SELECTIVE SYNTHESIS OF MALEIC-ANHYDRIDE BY SPATIAL SEPARATION OF N-BUTANE OXIDATION AND CATALYST REOXIDATION

The selective oxidation and ammoxidation of hydrocarbons in fixed-bed or fluidized-bed reactors is conventionally characterized by the simul taneous presence of oxygen gas and hydrocarbon vapor at the active sit es of the catalyst. In order to increase the selectivity it has been s uggested (Sze and Gelbein, 1976; Contractor and Sleight, 1987; Contrac tor, 1988) to separate the reaction into two parts; i.e. a first step where the catalyst chemisorbs oxygen and a second step, where the oxid ized catalyst reacts with the hydrocarbons. In the present work this c oncept has been tested on the laboratory scale. The oxidation of n-but ane to maleic anhydride (MA) has been taken as an example. The reactio n step was carried out in a riser of a circulating fluidized bed, the solids return line of which was used to implement a regenerator fluidi zed bed for the reoxidation step. A model of this reactor has been dev eloped which takes the oxygen loading on the catalyst particles into a ccount. Scale up calculations show that high solids circulation rates are necessary which, in turn, demand a high attrition-resistance of th e catalyst. Copyright (C) 1997 Elsevier Science Ltd.