A selective
and stable alumina-supported In-promoted Fe catalyst
(10 mol % In based on Fe) was discovered for converting syngas (2:1
H2/CO ratio) to olefins with high selectivity (45% with
CO2 included) and a remarkable stability (72 h run) at
a CO conversion of 10% at 400 °C and 5 bar. The X-ray photoelectron
spectroscopy results indicated that incorporating In into Fe catalysts
changed the chemical bonding state of Fe and Fe/In composition near
the surface layers, which affected the catalytic reactivity. Steady-state
isotopic transient kinetic analysis showed that more stable CHx fragments
are present on the catalyst surface when incorporating In into Fe,
which can promote C–C coupling reaction toward olefins. Our
study demonstrates that introducing In into Fe catalysts on Al2O3 support can lower CO activation abilities. It
has more impacts on lowering hydrogenation activity, which permits
more C–C couplings and like of “ene” hydrogenation.
Moreover, weakening CO adsorption both in terms of sites and strength
encouraged CO toward hydrocarbons rather than CO2.
A helical metal-organic framework was prepared by using a conformationally rigid tetratopic benzoic acid ligand with binding units pointing toward each other (concave ligand). To avoid the obvious intramolecular interactions between binding units, matching spacing groups were applied to introduce atropic repulsion, thereby allowing the formation of extended frameworks for the first time. With this new ligand design, a helical-shaped MOF with significantly improved air and moisture stability was successfully prepared, thus providing a new strategy for ligand design toward porous material constructions.
Active areas of research on chemical looping technologies for the conversion of CO2 to CO are contrasted and discussed, including current performance, methods for material design, and next steps in expanding their development. Generation of CO from CO2 is of interest in sustainable chemistry and engineering to convert anthropogenic CO2 emissions into feedstock for Fischer–Tropsch (FT), methanol to gasoline (MTG), gas-to-liquid (GTL), and other synthesis pathways for fuels and materials. Chemical looping strategies have been identified which not only produce CO, but also H2 from H2O and methane sources, supplying the other key component of syngas. Configurations of these chemical looping technologies into the materials economy potentially constitute sustainable carbon loop cycles for fuels as well as carbon sequestration into industrial and commercial materials. Major areas of research in CO2 conversion by chemical looping, collectively referred to here as CO2CL, including Solar-Thermal Chemical Looping (STCL), Reverse Water Gas Shift Chemical Looping (RWGS-CL), Chemical Looping Reforming (CLR), Super Dry Reforming (SDR), Autothermal Catalyst Assisted Chemical Looping (ACACL), and Reverse Boudouard Reforming (RBR) are discussed in terms of their process characteristics, historical development of oxygen carrier (OC) material, state of the art methods for material design, and future work needed to advance the scale-up of these technologies. This perspective centers around the non-methane utilizing processes for CO2CL, focusing on the phenomena of oxygen transfer between gas molecules and the oxygen carrier (OC).
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