Inorganic Chemicals Industry ›› 2021, Vol. 53 ›› Issue (6): 205-211.doi: 10.19964/j.issn.1006-4990.2020-0647

• Catalytic Materials • Previous Articles    

Effect of citric acid assisted hydrothermal dealumination on performance of Pt/Beta catalysts for selective ring opening of polycyclic aromatic hydrocarbons

Zang Jiazhong1,2(),Ma Mingchao1,2(),Yu Haibin1,2,Fan Jingxin1,2,Guo Chunlei1,2,Jin Fengying1,2   

  1. 1. CenerTech Tianjin Chemical Research and Design Institute Ltd.,Co.,Tianjin 300131,China
    2. Tianjin Refining and Catalytic Technology Engineering Center
  • Received:2020-12-15 Online:2021-06-10 Published:2021-07-08
  • Contact: Ma Mingchao E-mail:zangjiazhong@163.com;mamingchao0829@163.com

Abstract:

Beta zeolites were post modified by hydrothermal treatment,citric acid treatment and duplex treatment,and the Pt/beta catalyst was prepared with the modified support.The physicochemical properties of the the modified and unmodified beta zeolites were characterized by X-ray diffraction(XRD),X-ray fluorescence spectrometry(XRF),temperature programmed desorption(NH3-TPD),infrared pyridine adsorption(Py-IR),framework aluminum nuclear magnetic resonance(27Al MAS NMR) and framework silicon nuclear magnetic resonance(29Si MAS NMR),and the performance of the modified and unmod-ified Pt/beta on selective ring opening of polycyclic aromatic were investigated.The results showed that dealumination and re-alumination of Beta zeolite performed in citric acid treatment,leading to framework Al redistribution.In the process of hydro-thermal treatment,beta zeolite preferentially removed the framework aluminum at Si(2Al),which had relatively low stability,and produced framework defects and a certain proportion of secondary mesoporous structure.The hydrothermal-citric acid du-plex treatment made a difference to framework aluminum addition and redistribution of beta zeolite.After hydrothermal treat-ment,there were more framework defects in beta molecular sieves,which could promote the framework supplement of active Al(OH)2+ species.When the hydrothermal-citric acid duplex treatment sequence was used for beta zeolite,the effect of frame-work aluminum supplement and framework aluminum redistribution was significant.The sample was mainly medium strong acid with a high ratio of B acid content to L acid content.The as-prepared catalyst had the best selective ring opening activity and stability for polycyclic aromatic hydrocarbons.

Key words: beta zeolite, citric acid treatment, hydrothermal treatment, polycyclic aromatic hydrocarbons, selective ring opening

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