Research Lines

In the oil sector, a large part of the oil produced is recovered in emulsified form.  The stability of these emulsions makes them an obstacle to the industry. Therefore, the separation of water and oil is essential. Electrocoalescence is an attractive method to perform this separation for economic and environmental reasons. Interfacial systems play a key role in several chemical-related processes, especially for petroleum recovery from deposits. Low interfacial tensions contribute to emulsion formation, which enables a higher efficiency in the recovery process. Surfactants are major components to enable the "mixing" of water and oil, acting as stabilizers for the droplets formed in the continuous phase. Their behavior is essential to develop more efficient techniques and formulations for both emulsion formation and breaking.
In our research, we use a molecular scale model is to provide insight into key properties such as interfacial tension, molecular orientation, micelle, and emulsion formations.  This is done through coarse- grained  molecular simulations using the MARTINI force field, which allows for the study of more complex surfactants and for access to higher time and  length  scales. Barker and Henderson perturbation theory for fluids and van der Waals theory for solids can be used to calculate phase diagrams of water in oil emulsions over influence of an external electric field. Additionally, molecular Thermodynamics associated with energy minimization of water and surfactant systems is  used to predict micelle formation conditions (critical micelle concentration).

Gas hydrates are structures formed by the cooperative hydrogen bonding of water molecules to form cages that encapsulate small molecules. In terms of methane reservoir, these crystalline structures (clathrates) are extremely important because they trap enormous amounts of natural gas on the ocean floor. The amount of carbon in gas hydrates is estimated to be more than twice the amount of carbon in all other fossil fuel deposits. Gas hydrates have also been proposed as potentially useful in novel gas separation processes and in transport of natural gas. In terms of problems, gas hydrates can form in pipelines and, by agglomeration mechanism, can plug subsea pipelines from offshore platforms causing economic loss and potentially unsafe conditions. For the flow assurance in oil and gas industry and in collaboration with Petrobras, our group studies thermodynamic and kinetic aspects related to hydrate formation and hydrate dissociation. Multiphase equilibria and kinetic studies provide thermodynamic, transport, and kinetic data for hydrate decomposition.

Many active ingredients in medicines are chiral molecules. Praz- iquantel (PZQ) racemate has been used to fight against schistosomiasis. In our research, a built-in-house Simulated Moving Bed (SMB) unit is developed concerning the praziquantel separation. The experimental open-loop study is performed with chiral detector equipment coupled to the SMB unit.
We are also working on  the adsorption of fine chemicals (organic  acids-OAc  and Praziquantel-PZQ)  and evaluating the uncertainties propagation by means of Fisherian and Bayesian approaches.  The bayesian Uncertainty modelling for adsorption isotherms. approach  allowed  for conservative  inference over the adsorption parameters and even on experimental variances. The results are valuable for the design and optimization of continuous chromatographic operations as the simulated moving bed.

Prediction of the interaction of complex fluids (e.g. hydrogen-bonding fluids, hydrocarbons, proteins, and polymers) with adsorbing surfaces is essential for the control of many processes of current industrial and scientific interest. In our group, we develop tools in statistical thermodynamics, equations of state, molecular simulations, and density functional theory to predict the thermodynamic properties and structures of components confined near hydrophobic and hydrophilic surfaces. These tools can be useful for solving problems in adsorption, shale gas reservoirs, and other systems with confined fluids.
Classical Density Functional Theory (cDFT) can be applied to characterize new porous materials by examining the pore size distribution (PSD) and obtaining absolute adsorption isotherms from excess isotherm experimental data. NLDFT and QSDFT are already applied in the literature to simulate the adsorption of simple fluids. However, models consistent with PC-SAFT and PCP-SAFT can successfully describe hydrocarbon and CO2 isotherms, even under supercritical conditions. Here, we developed methodologies to apply the cDFT models to obtain adsorption and  desorption  physicalchemical properties for simple fluids, chain-molecules, and species with polarity effect in adsorbent cavities, considering pore walls with and without roughness. In addition, we also developed techniques to optimize cDFT routines to obtain the equilibrium  physical-chemical properties for cases where 3D PC-SAFT-DFT simulation of methane in a there is sorption hysteresis, slit-pore with chemical heterogeneity.  allowing the direct calculation of the equilibrium isotherm and phase diagrams inside the pores.

The laboratory has a recently built infrastructure for natural gas dehydration studies by adsorption, which consists mainly of a pilot unit for natural gas dehydration studies that is unique in the world and a highly accurate adsorption system in controlled environments (pressure, temperature, corrosive gases) known as a Magnetic Suspension Balance (MSB). The pilot unit and the MSB equipment com- plement each other, allowing the laboratory to: (1) carry out studies to characterize the physicochemical prop- erties of adsorbents (textural  properties of adsorbents and isotherms); (2) standardize and calibrate wet streams with high CO2 content and (3) select,  qualify and  study adsorbents, as well as the study of their aging through the use of the pilot plant present in the laboratory, which was designed to be temperature modulated to the removal of water by adsorption in streams with high CO2 content.

