Abstract
Chromium oxide supported on mesoporous organo-silica (MOS) was synthesized with different Cr loading by an incipient method. The catalytic performance of a Cr(x)/MOS catalyst for CO2-based ethane dehydrogenation was investigated. The synthesized catalysts were characterized by XRD, BET, TEM, SEM, XPS, FTIR, and UV–Vis DR measurements. The textural properties of the prepared samples showed that the mesoporous nature of MOS sample was not disturbed by chromium impregnation. Among the prepared samples, Cr(8)/MOS catalyst exhibited good distribution of chromium species along with superior concentration of Cr6+ and the highest recorded Cr6+/Cr3+ ratio. The results revealed that the superior catalytic performance was reached at Cr(8)/MOS, with 50.4% and 90.1% of ethane conversion and ethylene selectivity, respectively. The catalytic activity decreased slowly over reaction time; it declined approximately 22% after 10 h of stream operation. The roles of CO2-based ethane dehydrogenation were also studied, where carbon dioxide can be a source of lattice oxygen and as a hydrogen consumer in reverse water–gas shift (RWGS) reaction. The effect of various catalytic factors, such as catalytic temperature, reaction time, space gas velocity, and CO2 partial pressure on the conversion of ethane, yield, and selectivity to ethylene, were investigated as well.
Highlights
Ethane to ethylene-based oxidative dehydrogenation (ODH) by implementing carbon dioxide as an oxidant has received much attention as a replacement to conventional thermal cracking processes and is a path for carbon dioxide utilization [1,2,3,4,5,6]
Type H1 hysteresis is associated with porous materials exhibiting pore geometry of cylindrical shape, along with pore size uniformity which is distinguished for all synthesized samples (Figure 1A)
CO2-based ethane oxidative dehydrogenation was studied over supported chromium oxide on mesoporous organo-silica (MOS)
Summary
Ethane to ethylene-based oxidative dehydrogenation (ODH) by implementing carbon dioxide as an oxidant has received much attention as a replacement to conventional thermal cracking processes and is a path for carbon dioxide utilization [1,2,3,4,5,6]. Among all investigated catalytic systems, chromium oxide supported over silica catalysts exhibits attractive catalytic performances for ODH of ethane with CO2. MCM14-supported chromium oxide, for instance, has been extensively investigated in the dehydrogenation of alkanes, and it exhibited a high Cr dispersion which was reflected positively on their catalytic performance [12,13,16]. The consistent distribution of silicon and organic atoms in the organo-silica precursors is retained in the MOS matrix, so that each individual organic group is covalently bonded to two or more silicon atoms These bridging organic functionalities are uniformly arranged into internal pore wall as well as their outer surface, which provides them thermal and mechanical stability. The catalyst behavior in the presence and absence of CO2, and the effect of CO2 partial pressure, were investigated
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