High Throughput Experimentation Protocol for Quantitative

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Kinetics, Catalysis, and Reaction Engineering

A High Throughput Experimentation Protocol for Quantitative Measurements of Regioselectivity in Ziegler-Natta Polypropylene Catalysis Antonio Vittoria, Alessio Mingione, Raffaele Andrea Abbate, Roberta Cipullo, and Vincenzo Busico Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.9b02801 • Publication Date (Web): 24 Jul 2019 Downloaded from pubs.acs.org on July 26, 2019

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Industrial & Engineering Chemistry Research

A High Throughput Experimentation Protocol for Quantitative Measurements of Regioselectivity in Ziegler-Natta Polypropylene Catalysis Antonio Vittoria,a, ‡ Alessio Mingione,b, ‡ Raffaele Andrea Abbate,a, † Roberta Cipullo,* ,a, b and Vincenzo Busico a ,b.

aDepartment

Naples, Italy

of Chemical Sciences, Federico II University of Naples, Via Cintia, 80126 bHTExplore

s.r.l., Via R. Morandi 12, 80124 Naples, Italy

1 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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ABSTRACT: This paper introduces a High Throughput Experimentation method for fast and accurate evaluations of regioselectivity in Ziegler-Natta (ZN) propene polymerizations. With a simple protocol, the (very low) fraction of regioirregular 2,1 monomeric units in the polymers can be quantitated by means of

13C

NMR chain-end analyses on single H2-terminated

polypropylene samples. The method, that was successfully validated for three representative ZN catalyst systems, also provides information on catalyst ‘dormancy’ and propensity to undergo chain hydrogenolysis. This opens the door to the rapid and accurate implementation of Quantitative Structure-Activity Relationship (QSAR) databases of regioselectivity and ‘hydrogen response’ in this important industrial catalysis.

KEYWORDS: Ziegler-Natta catalysts, regioselectivity, hydrogen response, High Throughput Experimentation, polypropylene.

INTRODUCTION Ziegler-Natta (ZN) catalyst systems of composition MgCl2/TiCl4/ID-AlR3/ED (ID = Internal Donor, ED = External Donor) are dominant in industry for the production of polypropylene


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(PP) based materials. In recent papers, we presented and discussed a High Throughput Experimentation (HTE) approach to such systems, for the part aimed to determine the relationships between system formulation and catalyst stereoselectivity.1–3 The question of

regioselectivity, that hierarchically might have been expected to come first in the investigation, was temporarily put on hold because all said catalysts are almost fully regioselective (in typical cases >99.8%) in favor of 1,2 (‘primary’) propene insertion.4,5 The occasional 2,1 (‘secondary’) regiodefects are not detected in routine

13C

NMR spectra of ZN-PP samples,

and can be neglected in microstructural assessments as long as the physical properties of such samples are concerned. Historically, the identification of a 1,2 insertion regiochemistry as the dominant one was based on the NMR elucidation of the polymer chain ends.6,7 1H NMR spectra of PP samples obtained in the absence of H2, which is the industrially used chain transfer agent to modulate average polymer molecular weight (MW), show vinylidene chain ends (CH2=C(CH3)(P), P = Polymeryl), which can be traced to -H elimination from a 1,2 last-inserted monomeric unit. Trans-alkylation of growing chains with

13C-enriched

AlMe3, in turn, led to the formation of



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(P)CH2-CH(CH3)(13CH3) end groups, which is consistent with 1,2 monomer insertion into an initial Ti-13CH3 bond.7–9 In the 1990s, indirect methods for the quantification of ZN catalyst regioselectivity were introduced, based on propene (a) hydro-oligomerization or (b) copolymerization with [1-13C]ethene.10–15 The common basis for such methods is the fact that a growing PP chain with a 2,1 last-inserted unit is poorly reactive towards propene insertion, because the -methyl branch creates severe steric hindrance at the Ti center, that therefore features a ‘dormant’ character (with reference to Scheme 1, kspksp ; kpEksE>>ksp). Therefore, both molecules have the ability to ‘wake-up’ the dormant centers, which explains their strong activating effect on these catalysts.


