Some effects of sulfiding of a NiMo/Al2O3 catalyst on its activity for hydrodenitrogenation of quinoline

Transition metal chalcogenide bifunctional catalysts for chemical recycling by plastic hydrocracking: a single-source precursor approach

Sulfided nickel, an established hydrocracking and hydrotreating catalyst for hydrocarbon refining, was synthesized on porous aluminosilicate supports for the hydrocracking of mixed polyolefin waste. Zeolite beta, zeolite 13X, MCM41 and an amorphous silica-alumina catalyst support were impregnated with the single-source precursor (SSP) nickel (II) ethylxanthate for catalyst support screening. Application of this synthesis method to beta-supported nickel (Ni@Beta), as an alternative to wet impregnation using aqueous nickel (II) nitrate, provided catalytic materials with higher conversion to fluid products at the same mild batch reaction conditions of 330°C with appropriate agitation and 20 bar H₂ pressure. Mass balance quantification demonstrated that SSP-derived 5wt%Ni@Beta yielded a greater than 95 wt% conversion of a mixed polyolefin feed to fluid products, compared with 39.8 wt% conversion in the case of 5wt%Ni@Beta prepared by wet impregnation. Liquid and gas products were quantitatively analysed by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS), revealing a strong selectivity to saturated C₄ (37.3 wt%), C₅ (21.6 wt%) and C₆ (12.8 wt%) hydrocarbons in the case of the SSP-derived catalyst.

Accelerating Kinetic Parameter Identification by Extracting Information from Transient Data: A Hydroprocessing Study Case

Hydroprocessing reactions require several days to reach steady-state, leading to long experimentation times for collecting sufficient data for kinetic modeling purposes. The information contained in the transient data during the evolution toward the steady-state is, at present, not used for kinetic modeling since the stabilization behavior is not well understood. The present work aims at accelerating kinetic model construction by employing these transient data, provided that the stabilization can be adequately accounted for. A comparison between the model obtained against the steady-state data and the one after accounting for the transient information was carried out. It was demonstrated that by accounting for the stabilization, combined with an experimental design algorithm, a more robust and faster manner was obtained to identify kinetic parameters, which saves time and cost. An application was presented in hydrodenitrogenation, but the proposed methodology can be extended to any hydroprocessing reaction.

Preparation and characterization of NiW supported on Al-modified MCM-48 catalyst and its high hydrodenitrogenation activity and stability

Al-containing MCM-48 with different Si/Al ratios and aluminum free MCM-48 materials were successfully prepared with CTAB and P123 as a co-template.

Mechanism of Hydrodenitrogenation on Phosphides and Sulfides

The mechanism of hydrodenitrogenation (HDN) of 2-methylpiperidine was studied over a silica-supported nickel phosphide catalyst (Ni2P/SiO2, Ni/P = 1/2) and a commercial Ni-Mo-S/Al2O3 catalyst in a three-phase trickle-bed reactor operated at 3.1 MPa and 450-600 K. Analysis of the product distribution as a function of contact time indicated that the reaction proceeded in both cases predominantly by a substitution mechanism, with a smaller contribution of an elimination mechanism. Fourier transform infrared spectroscopy (FTIR) of the 2-methylpiperidine indicated that at reaction conditions a piperidinium ion intermediate was formed on both the sulfide and the phosphide. It is concluded that the mechanism of HDN on nickel phosphide is very similar to that on sulfides. The mechanism on the nickel phosphide was also probed by comparing the reactivity of piperidine and several of its derivatives in the presence of 3000 ppm S. The relative elimination rates depended on the structure of the molecules, and followed the sequence: 4-methylpiperidine approximately piperidine > 3-methylpiperidine > 2,6-dimethylpiperidine > 2-methylpiperidine. [Chemical structure: see text] This order of reactivity was not dependent on the number of alpha-H or beta-H atoms in the molecules, ruling out their reaction through a single, simple mechanism. It is likely that the unhindered piperidine molecules reacted by an S(N)2 substitution process and the more hindered 2,6-dimethylpiperidine reacted by an E2 elimination process.