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El mapa mental no se puede apreciar como corresponde. Por tal motivo, se ha colocado un enlace.

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En el mapa mental se pueden encontrar propiedades del bismuto, efectos, aplicaciones, entre otras especificaciones más.

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Sign up | Miro | Online Whiteboard for Visual Collaboration

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Scalable, secure, cross-device and enterprise-ready team collaboration whiteboard for distributed teams. Join 35M+ users from around the world

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Propiedades del bismuto, desde su bajo punto de fusión, alta densidad hasta su baja toxicidad , la capacidad de expandirse al solidificar y su uso en la medicina para tratar algunas dolencias gastrointestinales

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BISMUTO: PROPIEDADES DEL METAL MÁS RARO QUE EXISTE

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La Nueva Farmacoterapia Inorganica XVI. Compuestos de Bismuto

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Se presentan aspectos de actividad farmacológica asociada a diferentes compuestos simples de bismuto. Luego se analiza en detalle los efectos del llamado "subcitrato de bismuto coloidal" en el tratamiento de las úlceras gástricas, así como las propiedades químicas y estructurales de esos preparados.

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Los diferentes tipos de uso del bismuto en la medicina

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archivos de investigacion sobre el bismuto

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archivos de investigacion sobre el bismuto

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Bismutoak eroankortasun propietate berriak erakutsi ditu

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Maia G. Vergniory ikerlariak isolatzaile topologikoen arloan egindako lanak Nature Physics aldizkariaren azala lortu du Bismutoak eroankortasun propietate berriak erakutsi ditu Ikerketa...

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Microestructura y propiedades electricas de bismuto.
El artículo presenta la fabricación de películas delgadas de bismuto y óxido de bismuto mediante la técnica de Sputtering con Magn y se enfoca en el análisis de las propiedades eléctricas de los materiales.

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Microestructura y propiedades eléctricas de bismuto y oxido de bismuto depositados por magnetrón sputtering UBM

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In this work, bismuth (Bi) and bismuth oxide (Bi2O3) thin films were prepared, at room temperature, by Sputtering Unbalanced Magnetron (UBM - Unbalance Magnetron) technique under glass substrates. Microstructural and electrical properties of the samples were studied by X-ray diffraction (XRD ) and System for Measuring Physical Properties - PPMS (Physical Property Measurement System).

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La importancia del Bismuto en el campo de la catálisis.

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Abstract

The Standard Oil of Ohio Company (SOHIO) process is the oxidation/ammoxidation of over bismuth/molybdate catalysts. Studies in the heterogeneous systems show that propene bismuth is involved in the rate-determining hydrogen abstraction from propene in both cases, and may be involved in later steps of the process as well. Model studies support the intervention of bismuth(III) in the rate-determining step and molybdenum(VI) in later steps. Few model studies with bismuth-containing compounds have been reported.

Introduction

The coordination chemistry of bismuth has applications in areas including medicine [1], materials synthesis, organic synthesis, and catalysis. In the field of catalysis, one of the most important processes involving bismuth is Standard Oil of Ohio Company (SOHIO) oxidation/ammoxidation [2]. This review will provide an overview of the SOHIO process, and describe what is known about the role of bismuth in SOHIO oxidation and ammoxidation catalysis. The goal is not to update the field since the last review, but rather to examine the evidence for the exact role (or lack thereof) of bismuth in each mechanistic step.

Section 2 will delineate the homogeneous model systems that have been described to date. Although immense research effort has been devoted to mechanistic studies of the heterogeneous system, the chemistry of homogeneous model compounds is relatively limited.

This article will focus on bismuth molybdenum oxides that utilize propene as a substrate. Although these bicomponent systems are no longer used in industry, an understanding of their chemistry is very applicable to current catalysis. Present industrial catalysts are generally multicomponent systems rather than pure Bi/Mo oxides, however it has been shown that the surface layer of these systems is made up of Bi/Mo oxides, and that the active sites comprise these two metals [3].

There is also significant interest in catalysis for the oxidation/ammoxidation of propane rather than propene. Bismuth molybdates, among other catalysts, are used for propane ammoxidation, which is of significant current industrial interest [4], [5]. Although the mechanism is necessarily more complex than that of propene ammoxidation, the dehydrogenation step is believed to occur in the gas phase to form propene [5] which is then oxidized/ammoxidized on the Bi/Mo catalyst. Bismuth molybdate catalysts must therefore be optimized for new reaction conditions in order to be suitable for propane ammoxidation.

