Fixed bed reactor and method for preparing maleic anhydride by virtue of normal butane oxidation

The invention discloses a fixed bed reactor and a method for preparing maleic anhydride by virtue of normal butane oxidation. A gas inlet is formed at one end of a reactor body; a gas pre-distributer is arranged in one end of the reactor body and is connected with the gas inlet; a discharge port is arranged at the other end of the reactor body; a heat-transfer medium molten salt outlet and a heat-transfer medium molten salt inlet are formed on the side wall of the reactor body; a plurality of catalyst filling pipes are arranged in the reactor body; gas distributing plates are arranged at both ends of the plurality of catalyst filling pipes respectively, wherein a second homogenizing space is arranged between one gas distributing plate and the gas inlet while a first homogenizing space is arranged between the other gas distributing plate and the discharge port; the molten salt as a heat-transfer medium is arranged among the plurality of catalyst filling pipes; and a fluid director is connected with the inner wall of one end of the reactor body through a support rod. The fixed bed reactor provided by the invention has the advantages that the dimension of a region with a low gas velocity is reduced; and the influence of an uneven local impact on the distributing plates is decreased, so that the operation stability is improved. Therefore, the fixed bed reactor can be applied to the industrial production of maleic anhydride.