The Fischer-Tropsch activity of supported iron catalysts prepared via electrochemical techniques has been evaluated as a function of potassium addition. Catalyst pretreatment in 0.09, 0.18, and 0.27 M K2C03 solutions generated potassium levels of 1.7, 2.8, and 3.9 wt %, respectively. Pretreatment in 0.18 KOH provided a catalyst with 2.3 wt % potassium and facilitated comparison of the effects of the basicity of the pretreatment solution upon catalyst activity. A maximum in catalyst activity and CO conversion was noted upon increasing K content, followed by a sharp decline in activity at potassium levels in excess of the maximum. The hydrogenation ability of the catalyst decreased, and a shift to higher molecular weight products was observed, with increasing potassium content. The type of pretreatment solution had little effect on the catalyst activity or the product selectivity.

No abstract

An improved method for the elcctrode-mcdiated oxidations of olefins by palladium(I1) is dcscribed. Current efficiencies from 80% to 95% werc obtained in oxidations of I-dcccnc, styrene, tt.trtls-2-octcne, and cyclohexene in which pcrchloric acid was added to a chloride-free solution of a palladiun~(I1) acctate catalyst. The palladiunl(0) was reoxidized to palladium(I1) by reaction with catalytic amounts of benzoquinone, which was, in turn, regenerated by anodic oxidation. Addition of varying amounts of pcrchloric acid did not affect the current efficiency but accelerated the oxidation reaction, up to a concentration of approximately 0. I5 M. Thc current efficiency remained high (>80%) over the course of the electrode-mediated oxidations of I-decene, trcltls-2-octcne, and cyclohexenc. At thc end of the reactions. when the substrate was depleted, a drastic dccrease in the current was observed, indicating that the catalytic cycle leading to product was primarily responsible for the electrochemical reaction. It also was shown that the rates of the electrochemical reactions were generally slower than those of homogeneous reactions in which a stoichiometric amount of benzoquinone was used, indicating that the elcctroche~nical regeneration of benzoquinonc was mass transport limited at the highest concentrations of pcrchloric acid. This is in contrast to othcr rcports in the literature that suggested that the homogencous (non-electrochemic:~l) reactions were actually slower. Reasons for the discrepancy betwccn thesc results arc discussed. pour I'ensemble des oxydations assistees par une Clcctrode. A la fin de reactions, lorsqu'il ne reste plus de substrat, on observe une dra~natique diminution du courant qui indique que le cycle catalytique conduisant au produit est le principal responsable de la rtaction Clectrochimique. On a montrC que la vitesse des reactions electrochimiq~~es est g&n&ralement plus lentc que les reactions homogenes dans lesquelles on utilise unc quantitd stocchiornttrique de benzoquinone; ceci i n d i q~~e que, 5 des concentrations ClevCes d'acide perchlorique, la rCgCndration clectrochi~nique de la benzoquinonc est li~nittc par un transport de Iiiasse. Cctte situation est en opposition avcc d'autrcs rapports parus dans la littkrature qui suggeraient que Ics reactions homogiines (non-Clectrocliin~iq~~es) sont clc fait plus Icntcs. On discute des raisons pouvant expliquer ccs diff6rcnces.[Traduit par la redaction]

Fischer-Tropsch synthesis produces both hydrocarbon and oxygenated products (oxygenates) by reducing CO with hydrogen on a suitable catalyst, among which supported iron, cobalt, and rhodium are examples. Recently we have carried out Fischer-Tropsch reactions on a potassium-promoted supported-iron catalyst using perdeuterated ethylene as an additive to the H2/CO feed. This was done as a part of a study to investigate the special role that ethylene is claimed to have in the Fischer-Tropsch process, as suggested, in part, by the low concentration of ethylene that is often observed in the products of this reaction.1 The reaction products were subjected to scrupulous GC-CIMS analysis in order

104ChemInform Abstract Addition of acids such as perchloric acid enhances the palladium-catalyzed oxidation of the alkenes (I) in the presence of p-benzoquinone to give the carbonyl compounds (II) -(IV).