Flavia Guinhos - Academia.edu (original) (raw)

Papers by Flavia Guinhos

Journal of Alloys and Compounds, 2001

Up-conversion of infrared radiation to the visible and ultraviolet regions in PbF-GeO-Al O-Tm O-Y... more Up-conversion of infrared radiation to the visible and ultraviolet regions in PbF-GeO-Al O-Tm O-Yb O oxyfluoride glasses 2 2 2 3 2 3 2 3 and glass ceramics was obtained, exciting at 1.0 mm with a diode laser at room temperature. Transparent films and microspheres were prepared by a modified spin-coating technique. The effect of host composition on the up-conversion luminescence was studied in order to 31˚i mprove the ultraviolet radiation generation. In the glass samples, the Tm blue (4786 A) and red (6500 A) visible emissions got more 31 1 3 cross-relaxation process given by (F , G)→(H , D).

Journal of the Brazilian Chemical Society, 2009

Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH ... more Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH 2 O com ácido sulfúrico, fosfórico, nítrico, sendo investigados juntamente com Nb 2 O 5 e Nb 2 O 5 •xH 2 O como catalisadores na reação de transesterificação, esterificação e pirólise de óleos vegetais. Os catalisadores foram caracterizados por análise térmica (DTA-TGA), espectroscopia (DRX, FT-IV e FT-Raman), área superficial (BET), e determinada acidez (Ho) pela titulação com n-butilamina utilizando o método Hammet. Após o tratamento ácido, todas as áreas superficiais e a acidez decresceram comparadas com o Nb 2 O 5. xH 2 O utilizado inicialmente no tratamento. A única exceção foi a alta acidez verificada quando o ácido nítrico foi utilizado. Entre os catalisadores testados, o Nb 2 O 5 /H 3 PO 4 apresentou boa atividade na reação de alcoólise do óleo de soja com diferentes alcoóis (metanol, etanol, 2-propanol, n-butanol). Todos os sólidos testados demonstraram estabilizar ácidos carboxílicos durante a pirólise. Finalmente, o uso de Nb 2 O 5 /H 3 PO 4 e Nb 2 O 5 /H 2 SO 4 como catalisador na reação de esterificação demonstrou melhor atividade que o Nb 2 O 5 e Nb 2 O 5 •xH 2 O. Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) compounds were obtained from the treatment of niobium acid (Nb 2 O 5 •xH 2 O) with sulfuric, phosphoric, and nitric acids as well as Nb 2 O 5 and Nb 2 O 5 •xH 2 O have been investigated as catalysts for the transesterification, esterification and pyrolysis of vegetable oils. The compounds were characterized by thermal analysis (DTA-TGA), spectroscopy (DRX, FT-IR and FT-Raman), surface area (BET) and the acidity (Ho) determined by n-butylamine titration using the Hammet´s indicator method. It was observed that after the acid treatment both the surface area and the acidity decreased as compared to the starting Nb 2 O 5 •xH 2 O. The only exception was a higher acidity verified when nitric acid was used. Among the catalyst investigated, the Nb 2 O 5 /H 3 PO 4 presented the highest activity in the alcoholysis of soybean oil with different mono-alcohols (methanol, ethanol, 2-propanol, n-butanol). All tested solids seemed to stabilize the carboxylic acids formed during the pyrolysis, yielding higher acid numbers for the obtained products. Finally, the use of Nb 2 O 5 /H 3 PO 4 and Nb 2 O 5 /H 2 SO 4 as catalysts for the esterification showed better activity than Nb 2 O 5 •xH 2 O and Nb 2 O 5 .