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Scheme 1. Regiochemistry of propene insertion into Ti-P bonds, (P = Polymeryl, n = number of monomeric units), and reactivity of H2 and ethene with the various possible Ti-P moieties.

As can be seen from Scheme 1, the reaction products of both H2 and ethene with dormant chains are idiosyncratic, and easily recognizable by means of

13C

NMR (and by capillary

GC(/MS) too for hydro-oligomeric products11). The use of [1-13C]-ethene is especially convenient for

13C

NMR quantifications of the mole fraction of 2,1 units (xs), but relatively

expensive and cumbersome as well.13–15 Somewhat unexpectedly, all aforementioned studies agreed that the simple MgCl2/TiCl4AlEt3 (TEA) catalyst system, that may be seen as the archetype of all formulations including electron donors, is only moderately regioselective. The average value of xs in the (poorly stereoregular) polymer produced by this system turned out to be around 1.0%, which is



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similar to (or even higher than) what is found for metallocene-made PP. The reason why head-to-head/tail-to-tail enchainments were not revealed before by routine

13C

NMR analyses

is that they mainly concentrate in poorly stereoregular monomer sequences15, and the multiplicity of stereochemical environments results into an extensive splitting and broadening of the corresponding

13C

NMR resonances, which raises the threshold for their detectability.15

Catalysts modified with ID’s or ED’s, on the other hand, are indeed highly regioselective, with

xs values lower by roughly one order of magnitude.14 The formation of dormant centers is of huge technological relevance, not only for their impact on catalyst productivity, but also because they determine the propensity of a given catalyst to undergo hydrogenolysis.14,16–19 As was noted above, all industrial processes for PP production make use of H2 as a chain transfer agent to regulate the average MW of the polymer. The ability of H2 to cleave dormant chains (Scheme 1) makes the latter the main contributors of saturated chain ends; therefore, measuring the amount of dormant centers and how prone they are to hydrogenolysis is very important for application. It is worthy to note at this point that when the propene hydro-oligomerization method10,11 was introduced the signal-to-noise (S/N) ratio of routine

13C

NMR spectrometers was too low 6

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for chain end analyses on PP samples with number-average degree of polymerization approaching the range of commercial ones (Pn > 5102, indicatively), and therefore oligomeric samples had to be investigated. Whereas the results were validated by benchmarking with 13C-enriched

high polymers, the risk of flawed conclusions when looking at the low-end tail of

the overall molecular weight distribution (MWD) in a polymer produced with a multi-sited catalyst system (as typical ZN ones are) remains non-negligible. The introduction of NMR spectrometers equipped with high-temperature cryoprobes represented a breakthrough in polyolefin analysis.20,21 As a matter of fact, due to the 10-fold increase in S/N ratio compared with standard probes (resulting into a 100-fold reduction of the experiment time to reach a desired S/N value), features like the chain end groups and the regioirregular placements in commercial PP samples at natural

13C

abundance became

accessible, albeit with experiment times that are too long for high-throughput operation. One such spectrometer was integrated off-line in the HTE workflow used in our ZN project2,3, and exploited to implement a method enabling rapid and accurate quantifications of regioregularity on ZN PP with 13C NMR experiment times short enough for a HTE approach. In this paper we



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introduce and discuss said method, which also provides semi-quantitative information on catalyst dormancy and ‘hydrogen response’.

