Catalytic Conversion of n-C7 Asphaltenes and Resins II into Hydrogen Using CeO2-Based Nanocatalysts.

This study focuses on evaluating the volumetric hydrogen content in the gaseous mixture released from the steam catalytic gasification of n-C7 asphaltenes and resins II at low temperatures (<230 °C). For this purpose, four nanocatalysts were selected: CeO2, CeO2 functionalized with Ni-Pd, Fe-Pd, and Co-Pd. The catalytic capacity was measured by non-isothermal (from 100 to 600 °C) and isothermal (220 °C) thermogravimetric analyses. The samples show the main decomposition peak between 200 and 230 °C for bi-elemental nanocatalysts and 300 °C for the CeO2 support, leading to reductions up to 50% in comparison with the samples in the absence of nanoparticles. At 220 °C, the conversion of both fractions increases in the order CeO2 < Fe-Pd < Co-Pd < Ni-Pd. Hydrogen release was quantified for the isothermal tests. The hydrogen production agrees with each material's catalytic activity for decomposing both fractions at the evaluated conditions. CeNi1Pd1 showed the highest performance among the other three samples and led to the highest hydrogen production in the effluent gas with values of ~44 vol%. When the samples were heated at higher temperatures (i.e., 230 °C), H2 production increased up to 55 vol% during catalyzed n-C7 asphaltene and resin conversion, indicating an increase of up to 70% in comparison with the non-catalyzed systems at the same temperature conditions.

Physicochemical characteristics of calcined MnFe2O4 solid nanospheres and their catalytic activity to oxidize para-nitrophenol with peroxymonosulfate and n-C7 asphaltenes with air.

Manganese ferrite solid nanospheres (MSNs) were prepared by a solvothermal method and calcined at various temperatures up to 500 °C. Their surface area, morphology, particle size, weight change during calcination, surface coordination number of metal ions, oxidation state, crystal structure, crystallite size, and magnetic properties were studied. The MSNs were used as catalysts to activate potassium peroxymonosulfate (PMS) for the oxidative degradation of para-nitrophenol (PNP) from water and for the oxidation of n-C7 asphaltenes in flowing air at atmospheric (0.084 MPa) and high pressure (6 MPa). Mn was in oxidation states (II) and (III) at calcination temperature of 200 °C, and the crystalline structure corresponded to jacobsite. Mn was in oxidation states (III) and (IV) at 350 °C and in oxidation states (II), (III), and (IV) at 500 °C, and the crystalline structure was maghemite at both temperatures. MSN catalysts generated hydroxyl (HO·) and sulfate (SO4·-) radicals in the PMS activation and generated HO· radicals in the n-C7 asphaltene oxidation. In both reactions, the best catalyst was MSN calcined at 350 °C (MSN350), because it has the highest concentration of Mn(III) in octahedral B sites, which are directly exposed to the catalyst surface, and the largest total and lattice oxygen contents, favoring oxygen mobility for Mn redox cycles. The MSN350 sample reduces the decomposition temperature of n-C7 asphaltenes from 430 to 210 °C at 0.084 MPa and from 370 to 200 °C at 6.0 MPa. In addition, it reduces the effective activation energy by approximately 77.6% in the second combustion (SC) region, where high-temperature oxidation reactions take place.

Development of Nanofluids for the Inhibition of Formation Damage Caused by Fines Migration: Effect of the interaction of Quaternary Amine (CTAB) and MgO Nanoparticles.

