Multi-scale Architecture

Multi-scale processing may be done for reasons other than to control exothermic reactions, e.g. for staged post-mixing, to have different process parameter levels along the reaction path (stage-wise change of temperature, pressure, etc.) or to combine various unit operations with different demands on process 

Ehrfeld, V. Hessel, H. Lowe, Microreactors, Wiley-VCH Verlag GmbH, Weinheim, 2000. 

Hessel, C. Serra, H. Lowe, G. Hadziioannou, Polymerizationen in mikrostrukturierten Reaktoren Ein Uberblick. Chem. Ing. Tech., 2005, 77 (11), 1693-1714. 

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This class of hybrid components comprises chip micro-reactor devices, as described in Section 4.1.3, connected to conventional tubing. This may be H PLC tubing which sometimes has as small internals as micro channels themselves. The main function of the tubing is to provide longer residence times. Sometimes, flow through the tube produces characteristic flow patterns such as in slug-flow tube reactors. Chip-tube micro reactors are typical examples of multi-scale architecture (assembly of components of hybrid origin). 

The methods discussed here merely represent the beginning of increasingly complex computational architectures, where more than one QM method may be combined with other QM methods, MM methods, continuum electrostatic approaches and coarse-grained models in a coherent multi-scale framework. With such developments, increasingly complex chemical and biological systems can be analyzed computationally in a routine and realistic fashion. 

A final example might be offered in the case of melt rheology. The local constitutive behaviour is complex enough as a function of molecular architecture and its distribution, but the behaviour of such a melt in a complex processing flow has as much effect on the properties via frozen-in orientation and predisposition of the semi-crystalline morphology. A multi-scale approach to this problem is the focus of a large UK-based collaboration. ... 

The dendritic architectures, as highly branched and three-dimensional macromolecules that have unique chemical and physical properties, offer potential as the next great technological revolutioa This review gives a brief introduction to some of the stmctural properties and application of dendritic polymer in various fields. The focus of the paper is a survey of multi-scale modehng and simulation techniques in hyper-branched polymer and dendrimers. Results of modehng and simulation calculations on dendritic architecture are reviewed. 

Intensive studies in the area of dendritic macromolecules, which include applied research and are generally interdisciplinary, have created a need for a more systematic approach to dendritic architectures development that employs a multi-scale modeling and simulation approach. A possible way is to determine the atomic-scale characteristics of dendritic molecules using computer simulation and computational approaches. Computer simulation, as a powerful and modem tool for solving scientific problems, can be performed for dendritic architectures without synthesizing them. Computer simulation not only used to reproduce experiment to elucidate the invisible microscopic details and further explain experiments, but also can be used as a useful predictive tool. Currently, Monte Carlo, Brownian dynamics and molecular dynamics are the most widely used simulation methods for molecular systems [5]. 

Multi-Scale Modeling and Simulation of Dendritic Architectures New Horizons 35... 

A key aspect of metal oxides is that they possess multiple functional properties acid-base, electron transfer and transport, chemisorption by a and 7i-bonding of hydrocarbons, O-insertion and H-abstraction, etc. This multi-functionality allows them to catalyze complex selective multistep transformations of hydrocarbons, as well as other catalytic reactions (NO,c conversion, for example). The control of the catalyst multi-functionality requires the ability to control not only the nanostructure, e.g. the nano-scale environment around the active site, " but also the nano-architecture, e.g. the 3D spatial organization of nano-entities. The active site is not the only relevant aspect for catalysis. The local area around the active site orients or assists the coordination of the reactants, and may induce sterical constrains on the transition state, and influences short-range transport (nano-scale level). Therefore, it plays a critical role in determining the reactivity and selectivity in multiple pathways of transformation. In addition, there are indications pointing out that the dynamics of adsorbed species, e.g. their mobility during the catalytic processes which is also an important factor determining the catalytic performances in complex surface reaction, " is influenced by the nanoarchitecture. 

Some simple biphenols equipped with methyl groups, e.g., 3,3, 5,5 -tetramethyl-2,2 -biphenol 38, have attracted attention as important components of highly potent ligand systems [75-86]. Remarkably, the sustainable synthesis of such biphenols is rather challenging despite their simple scaffolds. In particular, methyl-substituted phenols are prone to side reactions. This is especially the case when 2,4-dimethyl-phenol (37) is oxidatively treated. Upon anodic conversion 37 is preferably transformed into polycyclic architectures [87]. Direct electrolysis in basic media provided only traces of the desired biphenol 38 and the dominating components of the product mixture consisted of Pu in meter s ketone 39 and the consecutive pentacyclic spiro derivative 40 [88]. For an efficient electrochemical access to 3,3, 5,5 -tetramethyl-2,2,-biphenol (38) we developed a boron-based template strategy [89, 90]. This methods requires a multi-step protocol but can be conducted on a multi-kilogram scale (Scheme 17). 

An actual breakthrough is to design both the microstructure (grain size, porosity,...) of the different system materials (support-membrane-catalyst) and the reactor architecture in order to obtain improved permeation properties and stability during the time on stream [19]. Considering all the parameters, a special consideration was given in this paper to the stack of the different materials at different length scale, from the microscopic-scale (microstructure) to the assembly of materials on the whole reactor thickness (architecture). An example of the architecture/microstructure concept was used in the Multi Electrode Assembly (MEA) approach. 

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