Development of a Two Beds Circulating Fluidized Bed Reactor System for Non-Oxidative Aromatization of Methane over Mo/HZSM-5 Catalyst

The non-oxidative aromatization of methane provides a promising route of direct methane conversion to valuable aromatics and has been extensively studied from both fundamental and applicative points of view since its first report in 1993. Mo/HZSM-5 has been well recognized the most promising catalyst for the reaction, but it suffers from severe deactivation due to coking. On the other hand, at catalyst-working temperatures and non-oxidative conditions coking seems unavoidable. Thus the most practical solution to the deactivation problem is to develop a highly efficient, continuous regeneration technology to maintain the catalyst activity under operational conditions. Over the past thirteen years our team has been focusing its effort on the development of a really applicable technology for regeneration of coked Mo/HZSM-5 catalyst. Sustained effort has brought us the following findings of practical significance. 1) The high initial activity of Mo/HZSM-5 can be maintained via its cyclic regeneration in H₂ at 973-1073 K, and the H₂-regeneration approach is now well recognized to be the only practical way of reactivating coked Mo/HZSM-5 catalyst. 2) Continuous H₂ regeneration can be easily realized in a two-bed circulating fluidized bed reactor and the high initial activity of Mo/HZSDM-5 can be maintained at 1073 K and superficial velocities for several hours without addition of any fresh catalyst. 3) a binder-free, well shaped fluidizable Mo/HZSM-5 has been developed and successfully tested in a two beds circulating fluidized bed reactor system. In this presentation we will give a detailed description of how the major operating parameters are determined including temperature, space velocity and the mean residence times of the catalyst in the methane converter and regenerator, and of how the catalyst-circulating rate is precisely controlled by using a screw-type feeder.  Some achievements on the fundamentals of the catalytic system will be also presented.

References

1) Xu et al., Chem. Eng. Proc., 72(2013)90-102.

2) Xu et al., J. Natural Gas Chem., 21(2012)729-744.

3). Xu et al., Chem. Eng. J., 168(2011)390-402.