Increasing Mo Loading Research Articles

The relationship between structure and performance of Mo-ZrO2 catalysts in CO2 hydrogenation

CO₂ hydrogenation is a structure-sensitive reaction, producing a diverse range of products based on the structure of catalysts. In this study, we present a catalyst Mo-ZrO2 for CO2 hydrogenation and observed the products vary among CO, CH4, and CH3OH as Mo changes in its loading and local environment. Kinetic studies reveal that increasing Mo loading amplifies hydrogenation ability of the catalyst while simultaneously reducing CO2 adsorption on ZrO2. Specifically, Mo loadings under 10 wt% result in Mo integration into ZrO2 support, forming a Mo-O-Zr structure. Conversely, a higher Mo loading leads to the formation of Zr(MoO4)2 clusters on ZrO2 support. The Mo5⁺-Ov-Zr structure, formed in Mo-doped ZrO2 during reduction pretreatment, emerges as an active site for methanol synthesis. In contrast, metallic Mo formed from the reduction of Zr(MoO4)2 clusters loaded on ZrO2 is responsible for methane formation. The evolution of the surface structure from Mo-O-Zr structure to Zr(MoO4)2 clusters on ZrO2 as Mo loading changes, resulting in alterations in the number of active sites for methanol synthesis and methanation, consequently leading to variations in product distribution.

Observed reduction in fracture toughness of AlN and AlN–Mo ceramic matrix composites with carbon additive

The fracture toughness of AlN ceramic matrix composites containing carbon (0.5 vol%), yttria (5.0 vol%), and Mo (0.0–4.0 vol%) was evaluated using Vickers indentation. The results of these measurements were compared to a carbon-free, commercial AlN (ST-200 ALN) as well as to AlN and AlN–Mo compositions from the literature. The presence of added carbon was found to correlate with a 21% reduction in fracture toughness of the 0.0 vol% Mo carbon-containing sample, compared to commercial ST-200 AlN, in both the A-orientation (indentation parallel to the pressing direction) and the B-orientation (indentation perpendicular to the pressing direction). Mo additions at small loading fractions (~ 0.25 vol%) were found to exhibit greater-than-expected increases in fracture toughness in the A-orientation, when compared to literature data on AlN–Mo composites. This increase in fracture toughness correlates to the removal of elemental carbon in the AlN matrix through reaction with the Mo additive, forming Mo2C, localized at the Mo particle sites. Further increasing Mo loading was observed to result in generally increasing fracture toughness values, as would be expected from literature data.Graphical abstract

Biodiesel production by transesterification of waste cooking oil in the presence of graphitic carbon nitride supported molybdenum catalyst

Development of the active metal species with high utilization and accessibility of oil macromoleculars is one of the critical factors affecting heterogeneous metal-based catalysts for production of biodiesel. Here, we synthesized two-dimensional graphitic carbon nitride supported molybdenum (xMo/g-C3N4) catalysts for the facile transesterification of waste cooking soybean oil. Various characterization results of these catalysts show the crystal structure of g-C3N4 is not destroyed, however, Mo oxides phase, containing Mo6+ and Mo5+ state, is detected on the surface of the Mo/g-C3N4 with much Mo-loading, and the ratio of Mo6+/Mo5+ increases significantly with the increasing Mo loading. As expected, compared with the neat g-C3N4 catalyst, the g-C3N4 supported Mo catalyst exhibits a better catalytic performance; especially the 10%Mo/g-C3N4 catalyst has the optimal waste cooking soybean oil conversion of 71.1% and biodiesel selectivity of 99.5%. Furthermore, the experimental parameters and catalytic reusability for the transesterification reaction over 10%Mo/g-C3N4 catalyst are investigated. Moreover, the possible deactivation mechanism and regeneration method of as-prepared catalyst are also proposed. This work provides a valuable tactics for the production of clean and low-cost biodiesel from waste cooking soybean oil in the presence of efficient solid catalyst.

