Mathematical Model and Advanced Control for Gas-phase Olefin Polymerization in Fluidized-bed Catalytic Reactors

In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.

A Sterically Hindered Zirconocene Complex (1,2-Ph_2C_5H_3)_2ZrCl_2:Synthesis,Structure and Properties as Olefin Polymerization Catalyst

An unbridged zirconocene complex bis(1,2-diphenylcyclopentadienyl)zirconium dichloride [(1,2-Ph2-C5H3)2ZrCl2] 1 has been synthesized and structurally characterized. When activated by MAO, 1 produces ultra-high molecular weight polyethylene with high melting transition temperature, as well as atactic oligopropylene with average molecular weight of ~1150 g mol-1.

NdCl_3/MgCl_2 BISUPPORTED CATALYST FOR OLEFIN POLYMERIZATION

The NdCl_3/MgCl_2 bisupported catalyst was prepared by using NdCl_3 ,MgCl_2, (CH_3)_2(CH_2)_2 OH and TiCl_4. It is shown that the structure of bisupported catalyst was different from those of either NdCl_3 or MgCl_2 single supported catalyst. A peculiar type of kinetic curve for ethylene polymerization was found.

Recent Progress on Transition Metal （Fe, Co, Ni, Ti and V） Complex Catalysts in Olefin Polymerization with High Thermal Stability

The design and synthesis of transition metal complexes with high thermal stability in olefin polymerization have become more and more important in order to meet the need of industrial application.This review focuses on the transition metal complex catalyst with high thermal stability containing different structures,including the backbone of bis（imino）pyridine,a-diimine and other types of ligands.Besides the catalytic activity,the influence of reaction temperature on the molecular weight and molecular weight distribution of the obtained polymer was also described.The plausible mechanism on the stability of catalysts at high temperature was proposed,which may give guidance to design catalyst with good thermal stability.

Benzosuberyl Substituents as a"Sandwich-like"Function in Olefin Polymerization Catalysis

For the rational design of metal catalyst in olefin polymerization catalysis,various strategies were applied to suppress the chain transfer by bulking up the axial positions of the metal center,among which the"sandwich"type turned out to be an eficient category in achieving high molecular weight polyolefin.In the a-dimine system,the"sandwich"type catalysts were built using the typical 8-aryl-naphthyI framework.In this contribution,by introducing the rotationally restrained benzosuberyl substituent into the ortho-position of N-aryl rings,a new class of "sandwich-like"a-diimine nickel catalysts was constructed and fully identified.The rotationally restrained benzosuberyl substituents played a"sandwich-like"function by capping the nickel center from two axial sites.Compared to the nickel catalyst Ni1 bearing freely rotated benzhydryl substituent,Ni2 featuring benzosubery|substituent enabled the increase(8 times)of polymer molecular weights from 8 kDa to 65 kDa in the polymerization of ethylene.By further increasing the steric bulk of another ortho-site of the N-aryl ring,the polymer molecular weight even reached an ultrahigh level of 833 kDa(Mw=1857 kDa)using the optimized Ni3.Notably,these nickel catalysts could also mediate the copolymerization of ethylene with methyl 10-undecenoate,with Ni3 giving the highest copolymer molecular weight(88 kDa)and the highest incorporation of comonmer(2.0 mol1%),along with high activity of up to 10^(5)g·mol^(-1)·h^(-1).

STUDY ON HIGHLY ACTIVE ZIEGLERNATTA CATALYSTS FOR POLYMERIZATION OF OLEFINS

In this paper, highly active Ziegler-Natta catalysts of MgCl_2 supported TiCl_4 for synthesis ofpolyolefins, using di-n-butyl phthalate (DNBP) as internal donor and diphenyl dimethoxyl silane(DPDMS) as external donor, have been prepared. The conditions controlling the treatment ofsupport were studied. The interactions of various components present in the catalysts and theirinfluences on catalytic performance were investigated. It is found that by using DNBP and DPDMSas internal and external donors together the polymer products with higher isotactic index can beobtained. Plausible structure model and mechanism were proposed.

Dual roles of trifluoroborate in nickel-catalyzed ethylene polymerization:Electronic perturbation and anchoring for heterogenization

Brookhart-typeα-diimine nickel and palladium catalysts have been extensively studied over the past several decades;however,the heterogenization of these metal complexes has received much less attention.In this contribution,we installed a trifluoroborate potassium substituent on anα-diimine framework.The ionic nature of trifluoroborate potassium endowed theα-diimine nickel complex with a strong affinity for the SiO_(2)support,while its electron-donating nature enhanced the catalyst stability and polyethylene molecular weight.In the presence of only 100 equiv.of Et2AlCl cocatalyst,the SiO_(2)-supported catalyst demonstrated significantly better performance than its homogeneous analog during ethylene polymerization,with extremely high activity(1.42–6.53×10^(7)g mol^(−1)h^(−1))and high thermal stability.The heterogeneous system led to the formation of high-molecular-weight polyethylenes(Mn 142,500–732,800 g/mol),narrow polydispersities(2.18–3.00),tunable branching densities(21–64 per 1000 carbon atoms),and great mechanical properties.Moreover,the efficient copolymerization of ethylene with comonomers such as methyl 10-undecenoate,6-chloro-1-hexene or 5-hexenylacetate was achieved.These superior properties enabled by the trifluoroborate potassium moiety may inspire its applications in other polymerization catalyst systems.

