Hydrogen helium stream

In at5q)ical operation, about 100 mg of the powdered catalyst is placed in a ceramic boat, which is positioned in a quartz tube located in a horizontal tube furnace. The sample is initially reduced in a 10% hydrogen helium stream at 600 °C and then quickly brought to the desired reaction temperature. Following this step, a predetermined mixture of hydrocarbon, hydrogen, and inert gas is introduced into the system and the reaction allowed proceeding for periods of about 2 h [6]. 

Cmde helium (containing 50—70% helium, associated hydrogen and neon, 1—3% methane, and the balance nitrogen) can easily be obtained by minor enhancements to the nitrogen rejection unit, particularly with natural gases containing 0.5% or more helium. For example, by operating the double-column condenser in a partial condensation mode, a stream of uncondensed vapor at about 50% helium concentration can be obtained. This cmde helium stream can be fed directly to helium purification and Hquefaction units. 

Figure 12 shows the spectrum for the deformation region in an ethylene-helium stream and an ethylene-hydrogen stream. In the deformation region the two bands at 1451 and 1438 cm-1 due to ethylene alone appear to weaken and shift slightly and a new band (or perhaps two) appears at about 1415 cm-1. Figure 12 also shows that under reaction conditions the ZnH band is shifted from 1709 to 1655 cm 1 the corresponding shift in the OH band is from 3490 to 3510 cm-1. 

Total Amount of Adsorbed Oxygen. The amount of adsorbed oxygen can easily be estimated from the graphical integration of the 2 °2 response curve. After the catalyst surface had completely been reduced by a pure hydrogen stream for about 5 hrs, the stream was switched over to a pure helium stream and then the (inc.,0)-C>2> the 0 (dec. , 0)-C and again the ( (inc.jO) -C>2 responses were followed successively. This procedure was repeated after changing the concentration of 0. Fig.l clearly shows a delay for the C>2 (inc. , 0) -C>2 response (Runl) at first time and shows an instantaneous response for both the successive 0 (dec.,0)-C ... 

Procedure. After the catalyst has reached a steady state synthesis activity the synthesis gas stream is switched to a hydrogen/helium gas mixture (ratio 0.25) at a velocity of 0.75 cm-fys and 0.25 MPa. The temperature in the reactor is held at 550 K. When the production of hydrocarbons is very small, the H2/He stream is replaced by synthesis gas for 20 seconds, whereafter again l /He is fed to the catalyst. Pressure, temperature and feed are carefully held constant during this treatment. A second experiment is carried out that is almost identical to the one described above. The only difference is that instead of a mixture of hydrogen and helium pure helium is used in the periods between the introduction of synthesis gas. 

At 400° C., hydrogen was able to displace H2S more quickly than helium, because it was possible to produce small H2S peaks by injecting hydrogen into the reactor while H2S was still slowly desorbing in a helium stream. This could conceivably have involved some desulfiding, but clearly the rest of the phenomena observed were due to desorption. 

The reaction of silicon with a gaseous mixture of ethylene and hydrogen chloride was carried out at temperatures ranging from 240 to 260 °C, after preheating a mixture of elemental silicon and copper(I) chloride in a helium stream at 450°C.82 Ethyldichlorosilane was formed along with trichlorosilane, dichlorosilane, and tetrachlorosilane (Eq. 20). 

The water and hydrogen line shapes generated by the TPRn of a 0.6% water in helium stream on a potash promoted catalyst are shown in Figure 4. These data indicate that no water decomposition occurred on this catalyst surface at temperatures of less than 400 C. However, above this temperature hydrogen was produced, A similar reaction profile was observed on an alkali free nickel catalyst ... 

A transparent Universe. After 300,000 yr temperatures dropped to 4,500 K and gave rise to the formation of atomic matter, and atoms of hydrogen, helium, and deuterium were formed. Because electrons were removed from the plasma through the formation of atoms, radiation streamed out and the Universe became transparent. Initially the Universe contained abundant ultraviolet-and X-rays, now cooled down to microwave wavelengths. This is what is recorded as the Cosmic Background radiation. 

The apparatus used for these experiments has been described previously (10). In a typical TPD experiment, 25 mg of sample were placed in a quartz microreactor which was mounted inside a furnace. Following evacuation for 1 h at room temperature, helium was flowed over the sample at a rate of 100 cc/min (STP) and the temperature was raised at 0.5 K/s. During heating, the desorption products were swept from the reactor by the helium stream and monitored downstream with a UTI Model 100 C quadrupole mass spectrometer. Upon completion of each TPD experiment, the mass spectrometer was calibrated for oxygen as described below, and then a TPR experiment was performed using a hydrogen flow rate of 200 cc/min (STP). After each TPR experiment, the mass spectrometer calibration was repeated. 

Carbon was deposited on the reduced catalyst samples by TPRn of a 7% propane In helium stream (pressure 1 atm helium flow rate 25ml min 1). The rate of the catalytic decomposition of propane on the catalysts was monitored using the hydrogen produced by the decomposition reaction (Figure 1),... 

Example 2.5.2 Prior to reacting an iron oxide pellet with hydrogen in a tubular furnace, we wish to preheat the specimen to the reaction temperature of 700°C by contacting it with a helium stream at 700°C. If the convective heat transfer coefficient is 10 " cal/cm °C sec, estimate the time required for the specimen to reach 650°C. 

Therefore, the reduction extent can be easily controlled by determining the amount of produced HCl this is done by a down-stream trap containing a basic solution after the reduction, the rest of basic solution is titrated key parameters are flow rate and composition of hydrogen/helium mixture to avoid redox decomposition of the precursor and formation of chlorine as it could be the case for platinum or iridium precursors H2PtCl6orH2lrCl6. 

Because of their very low boiling points, helium, neon, and hydrogen are noncondensable under the conditions at the top of the nitrogen column, and they concentrate in the nitrogen gas there. Because they cut down on the rate of condensation of nitrogen and thereby reduce the thermal efficiency of the process, they must be withdrawn. The noncondensable stream withdrawn may have a neon, helium, or hydrogen content that varies from 1 to 12%... 

I eon—Helium Separation and Purification. As indicated eadier, neon, heHum, and hydrogen do not Hquefy in the high pressure (nitrogen) column because these condense at much lower temperatures than nitrogen. As withdrawn, the noncondensable stream has a neon—helium content that varies 1—12% in nitrogen, depending on the rate of withdrawal and elements of condenser design and plant operation. 

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