Activity, chemical solid

Analysis of thermal decomposition of molecules on hot surfaces of solids is of considerable interest not only for investigation of mechanisms of heterogeneous decomposition of molecules into fragments which interact actively with solid surfaces. It is of importance also for clarifying the role of the chemical nature of a solid in this process. Furthermore, pyrolysis of molecules on hot filaments made of noble metals, tungsten, tantalum, etc., is a convenient experimental method for producing active particles. Note that it allows continuous adjustment of the intensity of the molecular flux by varying the temperature of the filament [8]. 

The purpose of chemical processes is not to make chemicals the purpose is to make money. However, the profit must be made as part of a sustainable industrial activity. Chemical processes should be designed as part of a sustainable industrial activity that retains the capacity of ecosystems to support both industrial activity and life into the future. Sustainable industrial activity must meet the needs of the present without compromising the needs of future generations. For chemical process design, this means that processes should use raw materials as efficiently as is economic and practicable, both to prevent the production of waste that can be environmentally harmful and to preserve the reserves of raw materials as much as possible. Processes should use as little energy as economic and practicable, both to prevent the buildup of carbon dioxide in the atmosphere from burning fossil fuels and to preserve reserves of fossil fuels. Water must also be consumed in sustainable quantities that do not cause deterioration in the quality of the water source and the long-term quantity of the reserves. Aqueous and atmospheric emissions must not be environmentally harmful, and solid waste to landfill must be avoided. 

The unsaturated open-chain hydrocarbons include the alkene or olefin series, the diene series, and the alkyne series. The alkene series is made up of chain hydrocarbons in which a double bond exists between two carbon atoms. The general formula for the series is CnH2n, where n is the number of carbon atoms. As in the paraffin series, the lower members are gases, intermediate compounds are liquids, and the higher members of the series are solids. The alkene series compounds are more active chemically than the saturated compounds. They react easily with substances such as halogens by adding atoms at the double bonds. 

The weak acidity of the pure OMS materials is disadvantageous for petrochemical processes but for the synthesis of fine chemicals, solids with moderate acidity can be very active catalysts. Table 4.2 gives... 

The discussion so far has described how libraries of potentially active chemical compounds can be produced using solid-phase synthesis. The next question—and a crucial question it is—is which of those compounds meet the basic criteria for which the experiment was intended One might ask, for example, which compounds of all those in the library are actually potent in the treatment of some disease. The process by which the structure of any active compound present in a mixture of compounds is identified is called deconvolution. Deconvolution is often one of the most time-consuming steps in any combinatorial procedure. 

Local chemical composition from areas less than 1 nm in diameter can be measured by energy dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS). Such spectroscopic information may be presented in 2D maps showing the spatial element distribution in the specimen (13). Furthermore, information about the local density of unoccupied electron states of a specific element can be extracted from EELS data and used to estimate the oxidation state and the local coordination geometry of the excited atoms (14). In some favorable cases, electronic structure information with a resolution of about 1 eV from individual atomic columns has been attained (15,16). Recent developments of monochromators and spectrometers have brought the resolution down to 0.1 eV (17,18), and this capability may offer new opportunities to determine relationships between electronic structure information, the atomic arrangements and the catalytic activities of solids. 

Selenium oxybromide is a very active chemical agent. It reacts with sulphur in the cold with the evolution of sulphur dioxide, and with selenium to form the monobromide. Phosphorus reacts violently with the solid silicon and carbon are unattacked. 

Several formal and informal intercomparisons of nitric acid measurement techniques have been carried out (43-46) these intercomparisons involve a multitude of techniques. The in situ measurement of this species has proven difficult because it very rapidly absorbs on any inlet surfaces and because it is involved in reversible solid-vapor equilibria with aerosol nitrate species. These equilibria can be disturbed by the sampling process these disturbances lead to negative or positive errors in the determination of the ambient vapor-phase concentration. The intercomparisons found differences of the order of a factor of 2 generally, and up to at least a factor of 5 at levels below 0.2 ppbv. These studies clearly indicate that the intercompared techniques do not allow the unequivocal determination of nitric acid in the atmosphere. A laser-photolysis, fragment-fluorescence method (47) and an active chemical ionization, mass spectrometric technique (48) were recently reported for this species. These approaches may provide more definite specificity for HN03. Challenges clearly remain in the measurement of this species. 

Ion selective membranes are the active, chemically selective component of many potentiometric ion sensors (7). They have been most successfully used with solution contacts on both sides of the membrane, and have been found to perform less satisfactorily when a solid state contact is made to one face. One approach that has been used to improve the lifetime of solid state devices coated with membranes has been to improve the adhesion of the film on the solid substrate (2-5). However, our results with this approach for plasticized polyvinylchloride (PVC) based membranes suggested it is important to understand the basic phenomena occurring inside these membranes in terms of solvent uptake, ion transport and membrane stress (4,6). We have previously reported on the design of an optical instrument that allows the concentration profiles inside PVC based ion sensitive membranes to be determined (7). In that study it was shown that water uptake occurs in two steps. A more detailed study of water transport has been undertaken since water is believed to play an important role in such membranes, but its exact function is poorly understood, and the quantitative data available on water in PVC membranes is not in good agreement (8-10). One key problem is to develop an understanding of the role of water uptake in polymer swelling and internal stress, since these factors appear to be related to the rapid failure of membranes on solid substrates. 

Activation of solid catalysts under well-specified conditions is a key step for obtaining the desired catalytic performance. It is particularly the case with zeolites, which are hygroscopic solids and for which the efficiency can be significantly reduced by the presence of water (e.g. change in the characteristics of the protonic acid sites, loss of reactant by hydrolysis). Polar organic molecules (even present in low amounts in the atmosphere of the chemical laboratories) can also be rapidly and strongly adsorbed over zeolites causing a decrease of their catalytic efficiency. Pretreatment of the zeolite in the reactor is preferable. This in situ pretreatment is easier to carry out in fixed bed than in batch reactors. 

Schafer, L., Hofer, M. and Kroger, R. (2006), The versatility of hot-filament activated chemical vapor deposition. Thin Solid Films, 515(3) 1017-1024. 

In this paper we consider SHP as a combination of a loop heat pipe (LHP) and ammonia/ (active carbon fiber -I- chemicals) solid sorption cooler. Such system extends the limits of two-phase thermal control and ensures successful mode of electronic components cooling even in very harsh environmental conditions (ambient temperature 40 °C, or more) and ensures a deep cooling of space sensors down to the triple point of the hydrogen. 

The fact that mica (and fused silica) can serve as solid state track detector (SSTD) of fission fragments was reported shortly before the final stage of development of the method for element 104 [12-14], In the dielectric solids, fission fragments produce tiny tracks visible by electron microscopy. Mica and silica are very resistant to active chemical reagents and elevated temperatures. The tracks proved to stay in hostile conditions of real experiments for a reasonably long time. Thanks to this, after the end of bombardment (EOB), the mica sheets could be etched with hydrofluoric acid to enlarge the tracks to micrometer size they were distinct in appearance and were searched out by scanning the surface of the detectors with an... 

The thermodynamic factor T corrects for differences in activities (chemical potentials) of different gases which can exist with similar concentration gradients. It is similar to the factor that has been described in solid state diffusion by Darken and is sometimes named after him. 

The acceleration of a chemical reaction by solid catalysts proceeds at the surface of the catalyst. The catalytic activity of solids is therefore generally proportional to the surface area of the catalytically active component of the catalyst per unit weight or per unit volume. The surface area per unit volume depends on the size of the solid particles and the bulk density. Assuming a bulk density of... 

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