Butadiene production from bioethanol and acetaldehyde over tantalum oxide-supported spherical silica catalysts for circulating fluidized bed

• The effect of size and structural properties of Ta2O5/silica sphere was studied.
• The various ETB reaction conditions for Ta2O5/silica sphere were studied.
• Ta2O5/Q-6 catalyst showed good mechanical strength and catalytic performance.
• Ta2O5/Q-6 catalyst tested for hydrodynamic properties in the cold-bed CFB.

The chemical 1,3-butadiene (BD) is usually produced from ethanol and acetaldehyde (ethanol to BD, ETB) over Ta2O5/SiO2 catalyst in fixed-bed system. However, the ETB process has a short catalyst-regeneration cycle due to rapid deactivation of the catalyst by coke. To overcome this problem, a circulating fluidized-bed (CFB) reactor could be used in the ETB reaction for continuous regeneration of deactivated catalyst. The catalyst supplied to a CFB reactor must be spherical, show good catalytic performance, and be mechanically strong. In this study, a series of samples of Ta2O5 catalyst on silica spheres with different pore and particle sizes, were prepared. The catalysts were examined for mechanical strength by an attrition test and in ETB reaction in the fixed-bed reactor. The Ta2O5/Q-6 catalyst, with particles size of 75–150 μm, showed good mechanical strength and the best catalytic performance. This optimum spherical catalyst was tested to examine its hydrodynamic properties in a cold-bed CFB reactor.