Interface large specific

The selectivity issue has been related to multi-phase processing [31]. Nitrations include both organic and aqueous phases. Oxidation to phenol as one side reaction takes places in the organic phase, whereas all other reactions occur in the aqueous phase and are limited by organic solubility. For this reason, enhancing mass transfer by large specific interfaces is a key to affecting product selectivity. 

OS 41a] [R 19] ]P 30] A study was undertaken to compare extended (1 h) processing in small vials (2 cm ) with short-time (100 s) continuous micro reactor and mini-batch (10 cm ) operation for 10 different substrates (C4-C8 alcohols) which were reacted with rhodium(I)-tris(m-sulfophenyl)phosphane [111]. The vials were either directly filled with the two phases yielding a bilayered fluid system with small specific interfaces or by interdigital micro mixer action yielding an emulsion with large specific interfaces. 

In micro reactors, large specific interfaces between immiscible phases can in general be achieved. In special laminating contactors, a stable two-phase flow with continuous phases can be obtained, while separation of the phases is facilitated when the two separate streams leave the micro reactor as there is no dispersion. 

These devices have gas and liquid streams which do not merge, i.e. are not fed into each other. Rather, by use of separate ports both phases are passed in their own encasing, e.g. their own micro channel. Thereby, dispersion of the phases is prevented and only one large specific interface is created for mass transfer (different from dispersive micro devices, see, e.g.. Section 5.1.2). The separate guidance of the phases allows to heat the phases separately, usually from the side most distant from the gas/liquid interface. 

Especially the favorable mass transfer of micro reactors is seen to be advantageous for the oxidation of benzyl alcohol [58]. As one key to this property, the setting and knowledge on flow patterns are mentioned. Owing to the special type of microreactor used, mixing in a mini trickle bed (gas/liquid flows over a packed particle bed) and creation of large specific interfaces are special aspects of the reactor concept. In addition, temperature can be controlled easily and heat transfer is large, as the whole micro-reactor construction acts as a heat sink. 

One of the most attractive roles of liquid liquid interfaces that we found in solvent extraction kinetics of metal ions is a catalytic effect. Shaking or stirring of the solvent extraction system generates a wide interfacial area or a large specific interfacial area defined as the interfacial area divided by a bulk phase volume. Metal extractants have a molecular structure which has both hydrophilic and hydrophobic groups. Therefore, they have a property of interfacial adsorptivity much like surfactant molecules. Adsorption of extractant at the liquid liquid interface can dramatically facilitate the interfacial com-plexation which has been exploited from our research. 

An understanding of much of aqueous geochemistry requires an accurate description of the water-mineral interface. Water molecules in contact with> or close to, the silicate surface are in a different environment than molecules in bulk water, and it is generally agreed that these adsorbed water molecules have different properties than bulk water. Because this interfacial contact is so important, the adsorbed water has been extensively studied. Specifically, two major questions have been examined 1) how do the properties of surface adsorbed water differ from bulk water, and 2) to what distance is water perturbed by the silicate surface These are difficult questions to answer because the interfacial region normally is a very small portion of the water-mineral system. To increase the proportion of surface to bulk, the expanding clay minerals, with their large specific surface areas, have proved to be useful experimental materials. 

Inlerfacial Contact Area and Approach to Equilibrium. Experimental extraction cells such as the original Lewis stirred cell are often operated with a flat liquid-liquid interface the area of which can easily he measured. In the single-drop apparatus, a regular sequence of drops uf known diameter is released through the continuous phase. These units are useful for the direct calculation of the mass flux N and hence the mass-transfer coefficient for a given system. In industrial equipment, however, it is usually necessary to create a dispersion of drops in order to achieve a large specific inlerfacial area. u. defined as the inlerfacial conlael area per unit volume of two-phase dispersion. Thus the mass-lransler rale obtainable per unit volume... 

By feed of a fluid through a nozzle array, which is a plate with many tiny holes, so-called micro-plume injection into a micro channel can be achieved [51, 147]. Typically, the micro channel s floor is perforated in a section in this way and a closed-channel fraction follows for completion of mixing. Large specific interfaces can in principle be achieved depending on the nozzle diameter. This mixing concept benefits from conceptual simplicity and fits well to existing MEMS techniques. Furthermore, it consumes less footprint area and therefore does not create much dead space, which is one of the prime requirements during pTAS developments. 

T]here is a range of potentials for which a current does not flow across the interface [..., which is] electrically similar to a condenser of large specific capacity. The capacity of this condenser gives a fairly... 

The issues to be solved for direct fluorinations are heat release and mass transfer via the gas-liquid interface. Multiphase microstructured reactors enable process intensification [230,248-250,304—306]. Often geometrically well-defined interfaces are formed with large specific values, for example, up to 20 000 m2/m3 and even more. These areas can be easily accessible, as flow conditions are often highly periodic and transparent microreactors are available. For the nondispersing... 

These flows were guided into a wound delay tube for reaction with ethylene glycol/ water (60/40 wt%) and hydrogen [324,326]. Efficient mass transfer in a kinetically controlled manner was achieved by the large specific gas-liquid interfaces of the foams of up to 50000m2/m3. 

Electrolytic capacitor— (H.O. Siegmund 1921) Capacitor with a large specific capacity based on specific properties of electrochemical interfaces. The - capacity C of a condensator (- capacitor) is defined as... 

Choice of appropriate chemical reaction, which effectively exploits advantageous features of liquid microspace such as short diffusion distance, large specific interface, and small heat capacity... 

Adsorption occurs whenever a solid surface is exposed to a gas or liquid it is defined as the enrichment of material or increase in the density of the fluid in the vicinity of an interface. Under certain conditions, there is an appreciable enhancement in the concentration of a particular component and the overall effect is then dependent on the extent of the interfacial area. For this reason, all industrial adsorbents have large specific surface areas (generally well in excess of 100 m2g-1) and are therefore highly porous or composed of very fine particles. 

Kinetic studies, on the other hand, have been less extensive and systematic. This is in part because of the fine subdivision of the solids and their correspondingly large specific surface areas as well as the low rates of liquid convection in soils. Interactive phenomena at liquid-solid interfaces are usually considered sufficiently fast for local equilibrium to be maintained. Also, the fact that soils are very complex mixtures of different constituents may well have discouraged many investigators from attempting a thorough... 

A very significant characteristic of colloidally dispersed particles is their large specific surface area, which may be as large as 10 to 10 cm cm . This value increases with decreasing size of colloidal particles. Due to their internal as well as external active surface, the colloidal particles affect many important characteristics of the soil, such as its ability to bind ions, water, gases and its tendency to swelling and adhesion. This results from the fact that the most important chemical, physico-chemical and physical processes occur on phase interfaces formed between the active surface of the colloid and liquid phase, i.e. soil water. 

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