A Study of the Adsorption Properties of Single Walled Carbon Nanotubes Treated with Nitric Acid

The changes observed in the properties of Single Walled Carbon Nanotubes (SWCNTs) after treatment with nitric acid are reported. The oxidized nanotube samples were characterized morphologically by scanning electron microscopy and structurally by Raman spectroscopy, thermogravimetric analysis, infrared spectroscopy and X-ray photoelectron spectroscopy. Gas adsorption was used to study the changes in the surface properties of the samples (including the changes in their porosity), as well as the changes in the adsorbate–adsorbent interactions which occurred as a result of the acid treatment. The adsorption studies were conducted using nitrogen at 77 K and CO2 at different temperatures between 263 K and 289 K at sub-atmospheric pressures. The isosteric heat was calculated from the data obtained and indicated a higher adsorbate–adsorbent interaction for the oxidized materials. A correlation was found between morphological and structural evolution and the adsorption properties of CO2, a probe gas which appears to be very suitable for characterizing the microporosity of these kinds of materials.Fil: Garcia Blanco, Andres Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Villarroel Rocha, Jhonny. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Nazzarro, Marcelo Sandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Zgrablich, Giorgio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; Argentin

Study of the sorption properties of alkali zirconate-based sorbents at high temperature in the presence of water and low CO2 concentration

Li2ZrO3, K-doped Li2ZrO3, and mixed Li2ZrO3-Na2ZrO3 based sorbents were synthesized through wet impregnation of alkaline solutions in a suspension of zirconia nanoparticles. Structural Raman and surface XPS characterizations were performed and the zirconate reactivity was analyzed through operando Raman experiments. t-Li2ZrO3, m-Na2ZrO3, m-ZrO2, m-Li2CO3 and m-Na2CO3 phases were detected by Raman spectroscopy and XRD. Sorption tests were performed at 500 °C with low and high CO2 concentrations (15% and 50%, respectively) and 0%, 10%, 20% and 30% H2O. All samples presented good sorption properties under dry conditions and 50% CO2. The addition of growing amounts of water played a positive effect on the capture properties, mainly in experiments with 15% CO2. For the KLiZr and NaLiZr samples, the addition of 10% H2O produced a more marked increase on the capture capacity, mainly observed at lower capture times. Accordingly, an enhancement of Li2ZrO3 and Na2ZrO3 reactivity was observed in the presence of water through operando Raman measurements. Water is believed to increase the ionic mobility and, consequently, the reactivity of alkali zirconates. The multi peak CO2 TPD profiles obtained during the regeneration of the Na-Li and K-doped samples were associated with their structural and compositional properties. KLiZr presented excellent stability over 10 sorption/regeneration cycles with capture under humidified conditions (15% CO2-10% H2O), while the capture capacity of NaLiZr decreased. The loss of capture efficiency in NaLiZr could be related to structural rearranges that affected the reaction kinetics.Fil: Peltzer, Diana Jacqueline. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

The effect of the Li:Na molar ratio on the structural and sorption properties of mixed zirconates for CO2 capture at high temperature

Different Li2ZrO3-Na2ZrO3 based sorbents were synthesized by the wet impregnation of a zirconia nanoparticle suspension with a lithium carbonate solution. The solids were characterized by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy and X-ray photoelectron spectroscopy, while sorption properties were studied by thermogravimetric measurements carried out at different CO2 partial pressures. The stability experiments were carried out in a thermal programmed desorption system through 20 consecutive capture/desorption cycles. The Li-Na zirconate based-sorbents developed presented capture capacities between 0.187 and 0.211gCO2gmat-1, which represented 80-90% of their theoretical maximum capacity, and fast reaction kinetics even at low CO2 partial pressure equal to 0.1bar. The sorption properties depended on the Li2ZrO3/Na2ZrO3 ratio, which in turn depended on the Li and Na nominal content. In addition, faster desorption rates were obtained as the Li nominal contents increased. Moreover, the presence of Li in the sorbent could enhance the Na2CO3 decomposition, making these processes more efficient. Finally, the evolution of the solid and gaseous species was monitored by operando Raman spectroscopy.Fil: Peltzer, Diana Jacqueline. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

