A Study of Ziegler–Natta Propylene Polymerization Catalysts by Spectroscopic Methods

Ткаченко, О. П.; Кучеров, А. В.; Kustov, L. М.; Virkkunen, Ville; Leinonen, Timo; Denifl, Peter

doi:10.3390/ma10050496

Cited by 10 publications

(6 citation statements)

References 40 publications

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“…Steady-state DRIFTS spectra were acquired for H-BEA and 2 wt % Pd/BEA samples using a 1 h exposure of C 3 H 6 and O 2 at 80 °C (Figure ). The set of larger peaks at 2950, 2910, and 2850 cm –1 is associated with C–H stretches of the CH 2 group of adsorbed HC species, which are likely present as long-chain alkanes formed during C 3 H 6 coupling . The smaller peaks between 1100 and 1300 cm –1 are associated with bending of the CH 2 and CH 3 groups of these HCs (Figure b).…”

Section: Resultsmentioning

confidence: 97%

“…The set of larger peaks at 2950, 2910, and 2850 cm −1 is associated with C−H stretches of the CH 2 group of adsorbed HC species, which are likely present as long-chain alkanes formed during C 3 H 6 coupling. 40 The smaller peaks between 1100 and 1300 cm −1 are associated with bending of the CH 2 and CH 3 groups of these HCs (Figure 5b). Additionally, these peaks are evident in both Pd/BEA and H-BEA spectra, as well as in the presence of NO in the feed.…”

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 98%

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Coupled NO and C₃H₆ Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NO_x Trap

Malamis

Harold

Epling

2019

Ind. Eng. Chem. Res.

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Automotive emission control catalysts are not effective in eliminating CO, hydrocarbons (HCs), and NO x during engine cold start (below 200 °C). In this study, the effectiveness of coupled low-temperature NO x and C3H6 trapping and conversion on the model lean HC NO x trap (LHCNT) consisting of a washcoated Pd/BEA monolith was examined. Transient uptake and release experiments were conducted to obtain insight regarding competitive adsorption, release temperature, conversion activity, and water impact. NO and C3H6 uptake were found to be mutually inhibitive because of competition for adsorption on Brønsted acid sites. During desorption, the existence of multiple NO sorption sites was established. Although C3H6 inhibited NO adsorption on some of these sites, it delayed NO x desorption to higher temperatures. Furthermore, above 200 °C, Pd/BEA was able to catalyze the oxidation of stored HCs and exhibited NO x reduction activity. Addition of water inhibited both NO x and C3H6 uptake, but the inhibition was lessened through a high-temperature thermal pretreatment. Overall, Pd/BEA demonstrates a combination of inhibiting and promoting coupling effects during uptake and release and exhibits activity for both NO x reduction and C3H6 oxidation. The findings provide guidance for developing improved LHCNT materials.

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Section: Resultsmentioning

confidence: 97%

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 98%

Coupled NO and C₃H₆ Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NO_x Trap

Malamis

Harold

Epling

2019

Ind. Eng. Chem. Res.

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“…Recent years have seen more experimental studies that focus on structure–function relationships, for both traditional MgCl 2 -based ZNCs − and new MgCl 2 -derived support materials. − Still, many studies try to investigate the produced polymer in intricate ways to learn more about these elusive catalysts via an indirect approach . It is our belief that the final answers about the working mechanisms of ZNCs will primarily be found when studying the catalysts themselves …”

Section: Introductionmentioning

confidence: 99%

Probing Interactions between Electron Donors and the Support in MgCl₂-Supported Ziegler–Natta Catalysts

