3921 Shaker Hydrogenation Apparatus

3921 Shaker Hydrogenator shown with Explosion Proof Motor and Switch.

Materials to be treated in a Parr hydrogenatorare sealed in a reaction bottle with a catalyst and connected to a hydrogen reservoir. Air is removed either by evacuating the bottle or by flushing with hydrogen. Pressure is then applied from the reservoir and the bottle is shaken vigorously to initiate the reaction. The bottle can be heated or cooled during this process, if necessary.  After the reaction reaches the desired point, the shaker is stopped, the bottle  vented and the product and catalyst are recovered.

Progress of the reaction can be followed by observing the pressure drop in the system. For example, when using a 250 mL charge in a 500 mL bottle and drawing hydrogen from the standard 4-liter tank, the tank pressure will drop approximately 8 psi for each one-tenth mole of hydrogen consumed. The exact relationship between the pressure drop and the amount of hydrogen consumed can be determined by making a calibration run using a weighed amount of a compound whose hydrogen acceptance is known.

Convenient Valves and Fittings

Each apparatus is equipped with all necessary valves and fittings for admitting hydrogen to the bottle, for evacuating the bottle and for filling the hydrogen tank-all without disturbing the bottle connection. Separate gages show the bottle pressure and the tank pressure at all times. The four-liter gas tank, bottle holder and a sturdy shaker mechanism are arranged in a compact assembly on a steel base for convenient operation on a laboratory bench or in a hood.

The gas connection from the hydrogen tank to the reaction bottle is made with polypropylene tubing that extends directly into the bottle so that no metal parts come in contact with the charge. The tank itself, its valves and pressure gages are made of brass or bronze. These parts are well suited for use with hydrogen, but they must be replaced with a stainless steel tank and stainless valves if ammonia or other corrosive gases are to be used in the system. All of these valves have stainless stems, PTFE packing and replaceable Kel-F seats to ensure positive, leak-proof control in quantitative procedures. A smaller, one-liter brass tank is available for semimicro operations in which small amounts of gas must be measured. The regular valves are easily transferred to this smaller tank.

A 6-ft pressure hose is furnished with each apparatus for filling the hydrogen tank from a commercial gas cylinder. This can be attached easily to any gas pressure regulator or tank valve system.

Pressure Tested Bottles

Reaction bottles for these hydrogenators are offered in several sizes as listed in the table below. All are made of borosilicate glass and individually pressure tested to twice their specified maximum working pressure. Several of these bottles can be furnished with a tough outer fiberglass oating. These coated bottles are no stronger than the plain ones, but the fiberglass envelope will usually retain any broken glass and prevent the loss of valuable reactants in case of accidental breakage. When considering the listed bottle sizes it must be remembered that in most catalytic procedures the reaction bottle is filled only about half full to leave sufficient space for effective mixing.

Bottles for the larger 3921 Apparatus are made in several sizes from 1000 to 2500 mL all of which fit into the same bottle holder. One each of the plain 1000 and 2000 mL bottles is furnished with each 3921 Hydrogenator. These are carefully selected, machine blown bottles which, because of their large size, are restricted to 40 and 30 psig working pressures. If higher pressures up to 60 psig are required for treating large amounts of reactants, users are urged to purchase the special 2500 mL heavy duty bottle (72CA4) which is made specifically for this purpose. This is a hand blown, borosilicate glass bottle with an extra heavy wall that is much stronger than the standard machine-made bottles. Or, for reactions that can be handled satisfactorily in stainless steel, there is a 1700 mL bottle made of T304 Stainless Steel, which can be installed in any 3921 Apparatus. This bottle with a stainless steel cover and O-ring seal will withstand working pressures up to 65 psig.