Influência do método de preparação e performance catalítica para os catalisadores de Pd-La2O3-Al2O3 aplicados na reforma autotérmica do metano

Pd catalysts supported on Al2O3 and La2O3-Al2O3 (12 wt.% La2O3) were prepared by wetness impregnation method with aqueous solution of of palladium nitrate (1 wt.% Pd). The supports were obtained by conventional method (PdAl-Conv. and PdLaAl-Conv.) and two different sol-gel methods with Al-sec-butoxide/HNO3/Ethanol (PdAl-SG-Et. and PdLaAl-SG-Et) and Al-sec-butoxide/CH3COOH/sec-butanol (PdAl- SG-2But. and PdLaAl-SG-2But.). The catalysts were characterized by X-ray diffraction (XRD), BET surface area of catalysts were calculated from nitrogen absorption isotherm (SBET), FTIR-CO adsorption spectroscopy and autothermal reforming of methane (ATRM). XRD of precursors shows diffraction lines of boehmit for -SGEt. sample and shows diffraction lines of aluminum acetate for -SG-2But sample. No peaks of Pd or PdO were reveled in all catalysts samples. SBET for PdAl-SG-Et, PdLaAl- SG-Et and PdAl-SG-2But.catalysts shows type IV adsorption isotherm and H1 hysteresis and for PdLaAl-SG-2But catalyst shows type III adsorption isotherm and H3 hysteresis. FTIR-CO show that the adding of lanthana on γ-Al2O3 suppress CO adsorption in bridge form over Pd. The CO adsorption form is insensitive to presence of lanthana in catalysts obtained by sol-gel method. The intensity of bands of CO in bridge (LF) and linear (HF) show a LF/HF ratio of 4.8 to 2.3 for PdAl-Conv. and PdLaAl- Conv catalysts, respectively. The Pd catalysts supported on Al2O3 show higher deactivation with time on stream on ATRM reaction, which is assigned mainly to coalescence of Pd particle. La-containing catalysts are quite stable and H2/CO ratio depends to the synthesis method.Universidade Federal de Sao CarlosAl2O3 e La2O3-Al2O3 (12 % p/p de La2O3) com solução aquosa de nitrato de paládio (1% p/p). Os suportes foram obtidos pelos métodos convencional (PdAl-Conv. e PdLaAl-Conv.), sol-gel a partir do Al-tri-sec-butóxido/etanol/HNO3 (PdAl-SG-Et e PdLaAl-SG-Et) e Al-tri-sec-butóxido/2-butanol/CH3COOH (PdAl-SG-2But. e PdLaAl- SG-2But ).Os catalisadores foram caracterizados por difração de raios-X (DRX), área superficial específica (SBET), espectroscopia de refletância difusa na região do infravermelho com transformada de Fourier da adsorção do CO (DRIFTS-CO) e empregados na reação de reforma autotérmica do metano (RAM). Os resultados de DRX dos precursores obtidos pelo método sol-gel etanol/HNO3 e 2-butanol/CH3COOH apresentam uma estrutura do tipo boehmita e acetato de alumínio, respectivamente. Os catalisadores não apresentam picos difração referentes as espécies Pd e PdO, sugerindo que o metal esteja bem disperso no suporte. Os catalisadores PdAl-SG-Et., PdLaAl-SGEt. e PdAl-SG-2But. apresentam isotermas de adsorção do tipo IV, histerese H1e o catalisador PdLaAl-SG-2But. isoterma do tipo III e histerese H3. Os resultados de DRIFTS-CO mostram que a adição de La2O3 à γ-Al2O3 comercial suprime a adsorção do CO na forma de ponte sobre o Pd, enquanto que a forma de adsorção do CO não é sensível a presença de La2O3 nos suportes obtidos pelo método sol-gel. A razão das bandas BF/AF de CO adsorvido na forma de ponte e linear é de aproximadamente 4,8 e 2,3 para as amostras PdAl-Conv. e PdLaAl-Conv., respectivamente. Os catalisadores suportados em Al2O3 apresentam uma forte desativação durante o período de 24h em reação de RAM a 800 °C, devido principalmente a aglomeração das partículas de Pd e não a deposição de carbono. Os catalisadores contendo La são mais estáveis e a razão H2/CO é dependente do método de preparação

