JORGE MOREIRA VAZ
3 resultados
Resultados de Busca
Agora exibindo 1 - 3 de 3
Artigo IPEN-doc 30352 Methane conversion and hydrogen production over TiO2/WO3/Pt heterojunction photocatalysts2024 - CARMINATI, SAULO A.; JANUARIO, ELAINE R.; MACHADO, ARTHUR P.; SILVAINO, PATRICIA F.; VAZ, JORGE M.; SPINACE, ESTEVAM V.Along with the advantages of mild reaction conditions, simple operation, and low energy consumption, the photocatalytic conversion of methane in the presence of water presents great potential in facilitating direct methane conversion into value-added chemicals and H-2 generation. In this work, TiO2/WO3 heterojunction photocatalysts modified with Pt nanoparticles were synthesized and their performances towards methane conversion into ethane (C2H6) and hydrogen (H-2) in the presence of water were evaluated. The ternary photocatalysts were characterized by X-ray diffraction, UV-vis, scanning and transmission electron microscopy and X-ray photoelectron spectroscopy. The highly active TiO2/WO3/Pt photocatalyst achieved C2H6 and H-2 production rates of 1.18 mmol g(-1) h(-1) and 57 mmol g(-1) h(-1), respectively. These values were 37% (for C2H6) and 34% (for H-2) higher than those produced by a TiO2/Pt photocatalyst. The results show that the presence of WO3 in a very small concentration on TiO2 with the introduction of Pt as a co-catalyst contributes to achieving higher activities towards both C2H6 and H-2 evolution.Artigo IPEN-doc 30182 Methane conversion coupled with hydrogen production from water using Au/Ga2O3 photocatalysts prepared by different methods2023 - JANUARIO, ELAINE R.; CARMINATI, SAULO A.; TOFANELLO, ARYANE; SILVA, BRUNO L. da; SILVAINO, PATRICIA F.; MACHADO, ARTHUR P.; VAZ, JORGE M.; SPINACE, ESTEVAM V.Au/Ga2O3 photocatalysts were prepared by three different methods (pre-formed Au nanoparticles, borohydride reduction, and impregnation-H2 reduction) and tested as photocatalysts for methane conversion coupled with hydrogen production from water. The photocatalysts were characterized by Xray fluorescence, X-ray diffraction, UV-vis, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and PL spectroscopy. The reactions were performed with the photocatalysts dispersed in water in a bubbling methane stream under UV-light illumination. The products were identified and quantified by gas chromatography (GC-FID/TCD/MSD). The main products formed were H2, C2H6, CO, and CO2 with minor quantities of C2H4, C3H8, and C4H10. The best performances were observed for the photocatalysts prepared with the nominal Au content of 0.1 wt% regardless of the method used. A production rate of about 100 mmol g−1 h−1 for C2H6 and 15 000 mmol g−1 h−1 for H2 was obtained. The Au content, nanoparticle sizes and interactions with Ga2O3 strongly influenced the photocatalytic activity.Artigo IPEN-doc 28346 Methane Conversion Under Mild Conditions Using Semiconductors and Metal-Semiconductors as Heterogeneous Photocatalysts2021 - JANUARIO, ELIANE R.; SILVAINO, PATRICIA F.; MACHADO, ARTHUR P.; VAZ, JORGE M.; SPINACE, ESTEVAM V.The processes currently used in the chemical industry for methane conversion into fuels and chemicals operate under extreme conditions like high temperatures and pressures. In this sense, the search for methane conversion under mild conditions remains a great challenge. This review aims to summarize the use semiconductors and metal-semiconductors as heterogeneous photocatalysts for methane conversion under mild conditions into valuable products. First, a brief presentation of photochemical conversion of methane is provided and then the focus of this review on the use of heterogeneous photocatalysts for methane conversion are described. Finally, the main challenges and opportunities are discussed.