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EP-4739718-A1 - PRODUCTION OF POLY-ALPHA-OLEFINS

EP4739718A1EP 4739718 A1EP4739718 A1EP 4739718A1EP-4739718-A1

Abstract

Current invention describes a process for producing poly-α-olefins, the process comprises providing at least one α-olefin monomer and a catalyst, and letting the at least one α-olefin monomer react in the presence of the catalyst to form a mixture of poly-α-olefins (PAO). The obtained mixture of poly-α-olefins is fractionated to two PAO fractions wherein the two PAO fractions are a first fraction of PAO having a kinematic viscosity of 5 cSt or lower and a second fraction of PAO having a kinematic viscosity of more than 5 cSt. Optionally a recycle fraction is also obtained in the fractionation and at least a part of the recycle fraction comprising dimers of the α- olefins can be recycled back to the reaction step. The process further comprises a step where the obtained two PAO fractions are directly subjected to separate hydrogenation to obtain hydrogenated PAO fractions.

Inventors

  • Wahlström, Jan
  • Vikman, Kim

Assignees

  • Neste Oyj

Dates

Publication Date
20260513
Application Date
20240704

Claims (7)

  1. 1. A process for producing poly-a-olefins, the process comprising a] providing at least one a-olefin monomer and a catalyst, b] letting the at least one a-olefin monomer react in the presence of the catalyst to form a mixture of poly-a-olefins [PAO], c] fractionating the obtained mixture of poly-a-olefins to two PAO fractions, wherein the two PAO fractions are a first fraction of PAO having a kinematic viscosity of 5 cSt or lower and a second fraction of PAO having a kinematic viscosity of more than 5 cSt; and optionally a recycle fraction, of which at least a part is recycled back to the reaction step, and the recycle fraction comprises dimers of the a-olefins, d] subjecting the obtained two PAO fractions to separate hydrogenation to obtain hydrogenated PAO fractions, and e] optionally further fractionating at least one of the hydrogenated PAO fractions to obtain hydrogenated PAO sub-fractions.
  2. 2. The process according to claim 1, wherein the obtained two PAO fractions are hydrogenated in separate hydrogenation units.
  3. 3. The process according to claim 1 or 2, wherein the process comprises a further fractionation step e] and the further fractionation step e] is performed on the hydrogenated PAO fraction having a kinematic viscosity of 5 cSt or lower to obtain a first hydrogenated PAO sub-fraction having a kinematic viscosity of about 2 cSt and a second hydrogenated PAO sub-fraction having a kinematic viscosity of about 4 cSt.
  4. 4. The process according to any one of the previous claims, wherein the at least one a-olefin monomer comprises C4 - C20 a-olefins, preferably Cs - C12 a- olefins and more preferably C10 a-olefin.
  5. 5. The process according to any one of the previous claims, wherein the catalyst is a catalyst complex comprising a primary catalyst and a co-catalyst and the primary catalyst is preferably an aluminium halide or a boron halide, more preferably the primary catalyst is BF3, and the co-catalyst is preferably selected from C1-C10 alcohols, and more preferably the co-catalyst is n-butanol.
  6. 6. The process according to any one of the previous claims, wherein the hydrogenation is performed in the presence of a noble metal or nickel catalyst in a fixed bed reactor.
  7. 7. The process according to any one of the previous claims, wherein the hydrogenation is performed in a pressure from 2 MPa to 10 MPa, preferably from 2.5 MPa to 8 MPa, more preferably from 3 MPa to 6 MPa; a temperature from 100 °C to 320 °C, preferably from 120 °C to 280 °C, more preferably from 130 °C to 250 °C.

Description

PRODUCTION OF POLY-ALPHA-OLEFINS FIELD OF THE INVENTION The present invention relates to a process for producing poly-a-olefins from a-olefin monomers. More particularly the invention relates to a process for producing poly-a-olefins where the product mixture is fractionated to two product fractions and the product fractions are hydrogenated separately. The present invention therefore provides a simple process, which can be continuous, for producing poly-a-olefins of high quality, with good yield and optimal process and equipment set-up. BACKGROUND OF THE INVENTION Oligomerisation reaction of a-olefins to form various grades of components useful in production of synthetic lubricants are well known. The production method generally includes oligomerisation of the a-olefin monomers using a catalyst or a catalyst complex, removal of the catalyst or catalyst complex from the reaction product and various post-reaction treatments of the oligomerisation product. The oligomerisation product is generally named poly-a-olefin (PAO) and can be categorised based on the viscosity as measured in cSt of the product in the typical range of 2 to 100 cSt. The viscosities of typical low viscosity PAO products are 2, 4, 6 or 8 cSt. In the oligomerisation of a-olefins dimers, trimers, tetramers, pentamers etc. are formed. Heavier products, i.e. having a higher number of monomer units in the oligomer product, naturally have a higher viscosity compared to lighter products. PAO products are used in various applications and depending on the use, various viscosity and other properties are required of the PAO product. Different oligomers can also be mixed to form products with desired properties. Publication US4,434,309 describes oligomerisation of low molecular weight alpha olefins to produce synthetic lubricant base stock. The oligomerisation is performed in the presence of a catalyst, which can be boron trifluoride and a protonic promoter. One key aspect of the production process is the separation of the catalyst or catalyst complex from the oligomerisation product. Publication EP1694439 describes a typical PAO production process and separation of a catalyst complex containing boron trifluoride (BF3) and alcohol from the oligomerisation product with distillation under reduced pressure. The produced oligomerisation product typically needs to be hydrogenated in order to saturate any double bonds still present in the poly-a-olefin (PAO). A typical process sequence to hydrogenate an unsaturated product is that the product intermediate is hydrogenated directly after the process reaction section and the hydrogenation is followed by at least one separation step to obtain the desired saturated product fractions. Alternatively, the product is first separated to various product streams with desired properties, which product streams are then subsequently hydrogenated. However, this process sequence requires intermediate storage capacities and campaign wise batch hydrogenation. There is still a need to develop optimal process sequences in PAO production to enable high quality products with sufficient and economical equipment and process set-ups, with high plant capacity and low downtime. BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is thus to provide a robust process for obtaining poly-a-olefins, with optimal product fractionation and hydrogenation steps. The objects of the invention are achieved by a process characterised by what is stated in the independent claim. The preferred embodiments of the invention are disclosed in the dependent claims. The invention thus provides a process for producing poly-a-olefins, the process comprising a) providing at least one a-olefin monomer and a catalyst, b) letting the at least one a-olefin monomer react in the presence of the catalyst to form a mixture of poly-a-olefins (PAO), c) fractionating the obtained mixture of poly-a-olefins to two PAO fractions, wherein the two PAO fractions are a first fraction of PAO having a kinematic viscosity of 5 cSt or lower and a second fraction of PAO having a kinematic viscosity of more than 5 cSt; and optionally a recycle fraction, of which at least a part is recycled back to the reaction step, and the recycle fraction comprises dimers of the a-olefins, d) subjecting the obtained two PAO fractions to separate hydrogenation to obtain hydrogenated PAO fractions, and e) optionally further fractionating at least one of the hydrogenated PAO fractions to obtain hydrogenated PAO sub-fractions. An advantage of the current invention is that it provides a process for producing poly-a-olefins with an optimal process and equipment set-up. In one embodiment the presented process provides possibilities to run the oligomerisation and hydrogenation steps continuously with little or no intermediate storage of non-hydrogenated products. BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described in greater detail by means of preferred