Geraldo Crossetti | Universidade Federal do Pampa (original) (raw)
Papers by Geraldo Crossetti
Resumo: Cada vez mais as indústrias de produção de polímeros buscam métodos robustos para confirm... more Resumo: Cada vez mais as indústrias de produção de polímeros buscam métodos robustos para confirmar características desejadas achando as condições do processo que levem ao rendimento máximo do polímero. Os processos de polimerização estão sendo aperfeiçoados, colaborando para a obtenção de polímeros cada vez mais sofisticados e baratos. A modelagem do processo de polimerização contribui para isso, uma vez que permite reduzir os custos de desenvolvimento, além de possibilitar compreensão do processo industrial. Neste trabalho, aborda-se sobre modelos regressivos desenvolvidos para o processo de polimerização. Inicialmente, formula-se um problema de otimização com vínculo, onde a Massa (M) representa a função objetivo (definida como uma função polinomial quadrática), dependente das variáveis preditoras: temperatura (T), pressão (P), concentração de alumínio (Al) e da taxa concentração de alumínio/concentração de níquel (Al/Ni); e o peso molecular (PM), fixado em determinado valor, é a...
Polymer Engineering and Science, Sep 1, 2010
A ciência dos polímeros foi gerada em 1920 quando Staudinger postulou o conceito de cadeia polimé... more A ciência dos polímeros foi gerada em 1920 quando Staudinger postulou o conceito de cadeia polimérica. Desde então o interesse na modelagem matemática dos fenômenos associados aos polímeros tem-se desenvolvido com relativa amplitude segundo os períodos de crescimento ou de estabilidade da industria dos polímeros. Os modelos matemáticos para estudar a reação química envolvem equações algébricas e/ou diferenciais. Desta forma no processo de polimerização existem diversos enfoques para obter funções de modelagem, entre eles: * Modelos de regressão multivariada; *Métodos de otimização combinatória. Nosso alvo foi otimizar a atividade polimérica tomando como vínculo um peso molecular fixo (ver Fig 1), após a modelagem da duas funções esboçar a modelagem mediante a regressão de várias variáveis, considerando um p-level 1 apropriado (0,05). Foram trabalhados vários modelos de regressão com diversas variáveis preditoras, tentando empregar como função dependente o peso molecular no caso de o...
Ethylene and 10-undecen-1-ol Copolymerization with the Catalyst System DADNi(NCS) 2 /MAO . The ca... more Ethylene and 10-undecen-1-ol Copolymerization with the Catalyst System DADNi(NCS) 2 /MAO . The catalyst DADNi(NCS) 2 (DAD = (ArN=C(Me)-C(Me)=ArN); Ar = 2,6-C 6 H 3), activated by methylaluminoxane (MAO) was tested at 50°C and Al/Ni ratio: 200. The system was also supported on silica Grace 955. The catalyst system was active in ethylene and 10-undecen-1-ol copolymerization. The polar monomer was protected with IPRA or TIBA. The best activities were obtained at lower concentration of polar monomer and the incorporation increases with the increase of the polar monomer concentration. The quantification of branches by 13 C-NMR showed that all the polyethylenes were highly branched . Introdução Poliolefinas com grupos funcionais ao longo da cadeia principal são de grande interesse por suas propriedades(1). A copolimerização de olefinas com comonômeros polares, é, atualmente, um dos métodos mais interessantes para obter estes materiais, especialmente, quando se usa sistemas catalíticos com...
Este trabalho faz parte do estudo da cinética de polimerização dos sistemas catalíticos formados ... more Este trabalho faz parte do estudo da cinética de polimerização dos sistemas catalíticos formados pelos complexos diimínicos de níquel, ativados por metilaluminoxano na polimerização de eteno, caracterizando os produtos da polimerização e visando relacionar as propriedades finais dos polímeros com as condições do processo de polimerização. Os dados experimentais são modelados buscando estabelecer as condições ótimas de polimerização, e otimizando a atividade do sistema e as propriedades do material polimérico. A modelagem do processo de catalização dos polímeros apresenta diversos problemas que podem ser resolvidos parcialmente com diversos métodos matemáticos de análise. Desenvolver novos materiais poliméricos implica num grande número de testes e caracterizações para determinar quais as condições de processo necessárias para produzir um polímero com as características desejadas. O uso de modelos matemáticos que relacionam as características finais dos polímeros com as condições de ...
