WO2014163506A1

WO2014163506A1 - Process to prepare epsilon-caprolactam

Info

Publication number: WO2014163506A1
Application number: PCT/NL2014/050219
Authority: WO
Inventors: Saeed RAOUFMOGHADDAM; Eit Drent; Elisabeth Bouwman
Original assignee: Universiteit Leiden
Priority date: 2013-04-05
Filing date: 2014-04-07
Publication date: 2014-10-09

Abstract

The invention is directed to a process to prepare ε-caprolactam and/or unsaturated ε-caprolactam from a pentenamide by contacting the pentenamide with a mixture of hydrogen and carbon monoxide in the presence of a solvent and a catalyst system comprising of a Group 8-10 metal and a phosphorus-donor ligand. The ligand may be a xantphos-type ligand.

Description

PROCESS TO PREPARE ε-CAPRO LACTAM

The invention is directed to a process to prepare ε-caprolactam.

Various processes are known to prepare ε-caprolactam. The processes which are applied commercially uses either cyclohexane, obtained from benzene, or phenol as feedstock. These compounds are converted to cyclohexanone oxime, which in turn is converted via a process as known as the Beckmann rearrangement to ε-caprolactam. The reaction is partly performed in a solution of oleum and sulfuric acid. Ammonium sulfate is produced as a by-product.

Various alternative routes to ε-caprolactam have been developed over the years which would not have the disadvantage of the ammonium sulfate production and/or the use of oleum and sulfuric acid. One of these routes is described in

EP1251 122. The process involves a carbonylation of butadiene in the presence of an alkanol to produce an alkyl-pentenoate, optionally isomerising any alkyl-3- and/or alkyl-2-pentenoate into alkyl-4-pentenoate, a hydroformylation of the alkyl- pentenoate to produce alkyl-5-formylvalerate, a reductive amination of the alkyl-5- formylvalerate in the presence of a hydrogenation catalyst to produce caprolactam and caprolactam precursors and optionally converting epsilon-caprolactam

precursors at elevated temperature into epsilon-caprolactam.

An object of the present invention is to provide a further, highly selective and environmetally friendly alternative process for preparing ε-caprolactam.

This and other objectives have at least in part been achieved.

Accordingly, the present invention relates to a process to prepare ε- caprolactam and/or unsaturated ε-caprolactam from a pentenamide, by contacting the pentenamide with a mixture of hydrogen and carbon monoxide in the presence of a solvent and a catalyst system comprising of a Group 8-10 metal and a phosphorus- donor ligand.

Applicants found that it is possible to prepare ε-caprolactam and/or unsaturated ε-caprolactam from a pentenamide with a high yield. Applicants further found that the pentenamide can be simply prepared from an alkyl pentenoate. The invention is therefore also directed to a process to prepare ε-caprolactam from an alkyl pentenoate by

(a) amidation of an alkyl pentenoate to obtain a pentenamide and (b) intramolecular hydoamidomethylation of the pentenamide to ε- caprolactam and/or unsaturated ε-caprolactam followed by an optional hydrogenation of any unsaturated ε-caprolactam as may be obtained.

The invention is further directed to the use of a pentenamide as a feedstock to prepare ε-caprolactam. Applicants believe that they are the first who have been able to prepare ε-caprolactam starting from a pentenamide.

While A. L. Roes and M.K. Patel, J. Cleaner Prod., 201 1 19(14), 1659-67, disclose the hydroamidomethylation of 1 -pentene in the presence of rhodium to form N-hexylacetamide, using p-toluenesulfonic or phosphoric acid as cocatalysts. The publication, which reviews a prospective, "ex ante" research programme, proposes that the same reaction may eventually be used for the preparation of ε-caprolactam from pentenamide. However, this requires a yet-to-be discovered catalyst and a yet- to-be discovered two step reaction scheme. The publication also discloses that the novel, i.e. yet undiscovered process is uncertain, hence making it impossible to foresee whether it may have clear advantages over known petrochemical routes, clearly indicating that it factually only postulates such a process, without any disclosure that a skilled artisan may find useful.

Saeed Raoufmoghaddam, Eite Drent, and Elisabeth Bouwman, Adv. Syn. Catal., 2013, 355(4), 717-33, disclose the use of various rhodium-based catalyst systems in the intermolecular catalytic reductive amidation of hexanal with

acetamide. The reaction yields a mixture of N-hexylacetamide, two isomeric unsaturated intermediates and hexanol. The publication proposes that a catalytic reductive amidation reaction may eventually be employed to prepare primary amines after subsequent hydrolysis of the resulting N-alkylamide, and indicates that the ultimate, but undisclosed goal of the research project is to eventually being able to combine the disclosed reductive amidation reaction with an in situ formation of the aldehyde by hydroformylation of alkenes.

The invention shall now be described in more detail. The phosphorus-donor ligand may be a monodentate ligand, a bidentate ligand or even a multidentate ligand or mixtures thereof. The ligands may be a monodentate phosphine ligand, a monodentate phosphite ligand, a bidentate diphosphine, a bidentate diphosphite ligand, a mixed nitrogen-phosphine ligand or a mixed oxygen-phosphine ligand. Examples of suitable monodentate phosphine ligands are triphenylphosphine, tris(n- butyl)phosphine, and bis(1 -adamantyl)-n-butylphosphine. Examples of suitable monodentate phosphite ligands are triphenylphosphite and tris-(2,4-di-t- butylphenyl)phosphite. Suitable multidentate phosphite ligands are for example disclosed in WO-A-9518089, the disclosure of which is incorporated herein by reference. Suitable bidentate phosphine ligands are described in WO-A-9733854, the disclosure of which is incorporated herein by reference. An example of a suitable mixed nitrogen-phosphine ligand is N-methyl-2-imidazolyl-biscyclohexylphosphine.

