Effect of organic phosphorus addition on the state of active metal species and catalytic performance of NiW/Al2O3 hydrodesulfurization catalyst

Abstract

This article proposes a novel organic additive 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) for the preparation of NiW/Al2O3 efficient hydrodesulfurization (HDS) catalysts. The effects of HEDP on the nature of the tungsten and nickel species supported on the support surface after drying and calcination steps were revealed by employing ultraviolet–visible spectroscopy (UV–Vis), Raman spectroscopy, N2 adsorption–desorption and H2 temperature programmed reduction (H2-TPR). While the slab morphology and the proportion of NiWS phases were determined by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Finally, dibenzothiophene (DBT) was used as a probe to evaluate the effects of HEDP modification on the catalytic performance of the prepared catalyst. The results indicate that the addition of HEDP can facilitate the formation of more polymerized tungsten oxide species and improve the availability of surface nickel atoms. The weakened interaction between active metals and support generate higher stacking numbers and shorter slab lengths among WS2 crystals on the corresponding catalyst, promote the sulfidation of both Ni and W species and enhance the proportion of NiWS phase. The catalytic evaluation results show that the HEDP-modified catalyst exhibits efficient HDS activity and higher DDS selectivity compared to the phosphoric acid-modified reference catalyst, which is attributed to a large number of accessible NiWS active sites. The present work relates the addition of organic additives with the formation of NiW species and the catalytic activity. The results highlight that the addition of HEDP is an effective strategy to improve the performance of HDS catalysts.