Acta Crystallographica Section C Crystal Structure Communications, 2001
In the title compound, [NiBr(2)(C(31)H(32)NP)], (I), the second reported example of a nickel-imin... more In the title compound, [NiBr(2)(C(31)H(32)NP)], (I), the second reported example of a nickel-iminophosphine N,P-chelate in which the Ni atom has tetrahedral coordination, the Ni coordination is distorted as a consequence of the N-Ni-P chelate bite angle of 91.07 (6) degrees compensated by the Br-Ni-Br angle of 126.385 (18) degrees. In (I) and its analogue, viz. dichloro[[2-(4-isobutyloxazol-2-yl)phenyl]diphenylphosphine-N,P]nickel(II), the Ni-N and Ni-P distances are greater and the N-Ni-P ligand bite angles smaller than those observed in a series of related complexes with square-planar nickel.
Polymer Engineering & Science, 2010
This article regards the ethylene polymerization catalyzed by a nickel catalyst and activated by ... more This article regards the ethylene polymerization catalyzed by a nickel catalyst and activated by ethylaluminum sesquichloride (EASC). The effects of the reaction conditions [polymerization temperature, cocatalyst (EASC) concentration, and ethylene concentration] on the average molecular weights of the final polymers and reaction yields were evaluated with the help of empirical statistical models. It is shown that reaction temperature and cocatalyst (EASC) concentration exert the most important effects on average molecular weights and catalyst activity. The polydispersities of the obtained polyethylenes are larger than the polydispersities of polyethylenes obtained with typical Brookhart catalysts. The analysis of polymer branching frequencies shows new types of short branching and significant amounts of long branches, which may explain the relatively large polydispersities of the obtained polymer samples.
Polymer Bulletin, 1998
Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and A... more Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and Al2O3 was investigated. Using catalysts based on MAO supported on silica, a highly isotactic polystyrene was obtained. Nevertheless, the Al2O3-supported catalyst can promote isospecific polymerization activated by common. alkyl aluminum compounds even by any prior support treatment with MAO.
Macromolecular Rapid Communications, 1997
... 1, show that the intensity of the reson-ance at 146.3 ppm, typical of the isotactic pentads43... more ... 1, show that the intensity of the reson-ance at 146.3 ppm, typical of the isotactic pentads435), varies with the type of MA 0 used and decreases in the order ... The crude polymers were fractionated by successive extractions with boiling acetone and methyl ethyl ketone (MEK). ...
Journal of Polymer Science Part A: Polymer Chemistry, 2004
A complete 13 C NMR characterization of a polymer synthesized with a new Ni-diimine complex [DADN... more A complete 13 C NMR characterization of a polymer synthesized with a new Ni-diimine complex [DADNi(NCS) 2 , where DAD ϭ 2,6-iPrOC 6 H 3 ONAC(Me)OC(Me)A NO2,6-iPrOC 6 H 3 ] activated by methylaluminoxane by homopolymerization of propylene is presented. The amorphous material was made up mainly of blocks of syndiotactic polypropylene and ethylene-propylene copolymer. Some degree of propylene inversion (Ͻ1.2 mol %) and of long isobutyl and 2-methyl hexyl branching (Ͻ1 mol %) were assigned and quantified.