EXPERIMENTAL SECTION All precatalysts and the Diisobutyldimethoxysilane ED used in this study were kindly donated by SABIC Europe (Geleen, Netherlands). Neat AlEt3 was purchased from Chemtura. Hydrocarbon solvents and diluents (Romil, HPLC-grade) were purified in an MBraun SPS-5 unit. Propene (2.6) and H2 (6.0) were purchased from Rivoira; the former was further purified by flowing it through a column containing activated A4 molecular sieves and an activated Cu catalyst (BASF R0-11G). All propene polymerization experiments were carried out in a robotically operated Freeslate (former Symyx) Parallel Pressure Reactor (PPR) setup, featuring 48 reaction cells with individual on-line reading/control of pressure and temperature, arrayed in six 8-cell modules integrally contained in a glovebox environment. The setup has been extensively described before.2 What follows is the polymerization protocol.


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Prior to the execution of a library of experiments, the PPR modules undergo ‘bake-andpurge’ cycles overnight (8 h at 90-140°C with intermittent dry N2 flow), to remove any contaminants and left-overs from previous experiments. After cooling to glove-box temperature, the module stir tops are taken off, and the 48 cells are fitted with disposable 10 mL glass inserts (pre-weighed in a Mettler-Toledo Bohdan Balance Automator) and polyether ether ketone (PEEK) stir paddles. The stir tops are then set back in place, and the cells are loaded with the appropriate amounts of heptane diluent, AlEt3 (TEA) as a scavenger, and 25 psi (1.7 bar) or 45 psi (3.1 bar) of H2, thermostated at 70°C, and brought to 80 psi (5.5 bar) with propene (3.8 bar and 2.4 bar). At this point, the catalyst injection sequence is started; aliquots of (a) a heptane ‘chaser’, (b) a heptane solution of TEA, alone or complexed with an alkoxysilane ED ([Al]/[Ti] = 160, [Si]/[Al] = 0.10), (c) a slurry of the precatalyst and (d) a heptane ‘buffer’, all separated by nitrogen gaps, are uploaded into the slurry needle and subsequently injected into the cell of destination, thus starting the reaction. This is left to proceed under stirring (800 rpm) at constant temperature and pressure by feeding propene on demand for 30 minutes, and quenched by over-pressurizing the cell with 50 psi (3.4 bar) of dry air (preferred over other possible catalyst quenchers because in case of cell or quench 9 ACS Paragon Plus Environment


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line leakage oxygen is promptly detected by the dedicated glove-box sensor). Once all cells have been quenched, the modules are cooled down and vented, the stir-tops are removed, and the glass inserts containing the reaction phases are taken out and transferred to a centrifugal evaporator (Genevac EZ-2 Plus), where all volatiles are distilled out and the polymers are thoroughly dried overnight. Reaction yields are double-checked against on-line monomer conversion measurements by robotically weighing the dry polymers while still in the reaction vials, subtracting the pre-recorded tare. Polymer aliquots are then sent to the characterizations. High-temperature Gel Permeation Chromatography (GPC) curves were recorded with a Freeslate Rapid-GPC setup, equipped with a set of two mixed-bed Agilent PLgel 10 μm columns and a PolymerChar IR4 detector. Typically, 1-4 mg of polymer were dissolved in proper volumes of ortho-dichlorobenzene (ODCB) containing 0.40 mg mL−1 4-methyl-2,6-ditert-butyl-phenol (butylhydroxy-toluene, BHT) as a stabilizer in order to obtain solutions at a concentration of 0.5-1.0 mg mL−1. Calibration was carried out with the universal method, using 10 monodisperse polystyrene samples (Mn between 1.3 and 3700 kDa). Before and


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after each campaign, samples from a known PP batch produced with an ansa-zirconocene catalyst were analyzed for a consistency check. 13C

NMR spectra were recorded with a 100 MHz Bruker Avance III 400 spectrometer

equipped with a 5 mm OD high temperature cryoprobe, and a robotic sample changer with preheated carousel (24 positions). The samples (∼30 mg) were dissolved at 120 °C in tetrachloroethane-1,2-d2 (0.7 mL) added with 0.40 mg mL−1 BHT and loaded in the carousel maintained at the same temperature. The spectra were taken sequentially with automated tuning, matching, and shimming. Operating conditions were as follows: 45° pulse; acquisition time, 2.7 s; relaxation delay, 5.0 s; 1-10 K transients. Broad-band proton decoupling was achieved with a modified WALTZ16 sequence (BI_WALTZ16_32 by Bruker). Spectral simulation was carried out using the SHAPE2004 software package (M. Vacatello, Federico II University of Naples, Italy).

