| 摘要 |
<p>1468940 Carboxylic acid anhydrides HALCON INTERNATIONAL Inc 3 Sept 1974 [4 Sept 1973 8 May 1974] 38511/74 Heading C2C An anhydride of a monocarboxylic acid is prepared by reacting a carboxylic ester RCOOR (Reaction I) or an ether ROR (Reaction II) with an acyl halide RCOX under substantially anhydrous conditions; X is an iodine or bromine atom, the Rs may be the same or different, and each R is a monovalent hydrocarbyl radical which may be substituted, any substituent being inert under the reaction conditions. The acyl halide may be produced by carbonylation of a hydrocarbyl halide (Reaction III) at superatmospheric pressure, using preferably a Group VIII noble metal as catalyst and preferably also a promoter comprising an element of Groups IA, IIA, IIIA, IVB or VIB, a non-noble metal of Group VIII or a metal of the lanthanide or actinide groups. Reaction III may be carried out in a separate reaction zone from reactions I or II, and the hydrocarbyl halide RX formed in I or II recycled to III. Alternatively the anhydride forming and carbonylation reactions may be combined in a single reaction zone; the hydrocarbyl halide, of which no net consumption takes place, may be formed in situ by adding an organic or inorganic halide or elemental bromine or iodine. Reaction II proceeds in two stages, the first step, ROR + RCOX = RCOOR + RX, being followed by I as second step; ester so formed as intermediate may be recovered as by-product. The formation of acetic, propionic, caprylic and benzoic anhydrides from, respectively, methyl acetate, ethyl propionate, heptyl caprylate and phenyl benzoate is exemplified.</p> |
