Process for Heterogeneous Isomerization of alpha-Olefins

Abstract

A method for the isomerization of alpha-olefins to the corresponding internal olefins uses a heterogenous catalyst containing silicon-aluminum mixed oxide in a continuous fixed-bed operation mode.

Claims

1. A method, comprising: reacting. by, isomerization at least one alpha-olefin comprising 10 to 20 carbon atoms with a silicon-aluminum mixed oxide composition as a catalyst, to obtain an internal olefin; wherein the silicon-aluminum mixed oxide composition consists of: 75 to 99.99% by weight of silicon dioxide (calculated as SiO.sub.2); and 0.01 to 25% by weight of aluminum oxide (calculated as Al.sub.2O.sub.3).

2. The method according to claim 1, wherein the silicon-aluminum mixed oxide composition has a BET surface area from 50 to 250 m.sup.2/g.

3. The method according to claim 1, wherein the silicon-aluminum mixed oxide composition consists of: 85 to 99.99% by weight of silicon oxide (calculated as SiO.sub.1); and 0.01 to 15% by weight of aluminum oxide (calculated as Al.sub.2O.sub.3).

4. The method according to claim 1, wherein the silicon-aluminum mixed oxide composition is prepared by flame hydrolysis.

5. The method according to claim 1, wherein the at least one alpha-olefin comprises 14 to 16 carbon atoms, or the at least one alpha-olefin comprises a mixture of alpha-olefins comprising 14 to 16 carbon atoms.

6. The method according to claim 1, wherein the at least one alpha-olefin is an alpha-tetradecene comprising at least 90% by weight of m o-olefinic linear alpha-olefins.

7. The method according to claim 1, wherein the reacting comprises: (a) providing the catalyst in a reaction zone of a reactor; (b) inerting and tempering the reactor to a reaction temperature; (c) continuously feeding the at least one alpha-olefin first through a preheating zone and then through the reaction zone to a reaction mixture, by controlling temperature, pressure and weight hour space velocity (WHSV); (d) optionally, if the reactor is a slurry reactor, removing the catalyst from the reaction mixture at a reaction outlet; (e) cooling the reaction mixture after the reaction zone to a temperature for further processing: and (f) optionally, collecting an isomerized product comprising the internal olefin; and/or (g) optionally, removing undesired by-products.

8. The method according to claim 7, wherein the catalyst consists of shaped bodies prepared by a shaping process from the silicon-aluminum mixed oxide composition, a binder and a temporary assistant.

9. The method according to claim 7, wherein the reaction temperature is in the range of 130 to 340° C.

10. The method according to claim 7, wherein the weight hour space velocity (WHSV) is in the range of 3.0 to 5.5.sup.−1.

11. The method according to claim 1, wherein a conversion rate of the at least one alpha-olefin is 95% or higher.

12. The method according to claim 1, wherein an amount of dimer in the isomerized product is 5 mol% or lower.

13. An isomerized product of at least one alpha-olefin comprising 10 to 20 carbon atoms, or a mixture thereof, prepared by a method comprising: (a) providing a catalyst in a reaction zone of a reactor; (b) inerting and tempering the reactor to a reaction temperature; (c) continuously feeding the at least one alpha-olefin first through a preheating zone and then through the reaction zone to a reaction mixture, top, by controlling temperature, pressure and weight hour space velocity (WHSV); (d) optionally, if the reactor is a slurry reactor, removing the catalyst from the reaction mixture at a reaction outlet; (e) cooling the reaction mixture after the reaction zone to a temperature for further processing; and. (f) optionally, collecting the isomerized product; and/or (g) optionally, removing of undesired by-products.

14. The isomerized product according to claim 13. wherein an amount of dimer is 5 mol % or lower.

15. The method according to claim 2, wherein the silicon-aluminum mixed oxide composition has a BET surface area from 100 to 200 m.sup.2/g.

16. The method according to claim 5, wherein the at least one alpha-olefin comprises 14 carbon atoms.

17. The method according to claim 7, wherein the reactor is a fixed-bed reactor.

18. The method according to claim 7, wherein in (g), the by-products are removed by distillation, rectification, vacuum distillation, or membrane separation.

19. The method according to claim 9, wherein the reaction temperature is in the range of 160 to 190° C.

20. The method according to claim 10, wherein the weight hour space velocity (WHSV) is in the range of 3.5 to 3.7 h.sup.−1.