RESULTS AND DISCUSSION The proposed method is closely related to propene hydro-oligomerization.11 As a matter of fact, the application protocol consists of the very same steps, namely: (i) prepare a number of 11 ACS Paragon Plus Environment


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H2-terminated PP samples at variable p(H2)/p(C3H6) ratios; (ii) measure the mole ratio

QpH/QsH between the mole amounts of isoButyl and nButyl chain ends in said samples; and (iii) build a correlation plot between the QpH/QsH ratio and [(1+QsH/QpH)Pn]-1. Indeed, it was demonstrated that, if all chain transfer processes other that hydrogenolysis can be neglected (vide infra, though), the following relationship holds:11

QpH/QsH = (ksp/kps)(kpH/ksH) + (kpp/kps)[(1+QsH/QpH) Pn]-1

(Eq1)

The derivative of the straight line through the experimental data points coincides with

kpp/kps, from which one can measure xs(kpp/kps)-1. The intercept at [(1+QsH/QpH)Pn]-1 = 0 yields (ksp/kps)(kpH/ksH)  ksp/kps11; from the latter ratio, one can estimate x*(d)(1 + ksp/kps)-1.11 On the other hand, a first important element of novelty of the method is that, due to the very high sensitivity of the used NMR spectrometer, it is applied to polymers with Pn values close to the commercial range (as a matter of fact, the definition of ‘hydro-oligomerization’ does not hold anymore). As was already noted in the introduction, this lowers the risk of looking at products formed at a ‘tail’ of catalytic species that are not representative of the overall population. Moreover, it makes it possible to fractionate the products mainly based on stereoregularity rather than on molar mass, as we shall see at a later stage. One last notable 12 ACS Paragon Plus Environment

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point is that the polymers are prepared in a HTE platform (Freeslate PPR), and with a proper Design of Experiments (DoE) the protocol can be reduced to

13C

NMR analyses of single H2-

terminated PP samples; this opens the door to the implementation of robust HTE databases of regioselectivity and hydrogen response as a function of catalyst system formulation. For the present study, three catalyst systems were selected to implement and validate the method,

namely:

MgCl2/TiCl4

(Cat1)-TEA

(short

notation

CatSys1);

MgCl2/TiCl4/Dibutylphthalate (Cat2)-TEA/ Diisobutyldimethoxysilane (short notation CatSys2); and MgCl2/TiCl4/2,2-Disobutyl-1,3-dimethoxypropane (C3)-TEA (short notation CatSys3). A 5module PPR library of 40 polymerization experiments was designed as is shown in Table 1. The results, including Rapid-GPC and

13C

NMR characterizations of the products, are

reported in Table 2 and Figure 1.



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Table 1. DoE of the propene polymerization library with the three investigated catalyst systems (see text).

p(C3H6), psi

65

65

55

45

25

p(H2), psi

0

15

25

35

45

Cell

Module 1

Module 2

Module 3

Module 4

Module 5

A B

CatSys1 (all experiments in duplicate)

C D

CatSys2 (all experiments in triplicate)

E F G

CatSys3 (all experiments in triplicate)

H


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Table 2. Main results of propene polymerization with the three investigated catalyst systems at 70°C (see text).

