WO2019102153A1 - Catalyst for the preparation of alpha-olefin trimers - Google Patents

Abstract

The invention relates to a chromium catalyst having formula (I), wherein: R1, R2 and R3 are identical and represent a hydrocarbon radical comprising between 1 and 36 carbon atoms and optionally one or more heteroatoms selected from among oxygen and nitrogen, on the understanding that if R1, R2 and R3 consist of hydrogen and carbon atoms then at least one of said radicals, R1, R2 or R3, represent(s) branched pentyl groups; and X₁, X₂ and X₃ represent, independently of one another, a halogen atom.

Description

 CATALYST FOR THE PREPARATION OF ALPHA-OLEFIN TRIMERS (S)

Technical area

 The present invention relates to a chromium catalyst and a process for oligomerizing alpha-olefins using said catalyst to obtain trimers with a conversion rate and / or a high yield.

Technological background

 In the API classification of base oils, polyalphaolefins (PAO) are referenced as Group IV base oils. Thanks to a good compromise between viscosity, volatility and cold properties, these PAOs are increasingly used in high performance lubricant formulations. In particular, this better compromise is very advantageous compared with the mineral bases, in particular of group II.

 In general, PAOs are synthesized from different olefinic monomers, in particular from C 6 -C 14 monomers, by acid catalysis or in the presence of a metallocene catalyst.

 In general, to prepare low viscosity products whose grades range from 2 to 10, acid catalysts are used.

Methods for the preparation of PAO by metallocene catalysis are known, generally leading to products of high viscosity whose kinematic viscosity at 100 ° C., measured according to ASTM D445, ranges from 40 to 150 mm ² . s ¹ (grades 40 to 150).

 In addition, the need for high performance lubricants is increasing. In particular, because of the conditions of use whose severity increases, for example because of temperatures or very high mechanical stresses.

 Drainage spacing and reduced size of lubrication systems also increase the need for high performance lubricants.

 Energy efficiency and in particular the improvement of the Fuel Eco (FE) of lubricants or the reduction of the fuel consumption of engines, in particular of vehicle engines, are increasingly important objectives and lead to the increasing use of high performance lubricants.

 High performance lubricants must therefore have improved properties, in particular as regards kinematic viscosity, viscosity index, volatility, dynamic viscosity or cold pour point.

 Thermal stability and oxidation resistance are also properties to be improved for high performance lubricants.

Reduced toxicity and good miscibility with other lubricants or other materials are also properties to look for high performance lubricants. Furthermore, improved PAO preparation methods must also be developed, in particular to improve the yield or selectivity of these processes. The improvement of the catalytic activity must also be aimed at.

 Thus, the present invention provides a novel easy-to-manufacture catalyst for catalyzing an oligomerization reaction of alpha-olefins having a high yield and a high selectivity and allowing, by hydrogenation of the obtained trimers, to prepare PAOs having satisfactory properties. , especially for high performance lubricant applications.

Summary of the invention

 The subject of the present invention is a chromium catalyst corresponding to formula (I):

in which :

 R 1, R 2 and R 3 are identical and represent a hydrocarbon radical comprising from 1 to 36 carbon atoms and optionally one or more heteroatoms chosen from oxygen and nitrogen, it being understood that if R 1, R 2 and R 3 are composed of carbon atoms and then said R 1, R 2, R 3 radicals represent branched pentyl groups;

X ₁ , X ₂ and X ₃ represent, independently of one another, a halogen atom.

According to one embodiment, the catalyst according to the invention is characterized in that:

 the groups R1, R2 and R3 represent branched pentyl groups, or the groups R1, R2 and R3 are substituted by a nitrogen atom, preferably the groups R1, R2 and R3 represent groups of formula: -Chh-Chh- NR'R "wherein R 'and R" are preferably identical and represent an alkyl radical comprising 1 to 8 carbon atoms, preferably 3 to 6 carbon atoms, preferably 6 carbon atoms.