Preferably a bidentate diphosphine ligand is used. The bidentate diphosphine ligand preferably has an organic bridging group bridging the two phosphorus atoms. The bridging group preferably comprises a chain of atoms forming the shortest link between the two phosphorus atoms consisting of 4 or 5 atoms, preferably 5 atoms. The atoms in this chain may be carbon, oxygen or nitrogen atoms. A suitable bridging group is the bridging group of a xantphos-type ligand. The chain of this ligand consists of 2 groups of 2 carbon atoms linked by one oxygen atom. Applicants also found that the bridging group is preferably a so-called rigid bridging group, which results in a defined bite angle of the bidentate ligand.

Ligands having a bite angle comparable to xantphos-type ligand are preferably used. More preferably the bidentate diphosphine ligand is a xantphos-type ligand.

For the purposes of the present invention, the term "xantphos ligand" generally refers to a compound of the general formula I,

wherein the subsitutents R¹ , R², R³ and R⁴ at the phosphorus atoms are each independently selected from the group containing, preferably consisting of, phenyl, tert-butyl and isopropyl, and wherein A is selected from the group comprising, preferably consisting of, -C(CH₃)₂-, -CH₂CH₂-, -Si(CH₃)₂-, -S-, -0-, and -C(C(CH₃)₂)-. Preferably R¹ , R², R³ and R⁴ represent phenyl and A represents -C(C(CH₃)₂)-, and wherein the the phenyl groups may comprise further subsitutents.

A preferred xantphos-type ligand may be a POP-xantphos-type ligand or a xantphos-type ligand according to the below formula (II):

wherein X is C or Si, R1 and R^ are each independently a hydrogen or an alkyl group having 1 to 5 carbons and R3, R4 R5 _ana; R6 _{are eac}h independently an optionally substituted phenyl group, a isopropyl group or a t-butyl group.

A POP-xantphos type ligand is a known ligand and described in R. P. J. Bronger, J. P. Bermon, J. Herwig, P. C. J. Kamer, P. W. N. M. van Leeuwen, Adv. Synth. Catal. 2004, 346, 789 and has a formula (III) as below:

(HI), wherein is hydrogen, methyl and/or a tert.-butyl group and is hydrogen and/or a methyl group.

Examples of suitable xantphos-type ligands according to formula (II) are those wherein X is C, and are hydrogen and R3 R4 5 _anc| R6 _are phenyl groups (further also to as xantphos); X is C, R^ and R^ are hydrogen and R3 R4_ R5 and R6 are o-methoxyphenyl groups (further also to as oMeO-xantphos); X is C, R^ and R2 are t-butyl groups and R3 R4, R5 and R^ are phenyl groups (further also to as tBu-xantphos); or X is Si, R^ and R^ are hydrogen and R3 R4_ R5 _anc| R6 _are phenyl groups (further also to as Si-xantphos).

The xantphos-type ligand is in itself known and may be prepared by well known procedures as for example described in US2004023979, US2004023980, van der Veen, L. A.; Kamer, P. C. J.; van Leeuwen, P.W.N.M. Organometallics 1999, 18, 4765 or van der Veen, L. A.; Kamer, P. C. J.; van Leeuwen, P.W.N.M. Angewandte Chemie-lnternational Edition 1999, 38, 336.

The group 8-10 metal may be for example cobalt, nickel, iridium, rhodium, platinum and palladium. Preferably the Group 8-10 metal is rhodium or palladium and even more preferably the metal is rhodium. Rhodium may be present in or provided to the catalyst system as for example as RhCl3^»3H20, [RhH(CO)(PPh3)3],

Rh(CO)2(acac), [Rh(cod)CI]2, [Rh(cod)2]BF4 and [Rh(cod)2]OTf , wherein acac represents acetylacetonate, cod represents 1 ,5-cyclooctadiene and OTf represents trifluoridomethanesulfonate, rhodium catalyst precursor.

The catalyst system may be prepared in situ in a reaction zone or, alternatively, it can be prepared ex-situ by reacting the rhodium catalyst precursor with the phosphorus ligand. The molar ratio between the phosphorus donor ligand as for example the xantphos-type ligand and rhodium may be between 0.5 and 100 or preferably between 1 and 10 or even more preferably between 2 and 4 mol ligand/ mol rhodium. Subsequently the catalyst system may be introduced into the reaction zone with the solvent and the pentenamide.

The catalyst system may comprise one or more co-catalyst(s). One possibility may be an acidic co-catalyst as for example p-toluenesulfonic acid

(HOTs). It was found that when the process is performed in the absence of HOTs, less polymerisation takes place. Other possible co-catalysts include fluorinated compounds, and more preferably 1 , 1 ,1 ,3,3,3-hexafluoroisopropyl alcohol (HFIPA). Such a co-catalyst may be present in a molar ratio of from 2 to 35 (mol co-catalyst / mol pentenamide) such as between 2 to 35, more preferably from 2 to 15. A co- catalyst may have a selectivity-enhancing effect.

Suitable solvents are organic solvents that are inert or solvents that do not disturb the reaction under the conditions of the reaction. Possible solvents include for example the starting compound and the product of the process and compounds that are related to the product to be formed, such as by-products and particularly condensation products which may form during the reaction. Other suitable solvents include saturated hydrocarbons such as naphthas, kerosine, mineral oil and cyclohexane and aromatics, esters, ethers, ketones and nitriles such as toluene, benzene, xylene, or 2,2,4-trimethyl-1 ,3-pentaandiolmonoisobutyraat, also known as texanol(texanol is a registered trademark of Eastman Chemical Company), diphenyl ether, tetrahydrofuran, cyclohexanone and benzonitrile. Preferred solvent are glyme, diglyme, tetrahydrofuran or toluene, and more preferably the solvent is glyme or diglyme. Some water may additionally be present. The concentration of water is preferably below 15 vol.%. It has been found that in the presence of water aldehydes can form, which in a later stage may be hydrogenated to alcohol. Diglyme may suitably be used as solvent in combination with 1 , 1 , 1 ,3,3,3-hexafluoroisopropyl alcohol (HFIPA) as co-catalyst.