Understanding selectivity changes during hydrodesulfurization of dibenzothiophene on Mo2C/carbon catalysts

The activity and stability of Mo2C supported on an activated carbon derived from petroleum coke (Mo2C/APC), is reported for the hydrodesulfurization (HDS) of dibenzothiophene (DBT). Mo2C/APC catalysts with Mo loading of 2%, 5%, and 10% were synthesized by carbothermal hydrogen reduction (CHR). XPS analysis of the fresh catalysts indicated ∼65% of Mo species were present as Mo carbide or oxycarbide, invariant with Mo loading; whereas, Mo2C particle size increased from 6.1 nm to 10.3 nm with increased Mo loading. The initial turnover frequency (TOF) for the HDS of DBT increased marginally with increased Mo2C particle size but DBT conversion declined rapidly with time-one-stream. A corresponding change in selectivity from >60% hydrogenation products (cyclohexylbenzene and bicyclohexane) to >70% biphenyl, the direct desulfurization product, also occurred. Characterization of the used catalysts showed the presence of MoS2 overlayers and an increase in Mo2C particle size, compared to the fresh catalysts. Density functional theory calculations were used to assess the impact of S on the Mo2C surface and the DBT adsorption geometry, showing that S enhances vertical DBT adsorption and consequently selectivity to the direct desulfurization product, biphenyl.

Effect of Mo-Doped Mesoporous Al-SSP Catalysts for the Catalytic Dehydration of Ethanol to Ethylene

The catalytic dehydration of ethanol to ethylene over the mesoporous Al-SSP and Mo-doped Al-SSP catalysts was investigated. The Al-SSP catalyst was first synthesized by the modified sol-gel method and then doped with Mo by impregnation to obtain 1% Mo/Al-SSP and 5% Mo/Al-SSP catalysts (1 and 5 wt% of Mo). The final catalysts were characterized using various techniques such as XRD, N2physisorption, SEM/EDX, TEM, and NH3-TPD. The catalytic activity for all catalysts in gas-phase ethanol dehydration reaction was determined at temperature range of 200°C to 400°C. It was found that the most crucial factor influencing the catalytic activities appears to be the acidity. The acid property of catalysts depended on the amount of Mo loading. Increased Mo loading in Al-SSP resulted in increased weak acid sites, which enhanced the catalytic activity. Besides acidity, the high concentration of Al at surface of catalyst is also essential to obtain high activity. Based on the results, the most suitable catalyst in this study is 1% Mo/Al-SSP catalyst, which can produce ethylene yield of ca. 90% at 300°C with slight amounts of diethyl ether (DEE) and acetaldehyde.

PREPARATION OF HIGHLY ACTIVE Co-Mo/Al<sub>2</sub>O<sub>3</sub> HDS CATALYSTS WITH CITRIC ACID ADDITION BY THE POST-TREATMENT METHOD

A study of the influence of citric acid (CA) addition by a post-treatment method during the preparation of a series of Mo/Al2O3 catalysts on the thiophene HDS activity was conducted. The Mo/Al2O3 catalysts were also prepared by a chemical vapor deposition (CVD) technique using Co(CO)3NO to introduce Co atom and characterized by means of NO adsorption, XRD, Mo K-edge EXAFS and XRF. With 8.7 wt% Mo, citric acid was not affected very much for the Co-Mo/Al2O3 catalysts. On the other hand, an outstanding result was shown that the HDS activity was drastically enhanced by 5 times up to Mo content around of 25 wt% Mo. It is suggested that the post treatment increased the dispersion of MoS2 particles, in particular at a high Mo loading. This was also supported by the amount of NO adsorption and amount of Co anchored by the CVD results, which enhanced as the increasing Mo loading up to 25 wt% Mo. Moreover, Mo-CA complex species were observed on the post-treatment method and CVD technique was one of advanced method to prepare Co-Mo-S phases selectively.

Comparative study of molybdenum oxide in NaY zeolite prepared by conventional impregnation and vapor-phase deposition techniques