Journal of Polymer Science Part A: Polymer Chemistry, 2008
The catalyst DADNi(NCS) 2 (DAD ¼ (ArN¼ ¼C(Me)À ÀC(Me)¼ ¼ArN); Ar ¼ 2,6-C 6 H 3 ), activated by me... more The catalyst DADNi(NCS) 2 (DAD ¼ (ArN¼ ¼C(Me)À ÀC(Me)¼ ¼ArN); Ar ¼ 2,6-C 6 H 3 ), activated by methylaluminoxane, was tested in ethylene polymerization at temperatures above 25 8C and variable Al/Ni ratio. The system was shown to be active even at 80 8C and when supported on silica. However, catalyst activity decreased. The catalyst system was also tested in ethylene and 10-undecen-1-ol copolymerization at different ethylene pressures. The best activities were obtained at low polar monomer concentration (0.017 mol/L), using triisopropylaluminum (Al-i-Pr 3 ) to protect the polar monomer. The incorporation of the comonomer increased with the increase of polar monomer concentration. According to 13 C NMR analyses, all the resulting polyethylenes were highly branched and the polar monomer incorporation decreased as ethylene pressure increased. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5199-5208, 2007
Applied Organometallic Chemistry, 2004
3), [Ar = 2,6-i Pr-C 6 H 3 ; dppe = 1,2-bis(diphenylphosphine)ethane] were synthesized and examin... more 3), [Ar = 2,6-i Pr-C 6 H 3 ; dppe = 1,2-bis(diphenylphosphine)ethane] were synthesized and examined for ethylene polymerization activated by methylaluminoxane (MAO). Their behavior was compared with those of the corresponding halide analogues [ArN C(Me)-C(Me) NAr]NiBr 2 (4), [Ph 2 PC 6 H 4 CH NAr]NiBr 2 (5), and (dppe)NiCl 2 (6). The diimines showed the highest polymerization activity. Replacement of the halide for the NCS pseudo halide affected the activity and decreased the molecular weight of the polymer formed. The highest molecular weights were obtained with the diimine complexes. Highly branched polyethylenes were obtained with the bulkier complexes 1 and 4. Replacement of the halide for NCS in the diimine complexes also caused an increase in the branching content, whereas the opposite occurs for the iminophosphine complexes. The different activities and behavior of the catalyst systems with halide versus NCS in the polymerization of ethylene and the characteristics of the final products suggest a modification in the active species caused by the non-chelating ligand. Polymer molecular weight and branching content is dependent on the MAO/Ni molar ratio and on the working temperature.
Acta Crystallographica Section E Structure Reports Online, 2001
... Nadia M. Comerlato, a Geraldo L. Crossetti, a R. Alan Howie, b * Pollyanna CD Tibultino a and... more ... Nadia M. Comerlato, a Geraldo L. Crossetti, a R. Alan Howie, b * Pollyanna CD Tibultino a and James L. Wardell a. ... COLLECT. Nonius BV, Delft, The Netherlands. ... Chem. Rev. 100, 3553-3590. [PubMed] [CrossRef] [ChemPort] Koten, G. van & Vrieze, K. (1982). Adv. Organomet. ...
Journal of Polymer Science Part A: Polymer Chemistry, 2006
DADNiX 2 nickel-diimine complexes [DAD ¼ 2,6-iPr 2 À ÀC 6 H 3 À ÀN¼ ¼C(Me)À À C(Me)¼ ¼NÀ À2,6-iPr... more DADNiX 2 nickel-diimine complexes [DAD ¼ 2,6-iPr 2 À ÀC 6 H 3 À ÀN¼ ¼C(Me)À À C(Me)¼ ¼NÀ À2,6-iPr 2 À ÀC 6 H 3 ] containing nonchelating pseudohalide ligands [X ¼ isothiocyanate (NCS) for complex 1 and isoselenocyanate (NCSe) for complex 2] were synthesized, and the propylene polymerization with these complexes and also with the Br ligand (X ¼ Br for complex 3) activated by methylaluminoxane (MAO) were investigated (systems 1, 2, and 3/MAO). The polypropylenes obtained with systems 1, 2, and 3 were amorphous polymers and had high molecular weights and narrow molecular weight distributions. Catalyst system 1 showed a relatively high activity even at a low Al/Ni ratio and reached the maximum activity at the molar ratio of Al/Ni ¼ 500, unlike system 3. Increases in the reaction temperature and propylene pressure favored an increase in the catalytic activity. The spectra of polypropylenes looked like those of propylene-ethylene copolymers containing syndiotactic propylene and ethylene sequences. At the same temperature and pressure, system 2 presented the highest number of propylene sequences, and system 3 presented the lowest. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 458-466, 2006
Resumo: Cada vez mais as indústrias de produção de polímeros buscam métodos robustos para confirm... more Resumo: Cada vez mais as indústrias de produção de polímeros buscam métodos robustos para confirmar características desejadas achando as condições do processo que levem ao rendimento máximo do polímero. Os processos de polimerização estão sendo aperfeiçoados, colaborando para a obtenção de polímeros cada vez mais sofisticados e baratos. A modelagem do processo de polimerização contribui para isso, uma vez que permite reduzir os custos de desenvolvimento, além de possibilitar compreensão do processo industrial. Neste trabalho, aborda-se sobre modelos regressivos desenvolvidos para o processo de polimerização. Inicialmente, formula-se um problema de otimização com vínculo, onde a Massa (M) representa a função objetivo (definida como uma função polinomial quadrática), dependente das variáveis preditoras: temperatura (T), pressão (P), concentração de alumínio (Al) e da taxa concentração de alumínio/concentração de níquel (Al/Ni); e o peso molecular (PM), fixado em determinado valor, é a...
Polymer Engineering and Science, Sep 1, 2010
A ciência dos polímeros foi gerada em 1920 quando Staudinger postulou o conceito de cadeia polimé... more A ciência dos polímeros foi gerada em 1920 quando Staudinger postulou o conceito de cadeia polimérica. Desde então o interesse na modelagem matemática dos fenômenos associados aos polímeros tem-se desenvolvido com relativa amplitude segundo os períodos de crescimento ou de estabilidade da industria dos polímeros. Os modelos matemáticos para estudar a reação química envolvem equações algébricas e/ou diferenciais. Desta forma no processo de polimerização existem diversos enfoques para obter funções de modelagem, entre eles: * Modelos de regressão multivariada; *Métodos de otimização combinatória. Nosso alvo foi otimizar a atividade polimérica tomando como vínculo um peso molecular fixo (ver Fig 1), após a modelagem da duas funções esboçar a modelagem mediante a regressão de várias variáveis, considerando um p-level 1 apropriado (0,05). Foram trabalhados vários modelos de regressão com diversas variáveis preditoras, tentando empregar como função dependente o peso molecular no caso de o...
Ethylene and 10-undecen-1-ol Copolymerization with the Catalyst System DADNi(NCS) 2 /MAO . The ca... more Ethylene and 10-undecen-1-ol Copolymerization with the Catalyst System DADNi(NCS) 2 /MAO . The catalyst DADNi(NCS) 2 (DAD = (ArN=C(Me)-C(Me)=ArN); Ar = 2,6-C 6 H 3), activated by methylaluminoxane (MAO) was tested at 50°C and Al/Ni ratio: 200. The system was also supported on silica Grace 955. The catalyst system was active in ethylene and 10-undecen-1-ol copolymerization. The polar monomer was protected with IPRA or TIBA. The best activities were obtained at lower concentration of polar monomer and the incorporation increases with the increase of the polar monomer concentration. The quantification of branches by 13 C-NMR showed that all the polyethylenes were highly branched . Introdução Poliolefinas com grupos funcionais ao longo da cadeia principal são de grande interesse por suas propriedades(1). A copolimerização de olefinas com comonômeros polares, é, atualmente, um dos métodos mais interessantes para obter estes materiais, especialmente, quando se usa sistemas catalíticos com...
Este trabalho faz parte do estudo da cinética de polimerização dos sistemas catalíticos formados ... more Este trabalho faz parte do estudo da cinética de polimerização dos sistemas catalíticos formados pelos complexos diimínicos de níquel, ativados por metilaluminoxano na polimerização de eteno, caracterizando os produtos da polimerização e visando relacionar as propriedades finais dos polímeros com as condições do processo de polimerização. Os dados experimentais são modelados buscando estabelecer as condições ótimas de polimerização, e otimizando a atividade do sistema e as propriedades do material polimérico. A modelagem do processo de catalização dos polímeros apresenta diversos problemas que podem ser resolvidos parcialmente com diversos métodos matemáticos de análise. Desenvolver novos materiais poliméricos implica num grande número de testes e caracterizações para determinar quais as condições de processo necessárias para produzir um polímero com as características desejadas. O uso de modelos matemáticos que relacionam as características finais dos polímeros com as condições de ...
