Olefin oxidation

摘要

In the liquid phase oxidation of olefins with a substantially anhydrous organic solution containing a platinum metal and halogen in presence of oxygen at 30-300 DEG C., deposits of the metal upon the apparatus surface are prevented by incorporating in said solution between 1 and 20 weight per cent of a finely divided inert solid. The solid, impregnated with the precipitated metal during the oxidation or distillation, is recycled with the catalyst solution. Suitable solids are silicas, preferably silica gel, silicon carbide, carbons, and titania, preferably having a specific surface area of 2-1000 m2/g, and generally of 3-400 mesh (U.S. Standard). The metal may be Pt, Ir, Os, Rh, Ru or, preferably, Pd, usually in amounts of 0.001-5 weight per cent of the solution. It may be added as metal, soluble salt or oxide or chelate. The halogen may be added as Cl or Br; hydrogen, alkali, ammonium or platinum metal halide; or organic halide or phosgene. The water content of the reaction medium should be less than 20 weight per cent and reaction water formed is removed by distilling. Aliphatic alcohols of C1- 25 are preferred solvents for oxidation of olefins to acetals, a strong mineral acid in amount of 0.1-5% being added. Carboxylic acids are used in preparing unsaturated esters. Soluble carboxylates of alkalis, alkaline earths, and noble metals of Group VIII, or redox metal salts, e.g. halides, may also be present. Additional solvents include formamide, dimethyl formamide, hydrocarbons, and chlorhydrocarbons. Other oxidizing agents may also be used such as nitrogen oxides, nitrates or nitrites. Vanadium compounds may be added to catalyse oxidation of oxalic acid formed as a by-product.