Asymmetric Cationic [P, O] Type Palladium Complexes in Olefin Homopolymerization and Copolymerization

Metal-catalyzed ethylene homopolymerization and ethylene-polar monomer copolymerization to produce new kinds of polyolefins with novel microstructures are of great interest. So far, there are some disadvantages for traditional transition metal catalyst systems. Therefore, it is critical to develop new catalysts or alternative strategies. In recent years, some cationic [P, O] palladium complexes have been demonstrated with the abilities to obtain oligomers and the high molecular weight polymers. Most importantly, these complexes showed high activity and generated polymers with specific microstructures when used for copolymerization of ethylene with industrially relevant polar monomers. This review summarizes several types of high performance cationic [P, O] palladium catalysts in ethylene oligomerization, ethylene homopolymerization and the copolymerization of ethylene with polar monomers Specially, the regulation of steric and electronic effects at specific sites of the metal complexes was focused.

Preparation of Bio-hydrogen and Bio-fuels from Lignocellulosic Biomass Pyrolysis-Oil

In recent years, production of engine fuels and energy from biomass has drawn much interest. In this work, we conducted a novel integrated process for the preparation of bio-hydrogen and bio-fuels using lignocellulosic biomass pyrolysis-oil （bio-oil）. The process includes （i） the production of bio-hydrogen or bio-syngas by the catalytic cracking of bio-oil, （ii） the adjustment of bio-syngas, and （iii） the production of bio-fuels by ole nic polymerization （OP） together with Fischer-Tropsch synthesis （FTS）. Under the optimal conditions, the yield of bio-hydrogen was 120.9 g H2/（kg bio-oil）. The yield of hydrocarbon bio-fuels reached 526.1 g/（kg bio-syngas） by the coupling of OP and FTS. The main reaction pathways （or chemical processes） were discussed based on the products observed and the catalyst property.

Horizontally and Vertically Concerted Steric Strategy inα-Diimine Nickel Promoted Ethylene(Co)Polymerization

Main observation and conclusion Steric bulk plays a significantly paramount role in late transition metal promoted olefin(co)polymerization in terms of polymer molecular weight and catalyst thermal stability.Numerous sterically encumbered nickel and palladium catalysts have been developed,but they are usually uni-directional.In this contribution,from a bi-directional side the distinctive horizontally and vertically concerted steric strategy was well-developed and applied toα-diimine nickel catalysts.In ethylene polymerization,the increase of vertically steric bulk(H,Ph,Biph)led to an enhanced polymer molecular weight,a slightly ascended branching density;likewise increasing horizontally steric bulk(Ph,Nap,Ant)further resulted in the increase of polymer molecular weight and branching density.As a result,in sharp contrast to Ni1(H)without steric bulk,Ni5(Ant)with horizontally and vertically concerted steric bulk was thermally stable,showed very high activities at a level of 107 g·mol–1·h^(–1),and produced polyethylenes with the highest molecular weight of 518.8×10^(4)g·mol^(-1)and the broader range of branching density from 2.4/1000C to 27.8/1000C.In the copolymerization of ethylene with methyl 10-undecenoate,Ni5(Ant)also provided the highest copolymer molecular weight but gave the lowest incorporation of co-monomer.This work sheds light on the steric effect on olefin(co)polymerization.

Photoresponsive α-Diimine Nickel Modulated Ethylene (Co)Polymerization

Beyond the single ligand electronic and/or steric modifications, external stimuli are a useful tool for modulating catalytic polymerization reactions. Light stands out from external stimuli, but the corresponding photoresponsive transition metal catalysts are significantly rare for olefin polymerization due to the difficult synthesis. In this contribution, in consideration of the key role of steric shielding on the axial sites, we installed four concerted azobenzene moieties into symmetrically terphenyl-based α-diimine Ni(II) complexes to prepare photoresponsive catalysts, which were applied to ethylene polymerization and copolymerization with polar monomer. Via the trans-cis isomerization of azobenzene-functionalized Ni(II) catalysts in dark or under UV light, catalytic activity, polymer molecular weight, branching density, incorporation of co-monomer, and even the ratio of branching pattern were significantly modulated in ethylene (co)polymerizations. This photo-controlled strategy behaved an opposite influence between ethylene polymerization and copolymerization, in terms of catalytic activity and polymer molecular weight. As a result, slightly branched ultrahigh molecular weight polyethylenes and high molecular weight functionalized polyethylenes were produced at ambient conditions.

