Reagent gases hydrocarbon

GC/MS TIC traces of butyl methacrylate dissolved in C11-C12 saturated hydrocarbon, (a) EL The peak corresponding to butyl methacrylate is marked by a dot. The peaks following are Cll saturated hydrocarbons. (b) Same trace obtained by Cl usig methane as reagent gas. Butyl methacrylate (dot) is still well detected, but the trace of the hydrocarbons is aten-uated. (c) Cl using isobutane as reagent gas. Butyl methacrylate is well detected, while the hydrocarbons are almost not detected. 

The composition of the reagent gas plasma is controlled by the mobile phase composition. It contains reactant ions of the type HsO, CH30H2, CHsCNH, etc., in most cases solvated by solvent molecules, for example, CH30H2 (H20)n(CH30H)ni with n + m < 4. The presence of ammonia vapor, for example, as a result of the evaporation of ammonium acetate added to the mobile phase, causes rapid removal of protonated solvent ions with formation of ammonium ions that become the dominant reagent gas ions. The addition of alkylamines or acids to the mobile phase results in the formation of protonated amines or anions as the dominant species in the reagent gas plasma. Since highly reactive ions, such as CHs" ", can not be formed by APCI in the presence of solvents, it is not possible to ionize saturated hydrocarbons or other compounds of low gas-phase basicity. 

Hydride transfer from M occurs mainly when the analyte molecule is a saturated hydrocarbon. In addition, the ionized reagent gas can react with M to form, for example, an (M + C2H5) ion with m/z= (M + 29). The presence of such an adduct ion of mass 29 Da above a candidate molecular ion in a methane Cl mass spectrum is a good confirmation of the identity of the molecular ion. 

Reagent Ion Capture The capture of negative reagent gas ions was described in the early 1970s by Manfred von Ardenne and coworkers for the analysis of long-chain aliphatic hydrocarbons with hydroxyl ions (Ardenne etal., 1971). 

The use of water is universal. In the determination of polyaromatic hydrocarbons, considerable increases in response compared with El detectors are found. Analytical procedures have even been published for nitroaromatics. Water can also be used successfully as a reagent gas for screening small molecules, for example, volatile halogenated hydrocarbons (industrial solvents), as it does not interfere with the low scan range for these substances. 

Figure 4 ionization potentiais of hydrocarbons as a function of moiecuiar mass. Reprinted with permission from Sieck LW (1983) Determination of moiecuiar weight distributions of aromatic components in petroieum products with chiorobenzene as reagent gas. Analytical Chemistry 55 38-41. Copyright (1983) American Chemicai Society. 

Ionization is achieved in the following way. A reagent gas, frequently methane or other simple hydrocarbon gas, is ionized by electron impact at a high source pressure (about 0.133 kPa). The resulting reactive ion plasma in turn ionizes sample molecules by ion-molecule collision. This can be either by proton transfer from, or hydride extraction by, the reagent gas ions and so give rise to quasimolecular ions from the sample, i.e. (M H)t. 

Acetylene has a low solubiHty in Hquid oxygen. Excessive concentrations can lead to separation of soHd acetylene and produce accumulations that, once initiated, can decompose violently, detonating other oxidizable materials. Acetylene is monitored routinely when individual hydrocarbons are determined by gas chromatography, but one of the wet classical methods may be more convenient. These use the unique reaction of acetylene with Ilosvay s reagent (monovalent copper solution). The resulting brick-red copper acetyHde may be estimated colorimetricaHy or volumetricaHy with good sensitivity (30). 

CNTs can also be produced by diffusion flame synthesis, electrolysis, use of solar energy, heat treatment of a polymer, and low temperature solid pyrolysis. In flame synthesis, combustion of a portion of the hydrocarbon gas provides the elevated temperature required, with the remaining fuel conveniently serving as the required hydrocarbon reagent. Hence, the flame constitutes an efficient source of both energy and hydrocarbon raw material. Combustion synthesis has been shown to be scalable for a high volume commercial production. 

Reactants and reagents can be conveniently loaded into the dry zeolite by adsorption. This can be accomplished by intimately mixing the solid or liquid reactant and the powdered zeolite, by absorption from the gas phase, or by diffusion in a solvent slurry containing the zeolite and dissolved reactant. The choice of solvent for the slurry method is critical. It must be volatile enough to be removable at a pressure and temperature that does not result in evacuation of the reactant or its decomposition. In addition, the reactant must have a greater affinity for the interior of the zeolite than for the slurry solvent itself. The lack of affinity for the interior of the zeolite is an acute problem for non-polar hydrocarbons that lack binding sites for the intrazeolitic cations. The use of fluorocarbons such as perfluorohexane as slurry solvents takes advantage of the fluorophobicity of many hydrocarbons and has alleviated this problem to some extent.29... 

As stated, one of the fundamental problems encountered in the direct oxidation of hydrocarbon fuels in SOFCs is carbon deposition on the anode, which quickly deactivates the anode and degrades cell performance. The possible buildup of carbon can lead to failure of the fuel-cell operation. Applying excess steam or oxidant reagents to regenerate anode materials would incur significant cost to SOFC operation. The development of carbon tolerant anode materials was summarized very well in several previous reviews and are not repeated here [7-9], In this section, the focus will be on theoretical studies directed toward understanding the carbon deposition processes in the gas-surface interfacial reactions, which is critical to the... 

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