The natural gas produced in Brazil has been presenting a high CO2 content, reaching up to 70% composition in some pré-salt reservoirs. The presence of CO2 increases the solubility considerably in terms of water vapor, which under the operating conditions imposed by the production in ultra-deep waters (high pressures) can lead to the for- mation of hydrates and favor the formation of corrosive compounds. Thus, studying and improving the techniques employed to mon- itor natural gas regarding the associated water content is neces- sary, especially at low temperatures. Our research aims to obtain water DSC thermogram that indicates the water vapor saturation content data for in the CO2-H2O binary system. natural gas with high CO2 contents (up to 50%) and low temperature (around 4 °C) using the Quartz Crystal Microbalance (QCM) and Tunable Diode Laser Spectroscopy (TDLAS) techniques, assuring the water saturation condition with a micro-DSC, and then correlating the obtained data using the Polar PC-SAFT equation of state.

CO2-rich reservoir fluids can induce asphaltene precipitation, which causes pipe clogging and serious economic losses. These high molecular mass aggregates represent one of the main challenges in thermodynamic modeling of reservoir fluids. Most commercial simulators only include two-phase equilibrium for the oil phase and use traditional equations of state such as Peng-Robinson and Soave-Redlich-Kwong, thus failing to predict asphaltene precipitation. The PVT-Atoms simulator, developed by the ATOMS group, uses the Cubic Plus Association (CPA) equation, which consists of a combination of Peng-Robinson and the Statistical Associating Fluid Theory (SAFT) equation. The software models liquid-liquid equilibrium and heterogeneous bubble points, simultaneously predicting asphaltene precipitation and the PVT properties of reservoir fluids. From diverse sets of experimental data, the simulator estimates the parameters of the CPA model through stochastic and deterministic optimization methods.

During production, petroleum is submitted to different temperature and pressure conditions, which can lead to precipitation of different solids, such as hydrates, asphaltenes and waxes. Among these flow assurance issues, wax deposition gains importance as the frontiers of oil exploration moves towards hostile environments, like deep water and the Artic. Wax deposition is hard to remediate, as it depends on mechanical removal of the deposits through pigging operations or chemical intervention like solvent soaking. As these different operations lead to production loss, the most cost effective strategy to deal with wax deposition is to avoid it during the design of production installations. Thus, the use of thermodynamic models for the calculation of solid-liquid equilibria (SLE) for mixtures of waxes and oil is very important to the petroleum industry. Therefore, our group studies, in collaboration with Petrobras, the thermodynamic aspects related to wax precipitation using different approaches available in the literature.

The formation of asphaltene plugs in piping represent a significant problem in oil production and refining. Asphaltenes are a collection of polydisperse molecules consisting mostly of polynuclear aromatics with varying proportions of aliphatic and alicyclic and small amounts of heteroatoms (oxygen, sulfur, vanadium, etc.). Problems in recovery and refining operations associated with asphaltenes are due primarily to their molecular size and their self-aggregation. Hence, a better understanding of asphaltene phase behavior and deposition requires a better understanding of how molecular size and aggregation affect phase behavior and deposition. For the flow assurance in oil and gas industry our group, in collaboration with Petrobras, we study thermodynamics and kinetics aspect related to asphaltene precipitation, deposition and agglomeration using both CPA type of equation of state and molecular simulation.

In the search for environmentally greener solvents, Deep Eutectic Solvents (DES) proved attractive for applications in various chemical processes. These compounds consist of mixtures between hydrogen bond donors and acceptors where, due to the strength of these bonds, at a certain proportion, they have a melting point lower than that of their pure components and lower than that of an ideal liquid mixture. Their highly non-ideal behavior has  encouraged the study of these systems from different  modeling perspectives.  In this regard, the use of advanced equations of state, such as the soft-SAFT approach, provides an attractive framework for reliable estimates of the Experimental and soft-SAFT predicted densities of choline chloride: ethylene glycol DESs  physicochemical behavior of DES, as the hydrogen bonding and other association effects can be explicitly considered in the model. Thus, one of our goals  is the thermodynamic characterization of DESs  using soft-SAFT by developing accurate transferable and semi-predictive models.
Free energy calculations are essential in obtaining industrial and academic interest thermodynamic properties. We can obtain such proper-ties using Molecular Dynamics (MD), applying alchemical transforma-tions, where non-physical thermodynamic pathways calculate the freeenergy difference. Recently, an approach called Linear Basis Function (LBF) was proposed to improve the efficiency of these calculations. The LBF modelis promising asit overcomes thedisadvantages ofexisting models while gathering their advantages. In our research, we propose modifications in the LBFmodel to reduce the number of required parameters. To validate our proposals, we calculated the octanol-water partition coefficient having small organic molecules as solutes. Comparisons of the obtained resultswith literature data indicate the effectiveness of our methodology. Ingeneral, our investigations emphasize the efficiency of the LBF approachand the wide range of improvement possibilities associated with it.

