This article is an up-to-date review of the literature available on the subject of ethanol to ethylene. The process of ethanol to ethylene has broad development prospects. Compared with the process of petroleum to ethylene, ethanol dehydration to ethylene is economically feasible. Researchers have been redirecting their interest to the ethylene production process, catalysts, and reaction mechanisms. A fluidized bed reactor, together with a wear-resistant, efficient, and stable catalyst will be the focus of future research that includes a deep understanding of the large-scale activated alumina catalyst and the molecular sieve catalyst used, and will promote the development of the ethanol dehydration to ethylene process and provide strong support for the market competiveness of the process.
Direct production of light olefins from synthesis gas
through the
Fischer–Tropsch to Olefins (FTO) process over iron carbide
catalysts is promising. Several mechanisms have been proposed to explain
the formation of different hydrocarbons on clean surfaces. However,
when these mechanisms were discussed before, the influence of adsorbed
surface species, especially surface H, on the mechanisms is less understood.
Hence, we reported a density functional theory (DFT) study on the
hydrogen coverage effect and the mechanism of the FTO process on Fe5C2 (510). It is found that the Fe5C2 (510) surface may be covered with a layer of H in the FTO
process. The mechanism of the Fischer–Tropsch synthesis on
the Fe5C2 (510) surface prefers to proceed via
the CO insertion mechanism rather than the carbide mechanism in the
presence of adsorbed H. The optimized C–C coupling pathways
feature H-assisted CO coupling pathways in which the CHCHO pathways
(E
a = 1.15 eV) and the CH2CHO
pathways (E
a = 1.10 eV) are favorable.
The methane formation pathway is an alternative major pathway on the
χ-Fe5C2 (510) surface due to its relatively
low barrier energies (E
a = 0.80 eV). The
formation of oxygenates is unfavorable due to the high C–O
dissociation reactivity. The olefin ratio for ethylene and ethane
is influenced by two competitive processes in a stepwise hydrogenation.
It is suggested from the mechanism that high C–C coupling
activity and the matching hydrogenation activity with the former are
the key directions to modify iron-based FTO catalysts.
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