SELECTIVE OLIGOMERIZATION OF OLEFINS

Abstract

The invention relates to a catalyst system for oligomerizing olefins over a catalyst comprising nickel, to the use of this catalyst and to a method for dimerizing olefins.

Claims

1. Catalyst system comprising a Ni ion-exchanged zeolite of Linde Type A having a Ni content of 1 to 10 wt % (based on the total mass of the catalyst), characterized in that in addition the cations of potassium, sodium or calcium incorporated in the zeolite are at least partially exchanged with other alkali metal or alkaline earth metal ions, wherein the proportion of alkali metal and/or alkaline earth metal ions introduced is between 0.02 and 8.8 wt %.

2. Catalyst system according to claim 1, characterized in that the Ni ion exchange is effected by liquid ion exchange.

3. Catalyst system according to claim 1, characterized in that the alkali metal or alkaline earth metal ions are selected from lithium and/or magnesium.

4. Catalyst system according to claim 1, characterized in that the exchange with alkali metal and/or alkaline earth metal ions is effected by liquid ion exchange.

5. Method for oligomerizing olefins, wherein the olefins are present in gaseous or supercritical form, wherein a Ni ion-exchanged zeolite of Linde Type A having a Ni content of 1 to 10 wt % (based on the total mass of the catalyst) is used as catalyst and wherein an ISO index of less than 0.8 is achieved at a conversion per pass of >10%.

6. Method according to claim 5, characterized in that the olefins used are C2- to C6-olefins or mixtures thereof.

7. Method according to claim 5, characterized in that the olefin is n-butene.

8. Method for oligomerizing n-butene, comprising the following steps: A) providing a catalyst system according to claim 1, B) oligomerizing n-butene by contacting the catalyst system with an n-butene-containing mixture.

9. Method according to claim 8, characterized in that the oligomerization is conducted at a temperature in the range of 150 to 180 C. and a pressure of 40 to 60 bar.

10. Catalyst system according to claim 2, characterized in that the alkali metal or alkaline earth metal ions are selected from lithium and/or magnesium.

11. Catalyst system according to claim 10, characterized in that the exchange with alkali metal and/or alkaline earth metal ions is effected by liquid ion exchange.

12. Catalyst system according to claim 2, characterized in that the exchange with alkali metal and/or alkaline earth metal ions is effected by liquid ion exchange.

13. Catalyst system according to claim 3, characterized in that the exchange with alkali metal and/or alkaline earth metal ions is effected by liquid ion exchange.

14. Method according to claim 6, characterized in that the olefin is n-butene.

Description

EXAMPLES

Catalyst Synthesis:

[0043] Zeolite of Linde Type A (LTA) in the sodium or calcium form (Sigma Aldrich) was pre-calcined at 500 C. for 4 h (heating rate: 5 C./min, in an air stream at 100 ml/min air) and was used either directly exchanged with nickel ions (Ni on Na-LTA and Ni on Ca-LTA) or was exchanged with other co-cations prior to nickel exchange. For this exchange, the zeolite was mixed four times with a 0.5M aqueous solution of LiCl or MgCl.sub.2; (20 g/g zeolite) and stirred at 80 C. for 4 h each time. After each exchange step, the liquid was removed by centrifugation and a fresh solution was added. After the last exchange step, the zeolite was washed with deionized water (2 l), dried overnight and calcined (8 hours at 500 C., heating rate: 5 C./min, in an air stream at 100 ml/min air).

[0044] For the nickel exchange, the LTA precursor was mixed with an aqueous solution of nickel nitrate at concentrations of 0.01 to 0.1 M (20 g/g catalyst) and stirred at 80 C. for 24 h. Subsequently, the catalyst precursor was washed with water (2 l), dried and calcined (8 h at 500 C., heating rate: 5 C./min, in an air stream at 100 ml/min air).

Reaction Process:

[0045] Prior to charging in the reactor, the catalyst was dried at 100 C. for at least 1 h. Then, between 10 and 200 mg of the catalyst were diluted with silicon carbide (SiC) in order to achieve a total weight of 800 mg. This mixture was installed in the middle of a 30 cm long tubular reactor having an internal diameter of 0.152 inches. SiC was used to fix the catalyst bed. The catalyst was activated in a flow of air (100 ml/min) at 450 C. for 2 h (heating rate: 10 C./min. After purging with N.sub.2, the mixture was pressurized with N.sub.2 and then the reactant mixture (85% 1-butene, 15% isobutane) was added via a syringe pump (ISCO SYRINGE PUMP 500 D; including cooling unit to maintain 14 C.). The desired flow rate was set (0.03-0.2 ml/min) and heating was initiated. The products which were formed in the straight pass through the catalyst bed were analyzed by online GC. Prior to GC injection, 100 ml/min H.sub.2 were added in order to hydrogenate the product stream at ambient pressure by means of a Pt/Al.sub.2O.sub.3 catalyst.

