Behavior of different soot combustion catalysts under NOx/O2. Importance of the catalyst–soot contact

Four different catalysts (Pt/Al2O3, Ce0.8Zr0.2O2, PrO2−x and SrTiCuO3) have been investigated on a laboratory scale to evaluate their potential as diesel soot combustion catalysts under different experimental conditions, which simulate the situation found in a continuous regeneration technology trap (dual-bed configuration of catalyst and soot) or a catalyst-coated filter system (single-bed configuration, both catalyst and soot particles mixed under loose-contact mode). Under dual-bed configuration, the behavior of the catalysts towards soot combustion are very similar, despite the differences observed in the NO2 production profiles. However, under single-bed configuration, there are important differences in the soot combustion activities and in the NO2 slip profiles. The configurations chosen have an enormous impact on CO/(CO + CO2) ratios of combustion products as well. The most active catalyst under NOx + O2 is PrO2−x combining a high contribution of active oxygen-assisted soot combustion as well as high NO2 production activity along the catalytic bed.Financial support of Generalitat Valenciana (Prometeo/2009/047 project) and the Spanish Ministry of Science and Innovation (project CTQ2012-30703, which is co-funded by FEDER resources). N. G. H. wishes to thank Generalitat Valenciana her Ph.D. grant within VAL i+d Program

Pt–Sn/C catalysts prepared by sodium borohydride reduction for alcohol oxidation in fuel cells: Effect of the precursor addition order

A series of Pt–Sn/C catalysts used as anodes during ethanol oxidation are synthesized by a deposition process using NaBH4 as the reducing agent. The order in which the precursors are added affects the electrocatalytic activity and physical-chemical characteristics of the bimetallic catalysts, where the Pt–Sn catalyst prepared by co-precipitation of both metals functions best below a potential of 0.5 V and the catalyst prepared by sequential deposition of Sn and Pt (drying after Sn addition) is most active above a potential of 0.5 V. The electrochemical behavior of catalysts during ethanol oxidation in an acidic medium are characterized and monitored in a half-cell test at room temperature by cyclic voltammetry, chronoamperometry and anode potentiostatic polarization. Catalyst structure and chemical composition are investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). This behavior presented for best Pt–Sn catalyst can be attributed to the so-called bifunctional mechanism and to the electronic interaction between Pt and Sn.The authors thank the Brazilian National Council of Technological and Scientific Development-CNPq (grants: 303630/2012-4, 402243/2012-9 and 310282/2013-6) for the scholarships and financial support for this work

BaTi1−xCuxO3 perovskites: The effect of copper content in the properties and in the NOx storage capacity

BaTi1−xCuxO3 perovskites have been prepared by the Pechini's sol-gel method and the effect of copper in the structural and physico-chemical properties of the perovskites and in the performance of the catalysts for NOx storage has been studied. XRD and Raman spectroscopy results indicate that all the copper containing catalysts present a distortion of the original tetragonal structure due to the incorporation of copper into the lattice. The XPS and H2-TPR results reveal that the copper catalysts, except for BaTiCu0,5 catalyst, present two copper species (with different electronic interaction with the perovskite) and active surface oxygen species. Additionally, it seems that the fraction of copper with a strong electronic interaction with the perovskite or incorporated into the perovskite structure increases with the copper content. The active sites created on the BaTi1−xCuxO3 perovskite surface bring to the catalysts activity for the NO to NO2 oxidation and for the NOx adsorption. The NOx storage capacity increases with the copper content and reaches a limit for the BaTiCu2 catalyst (300 μmol/g, at 420 °C) which is within the range of the values reported for the noble metal-based catalysts.The authors thank to Spanish Government (MINECO projectCTQ2012-030703) and to Generalitat Valenciana (project PROM-ETEOII/2014/010) for the financial support