 According to one particular embodiment of the invention, the catalyst corresponds to formula (Ia):

Ou à la formule (Ib) :

Or in the formula (Ib):

The subject of the invention is also a process for producing the catalyst according to the invention, comprising:

 The reaction of primary alkylamine (s) in the presence of polyoxymethylene, followed by the reaction of the product from the previous step with a halochromate complex.

The invention also relates to a process for the preparation of alpha-olefin trimers, comprising the oligomerization of alpha-olefin (s) in the presence of a catalyst according to the invention and an activator compound .

 According to one embodiment of the process for preparing alpha-olefin trimers according to the invention, the alpha-olefin (s) are chosen from linear alpha-olefins comprising from 3 to 18 carbon atoms, preferably from 4 to 16 carbon atoms, preferably 5 to 14 carbon atoms, more preferably 6 to 12 carbon atoms, even more preferably 8 to 10 carbon atoms.

 According to one embodiment of the invention, the oligomerization is carried out at a temperature greater than or equal to 5 ° C., preferably at a temperature ranging from 10 ° C. to 50 ° C., preferably ranging from 15 ° C. to 40 ° C. ° C, preferably ranging from 20 ° C to 35 ° C.

 According to one embodiment of the invention, the oligomerization is carried out using homogeneous catalysis, preferably in the presence of at least one solvent chosen from hydrocarbons, halogenated hydrocarbons, and mixtures thereof, preferably among hydrocarbons such as toluene, benzene, n-hexane, n-heptane, cyclohexane or xylenes and halogenated hydrocarbons such as dichlorobenzene.

 According to one embodiment of the invention, the activator compound is chosen from aluminoxanes, ionic activators and mixtures thereof.

 According to one embodiment, the activator compound is an aluminoxane, preferably an alkylaluminoxane, the alkyl group of which is preferably chosen from linear or branched alkyl groups comprising from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms. carbon, preferably from 1 to 3 carbon atoms.

According to another embodiment, the activator compound is an ionic activator, preferably chosen from dimethylanilinium tetrakis- (perfluorophenyl) borate (DMAB), the triphenylcarbonium tetrakis- (perfluorophenyl) borate, dimethylanilinium tetrakis- (perfluorophenyl) aluminate and mixtures thereof.

According to one embodiment of the process according to the invention, the molar ratio catalyst / alpha-olefin (s) ranges from 1/10000 to 1/500, preferably from 1/8000 to 1/1000, and / or the catalyst molar ratio. / activator compound is from 1/500 to 1/1, preferably from 1/400 to 1/100, preferably from 1/350 to 1/200.

 According to one embodiment of the process according to the invention, the oligomerization is carried out in the presence of a co-activator compound, preferably chosen from trialkylaluminium derivatives, where the alkyl group preferably has from 1 to 16 carbon atoms, preferably from 2 to 10 carbon atoms.

 According to one embodiment of the invention, the process for preparing alpha-olefin trimers (s) further comprises a hydrogenation reaction in the presence of a hydrogenation catalyst.

The catalyst according to the invention can be prepared by a simple process from widely available raw materials.

 The catalyst according to the invention is particularly effective for the oligomerization of alpha-olefins.

 The oligomerization process according to the invention makes it possible to obtain a high conversion rate as well as a high selectivity towards obtaining trimers.

Detailed description of the invention

 The present invention relates to a chromium catalyst of formula (I):

in which :

 R 1, R 2 and R 3 are identical and represent a hydrocarbon radical comprising from 1 to 36 carbon atoms and optionally one or more heteroatoms chosen from oxygen and nitrogen, it being understood that if R 1, R 2 and R 3 consist of carbon atoms and then said R 1, R 2, R 3 radicals represent branched pentyl groups;

X ₁ , X ₂ and X ₃ represent, independently of one another, a halogen atom.

The catalyst of the invention is a complex type chromium catalyst in which the chromium atom is linked to a triazacyclohexane type ring by bonding between the chromium atom and the nitrogen atoms. of the triazacyclohexane ring. The bond of the chromium atom to the ring may be of the covalent or non-covalent type.

