Banca de DEFESA: HELOISA PIMENTA DE MACEDO
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.DISCENTE : HELOISA PIMENTA DE MACEDO
DATA : 27/07/2018
HORA: 09:00
LOCAL: Auditório do CCET
TÍTULO:
Hybrid Porous Ceramics Derived from Polysiloxanes Containing Ni Nanoparticles for Production of CH4 via Hydrogenation of CO2
PALAVRAS-CHAVES:
Hybrid ceramics, polysiloxane, polymer-derived ceramic, catalysis, nickel, CO2 methanation
PÁGINAS: 101
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
ESPECIALIDADE: Cerâmicos
RESUMO:
Preceramic polymers are Si-based organic–inorganic materials that can be converted to ceramics under inert atmosphere, resulting in hybrid materials with adjustable characteristics and interesting physico-chemical properties. Hybrid ceramic materials with dispersed Ni nanoparticles were prepared by pyrolytic conversion of polysiloxane precursors in order to evaluate their applicability in CO2 methanation. Materials with tailorable characteristics were synthesized by varying the precursors (polysiloxanes with either methyl or methyl phenyl groups) and by ranging the pyrolysis temperature from 400 to 600, leading to the formation of porous materials in a hybrid state where the polymer is just partly converted to ceramic. The siloxane bistrimethoxysilylpropylamine (BisA) was used as complexing agent of the metal precursor. The materials were characterized by thermogravimetric analysis (TGA), N2 adsorption-desorption isotherms (BET-BJH), water and n-heptane adsorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Catalytic CO2 methanation tests (CO2 + 4 H2 → CH4 + 2 H2O) were performed between 200 – 400 at atmospheric pressure. In-situ X-ray diffraction analysis (in-situ XRD) was used to evaluate the Ni particle structure and size during a simulated catalytic reaction. Ceramers with hierarchical porosity (micro, meso and macropores), high specific surface areas (100-550 m2.g-1), hydrophobic or hydrophilic surfaces and different Ni particle sizes (4-7 nm) were obtained by changing the pyrolysis temperature and polysiloxane composition. Regarding the catalytic performance, ceramers prepared from methyl polysiloxane precursor exhibited less hydrophilic surfaces and, thus, improved catalytic performance compared to the ones preparaded from metyl phenyl polysiloxanes. A negative effect on the catalytic performance of ceramers was observed with increasing pyrolysis temperatures, which led to an increase in the Ni particle size (from 4 to 7 nm), and consequently, lower levels of conversion and selectivity. The ceramers pyrolyzed at 400 exhibited the best catalytic performance, showing selectivity up to ~77% and good stability during a 10 h test, whereas preserving the Ni crystallite size as shown by the in-situ XRD. Therefore, Ni based hybrid ceramers derived from polysiloxanes are promising catalysts with highly distributed metal particles and tunable surface properties.
MEMBROS DA BANCA:
Presidente - 349770 - DULCE MARIA DE ARAUJO MELO
Interno - 1883170 - MAURICIO ROBERTO BOMIO DELMONTE
Externo ao Programa - 1979301 - RENATA MARTINS BRAGA
Externo à Instituição - BRAULIO SILVA BARROS - UFPE
Externo à Instituição - MICHAELA WILHELM - Uni Bremen