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  1. Reaction Pathways over ZnZrO2-Based Catalysts and Catalytic Sorbents

    Proaño, Laura ; Wielang, Jordan ; Jones, Christopher W. - ACS Catalysis
    Reactive capture and conversion (RCC) is a process intensification approach that integrates CO2 capture and hydrogenation within a single unit, removing the CO2 purification and storage steps of traditional process flow schemes. This alters the catalytic step from a traditional steady-state (SS) flow process to a transient capture and conversion cycle, which could lead to product distributions distinct from those observed in conventional SS experiments. Such differences are investigated in the combined capture and hydrogenation of carbon dioxide to methanol over a ZnZrO2 catalyst and a ZnZrO2 + NaNO3/Mg3AlOx catalytic sorbent (CS) using fixed-bed kinetic measurements, in situ diffuse reflectancemore » infrared Fourier transform spectroscopy (DRIFTS), and steady-state isotopic transient kinetic analysis-DRIFTS (SSITKA-DRIFTS). Under SS conditions, ZnZrO2 produced methanol through sequential hydrogenation of HCOO* and CH3O* intermediates. On the contrary, CO was attributed primarily to CO2 dissociation at oxygen vacancies, as supported by isotopic shifts and measured reaction orders. For the CS, isotopic switching experiments suggested that monodentate carbonate species (CO32−, abbreviated as m-CO32−) act as active intermediates that can be hydrogenated to HCOO* and subsequently to CH3O. Under RCC conditions, in situ DRIFTS and isotopic experiments reveal that m-CO32− species formed during the CO2 capture step follow two competing routes upon H2 exposure: (i) direct hydrogenation to methane on the sorbent domain or (ii) migration of m-CO32− to the ZnZrO2 domain, where they are hydrogenated to methanol through the HCOO pathway. Overall, RCC enables carbonate hydrogenation routes not observed under SS cofeed conditions. Thus, the reaction pathways and rates during RCC can be different from operation under conventional SS conditions, and the product distribution is determined here by competition between carbonate hydrogenation on sorbent sites and migration to ZnZrO2 for methanol synthesis.« less

  2. Carbon Mineralization of Sulfate Wastes Containing Pb: Synchrotron Pb M3-Edge XANES Analysis of Simultaneous Heavy Metal and Carbon Sequestration

    Hu, Jun ; Pincus, Lauren N. ; Wierzbicki, Dominik ; ... - Environmental Science and Technology
    Sulfate wastes are produced in large quantities and contain toxic heavy metals such as lead (Pb), posing environmental risks. Because of favorable solubility differences, these wastes can be repurposed for engineered carbon dioxide (CO2) sequestration. Understanding the fate and mobility of heavy metals during this process is important. This study focuses on Pb and the effect of zinc (Zn) on Pb in carbon mineralization. Synthesized gypsum was treated with a carbonate-rich solution at pH 11.5 to convert the sulfates to carbonates. Aqueous solutions and mineral solids were analyzed. Synchrotron-based micro-X-ray fluorescence and a novel application of Pb M3-edge X-ray absorptionmore » near-edge structure provided detailed insights into Pb distribution and mineral forms. Results showed significant reductions in aqueous Pb and Zn concentrations, indicating effective metal sequestration. Carbon mineralization transformed Pb from soluble anglesite (PbSO4) into insoluble cerussite (PbCO3) and hydrocerussite (Pb3(CO3)2(OH)2). Pb primarily precipitated onto calcium carbonate surfaces through surface-mediated precipitation reactions. While the presence of Zn modified crystallization dynamics, it did not impede Pb sequestration and potentially enhanced surface reactivity, facilitating greater Pb immobilization. These findings highlight carbon mineralization as a sustainable approach to immobilize toxic metals in sulfate wastes while advancing CO2 sequestration efforts.« less

  3. Taking bio-induced precipitation to the field for sustainable geo-energy storage: Experimental and numerical studies of leakage mitigation

