Hydrodenitrogenation of Quinoline and Decahydroquinoline Over a Surface Nickel Phosphosulfide Phase

Controlled Surface Modification of Cobalt Phosphide with Sulfur Tunes Hydrogenation Catalysis

Transition metal phosphides have shown promise as catalysts for water splitting and hydrotreating, especially when a small amount of sulfur is incorporated into the phosphides. However, the effect of sulfur on catalysis is not well understood. In part, this is because conventional preparation methods of sulfur-doped transition metal phosphides lead to sulfur both inside and at the surface of the material. Here, we present an alternative method of modifying cobalt phosphide (CoP) with sulfur using molecular S-transfer reagents, namely, phosphine sulfides (SPR3). SPR3 added sulfur to the surface of CoP and using a series of SPR3 reagents having different P═S bond strengths enabled control over the amount and type of sulfur transferred. Our results show that there is a distribution of different sulfur sites possible on the CoP surface with S-binding strengths in the range of 69 to 84 kcal/mol. This provides fundamental information on how sulfur binds to an amorphous CoP surface and provides a basis to assess how number and type of sulfur on CoP influences catalysis. For the catalytic hydrogenation of cinnamaldehyde, intermediate amounts of sulfur with intermediate binding strengths at the surface of CoP were optimal. With some but not too much sulfur, CoP exhibited a higher hydrogenation productivity and a decreased formation of secondary reaction products. Our work provides important insight into the S-effect on the catalysis by transition metal phosphides and opens new avenues for catalyst design.

Influence of Reduction Temperature on the Structure and Naphthalene Hydrogenation Saturation Performance of Ni2P/Al2O3 Catalysts

Jet fuel rich in hydroaromatics and cycloalkanes could be derived from direct coal liquefaction oil via the hydrogenation saturation process. Developing an efficient catalyst to transform naphthalene hydrocarbons to hydroaromatics and cycloalkanes with high selectivity plays a significant role in realizing the above hydrogenation saturation process. In this work, Ni2P/Al2O3 catalysts were prepared at different reduction temperatures via the thermal decomposition of hypophosphite. We investigated the influence of reduction temperature and the results showed that reduction temperature had an important impact on the properties of Ni2P/Al2O3 catalysts. When the reduction temperature was 400 °C, the Ni2P particle size of the Ni2P/Al2O3 catalyst was 3.8 nm and its specific surface area was 170 m2/g. Furthermore, the Ni2P/Al2O3 catalyst reduced at 400 °C obtained 98% naphthalene conversion and 98% decalin selectivity. The superior catalytic activity was attributed to the smaller Ni2P particle size, higher specific surface area and suitable acidity, which enhanced the adsorption of naphthalene on Ni2P/Al2O3 catalyst.

Naphthalene Hydrogenation Saturation over Ni2P/Al2O3 Catalysts Synthesized by Thermal Decomposition of Hypophosphite

A series of Ni₂P/Al₂O₃ catalysts with different Ni₂P loadings were synthesized via thermal decomposition of hypophosphite and employed for naphthalene hydrogenation saturation. Results showed that Ni₂P loading greatly affected Ni₂P particle size and the number of active sites of the as-synthesized catalysts, which was derived from the variable interaction between POx and Al₂O₃. When the hydrogenation saturation reaction was performed at 300 °C, 4 MPa, a H₂/oil volume ratio of 600, and a liquid hourly space velocity (LHSV) of 3 h^-1, 98% naphthalene conversion and 98% selectivity to decalin were achieved over Ni₂P/Al₂O₃ catalysts with 10 wt % Ni₂P. The superior naphthalene hydrogenation saturation performance was ascribed to the large specific surface area (169 m²·g^-1), small Ni₂P particle size (3.8 nm), and the high number of exposed active sites (CO sorption 30 μmol·g^-1), which were beneficial to the adsorption and diffusion of the reactant molecules on the catalyst.

Preparation and Catalytic Performance of Metal-Rich Pd Phosphides for the Solvent-Free Selective Hydrogenation of Chloronitrobenzene

A facile synthesis method of palladium phosphide supported on the activated carbon was developed. The effects of Pd precursors for phosphatization, phosphatization temperature, and the ratio of hypophosphite/Pd on the generation of palladium phosphide were investigated, and a generation mechanism of the Pd3P crystal structure is proposed. The results demonstrate that only PdO, rather than Pd or PdCl2, can transform into Pd phosphide without damage to the activated carbon. The penetration of P into the Pd particle can dramatically improve the dispersion of Pd species particles on the activated carbon. The generation of Pd phosphide greatly depends on the phosphatization temperature and the ratio of hypophosphite/Pd. An intact Pd3P crystal structure was obtained when the ratio of hypophosphite/Pd reached 32 and the phosphatization temperature was above 400 °C. The Pd3P supported on the activated carbon exhibited superior catalytic performance in terms of the hydrogenation of halonitrobenzenes to haloanilines because it had few L acids and B acids sites and could not generate deficient-electron active hydrogen atoms as electrophiles.