Gas-phase reservoir

This account summarizes our own results and the reports of other authors regarding the photochemical reactions between transition metal complexes and gases at high pressures. The reactions usually take place in a liquid solvent between dissolved substrates, metal complexes, and dissolved gases which are in equilibrium with a gas phase reservoir. 

Figure 6.11. Schematic diagram of the automated multiple development chamber. Identification 1 = developing chamber 2 = solvent reservoirs 3 = solvent selection valve 4 = solvent mixer 5 = wash bottle for preparation of the gas phase for layer conditioning 6 = gas phase reservoir 7 = vacuum pump and 8 = solvent waste reservoir.

Figure 5 The AMD development unit (CAMAO) featuring a developing chamber, six solvent reservoir bottles, seven-port motor-driven valve, two-step gradient mixer, wash bottle, gas phase reservoir vacuum pump, and water collection bottle.

Peroxynitric acid (HO2NO2, PNA) plays an important role in atmospheric chemistry as a gas-phase reservoir for NO (NO and NO2) and HO in the stratosphere as well as the troposphere. The lifetime of PNA at the middle latitudes in the upper troposphere and lower stratosphere is in the range of 10-12 h. However, at the higher tonperatures found in the lower troposphere and even in the middle of the upper stratosphere, HOjNOj degradation can be dominated by thermal decomposition (reaction -1)... 

Because a chemical potential is not easily measured directly, it is desirable to relate it to quantities more directly accessible in an adsorption experiment, such as temperature and pressure. This can be accomplished by assuming that the adsorption system is in equilibrium with a gas-phase reservoir ... 

The choice of gas-phase reservoir is not unique and may be defined in a number of ways, and this choice affects the relationship between chemical potential and gas pressures. The conceptually simplest case to consider is an adsorbate dosed by its native gas-phase species, A(g), but depending on the particular experimental situation of interest or on the reliability of the available DFT data, it is also appropriate to define a reference to something other than A itself. " In the 0-Pt(321) system, surface O might be dosed by dissociative adsorption of O2 ... 

We discuss these two eases in more detail below, but numerous other scenarios could be imagined, involving dosing by CO2, H2O, atomic O, O3, or even solid oxides. Reference states for adsorbates are not restricted to reservoirs of gas-phase species, but this interpretation is eonceptually simple to understand when discussing adsorption at a gas-solid interface, and we refer to the adsorbate reservoir as a gas-phase reservoir simply for convenience. 

With the oxygen chemical potential rewritten in terms of the gas-phase reservoir species, we then substitute back into eqn (2.32) for an expression of the surfaee energy as a function of T, Pno2 P o-... 

For this choice of reference, we write the chemical potential change as A/r) to distinguish it from the previous case relative to a 0 K reference. In this way, A A = 0 corresponds to the surface in equilibrium with the gas-phase reservoir at the same temperature and the reference pressure. Negative values of A ) would indicate equilibrium with a pressure less than P and positive values with a pressure greater than P. We have already defined, Pa) in eqn (2.34),... 

The initial condition for the dry gas is outside the two-phase envelope, and is to the right of the critical point, confirming that the fluid initially exists as a single phase gas. As the reservoir is produced, the pressure drops under isothermal conditions, as indicated by the vertical line. Since the initial temperature is higher than the maximum temperature of the two-phase envelope (the cricondotherm - typically less than 0°C for a dry gas) the reservoir conditions of temperature and pressure never fall inside the two phase region, indicating that the composition and phase of the fluid in the reservoir remains constant. 

Reservoir engineers describe the relationship between the volume of fluids produced, the compressibility of the fluids and the reservoir pressure using material balance techniques. This approach treats the reservoir system like a tank, filled with oil, water, gas, and reservoir rock in the appropriate volumes, but without regard to the distribution of the fluids (i.e. the detailed movement of fluids inside the system). Material balance uses the PVT properties of the fluids described in Section 5.2.6, and accounts for the variations of fluid properties with pressure. The technique is firstly useful in predicting how reservoir pressure will respond to production. Secondly, material balance can be used to reduce uncertainty in volumetries by measuring reservoir pressure and cumulative production during the producing phase of the field life. An example of the simplest material balance equation for an oil reservoir above the bubble point will be shown In the next section. 

