AU5700994A - A method to oligomerize c4 olefins together with linear alpha olefins - Google Patents

Description

A method to oligomerize C₄ olefins together with linear alp olefins

The invention concerns a process in accordance with the preamble of claim 1 for producing synthetic oils.

According to a process of the present kind, olefinic hydrocarbons are polymerized in order to prepare oily products whose number average molecular weights typically l in the range from 300 to 1200.

The invention also relates to copolymers in accordance with the preamble of claim 17 useful as synthetic oils. A proces for preparing such copolymers is also disclosed.

In the petrochemical industry, a mixture of hydrocarbons known as Raffinate II remains after the isolation of 1, 3-butadiene and isobutylene from pyrolytic C₄ fractions. This kind of a mixture emanates, for instance, from the production of polyisobutylene and, in particular, from the production of methyl tert-butyl ether (MTBE) used as an anti-knock in petrols. The Raffinate II contains, besides n-butane and isobutane, large amounts of n-butenes . Thus, a conventional Raffinate composition comprises some 30 to 55 by weight of 1-butene and 15 to 30 % by weight of 2-butenes (i.e. cis- and trans-butene) . In addition there are minor amounts, typically less than about 3 % by weight, of iso¬ butylene and some methanol, for instance less than about 3 by weight, in the Raffinate.

Normally large volumes of the Raffinate II are produced and used in low value applications during processing of polyisobutylene and MTBE. Here it has been suggested in the prior art to use said Raffinate II and similar secondary ra materials for preparing synthetic oils. Thus, EP Published Patent Applications Nos . 0 337 737 and 0 367 386 teach a process for preparing poly(n-butene) oils, which comprises oligomerizing the olefinic C₄ hydrocarbons of the Raffinate II in a reaction carried out in the presence of an initiato such as A1C1₃ or alkylaluminium chlorides, and a coinitiator typically HCl . Because Raffinate II does not contain isobutylene, or contains it in concentrations below 3 % by weight, the produced oils are predominantly the copolymers 1-butene with cis- and trans-2-butenes .

Although poly(n-butene) oils are not yet industrially produced on a large scale, their broad application in practice is expected because they can be produced from an inexpensive secondary raw material, such as Raffinate II.

However, the viscosity of these oils is strongly dependent temperature, which today limits a broader utilization of th poly(n-butene) oils in the field of engine lubricating oils and for similar purposes.

The quality of lubricating oils is usually characterized by the pour point and the viscosity index. The latter reflects the temperature-dependency of the viscosity of the oil. In the case of high-quality synthetic oils intended for use as engine lubricating oils, it is generally required that the value of the viscosity index be about 120 or higher. Such values are obtained with conventional polyolefinic oils produced by oligomerization of higher linear alpha-olefins using Friedel-Crafts catalysts or Ziegler-Natta catalytic systems. These oils are primarily produced by oligomerizatio (i.e. trimerization to pentamerization) of 1-octene or 1- decene, giving oligomers with optimal properties from the point of view of both viscosity index and pour point. In comparison, it should be mentioned that the viscosity index of poly(n-butene) based oils is below 75, which — although too low for engine lubrication — still is sufficient for man other applications.

The industrially produced oils from higher linear olefins belong to the expensive oils on the market and therefore their broader use is limited. Thus, in summary, the conventional synthetic oils are too expensive to be used on a larger scale, whereas the properties of the much more inexpensive poly(n-butene) oils do not meet the standards for engine lubricants.

One aim of the present invention is to eliminate the proble related to the prior art in the field of synthetic lubricating oils and to provide inexpensive new oils with acceptable properties.

Another aim is to provide novel olefinic copolymers which c be used as lubricating oils or as part of synthetic oil compositions.

Still a third aim is to provide processes for preparing the novel oils and copolymers.

It has now unexpectedly been found that 1-butene along with the cis- and trans-2-butenes or their mixtures contained in the Raffinate II can readily be copolymerized with higher linear alpha-olefins in the presence of suitable initiators to provide an oily product with high viscosity index and lo pour point. Thus, the invention is based on the idea of polymerizing higher linear alpha-olefins in hydrocarbon compositions containing essential amounts of olefinic C₄ hydrocarbons, in particular compositions, which are compris of the residues of the pyrolytic C₄ fractions, such as the above-mentioned Raffinate II.

In particular the process in accordance with the invention characterized by what is stated in the characterizing part claim 1.

The copolymers according to the invention are mainly characterized by what is stated in the characterizing part claim 17. The process for preparing copolymer useful as synthetic oil is characterized by what is stated in the characterizing pa of claim 20.

Within the scope of the present application the term "to polymerize" denotes the formation by chemical reactions of large molecules built up by single monomers (or repeating units) irrespective of the number of such monomers in the product. Thus, for the purposes of this application "polymerizing" also includes "oligomerizing" , i.e. formatio of large molecules containing 2 to 10 monomers.

According to one preferred embodiment, synthetic oils are prepared by polymerizing higher linear alpha-olefines (LAO) in hydrocarbon compositions containing some 15 to 80 % by weight of 1-butene, 5 to 50 % by weight of 2-butenes, and about 10 % by weight or less of isobutylene. Preferably, th olefinic hydrocarbon compositions contain about 25 to 70 % weight, in particular 30 to 60 % by weight of 1-butene and to 40 % by weight, in particular 15 to 30 % by weight of 2- butenes. In addition to these components the composition ma contain minor amounts of, for instance, n-butane, isobutane, propane and other alkanes, isobutylene, methyl tert-butyl ether and other etherification products, as well as various other lower olefinic oligomers.

In particular, the olefinic hydrocarbon compositions compris mixtures of hydrocarbons remaining in a pyrolytic C₄ fractio after isolation of 1, 3-butadiene and isobutylene. These kin of hydrocarbon mixtures may consist of Raffinate II which is obtained from the production of methyl tert-butyl ether or from the selective polymerization of isobutylene.

To the C₄ hydrocarbon compositions there are added 1 to 99 % by weight, preferably 5 to 90 % by weight and in particular

10 to 70 % by weight of higher LAO's. The amount of the add LAO's is calculated on basis of the total amount of olefins in the composition after the addition. The added LAO's are selected from the group comprising higher alpha-olefins containing 6 to 24 carbon atoms, preferably the LAO's may b selected from the group comprising higher linear alpha- olefins containing 6 to 18 carbon atoms, and in particular the LAO's are selected from the group comprising higher linear alpha-olefins containing 8 to 16 carbon atoms. Exemplifying LAO species are 1-octene, 1-decene, 1-dodecene 1-tetradecene and 1-hexadecene.

The molecular weights of the produced copolymers depend on the composition of the initial mixture, on the polymerizati temperature, and to some extent on the initiator system use Typically, the number average molecular weight, M_n, ranges from 300 to 1200, preferably from about 350 to about 1000.

The polymerization is preferably carried out at -10 °C to +70 °C. Without altering the composition of the reaction mixture, the number average molecular weight of the copolymers can be varied in the range from 300 to 1000 by changing the temperature of the polymerization.

The initiator systems used for the polymerization are simil to those previously employed for preparing poly(n-butenes) . Reference is made, in particular, to the above-mentioned European Published Patent Applications Nos. 0 337 737 and

0 367 386, the disclosures of which are herewith incorporated by reference.

Thus, the initiator system may be based on A1C1₃. However, the copolymerization does not proceed solely with A1C1₃ and, according to one preferred embodiment, A1C1₃ is therefore added in an ethyl chloride solution or as a liquid complex formed from AlCl₃, toluene or an equivalent aromatic solvent and hydrogen chloride. The advantage of these forms of A1C1₃ consists in easy dosing of the initiator into the reaction system and also in the fact that A1C1₃ does not need any additional coinitiator if added in this form. Since the aluminium trichloride liquid complex is not soluble in Raffinate II, vigorous stirring of the reaction medium is required to avoid deposition of the catalyst system on the bottom of the reaction vessel.

According to another preferred embodiment, an alkylaluminiu chloride of the general formulas R₂A1C1 or RA1C1₂ is employe as an initiator and an anhydrous hydrogen halide as a poly- merization coinitiator. In the above general formulas R stands for a lower alkyl having 1 to 6 carbon atoms . Preferably alkylaluminium dichloride compounds of the gener formula RA1C1₂ are used and, in particular, the compounds a selected from the group comprising methylaluminium dichloride, ethylaluminium dichloride, propylaluminium dichloride and butylaluminium dichloride. The hydrogen halides may comprise hydrogen chloride or hydrogen fluoride hydrogen chloride being preferred.

