The present invention relates to a process for treating a supported metal containing catalyst, to a catalyst obtainable by such process and to a process for hydrogenation of unsaturated hydrocarbons wherein such catalyst is used.

In refineries and petrochemical facilities large amounts of hydrocarbons are produced and stored which comprise significant amounts of unsaturated hydrocarbons causing problems during the further processing steps and its storage. Such unsaturated compounds are for instance acetylene, propyne, propadiene, butadienes,

vinylacetylene, butynes, phenylacetylene and styrene.

For example, acetylene is known to reduce the

catalyst activity in polymerisation processes and the quality of the polymers is deteriorated. Thus, in the synthesis of polyethylene from ethylene the concentration of acetylene should be minimized.

These undesired unsaturated compounds are removed mainly by selective hydrogenation wherein these compounds are hydrogenated, preferably to a content of less than a few parts per million (ppm) . It is important for the efficiency of the selective acetylene hydrogenation in ethylene feeds that the selective hydrogenation of ethylene to ethane and the oligomerization to higher hydrocarbons and the production of coke are avoided.

In the art, nickel sulfide, tungsten/nickel sulfide or copper containing catalysts were initially used for selective hydrogenation of such undesired unsaturated compounds. Due to their low activity at high temperatures the formation of polymers was increased. It is also known to use supported palladium (Pd) containing catalysts based on an aluminium oxide (alumina) or silicium oxide (silica) for such selective hydrogenation processes.

Further, supported catalysts based on an alumina, containing both Pd and silver (Ag) , are known for their use in such selective hydrogenation processes. Such Pd-

Ag-Al ₂ C>3 catalysts and their use are for example

described in US2802889, US3243387, US4484015, EP0722776 and US20040248732.

According to the state of the art catalysts exhibit an unsatisfactory selectivity, in particular when

employed in a hydrogenation process, in particular in selective hydrogenation processes for hydrogenating acetylene, propyne, propadiene, butadienes,

vinylacetylene, butynes, phenylacetylene and styrene. For example, in the case of hydrogenation of acetylene from a hydrocarbon feed comprising ethylene, it is important that acetylene is selectively hydrogenated meaning that acetylene is hydrogenated to ethylene, and not further to ethane, and that hydrogenation of ethylene from the hydrocarbon feed is avoided as much as possible.

Therefore, the technical problem underlying the present invention is to overcome the above-identified

disadvantage, in particular to provide a catalyst for the hydrogenation of a hydrocarbon feed that has such higher selectivity.

Surprisingly it was found that such selectivity is increased by first treating the catalyst with an ionic liquid .

Accordingly, the present invention relates to a process for treating a supported metal containing

catalyst, comprising contacting the catalyst with a solution comprising a solvent and an ionic liquid and removing the solvent, wherein the catalyst contains one or more metals selected from the group consisting of nickel, copper, gold, platinum, palladium and silver. Further, the present invention relates to a catalyst obtainable by the above-mentioned process of the present invention.

Further, the invention relates to a supported metal containing catalyst, which contains one or more metals selected from the group consisting of nickel, copper, gold, platinum, palladium and silver and which further contains an ionic liquid.

Further, the invention relates to a process for the hydrogenation, preferably for the selective

hydrogenation, of a hydrocarbon feed, preferably

comprising a first and a second group of unsaturated hydrocarbons, wherein the hydrocarbon feed is contacted under suitable hydrogenating conditions with the catalyst obtained by the above-mentioned process of the present invention, or with the above-mentioned catalyst

obtainable by the above-mentioned process of the present invention or with the above-mentioned supported metal containing catalyst, which contains one or more metals selected from the group consisting of nickel, copper, gold, platinum, palladium and silver and which further contains an ionic liquid, and the unsaturated

hydrocarbons in the hydrocarbon feed, preferably in the first group, are hydrogenated .

As defined by Wasserscheid and Keim in "Angewandte Chemie" 2000, 112, pages 3926-3945, ionic liquids are salts which melt at a relatively low temperature. Ionic liquids are therefore already liquid at relatively low temperatures. In addition, they are in general not combustible and have no measurable vapour pressure. Within the present specification, "ionic liquid" means a salt which has a melting point or melting range which is below 200 °C, preferably below 150 °C and particularly preferably below 100 °C.

Ionic liquids are formed from positive ions and negative ions (cations and anions, respectively) , but are overall neutral in charge. The positive and also the negative ions are predominantly monovalent, but

multivalent anions and/or cations which have up to five, preferably up to four, particularly preferably up to three and particularly preferably up to two electric charges are also possible. The charges within the

respective ions are either localized or delocalized.