The concentration of rhodium in the process may be between 1 and 100 ppm and more preferably between 1 and 40 ppm as calculated as free metal (mol of metal precursor (based on mononuclear compound) x atomic mass of metal / volume of reaction mixture in ml; assuming the average density of the reaction mixture to be 1 g/ml).

The temperature, i.e. the temperature at which the reaction may

advantageously be performed may be between 50 and 130 °C, preferably between 80 and 130 °C and more preferably between 80 and 1 10 °C. In general the temperature may also be lower or higher, but lower temperatures slow down the reaction, and higher temperatures tend to promote polymerisation.

The molar ratio of hydrogen and carbon monoxide, preferably for the hydroformylation reaction, may be between 4:1 and 1 :1 and preferably between 4: 1 and 2: 1 and more preferably between 3: 1 and 2: 1 . The total pressure may be between 2 and 12 MPa, preferably between 4 and 10 MPa and more preferably between 5 and 7 MPa.

The pentenamide is preferably 4-pentenamide because the selectivity to the saturated and/or unsaturated ε-caprolactam will then be favoured. Mixtures of 2-, 3- and 4-pentenamide may also be used as feed for the present process. Preferably the molar ratio of 4-pentenamide to 3-pentenamide and 2-pentenamide is above 2, preferably above 3 and more preferably above 5.

The concentration of the starting pentenamide may be between 0.2 and 0.5 M. The concentration of pentenamide is herein defined as the total of all

pentenamide isomers. At higher concentration polymerisation may occur and unsaturated nylon polymer may be formed next to unsaturated ε-caprolactam and ε-caprolactam. At lower, more diluted, concentration of pentenamide less

polymerisation is observed.

The reactions that are believed to take place in the process according to the invention are illustrated in Figure 1 . In this Figure it is shown that the linear aldehyde is formed by hydroformylation of 4-pentenamide. The linear aldehyde surprisingly was found to cyclise to form the unsaturated ε-caprolactam.

Some of the formed unsaturated ε-caprolactam may be hydrogenated under the reaction conditions thereby resulting in a mixture of saturated and unsaturated ε-caprolactam. As explained above some polymerisation may occur of the saturated and unsaturated ε-caprolactam. Other side reactions resulting in by-products are not shown in Figure 1 for clarity reasons. The entire process from the pentenamide to saturated ε-caprolactam is referred to as an intramolecular hydroamidomethylation reaction.

Suitably any unsaturated ε-caprolactam is hydrogenated in a separate step to ε-caprolactam in the presence of a hydrogenation catalyst. The hydrogenation catalyst may be a homogeneous hydrogenation catalyst or a heterogeneous hydrogenation catalyst. A suitable heterogeneous catalyst may comprise a Group 8, 9 or 10 metal of the Periodic System (standard form). Preferred hydrogenation catalysts are nickel, cobalt, platinum, copper, rhodium, ruthenium, iridium, gold and palladium comprising catalysts of which rhodium and palladium comprising catalysts are preferred. The hydrogenation may be performed in a separate vessel or reactor than the reactor in which the unsaturated ε-caprolactam is prepared. Such a hydrogenation step may be performed by means of well known processes. It has been found that the catalyst system of the process according to this invention may also be used to catalyse the hydrogenation reaction to ε-caprolactam. In order to perform the hydrogenation reaction hydrogen has to replace the mixture of carbon monoxide and hydrogen, at least in part. Thus in a preferred embodiment the hydrogenation catalyst is the catalyst system comprising of rhodium and a phosphine ligand and preferably the xantphos-type ligand as used to prepare the unsaturated ε- caprolactam. Subsequently the hydrogenation is performed in the presence of hydrogen or a gas mixture comprising hydrogen, preferably at a temperature of between 50 and 100 °C and a pressure of between 2 and 10 MPa, to obtain ε- caprolactam.

The hydrogenation may also preferably be performed in the same reaction environment as the reaction environment in which the unsaturated ε-caprolactam is prepared. Typically the hydrogenation will be performed in the presence of a gas mixture comprising hydrogen. Preferably, the hydrogenation reaction may be performed by removing essentially all carbon monoxide present in the reactor, and by adding a gas comprising hydrogen and essentially no carbon monoxide.

Applicants found that the presence of carbon monoxide reduces the ability of the catalyst system employed in the first reaction phase to effectively hydrogenate. However, upon removal of the gas mxiure present, and replacing it with largely a hydrogen atmosphere, the hydrogenation reaction proceeded swiftly. This permits to operate in a single reactor and with a singe catalyst system, by a simple switch of the gas phase making the reaction a one-pot, two-step process.

The total pressure in the reactor in the second stage may advantageously be between 2 and 12 MPa, preferably between 4 and 10 MPa and more preferably between 5 and 7 MPa.

In the process according to the invention some of the unsaturated ε- caprolactam and saturated ε-caprolactam may polymerise. In order to improve the ε- caprolactam yield it may be preferred to depolymerise any polymerised material to ε- caprolactam. Preferably the polymerised material has been subjected to the above described hydrogenation reaction prior to the depolymerisation step.

Depolymerisation may be performed by contacting the polymerised material with super heated steam as described in for example WO97/20813. The pentenamide is suitably prepared from an alkyl pentenoate or pentenoic acid by amidation. The alkyl group may contain 1 to 6 carbon atoms and is suitably a methyl group. The starting alkyl pentenoate or pentenoic acid is preferably a 4-pentenoate alkyl ester or 4-pentenoic acid. Starting from mixtures comprising a high content of 4-pentenoate alkyl ester or 4-pentenoic acid will yield more of the desired 4-pentenamide. Mixtures comprising of 2-, 3- and 4-pentenoic acids or mixtures comprising of 2-, 3- and 4-pentenoate alkyl esters may also be used as shown in Figure 2 for example a mixture of 4- and 3-pentenoate methyl esters. The amidation reaction may be carried out by contacting the alkyl pentenoate with a source of ammonia at a temperature of between 20 and 100 °C. The source of ammonia may be for example ammonia gas, methanolic ammonia and preferably ammonium hydroxide. The amidation is disclosed in more detail in present examples 2 to 6.