Gradual addition of the initiator into the reaction mixture will assist in governing the rate of copolymerization by providing practically isothermal reaction control of the strongly exothermic copolymerization. In this way it is possible to ensure that a product of even quality will be obtained.

In the case of an initiator system comprising an initiator and a coinitiator, it is preferred to add the coinitiator a the beginning of polymerization. If anhydrous hydrogen chloride is used, the total amount of initially added coinitiator ranges from 0.1 % by weight to 0.3 % by weight. The coinitiator can be added dissolved in the reaction mixture. Alkylaluminium dichloride can be then added in sma portions, preferably in an inert solvent, and thus an almos isothermal course of polymerization can be secured at the required temperature. At an inverse addition order of components, there is a danger that the exothermal reaction cannot be controlled and proceeds extremely fast. In such a case, an undesirable overheating of the reaction mixture ma take place.

The initiator and the coinitiator are consumed by the polymerization reaction. At polymerization temperatures bel -10 °C, the relative consumption of the initiator increases and high conversions are hardly attained. Therefore, as mentioned above, the reaction is preferably carried out at temperatures above -10 °C. Typically, the initiator consumption (calculated on basis of the obtained product) amounts to 0.3 - 0.7 % by weight at temperatures in the preferred range from -10 °C to +70 °C at olefin conversion rates in excess of 90 %.

According to one particularly preferred embodiment of the invention, to an olefinic hydrocarbon composition, which contains n-butenes in a total concentration of at least 30 % by weight, there are added alpha-olefins containing 6 to 18 carbon atoms in the molecule. The alpha-olefins are reacted with the butenes of the hydrocarbon composition in the presence of an initiator system comprising a solution of A1C1₃ in ethyl chloride or a liquid complex formed from A1C1 toluene and HC1 to provide oils with viscosity indeces from 100 to 150 and pour points from +5 °C to -65 °C, the molar ratio of alpha-olefins to n-butenes being in the range from 1:1 to 1:5.

According to another particularly preferred embodiment of t invention, to an olefinic hydrocarbon composition, which contains n-butenes in a total concentration of at least 30 % by weight, there are added alpha-olefins containing 8 to 16 carbon atoms in the molecule. The alpha-olefins are reacted with the butenes of the hydrocarbon composition in the presence of an initiator system comprising an alkylalumium dichloride together with hydrogen chloride to provide an oi with viscosity index from 100 to 140 and pour points from 0 °C to -65 °C, the molar ratio of alpha-olefins to n-butene being in the range from 1:1 to 1:5.

The copolymers according to the invention essentially consis of repeating units of n-butene, cis- and trans-2-butenes and higher linear alpha-olefins with 6 to 18 carbon atoms. The polydispersity of these copolymers defined as the ratio M_w/M is lower than 1.4.

As mentioned above, the invention also concerns a process fo producing a copolymer product useful as a synthetic oil or part thereof . The process may be summarized as comprising th steps of

- mixing higher linear alpha-olefins having 6 to 18 carbon atoms with a C₄ hydrocarbon composition derived from the production of methyl tert-butyl ether or from the selective polymerization of isobutylene and containing at least 15 % by weight of 1-butene and at least 5 % by weight of 2-butenes to form a reaction mixture,

- adding an initiator system to the reaction mixture,

- keeping the temperature of the reaction mixture in the range from -10 °C to +70 °C,

- allowing the higher linear alpha-olefins to react with the 1-butenes and 2-butenes to form a reaction product and

- separating volatile components and any initiator syste residues to form a oily product consisting essentially of copolymers having a number average molecular weight in the range from 300 to 1200.

The oily products of the invention are characterized by having higher viscosity index than have the poly (n-butene) oils as such. Also the pour point is improved by the copolymerization of n-butenes with higher linear alpha-

-olefins. The pour point of the present oils is lower than that of poly(n-butene) oils and it is, in fact, even lower that the pour points of oligomers of higher linear alpha- -olefins of comparable molecular weights.

