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

Abstract

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.

Nanotechnology Applied to Thermal Enhanced Oil Recovery Processes: A Review

“…As can be seen, under the three atmospheres, the cracking of the asphaltenes occurs at several stages, and they start at 400, 426, and 465 °C for inert, air, and steam atmospheres, respectively [44,82,87]. Several authors explain this phenomenon due to the presence of a distribution of sizes of asphaltenes of high to low molecular weight, where the heavier fractions decompose at higher temperatures [30,45,88] and the different intensities of the different peaks is attributed to possible addition or aggregation reactions of n-C7 asphaltene after its initial cracking. After the asphaltene [49], inert gases [44], and air [82] performed at atmospheric pressure.…”

“…Additionally, the gasification of resins II and complex systems R:A (Resins: Asphaltenes) under isothermal and nonisothermal conditions, at temperatures below 240 • C. The authors found that the increase in content of resins II in the systems decreases the activation energy to carry out the decomposition of the system. Finally, considering the above, it is important to decompose these molecules in order to bring the crude oil to better viscosity conditions and API gravity to facilitate production, refinery, and transport operations [88]. However, the conventional thermal enhanced oil recovery processes do not generate an upgrading in the crude oil quality, due to the low temperatures at which it operates, since asphaltene and resins decompose mainly at temperatures above 400 • C [88].…”

“…Several studies propose the use of metal oxide nanoparticles for the enhancement of heavy and extra-heavy crude oil properties through interactions with the asphaltenes [45,88,129,130]. Thanks to the catalytic properties of the NiO nanoparticles, several technical approaches and particularly steam gasification reactions [24] have been carried out.…”

“…In general, with the increase in temperature, the conversion of tar into gas increases and, therefore, the amount of hydrogen increases [136]. When applying nanoparticles of Ni/Al 2 O 3 , Ni/Olivine, Ni/Fe 2 O 3 , the elimination of the tars is achieved in 99%, 93.1%, and 83.6%, respectively, at a temperature of 900 • C. The water gas shift reaction (WGS) has also been studied by using nanocatalysts based on cerium oxide (CeO 2 ) functionalized with different transition elements oxide (Fe, Ni, Co, and/or Pd) [88]. Here it was obtained an increase of the production of gases and light hydrocarbons facilitating the hydrogenation of asphaltene molecules due to three catalytic routes that involve the effect of the (a) interactions between metals and CeO 2 , (b) the redox cycle of the support, and (c) the production of hydrogen under two mechanisms that govern the WGSR: redox and formates.…”

“…Three components simplex-centroid mixture design with ceria support (CeO 2 ) functionalized with nickel oxide (NiO) and palladium oxide (PdO). Reprinted with permission[88]; Copyright 2019, MDPI.…”