The alkyl pentenoate may be obtained by carbonylation of butadiene as for example described in the afore mentioned EP1251 122. A disadvantage of the butadiene-based processes is the high cost of butadiene. A second disadvantage is the low rate of the methoxycarbonylation of butadiene.

Another process for obtaining the alkyl pentenoate starts from levulinic acid as a renewable source. Levulinic acid may be produced from agricultural cellulosic waste products or cellulosic waste from the paper industry or municipal waste and therefore constitutes a renewable source. The hydrogenation of levulinic acid has been described and produces gamma-valerolactone in high yield as for example described in US2012/0302767. The alkyl pentenoate may subsequently be prepared by reacting the gamma-valerolactone, also referred to as GVL, with a d-C6 alcohol, as described in for example US4740613 or WO2004007421 . Figure 3 illustrates the preparation of a mixture of methyl pentenoates by reacting gamma-valerolactone with methanol.

Preferably the transesterification GVL to the alkyl pentenoate is performed as an acid-catalyzed reactive distillation as for example described in WO2005058793 or in present example 1 . The catalytic distillation is advantageous because it makes use of the large difference in boiling point between GVL and the formed alkyl pentenoates. During the reactive distillation process, the alcohol is continuously feed to the reaction mixture comprising the starting GVL and the acid catalyst. The acid catalyst is preferably para-toluenesulfonic acid (HOTs).

When the alcohol is methanol, the distillate product mixture will comprise methanol, water, methyl 2-pentenoate (2-MP), cis and trans methyl 3-pentenoates (3- MP) and methyl 4-pentenoate (4-MP) as well as trace amounts of GVL, methyl 4- methoxypentanoate and methyl 4-hydroxypentanoate.

The above processes may yield a mixture comprising of 2-, 3- and 4- pentenoates. Preferably the feed comprises substantially more alkyl 4-pentenoates, i.e. alkyl esters of the 4-pentenoic acid, than 2- and 3-pentenoates. In order to increase the content of 4-pentenoate alkyl esters one may subject this mixture to an isomerisation reaction as for example described in for example EP-A-0126349.

Preferably the pentenamide is thus obtained by hydrogenation of levulinic acid to gamma-valerolactone (GVL), transesterfication of gamma-valerolactone (GVL) to alkyl pentenoates and amidation of the alkyl pentenoates to obtain pentenamides.

Preferably, a process is used that effectively converts the GVL into a 4 - pentenamide enriched feed, e.g. by separating 4-alkylpentenoate, preferably 4- methylpentenoate from the mixture of the different isomers, for instance by

azeotropic distillation with water, and by feeding the non-desired pentenoate isomers back into the reactive distillation section, where they at least in part revert to GVL.

The reactive distillation thus preferably is performed under conditions whereby methanol is removed from the methyl pentenoate isomers. These conditions apply typically under transesterification conditions for GVL, as prevailing in the reactive distillation section of methyl pentenoates production, as for instance those disclosed in US4,879,405 or US5, 144,061 .

The preferred formation of the desired pentenoate isomer may further be enhanced by catalytic conversion of GVL into a 4-alkylpentenoate in the presence of a selective basic heterogeneous catalyst, e.g. cesium acetate on Silica, at a temperature in the range of from 300 to 380 °C, preferably from 340 °C to 360 °C for methylpentenoate as starting material for the azeotropic distillation, as disclosed for instance in WO-A-2004/007421 .

The invention is advantageousoly also directed to a process to prepare ε- caprolactam from levulinic acid by (i) hydrogenation of levulinic acid to gamma- valerolactone (GVL), (ii) transesterification of gamma-valerolactone (GVL) to alkyl 4- pentenoate, (iii) amidation of the alkyl pentenoate to obtain 4-pentenamide and (iv) intramolecular hydroamidomethylation of 4-pentenamide to ε-caprolactam and/or unsaturated ε-caprolactam, followed by an optional hydrogenation of any unsaturated ε-caprolactam as may be obtained.

The present invention advatageously further relates to a prefeabrly integrated process to prepare ε-caprolactam and/or unsaturated ε-caprolactam, comprising (a) amidation of an alkyl pentenoate to obtain a pentenamide; and (b) intramolecular hydroamidomethylation of the pentenamide to ε-caprolactam and/or unsaturated ε-caprolactam. Step (b) preferably is performed according as described herein above. The alkyl pentenoate used in the process is preferably formed by (i) hydrogenation of levulinic acid to gamma-valerolactone (GVL), and (ii)

transesterfication of gamma-valerolactone (GVL) to alkyl pentenoate. Preferably, in (ii), the GVL is converted into a 4 -pentenamide enriched feed, by (a) separating 4- alkylpentenaote from a mixture of the different isomers, preferably by azeotropic distillation with water, and (b) reverting the non-desired pentenoate isomers to GVL under dehydrating conditions, "dehydrating" herein revers to the removal of the alcohol, e.g. methanol, which may occur under the conditiosn of the reactive transesterification. Step (ii) is advantageously performed in the presence of a selective basic heterogeneous calatyst, preferably comrpising cesium acetate on Silica, at a temperature in the range of from 300 to 380°C, as set out herein above.

Preferably, the process further comprises a step (iia) comprising recycling of 2- and 3-pentenoates to the reactive transesterification of GVL. This was found to increase the selectivity for the desired products, since the 2-, 3-, and 4-pentenoate isomers likely produce the same pentenamide (PA) isomeric mixture. The term "unsaturated ε-caprolactam" herein relates to product or products obtained in the intramolecular cyclisation and dehydration of the hydroformylation products formed initially. The intramolecular hydroamidomethylation of 4-pentenamide to ε- caprolactam is preferably performed by the process according to this invention and its preferred embodiments as described, thus including the above referred to depolymerisation of any polymerised by-products. The invention shall be illustrated by the following, non-limiting examples.

