Maleic anhydride production from n-butane over vanadyl-phosphate catalyst

Abstract

As a link in a chain of utilizing $C_4$ fractions used now as fuels in Korea for chemical feedstock, a reaction producing maleic anhydride from n-butane was studied experimentally. A fixed bed reactor immersed in salt bath was used to investigate the reaction mechanism, reaction rate and the effects of reaction temperature and space velocity on the yield of maleic anhydride. A catalyst composed of $V_2O_5$ and $P_2O_5$ was prepared, and the catalyst was characterized by determining the oxidation state of the vanadium and surface area of the catalyst and by inspecting the X-ray diffraction pattern. An assumed reaction mechanism with first order kinetics was tested to yield good agreements. ◁그림 삽입▷(원문을 참조하세요) The values of reaction rate constants $K_1$, $K_2$ and $K_3$ have the range from 0.42 to 1.1 1/sec, 0.17 to 0.7 1/sec and 0.32 to 2.3 1/sec, respectively at reaction temperatures ranging from 426 to 512 ℃. The yield of maleic anhydride was observed to increase as the reaction temperature lowered, and the space velocity became slower. In a series of experiments, the maximum yield of maleic anhydride was 40 per cent, which was in the range of the values reported in patents but somewhat lower value for commercial purpose. Hot spot formation was observed during the experiments, and maximum temperature difference in the reactor bed reached to 38 ℃. This suggests that a hot spot formation may raise serious problems when commercialized.