Abstract
In this study, we aimed to enhance the catalytic activity of perovskite catalysts and elucidate their catalytic behavior in the oxidative coupling of methane (OCM), using alkali-added LaAlO3 perovskite catalysts. We prepared LaAlO3_XY (X = Li, Na, K, Y = mol %) catalysts and applied them to the OCM reaction. The results showed that the alkali-added catalysts’ activities were promoted compared to the LaAlO3 catalyst. In this reaction, ethane was first synthesized through the dimerization of methyl radicals, which were produced from the reaction of methane and oxygen vacancy in the perovskite catalysts. The high ethylene selectivity of the alkali-added catalysts originated from their abundance of electrophilic lattice oxygen species, facilitating the selective formation of C2 hydrocarbons from ethane. The high COx (carbon monoxide and carbon dioxide) selectivity of the LaAlO3 catalyst originated from its abundance of nucleophilic lattice oxygen species, favoring the selective production of COx from ethane. We concluded that electrophilic lattice oxygen species play a significant role in producing ethylene. We obtained that alkali-adding could be an effective method for improving the catalytic activity of perovskite catalysts in the OCM reaction.
Highlights
Since the industrial revolution of the late 18th century, total oil consumption has been increasing gradually with the industrial development of developing countries
The LaAlO3 catalyst was prepared in the same method for comparison
It was expected that the catalytic activity could be further enhanced by adding
Summary
Since the industrial revolution of the late 18th century, total oil consumption has been increasing gradually with the industrial development of developing countries. Shale gas has attracted significant attention as an upcoming alternative energy source It has significant reserves in the world, and about 80% to 90% of its components consist of methane (CH4 ). As shale gas is drawing attention as an alternative energy source, the study of converting methane, which is the main component of shale gas, into high value-added compounds is being actively conducted [1,2,3,4,5]. The indirect conversion of CH4 requires additional energy because it needs a multi-step process [6,7,8,9] For this reason, many researchers believe that the direct conversion of CH4 is more efficient in economic terms [10,11,12,13]. Among the direct CH4 conversion methods, the oxidative coupling of methane (OCM) to form C2 hydrocarbons such as ethylene (C2 H4 ) and ethane (C2 H6 )
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