Investigation of pyridine sorption in USY and Ce/USY zeolites by liquid phase microcalorimetry and thermogravimetry studies

Ghesti, Grace Ferreira; Macedo, Julio L. de; Parente, Vicente Cavalcanti Ibiapina; Dias, José A.; Dias, Sílvia C.L.

doi:10.1016/j.micromeso.2006.10.005

Cited by 33 publications

(23 citation statements)

References 57 publications

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“…Although a definitive assignment of the hydroxyl bands in USY zeolites cannot be performed at this moment, the bands at 3566 and 3642 cm -1 were more affected by cerium than the other ones, indicating that the ion exchange between cerium ions and protons occurred during impregnation steps. 22 In the present study, an increase of the Lewis/Brønsted ratio with increasing cerium loadings was observed (Table 3), which was attributed to a decrease of Brønsted sites that interacted with cerium species and an increase of Lewis sites. For the samples with 15 and 25% loadings, a decrease of the ratio could be an indication of the formation of cerium agglomerates with 25% loading, as observed with both SEM micrographs and FT-Raman spectroscopy.…”

Section: Ce-usy Aciditysupporting

confidence: 60%

“…[22][23][24][25] Similar nitrogen adsorption isotherms were reported by Yao et al 26 and Schneider et al 27 for sodalite and NaY zeolites, respectively.…”

Section: Thermal Evolution and Textural Characterizationsupporting

confidence: 60%

“…49,50 Gu et al 49 reported the presence of Brønsted and Lewis sites in CeO 2 by ammonia adsorption studies. Ghesti et al 22 reported recently two types of acid sites with enthalpies of −117.6 kJ mol -1 and −83.6 kJ mol -1 , which were assigned to Brønsted, and a combination of weak Brønsted/Lewis sites for 5 wt.% Ce-HUSY. The impregnation of cerium reduced the acidity of the HUSY zeolite, which previously had Brønsted sites with enthalpies of −134.0 kJ mol -1 and −101.5 kJ mol -1 , through the interaction with Si−O(H)−Al bridges, as observed by DRIFTS measurements.…”

Section: Ce-usy Aciditymentioning

confidence: 99%

“…In addition, a decrease in the intensity of the Al(VI) peak with increasing CeO 2 loading was observed due to the loss of crystallinity, as determined by XRD results. Ghesti et al 22 reported a decrease in the intensity of EFAL and Si−O(H)−Al groups at 3642 and 3566 cm -1 using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). There was also a convoluted signal between −0.4 and 59.1 ppm, which might be related to the presence of aluminum in distorted octahedral and/or tetrahedral sites.…”

mentioning

confidence: 99%

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Effect of cerium loading on structure and morphology of modified Ce-USY zeolites

Garcia¹,

Araújo²,

Silva³

et al. 2011

J. Braz. Chem. Soc.

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Este trabalho descreve detalhadamente o efeito da quantidade de cério na estrutura e morfologia da zeólita NH 4 USY. Ce-USY (2-25% m/m de CeO 2 ) foi obtido por impregnação úmida de CeCl 3 seguida de calcinação a 550 ºC por 8 h. Em quantidades baixas (2-10%), foi observado que as espécies de cério encontram-se nas posições de troca iônica na rede, enquanto em maiores teores (15-25%) pequenos agregados formaram-se na superfície da HUSY. Difratometria de raios X (XRD) mostrou apenas reflexões relacionadas à HUSY, confirmando a alta dispersão das espécies de cério, porém as análises por espectroscopia Raman com transformada de Fourier (FT-Raman) detectaram CeO x para os materiais acima de 10%. A reação do CeCl 3 com NH 4 USY produziu NH 4 Cl, o qual se decompõe em HCl, ocasionando a desaluminização da rede. Os materiais apresentaram um aumento da razão Lewis/Brønsted com o aumento da quantidade de cério, devido a interação do excesso de cério com os grupos OH da USY e consequente formação de espécies CeO x . This work describes comprehensibly the effect of cerium loading on the structure and morphology of NH 4 USY zeolite. The Ce-USY (2-25 wt.% of CeO 2 ) was obtained by wet impregnation of CeCl 3 followed by calcination at 550 ºC for 8 h. At low loadings (2-10%), cerium species are mainly located at ion exchange positions in the framework, whereas at higher loadings (15-25%), small aggregates were formed on the HUSY surface. X-ray diffractograms (XRD) exhibited only the reflections related to HUSY, demonstrating the high dispersion of cerium species, but Fourier transform Raman spectroscopy (FT-Raman) detected CeO x for the materials above 10%. Reaction of CeCl 3 with NH 4 USY produced NH 4 Cl, which decomposed to form HCl, leading to framework dealumination. The materials showed an increased Lewis/Brønsted ratio with increasing cerium loadings due to the interaction between the excess cerium and the OH groups of USY, and the consequent formation of CeO x species.Keywords: cerium USY zeolite, cerium oxide, ultra stable Y zeolite, solid-state ion exchange, 27 Al and 29 Si MAS NMR spectroscopy IntroductionFaujasite-type zeolites (X and Y) are largely applied in fluid catalytic cracking (FCC) of crude oil distillates and in hydrodesulfurization of fossil diesel oil and gasoline. 1 Y zeolites, either in their sodium or ammonium form, can be exchanged for rare earth ions to achieve the following main goals: (i) to prevent aluminum loss from the zeolite structure, which results in enhanced structural resistance to the severe hydrothermal conditions of the regeneration step of FCC, 2 and (ii) to increase the activity, because the introduction of rare earth species modifies the number of acidic protons through either hydrolysis or enhancement of ionic fields inside the zeolite structure. 3 Because rare earth cations modify the acidic properties of zeolites, their insertion has an effect on both thermal and mechanical stability, which are important for zeolite application to industrial processes such as pyrolysis, 4 oxidat...

