High asphaltene content in heavy crude oil normally generates adverse rheological properties that affect the flow through the reservoir, preventing optimal hydrocarbon production. It has been demonstrated that using nanoparticles may improve the mobility of oil. Nanoparticles may be used as adsorbents and catalysts in the oil industry for in situ upgrading. The main objective of this study was to investigate the sorption kinetics and the thermodynamic equilibrium for asphaltene sorption onto nickel and/or palladium oxides supported on fumed silica that was nanoparticulated at different times, temperatures, and concentrations. After adsorption, thermally cracked asphaltenes from Colombian crude oil were investigated using catalytic oxidation. The asphaltenes adsorbed onto the selected nanoparticles were subjected to thermal decomposition up to 700 °C in a thermogravimetric analyzer. This study was realized using an experimental design with a measured simplex–centroid of the three components by varying the wt % of the palladium and nickel oxides as well as the fumed silica as the support. The silica nanoparticles were characterized using N2 adsorption at 196 °C and X-ray diffraction. The Langmuir and Freundlich models were used to correlate the experimental sorption equilibrium data. The experimental asphaltene adsorption isotherm data were adequately adjusted using the Freundlich model. The adsorption of asphaltenes on NiO and/or PdO supported on fumed silica was much higher than that over fumed silica over the range of the tested equilibrium concentrations. Pseudo-first- and pseudo-second-order kinetic models were applied to the experimental data obtained at different asphaltene concentrations from 100 to 1500 mg/L for the virgin fumed silica (S) and fumed silica-supported materials (SHSs); better fits were found for the pseudo-second-order model. However, the nanoparticles significantly decreased the asphaltene decomposition temperature and activation energy. The catalyst kinetics was calculated using the Ozawa–Flynn–Wall Model (OFW). All of the nanoparticles demonstrated high catalytic activity toward asphaltene decomposition in the following order at 0.2 mg/m2 asphaltene concentration on nanoparticle surfaces: SNi1 < SNi1Pd1< SNi0.66Pd0.66 < SPd1 < SPd2 < SNi2 < S. Consequently, using nanoparticles significantly enhanced the thermal decomposition of asphaltenes, improving the mobility of heavy oils in situ.

Asphaltenes exhibit an amphiphlic behavior and tend to form colloidal i-mers, because of their chemical structure. The formation of colloidal aggregates can generate formation damage for the precipitation and/or deposition of asphaltenes, because of the degree of self-association, altering the wettability of rock surface and significantly affect crude oil viscosity and specific gravity. This study aims at introducing a novel model for describing, at the macroscopic level, the adsorption equilibria of self-associating molecules such as asphaltenes in solution onto solid surfaces based on the "chemical theory". The model describes the adsorption isotherms temperature-dependent using three parameters, namely, maximum amount adsorbed, constant of i-mer reactions, and Henry's law constant. Furthermore, a temperature-independent model of five parameters, based on the modifications of the constants of reaction and Henry's law using an Arrhenius-type equation was proposed for estimating the thermodynamics parameters, such as ΔG ads °, ΔH ads °, and ΔS ads °of the adsorption process. This model improves the understanding of interactions asphaltene−asphaltene and asphaltene−solid surface on the adsorption−equilibrium process. The theoretical predictions of isotherms were validated successfully by determining the root mean-square errors (RSM%) between data obtained from published literature and values predicted for asphaltenes and surfaces with differing chemical natures. More than 40 experimental data taken from literature have been used for validating the solid−liquid equilibrium (SLE) model for describing the adsorption isotherm of asphaltenes from different origins on surfaces with different chemical nature, which shows the model robustness due to the complexity of the liquid phase adsorption for those complex molecules.

