Multi-functional units

Hall et alP discuss the use of cross-corrugated membrane modules, illustrated in Figure 20.24, as offering the potential for developing multi-functional units for performing both reactions and product separation in one miniaturised module. The use of microporous... 

In its present configuration the HiGee rotating packed-bed concept only applies the elevated acceleration to the mass transfer elanent of a distillation operation. However, it is worth noting that the associated reboiler and condenser functions both involve multiple phases. They could therefore benefit from inclusion within the rotor, leading to a peripheral reboiler and a central condenser. This would lead to a further development of the PI strategy by the provision of multi-functional units, see Figure 6.8. 

In the reverse flow type, the hydrotreater reactor is fed with fresh and recycled feeds, and is operated to accomplish partial conversion of that combined feed in the first stage. A graded HDT-HCK bed or a multi-functional catalyst can be used in the first stage. A very effective H2 separation is used for the first-stage effluent gas. A bottoms fractionator or an adsorption unit is used for removal of heavy PAHs. Carbon adsorption extends the catalyst life. The liquid product of the first reactor is mixed with a mixture of fresh and recycled H2. The whole second stage effluent is hydrotreated in the first stage. 

The oligo- or multi-functional core unit also plays a role in determining the space occupied by a dendrimer. The core itself can exercise a function, as demonstrated by metallodendrimers (see Section 4.1.11), in which the metal ion core in a supramolecular or coordinatively constructed architecture coordinates with the surrounding branching units - and in this way can influence catalytic and photochemical processes. 

In 2002, Sasai et al. reported the synthesis of dendritic heterobimetal-lic multi-functional chiral catalysts, containing up to 12 l,l/-bi-2-naphthol (BINOL) units at their terminal positions (Fig. 9) [30]. On treating these functionalized dendrimers with AlMe3 and n-Buli, insoluble metallated Al-Ii-bis(binaphthoxide) generation x (GX-ALB) catalysts were obtained, which showed moderate catalytic activity in the asymmetric Michael reaction of 2-cyclohexenone with dibenzyl malonate (Scheme 4). 

The combination of an efficient control over the environment of the active sites in a multi-functional catalyst and its immobilization within an insoluble macromolecular support was pioneered by Seebach et al. In their approach, the chiral ligand to be immobilized was placed in the core of a polymerizable dendrimer, followed by copolymerization of the latter with styrene as shown in Scheme 9 [58]. In this way, no further cross-finking agent was necessary, since the dendrimer itself acted as cross-linker. The dendritic branches are thought to act as spacer units, keeping the obstructing polystyrene backbone... 

Figure 3 indicates the complete flowsheet of the multi-purpose high pressure extraction plant. In the following its functional units are described in more detail. 

The importance of stratigraphic studies and the identification of sedimentary units at extensively disrupted sites like Hierakonpolis can be illustrated by the excavations at locality II, where there is evidence for habitation (trash mounds and pottery) as well as industry (pottery kilns). This locality ofiered a unique opportunity to study Predynastic ecology because of the excellent state of organic preservation in an area where there was a clustering of multi-functional components (6,14). Four test pits were dug in one area through the site, in the direction NIO °E-SIO °W. The correlation profile is shown in Figure I. The oldest unit identified was Nile silt (Masmas formation). In some areas, this silt was covered by eolian and/or wadi sands, which probably represents a local feature of sand accumulation under arid to semiarid conditions. 

In addition, in the field of dewaxing (gas oils, HDC residues, lubricating oil, etc.), synthesis of novel molecular sieves with better adsorption and separation abilities is highly desired. In the past 20 years, thanks to the discovery of many molecular sieves with new compositions and structural features [secondary building units (SBUs) and pores], there have appeared a number of new application fields for molecular sieves, such as basic catalysis, extra-large microporous molecular sieve catalysis, redox catalysis, asymmetric catalysis, and dual- and multi-functional catalysis.1-201 All of these will lay a further solid foundation for the development of molecular sieves in catalysis, adsorption, and separation. 

A. Muller, P. Kogerler, and C. Kuhlmann, A variety ofcombinatorially linkable units as disposition from a giant icosahedral keplerate to multi-functional metal-oxide based network structures, Chem. 

A. van der Werf, E. Aerts, M. Peek, J. van Meerbergen, P. Lippens, and W. Verhaegh. Area optimization of multi-function processing units. In Proc. IEEE Int. Conf. Comp. Aided Design, Santa Clara CA, pages 292-299, Nov 1992. 

For each of these intensification challenges, the objective to be reached (volume reduction, reduced size/capadty ratio, etc.), and also the constraints (fixed productivity, fixed performance, quality specifications, etc.) can be identified and quantified with respect to technical and economic data. Unfortunately, the means to tackle these issues are much more complex to define since they can be of very different natures operating conditions (temperature, pressure, concentrations, etc.), physical or chemical parameters (solvents, catalysts, etc.), equipment (heat exchangers, mixers, columns, etc.), process parameters (reflux ratio, feed strategy of semi-batch reactors, separate unit operations or multi-functional reactors, separator types, etc.). In... 

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