According to a preferred embodiment of the present invention the hydrocarbon composition should contain only trace amounts, if any, of methanol, since the methanol may interfere with the polymerization reaction by consuming the initiator and causing inhibition of the polymerization. Therefore, if Raffinate II obtained from the production of methyl tert-butyl ether is used, which sometime may contain up to a couple of per cent per weight of methanol, the residual methanol is removed or its concentration lowered to below 3000 ppm before the polymerization reaction.

The viscosity index of the copolymerisate depends on the content and the kind of the higher linear alpha-olefins used and tends to increase with increasing content and length of the linear alpha-olefin. Pour point of the obtained copolyme also depends on the higher linear alpha-olefin used and increases with increasing length of the copolymer molecule and with increasing molar content of n-butenes .

After polymerization, the reaction mixture is processed by methods known per se . According to a preferred embodiment, i is washed, in particular, with an about 5 % aqueous solution of soda and then with water. Alternatively, sorption clay is added to the mixture in an amount of approx. 0,5 to 10 %, in particular about 2 %, calculated on basis of the initial content of olefins, to remove the catalyst. The low-boiling portions are distilled off by heating to at least 140 °C at 13 Pa. A colourless or slightly yellowish oil is obtained with a kinematic viscosity in the range from 4 to 15 cSt at +100 °C and in the range from 27 to 160 cSt at +40 °C. The obtained copolymers are characterized by a relatively narrow distribution of molecular weight corresponding to a polydispersity defined as the ratio M_w/M_n lower than 1.4. The invention provides considerable benefits. A particularl important advantage of the present process resides in the fact that the copolymerization of n-butenes can be carried out in Raffinate II, which is a cheap secondary raw materia normally discarded, without having to isolate and purify th n-butenes .

A further advantage of the invention consists in producing high quality synthetic oils with viscosity indeces on the same level as those of expensive synthetic oils prepared fr pure higher linear alpha-olefins.

The oils produced by copolymerization of n-butenes with higher linear alpha-olefins according to this invention can be used for a number of different applications. In particular, because of their very convenient values of viscosity index and pour point, they can be employed as hig quality engine lubricating oils in applications where the viscosity changes with temperature should be as small as possible. The low polydispersity of their molecular weights is important as it indicates that the oil viscosity will not change too much during long-term mechanical stress. The obtained properties are similar to these of multigrade oils with long-term service lives.

Another important feature of the present oils consists in th fact that they do not release any carbonization residue afte heating to high temperature or combustion. This is why their expected use is as lubricating oils for two-stroke combustio engines, as oils useful in metallurgy for rolling and drawin of metallic materials, as oils for transformers, electrical insulations and cables, as oils for energy transfer in cooling and heating systems, and as oils for many other similar applications. The oils are non-toxic and can be utilized as additives in plastics and rubbers.

In the following, the invention will be further examined in detail with the aid of working examples illustrating the copolymerization of n-butenes with higher linear alpha- olefins in a Raffinate II. It should, however, be understoo that the scope of the invention is not limited to these examples. In particular it should be noted that other hydrocarbon compositions containing essential amounts of olefinic C₄ hydrocarbons can be used for the purposes of the present invention.

Equipment and materials

The copolymerizations were carried out in a glass reactor with a volume of 150 ml or, alternatively, in a stainless steel reactor with a volume of 1000 ml. Both reactors were equipped with a magnetic stirrer, valve for charging and dosing the initiator and with outside cooling. The temperature of the reaction mixture was monitored with a thermocouple connected to a recorder. The polymerization course was controlled by gradual dosing of the initiator so as to keep the temperature of the reaction mixture in the region of +3 °C around the required temperature.

For the purpose of preparing the oils, a hydrocarbon composition (Raffinate II) comprising the residue of a C₄ fraction from the production of MTBE was used. It was washed three times with water in order to remove methanol and dried in the liquid state over KOH in a pressure vessel .

