Example 1
In an argon atmosphere dry box, a 500 mL flask equipped with a stirrer is charged with 20 mmol of zirconium tetrachloride anhydride (ZrCl4) and 250 mL of dry cyclohexane. The mixture is then stirred for 10 minutes at room temperature. To the stirred mixture is added triethylaluminum (TEA) and then ethylaluminum sesquichloride (EASC) to provide a mixture that has a EASC:TEA molar ratio of 3.5:1 and an aluminum to zirconium molar ratio of 7:1. The resultant mixture is then heated at 70° C. for 2 hours. The mixture is then cooled to room temperature. A 50 mL portion of the cooled mixture and is transferred to a one liter volumetric flask along with an amount of thiophene to thiophene:zirconium molar ratio of 3:1. The one liter volumetric is then charged with enough dry cyclohexane to provide one liter of catalyst system mixture. The zirconium concentration of the thus prepared catalyst system mixture/liter of cyclohexane and has an aluminum to zirconium molar ratio of 7:1, a EASC:TEA molar ratio of 3.5:1, and a thiophene:zirconium molar ratio of 3:1. The catalyst system mixture volumetric flask is then capped and removed from the argon atmosphere dry box.
Run 1-1 (Comparative)
The oligomerization apparatus as previously described is utilized using only the primary catalyst system solution pump. The oligomerization reactor is prepared for ethylene oligomerization by charging the high pressure product tank to the desired pressure using the high pressure N2 fill line. The reactor is also cycled through three high pressure N2 fill (to 800 psig-5.5 MPa) and vent cycles while isolated from the primary catalyst system solution pump. Each nitrogen purge is performed by closing the valve leading to the product tank, charging nitrogen to the autoclave through the spare entry port to a pressure of 800 psig (5.5 MPa), holding the nitrogen pressure on the autoclave for 5 minutes and then releasing the nitrogen pressure on the autoclave by opening the valve leading to the product tank. After the nitrogen of the final nitrogen purge is released, the autoclave is maintained with a slight residual nitrogen pressure. Catalyst system mixture, 200 mL, is then transferred to the catalyst system ISCO syringe pump of the prepared ethylene oligomerization apparatus. The reactor is then quickly filled organic reaction medium (cyclohexane). The diluent pump is then turned on at rate of 335 mL per hour to bring the reactor up to a reaction pressure of 925 psi (6.37 MPa). When the reactor achieves the reaction pressure, the overhead magnetic stirrer is started and set for ˜1200 rpm and the heating jacket turned on and set for 120° C. When the reactor achieves a stable temperature of 120° C., the catalyst system ISCO pump is turned on and set to feed the catalyst system mixture to the reactor at a rate of 15 mL/hr. After 30 minutes, ethylene is then introduced into the reactor at an initial rate of at 50 grams/hour and gradually increased, over a 30 minute period, to a final rate of 175 grams/hour. The oligomerization temperature is maintained by using the internal cooling coils and external heating jacket as needed. After 6 hours, the oligomerization is terminated by decreasing the catalyst system flowrate to zero, decreasing the ethylene flow rate to zero, and turning off the heating jacket. When the reactor attains room temperature, the organic reaction medium flow rate is decreased to zero, and the liquid contents of the reactor pressured into the high pressure product tank using high pressure N2.
