Hydrogenation apparatus for high-pressure

Fig. 3 Apparatus for high pressure hydrogenation. A, autoclave B, hydrogen inlet valve C, pressure release valve D, pressure gauge E, heating mantle F rocking device.

A solution of 24 g. (0.6 mole) of sodium hydroxide, 100 ml. of water, and 55 g. (0.5 mole) of resorcinol is placed in an apparatus for high-pressure hydrogenation together with 10 g. of reduced... 

A solution of 108 g. (0.5 inole) of diethyl ethoxymethylene-malonate (Note 1) in 100 ml. of commercial absolute alcohol is placed in an apparatus for high-pressure hydrogenation together with 10 g. of Raney nickel catalyst (Note 2). The pressure in the bomb is raised to 1000-1500 lb. with hydrogen, and the temperature is adjusted to 45° (Note 3). The bomb is shaken, and the reaction is allowed to proceed for 12-20 hours, during which time 0.5 mole of hydrogen is absorbed. 

Apparatus for hydrogenation at atmospheric pressure, 470-473 for high pressure hydrogenation, 868-870... 

The trend in hydrogenation practice appears to be toward the use of higher pressures, where the apparatus is smaller. Under such conditions, the reaction velocity is increased the equilibrium positions are made more favorable the reaction path is better defined, with fewer side reactions and heating and cooling and heat interchange are facilitated. The design and construction of equipment for high-pressure work are, however, somewhat more complicated than for low-pressure operations. Alloy steels are by far the most common materials of construction. 

The following account refers primarily to commercial apparatus suitable for conducting hydrogenations under pressime the apparatus can, of coimse, be employed for other reactions under high pressures, but slight modifications of experimental procedime wiU probably be necessary. 

Fig. 1.35 XRD pattern of MgH hydride after milling and annealing in Sieverts apparatus during thermal stabilization of the measuring system for 45 min at 300, 325, and 350°C under high pressure of hydrogen (4.5 MPa)...

Hydrogenation at High Pressures. These are carried out almost exclusively in autoclaves. Autoclaves are much like the apparatus previously shown, but with much more steel to withstand the high pressures and temperatures they receive. Most of them have built-in heating elements and temperature indicators. Yes, they are very expensive, I have seen some homemade units that functioned quite effectively but I do not recommend that you try to build one. If you do try to build one, know what extremities the unit will be subject to and get professional advice and assistance for construction. Because medium and no pressure hydrogenations are so effective, I will not elaborate on high pressure systems any further. 

After the hydrogenation is over and the apparatus is cold the excessive pressure is bled off. In high-temperature high-pressure hydrogenations carried out in robust autoclaves it takes considerable time for the assembly to cool down. If correct reading of the final pressure is necessary it is advisable to let the autoclave cool overnight. 

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