Preparation of alpha-olefin by ethenolysis

Abstract: Alpha-olefin is prepared from internal and/or vinylidene olefin by reacting the internal and/or vinylidene olefin with ethylene in the presence of a catalyst consisting essentially of Be₂O₇ and B₂O₃ on Al₂O₃.

Description: This invention relates generally to the preparation of alpha-olefins from internal or vinylidene olefins and more specifically to a process to ethenolize internal olefins and isomerize/ethenolize vinylidenes to vinyl olefins using a B₂O₃ modified Re₂O₇ on Al₂O₃ catalyst. The ethylene chain growth process for producing alpha-olefins (vinyl olefins) using triethylaluminum followed by olefin displacement as practiced commercially can produce olefins containing from 4 up to 30 or more carbon atoms. Although mainly alpha-olefins are produced, some vinylidene and internal olefins also result. These olefin by-products are generally less useful than alpha-olefins and in some applications, such as the production of sulfonic acids for detergents, vinylidene olefins form tertiary mercaptans which are very difficult to oxidize to sulfonic adds. Separation of such olefins by distillation is difficult. We have discovered a novel process for upgrading α-olefin mixtures containing such olefins to convert the vinylidene and internal olefins to α-olefins without any significant isomerization of α-olefins. US-A-3,785,956 discloses the disproportionation of a feed composed of ethylene and branched and linear olefins with a catalyst such as rhenium oxide on aluminum while maintaining the conversion of the linear olefins within the range of 30-50 percent. It has been reported by Xiading et al., J. Chem. Soc. Farady Trans. 1, 1986, 82, 1945-1953 that Re₂O₇/Al₂O₃ · B₂O₃ - MR₄ (where M = Sn or Pb and R = alkyl) catalysts can be used for the methathesis of alkenes, especially functionalized alkenes such as methyl oleate. This catalyst system is not useful in the upgrading ethenolysis of alpha-olefin mixtures because of its strong isomerization activity for alpha-olefins. DE-A-15 93 292 discloses the isomerisation of internal olefins to α-olefins in presence of a catalyst consisting of Re₂O₇ on Al₂O₃. In accordance with this invention there is provided a process for preparing alpha-olefin from an internal or vinylidene olefin or mixtures thereof comprising reacting said internal or vinylidene olefin or mixtures thereof with ethylene in the presence of a catalyst which essentially consists of 4 to 20 weight percent Re₂O₇ and 0.5 to 2 weight percent B₂O₃ on Al₂O₃, having a high surface area and which is present in an amount of from 1 to 10 weight percent based on the total weight of olefins in the reaction mixture. The process of the invention is useful in converting both vinylidene and internal olefins to alpha-olefins either separately or in admixture with one another in any proportions. The process is particularly useful in upgrading alpha-olefin products containing such vinylidene and/or internal olefins and especially those mixtures which result from ethylene chain growth on triethylaluminum followed by olefin displacement. Such olefin products contain from 4 to 30 carbon atoms and usually from 6 to 30 carbon atoms, depending upon the reaction conditions. When the ethylene chain growth process is used to make olefins containing 12 or less carbon atoms the amount of alpha olefin produced is predominant (80 mole percent or more). When used to make higher olefins the amounts of internal and vinylidene olefins increase such that the mixture can contain, for example, from 0-20 mole percent of internal olefins and from 5 to 50 mole percent vinylidene olefins and, typically, 1.5 to 8 mole percent internal olefins and 5 to 40 mole percent vinylidene olefins with the balance being alpha-olefins. The catalyst compositions are prepared, for example, by the impregnation of a high surface area Al₂O₃ with an aqueous solution of Re₂O₇ (perrhenic acid solution) and H₃BO₃. A slight excess