Hydrodemetallation and Hydrodesulfurization Spent Catalysts Elemental Analysis: Comparison of Wavelength Dispersive X-ray Fluorescence and Atomic Emission Spectrometries

Abstract

Petroleum industries continuously consume catalysts on very large scales. The recycling of spent catalysts is thus of major economic and environmental importance and its first step consists of the characterization of the valuable metal content. Wavelength dispersive X-ray fluorescence (WDXRF) analysis is compared with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the analysis of five samples of spent hydrodesulphurization (HDS) and hydrodemetallization (HDM) catalysts. The elements are considered for their economic interest (Co, Ni, Mo, and V) or for the problems that can arise when they are present in the sample in significant quantities (Al, As, P, Fe). First, the systematic comparison of the analysis of known synthetic samples was performed. The originality here is that the samples were first beaded with lithium tetraborate (Li₂B₄O₇) for WDXRF analysis and then dissolved in hot HCl 6M for ICP-AES measurements. With this processing, we were able to clearly identify the origin of analytical problems when they arose. Second, the semi-quantitative protocol of WDXRF is compared with the quantitative procedure. Finally, the analysis of the spent catalysts is presented and the information gained by the systematic comparison of ICP-AES and WDXRF is shared. The interest of the simultaneous determination by the two techniques when such complicated heterogeneous matrices are involved is clearly demonstrated.