The concern about environmental pollution, the high consumption ofplastics, and the waste generated by society generates a growing interest in research centers to find more environmentally friendly alternatives for the production of polymers through green technologies. Conventional polymerization uses large amounts of organic solvents such as toluene, which are highly toxic and directly affect the environment and human health because of the vapors emission. In search of solving these problems, green solvent alternatives are presented for future work, using supercritical fluids such as CO2, ionic liquids (which can be used as a solvent or catalyst for the reaction), and a possible mixture between both for the synthesis of polymers free of toxic residues in eco-friendly processes.
Over the last decades, demands for biodegradable and biocompatible polymers have substantially increased, mainly for ecological and biomedical applications. Pressurized fluids such as propane and supercritical CO2 are attractive alternatives in replacement to organic solvents, especially due to their non-toxic character, low dielectric constant, and easy separation from the final product. Our recent works report the successful enzymatic ring-opening polymerization of globalide using pressurized fluids. Reactions carried out using supercritical CO2 reach 100% conversion and produce polyglobalide (PGl) with low dispersity  and molecular weight of around 25 kDa. The use of pressurized propane generate positive results in terms of molecular weight, producing PGl with  around 40 kDa. Pressurized fluids are becoming Enzymatic polymerization of PGl was carried out usan important clean ing supercritical CO2 and pressurized propane. alternative as solvents for polymerization reactions and many other reactional and processing systems.
The continuous increase in the production of synthetic plastics and the inadequate disposal of plastic waste have provided a considerable increase of these materials in aquatic environments, becoming a major environmental concern. The interest in understanding the mechanisms, at the molecular level, of the interaction of nanoplastics (NP) with other compounds using molecular simulation techniques is growing in the literature. NP can affect the secondary structure of proteins and change the lateral organization and diffusion of lipid membranes.

The research stream of Lattice Boltzmann Methods (LBM) is a relatively new candidate in the family of Computational Fluid Dynamics (CFD) research. Discretizing the Boltzmann’s Transport Equation with finite velocity sets and using the appropriate collision schemes can efficiently solve fluid flow and heat transfer problems. Fluid is considered as fictitious particle and probability distribution functions are characterising the evolution of each particle. Mass, momentum, and energy conservation rules are obliged on suitable lattice models. Navier-Stokes equations can easily be recovered when hydrodynamic limits of the lattice Boltzmann equations are considered. Complex boundary conditions can be incorporated naturally in the LBM thus making LBM the favourite choice for simulations of fluid flows and thermal transport in complex geometry e.g., porous media. It is proven that LBM provides accurate and stable solutions for complex geometry and turbulent flows. We, together with AGH University of science and technology, Poland, recently opened up this new research stream at ATOMS to look for real world solutions to address some genuine problems regarding fluid flow and heat transfer. Our current activities involves development of the theoretical foundations and the in-house software based on cascaded, cumulant and entropic isothermal/thermal LBMs i.e. the state-of-art computational tools, which will be applied to complex fluid flows through porous media that can be of great interest to petroleum industry applications e.g., multiphase flows, phase separation, phase transition, mixing of chemicals, reservoir simulations, etc...

In the oil industry, the problem of inorganic scaling can occur at various stages of the production chain, from the producing well and liners, to valves and primary processing equipment. Variables such as pressure, temperature, flow, and concentration of salts have a great influence on the deposition phenomena, the growth of which can lead to a total blockage of the pipe and consequent production stoppage. Elevated water content and concentration of carbon dioxide in the production fluid are the main issues that Schematic representation for the dynamic model for scaling precan cause diction. scaling deposition of calcium carbonate. We have been working on the deposition in flow pipes of aqueous electrolytic solution using mathematical models and compare it with experimental data, coupling the deposition and precipitation kinetics with the aqueous equilibrium calculation.

We are also working on the evaluation of the effect of ionic specificity on the electrophoretic mobility of calcium carbonate nanoparticles, the effect of some parameters on the Zeta potential of calcium carbonate for different rest time and kinetics of concentrations of Ca and Mg. CO2 bubble formation and the surface zeta potential of different materials to measure the surface fouling potential and its effect on fouling. The results are intended to understand better the phenomena involved in the formation of calcium carbonate scale, making predictions about deposit properties that will be applied in hydrodynamic studies.