The interaction between Mo (2–30 wt.% expressed as MoO 3) and NaY zeolite lattice by applying conventional impregnation with aqueous (NH 4) 6Mo 7O 24 · 4H 2O (AHM) and vapor-phase deposition of volatile complex Mo(CO) 6 has been compared. The samples were characterized by FTIR spectroscopy, X-ray diffraction and in situ FTIR of pyridine adsorption. Their pore structure and surface were analyzed with nitrogen adsorption measurements at 77 K. The results showed that Mo species derived from AHM interact with framework aluminum of NaY, and the interaction overlaps so strong with increasing Mo loading above an equivalent monolayer. A new Al 2(MoO 4) 3 phase was developed due to continued dealumination of zeolite, leading to intense collapse of the crystalline structure and drastically reducing its adsorption capacity. Alternatively, a decarbonylation process owing to dissociative adsorption of Mo(CO) 6 into dehydrated zeolite in vacuo at 353 K with concurrent evolution of CO gas was occurred. Therefore, weak structural features of adsorbed CO 3 2 - (1453 cm −1) and HCO 3 - (656 cm −1) species were observed. It was suggested that a molybdenum monomer subcarbonyl species get built into the zeolite via coordination by two or three oxygen atoms of zeolite framework. Subsequent exposure to air produced a high-dispersed tetrahedral monomeric MoO x (895 cm −1) species in zeolite. The dispersed state of MoO x species measured the highest specific surface area and unit cell parameter. These results were utilized to derive relationships between solid structures and acid properties. The MoO x surface species in NaY served in new formed Brönsted acid sites. These sites have higher acid strength than the original ones in the zeolite and those in analogous samples prepared by impregnating zeolite with AHM.

A high-resolution MAS NMR study on the potential catalysts Mo/HBeta for olefin metathesis: The interaction of Mo species with HBeta zeolite

The interfacial interaction of Mo species with the HBeta zeolite was studied by multinuclear MAS NMR, XRD and N 2 adsorption. As proved by the quantitative 27Al MAS NMR, this interaction is so strong as to dealuminate the framework of HBeta, and leads to a new peak appearing at −14 ppm, which indicates the formation of crystalline Al 2(MoO 4) 3. This can also be detected by XRD measurements when the Mo loading is as high as 9.0 wt.%. The corresponding quantitative 29Si and 1H MAS NMR spectra show that the amount of silanols and Brønsted acidic sites decrease obviously with increasing Mo loading. This also reveals an interaction between Mo species and HBeta support through an oxygen bridge resulting from condensation with the hydroxyls on the support. At higher Mo loadings, the interaction is so strong that it results in an extraction of aluminum from the zeolite framework, and subsequently appearance of Al 2(MoO 4) 3 and loss of Brønsted acidic sites. These can be correlated to the low catalytic activity of Mo/HBeta in metathesis of ethylene and 2-butylene to propylene.

Structure and acidity of Mo/H-MCM-22 catalysts studied by NMR spectroscopy

A comprehensive study on physical and chemical properties of Mo/MCM-22 bifunctional catalysts has been made by using combined analytic and spectroscopic techniques, such as adsorption, elemental analysis, and 129Xe and 31P NMR of adsorbed trialkylphosphine oxide probe molecules. Samples prepared by the impregnation method with Mo loadings ranging from 2–10 wt.% have been examined and the results are compared with that obtained from samples prepared by mechanical mixing using MoO 3 or Mo 2C as agents. Sample calcination treatment is essential in achieving a well-dispersed metal species in Mo/MCM-22. It was found that, upon initial incorporation, the Mo species tend to inactivate both Brønsted and Lewis sites locate predominantly in the supercages rather than the 10-membered ring channels of MCM-22. However, as the Mo loading exceeds 6 wt.%, the excessive Mo species tend to migrate toward extracrystalline surfaces of the catalyst. A consistent decrease in concentrations of acid sites with increasing Mo loading <6 wt.% was found, especially for those with higher acid strengths. Upon loading of Mo > 6 wt.%, further decreases in both Brønsted and Lewis acidities were observed. These results provide crucial supports for interpreting the peculiar behaviors previously observed during the conversion of methane to benzene over Mo/MCM-22 catalyst under non-oxidative conditions, in which an optimal performance was achieved with a Mo loading of 6 wt.%. The effects of Mo incorporation on porosity and acidity features of the catalyst are discussed.

Characterization and reactivity of molybdenum oxide catalysts supported on Nb2O5–TiO2

A series of MoO3/Nb2O5 catalysts with Mo loadings varying from 2.5 to 15 wt % were prepared and characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of ammonia, electron spin resonance (ESR), oxygen chemisorption, and pore size distribution measurements. X-ray diffraction patterns indicate the presence of a crystalline molybdenum phase at higher Mo loadings on niobia. Dispersion of molybdenum was determined by the oxygen chemisorption at 623 K by a static method on the samples prereduced at the same temperature. At low Mo loadings, i.e., <10.0%, molybdenum oxide is found to be present in a highly dispersed state. Pore size distribution studies indicate a decrease in average pore diameter and pore volume with increased Mo loading. ESR results suggest the presence of Mo5+ in the reduced catalysts. TPR results suggest that the reducibility of MoO3 increases with increased Mo loading. The reduction peaks due to niobia in TPR appeared at high...

