Metathesis of ethylene and butylene-2 to propylene with Mo on Hβ-Al2O3 catalysts

Reaction performance, acidic and basic properties, as well as reduction properties of various supported molybdenum catalysts for the metathesis of ethylene and butylene-2 to propylene were investigated by TPR and NH3-TPD techniques in a flow-reactor. Besides temperature, space velocity and pressure, the stability of a Mo/(Hβ-Al2O3) catalyst is strongly affected by the Mo loading, the calcination temperature and the hydrothermal treatment conditions. A suitable molybdenum loading on Hβ-Al2O3 is favorable to the stability of the catalyst that possesses suitable amount of acidity, which was determined by NH3-TPD measurements. The optimum preparation conditions of the Mo/(Hβ-Al2O3) catalyst are as follows: molybdenum content 3 wt.%, hydrothermal treatment and calcination at 550 °C for 2 h and 700 °C for 2 h, respectively. Thus, the optimal catalyst of 3Mo/(Hβ-Al2O3), designated as 3Mo/Hβ5502700, could keep a conversion of C4H8-2 at about 82% during 22 h of reaction time-on-stream under the following conditions: N2/C2H4=1.5, C2H4/C4H8-2=3/1, WHSV(C2H4+C4H8-2)=1 h−1, T=120 °C, and P=1.0 MPa. In addition, a suitable pressure, such as 0.5–1.0 MPa, and a low temperature, such as 35 °C, are beneficial for keeping the stability of the 3Mo/Hβ5502700 catalyst.