The hydrocarbon composition refined in this way had the following composition: 49.2 % 1-butene, 15.1 % trans- -2-butene, 9.7 % cis-2-butene, 2.2 % isobutylene, 15.6 % n-butane, 7.2 % isobutane and 0.6 % propane. The methanol content was always less than 3000 ppm and the content of methyl tert-butyl ether was less than 0.2 %. The linear alpha-olefins were of commercial purity and contained more than 99 % by weight 1-olefin. Molecular weights M_n and M_w and polydispersity M_w/M_n of the products were evaluated by GPC and VPO.

Example 1

Copolymerization of n-butenes was carried out in a mixture o hydrocarbons known as Raffinate II which had been separated from the C₄ fraction in the production of MTBE . To this mixture 30 mol % of 1-decene was added, the amount of 1 decene added being calculated on basis of amounts of olefins in the new mixture formed. The copolymerization was performe at a mean temperature of +20 °C by gradual addition of small amounts of a 10 % A1C1₃ solution in ethyl chloride in such a way that the reaction mixture was not overheated by more tha 3 °C. The polymerization was stopped after 40 min by additio of alcohol, the reaction mixture was washed with a 5 % solution of soda and then with water. The hydrocarbon layer was separated, mixed with filtration clay and filtered under pressure. Volatile fraction was removed by heating the reaction mixture up to 120 °C at 13 Pa. The colourless oil obtained had a number average molecular weight M_n = 810 and viscosity index of 107. The consumption of A1C1₃ related to the final product was 0.6 % by weight at an olefin conversio rate of 97 % by weight

Example 2

Copolymerization of n-butenes with 1-dodecene was carried ou in Raffinate II in an analogous way as in Example 1. The copolymer prepared with 30 mol . % 1-dodecene at polymerizatio temperature +20 °C had a molecular weight M_n of 850, a viscosity index of 122 and a pour point of -43 °C. The consumption of AlCl₃ was 0.7 % by weight at a conversion rat of 95 % . Example 3

Copolymerization of n-butenes present in Raffinate II was carried out with the addition of 30 mol . % 1-tetradecene analogously as in Example 1. The molecular weight M_n of the oil obtained at a polymerization temperature of +20 °C was 810, whereas the polydispersity M_w/M_n was 1.3 and the viscosity index was 141.

Example 4

Copolymerization of n-butenes was carried out in the residue of a C₄ fraction (Raffinate II) with the addition of 30 mol . % 1-hexadecene (the added amount related to the total amount o olefins in the same way as in Example 1) . The copolymerization was conducted at +20 °C, the conversion rate, as calculated on basis of the olefins present in the mixture, being 92 %. The prepared oil had a number average molecular weight M_n of 910, a polydispersity M_w/M_n of 1.1, a viscosity index of 148 and a pour point of -3 °C. The consumption of A1C1₃ was 0.65 % by weight at a 92 % conversion rate.

Example 5

Copolymerization of n-butenes present in the residue of a C₄ fraction was carried out with the addition of 30 % by weight of 1-hexadecene at +20 °C under initiation with a liquid complex of A1C1₃, toluene and anhydrous HC1. The liquid complex was prepared by introducing gaseous HC1 into a suspension of 5.0 g A1C1₃ in 6.0 ml toluene at 0 °C until all A1C1₃ was transferred into the solution. A conversion rate of 94 % was attained by gradual dosing of the initiator into th reaction mixture for 30 min.

The obtained oil had a molecular weight M_n of 700, a poly¬ dispersity M^ M,, of 1.31, a viscosity index of 130 and a pour point of -15 °C. The consumption of AlCl₃ related to the product was 0.6 % by weight.

Example 6

Copolymerization of n-butenes was carried out in the residu of a C₄ fraction with 50 % by weight of 1-decene at +70 °C under initiation with a liquid A1C1₃ complex prepared according to Example 5. The polymerization was stopped afte 30 min by addition of alcohol at a 93.5 % conversion rate.

The oily product had a molecular weight M_n = 560, a viscosit index of 117 and a pour point of -38 °C.

Example 7

Copolymerization of n-butenes was carried out in Raffinate by the addition of 30 % by weight of 1-dodecene related to the total content of olefins in the resulting mixture using liquid A1C1₃ complex prepared according to the disclosure of Example 5 as an initiator. The copolymerization proceeded at -10 °C during 50 min under gradual dosing of the initiator to a conversion rate of 85 % related to the total content of olefins . The obtained copolymer had a molecular weight M_n of 860, a viscosity index of 105 and a pour point of -31 °C. T consumption of A1C1₃ related to the product was 0.83 % by weight.