Our research focuses on the study of materials and their applications by means of microscopic-scale modeling and computer simulation. In this way, we try to understand how the molecular constitution of a material determines its observed thermophysical properties. An exciting possibility is the study of yet undiscovered materials, entailing the prediction of their properties and the search for novel applications. This is the core of the discipline known as Material Design. The computational methods we employ in our investigations include advanced Monte Carlo (MC) methods such as Configurational-Bias MC, Multihistogram Reweighting, Multicanonical and other Non-Boltzmann Sampling methods, Transition-Matrix MC, and so on. Not only have we applied known methods, but also developed new ones and assembled many of them under a useful, generalized framework. For instance, we have being studying the equilibrium adsorption of polymers on solids with heterogeneous distributions of active sites, the effects of molecular topology on the scaling behavior and phase transitions of complex polymers, and the interaction between proteins and electrically charged surfaces of existing nanodevices.

The issues related to flow assurance in the oil industry have been addressed more frequently to avoid, for instance, wax and asphaltene precipitation. Therefore, we are working on research that aims to provide experimental data of phase equilibria and physical properties (viscosity and density) for n-alkanes mixed with high gas content (CO2 and CH4). The PCP-SAFT and Peng-Robinson Equation of State (EoS) are applied in, both Entropy and Helmholtz Scaling methods to foresee viscosity at different conditions, including high pressure and several compositions. The modeling part is essential to predict other conditions not covered by experimental data since the literature lacks information.

Mass transfer operations are quite recurrent and play a key role in processes design. In this sense, an appropriate modeling of composition grading in oil reservoirs depends on the knowledge of self-diffusion, Fick diffusion and thermal diffusion coefficients of mixtures of hydrocarbons and carbon dioxide at reservoir conditions. Considering the high cost and operational risks of the experimental determinations under high pressures, Molecular Dynamics represents an alternative approach for the determination of transport properties coefficients. In our research, a careful analysis of the methodology commonly employed in Molecular Dynamics for the calculation of mass transport coefficients is presented, and also new methodologies using Fourier Transforms are employed.

In terms of renewable energy sources, H2 appears to be an excellent choice on several criteria. However, the problems in using H2 are related to transport and storage. Underground storage in depleted or new reservoirs composed of porous matrixes is an alternative that is being explored. Also, storing CO2 in different types of reservoirs can mitigate the harmful effects caused to the planet. Our research uses molecular dynamics to obtain thermodynamic, structural, and transport properties of H2, CO2, and their mixtures confined in different porous media under typical conditions of Brazilian pre-salt reservoirs, in order to help optimize storage conditions at the nanoscale.

The main objective of this research is to establish separately the contributions of the isothermal gravitational field, thermal diffusion, and molecular association phenomena to the compositional grading observed in petroleum fields. Starting from the experience gathered from other fields in the literature where these phenomena are noticeable, new premises, methods of calculation and parameter estimation were then applied to case studies. Through  the microscopic equations of fluid transport, which support Irreversible Thermodynamics, different contributions for internal entropy generation, like heat conduction, molecular diffusion, and viscous dissipation are derived. Soret and Duffour effects are discussed, and the methods for calculation of thermal diffusion parameters for compositional grading are discussed.

The methods employed can be extended to other sedimentary basins, since one can always perform a parameter reestimation for local contexts.
 

In the oil and gas industry, in offshore installations, the occurrence of inorganic fouling is recurrent. These arise from the precipitation of certain salts, which may be formed on the surfaces of the tubes, or precipitate with time on the walls. Among the most common existing incrustations, mainly in the pre-salt area, is that of calcium carbonate.
These inorganic salt deposits can limit the flow of oil at the production stage, affecting or totally blocking certain equipment and valves. The most common current solutions to this problem, such as chemical inhibition agents, are costly. A possible alternative route is the utilization of physical inhibitors, such as the application of magnetic fields external to the flow of saline solutions.
An experimental system is proposed, linked to dynamic image analysis (DIA), in order to verify the effects of the magnetic field on the
crystallization steps involved in the calcium carbonate precipitation process.
Measurement of variables were pH, conductivity, and properties from the particle-size distributions was carried out and changes in the crystalline structure of calcium carbonate were analyzed by X-ray diffraction and scanning electron microscopy techniques.
Calcium carbonate scale formation commonly occurs in hard water pipelines, resulting in severe flow assurance problems in the oil industry.
The thermodynamic and kinetic behavior related to the formation and deposition of calcium carbonate nuclei is important to understand the scaling phenomenon. The main objective  of this research is the evaluation of the effect of ionic specificity on the electrophoretic mobility of calcium carbonate nanoparticles, the effect of some  parameters on the kinetics  of   CO2  bubble formation and the surface zeta potential of different materials to measure the surface fouling potential and its effect on fouling. The results are intended to understand better the phenomena involved in the formation of calcium carbonate scale, making predictions about deposit properties that will be applied in hydrodynamic studies.