The groups R 1, R 2 and R 3 are hydrocarbon groups optionally substituted by one or more heteroatoms chosen from oxygen or nitrogen. Thus, the groups R 1, R 2 and R 3 as defined in the present invention do not comprise hetero atoms different from oxygen or nitrogen. By way of example, the groups R 1, R 2 and R 3 typically do not comprise chlorine or bromine atoms.

 According to one embodiment, the groups R 1, R 2 and R 3 are hydrocarbon groups consisting of carbon and hydrogen atoms.

According to one embodiment, the radicals R1, R2 and R3 represent the isoamyl radical of formula: -CH ₂ -CH ₂ -CH (CH ₃ ) ₂ .

 According to another embodiment, the groups R 1, R 2 and R 3 are hydrocarbon groups substituted with a nitrogen atom. According to this embodiment, the groups R1, R2 and R3 are preferably groups of formula: -Chb-Chh-NR'R "where R 'and R" are preferably identical and represent an alkyl radical comprising from 1 to 8 carbon atoms, preferably from 3 to 6 carbon atoms, preferably 6 carbon atoms.

According to a very particular embodiment, at least one of the groups R1, R2 and R3 represents either a -CH2-CH2-CH (CHB) 2 0U group or a -CH ₂ -CH ₂ -N (CH ₃ ) _{2 group} .

According to one embodiment of the invention, the atoms X ₁ , X ₂ and X ₃ are identical and preferably each represent a chlorine atom.

 According to a particular embodiment, the catalyst according to the invention corresponds to the following formula (la):

According to one particular embodiment, the catalyst according to the invention corresponds to the following formula (Ib):

Le catalyseur selon l'invention peut être un catalyseur homogène ou hétérogène. Selon un mode de réalisation préféré de l'invention, le catalyseur est un catalyseur homogène, i.e. permettant d'effectuer une catalyse homogène. Autrement dit, lors du procédé d'oligomérisation, le catalyseur sera de préférence soluble dans le milieu réactionnel. Ainsi, le catalyseur de l'invention est selon un mode de réalisation préféré, non lié à un support solide, tel que la silice.

The catalyst according to the invention may be a homogeneous or heterogeneous catalyst. According to a preferred embodiment of the invention, the catalyst is a homogeneous catalyst, ie for performing homogeneous catalysis. In other words, during the oligomerization process, the catalyst will preferably be soluble in the reaction medium. Thus, the catalyst of the invention is according to a preferred embodiment, not bound to a solid support, such as silica.

The invention also relates to a method of manufacturing the catalyst according to the invention.

The catalyst of formula (I) can be obtained from primary alkylamine (s) of formula (IIia) RI-NH ₂ , (IIIb) R ₂ -NH ₂ and (IIIc) R 3 -NH ₂ , being understood that R1, R2 and R3 may be identical or different and have the meaning given in formula (I) above, according to the following protocol:

 In a first step, one or more primary alkyl amines are left at room temperature in the presence of a polyoxymethylene, such as paraformaldehyde, and a solvent, such as toluene, for a period ranging from 12 to 24 hours, to obtain the triazacyclohexane compound of formula (II) according to the following scheme:

I

 lllc R3

In a second step, the compound of formula (II) is reacted with a halochromic complex, for example of formula CrXiX ₂ Xs (THF) ₃ , where X ₁ , X ₂ and X ₅ have the meaning given for formula (I) above, in the presence of a solvent such as dichloromethane, to obtain the compound of formula (I), according to the following reaction scheme:

According to a preferred embodiment, the groups R 1, R 2 and R 3 are identical, in this case the compounds of formula (Ilia), (IIIb) and (IIIc) are identical.

