As an important aspect of shape-selectivity catalysis, the significance of diffusion in conversion, deactivation and product selectivity over molecular sieve catalysts have been recognized, but still cannot been interpreted quantitatively and explicitly.
Recently, we performed direct tracking of molecular diffusion in SAPO-34 catalyst during the methanol-to-olefins (MTO) reaction by combining the MTO reaction with the diffusivity evaluation by a pesudo-gas chromatography method, which was operated in one catalyst bed under the real reaction condition. Diffusion property measurements were manipulated over the working catalyst along with the reaction to reflect the evolution in shape-selectivity catalysis in real time.
This work was published in ACS Catalysis on July 10.
The experimental residence time distribution curve (E(t)) of CH4, C2H6, C3H8and i-C4H10probing on SAPO-34 catalyst bed during MTO reaction. Insert: coke amount and distribution. MA, NA and PA represent methyl-substituted benzene, naphthalenes and polycyclic aromatics, respectively.
This work demonstrates that the configurational diffusion hinderance in SAPO-34 due to the accumulation of organic species retained in the catalyst, corresponds well the evolution of methanol conversion and product distribution.
More importantly, these understandings enrich and rationalize the knowledge of shape-selective catalysis and provide the scientific basis for reaction modulation and optimization in MTO process.
This work was supported by National Natural Science Foundation of China,the Key Research Program of Frontier Sciences, CAS, the International Partnership Program of Chinese Academy of Sciences and Dalian Institute of Chemical Physics. (Text by HAN jingfeng)
Simultaneous Evaluation of Reaction and Diffusion over Molecular Sieves for Shape-Selective Catalysis. Jingfeng Han, Zhiqiang Liu, Hua Li, Jiawei Zhong, Wenna Zhang, Jindou Huang, Anmin Zheng, Yingxu Wei*, Zhongmin Liu*, 10(15):8727-8735, 2020.