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Section: Ce-usy Aciditysupporting

confidence: 60%

“…[22][23][24][25] Similar nitrogen adsorption isotherms were reported by Yao et al 26 and Schneider et al 27 for sodalite and NaY zeolites, respectively.…”

Section: Thermal Evolution and Textural Characterizationsupporting

confidence: 60%

Section: Ce-usy Aciditymentioning

confidence: 99%

mentioning

confidence: 99%

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Effect of cerium loading on structure and morphology of modified Ce-USY zeolites

Garcia¹,

Araújo²,

Silva³

et al. 2011

J. Braz. Chem. Soc.

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“…37 Os catalisadores foram desidratados em N 2 anidro a 300 ºC por 1 h, resfriados a 100 °C e depois permitiu-se que piridina gasosa diluída em N 2 passasse pelas amostras por 1 h. Por fim, manteve-se a temperatura a 100 °C em fluxo de N 2 por 1 h para remover a piridina fisicamente adsorvida. Após o experimento, as amostras foram analisadas por TG/DTG e FTIR.…”

Section: Adsorção De Piridinaunclassified

Produção de biodiesel via transesterificação etílica com zeólitas básicas

et al. 2012

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Recebido em 25/2/11; aceito em 30/6/11; publicado na web em 5/8/11 BIODIESEL PRODUCTION VIA ETHYLIC TRANSESTERIFICATION WITH BASIC ZEOLITES. Soybean oil transesterification with ethanol was carried out in a batch reactor using USY zeolites modified with barium and strontium (15 wt.%) as catalysts. A series of three catalytic cycles were performed for each zeolite without any loss of activity. The biodiesel product was analyzed by HPLC and FT-Raman, and the catalysts by pyridine and CO 2 adsorption. Ba/USY provided higher conversions (> 97%) than Sr/USY (< 75%). The increased catalytic activity of Ba/USY was attributed to two different effects: a larger number of basic sites; and a lower interaction between barium species and HUSY Brønsted sites.Keywords: biodiesel; basic zeolites; transesterification. INTRODUÇÃOA Sociedade Americana de Testes e Materiais (ASTM) definiu biodiesel como um combustível constituído de ésteres de monoalquila de ácidos graxos de cadeias longas derivados de óleos vegetais ou gordura animal, que satisfaçam os requerimentos da norma ASTM D 6751.1,2 O biodiesel apresenta diversas vantagens quando comparado ao diesel derivado de petróleo: é derivado de fontes renováveis, biodegradável, não tóxico, apresenta baixa emissão de poluentes, alto ponto de fulgor, excelente lubricidade e pode ser usado puro ou misturado com diesel derivado do petróleo. 1,3,4 O uso de óleos vegetais como combustível é conhecido desde a Exposição de Paris, em 1900. 4 No entanto, devido ao seu alto peso molecular e alta viscosidade cinética, seu uso direto em motores a diesel resultou em diversos problemas operacionais (e.g., pobre atomização, formação de depósitos de carbono devido à combustão incompleta, problemas de lubrificação, etc.).1,4,5 Para resolver estes problemas, quatro soluções possíveis foram investigadas na literatura: transesterificação (também chamada de alcoólise), pirólise, diluição com diesel derivado de petróleo e microemulsão. 1,[4][5][6][7][8][9][10][11][12] Dentre os métodos citados acima, a reação de transesterificação é o único processo que leva aos produtos definidos pela ASTM (i.e., ésteres de alquila) e é o método mais utilizado para produzir biodiesel.1-4 Na transesterificação, as moléculas de triglicerídeos encontradas no óleo ou gordura animal ou vegetal (e.g., óleo de soja, 2-/ZrO 2 , SO 4 2-/SnO 2 ), 26 materiais mesoporosos 27 e zeólitas (NaOx/NaX, ETS-10, 21 etc.), entre outros. Dentre os catalisadores citados acima, as zeólitas se destacam devido à grande quantidade de aplicações que apresentam na indústria química, como catalisadores e adsorventes. As zeólitas apresentam propriedades singulares, tais como, alta área superficial, propriedades de adsorção, propriedades de troca iônica, centros ativos dentro do sistema de canais e cavidades, e diferentes tipos de seletividade. [28][29][30][31][32][33][34] A alta área superficial desses materiais e suas propriedades de troca iônica permitem que sua rede cristalina seja usada para gerar centros básicos ativos na estrutura zeolítica (e....

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Catalytically Active Sites: Generation and Characterization

Hunger

2010

Zeolites and Catalysis

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Investigation of pyridine sorption in USY and Ce/USY zeolites by liquid phase microcalorimetry and thermogravimetry studies

Cited by 33 publications

References 57 publications

Effect of cerium loading on structure and morphology of modified Ce-USY zeolites

Effect of cerium loading on structure and morphology of modified Ce-USY zeolites

Produção de biodiesel via transesterificação etílica com zeólitas básicas

Catalytically Active Sites: Generation and Characterization

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