Sample p(H2)/p(C3H6), Rp

xnPr,

xisoBu, xnBu, 10-

#

psi/psi

(a)

%

%

1-1

0/65

4.4

1-2

15/65 (= 0.23) 14

1.1

0.51

0.59

0.91

1-3

25/55 (= 0.45) 12

1.1

0.64

0.57

1-4

25/55 (= 0.45) 12

1.3

0.75

1-5

35/45 (= 0.78) 11

1.5

1-6

45/35 (= 1.29) 5.6

1.6

2-1

0/65

21

2-2

15/65

51

0.27

0.17

0.10

3.7

CatSys2 2-3

25/55

43

0.34

0.25

0.10

2-4

35/45

41

0.50

0.40

2-5

45/35

32

0.56

0.46

3-1

0/65

29

3-2

15/65

66

0.395 0.274 0.14

2.5

CatSys3 3-3

25/55

64

0.505 0.353 0.14

3-4

35/45

46

3-5

45/35

46

System

CatSys1

(a) Kg(PP)

%

2P (b) n

QpH/QsH

Mn(c), KDa

Mw/Mn

11

7.7

0.9

4

7.2

0.86

1.1

4

4.8

0.63

0.74

1.2

4

4.7

1.0

0.69

0.62

1.5

3

4.6

1.2

0.69

0.57

1.7

3

5.0

31

9.7

1.7

14

8.2

2.9

2.5

12

7.3

0.10

2.0

4.0

12

5.0

0.10

1.8

4.6

9

5.4

60

6.2

2.0

14

4.4

2.0

2.5

10

4.2

0.623 0.511 0.14

1.6

3.7

7

4.0

0.912 0.750 0.14

1.1

5.4

6

3.8

g(Ti) h-1 bar(C3H6)-1. (b) Measured by 13C NMR. (c) Measured by Rapid-GPC.



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Figure 1. Experimental plot of QpH/QsH vs [(1+ QsH/QpH)Pn] for the data in Table 2.

For each catalyst system, Eq1 was well-verified (Figure 1). The best-fit values of kpp/kps and

ksp/kps, and the corresponding estimates of xs and x*(d), are collected in Table 3. Table 3. Best-fit values of kpp/kps and ksp/kps and corresponding estimated values of xs and

x*(d) for the studied catalyst systems.(a)

Catalyst system

(a)

kpp/kps

xs ( kps/kpp), %

ksp/kps

x*(d), %

CatSys1

123±9

0.81±0.06

0.25±0.07

85

CatSys2

1000±12

0.10

0

 100

CatSys3

715±16

0.14

0

 100

Correlation coefficients of the linear best-fit: 0.986 (CatSys1), 0.999 (CatSys2), 0.992

(CatSys3). 16 ACS Paragon Plus Environment

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In line with the conclusions of previous studies,14,15 system CatSys1 was found to be much less regioselective (xs=0.81%) and less dormant (x*(d)85%) than CatSys2 (xs=0.10%;

x*(d)100%) and CatSys3 (xs=0.14%; x*(d)100%). As noted before, the extrapolated values of x*(d) are based on the assumption that -bond metathesis of Ti-P bonds with H2 is the only pathway of chain transfer, which actually is not the case (intramolecular and monomerassisted β-H elimination, as well as trans-alkylation with the Al-alkyl cocatalyst, are also viable); therefore, they are unquestionably over-estimations. At odds with hydro-oligomers, the H2-terminated polymers can be fractionated based on their stereoregularity, because the average molar masses are high enough not to impact appreciably on the crystallization ability, and therefore on the solubility. As a result, plots like those in Figure 1 can also be built for individual fractions. As a matter of fact, the polymer samples of Table 2 were extracted with boiling pentane, so as to dissolve the fraction normally referred to as ‘atactic’, and the characterizations previously described for the raw samples were repeated on the boiling-pentane-insoluble (‘isotactic’) fraction. The results are



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reported in Table 4, and those of their elaborations in terms of Eq1 are in Table 5 and Figure 2. Comparison with the homologous data in Table 3 and Figure 1 demonstrates that the catalytic species with higher stereoselectivity are also those with higher regioselectivity and a more dormant character. In Table 5, moreover, we reported the values of xs directly measured by