The catalyst according to the invention can be used for the oligomerization of alpha-olefins. Thus, the invention also relates to a process for the preparation of alpha-olefin trimers, comprising the oligomerization of alpha-olefins in the presence of a chromium catalyst according to the invention and an activator compound. Alpha-olefins

 The process for preparing trimers according to the invention uses, as reactants, at least one alpha-olefin. For the purposes of the present invention, the term "alpha-olefins" is intended to mean an olefin having a carbon-carbon double bond in the alpha position (also called the terminal position).

 According to one embodiment, the process uses a single alpha-olefin.

According to one embodiment, the alpha-olefin is a linear alpha-olefin, preferably having a single carbon-carbon double bond.

 According to one embodiment, the alpha-olefin comprises from 3 to 18 carbon atoms, preferably from 4 to 16 carbon atoms, preferentially from 5 to 14 carbon atoms, more preferably from 6 to 12 carbon atoms, still more preferably 8 to 10 carbon atoms. According to a particular embodiment, the alpha-olefin is chosen from 1-butene, 1-hexene, 1-octene and 1-decene, preferably the alpha-olefin is 1-decene.

 According to a particular embodiment, the process uses a single alpha-olefin comprising from 6 to 12 carbon atoms.

 Alpha-olefins are products that can be commonly found in commerce. They can be obtained by oligomerization of ethylene, according to methods well known to those skilled in the art.

 According to one embodiment of the invention, the catalyst / alpha-olefin (s) molar ratio ranges from 1/10000 to 1/100, preferably from 1/8000 to 1/100.

Catalyst

 The catalyst used in the process of the invention is a chromium catalyst of formula (I) according to the present invention. The catalyst used for the oligomerization according to the invention may have one or more of the characteristics defined above.

 According to a particular embodiment, the catalyst used for the oligomerization corresponds to the formula (la) defined above.

 For the process for preparing trimers according to the invention, the catalyst is used in an activated form for the oligomerization of alpha-olefins. Thus, the process according to the invention uses an activator compound during the oligomerization of alpha-olefins.

Activator compound

 The activator compound may be chosen from aluminoxanes, ionic activators and mixtures thereof.

According to one embodiment of the invention, the oligomerization process is carried out with a catalyst / activator compound molar ratio ranging from 1/500 to 1/1, preferably from 1/400 to 1/100, preferably from 1/350 to 1/200. According to one embodiment of the oligomerization process according to the invention, the activator compound is an aluminoxane. Preferably, the aluminoxane used according to the invention is an oligomeric compound comprising units of formula -AI (R) -O- in which R independently represents a linear, branched or cyclic C ₁ -C ₂₀ alkyl group. Preferably, R represents an alkyl group comprising from 1 to 16 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 8 carbon atoms. Preferably, the aluminoxane is chosen from methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, isobutylaluminoxane and mixtures thereof. The methylaluminoxane is advantageously used.

 The aluminoxane can be used in solution in a solvent. Preferably, said solvent is selected from toluene, benzene, n-hexane, n-heptane, cyclohexane and xylenes, preferentially from toluene, benzene and xylenes.

 According to one embodiment of the oligomerization process according to the invention, the activator compound is an ionic activator. The ionic activator may be selected from dimethylanilinium tetrakis- (perfluorophenyl) borate (DMAB), triphenylcarbonium tetrakis- (perfluorophenyl) borate, dimethylanilinium tetrakis- (perfluorophenyl) aluminate and mixtures thereof. For example, the ionic activator may be tetrakis- (perfluorophenyl) borate dimethylanilinium (DMAB).

Coactivator

 During the trimerization reaction, it is possible to use a co-activator compound. A coactivator compound is particularly advantageous when the activator compound is an ionic activator.

 According to one embodiment, the coactivator compound is chosen from trialkylaluminium derivatives, alkylaluminoxanes (MAO), modified alkylaluminoxanes (MMAO) and alkylaluminium chloride, the alkyl groups preferably comprising from 1 to 16 carbon atoms. preferably from 1 to 10 carbon atoms.