Fines migration is a common problem in the oil and gas industry that causes a decrease in productivity. In this sense, the main objective of this study is to develop nanocomposites based on the interaction of quaternary amine (hexadecyltrimethylammonium bromide-CTAB) and MgO to enhance the capacity of retention of fine particles in the porous medium. MgO nanoparticles were synthesized by the sol-gel method using Mg(NO3)2·6H2O as a precursor. Nanoparticles were characterized by dynamic light scattering (DLS), the point of zero charge (pHpzc), thermogravimetric analysis, and Fourier transform infrared spectroscopy (FT-IR). Different nanoparticle sizes of 11.4, 42.8, and 86.2 nm were obtained, which were used for preparing two system nanofluids. These systems were evaluated in the inhibition of fines migration: in the system I MgO nanoparticles were dispersed in a CTAB-containing aqueous solution, and system II consists of a nanocomposite of CTAB adsorbed onto MgO nanoparticles. The fines retention tests were performed using Ottawa sand 20/40 packed beds and fine particles suspensions at concentrations of 0.2% in a mass fraction in deionized water. Individual and combined effects of nanoparticles and CTAB were evaluated in different treatment dosages. The analysis of the interactions between the CTAB and the MgO nanoparticles was carried out through batch-mode adsorption and desorption tests. The best treatment in the system I was selected according to the fines retention capacity and optimized through a simplex-centroid mixture design for mass fractions from 0.0% to 2.0% of both CTAB and MgO nanoparticles. This statistical analysis shows that the optimal concentration of these components is reached for a mass fraction of 0.73% of MgO nanoparticles and 0.74% in mass fraction of CTAB, where the retention capacity of the porous medium increases from 0.02 to 0.39 mg·L-1. Based on the experimental results, the nanofluids combining both components showed higher retention of fines than the systems treated only with CTAB or with MgO nanoparticles, with efficiencies up to 400% higher in the system I and higher up to 600% in the system II. To evaluate the best performance treatment under reservoir conditions, there were developed core flooding tests at fixed overburden pressure of 34.5 MPa, pore pressure at 6.9 MPa and system temperature at 93 °C. Obtaining critical rate increases in 142.8%, and 144.4% for water and oil flow in the presence of the nanofluid. In this sense, this work offers a new alternative for the injection of nanocomposites as a treatment for the problem of fines migration to optimize the productivity of oil and gas wells.

Upgrading of Extra-Heavy Crude Oils by Dispersed Injection of NiO-PdO/CeO2±Î´ Nanocatalyst-Based Nanofluids in the Steam.

The main objective of this study is to evaluate the injection of a dispersed nanocatalyst-based nanofluid in a steam stream for in situ upgrading and oil recovery during a steam injection process. The nanocatalyst was selected through adsorption and thermogravimetric experiments. Two nanoparticles were proposed, ceria nanoparticles (CeO2±Î´), with and without functionalization with nickel, and palladium oxides (CeNi0.89Pd1.1). Each one was employed for static tests of adsorption and subsequent decomposition using a model solution composed of n-C7 asphaltenes (A) and resins II (R) separately and for different R:A ratios of 2:8, 1:1, and 8:2. Then, a displacement test consisting of three main stages was successfully developed. At the beginning, steam was injected into the porous media at a temperature of 210 °C, the pore and overburden pressure were fixed at 150 and 800 psi, respectively, and the steam quality was 70%. This was followed by CeNi0.89Pd1.1 dispersed injection in the steam stream. Finally, the treatment was allowed to soak for 12 h, and the steam flooding was carried out again until no more oil production was observed. Among the most relevant results, functionalized nanoparticles achieved higher adsorption of both fractions as well as a lower decomposition temperature. The presence of resins did not affect the amount of asphaltene adsorption over the evaluated materials. The catalytic activity suggests that the increase in resin content promotes a higher conversion in a shorter period of time. Also, for the different steps of the dynamic test, increases of 25% and 42% in oil recovery were obtained for the dispersed injection of the nanofluid in the steam stream and after a soaking time of 12 h, compared with the base curve with only steam injection, respectively. The upgraded crude oil reached an API gravity level of 15.9°, i.e., an increase in 9.0° units in comparison with the untreated extra-heavy crude oil, which represents an increase of 130%. Also, reductions of up to 71% and 85% in the asphaltene content and viscosity were observed.

Influence of the Ce4+/Ce3+ Redox-Couple on the Cyclic Regeneration for Adsorptive and Catalytic Performance of NiO-PdO/CeO2±Î´ Nanoparticles for n-C7 Asphaltene Steam Gasification.