A DRIFTS study of Mo/alumina interaction: from Mo/boehmite solution to Mo/γAl 2O 3 support

With the aim of exploring an alternative way to prepare Mo/Al 2O 3 catalysts, we concentrate our attention on Mo/boehmite systems with particular reference to the molybdenum localization at the boehmite interface and its influence on the boehmite to γ-Al 2O 3 transformation. Several samples of boehmite at increasing Mo loading (0.02, 0.123 and 0.514 equivalent Mo/Al) have been synthesized and studied by means of diffuse reflectance infrared spectroscopy (DRIFTS), XRD and DTA–TGA.

Dispersion and reactivity of Mo/Nb2O5 catalysts in the ammoxidation of toluene to benzonitrile

A series of Mo/Nb2O5 catalysts were prepared with Mo loadings ranging from 2.5–15 wt% of Mo and characterized by X-ray diffraction (XRD), pulse oxygen chemisorption, temperature-programmed desoprtion of ammonia. Dispersion of molybdena was determined by oxygen chemisorption at 623 K in a dynamic method. At low Mo loadings molybdenum oxide is found to be present in a highly dispersed state. XRD results show the presence of crystalline MoO3 at higher Mo loadings (from 10 wt%). The dispersion of molybdena was found to decrease with increased Mo loading due to formation of MoO3. The catalytic properties were evaluated for the vapour phase ammoxidation of toluene to benzonitrile and are related to different characterization results.

Studies on physico-chemical characterization and catalysis on high surface area titania supported molybdenum hydrotreating catalysts

A series of titania supported molybdenum catalysts were prepared by incipient wetness impregnation method and characterized by BET surface area, XRD, TPR, FTIR, ESCA, and low temperature oxygen chemisorption. Thiophene, cyclohexene and tetrahydrofuran were taken as model compounds for evaluating catalytic activities for hydrodesulfurization (HDS), hydrogenation (HYD), and hydrodeoxygenation (HDO) reactions, respectively. XRD results indicate that molybdenum oxide species are dispersed as a monolayer on the support up to 8 wt.% Mo and the formation of crystalline MoO 3 is observed above this loading. FTIR and TPR results showed that molybdenum oxide species were present predominantly in tetrahedral form at lower loading and polymeric octahedral forms are dominant at higher loading. Both oxygen chemisorption and rates of reaction were found to increase with increasing Mo loading up to 8 wt.% and then decrease with further increase in loading. HDS and HYD activities are more or less same but HDO activity is two times higher than HDS and HYD activities. The results are also interpreted with the help of other parameters, like dispersion, equivalent molybdenum surface area, surface coverage, crystalline size, quasi-turnover frequencies and intrinsic activities. ESCA results suggest that electron transfer is taking place from support to metal.

Acidic properties of sulfated iron oxide supported molybdenum catalysts: a differential scanning calorimetry, thermogravimetry and Fourier transform-infrared study

Sulfated Fe 2O 3 catalysts impregnated with different molybdenum contents varied from 2 to 42 wt.%, were examined by temperature-programmed pyridine desorption via differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The acidity of these catalysts were investigated and compared with those corresponding to SO 4 2−/free Fe 2O 3 ones. Δ H values (obtained from DSC) and amounts of pyridine irreversibly adsorbed (obtained from TG) showed that the concentration of Lewis acid sites decreased with increasing Mo loading. On the other hand, the sulfated Fe 2O 3 supported Mo catalysts showed an increase in the concentration of acid sites to almost 10 times that of the corresponding SO 4 2−/free Fe 2O 3 catalysts. In addition, the enthalpies of pyridine desorption from SO 4 2−/Fe 2O 3 supported Mo catalysts were higher than those for the SO 4 2−/free Fe 2O 3 catalysts. This indicated the strength of acid sites on the former samples compared with those on the later ones. Comparative FT-IR spectroscopic analyses of pyridine adsorption have been investigated to study the nature of the acid sites and to assess the effect of SO 4 2− species on the surface acidity. It was found that the presence of SO 4 2− species enhanced the surface acidity and helped the formation of Brønsted sites earlier at the 2 wt.% Mo loading. These were manifested by the presence of vibrational bands at 1635 and 1540 cm −1. These bands were only detected at a loading of 5 wt.% Mo when the support was SO 4 2−/free Fe 2O 3. Important correlations and shifts in the IR absorption bands were evaluated and discussed.

