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Featured researches published by Francesco Masi.


Journal of Molecular Catalysis A-chemical | 2003

Polymerization of 1,3-dienes with iron complexes based catalysts: Influence of the ligand on catalyst activity and stereospecificity

Giovanni Ricci; Daniele Morganti; Anna Sommazzi; Roberto Santi; Francesco Masi

Abstract Various iron dichloride complexes with aliphatic and aromatic bidentate amine ligands have been synthesized and used, in combination with aluminium-compounds (AlR3 or methylaluminoxane (MAO)), for the polymerization of 1,3-dienes. Catalyst activity, chemo- and stereoselectivity are strongly influenced by the type of ligand; systems based on iron complexes with aromatic bidentate amines (e.g. bypiridine or phenantroline), in particular, exhibit an extremely high activity, giving from butadiene a 1,2-syndiotactic polymer. These systems are also able to polymerize substituted butadienes (e.g. isoprene, (E)-1,3-pentadiene, 2,3-dimethyl-1,3-butadiene) giving polymers with different structure from the different monomers; these results have permitted to confirm some aspects of the polymerization mechanism previously proposed.


Macromolecular Rapid Communications | 1998

Ethylene polymerization catalyzed by metallocene/ methylaluminoxane systems : quantum-mechanical study on the role of olefin separated ion pairs (OSIP) in the polymerization mechanism

Roberto Fusco; Luca Longo; Antonio Proto; Francesco Masi; Fabio Garbassi

DFT (density-functional theory) calculations were performed to investigate the thermodynamics of formation of Olefin Separated Ion Pairs (OSIP) Cp2MtCH3+/C2H4/Cl2Al[O(AlMe3)AlHMe] (Cp = η5-C5H5, Mt = Ti, Zr, Me = CH3) from ethylene and Cp2MtMe · Cl2Al[O(AlMe3)AlHMe]2, a model of adduct produced by metallocence/methylaluminoxane (MAO) systems for olefin polymerization. The results account for the high cocatalytic activity of MAO and show that titanium complexes are potentially more active than zirconium homologues, as confirmed by low temperature polymerization tests.


Journal of Molecular Catalysis | 1989

Supported hafnium catalysts for ethylene polymerization

Francesco Masi; Stefano Malquori; Lia Barazzoni; Renzo Invernizzi; Angelina Altomare; Francesco Ciardelli

Abstract Hafnium polymerization catalysts supported on spray-dried magnesium chloride have been prepared by precipitation with alkylaluminium chlorides from paraffin solutions of hafnium(tetra-n-butanolate). These catalysts have been used for ethylene polymerization after activation with different aluminium alkyl derivatives such as tri(isobutyl) aluminium, triethylaluminium and diethylaluminium chloride. The influence of the polymerization conditions, i.e . hydrogen pressure, 1-butene content, temperature, cocatalyst and ethyl benzoate, on the specific activity, polymerization rate and molecular weight has been investigated. The behaviour of the Hf catalyst has been compared to that of similar systems based on titanium or zirconium. The results obtained suggest that the selection of appropriate transition metal derivatives provides the further possibility of tailoring the characteristics of polyethylene.


Journal of Organometallic Chemistry | 1991

Comparative behaviour of hafnium and titanium catalysts in copolymerization of α-olefins

Angelina Altomare; Roberto Solaro; Francesco Ciardelli; Lia Barazzoni; Francesco Menconi; Stefano Malquori; Francesco Masi

Abstract Supported hafnium and titanium catalysts were prepared under the same conditions starting from the corresponding tetrakisbutanolates, which were supported on MgCl2 by reaction of a suspension of Hf/Mg catalyst with aluminum alkyl chlorides. The systems were employed in the copolymerization of 1-hexene with 4-methyl-1-pentene. The extent of polymerization, as well as the copolymer composition, sequence distribution, stereoregularity, and molecular weight were evaluated. The hafnium catalysts gave higher molecular weights and better isotactic stereoregularity but displayed lower activity than the titanium catalysts, but the co-monomer distributions were similar for the two systems. These results are discussed in terms of the number and type of active sites.


Polymer | 1993

Effect of protic compounds on ethylene polymerization by HfTi supported catalysts

C. Ferrero; Francesco Masi; Francesco Menconi; Lia Barazzoni; A. Moalli; Angelina Altomare; Roberto Solaro; Francesco Ciardelli

Abstract The effect was investigated of the addition of different protic compounds, such as water, n-butanol, butanoic acid and methyl ethyl ketone, to triisobutylaluminium used as the cocatalyst for an HfTi bimetallic catalyst supported on magnesium dichloride (Ti1.0Hf1.3Mg2.0Al0.85Cl12.45) in the polymerization of ethylene. All the above compounds show a similar behaviour by decreasing catalyst activity, increasing polymer molecular weight and narrowing polymer molecular weight distribution. Minor differences are observed in the end-group unsaturations. An attempt has been made to correlate these effects to the interaction of hafnium and titanium sites with the reaction products from AlR3 and the different protic compounds.


Journal of Molecular Catalysis | 1993

Characterization of supported bimetallic catalysts for ethylene polymerization: The effect of external Lewis bases

Lia Barazzoni; Francesco Menconi; Cesare Ferrero; Angelo Moalli; Francesco Masi; Angelina Altomare; Roberto Solaro; Francesco Ciardelli

Abstract The homopolymerization of ethylene was investigated in the presence of a hafnium/titanium (1:1) catalyst supported on magnesium chloride and activated with triisobutylaluminum to which different Lewis bases (LB) were added in various molar ratios. All the investigated LB, i.e. dibutyl ether, butyl acetate, dibutyl phthalate, tetramethylpiperidine, tetraethoxysilane, and phenyltriethoxysilane, show a similar behaviour: polymer yield, molecular weight and molecular weight distribution decrease with increasing the LB:transition metal molar ratio. However, distinct features are observed when changing the nature of the LB, as well as its amount. As far as the polymer yield is concerned, dibutyl ether and tetramethylpiperidine show the lowest and the highest decreasing effect, respectively. Dibutyl ether has very little effect on molecular weight and molecular weight distribution. By contrast, silanes cause a remarkable decrease of molecular weight when molar ratios LB/(Ti + Hf) greater than 0.5 are used. Finally, tetramethylpiperidine gives strongly reduced molecular weight and molecular weight distribution when used at molar ratios appreciably lower than 0.5, while additional amounts do not have any further effect. These results are discussed in terms of possible selective interactions of different catalytic sites with the investigated LB.


Polymer | 1992

Distinct behaviour of Ti and Hf supported catalysts in the polymerization of different monoalkenes

Angelina Altomare; Roberto Solaro; Francesco Ciardelli; Lia Barazzoni; Francesco Menconi; Stefano Malquori; Francesco Masi

Abstract MgCl2 supported Ti and Hf catalysts were comparatively tested with respect to the polymerization of differently shaped monoalkenes. The ratio between the average polymerization rates of Ti and Hf catalysts during the first 120 min ( V Ti p V Hf p is 10 for ethylene, increases to 63 for propylene and returns to ∼ 12–20 for higher or bulkier monoalkenes, suggesting a distinct shape selectivity of active sites.


Coordination Chemistry Reviews | 2010

Well-defined transition metal complexes with phosphorus and nitrogen ligands for 1,3-dienes polymerization

Giovanni Ricci; Anna Sommazzi; Francesco Masi; Marco Ricci; Aldo Boglia; Giuseppe Leone


Archive | 1988

A catalyst component for polymerizing ethylene or copolymerizing ethylene with an alpha-olefin

Renzo Invernizzi; Angelo Moalli; Francesco Masi


Journal of Organometallic Chemistry | 2005

Synthesis, structure and butadiene polymerization behavior of CoCl2(PRxPh3 − x)2 (R = methyl, ethyl, propyl, allyl, isopropyl, cyclohexyl; x = 1, 2). Influence of the phosphorous ligand on polymerization stereoselectivity

Giovanni Ricci; Alessandra Forni; Aldo Boglia; Anna Sommazzi; Francesco Masi

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