Effect of NTA addition on the formation, structure and activity of the active phase of cobalt–molybdenum sulfide hydrotreating catalysts

Study on ultrasound-assisted precipitation for preparing Ni/Al2O3 catalyst

With the rapid development of oil hydrogenation industry, the development of oil hydrogenation catalyst has also become a research hotspot. In this paper, ultrasound-assisted precipitation technique is used to prepare Ni/Al₂O₃ catalyst. The effect of ultrasonic output power on catalyst performance is investigated. The prepared catalyst is applied to the hydrogenation reaction of castor oil. It is found that the prepared catalyst shows the best hydrogenation performance when ultrasonic output power, frequency and ultrasonic treatment time are 80 W, 40 kHz and 600 min respectively. It also indicates that ultrasound-assisted precipitation technique can reduce the particle size and increase the specific surface area of Ni/Al₂O₃ catalyst so that its activity is improved. In addition, six important elements that should be considered in the development of industrial oil refining catalysts are discussed, and the effects of these factors on the catalyst performance are discussed. Finally, new way for improving catalyst performance is given, and the application of some new materials and methods in oil refining is introduced.

Promoting effects of SO42− on a NiMo/γ-Al2O3 hydrodesulfurization catalyst

SO₄²⁻ anchors to a NiMo/γ-Al₂O₃ catalyst, weakening the metal–support interactions, inhibiting MoS₂ aggregation, increasing the number of Ni–Mo–S sites, and thus improving its activity and stability.

Maximizing Active Site Concentrations at Ni-Substituted WS2 Edges for Hydrogenation of Aromatic Molecules

High concentrations of Ni in bimetallic sulfide catalysts lead to the formation of segregated Ni sulfides (NiS_x), which are rather inactive alone as large crystallites and even impede the accessibility of active sites at the sulfide slab edges that catalyze a multitude of hydrogenation reactions and H₂ and CO₂ activation processes. Treatment of Ni-WS₂/γ-Al₂O₃ catalysts in aqueous acids, particularly concentrated HCl, results in a significant reduction of NiS_x and ≤5-fold enhancement of the phenanthrene hydrogenation rate. Using infrared (IR) spectroscopy of probe molecules, we show that the acid-treated catalysts have a high concentration of accessible metal edge sites, a high degree of Ni substitution, and consequently a high sulfhydryl (SH) concentration at the slab edges in the presence of H₂. The site-specific "turnover frequency" (based on SH concentrations determined by IR measurements) is identical for all parent and acid-treated sulfide catalysts studied, showing that excess NiS_x does not influence electronic properties.

A novel method of monitoring the sulfidation of hydrotreating catalysts: the conversion of carbonyl sulfide

The conversion of COS during the sulfidation of HDS catalysts allows one to determine the temperature range of formation of CoMoS sites.