It is known to treat a supported metal containing catalyst with an ionic liquid.

For example, in US20090264691 it is described that it was found that by coating with an ionic liquid the activity of the catalyst can be reduced so markedly that even shaped bodies with a diameter of up to 2 cm can be used without significant losses in respect of product selectivity having to be accepted. In the Examples of said US20090264691, a supported nickel catalyst was coated with l-butyl-3-methylimidazolium octyl sulfate (BMIM octyl sulfate) as an ionic liquid. The coated catalyst was used in the hydrogenation of cyclooctadiene .

Further, Kernchen et al . in Chem. Eng. Technol. 2007, 30, No. 8, 985-994 describe the use of a commercial nickel catalyst coated with the ionic liquid [BMIM] [n- C ₈ Hi70S0 ₃ ] in the sequential hydrogenation of

cyclooctadiene to cyclooctene (COE) and cyclooctane. It is said that compared to the uncoated catalyst, the coating with the ionic liquid enhanced the maximum intrinsic COE yield from 40 to 70%. Further, Ruta et al . in J. Phys . Chem. C 2008, 112, 17814-17819 describe that palladium nanoparticles were obtained via reduction of Pd(acac)2 dissolved in an ionic liquid supported on carbon nanofibers anchored to

sintered metal fibers. The ionic liquid was either hydroxyl-functionalized l-butyl-3-methylimidazolium N- bis (trifluoromethanesulfonyl ) imidate [bmimOH] [TF ₂ N] or 1- butyl-3-methylimidazolium hexafluorophosphate

[bmim] [PFe] . The sintered metal fibers comprised nickel, chromium and aluminum. The palladium nanoparticles were tested for the selective hydrogenation of acetylene to ethylene .

Within the present specification, a "supported metal containing catalyst" means a catalyst comprising a support and containing one or more catalytically active metals .

In the present invention, the catalyst contains one or more, preferably two, metals selected from the group consisting of nickel, copper, gold, platinum, palladium and silver. Preferably, said one or more metals is or are selected from the group consisting of copper, gold, platinum, palladium and silver. More preferably, said one or more metals is or are selected from the group

consisting of gold, platinum, palladium and silver.

In case, in the present invention, the catalyst contains only one metal selected from the group

consisting of nickel, copper, gold, platinum, palladium and silver, the catalyst may contain nickel only, copper only, gold only, platinum only, palladium only or silver only.

In a preferred embodiment of the present invention, the catalyst contains two or more metals wherein one of the metals is palladium and the at least one other metal is selected from the group consisting of nickel, copper, gold, platinum and silver. More preferably, the catalyst contains palladium and/or silver. Even more preferably, the catalyst contains palladium and silver. Most

preferably, the catalyst solely contains palladium and silver as the catalytically active metals.

In a preferred embodiment of the present invention, the catalyst contains palladium in a concentration of from 0.01 to 2.50 wt.%, preferably 0.1 to 2.0 wt.%, more preferably 0.5 to 1.5 wt.% and in particular 0.8 to 1.2 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains palladium in a concentration of from 0.02 to 0.05 wt.%, preferably 0.03 to 0.04 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains platinum in a concentration of from 0.01 to 2.50 wt.%, preferably 0.1 to 2.0 wt.%, more preferably 0.5 to 1.5 wt.% and in particular 0.8 to

1.2 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains gold in a concentration of from 0.01 to 2.50 wt.%, preferably 0.1 to 2.0 wt.%, more preferably 0.5 to 1.5 wt.% and in particular 0.8 to 1.2 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains silver in a concentration of from 0.01 to 2.50 wt.%, preferably 0.1 to 2.0 wt.%, more preferably 0.5 to 1.5 wt.% and in particular 0.8 to 1.2 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains silver in a concentration of from 0.0068 to 0.03 wt.%, preferably 0.01 to 0.03 wt.% and in particular 0.01 to 0.025 wt . % (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains copper in a concentration of from 0.01 to 5.00 wt.%, preferably 0.1 to 4.0 wt.%, more preferably 0.5 to 3.0 wt.% and in particular 1.0 to

2.0 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains nickel in a concentration of from 0.01 to 5.00 wt.%, preferably 0.1 to 4.0 wt.%, more preferably 0.5 to 3.0 wt.% and in particular 1.0 to 2.0 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains palladium in a concentration of from 0.02 to 0.05 wt.%, preferably 0.03 to 0.04 wt.%

(based on the total weight of the catalyst) and silver in a concentration of from 0.0068 to 0.03 wt.%, preferably 0.01 to 0.03 wt.% and in particular 0.01 to 0.025 wt.% (based on the total weight of the catalyst) .

