Cardanol/SiO2 Nanocomposites for Inhibition of Formation Damage by Asphaltene Precipitation/Deposition in Light Crude Oil Reservoirs. Part I: Novel Nanocomposite Design Based on SiO2-Cardanol Interactions

This study aims to design a novel green nanocomposite based on the synergistic effect between silica nanoparticles (SN) and cardanol (CDN). The latter is an environmentally friendly dispersant compound extracted from the cashew nut shell waste. Three cardanol/SiO2 nanocomposites were synthesized and named as 5CSN, 7CSN, and 9CSN based on the mass fraction of cardanol on the surface of the SiO2 nanoparticles of 5, 7, and 9%, respectively. The nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and total surface acidity through temperature-programmed desorption of NH3 (TPD-NH3). The binding of CDN molecules on the SiO2 surface precedes an increase in hydrodynamic diameter and total surface acidity due to the exposure of the meta-alkyl chain, phenolic -OH groups, and aromatic rings on the nanocomposite surface. Besides, cardanol/SiO2 interactions were explained from adsorption/desorption isotherms, showing a behavior type I under IUPAC classification. Findings suggest that CDN molecules were highly desorbed, especially at CDN initial dosages of up to 25,000 mgh.L-1 with CDN desorbed percentages over 30.5%. Last, the nanocomposites were evaluated as inhibitors of the asphaltene precipitation/deposition through adsorption isotherms and aggregation kinetics of asphaltene. CDN attached to SiO2 nanoparticles leads to a heterogeneous surface with several functional groups that promote the asphaltene uptake and the reduction of their aggregate size. A higher amount of CDN on the SiO2 surface promotes a surface with high heterogeneity favoring its capability to interact with the asphaltene aggregates. It was found that the adsorption of n-C-7 asphaltenes onto the surface of the nanocomposite leads to a decrease in the available asphaltenes in the bulk solution, which reduce the collision and fragmentation phenomena of the asphaltene aggregates, leading to reductions in the aggregate sizes of 31.5, 50.9, 57.5, and 58.5% in the presence of SN, 5CSN, 7CSN, and 9CSN, respectively, at a fixed nanocomposite dosage of 500 mg.L-1. Thus, based on the decrease of the mean aggregate size in the liquid phase and the n-C-7 asphaltene affinity toward the nanocomposite surface, the evaluated nanomaterials exhibit the following trend: 9CSN > 7CSN > 5CSN > SN. This approach provides an understanding of the role of CDN nanocomposites in the inhibition of asphaltene formation damage via the capture of heavy oil fraction and the decrease of the size of the aggregate in the oil matrix.