Blaakmeer

Antinucci

Eck³

et al. 2018

J. Phys. Chem. C

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Olefin polymerization using Ziegler–Natta catalysts (ZNCs) is an important industrial process. Despite this, fundamental insight into the inner working mechanisms of these catalysts remains scarce. Here, we focus on the low-γ nuclei 25Mg and 35Cl for an in-depth solid-state NMR and density functional theory (DFT) study of the catalyst’s MgCl2 support in binary adducts prepared by ball-milling. Besides the bare MgCl2 support and a MgCl2–TiCl4 adduct, samples containing donors that are part of the families of 2,2-dialkyl-1,3-dimethoxypropanes and phthalates used in fourth- and fifth-generation ZNCs are studied. DFT calculations indicate that the quadrupolar coupling parameters of the chlorines differ significantly between bulk and surface sites. As a result, the NMR visibility of the chlorine sites correlates with the particle size except for the adduct with 2,2-dimethyl-1,3-dimethoxypropane donor. The DFT calculations furthermore show that the surface sites are fairly insensitive to binding of different donor molecules, making it difficult to identify specific binding motives. The surface sites with large 35Cl NMR line widths can be observed using high radio frequency field strengths. For the 2,2-dimethyl-1,3-dimethoxypropane donor, we observe additional surface sites with intermediately high quadrupolar couplings, suggesting a different surface structure for this particular adduct compared to the other systems. For 25Mg, pronounced effects of donor binding on the quadrupole interaction parameters are observed, both computationally and experimentally. Again the adduct with the 2,2-dimethyl-1,3-dimethoxypropane donor shows a different behavior of the surface sites compared to the other adducts, which display more asymmetric coordinations of the surface Mg sites. Identifying specific binding motives by comparing 25Mg NMR results to DFT calculations also proves to be difficult, however. This is attributed to the existence of many defect structures caused by the ball-milling process. The existence of such defect structures both at the surface and in the interior of the MgCl2 particles is corroborated by NMR relaxation studies. Finally, we performed heteronuclear correlation experiments, which reveal interactions between the support and Mg–OH surface groups, but do not provide indications for donor–surface interactions.

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“…DRIFT spectroscopy was employed to trace the structural evolution during the synthesis procedure of the POSSmodified catalyst. 28 The DRIFT spectra of the intermediates and POSS-modified catalyst mentioned above are displayed in Figure 2a each reaction step, the ν(OH) region (4000−3200 cm −1 ) and ν(CH) region (3200−2800 cm −1 ) are highlighted in Figure 2b,c, respectively. For bare silica, the single sharp peak at 3746 cm −1 is characteristic of isolated silanol groups, 27 which is negligible after treating with TEA.…”

Section: Resultsmentioning

confidence: 99%

Efficient Synthesis of Low-Polydispersity UHMWPE by Elevating Active Sites on Anchored POSS Molecules

Liang

Chen

Ren

et al. 2020

Ind. Eng. Chem. Res.

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Ultrahigh-molecular-weight polyethylene (UHMWPE) with a low polydispersity exhibits excellently physical and mechanical properties. In this work, a polyhedral oligomeric silsesquioxane (POSS)-modified Ziegler−Natta catalyst has been explored to synthesize the UHMWPE with a narrow molecular weight distribution. Diffuse reflection infrared spectroscopy combined with CO as the molecular probe, X-ray photoelectron spectroscopy, and diffuse reflectance UV−vis spectroscopy are employed to trace the evolution of the catalyst structure based on the investigation of vibrational and electronic properties of molecules. The results demonstrate that the chemically grafted POSS molecules are distributed evenly on the silica surface at the molecular level. The POSS can capture the MgTi compounds through protonation with the residual silanols, acting as a vertical support for active sites. The resulting active sites grafted on the POSS present much stronger Lewis acidity and were less heterogeneous (only tetra-coordinated Mg 2+ species) in comparison to the active sites directly grafted or absorbed on the silica surface. This less heterogeneity of active sites enables to synthesize the UHMWPE with a much narrow distribution, reducing the molecular weight distribution from 6.7 to 3.9.

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A Study of Ziegler–Natta Propylene Polymerization Catalysts by Spectroscopic Methods

Cited by 10 publications

References 40 publications

Coupled NO and C₃H₆ Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NO_x Trap

Coupled NO and C₃H₆ Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NO_x Trap

Probing Interactions between Electron Donors and the Support in MgCl₂-Supported Ziegler–Natta Catalysts

Efficient Synthesis of Low-Polydispersity UHMWPE by Elevating Active Sites on Anchored POSS Molecules

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A Study of Ziegler–Natta Propylene Polymerization Catalysts by Spectroscopic Methods

Cited by 10 publications

References 40 publications

Coupled NO and C3H6 Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NOx Trap

Coupled NO and C3H6 Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NOx Trap

Probing Interactions between Electron Donors and the Support in MgCl2-Supported Ziegler–Natta Catalysts

Efficient Synthesis of Low-Polydispersity UHMWPE by Elevating Active Sites on Anchored POSS Molecules

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Product

Resources

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Coupled NO and C₃H₆ Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NO_x Trap

Coupled NO and C₃H₆ Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NO_x Trap

Probing Interactions between Electron Donors and the Support in MgCl₂-Supported Ziegler–Natta Catalysts