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► Vanadium was introduced onto δ-aluminas modified by lithium, sodium or potassium. ► Vanadium species are preferentially located on group I element compared with the alumina surface. ...► Vanadium largely improved the rate of SO2 oxidation as well as the rate of sulfate reduction to H2S. ► The reduction of the formed sulfate to H2S was remarkably affected by the V–K proximity. ► Alumina modified by potassium exhibited the best DeSOx performance.
The location of vanadium species on δ-aluminas modified by lithium, sodium or potassium has been thoroughly investigated by means of several techniques. XRD, TPR and textural analyses showed that vanadium species are preferentially located on group I element or in its close vicinity when compared with the non-modified alumina.
Vanadium species are localized nearby lithium and potassium cations, whilst vanadium species are partially distributed between sodium and alumina support in the sodium-modified alumina. A detailed XPS study was also carried out over potassium-promoted alumina catalysts and confirmed the vanadium distribution nearby potassium.
Experiments of SOx capture and sulfate reduction to H2S were performed under realistic Fluid Catalytic Cracking (FCC) conditions with respect to the temperature of the catalyst regeneration (at 725°C) and during hydrocarbon reactions (around 575°C).
Among different alkali cation modifiers, alumina modified by potassium exhibited the best performance in the DeSOx reaction (in terms of mole of absorbed sulfur per mole of group I cation) according to the following ratios: 0.74, 0.34 and 0.24 observed for K, Li and Na, respectively.
Finally, vanadium largely improved the rate of SO2 oxidation as well as the rate of sulfate reduction to H2S.
Glyphosate, a non-selective herbicide with systemic action, is one of the most widely used substances in modern agriculture. With the objective of comparing the efficiency of glyphosate previously ...complexed with copper (Cu421) with that of the commercial product (Roundup WG®) and the purified substance (purified glyphosate) in controlling Brachiaria decumbens Stapf (signal grass), tests were conducted of the in vitro and in vivo activity of the enzymes 5-enolpyruvylshikimate-3-phosphate synthase (EPSPs) and phenylalanine ammonia lyase (PAL). The Cu421 complex significantly inhibited the EPSPs activity, as did the commercial product. In vivo test showed that treatments increased PAL activity more than double. The Cu421 complexed caused a substantial decline in the Falker chlorophyll index, as well as, the greatest reduction in the fresh mass yield and total protein concentration. In addition, the Cu 421 complexed application resulted in an increase in N-NO3- content in B. decumbens. The Cu421 complex had similar action as Roundup WG® and the purified glyphosate, indicating the possibility of using this complex to control weeds.
The interaction of VO2+ species with Mg6Al2(OH)16(CO3)·n(H2O) hydrotalcite (HTC) and the corresponding HTC‐derived mixed oxide (MO, obtained by calcination of HTC at 800 °C) is reported. Vanadium was ...loaded (2–20 wt.‐%) onto HTC and onto MO using an aqueous solution of VOSO4. After the spontaneous reaction, solids were filtered, treated at 120 °C and then characterised. The characterisation techniques used include spectroscopic, structural, textural and thermal analyses, such as FTIR, Raman, UV/Vis DRS, XRD, BET, EPR, TG/DTA and TPO/TPR. In this work, the nature of the vanadium species on HTC and MO as a function of vanadium loading was studied. The presence of VIII species in the layers of HTC and anionic VV species in the interlayers have been proposed, whereas on MO VIV species are easily oxidised by air producing oligomerised VV supported species.
Interaction of VO2+ with Mg6Al2(OH)16(CO3)·nH2O gives a hydrotalcite‐like compound containing VIII in the layers and vanadate(V) species in the interlayers. When VO2+ interacts with the mixed derived oxide, VIV is easily oxidised by air, and supported oligomerised VV species are obtained.
Among the epistemological obstacles described by Gaston Bachelard, we contend that unitary and pragmatic knowledge is correlated to the teleological categories of Ernst Mayr and is the basis for ...prevailing debate on the notion of "function" in biology. Given the proximity of the aspects highlighted by these authors, we propose to associate the role of teleological thinking in biology and the notion of unitary and pragmatic knowledge as an obstacle to scientific knowledge. Thus, teleological thinking persists acting as an epistemological obstacle in biology, according to Bachelardian terminology. Our investigation led us to formulate the "teleological obstacle," which we consider important for the future of biology and possibly other sciences.
Up to 90% of glyphosate was removed in 40 min by a 2:1 Mg
2
Al-layered double oxide (LDO) at pH 10, and the adsorption kinetics fitted a pseudo-second-order law. The adsorption isotherms were type L, ...and the Langmuir model best fitted the experimental data, with
q
max
of 158.22 μg/mg at 25 °C. The intraparticle diffusion model suggested that the adsorption process is dependent on the thickness and formation of the film at the solution/solid interface. The XRD results excluded the intercalation of glyphosate anions, and FTIR along with solid-state
13
C and
31
P MAS NMR confirmed that the glyphosate anions interact through the carboxylate and/or phosphonate moieties, both in end-on and side-on modes to the LDO surface. Glyphosate removal was also investigated in the presence of different anionic species, and simultaneous adsorption showed that carbonate and phosphate ions strongly influence glyphosate removal.