Acta Crystallographica Section C Crystal Structure Communications, 2001
In the title compound, [NiBr(2)(C(31)H(32)NP)], (I), the second reported example of a nickel-imin... more In the title compound, [NiBr(2)(C(31)H(32)NP)], (I), the second reported example of a nickel-iminophosphine N,P-chelate in which the Ni atom has tetrahedral coordination, the Ni coordination is distorted as a consequence of the N-Ni-P chelate bite angle of 91.07 (6) degrees compensated by the Br-Ni-Br angle of 126.385 (18) degrees. In (I) and its analogue, viz. dichloro[[2-(4-isobutyloxazol-2-yl)phenyl]diphenylphosphine-N,P]nickel(II), the Ni-N and Ni-P distances are greater and the N-Ni-P ligand bite angles smaller than those observed in a series of related complexes with square-planar nickel.
Polymer Engineering & Science, 2010
This article regards the ethylene polymerization catalyzed by a nickel catalyst and activated by ... more This article regards the ethylene polymerization catalyzed by a nickel catalyst and activated by ethylaluminum sesquichloride (EASC). The effects of the reaction conditions [polymerization temperature, cocatalyst (EASC) concentration, and ethylene concentration] on the average molecular weights of the final polymers and reaction yields were evaluated with the help of empirical statistical models. It is shown that reaction temperature and cocatalyst (EASC) concentration exert the most important effects on average molecular weights and catalyst activity. The polydispersities of the obtained polyethylenes are larger than the polydispersities of polyethylenes obtained with typical Brookhart catalysts. The analysis of polymer branching frequencies shows new types of short branching and significant amounts of long branches, which may explain the relatively large polydispersities of the obtained polymer samples.
Polymer Bulletin, 1998
Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and A... more Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and Al2O3 was investigated. Using catalysts based on MAO supported on silica, a highly isotactic polystyrene was obtained. Nevertheless, the Al2O3-supported catalyst can promote isospecific polymerization activated by common. alkyl aluminum compounds even by any prior support treatment with MAO.
Macromolecular Rapid Communications, 1997
... 1, show that the intensity of the reson-ance at 146.3 ppm, typical of the isotactic pentads43... more ... 1, show that the intensity of the reson-ance at 146.3 ppm, typical of the isotactic pentads435), varies with the type of MA 0 used and decreases in the order ... The crude polymers were fractionated by successive extractions with boiling acetone and methyl ethyl ketone (MEK). ...
Journal of Polymer Science Part A: Polymer Chemistry, 2004
A complete 13 C NMR characterization of a polymer synthesized with a new Ni-diimine complex [DADN... more A complete 13 C NMR characterization of a polymer synthesized with a new Ni-diimine complex [DADNi(NCS) 2 , where DAD ϭ 2,6-iPrOC 6 H 3 ONAC(Me)OC(Me)A NO2,6-iPrOC 6 H 3 ] activated by methylaluminoxane by homopolymerization of propylene is presented. The amorphous material was made up mainly of blocks of syndiotactic polypropylene and ethylene-propylene copolymer. Some degree of propylene inversion (Ͻ1.2 mol %) and of long isobutyl and 2-methyl hexyl branching (Ͻ1 mol %) were assigned and quantified.
