Removal of nickel and calcium from crude oil using core-shell materials grafted with N-substituted pyridines

Abstract

The existence of calcium and nickel in crude oil causes serious damage to oil processing equipment and reduces the quality of products. These metals are extremely hard to remove as they exist in form of stable oil-soluble complexes. If they could be removed during the electric desalination process, economic benefits will be greatly improved. The current study thus aimed to seek clean and non-corrosive demetallizing agents to chelating calcium and nickel during the electric desalination process of crude oil. Two different N-substituted pyridines based core-shell materials of P2VP@SiO2 (2-vinylpyridine) and P4VP@SiO2 (4-vinylpyridine) were first prepared, and their metal adsorption capacity and selectivity were explored and compared. The structure and mass grafting ratios (GR) of two materials were determined by FT-IR, TGA, elemental analysis (EA), GPC, SEM and TEM. The GR of P2VP@SiO2 and P4VP@SiO2 under different monomer concentrations, reaction temperature and duration were studied. In addition, the effects of various process conditions on nickel and calcium removal rates using the prepared P2VP@SiO2 and P4VP@SiO2 were investigated. It was worth noting that due to the difference in N substitution positions, for the same pyridine functional group, P2VP@SiO2 exhibited more stable adsorption selectivity, while adsorption capacity of P4VP@SiO2 for calcium and nickel is much better than P2VP@SiO2. The calcium and nickel removal rates by P4VP@SiO2 reached 61.3% and 67.2%, respectively. Briefly, P4VP@SiO2 could be used as a highly efficient demetallizing agent for removing calcium and nickel in crude oil, with high metal adsorption capacity.