 Preferably, the coactivator compound is a trialkylaluminium derivative, in which the alkyl group preferably has 1 to 16 carbon atoms, preferably 2 to 10 carbon atoms. More preferably, the co-activator compound is selected from triethyl aluminum (TEAL), tri-iso-butyl aluminum (TIBAL), tri-methyl aluminum (TMA), tri-n-octyl aluminum and methyl methyl ethyl aluminum (MMEAL). Advantageously, triisobutylaluminum (TIBAL) is used as coactivator.

 Advantageously, tri-iso-butyl aluminum (TIBAL) is used in the form of a dispersion that can range from 10 to 60% by weight.

According to one embodiment, the coactivator compound is used in a catalyst / co-activator molar ratio ranging from 1/500 to 1/1, preferably from 1/400 to 1/100, preferably from 1: 1 to 1: 1. 350 to 1/200, more preferably 1/100 to 1, even more preferably 1/75 to 1/10, or even 1/50 to 1/20. Solvent

 As indicated above, the activator may be in solution in a solvent. The alpha-olefin, the starting material, can also act as a solvent for the reaction.

 According to a particular embodiment of the invention, the oligomerization process is carried out in the presence of a solvent, different from the starting alpha-olefin. Preferably, the solvent is chosen from linear, branched or cyclic hydrocarbons, aromatic compounds, halogenated hydrocarbons, halogenated aromatic compounds, and mixtures thereof. Advantageously, the solvent is chosen from butanes, pentanes, hexanes, heptanes, octanes, cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, methylcycloheptane, toluene, xylenes, diflurobenzenes, and mixtures thereof.

Oligomerization reaction

 The process according to the invention allows the trimerization of alpha-olefin (s) starting, in the presence of a catalyst and an activator compound. Thus, the process makes it possible to obtain one or more alpha-olefin trimers.

 Advantageously, the process is carried out starting from a single alpha-olefin and the reaction mixture obtained at the end of the oligomerization reaction comprises at least 50% by weight, preferably at least 60% by weight. preferably at least 70% by weight of trimer (s) of said alpha-olefin, expressed relative to the total weight of the reaction mixture.

 For the purposes of the present invention, the term "reaction mixture" is intended to mean the mixture consisting of the starting alpha-olefin, the trimers of the alpha-olefin, and any oligomers formed other than the trimers. For the purposes of the present invention, the "reaction mixture" does not include the catalyst, the solvent, the activator compound or the coactivator compound.

According to one embodiment of the invention, the oligomerization reaction is carried out at a pressure ranging from 0.1 to 10 bar, preferably from 0.5 to 5 bar, preferably at a pressure ranging from 0.5 to 2 bar, preferably at a pressure of about 1 bar.

 According to one embodiment of the invention, the oligomerization reaction is carried out at a temperature ranging from 5 to 60 ° C., preferably from 10 to 50 ° C., preferably from 15 to 40 ° C., more preferably from 20 to 60 ° C. 35 ° C.

According to one embodiment of the invention, the oligomerization process is carried out in continuous mode. According to this embodiment, the alpha-olefin, the catalyst, the activator compound and optionally the coactivator compound are introduced continuously so as to keep constant the catalyst / alpha-olefin molar ratio and the catalyst / molar ratio. activator compound and optionally the molar ratio of co-activator / catalyst compound. According to this embodiment, the reactor may be a reactor for continuous reaction with stirring (CSTR, "continuous stirred tank reactor" in English). Still, according to this continuous embodiment, the reaction products can be continuously separated at the outlet of the reactor. hydrogenation

After oligomerization of the alpha-olefin (s), the trimers obtained can be hydrogenated. According to one embodiment of the invention, the process according to the invention comprises a catalytic hydrogenation of the products obtained at the end of the oligomerization. The catalytic hydrogenation is then carried out in the presence of hydrogen (H ₂ ) and a hydrogenation catalyst.