Instruments: The stainless steel autoclave reactors (100 ml) were of HEL Limited, UK, equipped with magnetic stirrer, pressure transducer and temperature controlling thermocouple. A Hewlett Packard HP6890 Series auto-sampler GC system was used for regular GC analysis. GC-MS analysis were carried out on an Agilent technologies 7820A GC system series coupled with an Agilent technologies 5975 series GC-MSD system. Nuclear magnetic resonance spectra were recorded on a Bruker DPX300 (300 MHz) or a Bruker DMX400 (400 MHz) spectrometer.

Example 1 : Catalytic Reactive Distillation of methyl pentenoates

The reaction was performed in a 100 mL two-necked round bottom flask loaded with GVL (9.5 mL, 100 mmol) and acid catalyst (1 - 10 mmol) were dissolved in 10 mL of MeOH. The flask was connected to a micro distillation device which was connected to a 100 mL round bottom flask used as a receiver. The receiver flask was cooled down with liquid N2. The solution was heated to a set temperature, 150 °C-

200 °C for 4-12 h. During this time MeOH was added to the bottom of the reactor flask at a rate of 10 mL/h. After specified time, the contents of both the reactor flask and the receiver were analyzed by GC. The reactor flask generally yielded a yellow- brown clear solution that contained a mixture of unreacted GVL, 3-MP, 4-MP, intermediates (methyl 4-hydroxypentanoate, methyl 4-hydroxypentanoate) and methyl para-toluenesulfonate. The receiver flask contained a clear colorless solution that was found to be a mixture of MeOH, water, 4-MP, 3-MP with traces of 2-MP and GVL. In a typical experiment (starting from 100 mmol GVL, 10 mmol para- toluenesulfonate, and a methanol feed rate of 10 mL/h) after a reaction time of 12 h at 190 °C 97% conversion of GVL was reached. The receiver flask contained 2.5 mmol of GVL, 67.4 mmol of 3-MP, 21 .7 mmol of 4-MP, 0.1 mmol of 2-MP and 0.7 mmol of methyl 4-methoxypentanoate. The reactor flask contained 0.6 mmol GVL, 3.3 mmol of 3-MP, 1 .1 mmol of 4-MP, 0.1 mmol of methyl 4-hydroxypentanoate and 0.8 mmol of methyl 4-methoxypentanoate.

Examples 2-4: Amidation of methyl pentenoates to pentenamides (PA) General Procedure: After each amidation experiment in examples 2-4, the reaction mixture was taken and at once analyzed by gas chromatography. Calibration lines for each analyte were used in determining the yields of the various products. The assignments of the products were confirmed with GC-MS and comparison with authentic and pure commercial samples.

GC Method: 1 μί Crude reaction mixture containing internal standard was injected into a Hewlett Packard HP6890 Series auto-sampler GC system with column HP-1 MS Ul (30m^*0.250mm^*1 .ΟΟμητι). All the solvents have been assigned by comparing to their standard GC spectra. All the retention values of substrate and product to undecane have been determined using commercially available or isolated standard chemicals. Analysis conditions: 130 °C (5 min), ramp 50°C/min to 300 °C, 300 °C (3.6 min) (12 min in total).

List of retention times for the different products: 3.1 1 min (MeOH), 5.01 min (4-MP), 5.27 min (trans-3-MP), 5.36 min (cis-3-MP), 6.34 min (GVL), 6.45 min (diglyme), 6.51 min (undecane), 7.04 min (4-PA), 7.32 min (trans-3-PA), 7.38 min (cis-3-PA).

Example 2: Amidation of methyl pentenoates to pentenamides (PA)

The reaction was carried out in a 50 mL round bottom flask loaded with 5 ml_ of a methyl pentenoate solution in MeOH (0.9 M, the contents of the receiver flask from the reactive distillation experiment in example 1 ), concentration

determined through GC calibration lines, 4.5 mmol total MP, (in approximate 3: 1 ratio of 3-MP:4-MP, with traces of GVL; thus containing -3.4 mmol 3-MP and -1 .1 mmol 4-MP), NH₃ (7 N) in MeOH and (0.254 ml) undecane as an internal standard were mixed and stirred for different times (see Table 1 ) at various temperatures between room temperature (rt) to 100 °C. After the experiment, the reaction mixture was taken and at once analyzed by gas chromatography. Calibration lines for each analyte were used in determining the yields of the various products. The assignments of the products were confirmed with GC-MS and comparison with authentic and pure commercial samples.

Table 1

Ex. 7N NH₃ in T t 3-PA 4-PA yield

MeOH

mmol of NH₃ °C h mmol mmol %

2.1 50 rt 5 0.1 0.0 2

2.2 50 rt 24 0.2 0.0 4

2.3 50 50 5 0.4 0.1 1 1

2.4 50 80 5 0.5 0.1 13

2.5 50 100 5 0.5 0.1 13 Example 3: Amidation of methyl pentenoates to pentenamides (PA)

The reaction was carried out in a 300 ml_ autoclave reactor loaded with MP (10 mmol (3-MP/4-MP~3: 1 , as in Example 1 ), 1 .14 g, after evaporation of MeOH) and (0.254 ml) undecane as an internal standard and in some cases a solvent (diglyme) was added (experiment 3.4). The autoclave was then tightly closed and subsequently filled with 0.6 MPa of NH₃ (g) (~75 mmol) and stirred for different reaction times kept at various temperatures between rt-100 °C (see Table 2). After the experiment, 5 ml of dried and degassed methanol was added to the reaction mixture (experiments 3.1 - 3.3) and this was then analyzed by gas chromatography. Calibration lines for each analyte were used in determining the yields of the various products. The assignments of the products were confirmed with GC-MS and comparison with authentic and pure commercial samples.

Table 2

(a) in 5 ml_ diglyme.