Description

[0096] FIG. 1: Comparison of the 1-tetradecene conversion in all reactors and experiments. The analytical data were determined by using the .sup.13C-NMR method.

[0097] The invention will be illustrated in detail below by examples and comparative examples without any intention that the concept of the invention be restricted to these particular embodiments.

Experimental Part

[0098] .sup.13C-NMR spectroscopical determinaton of the tetradecene isomer distribution The isomers produced by the isomerization of alpha-tetradecene were determined and quantified using offline .sup.13C-NMR spectroscopy. The determination was carried out on CDCI3 with an addition of chromoacetylacetonate as relaxation aid. The double bond signals were used for the evaluation. Under the chosen conditions, resulting 5-, 6- and 7-tetradecenes could not be differentiated and are therefore given as a lumped value.

[0099] For further validation of the multiplicity of the signals, especially of the methylene and quaternary carbon atoms, .sup.13C-DEPT spectrum was recorded as well.

Preparation of the Silicon-Aluminum Mixed Oxide

[0100] The vapor of a mixture consisting of 45 kg/h of CH.sub.3SiCl.sub.3 and 15 kg/h of SiCl.sub.4 and the vapor of 0.6 kg/h of aluminum chloride were introduced separately from one another by means of nitrogen as carrier gas into a mixing chamber. The vapors were mixed with 14.6 standard m.sup.3/h of hydrogen and 129 standard m.sup.3/h of dried air in the mixing chamber of a burner, fed via a central tube, at the end of which the reaction mixture is ignited, into a water-cooled flame tube and burnt there. The powder formed was subsequently deposited in a filter and treated with water vapor at 400 to 700° C. The powder contained 99% by weight of silicon dioxide and 1% by weight of aluminum oxide. The BET surface area was 173 m.sup.2/g. The DBP number was 326 g/100 g of mixed oxide.

[0101] To determine the weight ratio (Al.sub.2O.sub.3/SiO.sub.2).sub.surface of the primary particles in a surface layer having a thickness of about 5 nm, XPS analysis was employed. This resulted in a weight ratio (Al.sub.2O.sub.3/SiO.sub.2).sub.surface of 0.0042. The determination of the weight ratio (Al.sub.2O.sub.3/SiO.sub.2).sub.ttl in the total primary particle was carried out by X-ray fluorescence analysis on the powder. It showed a weight ratio (Al.sub.2O.sub.3/SiO.sub.2).sub.ttl of 0.010. This resulted in a value for (Al.sub.2O.sub.3/SiO.sub.2).sub.ttl (Al.sub.2O.sub.3/SiO.sub.2).sub.surface of 2.4.

Isomerization Reaction in Batch Mode

[0102] For each experiment, an electrically heated steel autoclave equipped with an internal stirrer was filled with 20 g of 1-tetradecene (feed) and 1 g of catalyst. After closing the reactor, the gas phase in the reactor was exchanged by feeding nitrogen and the pressure was adjusted to about 5 bar. subsequently, the heating of the reactor was started, and the reaction mixture stirred until the end of the desired reaction.

[0103] Detailed analysis of the experiments in batch mode was made by .sup.13C-NMR spectroscopic measurements after reaction stop.

Isomerization Reaction in Continuous Fixed-Bed Operation Mode

[0104] The experiments in the continuous operation mode were carried out simultaneously in two setups, each setup consisting of feed vessels, an HPLC-pump, a pre-heating zone, two consecutive tubular fixed-bed reactors located in a heating oven, and a product vessel. Each setup was filled with 6 g of fresh catalyst. The feed consisted of alpha-tetradecene and was pumped via the HPLC pump first through the preheating zone, where the feed liquid is heated to reaction temperature, and then from the bottom to the top through the first and subsequently through the second tubular fixed-bed reactor. This ensured that the reactors were entirely filled with liquid. The reaction mixture was cooled after the reaction zone to ambient temperature and stored in the product tank. The feed tank as well as the product tank were purged with nitrogen.

[0105] Reaction Conditions:

[0106] WHSV value=3.1 to 4.7 h.sup.−1

[0107] maximum catalyst loading=12 g

[0108] feed flow rate=0.8 to 1.2 mL/min

[0109] pressure=atmospheric

[0110] The reaction product of the continuous operation mode was analyzed in regular intervals by .sup.13C-NMR to determine the distribution of the C.sub.14-olefins. The consistency of the analyses was ensured by double measurement of the same sample.