Recent advances in catalysts, palladium alloys and high temperature WGS membrane reactors: A review

There is an increasing demand for pure H2 (CO < 10 ppm) to be used in low temperature PEM fuel cells. This puts pressure on the development of alternative routes to purify the hydrogen that is produced in reformers using feedstocks such as natural gas and ethanol. A good option is the water gas shift reaction conducted in a membrane reactor to obtain ultrapure hydrogen. This contribution critically reviews the developments that took place in this decade concerning more efficient, selective, long-lasting catalysts that do not catalyze the formation of methane, graphitic and carbonaceous residues. The membranes, highly selective to hydrogen with high permeability and resistant to poisonous gases, particularly H2S, are also critically reviewed. Also included in this analysis are the different types of membrane reactors most commonly used.Fil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Lombardo, Eduardo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Development of an active, selective and durable water-gas shift catalyst for use in membrane reactors

Rh(0.6%)/La2O3 and Rh(0.6%)/La2O3(27 wt%)·SiO2 were assayed for the WGS reaction at 673 K and 1 atm. They were both more active than industrial Cr-Fe based catalysts. Rh(0.6%)/La2O3 was the most active but it progressively deactivated. To investigate its deactivation and the stability of the Rh(0.6%)/La2O3(27 wt%)·SiO2, the WGS reaction was carried out in a DRIFTS cell in operando mode. The deactivation of the former was due to the strong adsorption of intermediate oxygenates. Another disadvantage of the Rh formulations was their methanation activity. Therefore, a series of formulations containing 0.1 wt% through 1.2 wt% Pt supported on La2O3(27 wt%)·SiO2 were synthesized and catalytically evaluated in a fixed-bed reactor. The activity, methane formation and stability were carefully checked. The fresh and used catalysts were characterized through a battery of techniques including XRD, LRS and XPS. The Pt(0.1 wt%) formulation resulted the most active one per gram of platinum and negligible methanation occurred. It maintained the activity and selectivity after 155 h on stream. This catalyst was tested in a Pd-Ag membrane reactor to produce ultrapure H2 (<10 ppm of CO) that can be used to feed a low temperature PEM fuel cell. Comparing our results with those already published, it is concluded that our system is one of the best ones reported so far.Fil: Lombardo, Eduardo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Cornaglia, Carolina Andre. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Operando Raman spectroscopic studies of lithium zirconates during CO2 capture at high temperature

Li2ZrO3 based sorbents were synthesized for CO2 capture at high temperature between 500 and 700 C. Monoclinic ZrO2, tetragonal Li2ZrO3, Li2 CO3, K2CO3 and LiKCO3 phases were detected by XRD and Raman spectroscopy. The sorbents showed high stability and moderate capture efficiency. The addition of K resulted in the improvement of capture efficiency from 0.052 g CO2 g mat1 in materials without K to 0.083 g CO2 g mat1 in the doped solid. Here, we report an experimental setup of Raman spectroscopy coupled with online mass spectrometry and a demonstration of its capabilities using lithium zirconates as sorbents for high temperature CO2 capture. Operando Raman spectroscopy allowed us to follow up the phase evolution during the capture process for the first time. The results obtained confirmed the presence of molten K and Li carbonates when the K-doped zirconates wereexposed to CO2 at 500 C.Fil: Peltzer, Diana Jacqueline. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

In situ characterization of phase transformation and reactivity of high surface area lanthanum-based Ru catalysts for the combined reforming of methane