 Preferably, the hydrogenation catalyst is chosen from a palladium derivative, a supported palladium derivative, a palladium derivative supported on alumina (for example on gamma-alumina), a nickel derivative, a supported nickel derivative, a derived from nickel supported on kieselguhr, a platinum derivative, a supported platinum derivative, a cobalt-molybdenum derivative, a supported cobalt-molybdenum derivative. More preferably, the hydrogenation catalyst comprises palladium. A particularly preferred hydrogenation catalyst comprises palladium supported on alumina (for example on gamma-alumina).

Also preferably, the hydrogen pressure (H ₂ ) during the catalytic hydrogenation of the oligomerization products is from 5 to 150 bar, more preferably from 10 to 140 bar, in particular from 15 to 125 bar.

Deactivation and recycling

 According to one embodiment, once the oligomerization of the alpha-olefin (s) has been carried out, the process according to the invention may comprise the deactivation of the catalyst.

 The deactivation of the oligomerization catalyst can be carried out after the oligomerization of the alpha-olefin (s) or after the catalytic hydrogenation of the oligomerization products. Preferably, the deactivation of the oligomerization catalyst is carried out after the oligomerization of the alpha-olefin (s) and before the catalytic hydrogenation of the oligomerization products.

 Advantageously, the deactivation of the catalyst is carried out by the action of air or water or by means of at least one alcohol or a solution of deactivating agent. Preferably, the deactivation of the catalyst is carried out using at least one alcohol, for example isopropanol.

It is also possible to provide for the recycling of the unconverted alpha-olefin (s) as well as any dimers of the alpha-olefins at the end of the oligomerization reaction. The recycled alpha-olefin (s) and / or the dimers can thus be reintroduced into the starting alpha-olefin (s) to carry out the oligomerization reaction according to the invention.

According to a particular embodiment of the invention, the method for preparing trimers comprises the following steps:

a) adding the activator compound, and optionally the coactivator compound, to the chromium catalyst, b) Mixing of the ingredients of step a),

 c) adding the alpha-olefin to the mixture resulting from step b),

 d) Oligomerization reaction.

In a preferred manner, the method according to the invention comprises the following characteristics:

 The catalyst has formula (Ia) or (Ib); and

 The activator compound is an aluminoxane.

According to one embodiment, the method according to the invention comprises the following characteristics:

 The oligomerization temperature is greater than or equal to 20 ° C; and

 The activator compound is an aluminoxane; and

 A trialkylaluminum co-activator compound is used where the alkyl group has 2 to 10 carbon atoms.

Advantageously, the method according to the invention comprises the following characteristics:

 The activator compound is an aluminoxane; and

 Catalysis is homogeneous catalysis; and

 The catalyst has formula (Ia) or (Ib).

In a particularly advantageous manner, the process according to the invention comprises the following characteristics:

 The oligomerization temperature is greater than or equal to 20 ° C; and

 The activator compound is an aluminoxane; and

 The catalyst has formula (Ia) or (Ib).

In a particularly advantageous manner, the process according to the invention comprises the following characteristics:

 The activator compound is an aluminoxane;

 A trialkylaluminum co-activator compound is used where the alkyl group has 2 to 10 carbon atoms.

According to an advantageous embodiment, the method according to the invention comprises the following characteristics:

The activator compound is a methylaluminoxane or an ethylaluminoxane; and the catalyst has formula (Ia) or (Ib). The process for preparing trimers according to the invention makes it possible to prepare trimers in the form of an oil having advantageous characteristics.

Indeed, the oil thus prepared has a kinematic viscosity at 100 ° C ranging for example from 2 to 5 mm ² . s ¹ , preferably from 3 to 4 mm ² . ¹ , measured according to ISO 3104.

 The oil prepared according to the invention generally has a viscosity index greater than 120 or ranging from 120 to 140 or from 125 to 135, measured according to the ASTM D2270 standard.

The process for preparing trimers according to the invention makes it possible to prepare an oil which can be used as a base oil or as a lubricating base oil.

