Figure 1

While low pressure reactor systems are useful for reactions run at pressures up to about 100 psig (depending on the size of the reactor) they are not adaptable for reactions run at atmospheric pressure. We have, however, designed apparatus in which gas uptake can be automatically measured while keeping the pressure in the reactor constant at atmospheric. This is diagramed in Figure 1 with a picture shown in Figure 2. The basic component in this system is a sensitive differential pressure transducer (A) with one side measuring atmospheric pressure and the other the internal reactor pressure. The computer monitors the transducer output and when a slight pressure differential (about a half inch of water) is detected because of the gas uptake in the reactor, the pulse valve (B) is opened to introduce a known volume of gas into the reactor. The size of this pulse is dependant on the gas pressure at the pulse valve and the time it remains open. These factors are adjusted to provide calibrated pulses of near one half cc of reactor gas. The selection valve (S) provides a simple means of using different reaction gases. This apparatus can also be used to study reactions in which a gas is produced.

Figure 3

Three of these automated atmospheric pressure reactor systems are pictured in Figure 3. A reproduction of the computer screen showing the progress of all three reactions is shown in Figure 4.

Figure 4

Each data point represents the time of introduction of the calibrated pulse of reactant gas. For room temperature reactions the standard low pressure reactors shown in the Low Pressure Reactor section are also used with these systems. When temperature control is needed, jacketed versions of these reactors are used with the temperature maintained by a constant temperature recirculating bath.