Patent GB-921443-A (GB)
Title: Improvements in or relating to the manufacture of maleic anhydride
IPC: C07C31/20
Filed: 1959-07-06
Abstract: <PICT:0921443/III/1> Crude maleic anhydride is introduced through pipe 14 into the top section of a container having superposed plates A, B, C, each of which is heated to the boiling-point of maleic anhydride; the liquid anhydride is maintained on plate A for a period of time and then passes, through overflow pipe 9, on to plate B. After a period on plate B the liquid flows down to plate C.  During this process, the quinones polymerize, or co-polymerize with maleic anhydride, to form tarry products, and maleic acid is converted into the anhydride, so that when the treated anhydride, withdrawn from plate C via conduit 11, is submitted to distillation, pure maleic anhydride is obtained as distillate.  Plates A and B each have a slot 2 surrounded by a sleeve 3 on which a bell-cap 5 is mounted.  A diametrical baffle 4, extending nearly across plates A and B, prevents rapid circulation of liquid.  There are two heating-pipes 6 associated with these two plates; these heaters being arranged on opposite sides of baffle 4.  Plate C is provided with a spiral-baffle 10; this plate is heated by a heating-chamber at the base of the container.  The process is preferably carried out at a temperature of 140 DEG  to 160 DEG C. and a pressure of 100 to 200 mm. Hg.  Vapours of crude maleic anhydride rise through slots 2, and pass through conduit 15 to the first of two condensers, connected in series.  The condensate formed in the first condenser, which is maintained at 120 DEG  to 130 DEG C., is returned to plate B; and the condensate formed in the second condenser, at 55 DEG -60 DEG C., is returned to plate A.  The entire apparatus is suitably made of stainless molybdenum steel.ALSO:<FORM:0921443/IV(a)/1> Crude maleic anhydride is introduced through pipe 14 into the top section of a container having superposed plates A, B, C, each of which is heated to the boiling-point of maleic anhydride; the liquid anhydride remains on plate A for a period of time and then passes, through pipe 9, on to plate B, and then after a period on plate B, the liquid flows down to plate C.  During this process, the quinones polymerize, or co-polymerize with maleic anhydride, to form tarry products, and maleic acid is converted into the anhydride, so that when the treated anhydride, withdrawn from plate C via conduit 11, is submitted to distillation, pure maleic anhydride is obtained as distillate.  The process is preferably carried out at a temperature of 140 DEG  to 160 DEG C., and a pressure of 100 to 200 mm. Hg.  Plates A and B each have a slot 2 surrounded by a sleeve 3 on which a beli-cap 5 is mounted.  A diametrical baffle 4, extending nearly across each of plates A and B, prevents rapid circulation of liquid.  There are two heating-pipes 6 associated with these two plates; these heaters being disposed on opposite sides of baffle 4.  Plate C is provided with a spiral-baffle 10; this plate is heated by a heating-chamber at the base of the container.  Vapours of crude maleic anhydride rise through slots 2, and pass through conduit 15 to the first of two condensers, connected in series.  The condensate formed in the first condenser, which is maintained at 120 DEG  to 130 DEG C., is returned to plate B; and the condensate formed in the second condenser, at 55 DEG -60 DEG C., is returned to plate A.  The entire apparatus is suitably made of stainless molybdenum steel.