Journal of the Brazilian Chemical Society, 2009

Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH ... more Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH 2 O com ácido sulfúrico, fosfórico, nítrico, sendo investigados juntamente com Nb 2 O 5 e Nb 2 O 5 •xH 2 O como catalisadores na reação de transesterificação, esterificação e pirólise de óleos vegetais. Os catalisadores foram caracterizados por análise térmica (DTA-TGA), espectroscopia (DRX, FT-IV e FT-Raman), área superficial (BET), e determinada acidez (Ho) pela titulação com n-butilamina utilizando o método Hammet. Após o tratamento ácido, todas as áreas superficiais e a acidez decresceram comparadas com o Nb 2 O 5. xH 2 O utilizado inicialmente no tratamento. A única exceção foi a alta acidez verificada quando o ácido nítrico foi utilizado. Entre os catalisadores testados, o Nb 2 O 5 /H 3 PO 4 apresentou boa atividade na reação de alcoólise do óleo de soja com diferentes alcoóis (metanol, etanol, 2-propanol, n-butanol). Todos os sólidos testados demonstraram estabilizar ácidos carboxílicos durante a pirólise. Finalmente, o uso de Nb 2 O 5 /H 3 PO 4 e Nb 2 O 5 /H 2 SO 4 como catalisador na reação de esterificação demonstrou melhor atividade que o Nb 2 O 5 e Nb 2 O 5 •xH 2 O. Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) compounds were obtained from the treatment of niobium acid (Nb 2 O 5 •xH 2 O) with sulfuric, phosphoric, and nitric acids as well as Nb 2 O 5 and Nb 2 O 5 •xH 2 O have been investigated as catalysts for the transesterification, esterification and pyrolysis of vegetable oils. The compounds were characterized by thermal analysis (DTA-TGA), spectroscopy (DRX, FT-IR and FT-Raman), surface area (BET) and the acidity (Ho) determined by n-butylamine titration using the Hammet´s indicator method. It was observed that after the acid treatment both the surface area and the acidity decreased as compared to the starting Nb 2 O 5 •xH 2 O. The only exception was a higher acidity verified when nitric acid was used. Among the catalyst investigated, the Nb 2 O 5 /H 3 PO 4 presented the highest activity in the alcoholysis of soybean oil with different mono-alcohols (methanol, ethanol, 2-propanol, n-butanol). All tested solids seemed to stabilize the carboxylic acids formed during the pyrolysis, yielding higher acid numbers for the obtained products. Finally, the use of Nb 2 O 5 /H 3 PO 4 and Nb 2 O 5 /H 2 SO 4 as catalysts for the esterification showed better activity than Nb 2 O 5 •xH 2 O and Nb 2 O 5 .

Journal of Alloys and Compounds, 2001

Up-conversion of infrared radiation to the visible and ultraviolet regions in PbF-GeO-Al O-Tm O-Y... more Up-conversion of infrared radiation to the visible and ultraviolet regions in PbF-GeO-Al O-Tm O-Yb O oxyfluoride glasses 2 2 2 3 2 3 2 3 and glass ceramics was obtained, exciting at 1.0 mm with a diode laser at room temperature. Transparent films and microspheres were prepared by a modified spin-coating technique. The effect of host composition on the up-conversion luminescence was studied in order to 31˚i mprove the ultraviolet radiation generation. In the glass samples, the Tm blue (4786 A) and red (6500 A) visible emissions got more 31 1 3 cross-relaxation process given by (F , G)→(H , D).

