Requirements for improved catalytic formulations is continuously driving researchi nh ydrotreating (HDT)c atalysis for biomass upgrading and heteroatom removalf or cleanerf uels. The present work proposes as urface-science approach for the understanding of the genesis of the active (sulfide) phase in model P-doped MoS 2 hydrotreating catalysts supported on a-Al 2 O 3 single crystals. This approach allows one to obtain as urface-dependenti nsightb yv arying the crystal orientationso ft he support. Model phosphorusdoped catalysts are preparedv ia spin-coating of MoP precursor solutions onto four a-Al 2 O 3 crystalo rientations, C(0001), A(112 0), M(101 0) and R(11 02) that exhibit different speciations of surface-OH. 31 Pa nd 95 Mo liquid-state NMR are used to give ac omprehensive description of the Mo andP speciation of the phospho-molybdic precursor solution. The speciation of the deposition solution is then correlatedw ith the genesiso ft he active MoS 2 phase.X PS quantificationo f the surfaceP /Mo ratio reveal as urface-dependent phosphate aggregation driven by the amount of free phosphates in solution.P hosphates aggregation decreases in the following order C(0001) @ M(101 0) > A(112 0), R(11 02). This evolution can be rationalized by an increasing strength of phosphate/surface interactions on the different a-Al 2 O 3 surface orientations from the C(0001) to the R(11 02) plane. Retardation of the sulfidation with temperature is observed for model catalystsw ith the highest phosphate dispersion on the surface(A(112 0), R(11 02)), suggesting that phosphorus strongly intervene in the genesis of the activep hase through ac lose intimacy between phosphates and molybdates.T he surface P/Mo ratio appears as ak ey descriptor to quantify this retarding effect.I ti sp roposedt hat retardation of sulfidation is drivenb yt wo effects:i)achemicali nhibition through formation of hardly reducible mixed molybdo-phosphates tructures and ii)a physicali nhibition with phosphate clusters inhibiting the growth of MoS 2 .T he surface-dependent phosphorus dopingo nm odel a-Al 2 O 3 supportsc an be used as ag uide for the rational design of more efficient HDT catalysts on industrial g-Al 2 O 3 carrier.

Environmental regulations concerning fuel‐related sulfur emissions are currently experiencing worldwide expansion. This is motivating the research and development of improved hydrotreating (HDT) catalysts with carefully engineered synthesis methods that maximize activity as ultimate goal. In this contribution, the effect of phosphorus doping and triethylene glycol (TEG) incorporation on the genesis of the CoMoS phase of model HDT catalysts is assessed. Following a surface‐science approach, α‐Al2O3 single crystals with four orientations: C(0001), A(11true2‾ 0), M(10true1‾ 0), and R(1true1‾ 02) are used as model supports of the traditional γ‐Al2O3 support for the study of active phase‐support interactions at the molecular scale. The model catalysts are prepared by traditional impregnation of a solution containing metal and phosphorus precursors and TEG. The catalysts are characterized in the sulfide phase by XPS, XAS, TEM, and AFM, revealing that the calcination step is key in the emergence of distinctive metal‐support interactions, which are directly related to the nature of alumina surface sorption sites. In addition, TEG incorporation on dried catalysts increases metal sulfidation and enhances promotion with respect to non‐additivated systems, especially at mild sulfidation temperatures. The catalytic activity of the model catalysts is tested in a thiophene hydrodesulfurization reaction, revealing the following activity trend with respect to alumina surface orientations: A()112‾0 ≫ M()101‾0 >R()11‾02 , C(0001). This trend is identical to the one observed for non‐phosphorus doped non‐TEG additivated model systems, confirming the predominance of surface effects on the catalytic activity over those exerted by P and TEG. By transposing these results to the industrial γ‐Al2O3 support, the (100) facet would provide surface sites that lead to better performing catalysts. This could result in the development of novel supports, engineered to expose surface sites that maximize hydrotreating activity.