Patent GB-1007295-A (GB)
Title: Hydrogenation of dinitrotoluene to tolylene diamine
IPC: C07C209/36
Filed: 1964-03-05
Abstract: Tolylene diamine is prepared by (1) supplying a slurry of dinitro toluene and Raney nickel in an inert diluent under high pressure into a first feed zone 1, (2) introducing a further quantity of the inert diluent into the first feed zone under high pressure thereby conveying the slurry from the first feed zone to a <PICT:1007295/C2/1> second feed zone 12 connected directly to a hydrogenator 13 under high pressure, (3) maintaining the high pressure in the second feed zone substantially constant, and (4) relieving the pressure in the first feed zone and continuously repeating the sequence of steps set forth. The temperature is preferably in the range 80-225 DEG  C. in the pressure from 50-200 atmospheres.  In an example, a slurry of dinitrotoluene and Raney nickel in, methanol, is introduced through valve 3 and check valve 5 into the first conduit 7, some of which will flow back into second conduit 9 but cannot reach the pump because the volumetric capacity of the second conduit 9 is greater than the size of the cylinder 21 of the pump 17.  The slurry enters the first conduit 7 only when the piston 23 is drawn from the cylinder 21.  The slurry then present within the first feed zone 1 is prevented from moving in the reverse direction by the unidirectional check valve 5.  The piston 23 is then actuated and forces the methanol in the cylinder 21 through discharge passage 25 and through the second conduit 9 under extremely high pressure, consequently forcing the slurry through unidirectional check valve 11 into the second feed zone 12 and then into the hydrogenator 13.  When the piston 23 is drawn from the cylinder 21, methanol enters the cylinder through inlet passage 27 and the third conduit 29.  The rate of flow of the methanol is determined by the opening of the adjusting needle valve 35 and this rate is indicated on the rotameter 33.  When the piston is actuated to pump the methanol from the pump, the unidirectional check valve 31 prevents the methanol from returning through the rotameter 33 and through adjusting needle valve 35.  Thus, during the suction stroke of the piston 23, the first feed zone 1 fills with slurry and simultaneously, the cylinder 21 fills with methanol.  On the pressure stroke, the highly erosive slurry moves from the first feed zone 1 through the first conduit 7 into the second feed zone 12 and into the hydrogenator 13.  The pressure within the second feed zone 12 and the hydrogenator is maintained by the unidirectional check valve 11. Thus the highly erosive slurry is supplied to the hydrogenator at high pressures without the need for passing the slurry through a pump.  The hydrogenator 13 generally consists of a battery of pressure reactors arranged in series provided with cooling means, preferably two separate sheaves of water tubes. Also provided is a means for introducing hydrogen under substantial pressure and an outlet for hydrogen and for the product solution.  The hydrogen is introduced under pressures within the range from 150 to 200 atmospheres.  Examples of other nitro compounds are nitrobenzene, dinitrophenyl, dinitronaphthalene, 4,41 - dinitrodiphenylmethane, dinitrohexane and dinitrocyclohexane.