Methane Dehydro-aromatization over Mo/HZSM-5 in the Absence of Oxygen: A Multinuclear Solid-State NMR Study of the Interaction between Supported Mo Species and HZSM-5 Zeolite with Different Crystal Sizes

The interaction between Mo species and a conventionally microsized and particularly nanosized HZSM-5 support was studied by high-resolution multinuclear solid-state NMR techniques. As proved by 27Al and 29Si MAS as well as CP/MAS NMR investigations, this interaction was so strong that the framework aluminum of both microsized and nanosized HZSM-5 zeolites could be extracted. With increasing Mo loading, more nonframework aluminum, resonanced at ca. 30 ppm, appeared in the 27Al MAS NMR spectrum of the Mo-loaded nanosized HZSM-5 catalyst. Meanwhile, this strong interaction led to the formation of more new Al2(MoO4)3 crystallines on the nanosized HZSM-5 support than on the microsized HZSM-5 support. The appearance of Al2(MoO4)3 crystallines resulted in fewer active catalysts for the methane dehyro-aromatization. The results of 1H MAS NMR using perfluorotributyl amine as a probe molecule demonstrated that Mo species preferentially reacted with the silanols and nonframework AlOH on the external surface of microsized and nanosized HZSM-5 zeolites. In addition, impregnated Mo species remained predominantly on the external surface of the nanosized HZSM-5 zeolite, although there was a possibility that they might migrate into the lattice channels of the microsized HZSM-5 zeolite. The migration of some Mo species into the zeolite channels might be beneficial for the conversion of methane to aromatics in the absence of oxygen.

High temperature calcined K–MoO 3/γ-Al 2O 3 catalysts for mixed alcohols synthesis from syngas: Effects of Mo loadings

One series of oxidized K–MoO 3/γ-Al 2O 3 samples with different Mo loadings (MoO 3/Al 2O 3 (wt ratio)=0.05–0.45) was prepared by impregnating K and Mo compounds and successive calcination in air at 800°C. The oxidized samples were sulfided and then utilized for mixed alcohols synthesis from syngas. The structural information from laser Raman spectroscopy (LRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ammonia saturation, temperature programmed desorption (TPD) and ethanol decomposition were studied to elucidate the reaction properties. The results indicated that with Mo loading increased from MoO 3/Al 2O 3=0.05 to 0.25, the total yields of mixed alcohols and hydrocarbons decreased, but the selectivity to mixed alcohols was enhanced sharply from 3% to 50%. With Mo loading increased from MoO 3/Al 2O 3=0.25 to 0.45, the CO conversion was enhanced, but the selectivity to mixed alcohols leveled off. On these catalysts, Fischer–Tropsch (FT) synthesis to linear alcohols and the condensation reaction of low alcohols to form branched i-C 4OH occurred at the same time. With increased Mo loading, activity of the alcohols condensation became high. Structural studies demonstrated that on oxidized samples with increased Mo loading the same K–Mo–O species was formed, but the dispersion of these K–Mo species decreased. The catalyst's acidity decreased remarkably with Mo loading up to MoO 3/Al 2O 3=0.25, and stayed unchanged as Mo loading was further increased to MoO 3/Al 2O 3=0.45. With increased Mo loading, the activity for ethanol dehydration changed parallel to the acidity. Results of the activity experiments for mixed alcohols' synthesis and the structural measurements indicated that the dispersion state of Mo species and the content of unreduced Mo species influenced the total CO conversion, and that the acidity of the catalyst controlled the selectivity to mixed alcohols.

