Redox and Nonredox CO2 Utilization: Dry Reforming of Methane and Catalytic Cyclic Carbonate Formation

S. Subramanian, Y. Song, D. Kim, C. T. Yavuz*
ACS Energy Lett., 5, 5, 1689–1700 (2020). Invited Review
DOI: 10.1021/acsenergylett.0c00406

CO2 emissions are too large to tackle with a single process, but a combination of avoidance with chemical utilization may be able to slow global warming. In this Focus Review, we identify two large-scale CO2 conversion processes based on their viability and opposite energy requirements. In the high-energy, stationary path, CO2 reforming of methane could provide gigatons of CO2 utilization through synthesis gas. The main problem is the lack of a durable, effective, low-cost dry reforming catalyst. The exothermic cyclic carbonate formation from CO2 and organic epoxides offers a low-energy, mobile, nonredox route. The catalysts, however, must be metal-free and robust, have a high surface area, and be low-cost while being easily scalable. These two processes could potentially address at least a quarter of all current CO2 emissions.

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Dry reforming of methane by stable Ni–Mo nanocatalysts on single-crystalline MgO

Y. Song, E. Ozdemir, S. Ramesh, A. Adishev, S. Subramanian, A. Harale, M. Albuali, B. A. Fadhel, A. Jamal, D. Moon, S. H. Choi, C. T. Yavuz*
Science, 367, 6479, 777-781 (2020).
DOI: 10.1126/science.aav2412

Large-scale carbon fixation requires high-volume chemicals production from carbon dioxide. Dry reforming of methane could provide an economically feasible route if coke- and sintering-resistant catalysts were developed. Here, we report a molybdenum-doped nickel nanocatalyst that is stabilized at the edges of a single-crystalline magnesium oxide (MgO) support and show quantitative production of synthesis gas from dry reforming of methane. The catalyst runs more than 850 hours of continuous operation under 60 liters per unit mass of catalyst per hour reactive gas flow with no detectable coking. Synchrotron studies also show no sintering and reveal that during activation, 2.9 nanometers as synthesized crystallites move to combine into stable 17-nanometer grains at the edges of MgO crystals above the Tammann temperature. Our findings enable an industrially and economically viable path for carbon reclamation, and the “Nanocatalysts On Single Crystal Edges” technique could lead to stable catalyst designs for many challenging reactions.

Perspective: Liyu Chen, Qiang Xu*, "Fewer defects, better catalysis?", p. 737
Research summary by Phil Szuromi, "Overcoming surface defects", p. 752-753
Highlighted in Chemistry World, C&EN, Nature Asia
Korean press release, English press release

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Sustainable nanoporous benzoxazole networks as metal-free catalysts for one-pot oxidative self-coupling of amines by air oxygen

S. Subramanian, H. A. Patel, Y. Song, C. T. Yavuz*
Adv. Sustain. Syst., 1, 1700089, (2017).
DOI: 10.1002/adsu.201700089

The development of sustainable organocatalysts with porosity, high stability, and excellent catalytic activity offers a clean and green alternative to precious metal catalysts. Here, an efficient, nanoporous, heterogeneous benzoxazole catalyst is reported for aerobic oxidative coupling of amines. A molecular design strategy is presented to functionalize primary amines to produce valuable products under one-pot, open-air reaction conditions. Unprecedented and previously unknown, the stable imine intermediate catalyzes its own formation, also known as autocatalysis, enabling a direct and favorable access to amino acids, even if the catalysts are absent. The biomimetic benzoxazole catalysts developed here provide quantitative catalytic activity over 50 cycles with favorable kinetics with no degradation. This work also marks the first use of benzoxazoles for oxidative catalytic reactions.

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Monitoring instability of linear amine impregnated UiO-66 by in-situ temperature resolved powder X-ray diffraction

Y. Song, D. Thirion, S. Subramanian, M. S. Lah, C. T. Yavuz*
Micropor. Mesopor. Mater., 243, 85-90, (2017).
DOI: 10.1016/j.micromeso.2017.02.021.

Carbon dioxide capture requires stable porous solids like zirconium based metal-organic frameworks (MOFs) in order to make sequestration efforts feasible. Because of the weak binding at low CO₂ partial pressures, oligomeric amines are commonly loaded on porous supports to maximize CO₂ capture while attempting to keep porosity for enhanced diffusion. Here we show the first temperature resolved stability study of linear-amine impregnated UiO-66 by in-situ monitoring of the PXRD pattern. Our findings show that the crystal structure shows a contraction at temperatures as low as 80 °C and deforms considerably above 120 °C, leading to significant doubts about their applicability in CO₂ capture from lean feeds. We confirm that all MOFs need to be thoroughly analyzed at least by means of PXRD at the process relevant temperatures, and reinforced before any plausible plans of application in CO₂ capture.

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