A lanthanum oxycarbonate phase (La2O2CO3) with high surface area was prepared as support of Ru catalysts. The metal was added by wet impregnation or incorporated during the oxycarbonate synthesis. The reactivity of the lanthanum and ruthenium species was studied through in situ Raman under dry reforming of methane conditions with and without oxygen addition. When Ru was incorporated by wet impregnation, the solid showed a higher reactivity of lanthanum oxycarbonate to the formation of La2O3 in a hydrogen flow even at low temperatures while RuOx was completely reduced at 400 °C. It was also found that the reduced ruthenium species could be re-oxidized by CO2 at the reaction temperature (550 °C). Under the dry reforming of methane, the metallic Ru did not change its oxidation state and the formation of graphitic carbon and oxycarbonate was observed. With the addition of oxygen, the same phase transformation occurred as in the case of the dry reforming of methane. However, the re-oxidation of Ru0 species was observed through in situ Laser Raman spectroscopy and pseudo in situ XPS measurements. These measurements allowed us to advance in the understanding of the solid transformations produced during methane reforming reactions.Fil: Faroldi, Betina María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Nanoparticles in the Water– Gas Shift Reaction and Steam Reforming Reactions

Nanomaterials typically display distinctive properties that are determined by their size and shape. The employment of advanced characterization and synthesis techniques has led to the development of new nanostructured materials for catalysis applications.1 This strategy aims to have a significant impact on environmental applications and on the production of hydrogen (H2) as a clean energy carrier. Catalysts formed by metallic or oxidic nanoparticles (NPs) highly dispersed on supports are usually very complex materials, and their size-dependent properties can be systematically designed leading to new catalysts with enhanced performance. Numerous catalysts based on noble metals such as Rh, Pt, Ir, Pd and Ru, as well as on non-noble metals such as Co, Ni and Cu have been studied for H2 producing reactions such as methane (CH4) reforming, steam reforming of ethanol (C2H5OH) and the water?gas shift (WGS) reaction.Fil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Faroldi, Betina María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin

Raman studies of Rh and Pt on La2O3 catalysts used in a membrane reactor for hydrogen production

Rh and Pt catalysts supported on lanthanum oxide were prepared by wet impregnation. The solids were used in a Pd-Ag membrane reactor to produce hydrogen through the carbon dioxide reforming of methane. The effect of the sweep gas flow rate and W/F upon the conversions of CO2 and CH 4, as well as on the production of H2 was studied. The best performing catalyst was Rh (0.6%). It yielded a methane conversion 38% higher than the thermodynamic value and the highest H2 permeate flux across the membrane. Lanthanum phases on the support and the catalysts were characterized by Laser Raman spectroscopy, FTIR, and XRD. The support and the calcined fresh catalysts exhibited a mixture of phases which were influenced by the metal type. Furthermore, platinum seemed to favor the formation of Ia-La2O2CO3 after a short treatment in flowing CO2. However, the only remaining crystalline phase after 100h on stream was II-La2O2CO3. A small amount of graphitic carbon was detected using Laser Raman spectroscopy, despite the fact that no carbon deposition was observed through TGA measurements. The graphite crystallization order seemed to be dependent upon the contact time of the reactants.Fil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Irusta, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Lombardo, Eduardo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Optimal Pt load of a Pt/La2O3·SiO2 highly selective WGS catalyst used in a Pd-membrane reactor

Pt(wt%)/La2O3(27)·SiO2 catalysts with wt% = 0.02 up to 1.2 were synthesized and tested in a conventional fixed-bed reactor. In differential mode, the Pt(0.1)/La2O3(27)·SiO2 catalyst showed higher activity per gram of Pt than the other solids. XPS showed the presence of only surface metallic platinum, in both the fresh and used Pt(0.1 wt%) formulation, which could be responsible for the high catalytic activity. At higher Pt loads both Ptδ+ and Pt° species were present at the surface. The presence of La2Si2O7 in all solids was detected by XRD. Graphitic carbon in the used catalysts was not detected through laser Raman spectroscopy. Different catalytic tests were carried out in a tubular Pd-membrane reactor feeding a reformer outlet type stream with a molar composition of 40% H2, 40% H2O, 12% CO2 and 8% CO. They were performed between 673 and 723 K and at pressures ranging from 100 kPa to 800 kPa. At 723 K and 800 kPa, the CO conversion and H2 recovery values were 96% and 88%, respectively. A stability test including several start-up and shut-down cycles showed high stability of the Pt(0.1) catalyst.Fil: Cornaglia, Carolina Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Tosti, Silvano. ENEA. Unità Tecnica Fusione; ItaliaFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Lombardo, Eduardo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin