Effect of Boron Addition on the State and Dispersion of Mo Supported on Alumina

Abstract

The influence of B on the state and dispersion of Mo phases on A1203 have been investigated by bulk and surface characterization techniques, e.g., XRD, XPS and TPR, respectively. In the absence of B, the dispersion of Mo phases Is in good agreement with the theoretical value calculated from Kerkhof-Moulijn model, suggesting that Mo atoms disperse easily on A1203 surface. XPS results indicate that B addition to A1203 leads the Mo dispersion to decrease in comparison with the theoretical mondayer value. This result is also confirmed by XRD analysis, which shows the formation of crystalline Moo3 particles with B addition. TPR profiles for Mo/A1203 consists of two reduction peaks, a low temperature peak (400°C-4500C) and a high temperature one (77OoC-810"C), respectively. The peak intensity of the higher temperature decreases rapidly with B addition, whereas that of lower temperature increases wi.h increasing B contents. Consequently, these results suggest that B addition weakens the interaction between Mo species and the A1203 surface. INTRODUCTIONCatalysts based on molybdenum or tungsten sulfide and promoted by nickel and/or cobalt have been used extensively for hydrotreating in petroleum refining such as hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodemezallization (HDM) for many years. Many studies have been focused on both elucidation of the structure of active phases and enhancement of HDS, HDN and HDM activities.The chemistry and structure of CoMolAlnOs catalysts have been well studied. Several models have been proposed to describe the interactlon between Mo and Co species. These models include the mondayer model [ l , 21, Co-Mo-S complex model [3-51, intercalation model [6] and contact synergy (remote control) model [7]. Recently, the Co-Mo-S model is generally believed as the active structure for the CoMolAlnOs catalysts.In order to take advantage of the relatively high surface area of Al203, a number of studies have been carried out in which the A203 support was modified by such oxides, e.g., MgO [8]

Hydrodesulfurization Properties of Nickel Phosphide on Boron‐treated Alumina Supports

“…The Al(2p) peak is observed in all spectra, and the measured binding energies (73.7–74.0 eV) are in the expected range for γ‐Al 2 O 3 . The B(1s) peak grows in intensity with increasing B loading and its binding energy (192.2–192.5 eV) is close to the value for interfacial aluminum borate (9Al 2 O 3 ⋅ 2B 2 O 3 ) of 192.5 eV, which is below the binding energy of bulk B 2 O 3 (193.5 eV), and nearly identical to values reported for a B 2 O 3 surface layer on γ‐Al 2 O 3 . The B(1s)/Al(2p) peak area ratio increases linearly with increasing B loading up to ∼4.7 wt % B, beyond which the peak area ratio increases more slowly.…”

“…[24] The B(1s) peak grows in intensity with increasing B loading and its binding energy (192.2-192.5 eV) is close to the value for interfacial aluminum borate (9Al 2 O 3 • 2B 2 O 3 ) of 192.5 eV, [25] which is below the binding energy of bulk B 2 O 3 (193.5 eV [25] ), and nearly identical to values reported for a B 2 O 3 surface layer on γ-Al 2 O 3 . [21,[25][26][27] The B(1s)/Al(2p) peak area ratio increases linearly with increasing B loading up to~4.7 wt % B, beyond which the peak area ratio increases more slowly. These results are consistent with previous XPS studies, [21,[25][26] and indicate the growth of well dispersed B 2 O 3 species on the γ-Al 2 O 3 support up to monolayer coverage.…”

“…[21,[25][26][27] The B(1s)/Al(2p) peak area ratio increases linearly with increasing B loading up to~4.7 wt % B, beyond which the peak area ratio increases more slowly. These results are consistent with previous XPS studies, [21,[25][26] and indicate the growth of well dispersed B 2 O 3 species on the γ-Al 2 O 3 support up to monolayer coverage. A calculation of the theoretical monolayer coverage using a B 2 O 3 cross-sectional area of (0.17 nm 2 /molecule [28] ) yields a loading of 4.3 wt % B (see Supporting Information), which is in good agreement with the value determined by XPS.…”

Effect of Preparation Methods and Content of Boron on Hydrotreating Catalytic Activity

“…Usman et al reported that boron may change low active Co–Mo–S type I sites to high Co–Mo–S type II sites. On the other hand, Morishige and Akai reported that boron decreases dispersion of molybdenum on an alumina support.…”

Hidrodesulfuración del dibenzotiofeno y 4,6-dimetildibenzotiofeno sobre catalizadores NiMo, CoMo y NiW en estado sulfuro soportados en alúmina: efecto del galio como aditivo

“…89,[115][116][117][118] El boro ha sido uno de los aditivos más investigados. Los resultados más aceptados indican que un efecto positivo sobre la dispersión del molibdeno, 119,120 así como sobre propiedades ácidas del soporte. [121][122][123][124] El efecto del boro sobre la actividad de los catalizadores NiMo y CoMo, al igual que los cationes antes presentados, es controvertido.…”