of water can be used for good dispersion. The impregnated Al₂O₃ is then dried in situ or in a tumble dryer and then calcined at a temperature of from 300° to 650° C, preferably 450° to 550° C, under dry air or oxygen for 0.5 to 10 hours. Particularly effective catalyst compositions contain from 4 to 20 weight percent Re₂O₇ and from 0.5 to 6 weight percent B₂O₃ on Al₂O₃ and especially 10-15 weight percent Re₂O₇ and 0.5 to 2 weight percent B₂O₃ on Al₂O₃. The catalyst is used in an amount which is effective to ethenolize internal olefins and isomerize/ethenolize vinylidene olefins to vinyl olefins at a reasonable rate. Weight ratios of from 10 to 100 olefin to catalyst are suitable and preferably 30 to 60 (1 to 10 wt % catalyst and, preferably, 1.5 to 3.5 wt % catalyst based on the total weight of olefins in the reaction mixture). The catalyst can be regenerated by heat treatment to remove residual olefins and burning off the residual coke at 400° to 525° C with N₂ and then diluted air (N₂) prior to calcination. It is believed that the catalyst first promotes the isomerization of the vinylidene olefin to a trisubstituted olefin which can then be ethenolized to provide an alpha-olefin and a new vinylidene olefin of lower molecular weight. The latter vinylidene olefin can then be more easily removed from the α-olefins by conventional techniques such as distillation. The reaction is carried out, for example, in a pressure vessel with agitation under an ethylene pressure of 2.06 to 20.67 MPa (300 to 3000 psig) and preferably from 4.8 to 10.33 MPa (700 to 1500 psig) at temperature of from 25° to 100° C and preferably from 40° to 85° C. The invention is further illustrated by, but is not intended to be limited to, the following examples. Catalyst Preparation A Re₂O₇/B₂O₃/Al₂O₃ catalyst is prepared which contains 10 wt % Re₂O₇ and 1.9 wt % B₂O₃ on Al₂O₃ by the following procedure. 1. Dissolve 0.30 gram H₃BO₃ in 9.0 grams of 10 wt % Re₂O₇ in water solution (a perrhenic acid solution) with or without warm-up. 2. Add 9.0 grams of high surface area (HSA) Al₂O₃ support to absorb the solution. 3. Calcine the catalyst under dry air (usually 2 SCFH) at high temperature (usually 500-525° C) for 1-5 hours (usually 2 hours). 4. Cool down the calcined Re₂O₇ (10 wt %)/B₂O₃ (1.9 wt %)/Al₂O₃ catalyst with air or N₂, and store in a glass bottle free from moisture. Catalysts with different amounts of Re₂O₇ and B₂O₃ are prepared by varying the amounts of H₃BO₃ and Re₂O₇ which are added to the Al₂O₃ support. Example 1 Under a small N₂ purge, a clean, dry, 300 cm³ (cc) stainless steel autoclave is charged with 3.0 grams of calcined Re₂O₇ (4.8 wt %)/B₂O₃ (5.6 wt %)/Al₂O₃ catalyst and 50 grams of a dry, primarily C₁₆₋₂₀ olefin mixture. The autoclave is closed, pressure tested with about 1.38 MPa (200 psig) ethylene and then charged with 5.31 MPa (770 psig) ethylene. The autoclave is heated to 50° C with agitation and maintained at about 50° C with the ethylene pressure ranging from 5.72-6.68 MPa (830-970 psig). Samples are taken through a dip tube and analyzed by gas chromotograph and NMR. After reaction the autoclave is cooled and excess ethylene vented. The olefin solution is decanted and the catalyst saved for regeneration. The reaction data are set out in Table I along with a comparison run in which the catalyst did not contain any B₂O₃. The NMR results demonstrate that the process of Example 1 converted significantly more of the internal and vinylidene olefins to α-olefins than the comparison using only a Re₂O₇/Al₂O₃ catalyst. Examples 2-3 The process of Example 1 is repeated using 86 and 123.8 grams of a dry primarily α-C₁₄ olefin mixture and 2.87 and 2.07 grams of catalysts containing 5 and 10 wt percent Re₂O₇ and 3.8 wt % B₂O₃ on Al₂O₃, respectively. The reaction data are set out in Table II along with a comparison in which the catalyst contained no B₂O₃. α-C₁₄ = (alpha C₁₄ = ) % in C 14=, s is a measure of selective performance of the