Patent GB-658179-A (GB)
Title: Oxidation of olefines
Inventor: HADLEY DAVID JAMES
IPC: B01J23/72
Filed: 1947-08-25
Abstract: Acrolein and methacrolein are obtained by oxidizing propylene and isobutene respectively with molecular oxygen-containing gases at elevated temperature, the reactants being passed over a contact material which comprises initially cupric oxide distributed on silica gel as support.  The reactants may be passed over the contact material in the presence of elementary selenium.  The preferred temperature range is 230 DEG  to 370 DEG  C.  The conversion rate is improved by heating the carrier charged with the cupric oxide to an elevated temperature, e.g. about 600 DEG  C. for about one hour before the gas mixture is passed over the catalyst.  When the mixture of reacting gases has an olefine content of about 10 per cent it is an advantage to allow said mixture in the absence of p  selenium to pass over the silica gel-cupric oxide mixture maintained at oxidation temperature, preferably after the latter has been previously pre-heated as above and then cooled.  This treatment in the absence of selenium is continued for a long period, e.g. for 24 hours, the olefines being oxidized to form unsaturated aldehyde and after this time selenium may be introduced into the reactor, for example by admixing selenium vapours with the gaseous reaction mixture.  The molecular oxygen is best applied in admixture with an inert gas such as nitrogen, carbon dioxide or steam.  The olefine content of the reactant gases is preferably from 1 per cent to about 12 per cent and the concentration of molecular oxygen should preferably be not substantially less than 10 per cent when the olefine content is about 2 per cent and not less than 15 per cent when the olefine content is about 10 per cent, although pure oxygen may be used. In examples: (1) granular silica gel is steeped in copper-nitrate solution and then dried and ignited at 450 DEG  C. in a current of nitrogen or air. The catalyst mixture is then heated to about 600 DEG  C. and then cooled.  A gas mixture containing about 2 per cent of the olefine is then introduced in conjunction with selenium vapours; (2) granular silica gel is heated and an excess of a boiling mixture of water and copper nitrate trihydrate then added.  The mixture is dried and then heated in a stream of air at 450 DEG  C.  The resulting copper oxide-silica gel mixture is placed in a helix of glass tubing maintained at 320 DEG  C. fitted with two inlets one of which accommodates a selenium reservoir which consists of a small glass cup suspended from a bung in the top of the inlet.  A mixture of propylene and air and containing 10 per cent of propylene is passed in via the inlet containing no selenium for one day, a small percentage of the propylene is converted to acrolein.  The whole of the gas stream is then diverted over the selenium reservoir maintained at 320 DEG  C. when the yield of acrolein increases. After one day the flow over the selenium is reduced to one quarter of the total, the remainder of the flow byepassing the selenium; (3) the contact material is prepared as in (2) and is then given a heat treatment at 600 DEG  C. before use, it is then exposed to a stream of propylene and air in the helical reactor but without the addition of selenium; (4) the contact material is prepared as in (2) and the same gas mixture is introduced into the reactor at 320 DEG  C. over the contact material after the whole of the gas stream has passed over the selenium maintained at 320 DEG  C. in the reservoir; (5) example (2) is repeated, except that the catalyst mixture is first subjected to a heat treatment at 600 DEG  C., the inlet gas stream is however finally doubled and one quarter of it passed over the selenium; (6) the catalyst is prepared as in (2) and is then heated for 1 hour at 600 DEG  C. and a mixture of isobutene, oxygen and carbon dioxide is then passed over the catalyst at 320 DEG  C., one third of the gas mixture having previously been diverted to pass over a reservoir containing selenium at 320 DEG  C., the isobutene is converted into methacrolein in good yield; (7) example (6) is repeated except that the catalyst is preheated to 600 DEG  C. for 1 1/2 hours and a mixture of propylene, oxygen and carbon dioxide is used.  Specifications 397,161, 625,330, 640,383, 648,386 and 658,240, [Group III], and U.S.A.  Specification 2,383,711 are referred to. According to the Provisional Specification the invention is applicable to the oxidation of any olefine of the general formula H2C.CR1 : CR2R3, wherein R1, R1, R2 and R3 are hydrogen atoms or alkyl groups.