Preparation, Characterization, and Performance of Alumina-Supported Nanostructured Mo−Phosphide Systems

Abstract

Al 2 O 3 -supported molybdenum phosphide catalysts containing fixed Mo-loading (9.9 wt %) and variable P amounts (1.5-9.6 wt %) were prepared by temperature-programmed reduction (TPR) from their oxide precursors in hydrogen. The effect of the P/Mo atomic ratio on the structure of the molybdenum phosphide materials was studied by S BET , XRD, HRTEM, TPD-NH 3 , H 2 chemisorption, XPS, and 31 P-and 27 Al-MAS NMR techniques. The reactions involved in the transformation of oxide precursor to Mo-phosphide were followed by TPR. Specific surface areas of samples subjected to reduction at 1123 K were rather high (210-263 m 2 g -1 ). These catalysts were tested in the gas-phase hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 553 K and 3.4 MPa. All Mo-phosphide catalysts were more active than a molybdenum sulfide sample with the same Mo-loading. The Mophosphide catalysts with P/Mo ratios of 1 and 1.1 were found to be the most active among the catalysts studied. The activity drop observed for higher P-loadings runs in parallel with the drop in specific areas. Moreover, the XPS and electrons diffraction analyses revealed the formation of MoP phase in all samples and the appearance of polyphosphates and AlPO 4 phases in P-rich ones. For the P-rich samples, the EFTEM study indicated that phosphate is accumulated around Mo atoms. It was found that the H 2 chemisorption capacity of the samples reduced at 1123 K correlates with the HDS performance of the catalysts.

Selective Hydrogenation of Acetylene over a MoP Catalyst

“…The Mo 3d 5/2 peak positions for the catalyst is located at electron binding energies of about 228.0, 229.1, and 232.2 eV, and these are with the same as those of Mo 3+ , Mo + , and Mo 6+ in a multiphase environment. These results are in agreement with previously reported results [10]. Additionally, the P 2p 3/2 peaks were at 129.2 and 133.4 eV, which is with the same as that for the P 3 and P 5+ species, and this is also in agreement with a previous report [11].…”

MoP/Al2O3 as a novel catalyst for sulfur‐resistant methanation

“…Moreover, a sharp diffraction peak at 26.6° can be observed in all samples, which is attributed to AlPO 4 phase (JCPDS 31–0029). It demonstrates that the formation of AlPO 4 phase is due to the strong interaction between Al 2 O 3 support and phosphate, which is consistent with the previous literature . And, the diffraction peak for AlPO 4 phase becomes stronger and sharper with the reduction temperature increased.…”

“…It demonstrates that the formation of AlPO 4 phase is due to the strong interaction between Al 2 O 3 support and phosphate, which is consistent with the previous literature. [22] And, the diffraction peak for AlPO 4 phase becomes stronger and sharper with the reduction temperature increased. Hence, phosphates are more prone to be crystallized at high temperature.…”

Dehydrogenation of methylcyclohexane to toluene over partially reduced Mo–SiO2 catalysts

“…The Mo 3d core-level spectra of the spent catalysts are shown in Figure 7(B). For both Mo10-SiO 2 and Mo15-SiO 2 , the deconvolution of the Mo 3d spectra reveals two doublets ( [49]. For the Mo5 sample (Table 3) For all the samples, the Mo/Si surface ratio is lower than the Mo/Si nominal ratio (Table 3).…”