In a preferred embodiment of the present invention, the catalyst contains palladium and silver and the weight ratio of the palladium to the silver is of from 1.5 to 3.0, preferably 2.0 to 3.0.

In the present invention, the catalyst further comprises a support. In a preferred embodiment of the present invention, the support is selected from the group consisting of C (carbon) , T1O ₂ (titania) , A1 ₂ 0 ₃ (alumina) , ZrC>2 (zirconia) and S1O2 (silica) . As catalyst support, also modifications of C, T1O2, AI2O3, Zr02 and S1O2 can be used. Preferably, combinations of the catalyst supports selected from the group consisting of C, T1O ₂ , A1 ₂ 0 ₃ , ZrC> ₂ and S1O ₂ can be used. In a preferred embodiment of the present invention, the catalyst support is AI ₂ O ₃ or a modification thereof. More preferably, the catalyst comprises alumina as the support. Most preferably, the catalyst solely comprises alumina as the support.

In a preferred embodiment of the present invention, the catalyst may be in the form of hollow cylinders, tablets, spheres or extrudates.

Preferably, in the present invention, the ionic liquid comprises (i) a cation which is an Ν,Ν'- dialkylimidazolium ion or an N-alkylpyridinium ion and (ii) an anion selected from the group consisting of tetrafluoroborate ion, alkoxyphosphonate ions,

alkylsulfonate ions, hexafluorophosphate ion and amide ions. More preferably, said anion is selected from the group consisting of alkoxyphosphonate ions and amide ions. Most preferably, said anion is an amide ion.

The alkyl groups in the N, N ' -dialkylimidazolium ion and N-alkylpyridinium ion for the ionic liquid may be Ci- Cio alkyl groups, preferably C1-C alkyl groups. Examples of suitable C1- C10 alkyl groups are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl , 2 , 4 , 4-trimethylpentyl and decyl . Preferably, said cation for the ionic liquid is an N, N ' -dialkylimidazolium ion, preferably an Ν,Ν'- dialkylimidazolium ion wherein the alkyl groups are C1- C10 alkyl groups as described hereinabove, preferably C1-C4 alkyl groups as described hereinabove.

A particularly preferred N, N ' -dialkylimidazolium ion is l-butyl-3-methylimidazolium ion (BMIM ion) .

Further, a particularly preferred Ν,Ν'- dialkylimidazolium ion is 1 , 3-dimethylimidazolium ion

(DMIM ion) . In the present invention, the anion from the ionic liquid may be tetrafluoroborate ion which is of the formula BF ^~ .

In the present invention, the anion from the ionic liquid may be an alkoxyphosphonate ion. The

alkoxyphosphonate ion is of the formula RO- PH(=0)0 ^~ wherein R is an alkyl group, preferably a Ci- Cio alkyl group, more preferably a C1-C alkyl group. Examples of suitable C1- C10 alkyl groups are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl , 2 , 4 , 4-trimethylpentyl and decyl . A particularly preferred alkoxyphosphonate ion is methoxyphosphonate ion.

In the present invention, the anion from the ionic liquid may be an alkylsulfonate ion. The alkylsulfonate ion is of the formula R- S(=0) ₂ 0 ^~ wherein R is an alkyl group, preferably a C1- C10 alkyl group, more preferably a C1-C4 alkyl group. Examples of suitable C1- C10 alkyl groups are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2- ethylhexyl, 2 , 4 , 4-trimethylpentyl and decyl.

In the present invention, the anion from the ionic liquid may be hexafluorophosphate ion which is of the formula P F ₆ ^~ .

In the present invention, the anion from the ionic liquid may be an amide ion. The amide ion is of the formula R-N ^~ -R ' wherein R and R ' may be the same or different and are preferably electron-withdrawing

substituents . Electron-withdrawing substituents , in general, are substituents that draw electrons away from an electron rich place in a molecule, in this case from the electron rich nitrogen atom in said amide ion. Preferably, R and R' are selected from the group

consisting of cyano and alkanesulfonyl .

A particularly preferred amide ion is dicyanamide ion, that is to say an ion of said formula R-N ^~ -R' wherein both R and R' are cyano.