Example 4: Amidation of methyl pentenoates to pentenamides (PA) The reaction was carried out in a 50 mL round bottom flask loaded with MP (10 mmol (3-MP/4-MP-3), 1 .14 g, after evaporation of MeOH from a distillate as obtained in Example 1 ), ammonium hydroxide 35% (50 mmol, 2.42 mL) and (0.254 ml) undecane as an internal standard were mixed and stirred for 5-6 hours (see Table 3) at various temperature between room temperature to 100 °C.

Table 3 Ex. NH₄OH (35%) T t 3-PA 4-PA yield

mmol of NH₃ °c h mmol mmol %

4.1 50 rt 5 2.1 0.2 23

4.2 50 50 5 4.8 0.8 56

4.3 50 80 5 7.2 2.0 92

4.4 50 100 5 7.3 2.1 94

4.5 50(a) 80 5 2.4 0.7 69

4.6 25 80 5 4.1 0.3 44

4.7 100 80 5 7.3 2.0 93

4.8 50 80 6 7.4 2.4 98

(a) no evaporation of MeOH (5 mL of a methyl pentenoates solution in MeOH, 0.9 M, a distillate from a reactive distillation experiment, concentration determined through GC calibration lines).

Example 5: Synthesis of 3-pentenamide from 3-pentenoic acid

Synthesis of 3-pentenamide from 3-pentenoic acid according to the procedure as described in K. von Auwers, Justus Liebigs Annalen der Chemie 1923, 432, 65. Bertrand, M. B.; Wolfe, J. P. Tetrahedron 2005, 61 , 6447. Nicolai, S.; Waser, J. Org. Lett., 2011 , 13, 6324.

Following the reported procedure, thionyl chloride (8.7 ml, 120 mmol) was added dropwise to frans-3-pentenoic acid (10 ml, 100 mmol) at 0 °C and the mixture was stirred at RT for 10 min and at 60 °C for 30 min. The excess thionyl chloride was evaporated and the oil was dissolved in 20 ml CH2CI2. This solution was added drop wise to a solution of 7 N NH₃ in MeOH (150 ml, 1 .0 mol) at 0 °C and stirred for 10 minutes at room temperature. The solvents were evaporated. Water (50 ml) was added and was extracted 2 times with 50 ml CH2CI2. The combined organic layers were washed with 50 ml brine, dried over MgSO₄ and the solvents were removed in vacuo to give a white powder. Yield 7.93 g, 80%. ¹H-NMR (CDCI₃): δ = 6.65 and 5.99 (br s, 2 x 1 H, NH₂), 5.70-5.49 (m, 2H, 2 x CH), 2.96 (d, 2H, CH₂), 1 .70 (m, 3H, CH₃). ¹³C-NMR (CDCI3): δ = 175.2 (CONH₂), 130.8 and 123.5 (2 x CH), 39.8 (CH₂), 17.9 (CH₃).

Example 6: Synthesis of 4-pentenamide from 4-pentenoic acid The synthesis of 4-pentenamide was performed in a similar fashion as in Example 5 starting from 4-pentenoic acid (15 ml, 150 mmol), thionyl chloride (13 ml, 180 mmol) and 200 ml 7 N NH₃ solution in MeOH. The yield was 13.6 g of a white powder (92%). ¹H-NMR (CDCI3): δ = 5.91 -5.78 (m, 1 H, CH), 6.0 and 5.7 (br s, 2 x 1 H, NH₂), 5.13-5.02 (m, 2H, CH₂=CH), 2.44-2.30 (m, 4H, 2 x CH₂). ¹³C-NMR (CDCI3): δ = 175.6 (CONH₂), 136.9 (CH), 1 15.7 (CH₂=CH), 35.1 and 29.4 (2 x CH₂).

Examples 7-1 1 : Catalytic high pressure intramolecular hydroamido- methylation reactions of pentenamide

All preparations and manipulations were performed using standard Schlenk techniques under an argon atmosphere. The solvent bis(2-methoxyethyl)ether (diglyme) was distilled from CaH₂, deoxygenated and used immediately after the purification process. The catalytic reactions were carried out under varying syngas pressures and reaction temperatures. For all the catalytic experiments the active catalyst precursor was formed by in-situ in the autoclave by transferring the metal precursor and the selected phosphane ligands.

The product samples in the Examples were analysed by GC. The GC Method: 1 μΙ_ Crude reaction mixture containing internal standard was injected into a Hewlett Packard HP6890 Series auto-sampler GC system with coloum HP-1 MS Ul (30m^*0.250mm^*1 .00pm). All the solvents have been ignored by comparing to their standard GC spectra. All the retention values of substrate and product to undecane have been determined using commercially available or isolated standard chemicals. Analysis conditions: 160 °C (3.3 min), ramp 30°C/min to 300 °C, 300 °C (4 min) (12 min in total).

List of retention times for the different products: 4.47 min (diglyme), 4.98 min (4-PA), 5.79 min (undecane), 6.31 min (unsaturated branched), 6.44 min

(unsaturated caprolactam), 6.81 (caprolactam)

GC-MS Method: 1 μΙ_ Crude reaction mixture containing internal standard was injected into a GC HP7820 Series auto-sampler GC system with column DB- 5MS Ul (30m^*0.250mm^*1 .00Mm) equipped with MSD 5975 Agilent series. All the solvents have been ignored by comparing to their standard GC spectra. All the retention values of substrate and product to undecane have been determined using commercially available or isolated standard chemicals. Analysis conditions: 100 °C (2.5 min), 20°C/min to 250 °C, 250 °C (5 min)(15 min in total). Example 7: intramolecular hvdroamidomethylation of 4-PA

In the preparation of the catalytic reaction mixture a rhodium precursors [Rh(cod)CI]₂ (0.0025 mmol, 1.24 mg), xantphos ligand (0.01 mmol, 5.79 mg) and HOTs (0.025 mmol, 4.78 mg) followed by 2 mmol of 4-PA as prepared in Example 6 were weighed and transferred into an autoclave. The autoclave was tightly closed and subsequently filled with argon with use of a Schlenk line that was connected to one of the valves of the autoclave. Through another valve under a continuous flow of argon subsequently was added 10 ml of dried and degassed solvent diglyme and (0.254 ml) undecane as an internal standard. Then the reactor was inserted into the heating block and pressurized with 5 MPa (CO/H₂ molar ratio of 1/2 mol/mol) syngas. This reaction mixture was stirred at 500 rpm for 30 min to ensure that complex formation was complete. The reaction mixture was heated up to 100 °C (within 30 min) under stirring at 500 rpm. All reaction conditions of the catalytic process were controlled by computerized software panels. After standing for eight hours at this temperature, the autoclave was cooled down to room temperature over about one hour. The autoclave was then slowly vented to atmospheric pressure. After each catalytic run the reaction mixture was taken from the reactor and at once analyzed by gas chromatography. Calibration lines for each analyte were used in determining the conversion of the substrates and yields of the various products. The assignments of the products were confirmed with GC-MS and comparison with authentic and pure commercial samples. The results are listed in Table 4.

Example 8: intramolecular hvdroamidomethylation of 4-PA

In the preparation of the catalytic reaction mixture a rhodium precursors [Rh(cod)CI]₂ (0.0025 mmol, 1.24 mg) and xantphos ligand (0.01 mmol, 5.79 mg) followed by 2 mmol of 4-PA as prepared in Example 6 were weighed and transferred into an autoclave. The autoclave was tightly closed and subsequently filled with argon with use of a Schlenk line that was connected to one of the valves of the autoclave. Through another valve under a continuous flow of argon subsequently was added 10 ml of dried and degassed solvent diglyme and (0.254 ml) undecane as an internal standard. Then the reactor was inserted into the heating block and pressurized with 5 MPa (CO/H₂ molar ratio of 1/2 mol/mol) syngas. This reaction mixture was stirred at 500 rpm for 30 min to ensure that complex formation was complete. The reaction mixture was heated up to 100 °C (within 30 min) under stirring at 500 rpm. All reaction conditions of the catalytic process were controlled by computerized software panels. After standing for eight hours at this temperature, the autoclave was cooled down to room temperature over about one hour. The autoclave was then slowly vented to atmospheric pressure. After each catalytic run the reaction mixture was taken from the reactor and at once analyzed by gas chromatography. Calibration lines for each analyte were used in determining the conversion of the substrates and yields of the various products. The assignments of the products were confirmed with GC-MS and comparison with authentic and pure commercial samples. The results are listed in Table 4.

Example 9: intramolecular hydroamidomethylation of 4-PA

In the preparation of the catalytic semi-one pot reaction mixture a rhodium precursors [Rh(cod)CI]2 (0.0025 mmol, 1 .24 mg) and xantphos ligand (0.01 mmol, 5.79 mg) followed by 2 mmol of 4-PA as prepared in Example 6 were weighed and transferred into an autoclave. The autoclave was tightly closed and subsequently filled with argon with use of a Schlenk line that was connected to one of the valves of the autoclave. Through another valve under a continuous flow of argon subsequently was added 10 ml of dried and degassed solvent diglyme and (0.254 ml) undecane as an internal standard. Then the reactor was inserted into the heating block and pressurized with 5 MPa (CO/H₂ molar ratio of 1/2 mol/mol) syngas (=P(CO/H₂)=5(1/2) MPa). This reaction mixture was stirred at 500 rpm for 30 min to ensure that complex formation was complete. The reaction mixture was heated up to 100 °C (within 30 min) under stirring at 500 rpm. All reaction conditions of the catalytic process were controlled by computerized software panels. After standing for eight hours at this temperature, the autoclave was cooled down to room temperature over about one hour. The autoclave was then slowly vented to atmospheric pressure.

In a semi-one-pot reaction after depressurizing syngas and flushing with di- hydrogen gas, the reactor was pressurized with 8 MPa dihydrogen gas and then the reaction mixture heated up to 80 °C under stirring at 500 rpm for hydrogenation step. After standing for four hours at this temperature, the autoclave was cooled down to room temperature and then slowly vented to atmospheric pressure. After each catalytic run the reaction mixture was taken from the reactor and at once analyzed by gas chromatography. Calibration lines for each analyte were used in determining the conversion of the substrates and yields of the various products. The assignments of the products were confirmed with GC-MS and comparison with authentic and pure commercial samples. The results are listed in Table 4.

Table 4

(a) hydroformylation step; (b) hydrogenation step after venting CO.

Example 10: intramolecular hydroamidomethylation of 4-PA

Example 7 was repeated using 2 mmol (198 mg) of 4-PA; 0.0025 mmol (1 .24 mg) [Rh(cod)(CI)]₂ precursor, 0.01 mmol ligand, P(CO/H₂)=5(1/2) MPa; T=100 °C; f=8-12h; Solvent: 10 ml_ diglyme.

Examples 10.1 and 10.2 are comparative examples that were performed without ligand; in 10.1 only the Rhodium catalyst precursor was used, in 10.2 a 1 : 1 mixture of Rh and Co precursor was used.

Examples 10.3 and 10.4 were performed using a monodentate phosphorus ligand, wherein PPh₃ represents triphenyl phosphine and P(0-di-tBuPh)₃ represents tris(2,4-di-t-butylphenyl)phosphite.

Examples 10.5-10.13 were performed using different xantphos-type ligands. Examples 10.1 1 -10.13 were performed wherein some acidic co-catalyst was added (HOTs and HFIPA=1 , 1 , 1 ,3,3,3-hexafluoroisopropyl alcohol). Examples 10.14-10.16 were performed wherein some water was added.

Example 10.17 was performed using a 3PA-4PA (3:1 ) feed produced from

GVL from example 4.8.

The amount of products was determined by GC analysis using undecane as an internal standard. The results are listed in Table 5.

Example 1 1 : intramolecular hydroamidomethylation of 4-PA

Example 9 was repeated using 2 mmol (198 mg) of 4-PA; 0.0025 mmol

(1 .24 mg) [Rh(cod)(CI)]₂ precursor, 0.01 mmol xantphos-type ligand, P(CO/H₂)=5(1/2 MPa/MPa) MPa; T=100 °C; f=8-12h; Solvent: 10 ml_ diglyme. In a semi-one-pot reaction condition: 8h at 100 °C hydroformylation- depressurizing syngas- flushing with H₂- pressurizing with H₂-4h at 80 °C hydrogenation. The results are listed in Table 5.

Table 5

Table 5 continued

In Table 5, the following references were used: (a) L = percentage of 7-membered lactam ring, corresponding with the linearity of the intermediate aldehyde; (b) In parentheses the amount of pentanamide; (c) 0.00125 mmol (0.62 mg) [Rh(cod)(CI)]₂ precursor and 0.00125 mmol (0.43 mg) Co₂(CO)₈; (d) In parentheses the amount of 6-oxohexanamide; (e) 0.1 ml water per 10 ml diglyme, (f) 0.5 ml water per 10 ml diglyme, (g) 1 ml water per 10 ml diglyme, (h) A mixture of 3-PA (1.5 mmol) and 4-PA (0.5 mmol) produced from GVL was used (experiment 4.8); the amounts of pentenamides was determined by injecting the mixture into GC before starting the reaction, (j) hydroformylation step; (k) hydrogenation step after venting CO.

The above experiments show that the present process permits to obtain unsaturated, but in partiuclar also saturated ε-caprolactam from penteneamides in unprecedented yields and with very high selectivity. The process furthermore is highly flexible., and allows to be operated as a one-pot process, or as a two-step process, allowing for an industrial scale implementation. The process furthermore permits to obtain ε- caprolactam from sustainable and renewable resources, and using a catalytic process rather than the presently employed processes, using readily obtainable resources such as carbon monoxide and hydrogen.

Claims

Process to prepare ε-caprolactam and/or unsaturated ε-caprolactam from a pentenamide by contacting the pentenamide with a mixture of hydrogen and carbon monoxide in the presence of a solvent and a catalyst system comprising of a Group 8-10 metal and a phosphorus- donor ligand.

Process according to claim 1 , wherein the metal is rhodium or palladium.

Process according to any one of claims 1 -2, wherein the phosphorus- donor ligand is a monodentate phosphine ligand, a monodentate diphosphite ligand, a bidentate diphosphine or a bidentate diphosphite ligand.

4. Process according to claim 3, wherein the ligand is a xantphos-type

ligand.

5. Process according to claim 4, wherein the ligand is a POP-xantphos-type ligand or a xantphos-type ligand defined according to formula (II):

wherein X is C or Si, R1 and are each independently a hydrogen or an alkyl group having 1 to 5 carbons and R3 R4 5 _ANA; R6 _{are eac}h independently an optionally substituted phenyl group, an isopropyl group or a f-butyl group.

6. Process according to claim 5, wherein X is C, and are hydrogen and R3 R4 R5 _ANO; R6 _are phenyl groups; or

X is C, R1 and R^ are hydrogen and R3 R4_ R5 _ANC| R6 _are p-methoxy phenyl groups; or

X is C, R1 and R^ are t-butyl groups and R3 R4_ R5 _ANC| R6 _are phenyl groups; or

X is Si, R1 and R^ are hydrogen and R3 R4_ R5 _ANC| R6 _are phenyl groups.

7. Process according to any one of claims 1 -6, wherein the temperature is between 50 and 130 °C.

8. Process according to any one of claims 1 -7, wherein the molar ratio of hydrogen and carbon monoxide is between 4: 1 and 1 : 1 .

9. Process according to any one of claims 1 -8, wherein a co-catalyst is present in a molar ratio between 2-35 mol additive/mol pentenamide. 10. Process according to claim 9, wherein the co-catalyst is 1 , 1 , 1 ,3,3,3- hexafluoroisopropyl alcohol and/or p-toluenesulfonic acid.

1 1 . Process according to any one of claims 2-10, wherein the metal is

rhodium, and the molar ratio between the phosphorus-donor ligand and rhodium is between 0.5 and 100.

12. Process according to any one of claims 1 -1 1 , comprising subsequent hydroformylation and hydrogenation steps, wherein the hydrogenation step is performed essentially in absence of carbon monoxide

13. Process according to claim 1 1 , wherein the gas mixture comprising carbon monoxide is removed when the hydroformylation reaction is essentially completed, and a gas atmosphere comprising hydrogen is added.

14. Process according to any one of claims 1 -13, wherein any unsaturated ε-caprolactam as obtained in the process is hydrogenated in a separate step to ε-caprolactam in the presence of a hydrogenation catalyst.

15. Process according to claim 14, wherein the hydrogenation catalyst is the catalyst system as defined in any one of claims 1 to 1 1 .

16. Process according to any one of claims 1 -15, wherein the pentenamide comprises 4-pentenamide.

17. Process to prepare ε-caprolactam and/or unsaturated ε-caprolactam, comprising

(a) amidation of an alkyl pentenoate to obtain a pentenamide; and

(b) intramolecular hydroamidomethylation of the pentenamide to ε- caprolactam and/or unsaturated ε-caprolactam. 18. Process according to claim 17, wherein (b) is performed according to any one of claims 1 to 16.

19. Process according to claim 17 or 18, wherein alkyl pentenoate used in the process is formed by

(i) hydrogenation of levulinic acid to gamma-valerolactone (GVL), and

(ii) transesterfication of gamma-valerolactone (GVL) to alkyl pentenoate.

20. Process according to claim 19, wherein in (ii), the GVL is converted into a

4 -pentenamide enriched feed, comprising

(a) separating 4-alkylpentenaote from a mixture of the different isomers, preferably by azeotropic distillation with water, and

(b) reverting the non-desired pentenoate isomers to GVL under dehydrating conditions. Process according to claim 19 or 20, wherein (ii) is performed in the presence of a selective basic heterogeneous calatyst, preferably comrpising cesium acetate on Silica, at a temperature in the range of from 300 to 380°C.