Saturation gas flow

CP grade ethylene (Matheson) was used without purification. A flow of ca. 100 raL/min of ethylene for 2-3 hr is adequate for saturation. Gas flow is continued throughout the irradiation in order to maintain a high concentration of ethylene and for stirring. 

The results obtained in c ase of S% CaCC>3 suspension and very Icrw CO2 concentration show, that at superficial velocity Wo=0.S m/s after 96 h, respectively 340 h the increasing of the pNressure drop is less than 8%, i.e. in case of a saturated gas flow the precipitaticm and crystallization can be practically neglected. The results obtain when these prcx esses cannot be neglected are presented in Figs. 2 to 4. 

Processing variables that affect the properties of the thermal CVD material include the precursor vapors being used, substrate temperature, precursor vapor temperature gradient above substrate, gas flow pattern and velocity, gas composition and pressure, vapor saturation above substrate, diffusion rate through the boundary layer, substrate material, and impurities in the gases. Eor PECVD, plasma uniformity, plasma properties such as ion and electron temperature and densities, and concurrent energetic particle bombardment during deposition are also important. 

Figure 3.5 The apparent vapour pressure of gold in gas transportation measurements as a function of the gas flow rate. Low flow rates, which were used earlier to assure equilibrium, are now known to be too high as a result of thermal diffusion in the gas mixture which is saturated with gold vapour...

In the adsorption cycle, the wet inlet gas flows downward through the tower. The adsorbable components are adsorbed at rates dependent on their chemical nature, the size of their molecules, and the size of the pores. The water molecules are adsorbed first in the top layers of the desiccant bed. Dry hydrocarbon gases are adsorbed throughout the bed, As the upper layers of desiccant become saturated with water, the water in the wet gas stream begins displacing the previously adsorbed hydrocarbons in the lower desiccant layers. Liquid hydrocarbons will also be absorbed and will fill pore spaces that would otherwise be available for water molecules. 

The checkers found considerable variation in the rate of the reaction in different runs, the time required for its completion ranging from 3 to 10 hours. It is therefore advisable to monitor the progress of the reaction. For this purpose small aliquots (ca. 0.05 ml.) were withdrawn from the flask with a syringe and hydrolyzed by injection into a vial containing ether and saturated ammonium chloride. The relative amoimts of enol silane and cyclopropoxy sdane were determined by gas chromatography on an 0.6 cm. X 3.7 m. column of 3% OV-17 coated on 100-120 mesh Chromosorb W. With a column temperature of 120° and a carrier gas flow rate of 20 ml. per minute, the retention times for the enol silane and the cyclopropoxy silane are ca. 1.9 and 2.3 minutes, respectively. 

Catalytic activity for the selective oxidation of H2S was tested by a continuous flow reaction in a fixed-bed quartz tube reactor with 0.5 inch inside diameter. Gaseous H2S, O2, H2, CO, CO2 and N2 were used without further purification. Water vapor (H2O) was introduced by passing N2 through a saturator. Reaction test was conducted at a pressure of 101 kPa and in the temperature range of 150 to 300 °C on a 0.6 gram catalyst sample. Gas flow rates were controlled by a mass flow controller (Brooks, 5850 TR) and the gas compositions were analyzed by an on-line gas chromotograph equipped with a chromosil 310 coliunn and a thermal conductivity detector. 

In a procedure developed by Carturan et al. [79,93] the alcohol is removed in a gas flow. This is also used to deliver the silica precursor. An alkoxide is initially evaporated to saturate a heated inert gas which serves as a carrier. When the gas... 

The HTE characteristics that apply for gas-phase reactions (i.e., measurement under nondiffusion-limited conditions, equal distribution of gas flows and temperature, avoidance of crosscontamination, etc.) also apply for catalytic reactions in the liquid-phase. In addition, in liquid phase reactions mass-transport phenomena of the reactants are a vital point, especially if one of the reactants is a gas. It is worth spending some time to reflect on the topic of mass transfer related to liquid-gas-phase reactions. As we discussed before, for gas-phase catalysis, a crucial point is the measurement of catalysts under conditions where mass transport is not limiting the reaction and yields true microkinetic data. As an additional factor for mass transport in liquid-gas-phase reactions, the rate of reaction gas saturation of the liquid can also determine the kinetics of the reaction [81], In order to avoid mass-transport limitations with regard to gas/liquid mass transport, the transfer rate of the gas into the liquid (saturation of the liquid with gas) must be higher than the consumption of the reactant gas by the reaction. Otherwise, it is not possible to obtain true kinetic data of the catalytic reaction, which allow a comparison of the different catalyst candidates on a microkinetic basis, as only the gas uptake of the liquid will govern the result of the experiment (see Figure 11.32a). In three-phase reactions (gas-liquid-solid), the transport of the reactants to the surface of the solid (and the transport from the resulting products from this surface) will also... 

In this procedure methylstannanes were generated directly in buffered sample, purged and cryogenically trapped on the head of a chromatographic column. Gas flow was diverted from the hydride generator while the purge tube was filled with up to lOmL of fluid, usually consisting of 5mL of sample and 5mL of buffer (saturated... 

Nguyen et al. [205] used a technique in which a constant mass flow rate of water-saturated air was forced through a water-saturated sample. It was explained that the shear force of the gas flow dragged water out of the sample. In addition, the saturated air was needed in order to prevent water loss from the sample by evaporation. Once a steady state was achieved, the pressure difference between the inlet and outlet of the apparatus was recorded. After the tests were completed, the sample was weighed to obtain its water content. Thus, the relative permeability was calculated from the pressure drop, the water content in the sample, and the mass flow rate [205]. 

This method in principle can also be used to estimate the average pore size of the membrane when there are no defects in the membrane. First, gas flows through the membrane in the dry state. Typically, the gas flow rate is a linear function of the applied pressure difference. Then the membrane is saturated with the test liquid and the gas is forced to flow through the wet... 

The reaction takes place in a trickle bed of 4.1 cm diameter and 1 m height with liquid flow rate of 2.17 kg/s m2, gas flow rate of 0.017 kg/s m2, and inlet ethanol concentration of 0.006 kmol/rn3. Horowitz et al. (1999) noted that pure oxygen was used as the gas feed, and under the experimental conditions the conversion of 02 was less than 5%. Thus, the gas-phase concentration of 02 can be considered constant. Furthermore, the liquid phase entered the reactor saturated with 02. Under these conditions, the conversion of the ethanol was about 14%. 

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