Enhancement of fatty acids hydrodeoxygenation selectivity to diesel-range alkanes over the supported Ni-MoOx catalyst and elucidation of the active phase

Mineral Montmorillonite Valorization by Developing Ni and Mo–Ni Catalysts for Third-Generation Green Diesel Production

“…The comparison of the present results with current literature results in the domain of the SDO of triglycerides and related compounds over nickel catalysts clearly revealed that the catalytic behavior of nickel species supported on mineral montmorillonite was similar to that exhibited over synthetic supports such as γ-alumina [ 20 , 21 , 49 , 50 , 51 , 63 ], silica [ 52 , 53 , 56 , 57 , 60 ], zirconia [ 88 ], ceria [ 64 ], zeolites [ 54 , 58 , 59 , 63 ], active carbons [ 62 , 63 ] and mineral palygorskite [ 66 , 67 ], from the viewpoint of the SDO network. Moreover, the catalytic efficiency obtained in the present study over nickel species supported on post-treated mineral montmorillonite was comparable to those obtained over nickel species supported on synthetic supports, though a rigorous comparison is very difficult to achieve due to the quite different evaluation conditions adopted in each case.…”

“…Moreover, the SEM–EDX mapping of the nickel and molybdenum showed that the nickel and molybdenum species are located very close together, at least at the microscale ( Figure 8 ). Based on the above, and taking into account the relevant literature [ 20 , 49 , 53 ], it seems that the Mo promoting action can be mainly attributed to the synergy between the oxygen vacancies situated on the surface of the molybdenum oxides and the neighboring metallic nickel sites. The intermediate fatty acids are adsorbed on the oxygen vacancies through the hydroxylic oxygen of the C-OH group.…”

“…The above results indicated that a loading of 20 wt.% Ni was quite sufficient for a Ni catalyst supported on montmorillonite, for SDO of WCO under solvent-free conditions. Based on this finding and on the relevant literature [ 20 , 21 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 ], a catalyst containing 20 wt.% Ni and 2 wt.% Mo co-deposited on the montmorillonite surface was also synthesized and studied. In this catalyst the atomic ratio was equal to 0.94, which is considered very suitable according to the literature [ 20 , 21 , 49 , 50 , 52 , 55 , 56 , 59 , 62 , 63 ].…”

“…Several methodologies have been developed to minimize these problems involving the use of suitable supports, nickel loading, preparation methods and optimized experimental conditions (mainly reaction temperature and hydrogen pressure) [ 11 ], as well as modification of the structure of the supported nickel through development of nickel phosphide [ 44 , 45 , 46 ], nitride [ 47 , 48 ] or carbide catalysts [ 32 , 48 ]. Another very promising prospect for overcoming the above drawbacks and further increasing the efficiency of nickel catalysts is the use of promoters, among which molybdenum oxides are the most effective [ 20 , 21 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. The literature survey indicated that excellent promoting action is observed in molybdenum oxides, mainly for catalysts with a Ni/(Ni+Mo) atomic ratio close to 0.85–0.95 [ 20 , 21 , 49 , 50 , 52 , 55 , 56 , 59 , 62 , 63 ].…”

“…Both the unpromoted and promoted nickel catalysts used to date for green diesel production are usually supported on synthetic supports (γ-alumina, silica, silica–alumina, synthetic zeolites, active carbons, carbon nanotubes, zirconia, titania, ceria, etc. [ 11 , 20 , 21 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 ]). Studies using cheap minerals as natural supports are very scarce [ 65 , 66 , 67 ].…”