Catalytic devices specificity

Physical devices (catalytic devices) for the nonchemical treatment of water and, more specifically, devices for scale prevention that employ magnetic fields have been part of the water treatment marketplace around the world since its earliest days. These devices include electronic, catalytic, electrostatic, and magnetic water treatments. There are also various other types of more recent alternative technologies (to chemical treatments) now available in the marketplace. These are being promoted for use in treating all types of MU water, FW, and BW. 

The majority of catalytic devices used in the modem chemical industry (i.e., both usual heterogeneous catalysts and materials based on applications of the catalytic properties) are based on mixed oxides (1- 3). The synthesis of specific tailor-made mixed oxides able to perform complex functions is one of the most current topics in solid state chemistry (4). 

Ley and Baxendale have shown that it is possible to complete a total synthesis by using a number of flow devices in series, which contained immobihzed reagents (14). Use of a number of CCSs in series would allow cascade catalysis in which the catalytic systems have been separated (Figure 4.2). This is quite attractive in view of the fact that often each catalyst needs highly specific operating conditions, such as temperature and pH. 

Enzymes are remarkable molecular devices that determine the pattern of chemical transformations in biological systems. The most striking characteristics of enzymes are their catalytic power and specificity. As a class of macromolecules, they are highly effective in catalyzing diverse chemical reactions because of their ability to specifically bind to a substrate and their ability to accelerate reactions by several orders of magnitude. Applying enzymes or organisms in... 

Compound-specific isotope analysis (CSIA) by GC-IRMS became possible in 1978 due to work of Mathews and Hayes [634], based on earlier low-precision work of Sano et al. [635]. The key innovation was the development of a catalytic combustion furnace based on Pt with CuO as oxygen source, placed between the GC exit and the mass spectrometer. The high pressure of helium (99.999% purity or better) ensures that all gas flows are viscous. After being dried in special traps avoiding formation of HC02 (i. e., interferes with 13C02) by ion-molecule reactions in the ion source, the C02 is transmitted to a device that regulates pressure and flow and then into the ion source [604]. 

This chapter deals with the selective preparation, TEM/EXAFS/XPS characterization and catalysis of mono- and bimetallic nanowires and nanoparticles highly ordered in silica FSM-16, organosilica HMM-1 and mesoporous silica thin films. The mechanism of nanowire formation is discussed with the specific surface-mediated reactions of metal precursors in the restraint of nanoscale void space of mesoporous silica templates. The unique catalytic performances of nanowires and particles occluded in mesoporous cavities are also reviewed in terms of their shape and size dependency in catalysis as well as their unique electronic and magnetic properties for the device application. 

The chemisorption of ions plays another role in determining the properties of PEC devices. The adsorbed ions may create the chemical intermediates or specific reaction sites necessary for charge transfer and chemical product formation. The rapid kinetics in photoelectrolysis and wet photovoltaic cells are in no small part due to the fact that in most of these systems the redox species are strongly adsorbed. Knotek(10,ll) and others (12,13) have shown that the nature of the TiC>2 surface and the species adsorbed on it greatly affect its catalytic properties. 

Engstrom and Carlsson already introduced in 1983 an SLPT [119] for the characterisation of MIS structures, which was extended to chemical gas sensors by Lundstrom et al. [26]. Both SLPT and LAPS base upon the same technique and principle. However, due to the different fields of applications in history, one refers to LAPS for chemical sensors in electrolyte solutions and for biosensors, and the SLPT for gas sensors. A description of the development of a hydrogen sensor based on catalytic field-effect devices including the SLP technique can be found, e.g., in Refs. [120,121]. The SPLT consists of a metal surface as sensitive material which is heated by, for instance, underlying resistive heaters to a specific working-point temperature, and a prober tip replaces the reference electrode (see Fig. 5.10). 

This section will provide information about micro structured reformer reactors, gas purification devices and catalytic burners, the last also in combination with an evaporator, for fuel processors. However, the specific problems related to the peripheral equipment will not be discussed in depth. 

Mother nature has resolved the various limitations involved in multi-electron processes. Unique assemblies composed of cofactors and enzymes provide the microscopic catalytic environments capable of activating the substrates, acting as multi-electron relay systems and inducing selectivity and specificity. Artificially tailored heterogeneous and homogeneous catalysts as well as biocatalysts (enzymes and cofactors) are, thus, essential ingredients of artificial photosynthetic devices. 

---