Pop-up English-Chinese

Kinetic modeling of ethylene polymerization with Cr-V bimetallic catalyst

LIU Bao1 TIAN Zhou2 ZHAO Ning1 LIU Boping1

(1.State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai, China 200237)
(2.Key Laboratory of Advanced Control and Optimization for Chemical Processes, Ministry of Education, East China University of Science and Technology, Shanghai, China 200237)

【Abstract】Bimetallic catalyst has been a hot research topic as it can realize one-pot synthesis of polyethylene with bimodal molecular weight distribution (MWD). The kinetics of ethylene homopolymerization with a novel Cr-iV bimetallic catalyst and corresponding monometallic S-2 and iV catalysts were studied at various experimental conditions. The MWD deconvolution of polymers made by these catalysts showed interaction between Cr and V active centers in the Cr-iV bimetallic catalyst. The activity of Cr centers was reduced, while the activity of V centers was improved. The polymerization temperature almost did not change the mass fractions of polymers produced by two active centers. The simplified single-site kinetic model for ethylene homopolymerization was employed to describe the polymerization behaviors of Cr and V centers in Cr-iV bimetallic catalyst. The kinetic parameters of each active center were estimated by fitting the experimental results of polymerization rates with model prediction. Compared to monometallic catalyst, the Cr center in the Cr-iV catalyst had decreased chain propagation rate constant, which led to the reduction of polymerization activity, whereas the V center in the Cr-iV catalyst had decreased chain deactivation rate constant, which signified more stable and active V center.

【Keywords】 bimetallic catalyst; ethylene polymerization; kinetics; modeling;

【DOI】

【Funds】 National Natural Science Foundation of China (21404061, 21674036) Fundamental Research Funds for the Central Universities (222201714054)

Download this article

    References

    [1] MORENO J, GRIEKEN R V, CARRERO A, et al. Development of novel chromium oxide/metallocene hybrid catalysts for bimodal polyethylene [J]. Polymer., 2011, 52 (9): 1891–1899.

    [2] LI Y F, WU X M. The production process and development of catalyst for bimodal polyethylene [J]. Shanghai Chemical Industry, 2007, 32 (1): 27–32 (in Chinese).

    [3] ALI A, HAGERTY R, ONG S. Process for producing bimodal ethylene polymers in tandem reactors: EP0503791 [P]. 1992.

    [4] BOHM L L. High mileage Ziegler-catalysts: excellent tools for polyethylene production [J]. Macromol. Symp., 2001, 173 (1): 53–64.

    [5] SAMUELS S B, KAROL F J. Process for the production of polyethylene with a broad and/or bimodal molecular weight distribution: US4918038 [P]. 1990-04-17.

    [6] STRICKLEN P M. Process for producing polyolefins and polyolefin catalysts: US4939217 [P]. 1990-07-03.

    [7] ZHANG Z F, ZHANG L T, XIAO M W, et al. Development of single reactor bimodal polyethylene catalyst and its characterization methods [J]. Modern Chemistry Industry, 2013, 33 (2): 28–32 (in Chinese).

    [8] KIM J D, SOARES J B P, REMPEL G L. Synthesis of tailor-made polyethylene through the control of polymerization conditions using selectively combined metallocene catalysts in a supported system [J]. J. Polym. Sci., Part A: Polym. Chem., 1999, 37 (3): 331–339.

    [9] KIM J D, SOARES J B P, REMPEL G L. Use of hydrogen for the tailoring of the molecular weight distribution of polyethylene in a bimetallic supported metallocene catalyst system [J]. Macromol. Rapid Commun., 2015, 19 (4): 197–199.

    [10] KUREK A, XALTER R, ST RZEL M, et al. Silica nanofoam (NF) supported single- and dual-site catalysts for ethylene polymerization with morphology control and tailored bimodal molar mass distributions [J]. Macromolecules., 2013, 46 (23): 9197–9201.

    [11] MEHDIABADI S, CHOI Y, SOARES J B P. Synthesis of polyolefins with combined single-site catalysts [J]. Macromol. Symp., 2012, 313 (1): 8–18.

    [12] KUREK A, MARK S, ENDERS M, et al. Mesoporous silica supported multiple single-site catalysts and polyethylene reactor blends with tailor-made trimodal and ultra-broad molecular weight distributions [J]. Macromol. Rapid Commun., 2010, 31 (15): 1359–63.

    [13] KUKALYEKAR N N, RASTOGI S S, CHADWICK J J. Controlled synthesis of bimodal polyethylene using supported dual catalysts [J]. Polymer Preprints, 2007, 48 (1): 280–281.

    [14] KIM J D, SOARES J B P, REMPEL G L. Synthesis of tailor-made polyethylene through the control of polymerization conditions using selectively combined metallocene catalysts in a supported system [J]. J. Polym. Sci., Part A: Polym. Chem., 1999, 37 (3): 331–339.

    [15] AHMADI M, JAMJAH R, NEKOOMANESH M, et al. Ziegler-Natta/metallocene hybrid catalyst for ethylene polymerization [J]. Macromol. Reac. Eng., 2007, 1 (6): 604–610.

