Unsupervised system to classify SO2 pollutant concentrations in Salamanca, Mexico

Salamanca is cataloged as one of the most polluted cities in Mexico. In order to observe the behavior and clarify the influence of wind parameters on the Sulphur Dioxide (SO2) concentrations a Self-Organizing Maps (SOM) Neural Network have been implemented at three monitoring locations for the period from January 1 to December 31, 2006. The maximum and minimum daily values of SO2 concentrations measured during the year of 2006 were correlated with the wind parameters of the same period. The main advantages of the SOM Neural Network is that it allows to integrate data from different sensors and provide readily interpretation results. Especially, it is powerful mapping and classification tool, which others information in an easier way and facilitates the task of establishing an order of priority between the distinguished groups of concentrations depending on their need for further research or remediation actions in subsequent management steps. For each monitoring location, SOM classifications were evaluated with respect to pollution levels established by Health Authorities. The classification system can help to establish a better air quality monitoring methodology that is essential for assessing the effectiveness of imposed pollution controls, strategies, and facilitate the pollutants reduction

Dynamic states of V2O5 supported on SnO2/SiO2 and CeO2/SiO2 mixed-oxide catalysts during methanol oxidation

A series of V2O5 supported on the SnO2/SiO2 and CeO2/SiO2 mixed oxides were investigated during methanol oxidation by in situ Raman spectroscopy, and the catalytic properties of these catalysts were probed by methanol oxidation kinetic studies. The Raman studies revealed that tin oxide forms a surface SnOx overlayer on the silica surface owing to the absence of Raman features of the SnO2 crystallite, but cerium oxide forms bulk CeO2 particles on the silica surface. The impregnated vanadium oxide formed a surface vanadia overlayer on all the catalysts owing to the absence of V2O5 crystallite Raman features. In situ Raman studies of the V2O5/SnO2/SiO2 and V2O5/CeO2/SiO2 catalysts during methanol oxidation indicate that the formation of the VOx-SnOx and VOx-CeO2 interactions totally blocks the formation of surface V-OCH3 groups, which are observed in the V2O5/SiO2 catalysts. The interaction between the surface VOx and the surface SnOx overlayer on silica increases the methanol oxidation reactivity by 1-2 orders of magnitude relative to V2O5/SiO2, and partial interaction between the surface VOx and bulk CeO2 particles increases the methanol oxidation reactivity by 0-1 order of magnitude relative to V2O5/SiO2. Temperature programmed reduction (TPR) studies indicate that the reducibility of the surface vanadium oxide species is dependent on the reducibility of the specific oxide support and confirm the formation of the VOx-SnOx bonds for the V2O5/SnO2/SiO2 catalyst and the formation of VOx-CeO2 as well as VOx-SiO2 bonds for the V(2)O5(/)CeO(2)/SiO2 catalyst

In Situ Raman Spectroscopy of Supported Transition Metal Oxide Catalysts: 18O2-16O2 Isotopic Labeling Studies

The isothermal isotopic exchange reaction of 18O2 with 16O of CrO3, MoO3, Nb2O5, WO3, V2O5, and Re2O7 supported on ZrO2 has been investigated with in situ laser Raman spectroscopy. Isotopic exchange of the oxygen atoms of the supported transition metal oxides with 18O2 is difficult and requires several successive reduction-18O2 reoxidation cycles at relatively high temperatures. The Raman spectroscopy data reveal that all the supported transition metal oxides are present as a monooxo species on ZrO2. This finding is consistent with the shifts calculated from the isotopic ratios for a simple diatomic oscillator, with the corresponding infrared spectra of the same catalysts and with the vibrational frequencies of several monooxo reference compounds. On this basis, coordination models of the molecular structures are proposed for CrO3/ZrO2, MoO3/ZrO2, Nb2O5/ZrO2, WO3/ZrO2, V2O5/ZrO2, and Re2O7/ZrO2 catalysts under dehydrated conditions

In Situ Raman Spectroscopy of Supported Transition Metal Oxide Catalysts: 18O2-16O2 Isotopic Labeling Studies

The isothermal isotopic exchange reaction of 18O2 with 16O of CrO3, MoO3, Nb2O5, WO3, V2O5, and Re2O7 supported on ZrO2 has been investigated with in situ laser Raman spectroscopy. Isotopic exchange of the oxygen atoms of the supported transition metal oxides with 18O2 is difficult and requires several successive reduction-18O2 reoxidation cycles at relatively high temperatures. The Raman spectroscopy data reveal that all the supported transition metal oxides are present as a monooxo species on ZrO2. This finding is consistent with the shifts calculated from the isotopic ratios for a simple diatomic oscillator, with the corresponding infrared spectra of the same catalysts and with the vibrational frequencies of several monooxo reference compounds. On this basis, coordination models of the molecular structures are proposed for CrO3/ZrO2, MoO3/ZrO2, Nb2O5/ZrO2, WO3/ZrO2, V2O5/ZrO2, and Re2O7/ZrO2 catalysts under dehydrated conditions

Effect of synthesis pH and H2O molar ratio on the structure and morphology of aluminum phosphate (AlPO-5) molecular sieves

AlPO-5 molecular sieves were prepared by the hydrothermal reaction of a gel mixture with the following compositions: Al2O3:P2O5:Et3N:H2O = 1:1:1.5:x, where x is between 100 and 750 H2O molar ratio. The structure and morphology of the AlPO-5 molecular sieves depend on the gel mixture's composition, hydrothermal temperature, hydrothermal reaction time, and H. Without H control, the AlPO-5 structure changed from a spherical shape at H2O = 100 to a hexagonal pillar shape at H2O = 450. With pH control in the range of about 2.5-3.5, the hexagonal pillar crystals began to form at H2O = 100 and an island of hexagonal pillars with radiation form appeared at H2O = 300-450 due to the formation of a tridymite type of dense AlPO4 phase. It appears that the formation rate of hexagonal pillar crystals to form a dense AlPO4 phase is favorable under acidic conditions, and an amorphous AlPO-5 structure forms under basic conditions. Thus, the H2O concentration and pH value have a dramatic effect on the AlPO-5 structure

Amination application over nano-Mg-Ni hydrogen storage alloy catalysts

Some nano-intermetallic alloys such as Mg-Ni were prepared by a chemical reduction method (named polyol process) using ethylene glycol, polyvinyl pyrroli done (PVP 10000) and PdCl2 as reduction reagent, protect reagent, and nuclear reagent, respectively, to reduce the metal salts. The particle size of the synthetic Mg-Ni alloy was affected by the amount of the protect agent and nuclear agent and by the reduction temperature. All synthetic Mg-Ni alloys possess higher surface area about 113-315 m(2)/g and four kinds of components: Mg2Ni, Ni, Mg and MgO. The contents of Mg2Ni, Ni, Mg and MgO are affected by the Mg/Ni molar ratio. High molar ratio of Ni makes the single phase of Ni easy to reduce and results in the increase of Ni crystalline degree. The results of XRD and TEM and electron diffraction pattern indicate that PVP concentration only changes the particle size, but not the structure and composition of synthetic Mg-Ni alloys. The catalytic studies of PEG amination show that the total amine yield reaches to 58.4% over 1 g of Mg-Ni alloy with Mg:Ni = 1:2 due to the formation of more single phase of Ni. The formation of Mg2Ni alloy and MgO prevent the aggregation of Ni, and possesses a higher amination activity. (C) 2004 Published by Elsevier B.V