Journal of Polymer Science Part A: Polymer Chemistry, 2008
The catalyst DADNi(NCS) 2 (DAD ¼ (ArN¼ ¼C(Me)À ÀC(Me)¼ ¼ArN); Ar ¼ 2,6-C 6 H 3 ), activated by me... more The catalyst DADNi(NCS) 2 (DAD ¼ (ArN¼ ¼C(Me)À ÀC(Me)¼ ¼ArN); Ar ¼ 2,6-C 6 H 3 ), activated by methylaluminoxane, was tested in ethylene polymerization at temperatures above 25 8C and variable Al/Ni ratio. The system was shown to be active even at 80 8C and when supported on silica. However, catalyst activity decreased. The catalyst system was also tested in ethylene and 10-undecen-1-ol copolymerization at different ethylene pressures. The best activities were obtained at low polar monomer concentration (0.017 mol/L), using triisopropylaluminum (Al-i-Pr 3 ) to protect the polar monomer. The incorporation of the comonomer increased with the increase of polar monomer concentration. According to 13 C NMR analyses, all the resulting polyethylenes were highly branched and the polar monomer incorporation decreased as ethylene pressure increased. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5199-5208, 2007
Applied Organometallic Chemistry, 2004
3), [Ar = 2,6-i Pr-C 6 H 3 ; dppe = 1,2-bis(diphenylphosphine)ethane] were synthesized and examin... more 3), [Ar = 2,6-i Pr-C 6 H 3 ; dppe = 1,2-bis(diphenylphosphine)ethane] were synthesized and examined for ethylene polymerization activated by methylaluminoxane (MAO). Their behavior was compared with those of the corresponding halide analogues [ArN C(Me)-C(Me) NAr]NiBr 2 (4), [Ph 2 PC 6 H 4 CH NAr]NiBr 2 (5), and (dppe)NiCl 2 (6). The diimines showed the highest polymerization activity. Replacement of the halide for the NCS pseudo halide affected the activity and decreased the molecular weight of the polymer formed. The highest molecular weights were obtained with the diimine complexes. Highly branched polyethylenes were obtained with the bulkier complexes 1 and 4. Replacement of the halide for NCS in the diimine complexes also caused an increase in the branching content, whereas the opposite occurs for the iminophosphine complexes. The different activities and behavior of the catalyst systems with halide versus NCS in the polymerization of ethylene and the characteristics of the final products suggest a modification in the active species caused by the non-chelating ligand. Polymer molecular weight and branching content is dependent on the MAO/Ni molar ratio and on the working temperature.
Acta Crystallographica Section E Structure Reports Online, 2001
... Nadia M. Comerlato, a Geraldo L. Crossetti, a R. Alan Howie, b * Pollyanna CD Tibultino a and... more ... Nadia M. Comerlato, a Geraldo L. Crossetti, a R. Alan Howie, b * Pollyanna CD Tibultino a and James L. Wardell a. ... COLLECT. Nonius BV, Delft, The Netherlands. ... Chem. Rev. 100, 3553-3590. [PubMed] [CrossRef] [ChemPort] Koten, G. van & Vrieze, K. (1982). Adv. Organomet. ...
Journal of Polymer Science Part A: Polymer Chemistry, 2006
DADNiX 2 nickel-diimine complexes [DAD ¼ 2,6-iPr 2 À ÀC 6 H 3 À ÀN¼ ¼C(Me)À À C(Me)¼ ¼NÀ À2,6-iPr... more DADNiX 2 nickel-diimine complexes [DAD ¼ 2,6-iPr 2 À ÀC 6 H 3 À ÀN¼ ¼C(Me)À À C(Me)¼ ¼NÀ À2,6-iPr 2 À ÀC 6 H 3 ] containing nonchelating pseudohalide ligands [X ¼ isothiocyanate (NCS) for complex 1 and isoselenocyanate (NCSe) for complex 2] were synthesized, and the propylene polymerization with these complexes and also with the Br ligand (X ¼ Br for complex 3) activated by methylaluminoxane (MAO) were investigated (systems 1, 2, and 3/MAO). The polypropylenes obtained with systems 1, 2, and 3 were amorphous polymers and had high molecular weights and narrow molecular weight distributions. Catalyst system 1 showed a relatively high activity even at a low Al/Ni ratio and reached the maximum activity at the molar ratio of Al/Ni ¼ 500, unlike system 3. Increases in the reaction temperature and propylene pressure favored an increase in the catalytic activity. The spectra of polypropylenes looked like those of propylene-ethylene copolymers containing syndiotactic propylene and ethylene sequences. At the same temperature and pressure, system 2 presented the highest number of propylene sequences, and system 3 presented the lowest. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 458-466, 2006