Off-line filter free Ziegler-Natta catalyst preparation

Abstract

The various embodiments provide, a magnesium titanium polymerization procatalyst, and methods for making and using the same.

Claims

1. A process to prepare an olefin polymerization procatalyst comprising a Ti.sup.3+ complex, said process comprising: a) forming a delta form MgCl.sub.2 species by combining i) a Mg compound selected from the group consisting of butylethyl magnesium (BEM), dibutyl magnesium, butyloctyl magnesium (BOM), and mixtures thereof, ii) a solvent, wherein the solvent is a C.sub.5-12 alkane or mixture thereof, and iii) a reactive organic chloride or HCl; wherein a Cl/Mg mole ratio is from 2.1 to 2.3; b) adding to said delta form MgCl.sub.2 species prepared in step a), an aluminum alkyl halide of the formula R.sup.1.sub.xAlX.sub.3-x first, a tetravalent titanium compound second, followed by an alkyl aluminum alkoxide of the formula R.sup.4.sub.yAlOR.sup.5.sub.3-y, wherein: an Al/Ti molar ratio is from about 0.7 to about 1, when measuring Al supplied from R.sup.1.sub.xAlX.sub.3-x; and the Al/Ti molar ratio is from about 1 to about 2, when measuring Al supplied from R.sup.4.sub.yAlOR.sup.5.sub.3-y; x is 1 or 2; y is 1 or 2; each R.sup.1 is a C.sub.1-8 alkyl radical; the tetravalent titanium compound is selected from the group consisting of TiR.sup.2X.sub.3, Ti(OR.sup.3)X.sub.3, TiX.sub.4, and mixtures thereof; each X is independently a halogen radical; each R.sup.2 is independently selected from the group consisting of C.sub.1-8 alkyl radicals and benzyl; and each R.sup.3, R.sup.4, and R.sup.5 is independently a C.sub.1-8 alkyl radical; wherein: a Mg/Ti molar ratio is from about 5 to about 10; and no filtration or washing steps are performed during or after formation of the olefin polymerization procatalyst.

2. The process of claim 1, wherein the reactive organic chloride is tertiary-butylchloride (tBuCl).

3. The process of claim 1, wherein step a) is performed at a temperature between about 20° C. and about 160° C.

4. The process of claim 1, wherein step a) or step b) is performed at a temperature between about 40° C. and 90° C.

5. The process of claim 1, wherein the Mg compound is butylethyl magnesium (BEM).

6. The process of claim 1, wherein the Cl/Mg mole ratio is about 2.2.

7. The process of claim 1, wherein R.sup.1.sub.xAlX.sub.3-x is selected from the group consisting of isobutylaluminum dichloride (IBADC) and ethylaluminumdichloride.

8. The process of claim 1, wherein the tetravalent titanium compound is TiCl.sub.4.

9. The process of claim 1, wherein R.sup.4.sub.yAlOR.sup.5.sub.3-y is diethylaluminumethoxide.

10. The process of claim 1, wherein the solvent is cyclohexane.

11. A solution olefin polymerization process comprising: i) adding to one or more continuous stirred tank reactor (CSTR), optionally followed by a tubular reactor, either in series or parallel: a solvent, wherein the solvent is chosen from C.sub.5-12 alkane or mixture thereof, and a procatalyst for polymerization on a delta form MgCl.sub.2 support comprising a Ti.sup.3+ complex of the formula TiCl.sub.3*[[R.sup.4].sub.a[R.sup.5O].sub.bAlX.sub.3-c].sub.d; wherein: a is 0 to 1; b is 0 to 1; c=a+b; d is from 0.33 to 1.0; each R.sup.4 and R.sup.5 is independently a C.sub.1-8 alkyl radical; each X is independently a halogen radical; at least 60% of a total Ti present is in a Ti.sup.3+ oxidation state; and no filtration or washing step is performed on the procatalyst for polymerization prior to the remaining steps; ii) adding ethylene, hydrogen, and optionally one or more comonomers selected from C.sub.3-8 comonomers to the CSTR reactor; and iii) adding an aluminum alkyl activator to the CSTR reactor in a molar ratio of about 1 to about 10, relative to an amount of the procatalyst for polymerization.

