This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the fractional conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from fractional conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results clearly indicate that an apt apex angle exists in tapered-in reactors in which the fractional conversion reaches a maximum value; while the variations of the apex angle slightly affect the fractional conversion in tapered-out fluidized beds. Increasing the residence time of the gas phase in the upper section of tapered-in beds has positive influences on the fractional conversion, while a further decrease in the gas phase velocity in the tapered-in reactors has a negative effect on the fractional conversion. Moreover, higher bed pressure drop was observed in tapered-in reactors than that in the columnar and tapered-out ones. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.