Modified Ceria for “Low‐Temperature” CO₂Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat

Abstract

Efficient CO 2-utilization is key to limit global climate change. Carbon monoxide, which is a crucial feedstock for chemical synthesis, can be produced by splitting CO 2. However, existing thermochemical routes are energy-intensive requiring high operating temperatures. We report a Hybrid Redox Process (HRP) involving CO 2-to-CO conversion using a lattice oxygen-deprived redox catalyst at relatively low temperatures (<700 °C). The lattice oxygen of the redox catalyst, restored during CO 2-splitting, is subsequently used to convert methane to syngas. Operated at temperatures significantly lower than a number of industrial waste heat sources, this cyclic redox process allows for efficient waste heat-utilization to convert CO 2. To enable the low temperature operation, we report lanthanum modified ceria (1:1 Ce: La) promoted by rhodium (0.5 wt. %) as an effective redox catalyst. Near-complete CO 2 conversion with a syngas yield of up to 83% at low temperatures were achieved using Rh-promoted LaCeO 4-x. While La improves low-temperature bulk redox properties of ceria, Rh considerably enhances the surface catalytic properties for methane-activation. Density Functional Theory calculations further illustrate the underlying functions of La-substitution. The highly effective redox catalyst and HRP scheme provide a potentially attractive route for chemical production using CO 2 , industrial waste heat, and methane, with appreciably lowered CO 2 emissions.

Boosting methane partial oxidation on ceria through exsolution of robust Ru nanoparticles

“…In the second step, the reduced metal oxide is reoxidized with CO 2 , producing CO (Eq.2). Importantly, the first step, which is an endothermic reaction occurring at high temperatures (800-1000 ºC), could be driven with waste 5 or concentrated solar heat [6][7][8] Eq. 1 4 +1/ This 2-step cyclic process presents several operational advantages.…”

“…However, the limited oxygen-exchange capacity of ceria could hamper its further applicability. In order to overcome this problem, doping with other cations, 4 such as Zr 14 or La 5 , has been employed in order to increase the reducibility of cerium oxides and, subsequently, the fuel yields obtained by H 2 O and/or CO 2 splitting. Morphological modifications 15 or combinations in the form of composites with other metal oxides such as perovksites 16 or binary oxides 17,18 have been also successfully tested.…”

Low temperature methane conversion with perovskite-supported exo/endo-particles

“…43 Other studies in the literature have been published with a similar scope of lowering the activation temperature of such processes and that have reported similar performance using noble metals to achieve so. 44 Still the results presented here result from a kinetic study and optimization is potentially needed in order for the above to be applied in an industrial process. In addition, the increase in porosity speeded up oxygen exchange with the gas phase since the methane consumption (similar to the reducing half cycle of a chemical looping process) nishes in 15 min, while it takes an additional 3-4 min more for its lower-porosity counterpart to complete the same task.…”

A tailored multi-functional catalyst for ultra-efficient styrene production under a cyclic redox scheme

“…1a ). Facilitated by the redox catalyst, redox-ODH follows a chemical-looping-based approach, which has been previously reported for CO 2 capture from fossil fuel combustion 20 – 22 , methane-selective oxidation 23 – 29 , thermochemical water/CO 2 splitting 30 – 37 , air separation 38 – 40 , and ODH of light alkanes 41 – 43 . To our knowledge, previous chemical-looping studies have yet to investigate catalytic conversion to hydrocarbon molecules containing more than four carbon atoms, mainly due to the high operating temperature required by conventional redox catalysts and/or lack of product selectivity 44 , 45 .…”