Influence of Backbone and Axial Substituent of Catalyst onα-Imino-ketone Nickel Mediated Ethylene(Co)Polymerization

Theα-imino-ketone nickel catalyst is an emerging versatile platform that is easy to prepare and allows for the production of branched high molecular weight functionalized polyethylenes.However,study on this catalyst system is rare thus far.In this contribution,by introducing different backbones,flexible and rigid axial substituents into theα-imino-ketone framework,a family of cationic nickel catalysts were synthesized and fully characterized.Without the addition of any activator,systematic studies on ethylene polymerization and copolymerization with polar monomers were performed to explore the influence of both backbone and axial substituent on catalytic activity,polymer molecular weight,branching density and incorporation.In particular,owing to the unique semi-opening feature of theα-imino-ketone framework,the preferred nickel catalyst exhibited high activity of 175 kg·mol^(-1)·h^(-1)to produce functionalized polyethylene with molecular weight of 13.4 kg·mol^(-1)and comonomer incorporation of 2.9 mol%.

The Influence of Bridge Type on the Activity of Supported Metallocene Catalysts in Ethylene Polymerization

Ethylene polymerization was carried out by immobilization of rac-ethylenebis（1-indenyl）zirconium dichloride （Et（Ind）2ZrCl2） and rac-dimethylsilylbis（1-indenyl）zirconium dichloride （Me2Si（Ind）2ZrCl2） preactivated with methylaluminoxane （MAO） on calcinated silica at different temperatures. Polymerizations of ethylene were conducted at different temperatures to find the optimized polymerization temperature for maximum activity of the catalyst. The Me2Si bridge catalyst showed higher activity at the lower polymerization temperature compared to the Et bridge catalyst. The highest catalytic activities were obtained at temperatures about 50 ~C and 70 ~C for Me2Si（Ind）2ZrC1JMAO and Et（Ind）zZrCI2/MAO catalysts systems, respectively. Inductively coupled plasma-atomic emission spectroscopy results and polymerization activity results confirmed that the best temperature for calcinating silica was about 450 ℃ for both catalysts systems. The melting points of the produced polyethylene were about 130 ℃, which could be attributed to the linear structure of HDPE.

Direct Synthesis of Ultrahigh Molecular Weight Functionalized Isotactic Polypropylene

Ultrahigh molecular weight functionalized isotactic polypropylene(f-UHMW-iPP)through the direct copolymerization of propylene with polar monomers is highly desirable but has not been accessed thus far because it involves challenging regio-and stereochemistry along with usually reduced molecular weight.Herein,in contrast to the unsuccessful catalyst strategy,a polar monomer-assisted strategy is used to access the above material.The introduction of O-or S-functionalized long-chain polar olefins into the hafnium-catalyzed copolymerization of propylene(and bulkierα-olefins)significantly increases the copolymer molecular weight with a maximum observed increase of+488%.f-UHMW-iPP and functionalized isotactic poly(α-olefin)s(M_(w)>2000 kDa,[mmmm]:99%)are thus prepared at ambient conditions.The incorporation of 1 mol%of polar monomer improves the surface property and significantly increases the long-sought toughness(860%)of brittle iPP,without reducing the tensile strength(42 MPa)due to the key achievement of ultrahigh molecular weight.A discussion of the mechanism involved in the beneficial effects of incorporating the polar monomer is herein presented by an in-depth density functional theory calculation.

A disubstituted-norbornene-based comonomer strategy to address polar monomer problem

The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar groups towards Lewis acidic metal centers and the drastic reactivity differences of polar comonomers versus non-polar olefins,it is challenging to develop catalysts that provide the desired polymer molecular weight,comonomer incorporation,and activity.In this contribution,we tackle this issue from a comonomer perspective using 5,6-disubstituted norbornenes,which are highly versatile,easily accessible,inexpensive,and capable of introducing two functional groups in a single insertion.More importantly,they are only mildly poisoning due to the presence of long spacers between double bonds and polar groups,and are not prone to b-hydride elimination due to their cyclic structures.As strong pdonors,they can competitively bind to metal centers versus olefins.Indeed,phosphine-sulfonate palladium catalysts can catalyze the copolymerization of ethylene with 5,6-disubstituted norbornenes and simultaneously achieve a high polymerization activity,copolymer molecular weight,and comonomer incorporation.The practicality of this system was demonstrated by studying the properties of the resulting polymers,copolymerization in hydrocarbon solvents or in bulk,recovery/utilization of unreacted comonomer,molecular weight modulation,and large-scale synthesis.