Rational Design of Nickel Phosphide Hydrodesulfurization Catalysts: Controlling Particle Size and Preventing Sintering

Abstract

The size-dependent catalytic activity of Ni 2 P for hydrodesulfurization (HDS) remains unstudied because the traditional temperature programmed reduction (TPR) method used in catalyst preparation results in highly polydisperse Ni 2 P particles. The ability to control the Ni 2 P particle size in the range 5−20 nm by varying the quantity of oleylamine in solution-phase arrested precipitation reactions is reported. Particles were introduced to a high surface area silica support (Cab-O-Sil, M-7D grade, 200 m 2 /g) via incipient wetness, and HDS activity was probed against dibenzothiophene (DBT). All samples were less active than TPR prepared materials, and the smallest particles were the least active, contrary to expectation. This is attributed in part to particle sintering under HDS conditions. Sintering occurs independently of wt% loading of catalyst, time, incipient wetness procedure, and ionic additives, at all temperatures greater than 200 °C. Sintering is minimized by encapsulation of Ni 2 P nanoparticles in a mesoporous silica shell, achieved by sol−gel silica formation around Ni 2 P-containing surfactant liquid crystal assemblies and subsequent calcination, resulting in a doubling of HDS activity.

The Birth of Nickel Phosphide Catalysts: Monitoring Phosphorus Insertion into Nickel

“…For example, nanoparticles of Ni 2 P, Ni 12 P 5 , and Ni 5 P 4 show contrasting performances in the HER . Broadly, a good understanding of the surface chemistry of metal phosphides produced by colloidal routes is essential to their development in other branches of catalysis, for example, hydrotreatment and selective hydrogenation reactions …”

Simultaneous Control of Composition, Size, and Morphology in Discrete Ni2–xCoxP Nanoparticles

“…), solution-phase arrestedprecipitation reactions enable excellent control of size, shape and composition, producing samples comprising narrowly polydisperse, discrete nanoparticles. [18][19][20][21] This approach has been extensively employed for the synthesis of binary phosphides, and these have recently been demonstrated to be effective as model catalysts for HDS 22,23 as well as electrocatalysts for HER. [6][7][8][9][10] In contrast, few examples of arrested precipitation reactions delivering ternary phosphide nanoparticles are reported.…”

Mild and Selective Hydrogenation of Nitrate to Ammonia in the Absence of Noble Metals

“…35 Initially thought to be a semiconductor, electronic structure calculations revealed that bulk Ni 2 P is actually metallic. 36,37,38 Interestingly, their resemblance to noble metals goes well beyond HER, as first row transition metal phosphides are also active catalysts in hydrotreating (HDX, X = S or hydrodesulfurization, 39,40,41,42 O or hydrodeoxygenation 43,44,45 , and N or hydrodenitrogenation 46,47 ), alkyne hydrogenation, 48,49,50,51 and hydrodearomatization reactions. 52 The ability of Ni 2 P and other Earth-abundant, binary metal phosphides to readily and reversibly adsorb hydrogen (H 2 ), perform a wide range of hydrogenation-like reactions, and achieve high product selectivities strongly suggest that they could also catalyze the hydrogenation of other, typically more challenging reactants, such as nitrate (NO 3 -).…”