13C

NMR from spectra recorded at long experiment time (24 h accumulation) for the

‘isotactic’ fractions of PP samples prepared at p(H2) = 0 (Table 2); the agreement with the estimates based on kpp/kps is excellent. Independent support to the above conclusion was reported before. In particular, a Quenched-Flow study of propene homopolymerization in the presence of CatSys2 (no added H2) demonstrated that the polymer produced in the very early stages of the reaction, i.e. before active site dormancy can develop, was practically stereo-perfect.22 As soon as dormant sites started accumulating, both catalyst productivity and stereoselectivity decayed strongly, and only the addition of H2 brought the system back to an industrially acceptable performance.


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Table 4. Main characterization results for the ‘isotactic’ fractions of the PP samples in Table 2.

System

Sample,

I.I.(a),

xnPr,

xisoBu,

xnBu,

#

%

%

%

%

1-1 CatSys1

1-5

40

1-6 2-1 CatSys2

2-4

96.5

2-5 3-1

3-4 3-5 (a)

0.15

0.15

3.4

1.0

0.44

0.29

0.16

2.3

1.9

0.52

0.35

0.15

1.9

2.4

0.65

0.46

0.16

1.6

3.0

0.17

0.12

0.06

5.7

2.0

0.23

0.18

0.06

4.3

3.0

0.32

0.27

0.06

3.1

4.5

0.35

0.29

0.06

2.9

4.8

0.21

0.14

0.07

4.8

2.0

0.31

0.24

0.07

3.2

3.4

0.34

0.29

0.07

2.9

4.1

0.41

0.37

0.07

2.3

5.3

96.0

3-2 CatSys3 3-3

0.30

98.4

2-2 2-3

QpH/QsH

44

1-2 1-3

10-2Pn

92.0

Weight-% of the boiling-pentane-insoluble fraction



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Figure 2. Experimental plot of QpH/QsH vs [(1+QsH/QpH)Pn] for the data in Table 4.

Table 5. Best-fit values of kpp/kps and ksp/kps and estimated values of xs for the ‘isotactic’ fractions of the PP samples in Table 2.(a) In the last column, xs values measured directly by 13C

NMR at long accumulation time were added for validation purposes.

Catalyst

xs (13C NMR),

%

%

0.1±0.1

0.16

0.14

1.7103

0

0.06

0.05

1.4103

0

0.07

0.07

ksp/kps

CatSys1

610±30

CatSys2 CatSys3

system

(a)

xs ( kps/kpp),

kpp/kps

Correlation coefficients of the linear best-fit: 0.999 (CatSys1), 0.999 (CatSys2), 0.996

(CatSys3).


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In Figure 3 the results of the fractions of

isoButyls

13C

NMR analysis of the terminal chain ends, that is the mole

(xisoBu) and nButyls (xnBu), as a function of the p(H2)/p(C3H6) ratio for the

PP samples of Table 2 are put in graphical form. In the case of CatSys1, featuring a comparatively low level of dormancy, xnBu followed an asymptotic trend, with the upper limit coinciding with xs for p(H2)/p(C3H6) >0.75. For the highly dormant CatSys2 and CatSys3, on the other hand, the plateau values of xnBu was already attained at the lowest p(H2)/p(C3H6) ratio (=0.23) used in this study. The above sets the basis for HTE determinations of xs; indeed, 13C NMR measurements of xnBu on single H2-terminated PP samples yield xs provided that the used p(H2)/p(C3H6) ratio is high enough to result into xnBu = xs. Actually we recommend to prepare and analyze PP samples at two p(H2)/p(C3H6) ratios (e.g., R(1) =

p(H2)/p(C3H6) = 0.20 and R(2) = p(H2)/p(C3H6) 1) for each given catalyst system, and check that the two xnBu values measured by

13C

NMR (xnBu(1) and xnBu(2), respectively) coincide

within the experimental error. In case they do not, the value of xnBu(2) can be taken as xs, and the xnBu(2)/xnBu(1) ratio as a semi-quantitative descriptor of catalyst dormancy (the higher the ratio, the lower the dormancy).



