Hydrogen Production of Clean Energy by Partial Oxidation of Methane over M(1)-Ni(5)/SBA-15 (M = Tb, Pr, Eu, and Dy) Catalysts

Abstract

Objectives : In order to solve the environmental problem that is the cause of the global greenhouse effect, We want to evaluate the effects of 1wt% of lanthanum (Tb, Pr, Eu, and Dy) as a promoter added to Ni(5)/SBA-15 catalyst by performing the partial oxidation of methane, the main component of natural gas, to hydrogen over M(1)-Ni(5)/SBA-15 (M = Tb, Pr, Eu and Dy) catalyst and to identify the active site of the catalyst by means of instrumentation such as XPS, FETEM, and EDS.Methods : The catalytic activities of the partial oxidation of methane (POM) to hydrogen as a clean energy over M(1)-Ni(5)/SBA-15 (M = Tb, Pr, Eu, and Dy) catalysts are investigated using a fixed bed flow reactor under atmospheric pressure. The active sites of the catalyst are verified through instrumental analysis with XPS, FETEM, and EDS.Results and Discussion : The XPS results show that when 1wt% of Eu is added to the Ni(5)/SBA-15 catalyst, the atomic percent of Ni2p3/2 is increased from 0.12% to 0.15%, and the oxygen atomic number including lattice oxygen and oxygen vacancies is increased 1.32 times compared to that of the Ni(5)/SBA-15 catalyst. Further, the O1s characteristic peak is chemically shifted toward the lower binding energy. The FETEM images show that the nanoparticles of Ni and Eu are uniformly distributed on the surface of a reduced Eu(1)-Ni(5)/SBA-15 catalyst. The EDS mappings of Eu, Ni, O, and Si are confirmed. It is believed that the activity of the catalyst was improved by increasing the dispersion of nanoparticles of Ni0 on the surface of the catalyst due to the increased mobility of oxygen by creating oxygen vacancies. Methane conversion of Ni(5)/SBA-15 catalyst was deactivated rapidly after the reaction time of 12h whereas M(1)-Ni(5)/SBA-15 (M = Tb, Pr, Eu, and Dy) catalyst showed constant and stable catalyst activity until 12h ~ 50h. It is also considered to be the case that the sintering of Ni particles is prevented by the strong metal support interaction (SMSI) effect between Eu3+, Ni2+, and the SBA-15 carrier, and the stability of the catalyst is thereby maintained. The hydrogen yield of catalyst was in the order of Eu(1)-Ni(5)/SBA-15(57.2%, 25h) >> Dy(1)-Ni(5)/SBA-15 (49%, 14h) > Pr(1)-Ni(5)/SBA-15 (43.1%, 29h) > Tb(1)-Ni(5)/SBA-15 (42.8%, 25h).Conclusion : The Ni(5)/SBA-15 catalyst was showed that the conversion of methane was rapidly reduced after a reaction time of 12h, while when 1wt% of lanthanum (Tb, Pr, Eu and Dy) as a promoter was added to the Ni(5)/SBA-15 catalyst, the conversion of methane and yields of hydrogen were showed constant and stable catalytic activity in the reaction time of 12h to 50h. It is believed that the conversion of methane was improved by increasing the dispersion of nanoparticles of Ni0 on the surface of the catalyst due to the increased mobility of oxygen by creating oxygen vacancies. Moreover, sintering of Ni0 nanoparticles on the surface of M(1)-Ni(5)/SBA-15 (M = Tb, Pr, Eu, Dy) catalyst is prevented by strong metal support interaction (SMSI) effect.