catalyst. Percentage of α-C₁₄ = plus C₂₆ = is a measure of isomerization of α-olefin(s) by the catalyst. The results show that the Re₂O₇/B₂O₃/Al₂O₃ catalysts of Examples 2 and 3 gave equivalent results to the Re₂O₇/Al₂O₃ comparison using, in the case of Example 2 a catalyst having one-half the amount of Re₂O₇, and in the case of Example 3, a catalyst having the same amount of Re₂O₇ but at only one-half the catalyst concentration. Example 4 A α-C₁₄ olefin mixture similar to that used in Example 2 is upgraded by ethenolysis according to the following procedure. Under a small N₂ purge, charge a clean, dry 300 cm³ (cc) S.S. autoclave with 3.75 grams of calcined Re₂O₇ (10 wt %)/B₂O₃ (1.9 wt %)/Al₂O₃ catalyst. Add 60.0 grams dry 1-C₁₄ = olefin (about 85% α-olefin, 10% vinylidenes and 5% internal olefins). Then close up the autoclave. After pressure test with 200 psig ethylene, charge the reactor with 4.8-5.5 MPa (700-800 psig) ethylene. Heat up to 50° C with agitation on. Run the reaction at about 50° C under about 5.9 MPa (850 psig). Take samples during the reaction through a 3.2mm (1/8") diptube. After the reaction, cool down and vent off excess ethylene. Decant the metathetic olefin solution and save the catalyst for regeneration. Regeneration of the Spent Catalyst 1. Heat up the spent catalyst under N₂ (∼2 SCFH) purge to 400-500°C to remove residual olefin. 2. Slowly introduce air to N₂ to burn off coke on the catalyst at 480-525°C. (The black coke is formed during the heat treatment for removal of residual olefins.) 3. Calcine the catalyst as described above under Catalyst Preparation. The regenerated catalyst was used to enthenolize additional α-C₁₄ olefin mixture. The reaction data are set out in Table III. The results demonstrate that the regenerated catalyst is still effective. Example 5 The process of Example 4 is repeated except that the catalyst contains 0.5 wt % B₂O₃. The results show a catalyst efficiency of 115⁺ compared with 100 for the same olefin to catalyst ratio using a Re₂O₇/Al₂O₃ catalyst. The foregoing examples illustrate carrying out of the process of the invention in a batch mode. It should be understood that the process can also be carried out in a continuous mode by passing the olefin feed and ethylene through a fixed bed of the Re₂O₇/B₂O₃/Al₂O₃ catalyst.

Claims: A process for preparing alpha-olefin from an internal or vinylidene olefin or mixtures thereof comprising reacting said internal or vinylidene olefin containing 4 to 30 carbon atoms or mixtures thereof with ethylene under an ethylene pressure of from 2.07 to 20.67 MPa (300 to 3000 psig) at a reaction temperature from 25° C to 100° C in the presence of a catalyst which essentially consists of 4 to 20 weight percent Re₂O₇ and 0,5 to 6 weight percent B₂O₃ on Al₂O₃, having a high surface area and which is present in an amount of from 1 to 10 weight percent based on the total weight of olefins in the reaction mixture. The process of claim 1 wherein the olefin is an internal olefin. The process of claim 1 wherein the olefin is a vinylidene olefin. A process according to claim 1 for upgrading an alpha-olefin mixture which contains internal and/or vinylidene olefins so as to convert at least a portion of said olefins to alpha-olefin comprising reacting said mixture with ethylene in the presence of a catalyst consisting essentially of Re₂O₇ and B₂O₃ on Al₂O₃. A process according to claim 1 wherein said mixture contains 0 to 20 mole percent internal olefin from 5 to 40 mole percent vinylidene olefin with the balance being alpha-olefin. The process of claim 1 wherein the ethylene pressure is from 4,8 to 10.33 MPa (700 to 1500 psig) and the temperature is from 40° C to 85° C.

Inventors: LIN RONNY-WEN LONG, NELSON MARSHALL BUDD, PETERS BRUCE CRAIG, LIN, RONNY-WEN LONG, NELSON, MARSHALL BUDD, PETERS, BRUCE CRAIG
Applicants: ALBEMARLE CORP, ALBEMARLE CORPORATION
Application year: 1991
Main classification: C07C6
IPC codes: C07B61, C07C2, C07C6, B01J23, C07C11