12. The polymerization process of claim 11, wherein the aluminum alkyl activator is selected from the group consisting of diethylaluminumethoxide, trialkyl aluminum compounds, and MAO.

13. The polymerization process of claim 11, wherein the solvent is cyclohexane.

14. The polymerization process of claim 11, wherein the process is performed at a temperature of at least about 220° C.

15. The polymerization process of claim 11, wherein the CSTR reactor has a hold-up time from about 30 seconds to about 5 minutes.

Description

EXAMPLES

(1) Chemicals and Reagents

(2) Purchased cyclohexane was dried and deoxygenated by passing it through a bed of deoxygenation catalyst (brand name R311 from BASF), an alumina bed (brand name Selexsorb COS/CD), and a molesieve (3A/13X) bed.

(3) Methyl pentane was purchased from Imperial oil. The solvent was dried by passing it through a bed of containing Selectsorb CD and Selectsorb CDX.

(4) 20 wt % Butylethyl Magnesium (BEM) in heptane solution was purchased from Albemarle.

(5) Isobutylaluminumdichloride (IBADC) was purchased from Sigma Aldrich with 97% by weight. It was contained in a pyrosafe and stored in a glovebox. IBADC has a boiling point of 242° C. and a density of 1.12 g/mL.

(6) 25.4 wt % Diethylaluminum Ethoxide (DEAO) in heptane solution was purchased from Akzo Nobel. DEAO has a boiling point of 98° C. and a density of 0.684 g/mL.

(7) A drying reagent with a “built in” dryness indicator (Drierite™) was purchased from Aldrich. The drying reagent was conditioned before use by drying it at 130° C. overnight followed by a secondary overnight drying step at 220° C. in a vacuum oven.

(8) 2-chloro-2-methylpropane (tert-butyl chloride or tBuCl) was purchased from Aldrich. The tBuCl was dried by placing it over the pre-dried drying reagent under an inert environment for approximately 16 hours at a ratio of 30 g of dryness indicator per 100 mL of tBuCl. The flask containing the tBuCl was covered in foil to shield it from light during this process to minimize the formation of isobutylene. The dried tBuCl was further purified by vacuum transfer. The tBuCl moisture content was 12 ppm or less and had purity above 97% after purification. All glassware used in this procedure was dried in a 120° C. oven overnight.

(9) Ethylene was purchased from Praxair as polymer grade. The ethylene was purified and dried by passing the gas through a series of purification beds including alumina (brand: Selexsorb COS), molesieve (type: 13X), and a deoxygenation bed (brand: Oxiclear®).

(10) Purchased 1-octene was dried by storing a 1-liter batch over molesieve 3A.

(11) Titanium (IV) chloride (TiCl.sub.4) was purchased from Aldrich as 99.9% purity packaged under nitrogen.

(12) Methanol was purchased as GR ACS grade from EMD Chemicals.

(13) Analytical Methods

(14) Melt index (“MI”) measurements are conducted according to ASTM method D-1238.

(15) Polymer densities are measured using ASTM D-1928.

(16) Catalyst Synthesis

(17) Catalyst Synthesis Unit (CSU):

(18) The CSU consists of two continuously stirred tank reactors (CSTR1, a 450 mL stainless steel Parr 4560-Series reactor, and CSTR2, a 2000 mL stainless steel Parr 4520-series reactor) as well as a plug flow reactor (PFR). The stir tank reactors were designed to hold pressures up to 20.6 MPa and temperatures up to 350° C., while the PFR can hold 60 mL with a design pressure up to 20.6 MPa and design temperature up to 204° C. MgCl.sub.2 can be made in the PFR through the controlled addition of BEM and tBuCl solutions with the MgCl.sub.2 being collected in CSTR2, mimicking the lab-scale one-shot addition method for MgCl.sub.2 synthesis. Alternatively, MgCl.sub.2 can be made directly in CSTR2 mimicking a simultaneous addition method. It was observed that the use of the PFR for magnesium chloride formation provided better mixing of the reactants as well as a more controlled addition which helped to form the desired δ-MgCl.sub.2 as well as assist with heat mitigation. Both the PFR method and the CSTR2 method have been used to successfully make active Ziegler-Natta catalysts. Catalyst A was made using the PFR method.

