Integration of carbon dioxide capture from flue gas with dry reforming of CH 4 represents an attractive approach for CO 2 utilization. The selection of a suitable bifunctional material serving as a catalyst/sorbent is the key. This paper reports Ni decorated and CeO x -stabilized SrO (SrCe 0.5 Ni 0.5 ) as a multi-functional, phase transition catalytic sorbent material. The effect of CeO x on the morphology, structure, decarbonation reactivity, and cycling stability of the catalytic sorbent was determined with TEM-EDX, XRD, in situ XRD, CH 4 -TPR and TGA. Cyclic process tests were conducted in a packed bed reactor. The results indicate that large Ni clusters were present on the surface of the SrNi sorbent, and the addition of CeO 2 promoted even distribution of Ni on the surface. Moreover, the Ce–Sr interaction promoted a complex carbonation/decarbonation phase-transition, i.e. SrCO 3 + CeO 2 ↔ Sr 2 CeO 4 + CO 2 as opposed to the conventional, simple carbonation/decarbonation cycles ( e.g. SrCO 3 ↔ SrO + CO 2 ). This double replacement crystalline phase transition mechanism not only adjusts the carbonation/calcination thermodynamics to facilitate SrCO 3 decomposition at relatively low temperatures but also inhibits sorbent sintering. As a result, excellent activity and stability were observed with up to 91% CH 4 conversion, >72% CO 2 capture efficiency and ∼100% residual O 2 capture efficiency from flue gas by utilizing the CeO 2 ↔ Ce 2 O 3 redox transition. This renders an intensified process with zero coke deposition. Moreover, the SLDRM with SrCe 0.5 Ni 0.5 has the flexibility to produce concentrated CO via CO 2 -splitting while co-producing a syngas with tunable H 2 /CO ratios.
more »
« less
Modified Ceria for “Low‐Temperature” CO 2 Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat
Efficient CO2utilization is key to limit global climate change. Carbon monoxide, which is a crucial feedstock for chemical synthesis, can be produced by splitting CO2. However, existing thermochemical routes are energy intensive requiring high operating temperatures. A hybrid redox process (HRP) involving CO2‐to‐CO conversion using a lattice oxygen‐deprived redox catalyst at relatively low temperatures (<700 °C) is reported. The lattice oxygen of the redox catalyst, restored during CO2‐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 CO2. To enable the low temperature operation, lanthanum modified ceria (1:1 Ce:La) promoted by rhodium (0.5 wt%) is reported as an effective redox catalyst. Near‐complete CO2conversion with a syngas yield of up to 83% at low temperatures is achieved using Rh‐promoted LaCeO4−
- NSF-PAR ID:
- 10459686
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 9
- Issue:
- 41
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The current study reports AxA’1-xByB’1-yO3-𝛿 perovskite redox catalysts (RCs) for CO2-splitting and methane partial oxidation (POx) in a cyclic redox scheme. Strontium (Sr) and iron (Fe) were chosen as A and B site elements with A’ being lanthanum (La), samarium (Sm) or yttrium (Y), and B’ being manganese (Mn), or titanium (Ti) to tailor their equilibrium oxygen partial pressures (P_(O_2 ) s) for CO2-splitting and methane partial oxidation. DFT calculations were performed for predictive optimization of the oxide materials whereas experimental investigation confirmed the DFT predicted redox performance. The redox kinetics of the RCs improved significantly by 1 wt.% ruthenium (Ru) impregnation without affecting their redox thermodynamics. Ru impregnated LaFe0.375Mn0.625O3 (A=0, A’=La, B=Fe, and B’=Mn) was the most promising RC in terms of its superior redox performance (CH4/CO2 conversion >90% and CO selectivity~ 95%) at 800oC. Long-term redox testing over Ru impregnated LaFe0.375Mn0.625O3 indicated stable performance during the first 30 cycles following with a ~25% decrease in the activity during the last 70 cycles. Air treatment was effective to reactivate the redox catalyst. Detailed characterizations revealed the underlying mechanism for redox catalyst deactivation and reactivation. This study not only validated a DFT guided mixed oxide design strategy for CO2 utilization but also provides potentially effective approaches to enhance redox kinetics as well as long-term redox catalyst performance.more » « less
-
Thermochemical splitting of carbon dioxide to carbon-containing fuels or value-added chemicals is a promising method to reduce greenhouse effects. In this study, we propose a novel process for synchronous promotion of chemical looping-based CO 2 splitting with biomass cascade utilization. The superiority of the process is reflected in (1) a biomass fast pyrolysis process is carried out for syngas, phenolic-rich bio-oil, and biochar co-production with oxygen carrier reduction; (2) the reduced oxygen carrier and the biomass-derived biochar were both applied for CO 2 splitting during the oxygen carrier oxidation stage with carbon monoxide production as well as oxygen carrier re-oxidation; (3) the redox looping of the oxygen carrier was found to synchronously promote the comprehensive utilization of biomass and CO 2 splitting to CO. Various characterizations e.g. HRTEM- and SEM-EDX mapping, H 2 -TPR, CO 2 -TPO, XRD, XPS, N 2 nitrogen adsorption and desorption isotherm tests, Mössbauer, etc. were employed to elucidate the aerogels' microstructures, phase compositions, redox activity, and cyclic stability. Results indicate that the Ca 2 Fe 2 O 5 aerogel is a promising initiator of the proposed chemical looping process from the perspectives of biomass utilization efficiency, redox activity, and cyclic durability.more » « less
-
more » « less
Abstract Sorption-enhanced steam reforming (SESR) of toluene (SESRT) using catalytic CO2sorbents is a promising route to convert the aromatic tar byproducts formed in lignocellulosic biomass gasification into hydrogen (H2) or H2-rich syngas. Commonly used sorbents such as CaO are effective in capturing CO2initially but are prone to lose their sorption capacity over repeated cycles due to sintering at high temperatures. Herein, we present a demonstration of SESRT using A- and B-site doped Sr1−
x A’x Fe1−y B’y O3−δ (A’ = Ba, Ca; B’ = Co) perovskites in a chemical looping scheme. We found that surface impregnation of 5–10 mol% Ni on the perovskite was effective in improving toluene conversion. However, upon cycling, the impregnated Ni tends to migrate into the bulk and lose activity. This prompted the adoption of a dual bed configuration using a pre-bed of NiO/γ –Al2O3catalyst upstream of the sorbent. A comparison is made between isothermal operation and a more traditional temperature-swing mode, where for the latter, an average sorption capacity of ∼38% was witnessed over five SESR cycles with H2-rich product syngas evidenced by a ratio of H2: COx > 4.0. XRD analysis of fresh and cycled samples of Sr0.25Ba0.75Fe0.375Co0.625O3-δ reveal that this material is an effective phase transition sorbent—capable of cyclically capturing and releasing CO2without irreversible phase changes occurring. -
null (Ed.)Chemical Looping Reaction is a key strategy to achieve both emission reduction and carbon utilization while producing various value-added chemicals, through redox reactions. Here we study the effect of nanoshape ceria supported Ru catalysts for plasma assisted Chemical Looping Reforming reduction step coupled with water splitting oxidation step reactions in the temperature range 150 ⁰C to 400 ⁰C at 1 atm pressure. The oxygen carrier/catalyst combination materials used are Ru/CeO2 nanorods (NR), Ru/CeO2 nanocubes (NC), Ru/SiO2 nanospheres (NS), and Ni-based perovskite mixed with CeO2. NRs and NCs showed the best catalytic performance followed by Ni-based perovskite and NS. Differences in the selectivity and reactivity for the NRs and NCs were noticed. The NCs showed slightly higher selectivity towards H2 formation during reduction step and lesser carbon deposition. From the analysis of data and literature, it is proposed that the spillover of species such as H adatoms and CHx radicals after activation at Ru sites into the CeO2 supports and lattice O mobility may be slightly faster in the case of NCs. During the oxidation step, the NR and NC materials showed increased H2 production by a factor of more than 4 when compared to Ni based perovskite material.more » « less