A base de Schiff (E) 5-bromo-N3-(1-(4-clorofenil)etilideno)piridina-2,3-diamina foi sintetizada, caracterizada espectroscopicamente por RMN de 1H e FT-IR/ATR e sua estrutura no estado sólido foi ...determinada por difração de raios-X de monocristal. O composto cristaliza no grupo espacial P21/n e sua unidade assimétrica é constituída de duas unidades moleculares. Os parâmetros cristalográficos foram simulados usando o método semi-empírico PM6 e o estudo de análise conformacional MMFF. Os valores de R2 obtidos para os parâmetros indicaram boa concordância dos dados e a análise conformacional indicou três confôrmeros de menor energia.
Os moluscos do gênero Pomacea estão distribuídos no município do Rio de Janeiro e outros municípios vizinhos a este, constituindo uma praga para a agricultura, sobretudo àquelas culturas de ...subsistência, que envolvem os pequenos produtores. Além disto, são incriminados como hospedeiros intermediários para Angiostrongylus cantonensis (Chen, 1935), um nematoide metastrongilídeo parasito de roedores na natureza e que ocasionalmente pode infectar o homem, causando quadros de meningoencefalite eosinofílica, podendo ser fatal, tornando-o um dos mais importantes metastrongilídeos, devido sua importância antropozoonótica. O cálcio é um metal considerado essencial na biologia de moluscos e um dos principais componentes inorgânicos que compõem as conchas desses animais. Pela importância desse íon no sucesso adaptativo de moluscos, o presente estudo teve como objetivo avaliar os efeitos da infecção experimental de A. cantonensis sobre aspectos estruturais da concha do molusco hospedeiro, variações nos conteúdos de cálcio na hemolinfa e de suas reservas na concha de P. maculata durante o período pré-patente (três semanas de infecção). Moluscos do gênero P. maculataforam infectados experimentalmente com 10.000 larvas L1 de A. cantonensis. Semanalmente, por três semanas após a exposição às larvas L1, moluscos tiveram suas conchas retiradas, sem uso de anestesia. Foram realizadas: determinação de cálcio na concha e na hemolinfa e análise das conchas in natura e calcinadas por FTIR. A infecção causou um aumento da concentração de cálcio na hemolinfa de 15,28% na primeira semana de infecção, e redução em 5,36% e 2,90% na segunda e terceira semana de infecção respectivamente. A concentração de cálcio presente na concha de P. maculata sofreu uma redução deste íon de 4,76% na primeira semana de infecção, aumento de 2,5% na segunda semana de infecção, culminando em equilíbrio no final do período pré-patente. Os espectros de FTIR das conchas in natura apresentaram bandas de absorção em regiões típicas de aragonita, diferentemente das conchas calcinadas, que apresentaram bandas de absorção semelhantes às da calcita. Os resultados obtidos até o presente momento evidenciam que P. maculata é um hospedeiro intermediário resistente para A. cantonensis, suportando uma carga larval de 10.000 L1, apresentando apenas uma pequena alteração no seu metabolismo de cálcio durante todo o período de infecção e uma taxa de mortalidade de 13,33%.
Um Outro Olhar Sobre as Ligações Hidrogênio Herbst, Marcelo Hawrylak; Monteiro Filho, Antônio Ricardo Moutinho
Química nova na escola,
2019, Letnik:
41, Številka:
1
Journal Article
The effects of the SAR (14 and 38) and of the methodology of introduction of nickel (wetness impregnation and ion exchange) on catalyst activation were investigated in Ni/USY model catalysts ...submitted to two activation treatments: reduction (A) and reduction/calcination/reduction, successively (B). the catalysts prepared by wetness impregnation, a marked increase in the catalytic activity after treatment B was observed. On the basis of the catalyst efficiency toward ethane hydrogenolysis, the lower SAR catalyst presents a threefold higher activity. On the contrary, the catalysts prepared by ion exchange, as well as a model catalyst prepared by wetness impregnation over a USY exhaustively exchanged with nickel ions, do not present measurable increasing of the catalytic activity under the same activation conditions. Monitoring the catalyst activation by EXAFS indicates the formation of nickel clusters in the impregnated catalysts after activation treatment B, which should be responsible for the high catalytic activity. However, TEM images reveal a bimodal particle size distribution, with large (ca. 20 nm) and small nickel particles. Temperature-programmed reduction performed under the same conditions of catalyst activation suggests that only the small nickel particles are activated under the experimental conditions adopted in this work.
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