Said alkanesulfonyl substituent in said amide ion is of the formula R-S(=0)2 ^~ wherein R is an alkyl group, preferably a C ₁ -C ₁ 2 alkyl group, more preferably a C ₁ -C4 alkyl group, for example methyl, ethyl or n-butyl . Said alkyl group may be linear or branched. Further, said alkyl group may be substituted with one or more halogen atoms. Said alkanesulfonyl substituent is preferably a trihalogenmethanesulfonyl substituent which is of the formula CX3-S(=0)2 ^_ wherein X is a halogen atom selected from the group consisting of fluorine, chlorine, bromine and iodine. More preferably, said halogen atom is

fluorine. Most preferably, said trihalogenmethanesulfonyl substituent is trifluoromethanesulfonyl (CF ₃ -S (=0) 2 - ) · In the present invention, preferably, the ionic liquid comprises an N, N ' -dialkylimidazolium ion as described hereinabove as the cation and an amide ion or alkoxyphosphonate ion as described hereinabove as the anion Preferably, said N, N ' -dialkylimidazolium ion is 1- butyl-3-methylimidazolium ion or 1 , 3-dimethylimidazolium ion.

It is particularly preferred that the ionic liquid comprises an N, N ' -dialkylimidazolium ion as described hereinabove as the cation and dicyanamide ion as the anion. More preferably, said ionic liquid comprises 1- butyl-3-methylimidazolium ion and dicyanamide ion, which ionic liquid is exemplified in the Examples below.

Further, it is particularly preferred that the ionic liquid comprises an N, N ' -dialkylimidazolium ion as described hereinabove as the cation and

methoxyphosphonate ion as the anion. More preferably, said ionic liquid comprises 1 , 3-dimethylimidazolium ion and methoxyphosphonate ion

In the present invention, the catalyst is contacted with a solution comprising a solvent and said ionic liquid. The solvent in said solution comprising an ionic liquid may be any kind of solvent. For example, the solvent may be acetone.

In the present invention, contacting said catalyst with the solution comprising solvent and ionic liquid may be performed by spraying the solution onto the catalyst. Said spraying may be carried out with a nozzle capable of finely dispersing liquids.

In the present invention, after contacting the catalyst with the solution comprising solvent and ionic liquid, said solvent is to be removed. Such removal may be performed by any means known to a skilled person, such as drying. Drying of the impregnated catalyst may, for example, be carried out at any temperature between room temperature and 200 °C. Such drying can be carried out under static or dynamic conditions, for instance in a fixed bed, or in a moving bed.

The catalyst according to the present invention preferably can be used in a hydrogenation process, in particular a selective hydrogenation of a hydrocarbon feed comprising unsaturated hydrocarbons.

Accordingly, the technical problem of the present invention is also solved by a process for the

hydrogenation, preferably for the selective

hydrogenation, of a hydrocarbon feed, preferably

comprising a first and a second group of unsaturated hydrocarbons, wherein the hydrocarbon feed is contacted under suitable hydrogenating conditions with the catalyst according to the present invention and the unsaturated hydrocarbons in the hydrocarbon feed, preferably in the first group, are hydrogenated .

Preferably, the hydrocarbon feed in the hydrogenation process of the present invention comprises a first and a second group of unsaturated hydrocarbons. Said first group may contain undesired, that means highly

unsaturated hydrocarbons, in particular aromatics, alkynes and/or di-, tri- or polyunsaturated hydrocarbons, particularly alkadienes, alkatrienes or alkapolyenes , such as acetylene, propyne, propadiene, butadienes, vinylacetylene, butynes, phenylacetylene and/or styrene. Further, said second group may contain desired, that means less unsaturated hydrocarbons, in particular monounsaturated hydrocarbons, namely alkenes,

particularly ethylene. In particular, said first group comprises acetylene and said second group comprises ethylene .

Advantageously, in such preferred embodiment, the undesired first group of unsaturated hydrocarbons is removed, in particular hydrogenated, preferably to a desired less unsaturated hydrocarbon, thereby leaving the second group of unsaturated hydrocarbons in their

monounsaturated form. Thus, the present invention

provides a process for the selective hydrogenation of highly unsaturated hydrocarbons in the presence of less unsaturated hydrocarbons characterized by the use of a catalyst according to the present invention.

Preferably, the hydrocarbon feed in the hydrogenation process of the present invention comprises a first and a second group of unsaturated hydrocarbons, the first group of unsaturated hydrocarbons comprises acetylene, and the unsaturated hydrocarbons in the first group of

unsaturated hydrocarbons are selectively hydrogenated . Thus, the hydrocarbon feed may comprise in its first group of unsaturated hydrocarbons acetylene, in

particular in the presence of less unsaturated

hydrocarbons. Further, such hydrogenation process foresees to preferably reduce acetylene to ethylene, in particular in the presence of less unsaturated

hydrocarbons, preferably ethylene.

In a preferred embodiment acetylene is hydrogenated selectively to ethylene.

