Effects of Surface Modification on the Catalytic Performances of Nickel Sulfide Nanocatalysts for Residue Hydrocracking: A Monte Carlo Simulation and Experimental Study

Saturates, aromatics, resin, and C-7 asphaltene (SARA) fractions of feedstock were analyzed systematically, and molecular models were constructed. The Monte Carlo method was utilized to investigate the intermolecular interactions between SARA fractions and the ligands absorbed on nickel sulfide nanocatalysts. Additionally, the structural characteristics of the hydrocracked products were analyzed by using elemental analysis, (HNMR)-H-1 spectroscopy, and FTIR spectroscopy to study the effect of surface modification on the catalytic performances of nickel sulfide nanocatalysts. Simulation results reveal that oleic acid and 1-dodecanethiol have a better miscibility with aromatic fractions of residue than cetyltrimethyl ammonium bromide and that oleic acid has a high affinity and selectivity to C-7 asphaltene. Adsorption experiments show that nickel sulfide nanocatalysts modified with oleic acid and 1-dodecanethiol present a certain core affinity in the diffusion of residue colloid, which leads to a higher catalyst concentration in C-7 asphaltene than the average value in the feedstock. Subsequently, experimental data demonstrate that surface modification with oleic acid and 1-dodecanethiol enhances the catalytic activity of nickel sulfide nanocatalysts, which also facilitates the hydrogenation of C-7 asphaltene. Furthermore, nickel sulfide nanocatalysts modified with oleic acid show the best hydrogenation and anticoke activity because of the affinity between oleic acid and C-7 asphaltene.