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In general and on inspection of the plots in Figure 3, one should realize that for ZN PP the dependence of average MW on p(H2) at a given p(C3H6) is heavily affected by the asymptotic decrease of xs, and that the empirical relationship of MW  p(H2)0.5 at practical values of p(H2) 17,23

is merely a rough approximation of a more complicated kinetic law.

CatSys1

Figure 3.

13C

CatSys2

CatSys3

NMR values of xisoBu () and xnBu (■) vs p(H2)/p(C3H6) for the PP samples of

Table 2.


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CONCLUSIONS In the previous sections we have seen that regioselectivity is a key property of ZN catalyst systems for the industrial production of PP, because it dictates the so-called ‘hydrogen response’, that is the extent to which the average MW of the polymers made with a given catalyst system can be modulated by means of H2 added as a chain transfer agent. The reason is that growing PP chains with a regioirregular 2,1 last-inserted unit have a ‘dormant’ character in chain propagation, whereas their chain transfer via hydrogenolysis is fast. On the other hand, quantitative estimates of regioselectivity for these catalysts remain rare, because measuring the very low fraction of 2,1 units (xs) in PP samples is exceedingly difficult with conventional methods. In this paper, we introduced a simple HTE method for fast and accurate determinations of this elusive quantity. For each given catalyst system, the method requires to measure by

13C

NMR the mole fraction of nButyl chain ends (xnBu) in one single PP sample prepared at a

p(H2)/p(C3H6) ratio high enough to result into the complete hydrogenolysis of the dormant chain ends, so that xnBu  xs. In typical cases this condition is matched for p(H2)/p(C3H6) >0.2; verification on two samples prepared at different p(H2)/p(C3H6) ratios (e.g., 0.2 and >1) is 23 ACS Paragon Plus Environment


Page 24 of 31

recommended. In case the thus measured 13C NMR values of xnBu do not coincide, the one at higher p(H2)/p(C3H6) (namely, xnBu(2)) can be taken safely as xs, and the xnBu(2)/xnBu(1) ratio represents a semi-quantitative descriptor of catalyst dormancy (the higher the ratio, the lower the dormancy). Application of the described protocol to a vast set of industrial catalysts for QSAR studies will be reported in the near future.


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ASSOCIATED CONTENT

Supporting Information. 13CNMR spectra of representative PP samples.

AUTHOR INFORMATION

Corresponding Author *email: [email protected]

Present Addresses

† Leibniz-Institut für Polymerforschung Dresden e.V. - Analytical Department Polymer Separation Group, Hohe Str. 6, D-01069 Dresden, Germany.

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ‡These authors contributed equally.



Page 26 of 31

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(2) Busico, V.; Cipullo, R.; Mingione, A.; Rongo, L. Accelerating the Research Approach to Ziegler–Natta Catalysts. Ind. Eng. Chem. Res. 2016, 55, 2686.

(3) Vittoria, A.; Meppelder, A.; Friederichs, N.; Busico, V.; Cipullo, R. Demystifying ZieglerNatta Catalysts: The Origin of Stereoselectivity. ACS Catal. 2017, 7, 4509.

(4) Cecchin, G.; Morini, G.; Piemontesi, F. Ziegler‐Natta Catalysts. In Kirk-Othmer

Encyclopedia of Chemical Technology; Seidel, A., Ed.; John Wiley & Sons, Inc.: Hoboken, NJ, 2007; pp 502–554.

(5) Pasquini, N. Polypropylene Handbook, 2nd Ed.; Hanser Publisher: Munich, 2005.

(6) Busico, V.; Cipullo, R. Microstructure of Polypropylene. Prog. Polym. Sci. 2001, 26, 443.