Journal of the Brazilian Chemical Society, 2009

Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH ... more Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH 2 O com ácido sulfúrico, fosfórico, nítrico, sendo investigados juntamente com Nb 2 O 5 e Nb 2 O 5 •xH 2 O como catalisadores na reação de transesterificação, esterificação e pirólise de óleos vegetais. Os catalisadores foram caracterizados por análise térmica (DTA-TGA), espectroscopia (DRX, FT-IV e FT-Raman), área superficial (BET), e determinada acidez (Ho) pela titulação com n-butilamina utilizando o método Hammet. Após o tratamento ácido, todas as áreas superficiais e a acidez decresceram comparadas com o Nb 2 O 5. xH 2 O utilizado inicialmente no tratamento. A única exceção foi a alta acidez verificada quando o ácido nítrico foi utilizado. Entre os catalisadores testados, o Nb 2 O 5 /H 3 PO 4 apresentou boa atividade na reação de alcoólise do óleo de soja com diferentes alcoóis (metanol, etanol, 2-propanol, n-butanol). Todos os sólidos testados demonstraram estabilizar ácidos carboxílicos durante a pirólise. Finalmente, o uso de Nb 2 O 5 /H 3 PO 4 e Nb 2 O 5 /H 2 SO 4 como catalisador na reação de esterificação demonstrou melhor atividade que o Nb 2 O 5 e Nb 2 O 5 •xH 2 O. Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) compounds were obtained from the treatment of niobium acid (Nb 2 O 5 •xH 2 O) with sulfuric, phosphoric, and nitric acids as well as Nb 2 O 5 and Nb 2 O 5 •xH 2 O have been investigated as catalysts for the transesterification, esterification and pyrolysis of vegetable oils. The compounds were characterized by thermal analysis (DTA-TGA), spectroscopy (DRX, FT-IR and FT-Raman), surface area (BET) and the acidity (Ho) determined by n-butylamine titration using the Hammet´s indicator method. It was observed that after the acid treatment both the surface area and the acidity decreased as compared to the starting Nb 2 O 5 •xH 2 O. The only exception was a higher acidity verified when nitric acid was used. Among the catalyst investigated, the Nb 2 O 5 /H 3 PO 4 presented the highest activity in the alcoholysis of soybean oil with different mono-alcohols (methanol, ethanol, 2-propanol, n-butanol). All tested solids seemed to stabilize the carboxylic acids formed during the pyrolysis, yielding higher acid numbers for the obtained products. Finally, the use of Nb 2 O 5 /H 3 PO 4 and Nb 2 O 5 /H 2 SO 4 as catalysts for the esterification showed better activity than Nb 2 O 5 •xH 2 O and Nb 2 O 5 .

Journal of the Brazilian Chemical Society, 2009

Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH ... more Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) foram obtidos após o tratamento do Nb 2 O 5 •xH 2 O com ácido sulfúrico, fosfórico, nítrico, sendo investigados juntamente com Nb 2 O 5 e Nb 2 O 5 •xH 2 O como catalisadores na reação de transesterificação, esterificação e pirólise de óleos vegetais. Os catalisadores foram caracterizados por análise térmica (DTA-TGA), espectroscopia (DRX, FT-IV e FT-Raman), área superficial (BET), e determinada acidez (Ho) pela titulação com n-butilamina utilizando o método Hammet. Após o tratamento ácido, todas as áreas superficiais e a acidez decresceram comparadas com o Nb 2 O 5. xH 2 O utilizado inicialmente no tratamento. A única exceção foi a alta acidez verificada quando o ácido nítrico foi utilizado. Entre os catalisadores testados, o Nb 2 O 5 /H 3 PO 4 apresentou boa atividade na reação de alcoólise do óleo de soja com diferentes alcoóis (metanol, etanol, 2-propanol, n-butanol). Todos os sólidos testados demonstraram estabilizar ácidos carboxílicos durante a pirólise. Finalmente, o uso de Nb 2 O 5 /H 3 PO 4 e Nb 2 O 5 /H 2 SO 4 como catalisador na reação de esterificação demonstrou melhor atividade que o Nb 2 O 5 e Nb 2 O 5 •xH 2 O. Nb 2 O 5 /HX (X = HSO 4 − , H 2 PO 4 − , NO 3 −) compounds were obtained from the treatment of niobium acid (Nb 2 O 5 •xH 2 O) with sulfuric, phosphoric, and nitric acids as well as Nb 2 O 5 and Nb 2 O 5 •xH 2 O have been investigated as catalysts for the transesterification, esterification and pyrolysis of vegetable oils. The compounds were characterized by thermal analysis (DTA-TGA), spectroscopy (DRX, FT-IR and FT-Raman), surface area (BET) and the acidity (Ho) determined by n-butylamine titration using the Hammet´s indicator method. It was observed that after the acid treatment both the surface area and the acidity decreased as compared to the starting Nb 2 O 5 •xH 2 O. The only exception was a higher acidity verified when nitric acid was used. Among the catalyst investigated, the Nb 2 O 5 /H 3 PO 4 presented the highest activity in the alcoholysis of soybean oil with different mono-alcohols (methanol, ethanol, 2-propanol, n-butanol). All tested solids seemed to stabilize the carboxylic acids formed during the pyrolysis, yielding higher acid numbers for the obtained products. Finally, the use of Nb 2 O 5 /H 3 PO 4 and Nb 2 O 5 /H 2 SO 4 as catalysts for the esterification showed better activity than Nb 2 O 5 •xH 2 O and Nb 2 O 5 .