 The process according to the invention makes it possible to prepare an oil which can also be used to improve the Fuel Eco (FE) of a lubricant, to reduce the fuel consumption of an engine or to reduce the fuel consumption of a fuel. vehicle engine.

 The process according to the invention makes it possible to prepare an oil which can be incorporated into a lubricating composition. Advantageously, this lubricating composition may comprise at least 10% by weight or at least 20% by weight of an oil prepared according to the invention. Also advantageously, this lubricating composition may comprise at least 30, 40, 50 or 60% by weight of an oil prepared according to the invention.

 Also advantageously, this lubricating composition may comprise an oil prepared according to the invention and at least one other base oil. It may also comprise an oil prepared according to the invention and at least one additive or an oil prepared according to the invention, at least one other base oil and at least one additive.

 As another oil-base base oil prepared according to the invention, this lubricating composition may comprise an oil selected from a Group III oil, a Group IV oil.

 The lubricant composition is particularly advantageous for use as a high performance lubricant for lubrication in the fields of engines, gears, braking, hydraulic fluids, refrigerants, greases. This lubricant composition can also improve the fuel Eco (FE) of a lubricant, reduce the fuel consumption of an engine or reduce the fuel consumption of a vehicle engine.

The following examples illustrate the invention without limiting it.

Example 1: Preparation of the catalyst

A catalyst (compound 3) corresponding to the formula (I) defined in the present invention was prepared according to the following reaction scheme:

EXAMPLE 1 Synthesis of Compound 2 ((CH ₃ ) ₂ CHCH ₂ CH ₂ ) ₃ TAC

 Compound 1 (871.6 mg, 1.2 mL, 10 mmol, commercially available) is dissolved in freshly distilled toluene (10 mL) at room temperature (23 ° C), followed by polyformaldehyde (0.3 g, 10 mL). mmol) is added and the mixture is stirred for 12 to 24 hours until complete solubilization of paraformaldehyde. A yield of 63% is obtained.

Example 1b: Synthesis of [((CH 2 CHCH CH 1 TACCrCl] (Compound 3)

Compound 2 (158.8 mg, 0.53 mmol, 1 equivalent) is dissolved in chlorobenzene (50 mL) and one equivalent of CrO ₃ (THF) ₃ (100.7 mg, 0.53 mmol, 1 equivalent) is added. The reaction mixture is stirred for 12 to 24 hours. Purification on a silica column (dried for 3 hours at 400 ° C. in vacuo) is then carried out with a dichloromethane eluent. A yield of 65% is obtained.

Example 2 Oligomerization of 1-decene

An oligomerization process was carried out according to the following protocol:

 In a glove box, a pillbox with septum provided with a magnetic bar, previously dried in an oven (100 ° C, minimum 15h) is loaded with the chromium catalyst (compound 3). Under argon flow, with the aid of a syringe, 1-decene (2mL, 10.6mmol) and the solvent (PhCl, lmL) are subsequently added, followed by MAO (250 equivalents / Cr catalyst). ). The reaction is stirred at room temperature for 15h, before being quenched.

The product obtained is then treated as follows: addition of 2 ml of permutated water, an external standard (dodecane, approximately 0.3 ml) accurately weighed, and a few drops of HCl to allow the passage of metal salts in the aqueous phase. Extraction of the organic phase with 4mL * 2 and then 2mL of pentane. Wash the organic phase with 2 * 2mL of deionized water and dry over MgSC. The organic phase is then filtered and diluted 100 ^e in pentane, 0.45 μm PTFE filter filtration, before being injected into GC.

Preferably, the solvents and reagents that have been used have been degassed and stored on sieves.

AT.

Table 1 groups together the amounts of reagents / solvents used.

 TABLE 1 Amount of reagents used for the oligomerization of Example 2

 (1) Molar equivalent of compound i = molar amount of compound i divided by molar amount of catalyst

The oligomerization reaction is carried out at 25 ° C for 18h. The 1-decene trimers (C30) are obtained with a yield of 85%.