Example 8

Copolymerization of n-butene in Raffinate II was carried out with linear alpha-olefins C₆ to C₁₆ added into the reaction mixture in an amount of 37 % by weight related to the total amount of olefins in the new resulting mixture. The poly¬ merizations were carried out at +20 °C under initiation with an A1C1₃ solution in ethyl chloride. The consumption of A1C1₃ related to the product ranged from 0.45 to 0.75 % by weight. The results are given in Table I . Table 1 Characteristics of copolymers of n-butenes in

Raffinate II with various 1-olefins (about 37 % b weight 1-olefin, 20 °C)

Polymerization conditions : initiator - aluminium chloride in ethyl chloride, polymerization temperature +20 °C

The content of 1-olefins (C₄-C₁₆) relates to the olefins present in the Raffinate II only

Example 9

Copolymerization of n-butenes was carried out in a mixture o C₄ hydrocarbons (Raffinate II) obtained from the production of MTBE. To this mixture 37 % by weight of 1-decene was added, the added amount being calculated on basis of the total amount of olefins in the new mixture formed. Before th polymerization, 0.3 % by weight of gaseous hydrogen chloride was introduced into the reaction mixture. The copolymerization was performed at a mean temperature of +20 °C by gradual addition of small amounts of a 10-% EtAlCl₂ solution in heptane in such a way that the reaction mixture was not overheated by more than 3 °C. The polymerization was stopped after 40 min by adding alcohol, the reaction mixture was washed with a 5 % solution of soda and then with water. The hydrocarbon layer was separated, mixed with filtration clay and filtered under pressure. Volatile fraction was removed by heating the reaction mixture up to 120 °C at 13 Pa. The colour-less oil obtained had a number average molecular weight M_n of 640 and a viscosity index of 97. The consumption of EtAlCl₂ related to the final product was 0.5 by weight at a 92 % conversion rate of the olefins.

Example 10

Copolymerization of n-butenes with 1-dodecene was carried ou in Raffinate II in an analogous way as in Example 9. The copolymer prepared with 37 % by weight of 1-dodecene at a polymerisation temperature of +20 °C had a molecular weight M_n of 111 and a pour point of -38 °C. The consumption of EtAlCl₂ was 0.7 % by weight at a conversion rate of 93 %.

Example 11

Copolymerization of n-butenes present in Raffinate II was carried out with the addition of 37 % by weight of 1-tetradecene analogously as in Example 9. The oil obtained at a polymerization temperature of +20 °C had a molecular weight ^"M_π of 630, a polydispersity M_w/M_n of 1.2, a viscosity index of 109 and a pour point of -33 °C.

Example 12

Copolymerization of n-butenes was carried out in a residue o a C₄ fraction (Raffinate II) with the addition of 37 % by weight of 1-hexadecene related to the total amount of olefin in the same way as in Example 9 at +20 °C. The prepared oil had a number average molecular weight M^" _w of 820, a poly¬ dispersity M_w/M_n of 1.25, a viscosity index of 110 and pour point of -16°C. The consumption of EtAlCl₂ was 0.65 % by weight at a conversion rate of 91 %. Anhydrous hydrogen chloride was added at the beginning into the initial reactio mixture in the amount of 0.25 % by weight.

Example 13

Copolymerization of n-butenes present in a residue of a C₄ fraction was carried out with the addition of 13 % by weight of 1-hexadecene at +20 °C under initiation with anhydrous HC and EtAlCl₂. A 89 % conversion rated was attained by gradual dosing of the initiator into the reaction mixture for 30 min The obtained oil had a molecular weight M_n of 680, a polydispersity ,/ _n of 1.15, a viscosity index of 83 and a pour point of -45 °C. The consumption of EtAlCl₂ related to the product was 0.6 % by weight.

Example 14

Copolymerization of n-butenes was carried out in a C₄ fraction residue with 50 % by weight of 1-decene at +70 °C under initiation with HCl and EtAlCl₂ . The polymerization was stopped after 30 min by the addition of alcohol at a conversion rate of 93.5 % by weight. The oily product had a molecular weight M_n of 560, a viscosity index of 119 and a pour point of -63 °C.

