Journal
NEW JOURNAL OF CHEMISTRY
Volume 45, Issue 5, Pages 2820-2829Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/d0nj05190j
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Funding
- National Natural Science Foundation of China [21972011, 22008013]
- Petro China Innovation Foundation [2018D-5007-0401]
- Six Talent Peaks program (Jiangsu Province) [2018-XCL-100]
- Research and Practice Innovation plan for graduate Students in Innovative Engineering (Jiangsu Province) [SJCX20_0964]
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The study demonstrated that Pt catalysts supported on ZSM-22 zeolites treated with citric acid showed enhanced catalytic activity in the hydroisomerization of n-dodecane, mainly due to the increased Brønsted acid sites on the treated zeolites.Pt/ZSM-22-CA-2 and Pt/ZSM-22-CA-3 exhibited similar catalytic activity and yield, with different C-12-isomers distribution, attributed to the different ratios between accessible Pt sites and B acidic sites.
In this study, Pt catalysts on a series of ZSM-22 zeolites treated with citric (CA) solution with different molar concentrations (Pt/ZSM-22-CA-x, x = 0,1, 2, and 3) were prepared, and evaluated in the hydroisomerization of n-dodecane. The CA-treated ZSM-22 zeolite had little change in the morphology, regardless of the molar concentration of the CA solution used. The prepared Pt catalysts on CA-treated ZSM-22 zeolites exhibited enhanced catalytic activity in n-dodecane hydroisomerization, compared to the original ZSM-22 zeolite supported Pt catalyst (89.7% vs. 19.6%) under the same reaction conditions. This was mainly due to the increased Bronsted (B) sites on the treated ZSM-22 zeolites, accelerating the skeletal rearrangement rate. Moreover, Pt/ZSM-22-CA-2 and Pt/ZSM-22-CA-3 exhibited the maximal, similar catalytic activity and yield, but different distribution for C-12-isomers. This phenomenon can be explained by the different ratios between accessible Pt sites and B acidic sites (C-Pt/C-H(+)), and a higher C-Pt/C-H(+) for Pt/ZSM-22-CA-3 (0.36) than Pt/ZSM-22-CA-2 (0.30) meant that the probability of iso-alkene intermediates for hydrogenation saturation on the Pt sites was increased before diffusing to the next B acid, inhibiting the further isomerization and cracking.
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