Patent GB-462714-A (GB)
Title: Improvements in or relating to chemical processes in the gaseous or vaporous phase
IPC: C07C51/56
Filed: 1935-06-12
Abstract: In carrying out endothermic reactions in the gaseous or vapour phase and wherein the pressure is maintained substantially below atmospheric in at least the later part of the reaction zone, e.g. the production of ketene or acetic anhydride, or propionic or butyric anhydrides from acetic acid &c., or the cracking of hydrocarbons to produce hydrocarbons of lower molecular weight or lower hydrogen content, e.g. the production of acetylene from methane, some or all of the heat is supplied to the material in the gas or vapour phase and thereafter a drop in pressure to below atmospheric is obtained by means of a constriction in the system and a suction pump. Preferably, the constriction consists of a perforated plate placed at a suitable point in the system. Undesirable decomposition of the reactants, or side-reactions are stated to be avoided.  The starting material may be preheated, the pressure reduced and the material further preheated before passing to the reaction zone, or the material may be passed to the reaction zone without further preheating or the reduction in pressure may be effected at a point in the reaction zone.  For example, acetic acid vapour may be preheated to 400--500 DEG  C. at atmospheric pressure, the pressure reduced to 250--300 mm. of mercury and the vapour further preheated to 600--700 DEG  C. or 700--850 DEG  C.  If desired, the pressure may be further reduced, e.g. to 10--30 mm. of mercury before passing to the reaction zone. Specifications 256,663, [Class 2 (iii)], and 458,160 are referred to.ALSO:In carrying out endothermic reactions in the gaseous or vapour phase and wherein the pressure is maintained substantially below atmospheric in at least the later part of the reaction zone, some or all of the heat is supplied to the material in the gas or vapour phase and thereafter a drop in pressure to below atmospheric is obtained by means of a construction in the system and a suction pump.  Preferably, the constriction consists of a perforated plate placed at a suitable point in the system. Undesirable decomposition of the reactants or side-reactions are stated to be avoided.  The starting material may be preheated, the pressure reduced and the material further preheated before passing to the reaction zone or the material may be passed to the reaction zone without further preheating or the reduction in pressure may be effected at a point in the reaction zone.  The process may be applied to the production of ketone or acetic anhydride, or propionic or butyric anhydrides from acetic acid &c., or to the cracking of hydrocarbons to obtain hydrocarbons of lower molecular weight or lower hydrogen content, e.g. the production of acetylene from methane.  For example, acetic acid vapour may be preheated to 400--500 DEG  C. at atmospheric pressure, the pressure reduced to 250--300 mm. of mercury, and the vapour further preheated to 600--700 DEG  C. or 700--850 DEG  C.  If desired the pressure may be further reduced, e.g. to 10--30 mm. of mercury before passing to the reaction zone.  Specifications 256,663, [Class 2 (iii)], and 458,160, [Group IV], are referred to.