(19) When following the PFR MgCl.sub.2 formation method, the PFR was pressurized to 700 KPa before BEM and tBuCl were fast flowed into the set-up. Flow and time were then adjusted to achieve a steady operation over the course of 25 minutes. CSTR2 was pressurized to 700 KPa with nitrogen. Temperature control was not critical at this point; however the temperature was maintained above 50° C. The MgCl.sub.2 slurry produced in the PFR was collected in CSTR2 allowed to stir for about 100 mins.

(20) After the MgCl.sub.2 support was prepared, remaining reagents were directly displaced into the CSTR2 reactor tank from their respective reagent sample cylinders using nitrogen pressure (conditions as seen in table 1). The reagent cylinders were loaded in a glovebox and charged with nitrogen and then the reagents were individually injected into the reactor by opening the lower cylinder valve at the designated time. After the final reagent addition, the reactor was heated to 50° C. The reaction was allowed to stir for 60 min before the reactor contents were cooled to ˜20° C. and the pressure was reduced to 70 KPa. A transfer vessel was placed on a scale under 5 psig of pressurized nitrogen. Unfiltered catalysts were directly transferred into the vessel using the product transfer flex hose. Multiply inventive catalyst A filtration free offline Ziegler catalysts were made and combined.

(21) TABLE-US-00001 TABLE 1 Formulation of Catalyst A Catalysts Prepared on CSU Isolated BEM tBuCl IBADC TiCl.sub.4 IBADC/ DEAO DEAO/ Catalyst Catalyst (mmol) (mmol) Cl/Mg (mmol) (mmol) Ti Mg/Ti (mmol) Ti Slurry (g) Batch 1 548.8 1205.2 2.20 124.0 72.9 1.70 7.53 87.3 1.20 1300 Batch 2 554.4 1217.7 2.20 125.8 72.9 1.73 7.60 88.3 1.21 1380 Batch 3 548.8 1205.2 2.20 125.8 74.1 1.70 7.41 88.8 1.20 1350
Catalyst A (Batch 1, 2 and 3 combined) was diluted in cyclohexane and final catalyst vessel contains 8.430 kg of catalyst A (4.57 wt % solids in cyclohexane with 0.1199 wt % Ti).
Catalyst A Evaluation at Solution Pilot Plant

(22) Testing of an example of the offline Ziegler Natta (Z/N) slurry catalyst (Catalyst A) at the pilot plant scale continuous polymerization facility and Catalyst B and Catalyst C as comparative examples (Catalyst B was made according to the procedure disclosed in U.S. Pat. No. 9,481,748 catalyst 2c and Catalyst C was made according to the procedure disclosed in U.S. Pat. No. 9,481,748 catalyst 9) was carried out.

(23) The examples in Table 2 illustrate the continuous flow, solution copolymerization of ethylene and 1-octene at a medium pressure using a pilot plant reactor system and using Ziegler catalyst systems. A pilot plant reactor system consists of two reactors. The first reactor was a continuous stirred tank reactor (CSTR) with a volume of 24.0 liters. The second reactor was a tubular reactor (AFT) having a volume of 82% of the CSTR volume (19.7 liters). Catalysts were fed into the CSTR. Monomer and solvent were split between the two reactors as indicated in Table 2. An offline Ziegler Natta filtration free slurry catalyst (Catalyst A) with an activator consisting of diethyle aluminuin ethoxide (DEAO) was used in the experiments. For comparison of Catalyst A, a comparative Ziegler Natta (Z/N) catalyst systems (Catalyst B and C) were also used and described in the next session. In Table 2, Product 3 (the product produced in this reactor configuration establishes a “baseline” reactor operating conditions for a given melt index, density and stress exponent). Product 2 was made with Catalyst B with the same aluminum activator. The reactor operating conditions were adjusted to yield similar melt index, density and stress exponent as in the product 3. The same strategy was applied for inventive Catalyst A to produce Product 1.

