scholarly journals Recoverable catalysts. Ultimate goals, criteria of evaluation, and the green chemistry interface

2001 ◽  
Vol 73 (8) ◽  
pp. 1319-1324 ◽  
Author(s):  
John A. Gladysz

Attempts are made to define the "ideal synthesis", "ideal catalyst", and "ideal recoverable catalyst". Although these unattainable limits can never be realized, they help to focus attention on attributes chemists should strive for. Criteria for evaluating catalyst recovery are analyzed, and increased attention to the critical and constructive evaluation of competing "green" chemical technologies is advocated.

2018 ◽  
Vol 90 (2) ◽  
pp. 337-351 ◽  
Author(s):  
Lucio Ronchin ◽  
Claudio Tortato ◽  
Alessio Pavanetto ◽  
Mattia Miolo ◽  
Evgeny Demenev ◽  
...  

Abstract Precious metal catalyst has been prepared by conventional wet impregnation method followed by precipitation and reduction with hydrogen finally passivated with water in air. The magnetically recoverable catalyst has been prepared starting from a stoichiometric Fe3O4 and ZrO2–Fe3O4 as supports prepared following a sequential precipitation procedure. Precious metal catalysts supported on carbon, alumina, magnetite and zirconia-magnetite nanocomposite has been used in the reduction of nitrobenzenes and acetophenone by using sodium and potassium formate as reducing agent in the presence and in absence of an aqueous phase. In addition, the same catalysts has been tested in CO2 and NaHCO3 hydrogenation, for verifying their potentiality in the CO2 as hydrogen carrier for hydrogenation processes.


Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3415
Author(s):  
Daniel P. Otto ◽  
Melgardt M. de Villiers

In 2020, the world is being ravaged by the coronavirus, SARS-CoV-2, which causes a severe respiratory disease, Covid-19. Hundreds of thousands of people have succumbed to the disease. Efforts at curing the disease are aimed at finding a vaccine and/or developing antiviral drugs. Despite these efforts, the WHO warned that the virus might never be eradicated. Countries around the world have instated non-pharmaceutical interventions such as social distancing and wearing of masks in public to curb the spreading of the disease. Antiviral polysaccharides provide the ideal opportunity to combat the pathogen via pharmacotherapeutic applications. However, a layer-by-layer nanocoating approach is also envisioned to coat surfaces to which humans are exposed that could harbor pathogenic coronaviruses. By coating masks, clothing, and work surfaces in wet markets among others, these antiviral polysaccharides can ensure passive prevention of the spreading of the virus. It poses a so-called “eradicate-in-place” measure against the virus. Antiviral polysaccharides also provide a green chemistry pathway to virus eradication since these molecules are primarily of biological origin and can be modified by minimal synthetic approaches. They are biocompatible as well as biodegradable. This surface passivation approach could provide a powerful measure against the spreading of coronaviruses.


Author(s):  
Andrey E. Bochkarev

There is no way to identify an animate object other than to describe its specific characteristics which necessarily look like deviations from the normal “average” pattern, named here paragon, in which the Axiological Standard of a human group is fixed. Of particular heuristic interest is, in this regard, the logical pattern, often used in Russian for describing such a deviation: (he/she is) not A, but B, in which a human creature is being denied the property of being human, but is assimilated to fire, flint, rag, chump, mouse, dough, etc. The variety of descriptions (pseudo-identifications) is explained by his or her need to focus attention on some remarkable feature of person’s character, incompatible with the paragon of accepted traits included in it as a result of the evaluation responses of his or her fellow countrymen. Although they have a greater illocutionary force than a simple statement of a deviant property, these identifications cannot be checked for “truth”, in particular, for compliance with the “real” state of things. They are pseudo-identifications which can only be verified for compliance with some kind of attitude, defining what properties should be used to qualify a person and what should be the ideal sample selected as an auxiliary object in an ideal scenario.


2001 ◽  
Vol 73 (8) ◽  
pp. 1243-1246 ◽  
Author(s):  
Thomas E. Graedel

Green chemistry does not operate as an isolated subsystem, but within higher levels of corporation and society. From an environmental standpoint, the ideal focus is to achieve optimum performance across the system, not at a single systems level. This paper proposes a four-level system for green chemistry and provides examples of performance at each level that can legitimately be termed sustainable.


Author(s):  
M.S. Shahrabadi ◽  
T. Yamamoto

The technique of labeling of macromolecules with ferritin conjugated antibody has been successfully used for extracellular antigen by means of staining the specimen with conjugate prior to fixation and embedding. However, the ideal method to determine the location of intracellular antigen would be to do the antigen-antibody reaction in thin sections. This technique contains inherent problems such as the destruction of antigenic determinants during fixation or embedding and the non-specific attachment of conjugate to the embedding media. Certain embedding media such as polyampholytes (2) or cross-linked bovine serum albumin (3) have been introduced to overcome some of these problems.


Author(s):  
R. A. Crowther

The reconstruction of a three-dimensional image of a specimen from a set of electron micrographs reduces, under certain assumptions about the imaging process in the microscope, to the mathematical problem of reconstructing a density distribution from a set of its plane projections.In the absence of noise we can formulate a purely geometrical criterion, which, for a general object, fixes the resolution attainable from a given finite number of views in terms of the size of the object. For simplicity we take the ideal case of projections collected by a series of m equally spaced tilts about a single axis.


Author(s):  
R. Beeuwkes ◽  
A. Saubermann ◽  
P. Echlin ◽  
S. Churchill

Fifteen years ago, Hall described clearly the advantages of the thin section approach to biological x-ray microanalysis, and described clearly the ratio method for quantitive analysis in such preparations. In this now classic paper, he also made it clear that the ideal method of sample preparation would involve only freezing and sectioning at low temperature. Subsequently, Hall and his coworkers, as well as others, have applied themselves to the task of direct x-ray microanalysis of frozen sections. To achieve this goal, different methodological approachs have been developed as different groups sought solutions to a common group of technical problems. This report describes some of these problems and indicates the specific approaches and procedures developed by our group in order to overcome them. We acknowledge that the techniques evolved by our group are quite different from earlier approaches to cryomicrotomy and sample handling, hence the title of our paper. However, such departures from tradition have been based upon our attempt to apply basic physical principles to the processes involved. We feel we have demonstrated that such a break with tradition has valuable consequences.


Author(s):  
G. Van Tendeloo ◽  
J. Van Landuyt ◽  
S. Amelinckx

Polytypism has been studied for a number of years and a wide variety of stacking sequences has been detected and analysed. SiC is the prototype material in this respect; see e.g. Electron microscopy under high resolution conditions when combined with x-ray measurements is a very powerful technique to elucidate the correct stacking sequence or to study polytype transformations and deviations from the ideal stacking sequence.


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