Further, the catalyst according to the present invention can be used in a hydrogenation process, in particular a selective hydrogenation of a hydrocarbon feed comprising unsaturated hydrocarbons as mentioned above, with a particular long catalyst lifetime allowing significantly increased cycle times. Based on the particular high durability of said catalyst,

hydrogenation processes can be repeated more often, before the catalyst has to be regenerated or in a continuous fixed bed the lifetime and/or conversion is increased. Advantageously, the catalyst according to the present invention reduces the formation of higher hydrocarbons .

In a preferred embodiment, the present hydrogenation process is carried out in the gas phase.

In a further preferred embodiment, the present

hydrogenation process is carried out according to the conditions of a front-end or tail-end hydrogenation process, preferably for the hydrogenation of C2 to C3 hydrocarbons .

In a preferred embodiment of the present

hydrogenation process, the hydrocarbon feed is contacted with the catalyst at a temperature of from 10 to 250 °C, preferably 30 to 200 °C, preferably 50 to 180 °C and in particular 60 to 120 °C.

In a preferred embodiment of the present

hydrogenation process, the hydrocarbon feed is contacted with the catalyst at a pressure of from 0.5 to 90 bar, preferably 0.5 to 60 bar, preferably 5 to 20 bar and in particular 10 to 20 bar.

In a preferred embodiment of the present

hydrogenation process, the hydrocarbon feed is conducted with the catalyst at a GHSV (gas hourly space velocity) from 1000 to 15000 v/vh, 3000 to 12000 v/vh, preferably 3000 to 7000 v/vh and in particular 3000 to 4000 v/vh. "v/vh" stands for volume gas per volume catalyst per hour.

In a preferred embodiment of the present

hydrogenation process, the hydrocarbon feed is contacted with a catalyst without the use of carbon monoxide as moderator. Furthermore, the hydrogenation can be carried out without carbon monoxide, namely is a monocarboxide- free process.

In a preferred embodiment of the present

hydrogenation process, the molar ratio of hydrogen to acetylene is of from 0.8 to 1.8, preferably 1.0 to 1.5 and in particular 1.0 to 1.3.

In a preferred embodiment of the present

hydrogenation process, the molar ratio of hydrogen to acetylene is of from 1.8 to 100, preferably 1.8 to 70, preferably 1.8 to 30 and in particular 1.8 to 10.

In a preferred embodiment of the present

hydrogenation process, the hydrocarbon feed is contacted with hydrogen to obtain the hydrogenated products. The invention is further illustrated by the following Examples .

Example 1

20 g of a supported metal containing catalyst, comprising alpha-alumina as the support and containing

0.035 wt . % of palladium and 0.015 wt . % of silver as the catalytically active metals (based on the total weight of the catalyst), were placed on a plate. Said catalyst was manufactured by consecutive impregnation of palladium and silver on the alumina support with a drying step after each impregnation. The drying steps were carried out in air between 120 and 150 °C. The dried catalyst

impregnated with palladium and silver was calcined in nitrogen at 630 °C for 5 hours.

A solution of 0.5 g of l-butyl-3-methylimidazolium dicyanamide (BMIM dicyanamide) in 10 ml of acetone was prepared. The catalyst on the plate was contacted with said solution by applying the solution onto the catalyst dropwise during a period of time of 30 minutes. The resulting impregnated catalyst was dried at room

temperature for 24 hours.

Example 2

The procedure of Example 1 was repeated, with the exception that a solution of 1.0 g of BMIM dicyanamide in 10 ml of acetone was used.

Hydrogenation experiments

The catalytic performances of the catalysts obtained in Examples 1 and 2 were measured, and compared with that of the untreated catalyst (which had not been treated with an ionic liquid) , in the following hydrogenation experiment. Experimental conditions were chosen which closely resembled those of a first reactor of a technical tail end reactor: 1.3 g catalyst

dilution (silica beads)

GHSV 4,000 v/vh

feed composition (mole %) : C ₂ H ₄ (30), C ₂ H ₂ (1.0), H ₂ (1.0), C ₃ H ₈ (1.0), Ar (rest)

pressure: 10 bar

In the table below, the conversion of acetylene ("X") and the selectivity towards ethylene ("S") at different temperatures are shown for the catalysts of Examples 1 and 2 and for the untreated catalyst (Comparison

Example) .

The conversion of acetylene ("X") was calculated as follows: [(acetylene inlet concentration - acetylene outlet concentration) /acetylene inlet concentration] *100.

The selectivity towards ethylene ("S") was calculated as follows: [(ethylene outlet concentration - ethylene inlet concentration) / (acetylene inlet concentration - acetylene outlet concentration) ] *100.

From the table it is evident that the treatment according to the present invention results in catalysts which exhibit a better selectivity.