Development of an Analytical Approach to Study the Surface Morphology and Roughness Analysis of Commercial Hydrotreating CoMo-γAl2O3 Catalysts via Atomic Force Microscopy (AFM) Analysis

Abstract

In this work a fully analytical approach for atomic force microscopy (AFM) (non-contact mode) is proposed to determine surface roughness, morphology, and topography of two commercial CoMo-γAl₂O₃ catalysts (Ketjenfine 124-3E and Ketjenfine 165) that are used in hydrotreating process (HTP) in Iraqi refineries. All parameters of the AFM image (amplitude, hybrid and spatial parameters) were discussed with a new insight and a detailed description of how the nano-particles were built in and distributed in hypothetical multi layers based on mathematical calculations of volume and surface area based on regarding that each individual grain has a sphere-like shape of a specific diameter. A clear relationship between grain number and average diameter was noticed, due to the increase in grain average diameter of KF124-3E (143.47 nm) comparing to that of KF165 (120.21) leads to make the density of grain distribution for the latter is greater than that of KF124. Surface area of total grains of Ketjenfine 124-3E and Ketjenfine 165 were 8 919 303.275 and 8 031 267.809 nm², respectively. Higher roughness average (S_a) value of catalyst KF165 (18.4 nm) means the reactants will have more opportunity for complete reaction. Root mean square (S_q) values were 8.16 nm for KF124-3E and 21.5 nm for KF165 indicating that KF165 is rougher than KF124-3E. Surface skewness of KF124-3E and KF165 were 0.00031, –0.168, respectively. For both hydrotreating catalysts the surface kurtosis value (S_ku) was about ≤2.0 and the distribution curves is Platykurtic. Root means square slope (S_dq) for KF165 catalyst is 1.31 nm^–1, which is approximately four times greater than that of KF124-3E (0.35 nm^–1) indicating that KF165 has rougher surface profile.