Patent GB-728821-A (GB)
Title: Oxidation catalyst and its preparation
IPC: C07D301/10
Filed: 1952-02-28
Abstract: Ethylene oxide is prepared by oxidation of ethylene with oxygen or oxygen-containing gases or both in the presence of a silver alloy catalyst mounted on a highly heat conducting metal base, characterized in that the silver is originally present as an alloy of silver and an alkaline earth metal which, as described and claimed in Specification 663,257, [Group III], is activated by removal of a portion of the alkaline earth metal from the alloy (see Group III). The reaction is carried out in the range 240-320 DEG  C., preferably 260-300 DEG  C.  Examples are given.ALSO:<PICT:0728821/III/1> <PICT:0728821/III/2> A catalyst for the production of ethylene oxide consists of a silver alloy mounted on a highly heat conducting metal base, characterized in that the silver is originally present as an alloy of silver and an alkaline earth metal which, as described and claimed in Specification 663,257, is activated by removal of a portion <PICT:0728821/III/3> of the alkaline earth metal present in the alloy.  The proportion of alkaline earth metal originally present in the alloy may be from 1-75 per cent., preferably 5-15 or 5-10 per cent., best 8.5 per cent., and from about 5 per cent. to substantially all may be removed.  Details of preferred thicknesses of metal base and quantity of alloy mounted thereon are given.  The alloy may be ground, activated by solution of the alkaline earth metal, e.g. with acetic acid, washed, dried, mixed with glycol and painted on to the base, or mounting may be performed before a similar activation process, by means of a hydraulic press, rolling mills or impact machine or by dipping the metal base into molten alloy. The invention may be used in the reactor shown in Fig. 1.  2 is a reaction tube surrounded by a cooling jacket 1 and contains catalyst elements 6 alternately packed with spacers 8, as shown in perspective in Fig. 5.  The spacers have a gap 9 and an expanded radius greater than that of the tube 2 so that a good thermal seal is effected.  The reactants enter at 12 and 13, flow through the series of catalyst elements via the holes 7 and 10 over a thermostat 11, and the product is removed at 14.  Catalyst elements may be constructed with a cross-section as shown in Fig. 7 in which 18 is a sheet of heat-conducting metal and 19 is a thin metal base supporting the catalyst 20.  Other apparatus is shown in which the catalyst elements are in the form of fins in thermal contact with a cooling medium.ALSO:An alloy of silver and alkaline earth metal or metals (calcium, magnesium, barium and strontium being mentioned), catalytically activated by removal of a portion of the alkaline earth metal, is mounted on a highly heat-conducting metal base, e.g. of silver, silver-plated copper or aluminium.  The original alloy may contain 1-75 per cent, preferably 1-15 per cent or 1-10 per cent, best 8.5 per cent of alkaline earth metal, and from about 5 per cent to substantially all may be removed.  The original alloy may be produced in situ if desired, by dipping a silver base in molten alkaline earth metal.  A metal base (which need not contain silver) may be dipped into a bath of the original alloy and if desired subsequently annealed, generally at 440-745 DEG  C.  The removal of the alkaline earth metal is performed as described and claimed in Specification 663,257, [Group III], the action of steam alone, water at an elevated temperature in an autoclave followed by steam, and water or steam followed by aqueous acetic acid being particularly described.