The main objective of this study is to evaluate the regenerative effect of functionalized CeO2±Î´ nanoparticles with a mass fraction of 0.89% of NiO and 1.1% of PdO in adsorption and subsequent decomposition of n-C7 asphaltenes in steam gasification processes. During each regeneration cycle, the adsorption capacity and the catalytic activity of the nanoparticles were evaluated. To estimate the adsorption capacity of the nanoparticles, adsorption kinetics were studied at a fixed concentration of n-C7 asphaltenes of 10 mg·L-1 as well as adsorption isotherms at three different temperatures at 25 °C, 55 °C, and 75 °C. To evaluate the catalytic activity, the loss of mass of the nanoparticles was evaluated by isothermal conversions with a thermogravimetric analyzer at 230 °C, 240 °C, and 250 °C, and at non-isothermal conditions involving a heating from 100 °C to 600 °C at a 20 °C·min-1 heating rate. The asphaltenes showed a high affinity for being adsorbed over the nanoparticles surface, due to the nanoparticles-asphaltene interactions are stronger than those that occur between asphaltene-asphaltene, and this was maintained during nine evaluated regeneration cycles as observed in the Henry's constant that increased slightly, with changes of 21%, 26% and 31% for 25 °C, 55 °C and 75 °C. Polanyi's adsorption potential decreases by 2.6% for the same amount adsorbed from the first cycle to the ninth. In addition, the catalytic activity of the nanoparticles did not change significantly, showing that they decompose 100% of the n-C7 asphaltenes in all cycles. However, the small decrease in the adsorption capacity and catalytic activity of the nanoparticles is mainly due to the presence and change in concentration and ratio of certain elements such as oxygen, iron or others at the surface of the nanoparticle as shown by X-ray photoelectron spectroscopy (XPS) analyses. Thermodynamic parameters of adsorption such as Δ H a d s o , Δ S a d s o , and Δ G a d s o and the effective activation energy (Ea) were calculated to compare adsorptive and catalytic performance during each cycle. There is an increase of 9.3% and 2.6% in the case of entropy and enthalpy, respectively, and a decrease of 0.5%, 3.1% and 6.5% for 25 °C, 55 °C and 75 °C respectively for the Gibss free energy from cycle 1 to cycle 9. It was found that these parameters are correlated with the Ce concentration and oxidation state ratios (Ce3+/Ce4+ couple) at the surface.

Optimization of the Load of Transition Metal Oxides (Fe2O3, Co3O4, NiO and/or PdO) onto CeO2 Nanoparticles in Catalytic Steam Decomposition of n-C7 Asphaltenes at Low Temperatures.

The main objective of this work is the catalyst optimization of Fe2O3-, Co3O4-, NiO- and/or PdO- (transition element oxides-TEO) functionalized CeO2 nanoparticles to maximize the conversion of asphaltenes under isothermal conditions at low temperatures (<250 °C) during steam injection processes. Adsorption isotherms and the subsequent steam decomposition process of asphaltenes for evaluating the catalysis were performed through batch adsorption experiments and thermogravimetric analyses coupled to Fourier-transform infrared spectroscopy (FTIR), respectively. The adsorption isotherms and the catalytic behavior were described by the solid-liquid equilibrium (SLE) model and isothermal model, respectively. Initially, three pairs of metal oxide combinations at a mass fraction of 1% of loading of CeNi1Pd1, CeCo1Pd1, and CeFe1Pd1 nanoparticles were evaluated based on the adsorption and catalytic activity, showing better results for the CeNi1Pd1 due to the Lewis acidity changes. Posteriorly, a simplex-centroid mixture design of experiments (SCMD) of three components was employed to optimize the metal oxides concentration (Ni and Pd) onto the CeO2 surface by varying the oxides concentration for mass fractions from 0.0% to 2.0% to maximize the asphaltene conversion at low temperatures. Results showed that by incorporating mono-elemental and bi-elemental oxides onto CeO2 nanoparticles, both adsorption and isothermal conversion of asphaltenes decrease in the order CeNi1Pd1 > CePd2 > CeNi0.66Pd0.66 > CeNi2 > CePd1 > CeNi1 > CeO2. It is worth mentioning that bi-elemental nanoparticles reduced the gasification temperature of asphaltenes in a larger degree than mono-elemental nanoparticles at a fixed amount of adsorbed asphaltenes of 0.02 mg·m-2, confirming the synergistic effects between Pd and Fe, Co, and Ni. Further, optimized nanoparticles (CeNi0.89Pd1.1) have the best performance by obtaining 100% asphaltenes conversion in less than 90 min at 220 °C while reducing 80% the activation energy.