Honeycomb channel structure

Fig. 3. Schematic of the flow through (a) a honeycomb catalyst structure and (b) a cross section of a honeycomb channel.

N—H 0 hydrogen bonds and are interlinked by the syrc-N—H 0 hydrogen bonds. (Reprinted from [9] with permission from A AAS) (b) Van der Waals cross-section of the cavity in the urea channel compared with the size of /3-octane (left), benzene (top), 3-methylheptane (right) and 2,2,4-trimethylpentane (bottom), (c) chemical structures of urea and thiourea, (d) packing of urea channels to give the honeycomb-like structure of hexagonal urea. 

Among the inorganic open-framework compounds, the family of phosphates is a large one [3]. A large variety of open-framework metal phosphates of different architectures have been synthesized in the last few years. They include one-dimensional (ID) linear chain and ladder structures, two-dimensional (2D) layer structures and three-dimensional (3D) channel structures [4]. In the linear chain and ladder structures, four-membered metal phosphate units of the type M2P2O4 share comers and edges respectively. Zero-dimensional four-membered zinc phosphates have been synthesised and characterized recently [5]. Several open-framework metal carboxylates have also been reported [6] and the presence of a hierarchy of zinc oxalates covering the monomer, dimer, chain, honeycomb-layer and 3D structures has indeed been established [7]. 

All the monolith composites were prepared at a 1 1 ratio between the magnesium silicate clay binder and the AC or alumina. After premixing of the dry powders by careful addition of water a dough was formed. This dough was extruded as honeycomb monolithic structures with parallel channels of square section at a cell density of 8 cells cm and a wall thickness of 0.9 mm using a Bonnot single screw extruder. 

Many commercial ceramic membranes nowadays come in the form of a monolith consisting of multiple, straight channels parallel to the axis of the cylindrical structure (Figure 3.6). The surfaces of the open channels are deposited with permselective membranes and possibly one or more intermediate support layers. The porous suppon of these multi-channel structures are produced by extrusion of ceramic pastes described above with a channel diameter of a few millimeters. Their lengths are somewhat limited by the size of the furnaces used to dry, calcine and sinter them and also by such practical considerations as the total compact weights to be supported during heat ueatment and the risk of distortion in the middle section. It should be noted that this type of honeycomb... 

Hence, increase the temperature led to a redistribution of evolved hydrogen from those creating a honeycomb-like structure (holes formed due to the attachment of hydrogen bubbles with cauliflower-like agglomerates of copper grains between them) to those making a copper structure with the dominant presence of cauliflower-like forms and irregular channels between them. 

Tanev et al. have reported the synthesis of mesoporous materials via a route which involves self-assembly between neutral primary amines and neutral inorganic framework precursors.12 The regularity of the pore structure in these materials has been illustrated by lattice images which show a honeycomb like structure. The system of channels of these molecular sieves produces solids with very high internal surface area and pore volume. This fact combined with the possibility of generating active sites within the channels produces a very unique type of acid catalyst. In the case of transition metal substituted M41S, the principal interest lies in their potential as oxidation catalysts, especially Ti and V substituted MCM and HMS type materials, and more recently synthesised large pore materials.13... 

Guest removal and exchange were investigated for benzene-1,3,5,-TEB-silvertriflate [TEB=tm(4-ethynyl-benzonitrile)] [8] (Fig. 3c). The nitrile functionality of the trigonal phenyl-acetylene-derived ligand coordinates to silver cations forming a (3,3)-connected 3D network. A honeycomb-like structure with a channel... 

FIGURE 9.2 Evolution of the geometry of ceramic membrane elements, (a) Conventional cylindrical-shaped channels, (b) Flower-like designed channels, (c) Honeycomb-type structure. 

The number, size, and distribution of holes in 3D foam or the honeycomb-like structures can be easily controlled by the choice of appropriate electrolysis parameters [20, 24, 25]. Also, the size of grains constructing dendrites or cauliflower-like agglomerates formed around holes, as well as the size of channels between small metal grains agglomerates, is controlled by conditions of electrolysis. The cauliflower-like agglomerates and dendrites among holes define the wall width in this structure type. The specific surface area of the 3D foam or the honeycomb-like... 

A desiccant wheel assembly consists of i) a core that contains the desiccant materials, ii) a core/wheel support structure, iii) a drive system to rotate the wheel at a very low speed, and iv) a set of air seals to separate the process air stream from the regeneration air stream. The core has a monolith honeycomb type structure. Both sinusoidal and hexagonal channels are used in commercial equipment. Various types of materials have been used for support matrix that includes ceramic, glass fibers, and corrugated aluminum sheets. The desiccant materials may be washcoated, impregnated, or formed in situ on the support matrix. 

Diesel particulate filters (DPFs) (see Figure 19.1) are used to remove soot particles from the exhaust stream [1-4]. These filters usually consist of wall-flow monoliths, that is, honeycomb-like structures with 50% of the channels plugged at the gas entry side and the remaining channek plugged at the exit The gas stream enters into the filter through the open channels and is forced to pass through the porous walls where the soot particles get stuck. 

Pan and Xue also synthesized pillar[5]arenes with three different kinds of substituent unit. Pillar[5]arenes containing one (6.16) and two (6.17) benzoquinone units assembled into one-dimensional channels by the stacking of pillar[5]arene molecules (Figure 6.10). The channels arranged into honeycomb-like structures. In contrast, two overlapped tubes were observed in pillar[5]arene with three benzoquinone units (6.18). 

The small particles are reported to be very harmful for human health [98]. To remove particulate emissions from diesel engines, diesel particulate filters (DPF) are used. Filter systems can be metallic and ceramic with a large number of parallel channels. In applications to passenger cars, only ceramic filters are used. The channels in the filter are alternatively open and closed. Consequently, the exhaust gas is forced to flow through the porous walls of the honeycomb structure. The solid particles are deposited in the pores. Depending on the porosity of the filter material, these filters can attain filtration efficiencies up to 97%. The soot deposits in the particulate filter induce a steady rise in flow resistance. For this reason, the particulate filter must be regenerated at certain intervals, which can be achieved in the passive or active process [46]. 

The nanoreplication of functional nanostructures has also been achieved through other block copolymer-templated structures. De Boer et al. [35] applied honeycomb-structured films of rod-coil block copolymer as patterned templates to replicate hexagonally packed arrays of aluminum cups on the substrate surfaces (Fig. 10b). Nguyen et al. [237] embedded semiconducting polymers in the channels of oriented hexagonal nanoporous silica and used this nanoscale architecture to control the energy transfer for potential optoelectronic applications. 

Ceramic honeycomb monoliths are porous macro-structured supports consisting of parallel channels. On the walls a thin layer of active material can be applied (Figure 1). Honeycomb catalyst supports were originally developed for use in automotive... 

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