[0111] 1-Tetradecene Purity

[0112] Before starting the experiments, the 1-tetradecenes used as feed were analyzed to determine the initial concentration distributions. Results are shown in Table 1. The term “tetradecane” is abbreviated throughout the tables as “TD”.

TABLE-US-00001 TABLE 1 Initial composition of 1-tetradecenes used. 2-ethyl-1- 2-propy-1- Ex. 1-TD 2-TD 3-TD 4-TD 5 + 6 + 7-TD dodecene undecene Dimer # [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] 1 95.6 0 0 0 0 1.6 2.5 0 2 96.0 0 0 0 0 1.6 2.4 0 3 96.3 1.5 0.4 0.2 0.4 0.6 0.6 0

[0113] The initial concentration of 1-tetradecene was about 96 mol % and main side components were 2-ethyl-1-dodecene and 2-propyl-1-undecene. The overall concentration of the branched hydrocarbons was about 4 mol % and no dimers were detected.

[0114] Catalytic Materials

[0115] The performance of the silicon-aluminum mixed oxide material according to the present invention (Catalyst 3) was compared to catalytic reference materials known to be active in isomerization reactions (Catalyst 1 and Catalyst 2).

[0116] Catalyst 1 (Reference): SAPO-39

[0117] Catalyst 2 (Reference): Amberlyst 15

[0118] Catalyst 3 (invention): silicon-aluminum mixed oxide

[0119] Performance Tests in Batch Mode Operation

[0120] The experimental conditions for all experiments in the batch mode are summarized in Table 2. Examples with reference catalysts are marked with the term “*)”. The term “tetradecene” is abbreviated throughout the tables as “TD”.

TABLE-US-00002 TABLE 2 Reaction conditions for the experiments in batch mode. Ex. Catalyst m.sub.Feed m.sub.cat Temp. Reaction time # # [g] [g] [° C.] [min] 4 — 775.00 — 200 380 5 3 775.00 30.000 130 842 6 3 775.00 30.000 130 977 7 1 775.00 30.000 200 1300 8 2 20.00 1.002 110 300 9 3 20.02 1.008 200 300 10 1 20.00 1.002 200 300 11 3 20.01 0.992 200 570 12 1 20.01 1.005 200 570 13 2 20.01 1.000 110 570 14 3 20.01 0.997 130 335 15 3 20.01 1.013 175 335 16 3 20.00 1.002 225 335 17 3 20.01 0.992 245 335 18 3 20.00 1.009 175 56 19 3 20.10 1.006 175 117 20 3 20.00 1.007 175 191

[0121] Table 2 gives an overview of the reaction conditions used for the different reactions run under batch mode. At first, a blind test was carried out to determine the influence of the reactor wall and the thermal stability of the used alpha-C14 olefin (see Example 4). Different reaction conditions were used to determine the catalytic performance of the selected catalysts to identify the best catalyst for the isomerization reaction, to find the optimum reaction conditions for the catalyst and to identify the influence of different feed qualities on the catalytic performance. The amount of feed was approximately 20 g and the amount of catalyst between 0.99 and 1.01 g (see Examples 5-10). Two different reaction times at 300 min and 570 min were compared.

[0122] The reaction temperature was varied in the range of 130 to 245° C. for the catalyst of the present invention (see Examples 11-14). Approximately 1 g of catalyst and 20 g of 1-tetradecene were filled in the reactor in each example.

[0123] The reaction time was further varied in the range from 56 minutes to 335 minutes for the catalyst of the present invention (see Examples 15-20 and 12). Approximately 1 g of catalyst and 20 g of 1-tetradecene were filled in the reactor in each example.

[0124] Results for the Batch Operation Examples

[0125] The following Table 3, the results for the above-mentioned examples are regarding conversion and product distribution are shown.

TABLE-US-00003 TABLE 3 Results of the double bond distribution of C.sub.14-olefins in batch reactions. 2-ethyl-1- 2-propyl-1- Ex 1-TD 2-TD 3-TD 4-TD 5 + 6 + 7-TD dodecene undecene Dimer # [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] 4 92.2 2.7 0.9 0.3 — 1.6 2.3 — 5 86.5 6.5 1.6 1.0 0.5 1.4 2.7 — 6 45.6 32.5 11.2 4.0 1.8 0.7 1.1 2.9 7 37.3 20.3 13.2 11.3 12.4 0.8 1.1 3.6 8 11.9 49.6 19.9 8.4 6.1 — — 4.0 9 1.2 14.9 14.2 17.3 41.9 — — 10.5 10 86.5 8.8 1.0 — — — — 3.8 11 0.9 12.5 11.8 15.8 38.1 — — 21.0 12 86.8 8.1 1.1 — — — — 4.2 13 1.8 34.6 22.5 16.3 15.6 — — 9.0 14 78.8 15.5 1.7 — — — — 4.1 15 1.0 16.1 14.0 15.3 29.8 — — 23.8 16 0.8 9.7 7.7 9.9 25.7 — — 46.1 17 0.4 3.9 3.5 4.1 9.8 — — 78.5 18 42.0 35.7 10.5 3.9 2.6 — — 5.4 19 15.9 44.5 18.3 8.8 6.8 — — 5.7 20 7.7 42.9 21.5 11.9 10.4 — — 5.7

[0126] Blind Test

[0127] The results for the blind test show that the alpha-C14 olefin is thermally stable up to 200° C. as the mole fraction of 1-tetradecene decreased only slightly to 92.2 mol % (see Example 4). The concentration of branched hydrocarbons remained unchanged at about 4 mol % and there was no formation of dimers observed.

[0128] Catalyst Variation

[0129] Examples 5-7 compare the conversion achieved by using the different catalysts and the double bond distribution obtained thereby. Reaction temperatures were 110° C. for Catalyst 2 (Example 5) and 200° C. for Catalyst 3 (Example 6) and Catalyst 1 (Example 7) and the reaction time was 300 minutes, respectively. For the use of Catalyst 2, a lower temperature had to be chosen, because the Amberlyst resin tends to decompose at higher temperatures and unfavorable dimer formation was observed under such conditions. On the other hand, the conversion at 110° C. for the two other catalyst were considerably slow.

[0130] The 1-tetradecene conversions are 87.6%. 98.7% and 9.5% for Examples 5, 6 and 7, respectively. The isomerization with Catalyst 2 showed the highest olefin concentration at 2-tetradecene (49.6 mol %). With increasing the carbon number for the double bond position in the carbon chain, the concentration of the respective internal olefin decreased. The lowest concentration was found for 5+6+7-tetradecene.

[0131] For Catalyst 3, under these conditions he highest internal olefin isomer concentrations were found with distribution close to equilibrium. Under equilibrium conditions, one would expect 14.7 mol % for each isomer. Experimentally, this value is nearly reached for the 2-, 3- and 4-isomer. For the 5+6+7-tetradecene lumped isomers, 41.9 mol % were obtained compared to calculated 44.1% at equilibrium. At the same time, the concentration of dimers amounted to moderate 10.5 mol %. Catalyst 1 showed the lowest 1-tetradecene conversion. The residual concentration of 1-tetradecene was 86.5 mol % after the applied reaction time. The mole fraction of 2-tetradecene amounted to 8.8 mol %; the concentration of all other internal olefins was lower than 1.0 mol %.

[0132] Examples 8-10 are a repetition of Examples 5-7 by increasing the reaction time from 300 to 570 minutes to investigate the influence of reaction time on equilibrium compositions. Due to the longer reaction time, the conversion of 1-tetradecene increased to 98.1 when using Catalyst 2 (Example 10). The concentration of the more internal double bond position isomers increased as well, but equilibrium composition could not be reached. The highest concentration of internal olefin was found for 2-tetradecene (34.6 mol %) and the mole fraction of dimers increased by a factor of 2.3.

[0133] Increasing the reaction time only slightly changed the isomer composition of internal olefins by using Catalyst 3. However, the concentration of dimers increased by a factor of 2. With Catalyst 1, no significant changes in the product composition were observed.

[0134] Temperature Variation

[0135] For the catalyst of the present invention, further examples were made to show the temperature dependence of 1-TD conversion and isomer distribution respectively (see Examples 6 and Examples 11-14). At 130° C. (Example 11), the conversion of 1-tetradecene was only 17.6% . The highest concentration of internal olefins was found at 2-tetradecene (15.5 mol %). The mole fraction of other internal olefins was negligible. The results at 175° C. (Example 12) and 200° C. (Example 6; shorter reaction time) showed nearly full conversion of approximately 99% and a nearly equal distribution of internal olefins over the carbon chain, i.e. equilibrium conditions are met. With increasing the reaction temperature further, the isomer composition does not change anymore significantly (i.e. equal distribution of the double bond position in the tetradecene except the alpha position), but undesired dimer formation increases significantly. At 245° C., most of the tetradecene is converted into dimers.