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(7) Zambelli, A.; Grassi, A.; Longo, P. Polymerization of A-Olefins: End Groups and Reaction Mechanism. Polym. Sci. 1991, 1, 214.

(8) Zambelli, A.; Sacchi, M. C.; Locatelli, P.; Zannoni, G. Isotactic Polymerization of αOlefins: Stereoregulation for Different Reactive Chain Ends. Macromolecules 1982, 15, 211.

(9) Zambelli, A.; Locatelli, P.; Sacchi, M. C.; Tritto, I. Isotactic Polymerization of Propene: Stereoregularity of the Insertion of the First Monomer Unit as a Fingerprint of the Catalytic Active Site. Macromolecules 1982, 15, 831.

(10) Busico, V.; Cipullo, R.; Corradini, P. Hydrooligomerization of Propene: A “Fingerprint” of a Ziegler-Natta Catalyst, 1. Preliminary Results for MgCl2-Supported Systems. Die

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(11) Busico, V.; Cipullo, R.; Corradini, P. Ziegler-Natta Oligomerization of 1-Alkenes: A Catalyst’s “Fingerprint”, 1 Hydrooligomerization of Propene in the Presence of a Highly Isospecific MgCl2-Supported Catalyst. Makromol. Chem. 1993, 194, 1079.



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(12) Busico, V.; Cipullo, R.; Talarico, G.; Caporaso, L. Highly Regioselective TransitionMetal-Catalyzed 1-Alkene Polymerizations: A Simple Method for the Detection and Precise Determination of Regioirregular Monomer Enchainments. Macromolecules 1998, 31, 2387.

(13) Busico, V.; Cipullo, R.; Ronca, S. Propene/Ethene-[1-13C] Copolymerization as a Tool for Investigating Catalyst Regioselectivity. 1. Theory and Calibration. Macromolecules 2002,

35, 1537.

(14) Busico, V.; Chadwick, J. C.; Cipullo, R.; Ronca, S.; Talarico, G. Propene/Ethene-[113C]

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(15) Busico, V.; Cipullo, R.; Polzone, C.; Talarico, G.; Chadwick, J. C. Propene/Ethene-[113C]

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(16) Chadwick, J. C.; Morini, G.; Balbontin, G.; Mingoui, I.; Polyolefins, M.; Natta, C. R. G.; Donegani, P. Effects of Using a Diether As External Donor. System 1997, 1188, 1181.


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(17) Guastalla, G.; Giannini, U. The Influence of Hydrogen on the Polymerization of Propylene and Ethylene with an MgCl2 Supported Catalyst. Makromol. Chem., Rapid

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(18) Chadwick, J. C.; Van Kessel, G. M. M.; Sudmeijer, O. Regio‐ and Stereospecificity in Propene Polymerization with MgCl2 ‐supported Ziegler‐Natta Catalysts: Effects of Hydrogen and the External Donor. Macromol. Chem. Phys. 1995, 196, 1431.

(19) Chadwick, J. C.; Morini, G.; Albizzati, E.; Balbontin, G.; Mingozzi, I.; Cristofori, A.; Sudmeijer, O.; Van Kessel, G. M. M. Aspects of Hydrogen Activation in Propene Polymerization Using MgCl2/TiCl4/Diether Catalysts. Macromol. Chem. Phys. 1996, 197, 2501.

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(21) Zhou, Z.; Kümmerle, R.; Stevens, J. C.; Redwine, D.; He, Y.; Qiu, X.; Cong, R.; Klosin, J.; Montañez, N.; Roof, G.

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NMR of Polyolefins with a New High Temperature 10mm

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(23) See e.g.: Keii, T.; Suzuki, E.; Tamura, M.; Murata, M.; Doi, Y. Propene Polymerization with a Magnesium Chloride-Supported Ziegler Catalyst, 1. Principal Kinetics. Die Makromol.

Chemie 1982, 183, 2285.


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SYNOPSIS


High Throughput Experimentation Protocol for Quantitative

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