The reactor is then opened and the solids inside the reactor and covering the internal reactor surfaces collected and added to the reactor effluent collected in the high pressure product tank. A liquid sample, 250 grams, of the product tank is collected and a known amount of internal standard (e.g. nonane) is added to the sample. The sample is then treated with 5 wt. % sodium hydroxide solution to deactivate the catalyst system. The organic layer of the sodium hydroxide treated sample is then analyzed using gas chromatographic analysis to determine oligomer product distribution, Schulz-Flory K value, carbon number purities, and catalyst system productivities. The remaining contents of the product tank are then homogenized and a second sample, 250 grams, of the product tank is taken. The second sample is then subjected to rotary evaporation for 1 h at 100° C. at −30 in Hg to effectively remove all the liquid. The mass of the remaining wax and polymer is determined. A portion of the wax is then analyzed by thermogravimetric analysis (TGA) to calculate the fraction of the solid sample that is polymer using the cutoffs of A) liquid (≤175° C.), B) waxes (175° C. to 420° C., and C) polymer ≥420° C. A second portion of the wax and polymer is analyzed by HPLC to determine the molecular weight distribution of the polymer produced in the oligomerization including Mw, Mn, and Mp. The liquid and polymer analysis results are used to determine the oligomer product distribution, Schulz-Flory K value, carbon number purities, catalyst system productivities, polymer Mw, polymer Mw maximum peak, percentage of polymer in the oligomer product, percentage of polymer having an Mw greater than 100,000, and percentage of oligomer product having a Mw greater than 1,000 g/mol.
Run 1-2.
In an argon atmosphere dry box, a 250 mL volumetric flask is charged with 0.1 mole of triethylsilane (a chain transfer agent) and then charged with enough dry cyclohexane to provide 250 mL of chain transfer agent mixture. The chain transfer agent mixture volumetric flask is then capped and removed from the argon atmosphere dry box.
A chain transfer agent feed line is connected to organic reaction medium feedline on the suction side of the organic reaction medium pump. The procedure of Run 1-1 is repeated but with the addition of the triethylsilane solution to the suction side of the diluent pump metered to provide a triethylsilane to ethylene mole ratio of 1×10−3:1 (˜15 mL/hour when ethylene flowrate is 175 grams/hour) throughout the ethylene oligomerization.
Run 1-3
In an argon atmosphere dry box, a 250 mL volumetric flask is charged with 0.1 mmole of iron(III) octanoate (a transition metal compound chain transfer agent) and then charged with enough dry cyclohexane to provide 250 mL of transition metal compound chain transfer agent mixture. The chain transfer agent mixture volumetric flask is then capped and removed from the argon atmosphere dry box.
A transition metal compound chain transfer agent feed line is connected to organic reaction medium feedline on the suction side of the organic reaction medium pump. The procedure of Run 1-1 is repeated but with the addition of the iron(III) octanoate solution to the suction side of the diluent pump metered to provide an iron(III) octanoate to ethylene mole ratio of 1×10−6:1 (˜15 mL/hour when ethylene flowrate is 175 grams/hour) throughout the ethylene oligomerization.
Run 1-4
A hydrogen feed line is connected to the ethylene feedline of the ethylene oligomerization apparatus. The procedure of Run 1-1 is repeated but with hydrogen being metered into the ethylene at a rate to provide a hydrogen to ethylene mass ratio of (1 g hydrogen)/(kg ethylene) throughout the ethylene oligomerization.
The gas chromatographic analyses and HPLC analyses of ethylene oligomerization Runs, 1-2, 1-3, and 1-4 using a chain transfer agent were reviewed and compared to the gas chromatographic analyses and HPLC analyses of ethylene oligomerization Run 1-1. The analyses show that the oligomer product that is produced in ethylene oligomerization Runs 1-2, 1-3, and 1-4 using a chain transfer agent has less than 1 wt. % of polymer and/or less than 1 wt. % compounds having a weight average molecular weight of greater than 1000 g/mol, when compared to ethylene oligomerization Run 1-1 which did not utilize a chain transfer agent. The analyses also show that the oligomer product that is produced in ethylene oligomerization Runs 1-2, 1-3, and 1-4 using a chain transfer agent produces an oligomer product comprising a polymer having a lower Mw, a polymer having a lower Mw maximum peak, a reduced percentage of polymer, and/or a polymer having a reduced percentage of polymer having a Mw greater than 100,000 when compared to ethylene oligomerization Run 1-1 which did not utilize a chain transfer agent. The gas chromatographic analyses of the oligomer product of Runs, 1-1, 1-2, 1-3, and 1-4 indicate that there is no significant discernable impact on the Schulz-Flory K value, carbon number purities, and catalyst system productivities when a chain transfer agent is utilized in the ethylene oligomerization.