 For the purposes of the present invention, the yield is defined with respect to the decene introduced originally.

Claims

1. A chromium catalyst having formula (I):

 in which :  R 1, R 2 and R 3 are identical and represent a hydrocarbon radical comprising from 1 to 36 carbon atoms and optionally one or more heteroatoms chosen from oxygen and nitrogen, it being understood that if R 1, R 2 and R 3 are composed of carbon atoms and then said R 1, R 2, R 3 radicals represent branched pentyl groups; X ₁ , X ₂ and X ₃ represent, independently of one another, a halogen atom. Catalyst according to claim 1, wherein:  the groups R1, R2 and R3 are substituted by a nitrogen atom, preferably the groups R1, R2 and R3 represent groups of formula: -Chh-Chh-NR'R "where R 'and R" are preferably identical and represent an alkyl radical comprising from 1 to 8 carbon atoms, preferably from 3 to 6 carbon atoms, preferentially 6 carbon atoms. Catalyst according to Claim 1, having formula (Ia):

4. Catalyst according to any one of claims 1 to 2, corresponding to formula (Ib):

Process for the production of the catalyst according to any one of claims 1 to 4, comprising:  The reaction of primary alkylamine (s) in the presence of polyoxymethylene, followed by the reaction of the product from the previous step with a halochromate complex. 6. Process for the preparation of alpha-olefin trimers, comprising the oligomerization of alpha-olefin (s) in the presence of a catalyst according to any one of claims 1 to 4 and an activator compound . 7. Process according to claim 6, in which the alpha-olefin (s) are (are) chosen from linear alpha-olefins comprising from 3 to 18 carbon atoms, preferably from 4 to 16 carbon atoms, preferably from 5 to 14 carbon atoms. carbon, more preferably from 6 to 12 carbon atoms, even more preferably from 8 to 10 carbon atoms. 8. Process according to claim 6 or 7, in which the oligomerization is carried out at a temperature greater than or equal to 5 ° C, preferably at a temperature ranging from 10 ° C to 50 ° C, preferably ranging from 15 ° C at 40 ° C, preferably ranging from 20 ° C to 35 ° C. 9. Process according to any one of claims 6 to 8, in which the oligomerization is carried out using homogeneous catalysis, preferably in the presence of at least one solvent chosen from hydrocarbons and halogenated hydrocarbons. and mixtures thereof, preferably from hydrocarbons such as toluene, benzene, n-hexane, n-heptane, cyclohexane or xylenes and halogenated hydrocarbons such as dichlorobenzene. The process according to any one of claims 6 to 9, wherein the activator compound is selected from aluminoxanes, ionic activators and mixtures thereof. The process according to claim 10, wherein the activator compound is an aluminoxane, preferably an alkylaluminoxane, the alkyl group of which is preferably selected from the group consisting of linear or branched alkyl groups comprising from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms. The process according to claim 10, wherein the activator compound is an ionic activator, preferably selected from dimethylanilinium tetrakis- (perfluorophenyl) borate (DMAB), triphenylcarbonium tetrakis- (perfluorophenyl) borate, dimethylanilinium tetrakis- (perfluorophenyl) aluminate and mixtures thereof. 13. Process according to one of Claims 6 to 12, in which the catalyst / alpha-olefin (s) molar ratio ranges from 1/10000 to 1/500, preferably from 1/8000 to 1/1000, and / or catalyst / activator compound molar ratio ranges from 1/500 to 1/1, preferably from 1/400 to 1/100, preferably from 1/350 to 1/200. 14. Process according to one of Claims 6 to 13, in which the oligomerization is carried out in the presence of a coactivator compound, preferably chosen from trialkylaluminium derivatives, in which the alkyl group preferably has from 1 to 16 atoms. carbon, preferably 2 to 10 carbon atoms. 15. Method according to one of claims 6 to 14, further comprising a hydrogenation reaction in the presence of a hydrogenation catalyst, after the oligomerization step.