    Olorode, Olufemi ; Kolawole, Oladoyin ; Igweonu, Chibuzor ; ... - Journal of Energy Storage
    There is a consensus that geologic hydrogen and CO2 storage as critical geo-energy technologies will play a significant role in meeting the 2050 net-zero global carbon emission target. However, the potential leakage of stored CO2 and hydrogen from the subsurface to shallower rocks or atmosphere through the faults/fractures expected in most subsurface rocks poses significant environmental and safety concerns. We propose reducing the permeability along these faults/fractures to curtail the gas leakage. This work presents the first-of-a-kind development of experimentally validated core-to-field-scale numerical models for studying the application of a biologically induced mineral precipitation (BIMP) technology to mitigate the leakagemore » of the stored CO2 and hydrogen from these subsurface rocks. Further, we proposed a novel approach for estimating the field-scale CO2 and hydrogen gas storage efficiencies of applied BIMP technology for sealing the fractures/faults that serve as the leakage pathways. Relative to the core-scale experiments, our numerical model showed an accuracy of 95 % in the permeability reduction. We quantified CO2 and hydrogen leakage through natural fractures at the field scale and observed a natural fracture permeability reduction of up to 100% after the BIMP treatment for the fractures closest to the horizontal treatment well. Finally, the results after the BIMP treatment indicate an increase in the long-term CO2 storage efficiency from 50% to 77% over 1100 years relative to pre-treatment, while the BIMP treatment increases the efficiency from 65% to 87% for 25-year cyclic storage and production of hydrogen. In conclusion, this work presents the first experimentally validated core-to-field-scale model for the application of BIMP to improve storage efficiency.« less

  4. Mineralization of alkaline waste for CCUS

    Walker, Irene ; Bell, Robert ; Rippy, Kerry - npj Materials Sustainability
    Ex-situ mineralization processes leverage the reaction of alkaline materials with CO2 to form solid carbonate minerals for carbon capture, utilization, and storage. Annually, enough alkaline waste is generated to reduce global CO2 emissions by a significant percentage via mineralization. However, while the reaction is thermodynamically favorable and occurs spontaneously, it is kinetically limited. Thus, a number of techniques have emerged to increase the efficiency of mineralization to achieve a scalable process. In this review, we discuss mineralization of waste streams with significant potential to scale to high levels of CO2 sequestration. Focus is placed on the effect of operating parametersmore » on carbonation kinetics and efficiency, methods, cost, and current scale of technologies.« less

  5. The cost of CO2 transport by truck and rail in the United States

    Myers, Corey ; Li, Wenqin ; Markham, Gregory - International Journal of Greenhouse Gas Control

  6. Integrated Approach to CO2 Capture and Conversion to Cyclic Carbonates under Solvent- and Additive-Free Conditions Utilizing the CO2 Capture Solvent EEMPA

    Kroll, Jared O. ; Kothandaraman, Jotheeswari ; Grubel, Katarzyna ; ... - Energy and Fuels
    An integrated CO2 capture and conversion to materials (IC3 M) implementation utilizing a CO2 capture solvent is an efficient approach to reduce the amount of CO2 in the atmosphere while producing value-added chemicals. In this work, we demonstrate that the advanced water-lean CO2 capture solvent, N-(2-Ethoxyethyl)-3-morpholinopropan-1-amine (EEMPA), can catalyze the cycloaddition reaction between CO2 and propylene oxide to produce the value-added chemical propylene carbonate in an IC3 M fashion. When excess propylene oxide is used relative to EEMPA, yields as high as 75% with 85% selectivity toward propylene carbonate can be achieved under solvent-free conditions without the need of additives/cocatalysts.more » The reaction temperature (120 °C) is comparable to that used in the thermal regeneration of the capture solvent under industrial conditions. Formation of an undesired amino alcohol side product was observed, but it may be reversible or avoidable with continued research despite the unsuccessful initial attempts. Finally, we show that this can be applied to other epoxides for the production of various cyclic carbonates.« less

  7. The hydration, microstructure, and mechanical properties of vaterite calcined clay cement (VC3)

    Li, Yaqiang ; Li, Yue ; Ma, Hongyan ; ... - Cement and Concrete Research
    Limestone (calcite) calcined clay cement (LC3) is a promising low-CO2 binder, but the low activity of calcite cannot compensate the reduction in clinker factor, resulting in low one-day strength and limiting its broad applications. As recent carbon capture and utilization technologies allow scalable production of vaterite, a more reactive CaCO3 polymorph, we overcome the challenge by introducing vaterite calcined clay cement (VC3), inspired by the vaterite-calcite phase change. In the present study, VC3 exhibits higher compressive strengths and faster hydration than LC3. Compared to hydrated LC3, hydrated VC3 exhibits increased amount of hemi- and mono-carboaluminate formation and decreased amount ofmore » strätlingite formation. With gypsum adjustment, the 1-day strength of VC3 is higher than that of pure cement reference. Finally, VC3, a low-CO2 binder, presents great potential as a host of the metastable CaCO3 for carbon storage and utilization and as an enabler of carbon capture at gigaton scales.« less

  8. Wettability variation and its impact on CO2 storage capacity at the Wyoming CarbonSAFE storage hub: An experimental approach

