Dehydrogenation of Ethane to Ethylene by CO2 over Highly Dispersed Cr on Large-Pore Mesoporous Silica Catalysts

Catalysts

SaeedM. Al-Zahrani¹  AhmedE. Abasaeed¹  AbdulrhmanS. Al-Awadi¹  AhmedMohamed El-Toni² 

[1] Chemical Engineering Department, King Saud University, Riyadh 11421, Saudi Arabia;King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi Arabia;

关键词: oxidative dehydrogenation;    chromium-based catalyst;    large-pore mesoporous silica;    ethane;    carbon dioxide;    ethylene;   

DOI  :  10.3390/catal10010097

来源: DOAJ

【 摘 要 】

A series of large-pore mesoporous silica (LPMS)-supported CrO_x catalysts were synthesized by hydrothermal and impregnation methods and tested for ethane dehydrogenation in the presence of CO₂ as an oxidant. To assess the effect of hydrothermal temperature treatment on the characteristics of LPMS support, different hydrothermal temperatures (100−160 °C) were studied and optimized. The optimum support was then loaded with different amounts of chromium (0, 2, 4, 8, and 11 wt % Cr). The obtained catalysts were characterized by different techniques such as XRD, BET, TEM, SEM, XPS, FTIR, and diffuse reflectance UV-Vis spectroscopy. The characterization results indicated that the sample hydrothermally treated at 130 °C exhibited the highest pore volume, a narrow pore size distribution, and a moderate BET surface area. Chromium species with various oxidation states including Cr³⁺, Cr⁶⁺, and α-Cr₂O₃ were detected in all synthesized Cr(y)/LPMS-130 catalysts. A lower Cr content resulted in the formation of Cr⁶⁺, whereas a higher Cr content dominated the α-Cr₂O₃ on the surface of the catalyst. Among the synthesized catalysts, the Cr(4)/LPMS-130 catalyst showed the highest Cr⁶⁺/Cr³⁺ ratio, indicating a good dispersion of chromium species along with a fine particle size. The ethane conversion and ethylene selectivity were 50.5 and 91.1% for Cr(4)/LPMS-130, respectively. Carbon dioxide was believed to supply enough lattice oxygen to maintain the Cr species at a higher oxidation state and to consume the hydrogen resulting from ethane cracking by a reverse water gas shift reaction.

【 授权许可】

Unknown