NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study

Abstract

The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca(2+). Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for (43)Ca, (13)C, and (17)O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

Structural and mechanical characterization of polyurethane-CaCO3 composites synthesized at high calcium carbonate loading: An experimental and theoretical study

“…This structure is in excellent agreement with previous theoretical calculations 38,46 and experimental results found in the literature. 47 The pure PU sample did not show any peak which could indicate impurities.…”

“…The Quantum-Espresso package was used to perform the calculations. 45 The CaCO 3 atomistic model was constructed based on the literature, 38,46 where the most stable (10-14) calcite surface was used as a slab model, employing a total of three CaCO 3 monolayers, one of which was fixed in the crystal position. In view of the interactions for the PU-CaCO 3 , the urethane molecule was used as a model for the molecule-surface interaction.…”

Multiscale Molecular Modeling Applied to the Upstream Oil & Gas Industry Challenges

“…In the Oil & Gas industry, such a feature could lead to a more detailed characterization of the interaction between oil hydrocarbon molecules and mineral surfaces. The high sensitivity of this technique allowed the distinction of the molecule adsorbed over a given calcite surface site (Bevilaqua et al 2014). Complementary, the DFT-NMR information revealed the nature of chemical interactions of organic molecules with mineral surfaces (Bevilaqua et al 2014).…”

First-Principles Calculation of Adsorption of Shale Gas on CaCO3 (100) Surfaces

“…The development from conventional oil and gas fields to shale gas fields actually reflects the scale transition from At the same time, the first-principles method is used to study the adsorption of gas molecules on material surface (17)(18)(19)(20)(21)(22)(23)(24)(25)(26), but there are few reports about the adsorption of gas molecules on the surface of calcium carbonate. Based on density functional theory with solid-state nuclear magnetic resonance (SS-NMR) calculations, Bevilaqua et al (27) simulated the adsorption of hydrocarbon molecules on calcite surface (CaCO 3 (10Ī4)), but the adsorption of shale gas was not studied. In this paper, we adopted the first-principles method based on density functional theory (DFT) to study the adsorption stability of shale gas and its components at different high-symmetry positions on CaCO 3 (100) surfaces.…”