Example 15

Copolymerization of n-butenes was carried out in Raffinate I with the addition of 30 % by weight of 1-octene related to the total content of olefins in the resulting mixture using EtAlCl₂ as an initiator. The copolymerization proceeded at -10 °C during 50 min under gradual dosing of the initiator u to a conversion of 85 % by weight related to the total content of olefins. The obtained copolymer had a molecular weight M_n of 860, a viscosity index of 105 and a pour point of -21 °C. The consumption of EtAlCl, related to the product was 0.83 % by weight. Anhydrous hydrogen chloride' was added at the beginning into the reaction mixture in an amount of 0.35 % by weight.

Example 16

Copolymerization of n-butene in Raffinate II was carried out by adding linear alpha-olefins C₆ to C₁₆ into the reaction mixture in an amount of 37 % by weight related to the total olefins in the new resulting mixture. The polymerizations were carried out at +40 °C under initiation with a solution of EtAlCl₂ and HCl as coinitiator. The consumption of EtAlCl₂ related to the product ranged from 0.40 to 0.70 % by weight. The results are given in Table 2.

Example 17

Copolymerization of n-butenes present in Raffinate II was carried out with the addition of 10 % by weight of 1-octene and 10 % by weight of 1-decene at +20 °C under initiation with anhydrous HCl and methyl aluminium dichloride MeAlCl₂.

The polymerization was stopped at a coversion rate of 93 % b weight. The consumption of MeAlCl₂ related to the product wa 0.65 % by weight, the number average molecular weight (M_n) o the oily product was 610, the viscosity index 95 and the pou point -55 °C.

Example 18

Copolymerization of a n-butenes mixture in the Raffinate II was carried out with 50 % by weight of 1-decene under initiation with HCl and butyl aluminium dichloride BuAlCl₂ a +50 °C.

The isolated polymer had a molecular weight M_n of 550, a viscosity index of 108 and a pour point of -51 °C. The consumption of BuAlCl₂ was 10.73 % by weight at a conversion rate of olefins of 92 % by weight.

Table 2 Characteristics of copolymers of n-butenes in

Raffinate II with various 1-olefins (about 37 % by weight 1-olefin, 40 °C)

Polymerization conditions initiator system: ethyl- aluminium dichloride, polymerization temperature +40 °C

^aContent of 1-olefins (C₄-C₁₆) relates to the olefins present in the Raffinate II only

Claims (21)

Claims

1. A process for producing synthetic oils, wherein olefinic hydrocarbons are polymerized to form an oily produ having a high viscosity index and a low pour point, c h a r a c t e r i z e d by

- reacting higher linear alpha-olefins containing 6 to 2 carbon atoms with a hydrocarbon composition containin essential amounts of 1-butene and 2-butenes in the presence of an initiator system to produce a copolyme containing reaction mixture, and

- separating the copolymer from the reaction mixture.

2. The process according to claim 1, wherein the higher linear alpha-olefins are reacted with a hydrocarbon composition containing 15 to 80 % by weight of 1-butene, 5 t 50 % by weight of 2-butenes, and about 10 % by weight or les of isobutylene.

3. The process according to claim 2, wherein the higher linear alpha-olefins are reacted with a hydrocarbon composit ion containing about 25 to 70 % by weight, in particular 30 to 60 % by weight of 1-butene and 10 to 40 % by weight, in particular 15 to 30 % by weight of 2-butenes.

4. The process according to any one of claims 1 to 3 , wherein the hydrocarbon composition comprises the residue of a C₄ fraction remaining after the separation of essentially all of the 1, 3-butadiene and isobutylene compounds.

5. The process according to claim 4 , wherein the hydrocarbo composition comprises a mixture of hydrocarbons known as Raffinate II obtained from a process for preparing a product selected from the group comprising methyl tert-butyl ether and poly(isobutylene) .

6. The process according to any one of claims 1 to 5, wherein 1 to 99 % by weight, preferably 5 to 90 % by weight and in particular 10 to 70 % by weight of higher .linear alpha-olefins are added to the hydrocarbon composition and reacted with the 1-butene and 2-butenes fraction thereof, t amount of the added linear alpha-olefins being calculated o basis of the total amount of olefins in the composition aft the addition.