Results:

[0046]

TABLE-US-00001 6 wt % Ni on Na-LTA Space- time C.sub.8 Selectivity/% Oligomer WHSV/ yield/ Methyl ISO Selectivity/% Conversion/% g * g.sup.1 * h.sup.1 g * g.sup.1 * h.sup.1 Dimethylhexene heptene Octene index C8 C12 C16 12.8 4.3 0.6 3.0 46.1 50.8 0.52 89.5 10.5 0.0 10.5 6.4 0.7 0.0 45.5 54.5 0.46 100.0 0.0 0.0 6.4 12.8 0.8 0.0 40.9 59.1 0.41 100.0 0.0 0.0 1.9 25.5 0.5 0.0 37.0 63.0 0.37 100.0 0.0 0.0

TABLE-US-00002 6 wt % Ni on LiNa-LTA Space- time Oligomer yield/ Methyl ISO Selectivity/% Conversion/% WHSV/h.sup.1 g * g.sup.1 * h.sup.1 Dimethylhexene heptene Octene index C8 C12 C16 10.5 4.3 0.5 1.8 41.7 56.5 0.45 86.0 14.0 0.0 6.4 6.4 0.4 1.6 39.2 59.2 0.42 87.6 12.4 0.0 4.3 12.8 0.6 0.0 39.0 61.0 0.39 89.2 10.8 0.0

TABLE-US-00003 6 wt % Ni on MgNa-LTA Space- time Oligomer yield/ Methyl ISO Selectivity/% Conversion/% WHSV/h.sup.1 g * g.sup.1 * h.sup.1 Dimethylhexene heptene Octene index C8 C12 C16 20.0 12.8 2.6 4.7 50.9 44.4 0.60 88.3 11.7 0.0 16.3 25.8 4.2 4.1 47.5 48.5 0.56 88.8 11.2 0.0

TABLE-US-00004 6 wt % Ni on Ca-LTA Space- time Oligomer yield/ Methyl ISO Selectivity/% Conversion/% WHSV/h.sup.1 g * g.sup.1 * h.sup.1 Dimethylhexene heptene Octene index C8 C12 C16 34.5 6.4 2.2 4.9 54.8 40.2 0.65 84.0 16.0 0.0 28.6 12.8 3.7 4.4 52.0 43.6 0.61 85.1 14.9 0.0 24.0 25.5 6.1 3.3 47.0 49.7 0.54 82.9 15.1 2.0 19.0 38.1 7.2 2.4 44.2 53.4 0.49 87.8 12.2 0.0 12.8 101.5 13.0 2.4 37.3 47.1 0.48 86.6 13.0 0.4

TABLE-US-00005 6 wt % Ni on LiCa-LTA Space- time Oligomer yield/ Methyl ISO Selectivity/% Conversion/% WHSV/h.sup.1 g * g.sup.1 * h.sup.1 Dimethylhexene heptene Octene index C8 C12 C16 37.3 6.4 2.42 5.5 53.7 40.8 0.65 83.9 16.1 0.0 35.2 12.7 4.8 4.4 49.9 45.8 0.59 83.6 16.4 0.0 32.9 25.6 8.4 5.1 50.3 44.6 0.61 82.2 15.7 2.2 20.4 102.4 20.9 3.6 45.4 51.0 0.53 88.0 11.1 0.9

TABLE-US-00006 6 wt % Ni on MgCa-LTA Space- time Oligomer yield/ Methyl ISO Selectivity/% Conversion/% WHSV/h.sup.1 g * g.sup.1 * h.sup.1 Dimethylhexene heptene Octene index C8 C12 C16 24.8 25.6 6.3 8.3 54.8 36.9 0.71 89.6 10.4 0.0 22.8 50.7 11.6 7.7 53.1 39.2 0.69 89.4 10.6 0.0

[0047] In summary, the present results show that Ni ion-exchanged zeolites of Linde Type A are highly active in butene dimerization and have high selectivity for linear and mono-branched dimers. Both the activity and selectivity can be adapted by the amount and type of the co-cations. Here, this should always be based on the specific product performance (also space-time yield), i.e. an overall consideration of how much product is formed per unit space and time. High selectivities at low WHSV and/or low conversions are therefore not better from an economic point of view, since less product is formed per unit time than in a comparable reaction with lower selectivity at higher WHSV and/or higher conversion. In particular, the inventive zeolites of Linde Type A exchanged with other alkali metal or alkaline earth metal ions exhibit a particularly good combination of high selectivites (high Iso indices) at the same time with high space-time yields.

[0048] This application of a specific zeolite for highly selective olefin oligomerization is not currently known to those skilled in the art.