Ab Initio Study of Dehydroxylation−Carbonation Reaction on Brucite Surface

Abstract

The possibility of forming magnesite from brucite crystallites, in a CO 2 -rich environment, has attracted large interest as a possible industrial procedure to store CO 2 in the form of carbonate minerals. The reaction mechanisms responsible for such processes are, however, not very well-known. In this work we first consider the compatibility of the magnesite and brucite structures, along specific crystallographic directions. In the second part we describe the sequence of events that leads to the formation of a magnesite layer, via the dehydroxylation of brucite and consequent adsorption and diffusion of carbon complexes. To observe these thermally activated events, we employ a method recently developed in our group 1,2 for finding complex reaction pathways and reproducing the related free energy surface. We find that the (11 h00) brucite surface can be dehydroxylated quite easily. The formation of vacancies in the hydroxyl layers might favor the diffusion of OH and protons through the channels between two neighboring (0001) OH planes, which characterize the brucite structure. This mechanism creates the necessary conditions for further dehydroxylation and formation of magnesite layers.

Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

“…Ab initio calculation gave a value of 180 kJ/mol for reaction (2) and values of around 226 kJ/mol for the carbonation reaction (Churakov et al 2004). Because the weight change observed by TG in the same temperature interval as in HT-XRPD experiments is negative, the contribution of reaction (b) to the overall decomposition reaction must be more important than reaction (a) as the carbonation is increasing the weight of the sample.…”

Structure and dynamics of the water films confined between edges of pyrophyllite: A first principle study

“…Although the simulation time is not sufficient to derive the proton diffusion coefficients the insight on the mechanism of surface proton diffusion can still be gained from the single proton transfer events. More accurate results on the proton diffusion kinetics could be obtained using with more advanced techniques like thermodynamic integration (Trout and Parrinello, 1999) or metadynamics (Iannuzzi et al, 2003;Churakov et al, 2004). Such simulations are beyond the scope of this study.…”

“…The "SiAOH groups are structurally similar to those on the surface of amorphous silica (Warne et al, 2000;Masini and Bernasconi, 2001). The amphoteric "AlAOH and "AlAOH 2 sites inherit the properties of simple layered hydroxides (Churakov et al, 2004;Wang et al, 2004) or the octahedral surface of kaolinite (Warne et al, 2000;Tunega et al, 2004). The "AlAOASi" sites are common in zeolites (Chatterjee et al, 1999).…”

Lithium Hydroxide Phase Transition under High Pressure: An Ab Initio Molecular Dynamics Study

“…[34,35] The choice of the PPs, energy cutoff, and exchange-correlation functional is based on their successful application in earlier simulations on similar systems, such as Ca(OH) 2 and Mg(OH) 2 . [36,37] The deuterium isotope was used instead of hydrogen, to compare the simulated structure factors directly with the neutron scattering experiments, [24] and to allow a larger simulation time step ( % 0.12 fs).…”