Determination of the surface coverage of Mo/TiO2 catalysts by ISS and CO2 chemisorption

A series of Mo/TiO 2 catalysts was prepared by equilibrium adsorption from aqueous solutions of (NH 4 ) 6 Mo 7 O 24 by varying the pH of the solution from 9.8 to 4. The Mo loading increases from 0.8 to 3.6 wt.% as the pH of preparation decreases. The surface coverage of the calcined catalysts was monitored by CO 2 chemisorption and ion scattering spectroscopy (ISS) measurements. Carbon dioxide uptake was determined in a standard BET system from the adsorption isotherms by extrapolating to zero pressure. Coverage measurements from ISS were obtained by monitoring the changes of the ISS Ti signal with Mo addition. Additional information about the dispersion of the Mo phase of these catalysts was obtained from x-ray photoelectron spectroscopy (XPS) measurements The XPS results evidenced the presence of a highly dispersed Mo phase. Carbon dioxide chemisorption results for Mo/TiO 2 catalysts indicated that the Mo coverage increases linearly from 0.16 to 0.93 with increasing Mo loading from 0.6 to 3.6 wt.%. These results were consistent with those determined by ISS measurements and are in good agreement with the predicted values for monolayer dispersion. These findings are in contrast with those obtained for alumina-supported catalysts, where the CO 2 chemisorption method has been show to overestimate the surface coverage. The origin of the apparent suitability of the CO 2 chemisorption method for monitoring the surface coverage of TiO 2 -based systems is discussed.

Methane dehydrogenation and aromatization in the absence of oxygen on [formula omitted]: A study on the interaction between Mo species and HZSM-5 by using 27Al and 29Si MAS NMR

By using a high-resolution solid state nuclear magnetic resonance spectrometer with 27Al and 29Si probes, the interaction between Mo species and HZSM-5 of frsol|Mo/HZSM-5 catalysts has been studied. The results show that there is a strong interaction between Mo species and HZSM-5 zeolite. The framework aluminum in the zeolite can be easily extracted by the introduction of Mo species. The extractability of framework aluminum by Mo species increases with increasing Mo loading and the calcination temperature. The extraction process leads to the formation of non-framework Al at first and then a new crystalline phase of Al 2(MoO 4) 3. The dealumination of the catalyst having a Mo loading of 15% and had been calcined at 973 K is so severe that all the aluminum in the framework are extracted and no framework Al could be detected by 27Al MAS NMR. The catalyst, therefore, lost its catalytic activity for methane dehydrogenation and aromatization in the absence of oxygen. The Si Al ratio measured from 29Si MAS NMR further confirms the dealumination process observed by 27Al MAS NMR. The MAS NMR results give us an evidence that Al 2(MoO 4) 3 crystallites are much less active for the reaction.

Study Mo/HZSM-5 Catalysts by NMR

By using high-resolution solid state Nuclear Magnetic Resonance spectrometer with Al-27 and Si-29 probes, the interaction between Mo species and HZSM-5 of Mo/HZSM-5 catalysts has been studied. The results show that there is a strong interaction between Mo species and HZSM-5 zeolite. The framework aluminium in the zeolite can be easily extracted by the introduction of Mo species. The extract ability of framework aluminium by Mo species increases with increasing Mo loading and the calcination temperature. The extraction process leads to the formation of non-framework Al at first and then a new crystalline phase of Al-2(MoO4)(3). The catalyst, therefore, lost its catalytic activity for methane dehydrogenation and aromatization in the absence of oxygen. The MAS NMR results give us an evidence that Al-2(MoO4)(3) crystallites are much less active for the reaction.

NaY-Supported Molybdenum Sulfide Catalysts: I. Catalysts Prepared via Impregnation with Ammonium Heptamolybdate

NaY-supported molybdenum sulfide catalysts with increasing Mo loading have been prepared by impregnation with ammonium heptamolybdate and characterized by means of thiophene hydrodesulfurization (HDS), overall sulfur analysis, temperature programmed sulfidation, N2adsorption, Xe adsorption,129Xe-NMR, and high resolution electron microscopy. After impregnation nearly all Mo is located on the exterior of the zeolite particles. During calcination in air part of the Mo is redistributed, resulting in a higher amount of Mo being located in the zeolite supercages. For the sulfided catalysts an amount of Mo comparable to that after calcination is present in the supercages. At the highest Mo loadings the catalysts are incompletely sulfided, due to the presence of large “bulk-like” molybdenum oxide particles on the outside of the zeolite particles. The amount of Mo present in the supercages, as well as the thiophene HDS activity of the sulfided catalysts, increases with increasing Mo loading. The small Mo sulfide particles in the supercages contribute strongly to the thiophene HDS activity.