Enhancing the Atomic-Level Understanding of Co2 Mineral Sequestration Mechanisms via Advanced Computational Modeling

Abstract

Fossil fuels currently provide 85% of the world's energy needs, with the majority coming from coal, due to its low cost, wide availability, and high energy content. The extensive use of coal-fired power assumes that the resulting CO 2 emissions can be vented to the atmosphere. However, exponentially increasing atmospheric CO 2 levels have brought this assumption under critical review. Over the last decade, this discussion has evolved from whether exponentially increasing anthropogenic CO 2 emissions will adversely affect the global environment, to the timing and magnitude of their impact. A variety of sequestration technologies are being explored to mitigate CO 2 emissions. These technologies must be both environmentally benign and economically viable. Mineral carbonation is an attractive candidate technology as it disposes of CO 2 as geologically stable, environmentally benign mineral carbonates, clearly satisfying the first criteria. The primary challenge for mineral carbonation is cost-competitive process development. CO 2 mineral sequestration − the conversion of stationary-source CO 2 emissions into mineral carbonates (e.g., magnesium and calcium carbonate, MgCO 3 and CaCO 3 ) − has recently emerged as one of the most promising sequestration options, providing permanent CO 2 disposal, rather than storage. In this approach a magnesium-bearing feedstock mineral (typically serpentine or olivine; available in vast quantities globally) is specially processed and allowed to react with CO 2 under controlled conditions. This produces a mineral carbonate which (i) is environmentally benign, (ii) already exists in nature in quantities far exceeding those that could result from carbonating the world's known fossil fuel reserves, and (iii) is stable on a geological time scale. Minimizing the process cost via optimization of the reaction rate and degree of completion is the remaining challenge.As members of the DOE/NETL managed National Mineral Sequestration Working Group we have already significantly improved our understanding of mineral carbonation. Group members at the Albany Research Center have recently shown that carbonation of olivine and serpentine, which naturally occurs over geological time (i.e., 100,000s of years), can be accelerated to near completion in hours. Further process refinement will require a synergetic science/engineering approach that emphasizes simultaneous investigation of both thermodynamic processes and the detailed microscopic, atomic-level mechanisms that govern carbonation kinetics.Our previously funded Phase I Innovative Concepts project demonstrated the value of advanced quantum-mechanical modeling as a complementary tool in bridging important gaps in our understanding of the atomic/molecular structure and reaction mechanisms that govern CO 2 mineral sequestration reaction processes for the model Mg-rich lamellar hydroxide feedstock material Mg(OH) 2 . In the present simulation project, improved techniques and more efficient computational schemes have allowed us to expand and au...

Electron gas-density functional calculations of the repulsive potentials between noble gas atoms and noble metal surfaces

“…There are only two theoretical values for He-Cu. Lenarcic-Poljanec et al [16] obtained a value of z b = 1.697 from SCF-HF calculations while Chizmeshya estimated z b % 2 [42].…”

Enhancing serpentine dissolution kinetics for mineral carbon dioxide sequestration

“…Aqueous carbonation of mineral silicates involves two steps: Dissolution of cations from the silicate minerals into solution followed by nucleation and growth of carbonate precipitate (Huijgen et al, 2006;Chizmeshya et al, 2003;Teir et al, 2007;Guthrie et al, 2001;Jarvis et al, 2009). Eqs.…”

Insights into the direct carbonation of activated lizardite: The identification a poorly reactive amorphous Mg-rich silicate phase

“…The identified peak at 1073.55 ± 3.95 cm -1 (formed upon carbonation and different from the unactivated lizardite, Figure 1b) might suggest the formation of phases containing siloxane groups (Benhelal et al, 2019b) or amorphous silica (Tran et al, 2013). This is consistent with the formation of a passivating Si-rich phase (Chizmeshya et al, 2006;Hellmann et al, 1990;Lafay et al, 2014), Numerous studies have reported that such phases play an important role in the passivation of the carbonation reaction (Béarat et al, 2006;Julcour et al, 2015). A fraction of Mg can also be stored in this Si-rich phase reducing the available Mg fraction to form carbonates (Benhelal et al, 2019b).…”

“…Analogously, the unreacted 1019 ± 8.5 cm -1 FTIR peak might also be associated with the poorly-reactive amorphous phase (PRAS) responsible for the 673 ± 1.1 cm -1 Raman peak. Moreover, the 888.1 cm -1 FTIR band associated with the reactive amorphous phase observed during this study might also not contain a silanol group (Benhelal et al, 2019b), as this functional group (as well as siloxane and Si-O-Al 2+ /Na 2+ /Mg 2+ groups) is associated with the formation of a Si-rich passivating layer (Casey et al, 1988;Chizmeshya et al, 2006;Hellmann et al, 1990;Lafay et al, 2014), since it is inconsistent with the highly-reactive nature of this intermediate and probably amorphous Mg-rich silicate phase.…”