Methanol Electro-Oxidation on Carbon-Supported PtRu Nanowires

One of the key objectives in fuel cell technology is to improve the alcohol oxidation efficiency of Pt-based catalysts. A series of carbon-supported PtRu nanowires with different concentrations of Pt and Ru were prepared for application in methanol oxidation in acid media. The physicochemical properties and electrocatalytic activity of these catalysts during methanol oxidation are function on their structure, morphology and composition. A Pt60Ru40/C catalyst shows the best behaviour towards methanol electro-oxidation allowing decrease the onset potential approximately 0.2 V respect to others PtRu/C synthesised nanowires. The structural modification of Pt by Ru and synergetic character of RuPt are main factors that could contribute to reduction of energy necessary for electro-oxidation process. The Pt and PtRu nanowires have different sizes and distribution on the substrate. The average crystallite sizes, found by XRD, are in the 4.6–5.9 nm range and the lattice parameter is between 0.3903–0.3908 nm. Small differences with the values of the Pt/C catalyst were found. The XPS results show a prevailing presence of metallic Pt and Ru4+ species.The authors thank to CNPq (grants: 304419/2015-0, 402243/2012-9, 400443/2013-9, 407274/2013-8 and 310282/2013-6), CAPES and FAPITEC for the scholarships and financial support

Tailoring the properties of BaTi0.8Cu0.2O3 catalyst selecting the synthesis method

The effect of the synthesis method (hydrothermal and sol-gel) on the properties of BaTi0.8Cu0.2O3 perovskites as catalysts for NOx and soot removal has been analyzed. X-ray powder diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), ICP-AES, N2 adsorption at −196 °C, Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and temperature programmed reduction with hydrogen (H2-TPR) have been used for catalysts characterization. To test their catalytic activity, NOx storage and soot combustion temperature programmed reaction tests have been carried out. The results allow to conclude that the synthesis method determines the position of copper on the perovskite structure and, therefore, the catalytic applications. When the hydrothermal method is used the copper is highly dispersed on the perovskite surface, obtaining a catalyst with a high activity for the NO to NO2 oxidation reaction, which can be used as oxidation catalyst for soot removal. Nevertheless, using the sol-gel method, copper is incorporated into the perovskite structure and, consequently, the catalyst presents a high NOx storage capacity.The authors thank the Spanish government (MINECO project CTQ2015-64801-R) for the financial support and Vicente Albaladejo Fuentes thanks the University of Alicante for his Ph.D. grant

Heterogeneous Photocatalytic Degradation of Ibuprofen Over TiO2–Ag Supported on Activated Carbon from Waste Tire Rubber

In recent years it has been discovered that some common use medicines, such as ibuprofen and other nonsteroidal anti-inflammatory drugs, are found in water sources in concentrations that have the potential to affect aquatic organisms. On the other hand, waste used tires are a massive problem for the environment due to the leaching of toxic compounds to soils and water. Also, the exposition to environmental conditions can make them sources of vectors like mosquitoes. In this work, three activated carbon (AC) catalysts derived from waste tire rubber, titanium dioxide and silver were synthesized using the sol–gel method. Morphological characterizations such as SEM and TEM were performed in which, the agglomeration of titanium particles and silver crystals on the surface of the AC is evident. In the XRD analysis, the presence of elemental silver nanoparticles was detected. In the diffuse reflectance spectroscopy analysis, the decrease in the titanium band gap, as well as activity in the visible spectrum, was observed. The photocatalytic tests were performed at pH 3 and 7 in the presence of UV/Vis radiation. These tests show that there are differences between the catalyst in both, UV and visible regions. Adsorption is a major phenomenon for the removal of ibuprofen, followed by photolytic decomposition. In visible spectra, the catalysts show a good performance for the removal of ibuprofen

