TLE MUSSER. Ullmann’s Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA, 15 October 2011 [0002]

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