[0136] Reaction Time Variation

[0137] When varying the reaction time (see Examples 12 and 15-20), the conversion of 1-tetradecene increased with increasing reaction time. After 56 minutes, the conversion of 1-tetradecene was 56.1% (Example 15) and increases to 99% after 335 minutes (Example 12). However, the mole fraction of dimers also increased from 4.8 mol % to 23.8 mol % with increasing the reaction time. In all experiments, the maximum mole fraction of internal olefin was found at 2-tetradecene, indicating that chemical equilibration of double bond position has not been reached. Only at 335 minutes (Example 12), the concentration of internal olefins was almost equally distributed over the carbon chain length. However, in this case, the concentration of dimers was already very high (23.8 mol %).

[0138] Performance Tests in Continuous Mode Operation

[0139] In the continuous fixed bed operation mode, the long-term stability of the catalyst of the present invention was investigated. Four different tests were made with different parameter sets were performed. Two reactors were run simultaneously, and two different flow rates were chosen as initial parameters.

[0140] Run 1a (Example 21)

[0141] In Run 1a, the 1-tetradecene was flown with 1 mL/min through the reactors filled with the catalyst of the present invention. The weight hourly space velocity amounted to 3.88 h.sup.−1. The reactor was heated to 180° C. After 11 days, the temperature was reduced to 170° C. and the other parameters kept constant. After 18 days, the flow rate was reduced to 0.8 mL/min (resulting in a WHSV of 3.1 h.sup.−1). The other parameters were kept constant. The total time-on-stream amounted to 32 days. Table 4 shows the reaction conditions and the conversion of 1-tetradecene as obtained.

TABLE-US-00004 TABLE 4 Reaction parameters and conversion X of 1-tetradecene in Run 1a. Reaction time Feed WHSV Temperature Conversion [days] [mL/min] [h.sup.−1] [° C.] [%] 4 1.0 3.88 180 96.7 6 1.0 3.88 180 96.6 8 1.0 3.88 180 95.4 11 1.0 3.88 180 95.0 13 1.0 3.88 170 92.7 18 1.0 3.88 170 89.1 22 0.8 3.10 170 89.9 27 0.8 3.10 170 85.2 32 0.8 3.10 170 85.8

[0142] The product distribution of the different isomers for the sampling in Run 1a are reported in the following Table 5.

TABLE-US-00005 TABLE 5 Results of the double bond distribution of C.sub.14-olefins in Run 1a. Reaction 1-TD 2-TD 3-TD 4-TD 5-TD 6 + 7-TD Dimer time [days] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] 0 96.0 0 0 0 0 0 0 4 3.2 25.3 18.5 17.6 12.8 15.9 6.6 6 3.3 26.3 18.7 17.5 12.7 15.2 6.1 8 4.4 28.6 19.5 16.6 12.0 13.3 5.7 11 4.8 29.7 19.9 16.0 11.3 12.1 6.1 13 7.0 37.8 21.7 14.2 8.0 6.3 5.0 18 10.4 42.6 21.3 11.9 5.7 4.1 4.0 22 9.7 42.8 22.0 11.8 5.3 4.0 4.4 27 14.2 46.4 20.3 9.2 3.9 2.4 3.8 32 13.6 45.8 20.4 9.4 4.0 2.6 4.3

[0143] After 4 hours on-stream, a high conversion level of 96.7% was obtained at the reactor outlet.

[0144] The isomers consisted of a high level of inner double bond positions, the 2-position slightly dominating with 25.3%. With increasing time-on-stream a slight deactivation of the catalyst was observed in Run 1a, which can be seen in a reduced conversion and less equilibrated concentration of the respective inner double bond isomers. When reducing the reaction temperature to 170° C., the conversion was further diminished and the double bond position at the 2-position became more dominating. With increasing time-on-stream, deactivating is increased. After 18 days, the feed rate was reduced to 0.8 mL/min (WHSV=3.1 h.sup.−1) resulting in a slight conversion increase to 89.9% due to the higher residence time in the catalyst bed. The Isomer composition, however, was not significantly affected. In all conditions, the dimer formation was low and between 6.6% on day 4 and 4.3% after 32 days.

