The effect of barium-promoted for microsphere Ru/CeO₂ catalysts in ammonia synthesis

ABSTRACT

In this essay, the effect of the morphology of the CeO₂ support and the Ba promoter on the ammonia synthesis reaction was studied. CeO₂ support with {110} and {100} crystal planes and more oxygen vacancies enhanced the catalytic activity of ammonia synthesis. The relatively uniform microspheres structure CeO₂ support (CeO₂-MS) with {110} and {100} crystal planes was synthesized. The structural functions of the as-synthesized CeO₂ support for the Ru-based catalyst were investigated in the ammonia synthesis reaction. The results of catalytic performance showed that the catalytic activity of 2.5%Ru/CeO₂-MS catalyst reached 8940 μmol· g⁻¹· h⁻¹ at 450 ℃, 3.8 MPa, H₂/N₂ = 3 (60 mL∙min⁻¹), which is higher nearly 2.5 times than the 2.5%Ru/CeO₂-commercial (CeO₂-C). And the catalytic activity of catalysts increased with the increase of reaction temperature. The activity of 6%Ba-2.5%Ru/CeO₂-MS (24000 μmol· g⁻¹· h⁻¹) catalyst increased about 268% than that of catalyst without addition of Ba. Their physical and chemical properties were characterized by XRD, BET, HRTEM, H₂-TPR, H₂-TPD, and XPS analyses. Our results indicate that the 2.5%Ru/CeO₂-MS catalyst and catalysts involving promoters (Cs, K, and Ba) exhibit significant support-morphology-dependent catalytic activity for ammonia synthesis.

KEYWORDS:

• Ammonia synthesis
• catalytic performance
• cerium oxide morphology
• promoter
• Ru-based catalyst

Supplementary Material

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Additional information

Funding

The authors acknowledge the financial support of the Natural Science Foundation of China (Grant No. 21671147), Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi, State Key Laboratory of Coal and CBM Co-mining (Grant Nos. 2016012004).