from first principles PP-I-1

OP-III-31On Mechanisms of Oxidation of 1,3-Butadieneon Pd-Te Catalysts in Polar SolventsKuznetsova N.I. 1 , Trebushat D.V. 1 , Kuznetsova L.I. 1 , Zudin V.N. 1 , Kajitani H. 2 ,Utsunomiya M. 2 , Takahashi K. 21 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia2 Mitsubishi Chemical Corporation, Kurashiki, Okayama, Japankuznina@catalysis.ruApart from high reactivity and wide use in polymerization, 1,3-butadiene (BD) is aconvenient feedstock for obtaining variable oxygenates, such as epoxybutene, maleicanhydride, furan, 1,4-diacetoxy-2-butene. Liquid-phase oxidations of BD follow three typicalmechanisms: (1) oxygenation directed to one of double bonds, (2) concert oxidative additionto 1,4-positions , and (3) radical chain mechanism. It has been shown that Pd-Te catalysts areable to participate in each single type of these reactions in appropriate solvent and conditions.Adsorption of oxygen on well-reduced Pd-Te/C catalysts resulted in electron transfer fromPd 0 and formation of surface reactive species capable of oxidizing BD. Suspended in a polarorganic solvent, the Pd-Te catalyst gave rise to formation of methyl vinyl ketone, furan andcroton aldehyde, the last compound being also produced on pure supported Pd. Water wasnecessary for the oxidation to proceed, and acid additives accelerated oxidation withpreferable formation of furan.Stabilization of intermediate and final products are required to realize oxidative 1,4-additionto BD. 1,4-Diacetoxy-2-butene is produced on Pd-Te catalysts in acetic acid [1]. We observedformation of 1,4-dimetoxy-2-butene from BD in methyl alcohol. Application of silica support,instead of carbon, or addition of sulfuric acid to solvent gave positive effect on etherproduction. Optimal temperature, water and acid additives appeared sufficient for conversionof BD predominantly to 1,4-dimetoxy-2-butene and allenic alcohol methyl ether.At a large BD loading, radical chain process is developed to form peroxides and finally1,2- and 1,4-butenedions together with numerous secondary products. The Pd-Te/C catalystintroduced some changes into the product composition increasing portion of 1,4-oxygenatesin the products.References:[1] US Patent 3 755 423 ; US Patent 3 922 300 ; K.Takehira, H.Mimoun, I.Seree De Roch,J. Catal. 58 (1979) 155.75