Effect Of Multifunctional Nanocatalysts On N-C-7 Asphaltene Adsorption And Subsequent Oxidation Under High-Pressure Conditions

This study was carried out to evaluate the effect of high pressure on the oxidation kinetics of n-heptane asphaltenes in the presence and absence of AuPd/Ce0.62Zr0.38O2 catalysts. Bimetallic Au-Pd catalysts with Au/Pd molar ratios from 3.5 to 9.6 were synthesized by deposition-precipitation of Au and followed by incipient wetness impregnation of Pd (3:1AuPd and 10: 1AuPd). Adsorption isotherms between hydrocarbons and nanocatalysts were constructed varying the initial asphaltene concentration from 100 to 1500 mg.L-1. Subsequent oxidation was evaluated using thermogravimetric analysis under an air atmosphere, at different pressures from 0.084 to 6.0 MPa in a wide temperature range between 100 and 800 degrees C. Kinetic parameters were calculated using a first-order kinetic model, considering the system pressure. Adsorption affinity increases in the order support < 3:1AuPd < 10:1AuPd. The catalytic activity of the nanocatalyst was highly dependent on the employed temperature and pressure. Their presence reduces the n-C-7 asphaltene decomposition temperature from 450 degrees C to temperatures below 200 degrees C for all catalysts used at 6.0 MPa. The main decomposition peaks are presented at 150, 170, and 210 degrees C for 10:1AuPd, 3: 1AuPd, and support, at 6.0 MPa, respectively. Besides, the oxygen chemisorption (OC) region is favored as the material has a greater catalytic activity, increasing from 9.0 to 14.0% (on the load asphaltene basis calculation) for the support and 10:1AuPd catalyst. This was corroborated by the activation energy, which is reduced by more than 30% for all pressures evaluated with the best system. Besides, 89.0 and 80.0% of the mass are lost in the decomposition of the chemisorbed oxygen (DCO) thermal event for the 10:1AuPd and 3:1AuPd nanocatalysts, respectively. Finally, first and second combustions were carried out at temperatures below 240 degrees C at 6.0 MPa for the 10:1AuPd system, which is a very promising result to determine the reaction pathway for the heavy and extraheavy crude oils during FOR application.