[0145] Run 1 b (Example 22)

[0146] In Run 1 b, the 1-tetradecene was flown with 0.9 mL/min through the reactors filled with the catalyst of the present invention. The weight hourly space velocity amounted to 3.49 h.sup.-1. The reactor was heated to 180° C. After 6 days, the flow rate was increased to 1.2 mL/min (WHSV=4.65 h.sup.-−1). The other parameters were kept constant. After 11 days, the reactor temperature was reduced to 170° C. The other parameters were kept constant. The total time-on-stream amounted to 32 days.

[0147] The following Table 6 shows the reaction conditions and the conversion of 1-tetradecene as obtained.

TABLE-US-00006 TABLE 6 Reaction parameters and conversion X of 1-tetradecene in Run 1b. Reaction time Feed WHSV Temperature Conversion [days] [mL/min] [h.sup.−1] [° C.] [%] 4 0.9 3.49 180 97.0 6 0.9 3.49 180 96.2 8 1.2 4.65 180 95.3 11 1.2 4.65 180 94.8 13 1.2 4.65 170 90.0 18 1.2 4.65 170 88.6 22 0.8 3.10 170 91.6 27 0.8 3.10 170 89.0 32 0.8 3.10 170 88.0

[0148] The product distribution of the different isomers for the sampling in Run 1 b are reported in the following Table 7.

TABLE-US-00007 TABLE 7 Results of the double bond distribution of C.sub.14-olefins in Run 1b. Reaction 1-TD 2-TD 3-TD 4-TD 5-TD 6 + 7-TD Dimer time [days] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] 0 96.0 0 0 0 0 0 0 4 2.9 21.6 16.4 17.9 14.6 19.1 7.5 6 3.6 23.7 17.9 17.0 13.7 17.0 7.0 8 4.5 27.7 19.1 16.8 12.1 14.0 5.9 11 5.0 28.4 19.2 16.1 11.6 12.8 6.8 13 8.7 39.3 20.7 13.7 7.0 6.0 4.5 18 10.9 41.0 20.7 11.5 6.3 4.6 5.2 22 8.0 39.3 21.3 13.0 6.6 7.5 4.5 27 10.5 42.2 21.3 11.3 7.1 3.6 4.0 32 11.5 42.4 20.7 11.3 5.4 4.1 4.7

[0149] After 4 hours on-stream, a high conversion level of 97% was obtained at the reactor outlet. The isomers consisted of a high level of inner double bond positions, close to equilibrium composition, the 2-position slightly dominating with 21.6%. With increasing time-on-stream, a slight deactivation of the catalyst was also observed in Run lb, which can be seen in a reduced conversion and less equilibrated concentration of the respective inner double bond isomers. After increase of the feed stream to 1.2 mL/min on day 6, the conversion expectedly decreased, and the isomer composition shifted towards the 2-position. When reducing the reaction temperature to 170° C. after day 11, the conversion was further diminished and the double bond position at the 2-position became still more dominating. After 18 days, the feed rate was reduced to 0.8 mL/min (WHSV =3.1 h.sup.−1) resulting in a slight conversion increase to 91.6% due to the higher residence time in the catalyst bed. The isomer composition, however, was not significantly affected. In all conditions, the dimer formation was low and between 7.5% on day 4 and 4.7% after 32 days.

[0150] Run 2a (Example 23)

[0151] In Run 2a, the 1-tetradecene was flown with 1 mUmin through the reactors filled with the catalyst of the present invention. The weight hourly space velocity amounted to 3.88 h.sup.−1. The reactor was heated to 180° C. After 8 days, the temperature was reduced to 170° C. and the other parameters kept constant. Total time-on-stream amounted to 25 days. The following Table 8 shows the reaction conditions and the conversion of 1-tetradecene obtained.

TABLE-US-00008 TABLE 8 Reaction parameters and conversion X of 1-tetradecene in Run 2a. Reaction time Feed WHSV Temperature Conversion [days] [mL/min] [h.sup.−1] [° C.] [%] 4 1.0 3.88 180 93.8 8 1.0 3.88 180 92.1 13 1.0 3.88 170 88.5 19 1.0 3.88 170 84.4 25 1.0 3.88 170 71.5

[0152] The product distribution of the different isomers for the sampling in Run 2a are reported in the following Table 9.