Condensable Hquids also are recovered from high pressure gas reservoirs by retrograde condensation. In this process, the high pressure fluid from the reservoir produces a Hquid phase on isothermal expansion. As the pressure decreases isotherm ally the quantity of the Hquid phase increases to a maximum and then decreases to disappearance. In the production of natural gas Hquids from these high pressure wells, the well fluids are expanded to produce the optimum amount of Hquid. The Hquid phase then is separated from the gas for further processing. The gas phase is used as a raw material for one of the other recovery processes, as fuel, or is recompressed and returned to the formation. 

Deposition of adamantane from petroleum streams is associated with phase transitions resulting from changes in temperature, pressure, and/or composition of reservoir fluid. Generally, these phase transitions result in a solid phase from a gas or a liquid petroleum fluid. Deposition problems are particularly cumbersome when the fluid stream is dry (i.e., low LPG content in the stream). Phase segregation of solids takes place when the fluid is cooled and/or depressurized. In a wet reservoir fluid (i.e., high LPG content in the stream) the diamondoids partition into the LPG-rich phase and the gas phase. Deposition of diamondoids from a wet reservoir fluid is not as problematic as in the case of dry streams [74, 75]. 

Figure 16. Schematic representation of a degassing magma reservoir in a physical steady-state (mass M of magma constant). ( ) and [Ik] denote fluxes and radionuclide Ik concentrations, respectively. Indices 0, L, G, E, I, R, refer to deep undegassed magma (in radioactive equilibrium), degassed lava, gas phase, and erupted, intended, or recycled degassed magma, respectively (after Gauthier and Condomines 1999).

Figure 19. ( °Po/ °Pb)G and ( °Bi/ °Pb)o activity ratios in the gas phase as a function of the magma residence time t in the degassing reservoir. Curves are drawn from the equations ...

Diffusion Systems The liquid whose vapor is to be the contaminant of the gas phase is contained in a reservoir maintained at a constant temperature. The liquid is allowed to evaporate and the vapor diffuses slowly through the capillary tube into a flowing gas stream. If the rate of diffusion of the vapor and the flow rate of the diluent gas are known, the vapor concentration in the resultant gas mixture can be calculated. 

Ionisation processes in IMS occur in the gas phase through chemical reactions between sample molecules and a reservoir of reactive ions, i.e. the reactant ions. Formation of product ions in IMS bears resemblance to the chemistry in both APCI-MS and ECD technologies. Much yet needs to be learned about the kinetics of proton transfers and the structures of protonated gas-phase ions. Parallels have been drawn between IMS and CI-MS [277]. However, there are essential differences in ion identities between IMS, APCI-MS and CI-MS (see ref. [278]). The limited availability of IMS-MS (or IMMS) instruments during the last 35 years has impeded development of a comprehensive model for APCI. At the present time, the underlying basis of APCI and other ion-molecule events that occur in IMS remains vague. Rival techniques are MS and GC-MS. There are vast differences in the principles of ion separation in MS versus IMS. 

Air from a cylinder at pressures up to about 10 bar (150 psi) is applied to a gas piston that has a relatively large surface area. The gas piston is attached to a hydraulic piston that has a smaller surface area. The pressure applied to the liquid = gas pressure x area of gas piston/area of hydraulic piston. With 10 bar inlet pressure and a 50 1 area ratio, the hydraulic pressure obtained is 500 bar (7500 psi). On the drive stroke, the outlet valve on the pump head is open to the column and the inlet valve closed to the mobile phase reservoir. At the end of the drive stroke, the air in the chamber is vented and air enters on the other side of the gas piston to start the return stroke. On the return stroke the outlet valve closes, the inlet valve opens and the pump head refills with mobile phase. The pump can be started and stopped by operation of a valve fitted between the cylinder regulator and the pump. 

With a final example, we consider how the presence of a gas phase can serve as a chemical buffer. A fluid, for example, might maintain equilibrium with the atmosphere, soil gas in the root zone, or natural gas reservoirs in deep strata. Gases such as 02 and H2 can fix oxidation state, H2S can set the activity of dissolved sulfide, and C02 (as we demonstrate in this section) can buffer pH. 

Hofstadler, S.A. Sannes-Lowery, K.A. Griffey, R.H. Enhanced Gas-Phase Hydrogen-Deuterium Exchange of Oligonucleotide and Protein Ions Stored in an External Multipole Ion Reservoir. J. Mass Spectrom. 2000, 55, 62-70. 

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