(24) Catalyst A or Catalyst B was pumped into the continuous flow polymerization reactor using the slurry delivering system. The slurry delivery system consisted of a slurry cylinder, agitated slurry day tank, recirculation loop, slurry catalyst metering pump and solvent diluent loop. The diluted slurry catalyst was transferred from the slurry cylinder to the slurry day tank in several charges by pressurizing/sparging the cylinder with nitrogen. Once the slurry catalyst was transferred into the slurry catalyst day tank, the agitator and recirculation pump were started to keep the catalyst slurry in suspension and constant composition. The temperature of the diluted slurry catalyst was maintained at ambient temperature. Tank pressure was maintained at 300 kPag. When the slurry catalyst was ready to be transferred to the reactor, the slurry catalyst delivery pump was started and slurry catalyst was lined up to the pump. At the discharge of the slurry catalyst delivery pump, a high flow solvent diluent was used to keep the slurry catalyst in suspension and aid in delivery the catalyst to the reactor. The diluent flowrate was maintained at 15 kg/hr. The temperature of the solvent was controlled at 25° C. The solvent and slurry catalyst were pumped into a flow transmitter and the flow was recorded. The slurry catalyst flowrate into the reactor was calculated by the difference between the diluent flowrate and combined diluent and slurry catalyst flowrate. Slurry catalyst flows (and ppm's) into the reactor are adjusted by changing the slurry catalyst delivery pump motor variable frequency drive or pump stroker.

(25) The inline formed Z/N catalyst system (Catalyst C) consisting of titanium tetrachloride (TiCl.sub.4), butyl ethyl magnesium (BEM) and tertiary butyl chloride (tBuCl), with an activator consisting of triethyl aluminum (TEAL) or diethyl aluminum ethoxide (DEAO) was used. The BEM and TEAL were provided “premixed” (20/1 Mg/Al mole ratio). All catalyst components were mixed in the methyl pentane solvent within the Catalyst Torpedo. The mixing order was BEM/TEAL and tBuCl (Section #1); followed by TiCl.sub.4 (Section #2); then followed by DEAO (Section #3). The catalyst was pumped into the reactor together with the methyl pentane solvent. The catalyst flowrate had an aim set point expressed as parts per million Ti by weight and was adjusted to maintain total ethylene conversions above 80%.

(26) A list of other abbreviations used in the Table 2 follows: hr: hour wt %: weight percent wt/wt: weight/weight Temp: temperature C: degrees Celsius ppm: parts per million by weight

(27) TABLE-US-00002 TABLE 2 Catalyst A, B and C and catalyst performance Catalyst A Catalyst B Catalyst C (Product 1) (Product 2) (Product 3) Overall units values values values TSR kg/hr 500 600 600.1 FE % in wt % 13.6 13.6 12.0 (CSTR) FE % in AFT wt % 15.5 15.4 13.9 R2 FT split ratio 80 80 80 FC/FE (wt/wt) ratio 0.4 0.4 0.45 H2 in R2 ppm 1 1 1 H2 in AFT ppm 0.5 0.5 0.5 R2 C. 199.4 199.2 182.1 temperature R2 Q % 90 90 89.9 AFT C. 224.6 230.3 212.8 temperature Total Q FE % 92.5 91.7 92.2 Overall 87.1 92.6 83.8 polymer production rate Polymer properties Density g/cc 0.9226 0.9205 0.9215 I2 g/10 min 1.09 1.04 0.98 S.Ex 1.31 1.32 1.33

(28) As demonstrated in Table 2, inventive Catalyst A can operate 12° C. higher than inline formed Ziegler Catalyst C for the product with similar melt index and density. Although the catalyst A run 6° C. below catalyst B. However, filtration free Catalyst A is much easier for scaling up and commercialization. Furthermore, the inventive Catalyst A is also much cheaper to make.