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1. Sorption-enhanced steam reforming of toluene using multifunctional perovskite phase transition sorbents in a chemical looping scheme

   https://doi.org/10.1088/2515-7655/acdbe9  

   Brody, Leo; Rukh, Mahe; Cai, Runxia; Saberi Bosari, Azin; Schomäcker, Reinhard; Li, Fanxing (June 2023, Journal of Physics: Energy)

   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 Sr_1−xA’_xFe_1−yB’_yO_3−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: CO_x> 4.0. XRD analysis of fresh and cycled samples of Sr_0.25Ba_0.75Fe_0.375Co_0.625O_3-δreveal that this material is an effective phase transition sorbent—capable of cyclically capturing and releasing CO₂without irreversible phase changes occurring. 

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2. Solubility of Rock in Steam Atmospheres of Planets

   https://doi.org/10.3847/0004-637X/824/2/103  

   Fegley, Bruce; Jacobson, Nathan S.; Williams, K. B.; Plane, J. M.; Schaefer, L.; Lodders, Katharina (June 2016, Astrophysical journal)

   Extensive experimental studies show that all major rock-forming elements (e.g., Si, Mg, Fe, Ca, Al, Na, K) dissolve in steam to a greater or lesser extent. We use these results to compute chemical equilibrium abundances of rocky-element-bearing gases in steam atmospheres equilibrated with silicate magma oceans. Rocky elements partition into steam atmospheres as volatile hydroxide gases (e.g., Si(OH)4, Mg(OH)2, Fe(OH)2, Ni(OH)2, Al(OH)3, Ca(OH)2, NaOH, KOH) and via reaction with HF and HCl as volatile halide gases (e.g., NaCl, KCl, CaFOH, CaClOH, FAl(OH)2) in much larger amounts than expected from their vapor pressures over volatile-free solid or molten rock at high temperatures expected for steam atmospheres on the early Earth and hot rocky exoplanets. We quantitatively compute the extent of fractional vaporization by defining gas/magma distribution coefficients and show that Earth's subsolar Si/Mg ratio may be due to loss of a primordial steam atmosphere. We conclude that hot rocky exoplanets that are undergoing or have undergone escape of steam-bearing atmospheres may experience fractional vaporization and loss of Si, Mg, Fe, Ni, Al, Ca, Na, and K. This loss can modify their bulk composition, density, heat balance, and interior structure. 

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3. Decarboxylation of stearic acid over Ni/MOR catalysts

   https://doi.org/10.1002/jctb.6211  

   Crawford, James_M; Zaccarine, Sarah_F; Kovach, Nolan_C; Smoljan, Courtney_S; Lucero, Jolie; Trewyn, Brian_G; Pylypenko, Svitlana; Carreon, Moises_A (October 2019, Journal of Chemical Technology & Biotechnology)

   Abstract BACKGROUNDOils derived from plants, animal fats, and algae contain both saturated and unsaturated fatty acids. These fatty acids can be converted into liquid fuels and chemicals in the presence of active solid catalysts. RESULTSNickel‐based catalysts were supported on mordenite via ion exchange synthesis and evaluated for the deoxygenation of stearic acid to diesel fuels. By tuning the synthesis pH, loadings of over 20 wt% Ni were obtained. Catalysts synthesized at pH 8.5 displayed the highest Ni loading and the highest activity for the decarboxylation/decarbonylation of stearic acid under inert nitrogen gas atmospheres, yielding 47% heptadecane. Characterization included scanning transmission electron microscopy‐energy‐dispersive spectroscopy (STEM‐EDS), X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), inductively coupled plasma atomic emission spectroscopy (ICP‐AES), N₂physisorption and thermogravimetric analysis (TGA), providing new insights into the recyclability of the catalyst. The observed loss of catalytic activity upon recycling was attributed to the agglomeration of Ni nanoparticles and the accumulation of carbonaceous coke. CONCLUSIONThis work demonstrates that Ni‐based catalysts supported on mordenite zeolite can effectively convert stearic acid into heptadecane. Yields to heptadecane were as high as 47%. Mechanistically, the reaction proceeds by decarboxylation and decarbonylation pathways. © 2019 Society of Chemical Industry 

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4. Advances in the synthesis, characterisation, and mechanistic understanding of active sites in Fe-zeolites for redox catalysts

   https://doi.org/10.1039/D0DT01857K  

   Bols, Max L.; Rhoda, Hannah M.; Snyder, Benjamin E.; Solomon, Edward I.; Pierloot, Kristine; Schoonheydt, Robert A.; Sels, Bert F. (November 2020, Dalton Transactions)

   null (Ed.)

   The recent research developments on the active sites in Fe-zeolites for redox catalysis are discussed. Building on the characterisation of the α-Fe/α-O active sites in the beta and chabazite zeolites, we demonstrate a bottom-up approach to successfully understand and develop Fe-zeolite catalysts. We use the room temperature benzene to phenol reaction as a relevant example. We then suggest how the spectroscopic identification of other monomeric and dimeric iron sites could be tackled. The challenges in the characterisation of active sites and intermediates in NO X selective catalytic reduction catalysts and further development of catalysts for mild partial methane oxidation are briefly discussed. 

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5. Cr and CeO2 promoted Ni/SBA-15 framework for hydrogen production by steam reforming of glycerol

   Abrokwah, R; Ntow, E; Jennings, T; Stevens_Boyd, R; Hossain, T; Swain, J; Bepari, S; Hassan, S; Mohammad, N; Kuila, D (November 2023, Steel in translation)

   Ni/SBA-15 meso-structured catalysts modified with chromium and CeO2 (Ni–Cr-CeO2/SBA-15) were utilized to produce hydrogen from glycerol steam reforming (GSR). The catalysts were synthesized by a one-pot hydrothermal process and extensively characterized by analytical techniques such as N2 adsorption–desorption (BET), H2-temperature programmed reduction (H2-TPR), powder X-ray diffraction (PXRD), inductively coupled plasma-optical emission spectrometry (ICP-OES), and transmission electron microscopy (TEM). The low-angle XRD reflections affirmed that the catalysts were crystalline and possessed a 2D-ordered porosity. The BET results depicted that all the catalysts exhibited a good surface area ranging from 633 to 792m2/g, and the pore sizes were consistently in the mesoporous range (between 3 and 5 nm). TEM analysis of both calcined and spent catalysts revealed that the metal active sites were embedded in the hybrid CeO2-SiO2 support. Overall, the Ni-based catalysts exhibited higher glycerol conversion -12Ni-SBA-15–99.9%, 12Ni3CeO2-SBA-15–89.4%, and 8Ni4Cr3CeO2-SBA-15–99.7%. Monometallic 12Ni/SBA-15 performed exceptionally well, while 12Cr/SBA-15 performed poorly with the highest 71.48% CO selectivity. For short-term GSR reactions, CeO2 addition to 12Ni/SBA-15 did not have any effect, whereas Cr addition resulted in a 32% decrease in H2 selectivity. The long-term stability studies of 12Ni-SBA-15 showed H2 selectivity of ~ 64% and ~ 98% glycerol conversion. However, its activity was short-lived. After 20–30 h, the H2 selectivity and conversion dropped precipitously to 40%. The doping of mesoporous Ni/SBA-15 with Cr and CeO2 remarkably enhanced the long-term stability of the catalyst for 12Ni3CeO2-SBA-15, and 8Ni4Cr3CeO2-SBA-15 catalyst which showed ~ 58% H2 selectivity and ~ 100% conversion for the entire 60 h. Interestingly, Cr and CeO2 seem to improve the shelf-life of Ni-SBA-15 via different mechanistic pathways. CeO2 mitigated Ni poisoning through coke oxidation whereas Cr bolstered the catalyst stability via maintaining a well-defined pore size, structural rigidity, and integrity of the heterogeneous framework, thereby restricting structural collapse, and hence retard sintering of the Ni active sites during the long-term 60 h of continuous reaction. Hydrogen generation from renewable biomass like glycerol could potentially serve as a sustainable energy source and could substantially help reduce the carbon footprint of the environment 

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