Cu/Al2O3 catalysts for soot oxidation: Copper loading effect

Cu/Al2O3 catalysts with metal loading from 0.64 to 8.8 wt.% have been prepared and characterized by different techniques: N2 adsorption at −196 °C (BET surface area), ICP (Cu loading), XRD, selective copper surface oxidation with N2O (Cu dispersion), TPR-H2 (redox properties), and XPS (copper surface species). The catalytic activity for soot oxidation has been tested both in air and NOx/O2. The activity in air depends on the amount of easily-reduced Cu(II) species, which are reduced around 275 °C under TPR-H2 conditions. The amount of the most active Cu(II) species increases with the copper loading from Cu_1% to Cu_5% and remains almost constant for higher copper loading. In the presence of NOx, the first step of the mechanism is NO oxidation to NO2, and the catalytic activity for this reaction depends on the copper loading. For catalysts with copper loading between Cu_1% and Cu_5%, the catalytic activity for soot oxidation in the presence of NOx depends on NO2 formation. For catalysts with higher copper loading this trend is not followed because of the low reactivity of model soot at the temperature of maximum NO2 production. Regardless the copper loading, all the catalysts improve the selectivity towards CO2 formation as soot oxidation product both under air and NOx/O2.MEC (project CTQ2005-01358); FELS thanks University of Alicante (International Cooperation Office) his thesis grant

Separación de ácido láctico por destilación reactiva

El estudio realizado, tiene como finalidad demostrar las bondades del proceso de destilación reactiva respecto de otro tipo de procesos (p.e.ultrafiltración, microfiltración, extracción reactiva, etc.) para la separación de ácido láctico. Además se aplica un novedoso método corto, llamado “Análisis de la Estática” para el diseño de la mejor configuración de la columna, que permite la separación de ácido láctico por hidrólisis del lactato de metilo. Subsecuentemente, se realiza la simulación de la columna en Aspen Plus partiendo de la información suministrada por el análisis de la estática, con el fin de optimizar los parámetros de operación de la misma

Separación de ácido láctico por destilación reactiva

The purpose of this study is to demonstrate the main advantages of reactive distillation process over other processes (p.e. ultrafiltration, microfiltration, reactive extraction, etc.) for lactic acid separation. Aditionally a new short method called “analysis of the statics” is applied to the design of the best column configuration, allowing optimal lactic  acid separation by hydrolysis of methyl lactate. Subsequently, the simulation of the column is made in Aspen Plus based on the informationprovided by the analysis of the statics, with the purpòse of optimizing the static operating parameters.El estudio realizado, tiene como finalidad demostrar las bondades del proceso de destilación reactiva respecto de otro tipo de procesos (p.e.ultrafiltración, microfiltración, extracción reactiva, etc.) para la separación de ácido láctico. Además se aplica un novedoso método corto, llamado “Análisis de la Estática” para el diseño de la mejor configuración de la columna, que permite la separación de ácido láctico por hidrólisis del lactato de metilo. Subsecuentemente, se realiza la simulación de la columna en Aspen Plus partiendo de la información suministrada por el análisis de la estática, con el fin de optimizar los parámetros de operación de la misma

Potassium-copper perovskite catalysts for mild temperature diesel soot combustion

The activity and stability of potassium-copper perovskite catalysts for soot combustion were analysed at 450 °C in a NOx/O2 gas mixture. Both impregnated (K-Cu/SrTiO3) and substituted (SrKTiCuO3) copper-potassium catalysts were prepared. For comparative purpose, also a potassium substituted catalyst (SrKTiO3) was studied. The high activity of the fresh potassium catalyst (SrKTiO3) is based on the volatile potassium species reaching the surface of soot. However, this catalyst is not useful because potassium is progressively lost during the reaction. Potassium was stabilized by copper and, as a consequence, the two potassium-copper perovskite catalysts present a constant activity for the soot combustion. The activity of the potassium-copper perovskite catalysts, which is maintained during consecutive reactions, is related to their NO2 production capacity. The metal addition method seems to influence the catalysts performance, the substituted catalyst (SrKTiCuO3) being the most active and stable.The authors gratefully acknowledge the financial support of the Spanish Government (MINECO, Project CTQ2012-030703) and of the FEDER funding