    Yu, Ying ; Farzana, Sumaiya ; Nye, Charles ; ... - Fuel
    Meeting global and national net zero carbon emission targets will require geologic carbon disposal. The U.S. Department of Energy (DOE) has accordingly funded significant research in this area, including the Wyoming CarbonSAFE project at Dry Fork Station (DFS) in Campbell County, Wyoming. This work studied wettability on micro- and macro-scales, CO2 storage potential, and the correlation between the two to support the Wyoming CarbonSAFE project’s subsurface assessment. During the study, a target formation’s wettability was found to affect how much CO2 can be stored in a given formation. Here, in this study, representative rock samples were selected from the targetmore » storage formations— Lakota, Hulett, and Minnelusa—based on the heterogeneity of the lithology, permeability, and porosity of the respective formations. The rock samples are all fine-grained sandstone with variable cementation and bedding structure, including different scales of laminated bedding. The porosity and permeability vary within the range of 9.0–14.3% and 0.1–28.9 mD, respectively. These rock samples were prepared for the micro-scale wettability (contact angle measurement), macro-scale wettability (wettability index derived from unsteady-state flow characterization for the core plugs), and CO2 storage evaluation. The macro-scale experiments suggested that wettability appeared to dominate the CO2 storage potential performance during the drainage process, where less water-wet behavior promoted higher CO2 storage potential. The micro-scale wettability tests showed that the rock samples at the studied reservoir conditions behaved water-wet and became more water-wet as pressure increased. This kind of wettability change discourages further CO2 storage potential yet benefits the CO2 residual trapping as the CO2 injection proceeds for the studied area. The results allow the recommendation of the best reservoir candidate for storage based on wettability that affects CO2 storage. The work presented in this study provides valuable insights into wettability’s effect on the CO2 storage capacity and wettability’s importance when identifying the optimal CO2 storage formation to meet the project’s goals.« less

  9. Anolyte Enhances Catalyst Utilization and Ion Transport Inside a CO2 Electrolyzer Cathode

    Saha, Prantik ; Henckel, Danielle ; Intia, Fry ; ... - Journal of the Electrochemical Society
    Electrochemical CO2 reduction is a promising technology to capture and convert CO2 to valuable chemicals. High Faradaic efficiencies of CO2 reduction products are achieved with zero-gap alkaline CO2 electrolyzers with a supporting electrolyte at the anode (anolyte). Herein, we investigate the effect of anolyte on the electrode properties such as catalyst utilization, ionic accessibility etc. of a CO2 reduction cathode using electrochemical techniques and cell configurations that avoid the complexities related to co-electrolysis. Using 1M KOH as the anolyte and a Cu gas-diffusion-electrode with low Nafion content as the model CO2 reduction electrode, we find that electrode capacitance (proxy formore » electrochemically active surface area) and ionic conductivity inside the cathode increase approximately 4 and 447 times, respectively, in presence of KOH. Liquid anolyte wets the electrode’s pore structure more efficiently than capillary condensation of feed water vapor. The ionomer coverage is very low, and its distribution inside the electrode is highly fragmented. Surface ion conduction mechanisms inside the electrode are orders of magnitude lower than the bulk ion conduction in presence of anolyte. This study shows that when an anolyte (e.g., KOH) is used, catalyst utilization and ionic accessibility inside the electrode increase significantly.« less

  10. Enhancing CO2 Mineralization Rate and Extent of Iron and Steel Slag via Grinding

    Myers, Corey ; Sasagawa, Jun ; Nakagaki, Takao - ISIJ International
    Roughly 10% of the CO2 emissions from iron and steel making are attributable to the direct release of CO2 from the thermal decomposition of carbonates to produce flux, mainly CaO, used for impurity removal. Notably, these direct emissions remain even if carbon-based steelmaking is replaced by hydrogen-based steelmaking. After removing impurities from the molten metal, this flux becomes the solid waste product called ‘slag’, a primarily Ca-silicate material. The transformation of slag back into carbonates is thermodynamically spontaneous with negative ΔG in the ambient environment, meaning that ~10% of the CO2 emissions from iron and steel making could be negatedmore » if equipment and methods were developed to support CO2 mineralization. However, the rate of CO2 mineralization using slag is slowed by several environmental, geometric, and processing factors. We leverage an experimentally verified model of CO2 mineralization to determine how to efficiently accelerate the process. Increasing the crystallinity of slag, increasing the relative humidity, and reducing the grain size of slag particles provide the greatest increase in CO2 mineralization rate at the lowest energy penalty. Increasing the concentration of CO2 and the temperature provide only modest increases in the CO2 mineralization rate while incurring a substantial energy penalty. For steelmaking slags, CO2 mineralization represents low-hanging fruit as the current reuse pathways are low value. For ironmaking slag, replacing the production of amorphous slag for the cement industry with the production of crystalline slag for CO2 mineralization becomes financially preferable when a carbon price/tax exceeds 67.40 USD/t-CO2.« less
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