The organic–inorganic dual anchoring strategy based on organic chelators and lacunary polyoxometalates for the preparation of efficient CoWS hydrodesulfurization catalysts

• Published in: Fuel (Guildford) 2024-03, Vol.360, p.130599, Article 130599
• Main Authors: Bao, Wenjing, Zhang, Cong, Yan, Dengwei, Sun, Fengyue, Yue, Changle, Wang, Chongze, Lu, Yukun
• Format: Article
• Language: English
• Subjects: Chelating agent; CoWS active phase; Hydrodesulfurization; Lacunary polyoxometalates
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2023.130599

[Display omitted] •A novel organic–inorganic ligand dual anchoring strategy was employed to prepare efficient S-Co(CA)W/Al2O3 catalyst.•Citric acid and SiW9 simultaneously anchored Co2+ to form chelate-promoter-lacunary polyoxometalates sandwich like molecules, realizing intimate contact of Co/W bimetal on precursor.•Organic ligands increase promotion degree and also generate carbon deposits to weaken the interaction of Al2O3 with active metals.•S-Co(CA)W/Al2O3 catalyst possessed abundant active phases and higher dispersion of (Co)WS2 layers, exhibiting excellent hydrodesulfurization activity and direct desulfurization selectivity. Designing catalysts with bimetallic intimate synergistic effects to enhance catalytic activity has always been a focused problem for hydrodesulfurization (HDS) systems. Efficient HDS catalysts with abundant CoWS active phases were prepared through novel organic–inorganic ligand dual anchoring strategy based on the organic chelating agents and lacunary polyoxometalates (POMs). Citric acid (CA) chelating agent and Co2+ promoter are pre-coordinated in the impregnating solution, the trivacant Keggin [SiW9O34]10- (SiW9) POMs attract the promoter through the nucleophilic oxygen groups at the vacant sites to form the CA-Co@SiW9 “sandwich-like” structure, which allows the organic chelator-promoter-active center to be intimate interaction in a single molecule, thus achieving atomic-scale Co-W proximity on the precursor. In the subsequent sulfidation process, CA delayed the reduction temperature of cobalt species, enabling more Co promoter to be anchored at the edge sites of WS2 clusters to form abundant CoWS active phases, which fully exerted the bimetallic intimate synergism in the HDS reaction. Furthermore, the carbon deposits generated from CA carbonation acted as secondary support weakening the interaction of active metals with Al2O3 support and increasing the sulfidation degree as well as the dispersion of active metals. As a result, the S-Co(CA)W/Al2O3 catalyst achieves a remarkable turnover frequencies (TOF) value of 1.24 × 10-3 s−1 in HDS reaction of dibenzothiophene (DBT). This dual anchoring method based on POMs inorganic ligand and organic chelator ligand provides a new idea for designing novel HDS catalysts.