7. The process according to any of the previous claims, wherein the higher linear alpha-olefins are selected from t group comprising higher alpha-olefins containing 6 to 18 carbon atoms .

8. The process according to claim 7, wherein the higher linear alpha-olefins are selected from the group comprising 1-octene, 1-decene, 1-dodecene, 1-tetradecene and 1- hexadecene.

9. The process according to any of the previous claims, wherein the initiator system is selected from the group comprising A1C1₃ together with HCl, AlCl₃ in an ethyl chlorid solution; a liquid complex formed from A1C1₃, an aromatic solvent and hydrogen chloride; and an alkylaluminium chlorid of the general formulas R₂A1C1 or RA1C1₂, wherein R stands fo a lower alkyl having 1 to 6 carbon atoms, together with an anhydrous hydrogen halide.

10. The process according to claim 9, wherein the initiator system is added gradually during the reaction.

11. The process according to claim 9, wherein the initiator system used is selected from the group comprising A1C1₃ in ethyl chloride solution, and a liquid complex formed from A1C1₃, toluene and HCl, the process comprising reacting alpha-olefins having 6 to 18 carbon atoms with a hydrocarbon composition containing at least 30 % by weight of 1-butene a a molar ratio of alpha-olefins to 1-butenes ranging from 1:1 to 1:5 to form oily products with a viscosity index in the range from 100 to 155 and pour points in the range from +5 ° to -65 °C.

12. The process according to claim 11, wherein the number average molecular weight of the oily products lies in the range from 400 to 1000.

13. The process according to claim 9, wherein the initiator system used comprises an alkylaluminium chloride together with anhydrous hydrogen chloride, the process comprising reacting alpha-olefins having 8 to 16 carbon atoms with a hydrocarbon composition containing at least 30 % by weight 1 butene at a molar ratio of alpha-olefins to 1-butenes rangin from 1:1 to 1:5 to form oily products with a viscosity index in the range from 100 to 140 and pour points in the range from 0 °C to -65 °C.

14. The process according to claim 13, wherein the number average molecular weight of the oily products lies in the range from 350 to 900.

15. The process according to any of the previous claims, wherein the methanol content of the hydrocarbon composition is less than 3000 ppm.

16. The process according to any of the previous claims, wherein the higher linear alpha-olefins are reacted with th 1-butene and 2-butenes of the hydrocarbon composition at a temperature in the range from -10 °C to +70 °C.

17. An olefinic copolymer useful as a synthetic oil or as a component of a synthetic oil, comprising repeating units of n-butene, cis- and trans-2-butenes and higher linear alpha- olefins containing 6 to 18 carbon atoms and having a number average molecular weight in the range from 300 to 1200 and a polydispersity defined as the ratio ^"M_w/M_n lower than 1.4.

18. The copolymer according to claim 17, wherein the higher linear alpha-olefin units are comprised of alpha-olefins having 10 to 16 carbon atoms in the molecule.

19. The copolymer according to claim 17 or 18, wherein the molar ratio between the higher linear alpha-olefin units and the n-butene units is in the range from 1:1 to 1:5.

20. A process for producing a copolymer product useful as a synthetic oil or components thereof, comprising the steps of

- mixing higher linear alpha-olefins having 6 to 18 carbon atoms with a spent C₄ hydrocarbon composition derived from the production of methyl tert-butyl ether or from the selective polymerization of isobutylene an containing at least 30 % by weight of 1-butene and at least 5 % by weight of 2-butenes to form a reaction mixture,

- adding an initiator system to the reaction mixture,

- keeping the temperature of the reaction mixture in the range from -10 °C to +70 °C,

- allowing the higher linear alpha-olefins to react with the 1-butene and 2-butenes to form a reaction product, and

- separating volatile components and any initiator syste residues to form a oily product consisting essentially of copolymers having a number average molecular weight in the range from 300 to 1200.

21. The process according to claim 20, wherein the initiator system is gradually added during the reaction between the higher linear alpha-olefins and the 1-butene and 2-butenes.