Patent GB-784681-A (GB)
Title: Improvements in and relating to the production of aromatic oxygen-containing compounds
Inventor: HARDING ANTHONY JOHN
Filed: 1954-03-19
Abstract: In a process for the production of para-diacetyl benzene in which feedstock comprising para-di-isopropyl benzene is subjected under substantially anhydrous conditions to oxidation with a gas comprising free oxygen at elevated temperatures, the oxidation is either (a) conducted directly in the substantial absence of meta-di-isopropyl benzene to give a product comprising a substantial amount of para-di-acetyl benzene using a catalyst comprising a salt or oxide of a metal selected from the group consisting of lead, manganese, iron, nickel, cobalt and copper, at a temperature above 100 DEG  C.; or (b) the feedstock contains at least 5 per cent by volume of meta-di-isopropyl benzene and the oxidation is carried out to give para-di-isopropyl benzene dihydroperoxide and is conducted in the presence of two alkaline stabilizing agents, one of which is a carbonate of an alkali metal or of an alkaline earth metal or magnesium and the second of which is an alkali metal or an alkaline earth metal or magnesium salt of a weak organic acid, at a temperature of up to 125 DEG  C., the resulting para-di-isopropyl benzene dihydroperoxide being separated off and heated so that it decomposes to give para-diacetyl-benzene as a major product.  The term "weak organic acid" means an acid weaker than acetic acid of which the alkali metal, alkaline earth and magnesium salts are at least partially soluble in the initial reaction mixture.  The product obtained by method (a) comprises a ,a ,a 1,a 1-tetra-methyl para-xylene diol, a ,a -dimethyl para-acetyl benzyl alcohol, para-di-acetyl benzene, para-acetyl benzoic acid and terephthalic acid and also compounds with one uncharged isopropyl radical, e.g. para-isopropyl a ,a -dimethyl benzyl alcohol and in addition para-di-isopropyl benzene mono- and di-hydroperoxides.  Catalysts mentioned include organic acid salts of the metals mentioned above which are soluble in the reaction mixture, e.g. toluates, acetates and stearates.  High temperatures and long reaction times favour the production of acetyl and carboxylic groups, short reaction times favour the formation of alcohol groups.  When manganous p-toluate and cupric acetate are employed under comparable conditions the former leads to the formation of more alcohol than ketone.  Inert solvents which may be employed include o-dichlorobenzene and tetrachloroethane.  In method (b) a peroxide oxidation initiator may be employed, e.g. di-isopropyl benzene dihydroperoxide, e.g. from a previous oxidation reaction. Catalysts which may be employed in the peroxidation reaction include copper or silver salts soluble in the reaction mixture, e.g. copper stearate, naphthenate or benzoate.  The para-di-isopropylbenzene dihydroperoxide may be heated alone or with an added metal compound, e.g. an oxide of lead, manganese, iron, nickel, cobalt and copper or salt thereof incapable of producing a pH of less than 1 in the reaction mixture.  The residue remaining after the removal of the para-dihydroperoxide may be treated with aqueous caustic soda to remove meta-diisopropylbenzene dihydroperoxide and returned to the oxidation stage.  The meta-dihydroperoxide may be separated by treating the aqueous caustic soda solution, e.g. with carbon dioxide and decomposed e.g. with aqueous sulphuric acid to resorcinol and acetone.  The para-diacetyl benzene may be converted by further oxidation to terephthalic acid.  In examples: para-di-acetyl benzene separates from the crude product obtained by distillation at reduced pressure of the mixture obtained by oxidizing para-diisopropyl benzene with air in the presence of lead acetate (1); and in similar processes cupric and plumbic acetates and manganous, ferric and cobaltous p-toluates are employed as catalysts and the proportions of alcoholic and ketonic groups in the reacted mixtures are determined by infra-red methods (2); in a similar process anhydrous manganese acetate is employed as catalyst and the presence of para-diacetyl benzene in the product is indicated by analysis and a mixture of sodium salts, from which terephthalic acid and para-acetyl benzoic acid is obtained by extracting the liquid product with caustic soda (3); a product containing para-diacetyl benzene and a ,a ,a 1,a 1-tetramethyl para-xylene diol is obtained by heating with lead acetate and diisopropyl benzene the dihydroperoxide obtained by treating a mixture of ortho, meta- and para-di-isopropyl benzenes with oxygen in the presence of sodium carbonate and stearate, separating the desired dihydroperoxide by extraction with acetone (4).  The first Provisional Specification relates to a process similar to (a) which is applied to an aromatic hydrocarbon of the general formula. <FORM:0784681/IV (a)/1> where R1 and R11 are alkyl groups in the absence of the two alkaline stabilizing substances though the use of a salt of an alkali metal and a weak acid, e.g. sodium acetate, is stated to be beneficial.  The second Provisional Specification refers to the distillation of di-isopropyl benzene to obtain a product containing a major proportion of para-di-isopropyl benzene together with some meta-isomer for use as starting material.  The use of a metal salt in a lower valency state, e.g. ferrous chloride, cuprous oxide, cobaltous hydroxide or lead monoxide to decompose the para-dihydroperoxide to paradiacetyl benzene and the oxidation thereof to terephthalic acid with nitric acid or an oxygen containing gas and decomposition with an acid catalyst, e.g. aqueous sulphuric acid to hydroquinone are also referred to.