Tang Haodong, Dang Mingming, Li Yuzhen, Li Lichun, Han Wenfeng, Liu Zongjian, Li Ying, Li Xiaonian
Institute of Industrial Catalysis, Zhejiang University of Technology Hangzhou 310014 PR China
College of Chemical Engineering, Zhejiang University of Technology Hangzhou 310014 PR China.
RSC Adv. 2019 Jul 30;9(41):23744-23751. doi: 10.1039/c9ra04250d. eCollection 2019 Jul 29.
In this study, three different approaches, the sol-gel method, precipitation method and hard-template method, were applied to synthesize MgF catalysts with improved stability towards the dehydrofluorination of hydrofluorocarbons (HFCs); the XRD technique was employed to investigate the relationship between the calcination temperature and the crystallite size of precursors to determine optimal calcination temperature for the preparation of the MgF catalysts. Moreover, the physicochemical properties of MgF catalysts were examined BET, XRD, EDS and TPD of NH and compared. Undoubtedly, the application of different methods had a significant influence on the surface properties and catalytic performances of MgF catalysts. The surface areas of the catalysts prepared by the precipitation method, sol-gel method and template method were 120, 215 and 304 m g, respectively, upon calcination at 200 °C. However, the surface area of the MgF catalysts decreased significantly when the calcination temperatures of 300 and 350 °C were applied. The catalytic performance of these catalysts was evaluated the dehydrofluorination of 1,1-difluoroethane (HFC-152a). The MgF catalyst prepared by the precipitation method showed the lowest catalytic activity among all the MgF catalysts. When the calcination temperature was above 300 °C, the MgF catalysts prepared the template method demonstrated the highest catalytic conversion rate with catalytic activity following the order: MgF-T (template method) > MgF-S (sol-gel method) > MgF-P (precipitation method). The conversion rate generally agreed with the total amount of acid on the surface of the catalysts, which was measured by the NH-TPD technique. The MgF-T catalysts were further examined for the dehydrofluorination of HFC-152a for 600 hours, and a conversion rate greater than 45% was maintained, demonstrating superior long-term stability of these catalysts.
在本研究中，采用了三种不同的方法，即溶胶-凝胶法、沉淀法和硬模板法，来合成对氢氟烃（HFCs）脱氢氟化具有更高稳定性的MgF催化剂；采用XRD技术研究煅烧温度与前驱体微晶尺寸之间的关系，以确定制备MgF催化剂的最佳煅烧温度。此外，对MgF催化剂的物理化学性质进行了BET、XRD、EDS和NH₃-TPD表征并进行了比较。毫无疑问，不同方法的应用对MgF催化剂的表面性质和催化性能有显著影响。在200℃煅烧时，通过沉淀法、溶胶-凝胶法和模板法制备的催化剂的表面积分别为120、215和304 m²/g。然而，当煅烧温度为300℃和350℃时，MgF催化剂的表面积显著下降。通过1,1-二氟乙烷（HFC-152a）的脱氢氟化反应评估了这些催化剂的催化性能。在所有MgF催化剂中，沉淀法制备的MgF催化剂表现出最低的催化活性。当煅烧温度高于300℃时，模板法制备的MgF催化剂表现出最高的催化转化率，催化活性顺序为：MgF-T（模板法）>MgF-S（溶胶-凝胶法）>MgF-P（沉淀法）。转化率一般与通过NH₃-TPD技术测定的催化剂表面酸总量一致。对MgF-T催化剂进行了600小时的HFC-152a脱氢氟化反应进一步考察，保持了大于45%的转化率，表明这些催化剂具有优异的长期稳定性。
