The Unique Role of CaO in Stabilizing the Pt/Al2O3 Catalyst for the Dehydrogenation of Cyclohexane

• Published in: ChemCatChem 2012-09, Vol.4 (9), p.1376-1381
• Main Authors: Yu, Jiafeng, Wang, Rui, Ren, Shiyuan, Sun, Xiaoyan, Chen, Chunlin, Ge, Qingjie, Fang, Wen, Zhang, Jian, Xu, Hengyong, Su, Dang Sheng
• Format: Article
• Language: English
• Subjects: calcium; coke; dehydrogenation; heterogeneous catalysis; platinum
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201200067

Coke‐induced deactivation is one of the major challenges in the field of heterogeneous catalysis. Herein, the performance of the Pt/Al2O3 catalyst for the hydrogen‐free dehydrogenation of cyclohexane was improved by doping with a small amount of Ca. The Ca‐modified Pt/Al2O3 catalyst exhibited a cyclohexane conversion of 97.0 % and maintained a conversion above 75 % after 48 h, whilst the unmodified catalyst was deactivated from 87.0 to 2.7 % under the same conditions. Characterization techniques, including in situ DRIFT, XPS, thermal analysis, and temperature‐programmed techniques, revealed that the presence of Ca effectively suppressed the deep dehydrogenation of H‐rich carbonaceous components and promoted coke desorption by increasing the H/C ratio of H‐deficient coke. This promotion effect of Ca was also associated with neutralizing the residual Cl ions and promoting immediate dehydrogenation. Catalyst body modification: The stability of the traditional Pt/Al2O3 catalyst was improved by doping with Ca, which effectively suppressed the deep dehydrogenation of H‐rich carbonaceous components in the graphitic structure. Ca also promoted coke desorption by increasing the H/C ratio of H‐deficient coke, thus favoring superior stability.