    [16] LOPEZ-LINARES F, BARRIOS A D A, ORTEGA H, et al. Modification of polyethylene polydispersity by blending a Ziegler-Natta catalyst with a group of IV-half metallocene or scorpionate complexes [J]. J. Mol. Catal. A: Chem., 2002, 179 (1): 87–92.

    [17] LOPEZ-LINARES F, BARRIOS A D, ORTEGA H, et al. Toward the bimodality of polyethylene, initiated with a mixture of a Ziegler-Natta and a metallocene/MAO catalyst system [J]. J. Mol. Catal. A: Chem., 2000, 159 (2): 269–272.

    [18] HAN S C, JIN S C, LEE W Y. Control of molecular weight distribution for polyethylene catalyzed over Ziegler-Natta/metallocene hybrid and mixed catalysts [J]. J. Mol. Catal. A: Chem., 2000, 159 (2): 203–213.

    [19] JIN S C, HAN S C, KO Y G, et al. Preparation of the Ziegler-Natta/metallocene hybrid catalysts on SiO2/MgCl2 bisupport and ethylene polymerization [J]. J. Mol. Catal. A: Chem., 1999, 144 (1): 61–69.

    [20] WU W Q, YANG Y R, QI D S, et al. Composite catalytic for producing polyethylene having wide molecular weight distribution: 101274968 [P]. 2008 (in Chinese).

    [21] HAN S C, CHOI Y H, LEE W Y. Characteristics of ethylene polymerization over Ziegler-Natta/metallocene catalysts: comparison between hybrid and mixed catalysts [J]. Catal. Today, 2000, 63 (2): 523–530.

    [22] ZHAO N, CHENG R, HE X, et al. Novel SiO2-supported silyl-chromate (Cr)/imido-vanadium (V) bimetallic catalysts producing polyethylene and ethylene/1-hexene copolymers with bimodal molecular-weight distribution [J]. Macromol. Chem. Phys., 2014, 215 (15): 1434–1445.

    [23] LIU B, TIAN Z, ZHAO N, et al. Peculiarities of ethylene polymerization kinetics with an imido-vanadium/silyl-chromate bimetallic catalyst: effect of polymerization conditions [J]. Ind. Eng. Chem. Res., 2017, 56 (21): 6164–6175.

    [24] SOARES J B P. Mathematical modelling of the microstructure of polyolefins made by coordination polymerization: a review [J]. Chem. Eng. Sci., 2001, 56 (13): 4131–4153.

    [25] OSTROVSKII N M, STOILJKOVIC D. Evaluation of the effect of reaction and mass transfer on the growth of polymer particles in olefin polymerization [J]. Theor. Found. Chem. Eng., 2011, 45 (1): 40–52.

    [26] SOGA K, YANAGIHARA H, LEE D H. Effect of monomer diffusion in the polymerization of olefins over Ziegler-Natta catalysts [J]. Die Makromolekulare Chemie, 2003, 190 (5): 995–1006.

    [27] FLOYD S, ANEN T H, TAYLOR T W, et al. Polymerization of olefins through heterogeneous catalysis (Ⅵ): Effect of particle heat and mass transfer on polymerization behavior and polymer properties [J]. J. Appl. Polym. Sci., 1987, 33 (4): 1021–1065.

    [28] KISSIN Y V. Active centers in Ziegler-Natta catalysts: formation kinetics and structure [J]. J. Catal., 2012, 292 (8): 188–200.

    [29] KISSIN Y V, MINK R I. Ethylene polymerization reactions with multicenter Ziegler-Natta catalysts-manipulation of active center distribution [J]. J. Polym. Sci., Part A: Polym. Chem., 2010, 48 (19): 4219–4229.

    [30] KISSIN Y. Kinetics of alkene polymerization reactions with transition metal catalysts [J]. Stud. Surf. Sci. Catal., 2007, 173 (7): 291–417.

    [31] VICKROY V V, SCHNEIDER H, ABBOTT R F. The separation of SEC curves of HDPE into flory distributions [J]. J. Appl. Polym. Sci., 1993, 50 (3): 551–554.

    [32] KISSIN Y V. Ethylene polymerization kinetics with heterogeneous Ziegler-Natta catalysts [J]. Macromol. Symp., 1993, 66 (1): 83–94.

    [33] SOARES J B P, HAMIELEC A E. Deconvolution of chain-length distributions of linear polymers made by multiple-site-type catalysts [J]. Polymer., 1995, 36 (11): 2257–2263.

    [34] SOARES J B P, MCKENNA T F. Polyolefin Reaction Engineering [M]. Weinheim: Wiley-VCH, 2012: 352

    [35] NETO A G M, FREITAS M F, NELE M, et al. Modeling ethylene/1-butene copolymerizations in industrial slurry reactors [J]. Ind. Eng. Chem. Res., 2005, 44 (8): 2697–2715.

This Article

ISSN:1671-1637

CN: 61-1369/U

Vol 20, No. 01, Pages 60-73

February 2020

Downloads:0

Share
Article Outline

Abstract

  • Introduction
  • 1 Experiment
  • 2 Establishment of kinetic model for ethylene homopolymerization
  • 3 Results and discussion
  • 4 Conclusions
  • References