Abstract
Oxidative dehydrogenation of alkanes to alkenes by a mild oxidant such as carbon dioxide is an active area of research. A series of MCM41-supported bimetallic oxide catalysts containing chromium oxide in addition to metal oxides (Ce, Co, Zn, V, Nb, and Mo) has been prepared. The binary catalysts have Cr metal oxide incorporated into MCM41 structure while the other oxides are either incorporated with Cr or impregnated on the MCM41 surface. The synthesized catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 sorption, scanning electron microscopy (SEM), hydrogen temperature programmed reduction (H2-TPR), and Diffuse reflectance UV–vis spectroscopy (DRS). The catalytic activity of Cr(4)-M(4)/MCM-41 catalysts in the dehydrogenation of ethane with CO2 was investigated. The textural properties of the synthesized samples showed that the addition of the bimetallic oxides did not disturb the mesoporous structure of MCM41 and the prepared catalysts exhibited a high BET surface area; however, the lowest surface area was recorded for Cr(4)-Mo(4)/MCM41 catalyst at 701 m2/g. Among the prepared catalysts, H2-TPR profile of Cr(4)-Ce(4)/MCM41 revealed the increase in the concentration of Cr6+ species which interacted with the framework of siliceous support. On the other hand, H2-TPR profiles of Cr(4)-Co(4)/MCM41 showed wide reduction peaks centered at 400 °C which is ascribed to reduction of Cr6+ to Cr3+ species and Co3O4 to metallic Co. At the same time, Cr(4)-Mo(4)/MCM41 and Cr(4)-V(4)/MCM41 exhibited higher temperature reduction peaks, indicating these two catalysts require higher activation temperatures. The synergy between the Cr with Zn or Nb metals reduced the concentration of Cr6+ species which is reflected in their catalytic performance. Cr(4)-Ce(4)/MCM41 recorded the highest catalytic activity toward ethylene production where the ethane conversion and ethylene yield were 37.9% and 35.1%, respectively.
Highlights
Ethylene, a crucial material in the petrochemical industry, is used in the production of versatile intermediate and final products
Ethylene is produced by catalytic cracking and steam cracking of hydrocarbon feedstocks like ethane and naphtha [1,2]
It has been established that using CO2 improves the yield and selectivity of ethylene as well as maintains the catalytic activity by reducing cock formation [10,11]
Summary
A crucial material in the petrochemical industry, is used in the production of versatile intermediate and final products. The cracking processes, Equation (1), have several drawbacks, including high energy requirements because of its endothermicity, severe coke formation, thermodynamic limitation, and inefficient control of ethylene selectivity [3,4,5]. Oxidative dehydrogenation of ethane by oxygen, Equation (2), has been introduced as a good alternative to the thermal cracking process because coke formation is minimized because of the presence of oxygen [6,7]. Over-oxidation of ethane and ethylene to carbon oxides and the probable formation of hot spots are the major issues of this process [8,9]. It has been established that using CO2 improves the yield and selectivity of ethylene as well as maintains the catalytic activity by reducing cock formation [10,11]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
