Butadiene conversion, optimum catalyst

The epoxidation of non-allylic, or kinetically-hindered, olefins can be carried out using supported silver catalysts. While epoxidation does occur for unpromoted catalysts, the strength of olefin epoxide adsorption leads to low activity and selectivity, as well as irreversible catalyst fouling. The additon of certain alkali metal salts, such as CsCI, lowers the desorption energy of the olefin epoxide, permitting dramatic increases in activity, selectivity, and catalyst lifetime. In the case of butadiene, the addition of an optimum level of CsCI increases activity and selectivity from approximately 1 % butadiene conversion and 50% selectivity for epoxybutene to 15% conversion and 95% selectivity, respectively. 

The same authors 160) reported a process study of ra-butene oxidation to maleic anhydride using an unspecified vanadium catalyst. The catalyst was said to be different from that suitable for benzene oxidation. From the data presented, the reaction appears to be first order in hydrocarbon. A temperature of 430-470° was optimum. On the basis of this study the following conditions for oxidation of w-butenes were recommended butene concentration, 0.9-1.2% by volume temperature, 430-450° gas hourly space velocity, 4000. These conditions give a conversion of butenes of about 80%, a selectivity of 52%, and a yield C X 81100 of 41.6%. This relatively high yield, compared to that reported by others, may in part result from inclusion of about 8% butadiene in the feed. However, Societe d Electrochemie 160a) report C X SjlOO — 49% with butenes over a V-1.2 P catalyst at 470°. 

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