NUMERICAL EVALUATION OF THE EFFECTS OF SOFT-MELTING PROPERTIES ON THE KINETIC OF (CAFE2 O4 -CA2 FE2 O5 ) FORMATION IN THE IRON ORE SINTERING PROCESS

This paper presents a mathematical model able to predict the influence of soft-melting properties of the blend of raw materials used in the iron ore sintering process in the kinetic formation of calcium ferrite and di-calcium ferrite constituents. The model is based on the simultaneous solution of transport equations of Momentum, energy and chemical species in multiphase multicomponent systems coupled with the chemical reactions kinetics and phase transformations that occur within the sinter bed. The numerical solution is obtained using the finite volume method and the model is validated using monitoring data from an industrial scale sintering plant. After validation, the model was used to predict processing conditions using raw materials with different soft-melting properties. Results indicate that the temperatures of starting soft-melting, shrinkage and melting range are the main parameters to be controlled in order to attain liquid phases formation responsible to confer good mechanical and reducibility properties for the sinter product. In this study was found that raw materials with high soft-melting temperature and wilder temperature of mushy zone could decrease up to 30% the calcium ferrites formation and hence deteriorates the metallurgical properties of the sinter

PRODUÇÃO DE CARVÃO VEGETAL A PARTIR DA CARBONIZAÇÃO DE CAPIM ELEFANTE (Pennisetum purpureum Schum.)

Pesquisadores e grandes empresas vêm buscando alternativas energéticas que possam diminuir a dependência e utilização de combustíveis de origem fóssil. Nesse sentindo, aponta-se o uso da biomassa como uma fonte renovável energética muito promissora e dentre elas destaca-se o capim elefante (Pennisetum purpureum Schum.). Seguindo essa vertente da tecnologia de biocombustíveis, neste trabalho foi realizada a transformação do capim elefante in natura até a obtenção do carvão, utilizando uma temperatura de carbonização de 450°C. Posteriormente, realizaram-se caracterizações do material que permitiram o estudo de suas propriedades físico-químicas, tais como análise química imediata, poder calorífico e tensão de ruptura. Os resultados corroboram para a aplicação do carvão obtido como um combustível promissor

Ni and Cu based catalysts supported over Hbeta - Evaluation on hydrodesoxigenation of Benzaldehyde

<p></p><p>ABSTRACT The activity and selectivity evaluation of nickel (Ni) and copper (Cu) catalysts supported over Hbeta in the hydrodeoxygenation (HDO) reaction of benzaldehyde were studied. For this purpose, monometallic (10 wt.% of NiO or CuO) and bimetallic catalysts with 10 wt.% of NiO with different CuO (2.5 %, 5 %, 7.5 % and 10 % by wt.) were synthesized. The reaction was carried out in batch reactor with magnetic stirring at 220 °C. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, hydrogen temperature programmed (TPR-H2), diffuse reflectance spectroscopy in ultraviolet and visible regions (DRSUV-Vis), thermogravimetric analysis (TG / DTG). Results of the catalytic evaluation showed that the benzaldehyde was converted to benzyl alcohol, toluene and benzene. Ni10Cu7.5/Hbeta catalyst presented a conversion of 84.73 %, with selectivity to toluene around 91 %, presenting higher selectivity to deoxygenated products than Ni10Cu10/Hbeta, which can be related to the higher acidic sites present in the catalyst. The bimetallic catalysts were more active than the monometallic Ni and Cu. Thus the addition of Cu can contribute to a better performance of the Ni/Hbeta catalysts in the HDO reaction.</p><p></p