This study is a continuation of our previous works on the use of metal-based nanoparticles for the adsorption of asphaltenes and its subsequent catalytic thermal decomposition. In this study, we evaluated the effects of asphaltene aggregation on the adsorption process and the subsequent catalytic oxidation using fumed silica and nanoparticles of NiO and/or PdO supported on fumed silica. Adsorption isotherms were constructed through batch adsorption experiments at 25°C by using mixtures of n-heptane and toluene in amounts of 0, 20 %v/v (heptol 20) and 40 %v/v (heptol 40) of n-heptane to obtain different aggregate sizes of asphaltenes. Subsequently, asphaltene oxidation in the presence and absence of the nanoparticles was carried out in a TGA/FTIR system to investigate the impact of adsorbed asphaltene aggregates on the catalytic activity of the selected nanoparticles. The adsorption isotherms were described by the solid-liquid equilibrium (SLE) model, and the catalytic behavior of the nanoparticles was compared based upon the trend of effective activation energies using the isoconversional method of Ozawa−Flynn−Wall (OFW). The results showed that the K parameter of the SLE model for both nanoparticles followed the trend of heptol 40 > heptol 20 > toluene, indicating that as the amount of precipitant in the solution increases, a higher degree of asphaltene self-association on the active site of the catalysts is found. On the other hand, the H parameter revealed higher adsorption affinities as the nheptane in the solution increased. However, when different adsorbents were compared at a fixed asphaltene concentration from the same solution it was found that the use of functionalized nanoparticles led to a lower degree of asphaltene self-association and a higher affinity. A correlation between the effective activation energies from the OFW model and the SLE parameters was developed, finding that for a fixed adsorbent, the E α increases as the affinity and the degree of self-association of asphaltenes increases. However, when the same asphaltenes were compared using different adsorbents, it was observed that the E α increases as the affinity decreases and the degree of asphaltene selfassociation increases. Consequently, this work shows the effect of the adsorption process on the catalytic activity of the nanoparticles. The reported results should give a better context for the use of such nanoparticles for the upgrading of heavy and extra-heavy oil.

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The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Reactor (SBR) operated for EBPR and finally validated with two experiments. The precipitation model proposed was able to reproduce the dynamics of amorphous calcium phosphate (ACP) formation and later crystallization to hydroxyapatite (HAP) under different scenarios. The model successfully characterised the EBPR performance of the SBR, including the biological, physical and chemical processes.

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Asphaltenes may generate production loss in oil reservoirs, because of several factors related to the interaction between the asphaltene molecules, aggregates, and the reservoir rock. Consequently, this could alter the wettability of the rock surface, increase the viscosity of the crude oil, and reduce the permeability of the porous media. In a previous study, we have developed the solid−liquid equilibrium (SLE) model based on Chemical Theory to describe the adsorption behavior of asphaltenes onto porous and nonporous solid surfaces. However, the SLE model neglects the effect of pressure on the interactions of asphaltene−asphaltene and asphaltene−aggregate−solid surfaces of the reservoir rock primarily under reservoir conditions (RC). Thus, in this study, to account for the effect of pressure, a modification to the previously developed SLE equation is presented. In this study, a novel and original modelcalled the SLE-RC model of adsorptionhas been proposed to describe the adsorption mechanism mainly under reservoir conditions, for which the pressure and temperature effect has been evaluated. This model describes the temperature−pressure−dependent adsorption isotherms with five parameters: the maximum amount adsorbed, the constant of the i-mer reactions, Henry's law constant, the molar volume, and the solubility parameter of the asphaltenes. The proposed model has been validated with adsorption tests on porous media under flow conditions at different pressures and temperatures. The dynamic adsorption experiments were performed at different asphaltene concentrations (100−2000 mg/L), pressures (6.89−17.24 MPa), and temperatures (313−353 K). The SLE-RC model was successful validated using more than five experimental data describing the adsorption isotherms of the asphaltene onto a packed bed of silica sand at high pressure and temperature and following a Type III behavior with root-mean-square errors (RMSE%) below 2%. In addition, the packed sands used in the adsorption tests were analyzed based on surface and color changes using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) analysis, and polarized light microscopy (PLM); the results were in agreement with the SLE-RC model parameters.

The production of heavy and extra-heavy oil is challenging because of the rheological properties that crude oil presents due to its high asphaltene content. The upgrading and recovery processes of these unconventional oils are typically water and energy intensive, which makes such processes costly and environmentally unfriendly. Nanoparticle catalysts could be used to enhance the upgrading and recovery of heavy oil under both in situ and ex situ conditions. In this study, the effect of the Ni-Pd nanocatalysts supported on fumed silica nanoparticles on post-adsorption catalytic thermal cracking of n-C 7 asphaltenes was investigated using a thermogravimetric analyzer coupled with FTIR. The performance of catalytic thermal cracking of n-C 7 asphaltenes in the presence of NiO and PdO supported on fumed silica nanoparticles was better than on the fumed silica support alone. For a fixed amount of adsorbed n-C 7 asphaltenes (0.2 mg/m 2 ), bimetallic nanoparticles showed better catalytic behavior than monometallic nanoparticles, confirming their synergistic effects. The corrected OzawaFlynn-Wall equation (OFW) was used to estimate the effective activation energies of the catalytic process. The mechanism function, kinetic parameters, and transition state thermodynamic functions for the thermal cracking process of n-C 7 asphaltenes in the presence and absence of nanoparticles are investigated.