Vacuum system, glass flow

A continuous-flow reactor with a fixed catalyst bed was employed under pressurized conditions. The reactor was made of stainless steel with an inner diameter of 6 mm. All products and unreacted feed materials were withdrawn in the gaseous state from the reactor through a heated pressure let-down valve, A quantitative analysis of the products was carried out by gas chromatography. The time factor, which corresponds to contact time, is expressed by W/F, where W is the weight of catalyst (g) and F is the total flow rate of feed (mol/hr). Chemisorption of H2, CO and methyl iodide (Mel) were measured by a conventional glass vacuum system. 

All reductions were carried out on a glass vacuum system under static H2 (Linde 99.999%) which was dried by passing through Drierite and molecular sieves prior to exposure to the sample. H2 uptakes were monitored using a capacitance manometer (MKS Instruments Inc.) N2 isotherms at 77 K were performed on the same vacuum system using pre-purified grade N2 (Linde) which was dried prior to use. Oxidations were performed under flowing 02 (Linde 99.999%) at 773 K and under static O2. The samples were evacuated at 623 K to a residual pressure of less than 5 X 10 5 torr prior to reduction or N2 isotherm measurements. 

The home-made heat-flow calorimeter used consisted of a high vacuum line for adsorption measurements applying the volumetric method. This equipment comprised of a Pyrex glass, vacuum system including a sample holder, a dead volume, a dose volume, a U-tube manometer, and a thermostat (Figure 6.3). In the sample holder, the adsorbent (thermostated with 0.1% of temperature fluctuation) is in contact with a chromel-alumel thermocouple included in an amplifier circuit (amplification factor 10), and connected with an x-y plotter [3,31,34,49], The calibration of the calorimeter, that is, the determination of the constant, k, was performed using the data reported in the literature for the adsorption of NH3 at 300 K in a Na-X zeolite [51]. 

Figure 2-12 Filtration with a Gooch filter crucible that has a porous glass (fritted) disk through which liquid can pass. Suction is provided by a vacuum line at the lab bench or by an aspirator that uses flowing water from a tap to create a vacuum. The trap prevents backup of filtrate into the vacuum system or backup of water from the aspirator into the suction flask.

Triallate concentration in air was obtained using a series of two polyurethane foam (PUF) plugs held in a glass tube (72). A vacuum system was used to draw triallate-laden air into the foam at a prescribed flow rate, 15 L min . After each sampling interval, the PUF was stored in a freezer until transport to the laboratory for analysis of the triallate concentration. Soil samples were taken using a coring device 2.5 cm in diameter. Twice each day, a total of 31 samples were collected randomly within the field to a depth of 1 cm. 

Unlike other spectroscopic methods requiring samples under vacuum or very low gas pressures, NMR spectroscopy of working catalysts is not limited by the so-called pressure gap. The flow techniques described in Section III.B are suitable for catalytic reaction experiments under atmospheric pressure. If necessary, a higher pressure inside the MAS NMR rotor reactor can be used. The gas pressure inside batch samples may be limited by the strength of the walls of the glass inserts or the type of the cap used to seal the MAS NMR rotor after the preparation of the reaction system. In both cases, at least atmospheric pressure can be reached inside the sample volume. 

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