TABLE-US-00009 TABLE 9 Results of the double bond distribution of C.sub.14-olefins in Run 2a. Reaction 1-TD 2-TD 3-TD 4-TD 5-TD 6 + 7-TD Dimer time [days] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] 0 96.0 0 0 0 0 0 0 4 5.9 27.3 18.3 16.0 11.5 14.5 6.5 8 7.6 31.5 19.3 15.3 10.4 11.1 4.9 13 11.0 42.3 21.3 11.2 5.5 3.7 4.9 19 14.9 42.7 19.1 9.5 4.1 5.6 4.1 25 27.3 45.4 15.1 5.2 1.8 1.3 4.0

[0153] After 4 hours on-stream, a high conversion level of 93.8% was obtained at the reactor outlet. The isomers consisted of a high level of inner double bond positions, the 2-position slightly dominating with 27.3%. With increasing time-on-stream, a slight deactivation of the catalyst was observed, which can be seen in a reduced conversion and less equilibrated concentration of the respective inner double bond isomers. When reducing the reaction temperature to 170° C., the conversion was further diminished and the double bond position at the 2-position became more dominating. With increasing time-on-stream, deactivating was increased. After 25 days, 71.5% of the 1-tetradecene was converted. In all conditions, the dimer formation was low and between 5.9% on day 4 and 4% after 25 days.

[0154] Run 2b (Example 24)

[0155] In Run 2b, the 1-tetradecene was flown with 0.9 mL/min through the reactors filled with the catalyst of the present invention. The weight hourly space velocity amounted to 3.49 h.sup.−1. The reactor was heated to 180° C. After 4 days, the flow rate was increased to 1.2 mL/min (WHSV =4.65 h.sup.−1). The other parameters were kept constant. After 8 days, the reactor temperature was reduced to 170° C. The other parameters were kept constant. Total time-on-stream amounted to 25 days. The following Table 10 shows the reaction conditions and the conversion of 1-tetradecene obtained.

TABLE-US-00010 TABLE 10 Reaction parameters and conversion X of 1-tetradecene in Run 2b. Reaction time Feed WHSV Temperature Conversion [days] [mL/min] [h.sup.−1] [° C.] [%] 4 0.9 3.49 180 96.1 8 1.2 4.65 180 97.0 13 1.2 4.65 170 95.6 19 1.2 4.65 170 92.0 25 1.2 4.65 170 90.1

[0156] The product distribution of the different isomers for the sampling in Run 2b are reported in the following Table 11.

TABLE-US-00011 TABLE 11 Results of the double bond distribution of C.sub.14-olefins in Run 2b. Reaction 1-TD 2-TD 3-TD 4-TD 5-TD 6 + 7-TD Dimer time [days] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] [mol %] 0 95.7 0 0 0 0 0 0 4 3.7 19.7 16.4 17.2 15.3 19.2 8.5 8 2.9 23.6 17.2 17.8 13.2 17.4 8.0 13 4.2 30.5 19.8 16.8 11.5 11.7 5.4 19 7.7 34.8 20.0 13.1 7.5 12.3 4.6 25 9.5 39.0 21.1 13.4 7.1 6.2 3.6

[0157] After 4 hours on-stream, a high conversion level of 96.1% was obtained at the reactor outlet. The isomers consisted of high level of inner double bond positions, close to equilibrium composition, the 2-position slightly dominating with 19.7%. After increase of the feed stream to 1.2 mL/min on day 4, the conversion did not decrease significantly but the isomer composition shifted towards the 2-position (23.6%). When reducing the reaction temperature to 170° C. after day 8, the conversion was further diminished and the double bond position at the 2-position became still more dominating. Under all conditions, the dimer formation was low and between 8.5% on day 4 and 3.6% after 25 days.

[0158] Conclusions:

[0159] According to the present invention, the reaction temperature and mean WHSV are the important parameters in the isomerization process when using the silicon-aluminum mixed oxide catalyst. The results achieved with the four runs showed that a reaction temperature of about 180° C. leads to a conversion from the used alpha-olefin to inner olefins of about 95% with good distribution of the inner olefins over the carbon chain and a dimer fraction of about 6.5 to 8.5 mol %. The dimer fraction could be decreased well below 5 mol % by reducing the reaction temperature to 170° C.

[0160] The equilibrium composition of the internal olefins shifted towards lower double bond positions with decreasing the catalytic activity over the time. The used catalyst showed good performance after 32 days long term stability test.