The SOHIO process is the selective oxidation (reaction (1)) and ammoxidation (reaction (2)) of propylene to make acrolein and acrylonitrile, used in industry on large scales. In 2000, the worldwide demand of acrylonitrile alone was estimated at 5,000,000 tons per year [6].

The predominant commercial processes for acrylonitrile and acrolein production use multicomponent catalysts based on Bi ₂O ₃·MoO ₃ catalysts developed by SOHIO workers in 1959-1962 [7], [8], where incorporation of other metal additives has increased yield and selectivity. Bismuth is known to be necessary to both the rate-determining and later steps of the catalytic cycle.

Commercial interest has driven a good deal of fundamental investigation into the mechanism of the SOHIO process, usually using simple bismuth molybdate compositions rather than the more complex catalysts used industrially [2], [9], [10], [11]. Although many of the intimate details remain obscure, certain aspects of acrolein and acrylonitrile formation are well-accepted [2].

For acrolein, the overall process is believed to comprise the following steps:

For acrylonitrile, the process is believed to be similar, but with initial NH ₃ absorption and/or substitution for a terminal MoO moiety, and subsequent CN bond formation rather than CO bond formation. The preeminent mechanistic theory was proposed by Grasselli (Scheme 1) [2], [12].

Several reviews of the SOHIO process have been published [2], [9], [10], [11], [13], [14].

There has been an impressive amount of research on the mechanism of the SOHIO process over the past 40 years, yet the exact mechanistic details remain controversial. Though many ingenious studies have been carried out, there are many obstacles to the complete elucidation of the heterogeneous chemistry. Below are some reasons for the difficulty of determining mechanistic details in the "real" systems.

3.
Directly conflicting results are sometimes found in literature, for example the segregation into Bi or Mo sites reported by Otsubo and co-workers [17] and contradicted by Keulks and Matsuzaki [18] or the same [19] or different [20] amounts of incorporation in acrolein and CO ₂ produced from propene oxidation. Raman spectra taken before and after reoxidation of γ-bismuth molybate after propene reduction show three different trends in three different articles [21], [22], [23].

4.
Conclusions are often made on the basis of change in activity or selectivity when a variable is changed. However, it is not always safe to assume that such an experiment can define the role of that variable in an otherwise unchanged mechanism. For example, reduced molybdenum oxide can be reoxidized by O ₂ gas, so one may be tempted to conclude that the bismuth molybdates are reoxidized at molybdenum sites. However, bismuth oxide can also be reoxidized by O ₂ gas; it is therefore not clear which type of reoxidation mechanism applies to the bimetallic oxide.

Section snippets

Role of bismuth in the SOHIO process

The presence of bismuth in the multicomponent catalyst is vital. Grasselli stated, in a recent review of ammoxidation, "without Bi, all of the other elements mentioned above, taken separately or together, are incapable of catalyzing the ammoxidation reaction" [2]. The role(s) of bismuth has been variously described over the years. The sections below will describe the evidence for bismuth's participation in various steps of the SOHIO process.

Molybdenum/tungsten models

Chan and co-workers have shown that the addition of benzyl radical to Cr and Mo imido complexes (Eq. (3)) forms benzylidene- tert-butylamine [66], [67]. These reactions are analogous to the trapping and oxidation of allyl radical observed on MoO ₃.

They also reported the migration of an allyl group from an oxo to an imido nitrogen atom (Eq. (4)), though product distributions indicated that a competing pathway also exists (possibly migration between imido groups [65]) [67]. Osborn and co-workers

Conclusion

Homogeneous model systems have illustrated the ability of both Mo and Bi complexes to perform many of the fundamental transformations proposed to intervene in the SOHIO process. Of course, chemistry of molecular models cannot be considered as proof of any mechanistic steps in the heterogeneous system.

Bismuth is clearly vital to the SOHIO process, but it can be seen that the details of its chemistry remain unclear. Bismuth is known to play a role in rate-determining hydrogen abstraction, and may

Acknowledgements

I would like to thank the National Science Foundation (Grant # CHE 0133866) and the Welch Foundation (Grant # P-1459) for research support.

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The role of bismuth in the SOHIO process

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The Standard Oil of Ohio Company (SOHIO) process is the oxidation/ammoxidation of propene over bismuth/molybdate catalysts. Studies in the heterogeneo...

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Vista de Producción y caracterización de recubrimientos de bismuto producidos con magnetrón desbalanceado pulsado | Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales