Subscriber access provided by Kaohsiung Medical University
Catalysis and Kinetics
Bifunctional MoS2-Silica-Alumina Catalysts for Slurry Phase Phenanthrene-Decalin Hydroconversion Juliana Sanchez, Andres Moreno, Fanor Mondragon, and Kevin J. Smith Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b02770 • Publication Date (Web): 18 Sep 2018 Downloaded from http://pubs.acs.org on September 25, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
Bifunctional MoS2-Silica-Alumina Catalysts for Slurry Phase Phenanthrene-Decalin Hydroconversion Juliana Sánchez,a Andrés Moreno,a Fanor Mondragón,a Kevin J. Smith b* a
Química de Recursos Energéticos y Medio Ambiente, Instituto de Química, Facultad de
Ciencias Exactas y Naturales, Universidad de Antioquia, UdeA - Colombia, Calle 70 No. 52-21, Medellín, Antioquia 050010, Colombia. b
Department of Chemical and Biological Engineering, University of British Columbia,
Vancouver, British Columbia V6T 1Z3, Canada. KEYWORDS: MoS2, oil-dispersed catalyst, in situ, amorphous silica-alumina, slurry-phase hydroconversion, phenanthrene, decalin. ABSTRACT MoS2-amorphous silica-alumina (MoS2-ASA) bifunctional catalyst for slurry-phase hydroconversion of the model reactants phenanthrene and decalin, were prepared using three distinct methodologies. The MoS2-ASA catalysts were prepared by: (i) a mechanical mixture of MoS2 (prepared separately) and ASA which were mixed directly in the reactor for the hydroconversion test (MM catalyst); (ii) in situ sulfidation of the molybdenum 1 ACS Paragon Plus Environment
Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 41
precursor in the presence of the ASA, both dispersed in the phenanthrene-decalin reaction mixture (IS catalysts) and (iii) impregnation of molybdenum octoate onto ASA, followed by thermal treatment to chemically link the Mo precursor to the ASA surface followed by sulfidation prior to the catalytic test (IMP catalyst). Among the three preparation methods, the MoS2-ASA catalysts prepared in situ (IS) had the highest MoS2 dispersion, degree of sulfidation and yielded the highest hydrogenating activity at the lowest Mo catalyst content (2.9Mo-ASA). Although, the MoS2 blocked Brønsted acid sites decreasing the ASA acidity, especially in IS and IMP catalysts, at the low Mo concentrations required with the IS methodology, most of the acidity was retained. In addition, in the case of IS catalysts, MoS2 particles were also found dispersed in the slurry feed independently of the ASA. Consequently, the IS catalyst retained the advantages of the unsupported MoS2 with the additional functionality of the acid component of the bifunctional catalyst, hence conversion was promoted due to both hydrogenation and hydrocracking reactions. These observations suggested that the bifunctional MoS2-ASA catalysts prepared in situ promotes hydrocracking reactions at lower temperatures reducing the severity of reaction conditions and limiting coke formation in slurry-phase hydroconversion. 1. INTRODUCTION The growing demand for transportation fuels combined with the depletion of conventional crude oil reserves has resulted in an increased need for residual oil upgrading.1 Among several residue oil conversion processes, slurry-phase hydroconversion is a promising alternative 2–6 because of the ability to process vacuum gas oils (VGO) and vacuum residues (VR), which are complex mixtures of paraffinic, naphthenic and aromatic hydrocarbons, with high metal, sulfur and nitrogen content.1,3,7 2 ACS Paragon Plus Environment
Page 3 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
Slurry-phase hydroconversion employs nano-sized transition metal sulfide catalysts,2,3,8–10 usually MoS2, generated in situ from oil-soluble precursors and a sulfur source.2,3,9,11,12 The resulting unsupported MoS2 catalysts dispersed in the reactant oil maximize contact between catalyst particles and reactants due to the nanometric MoS2 particle dimensions. Slurry-phase residue hydroconversion requires Mo concentrations < 1000 ppm to improve the quality of the product oil by increasing hydrogenation of aromatic compounds, catalyzing heteroatom and metal removal, and decreasing coke yield.3,11,13,14 However, residue conversion is driven by thermal cracking reactions that require high temperatures that also promote coke formation.3,13,15 Residue conversion can be enhanced by the use of bifunctional catalysts that have both hydrogenation and acidic functions, since the latter promotes hydrocracking reactions.16–19 Hence, a MoS2-acid bifunctional catalyst in slurryphase technology offers a path to high conversions of residue with minimal coke formation at reduced operating temperatures (below 430 ºC).3 There are few reports describing the use of a cracking catalyst for slurry-phase hydroconversion and most of them correspond to industrial developments published since the 1980´s, in which the preparation of the sulfide phase was carried out in situ during the hydroconversion and in the presence of inorganic or carbonaceous materials. The main focus of these studies was the recovery and reuse of the dispersed MoS2 catalysts.20–22 In more recent work, heteropoly acid precursors of Mo and W or transition metal precursors in the presence of inorganic acids were used, favoring residue oil conversions at lower temperatures compared to that required for thermal reactions; however, the characterization of the catalysts and the mechanism by which the acidic function is incorporated in these catalysts remains unclear.23–25 Eni Company has reported the effect of incorporating a fluid
3 ACS Paragon Plus Environment
Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 4 of 41
catalytic cracking (FCC) catalyst in the in situ preparation of the dispersed MoS2 to obtain a dual function catalyst for residue oil hydroconversion. They reported that both hydrogenation and cracking reactions were promoted and that the MoS2 particles help to protect the cracking catalyst from deactivation by coke deposition.26–28 In addition, they reported that after the catalytic test, the MoS2 particles were associated more with the coke obtained during the reaction than with the acidic function of the cracking catalyst particles, and with this information they proposed a model in which the MoS2 and acidic materials were phase-separated during the catalytic reaction. Other acidic materials such as talc, mica, alumina, silica, and silica-alumina were identified as possible acidic catalysts.28 In addition, Bdwi et al.29 evaluated a commercial supported hydrocracking W-Ni/Al2O3-SiO2 catalyst as co-catalyst with dispersed transition metal sulfides. The acidic function of the W-Ni/Al2O3-SiO2 catalyst enhanced the naphtha yield and the catalytic system was effective in reducing coke yield because of the presence of the dispersed catalyst.29 The above reports focused on the performance of the bifunctional catalysts, with far less data on catalyst properties reported, such that the interaction between both catalyst functions and their impact on the catalyst properties and activity, remains unclear. Furthermore, although the Mo concentration required for hydroconversion has been established, 26–28 the effect of the Mo concentration and the appropriate ratio between the hydrogenating and acidic functions of the bifunctional catalyst have not been reported. Regarding the characterization of bifunctional slurry phase catalysts, we recently reported on the incorporation of an amorphous silica-alumina (ASA) with dispersed MoS2 obtained in situ during phenanthrene-decalin hydroconversion at reaction temperatures between 300 and 400 °C. The presence of the ASA at 400 °C improved the structural and morphological
4 ACS Paragon Plus Environment
Page 5 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
properties of the MoS2 catalyst, promoted the conversion of both reactants and improved the selectivity towards cracking, isomerization and ring opening products.30 The beneficial effect of a cracking catalyst added to the MoS2 for residue hydroconversion has been demonstrated previously and different methodologies to incorporate the acidity have been reported, including in situ incorporation of an inorganic acid or the presence of supported bifunctional catalysts as co-catalyst of the unsupported sulfide. However, these methods have not been compared systematically,26–28 and consequently, how the method of incorporation of the acidic function influences the interaction between both catalyst components and thereby the physical and chemical properties of the catalysts and their performance is not known. Consequently, the aim of the present study is to generate bifunctional catalysts using ultradispersed MoS2 prepared from Mo oil-soluble precursors and an amorphous silica-alumina (ASA), evaluating different preparation methods at two catalyst compositions. We demonstrate that the composition and preparation methodology of the bifunctional MoS2-ASA catalyst impacts both the properties of the MoS2 and the catalytic activity of the MoS2-ASA catalyst, as assessed during the hydroconversion of a mixture of phenanthrene-decalin to simultaneously determine the ability of the catalysts to enhance hydrogenation, isomerization, ring opening, and cracking reactions. As noted previously, a mixture of phenanthrene-decalin has been used as model reactant to overcome the complexity of residue oil feedstocks and the associated difficulties of dispersed catalyst recovery and characterization, such that a fundamental understanding of the chemical transformations that occur during hydroconversion can be assessed.30 2. EXPERIMENTAL 2.1 Materials 5 ACS Paragon Plus Environment
Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 6 of 41
The reactants used were molybdenum-octoate (15 wt % Mo, provided by Strem Chemicals), carbon disulfide (Aldrich, ≥99.9 %), decalin (Aldrich, 99 %), phenanthrene (Aldrich, 98 %) and an amorphous silica-alumina (ASA, Siral® 40 provided by the Sasol Company) which was activated at 550°C in air for 3h before use. The model reactant mixture consisted of a solution of 10 wt% of phenanthrene in decalin. 2.2 Catalyst Preparation and Activity Assessment The composition of the MoS2-ASA catalysts is reported in terms of the nominal Mo content of the composite catalyst (i.e., Mo wt % content in the MoS2 + ASA composite). Catalysts with 2.9 wt% Mo and 13.0 wt% Mo, are named as 2.9 Mo-ASA and 13.0 Mo-ASA, respectively. The ASA concentration with respect to the reactant mixture was 2 wt% in all cases, and the corresponding Mo concentration with respect to the reactant mixture was 600 ppm Mo for the 2.9 Mo-ASA catalyst and 3000 ppm Mo for the 13.0 Mo-ASA catalyst.
Three different methods of preparation were examined as follows: (i) Mechanical mixture catalysts (MM) were obtained by adding to the reaction vessel MoS2 (previously prepared) and ASA in the quantities required to obtain the concentrations mentioned above. The mixture of the MoS2 and ASA solids was done by mechanical stirring in a 300 mL stirred-batch reactor (Autoclave Engineers) during the phenanthrenedecalin hydroconversion, and the catalysts recovered after the catalytic test were named as MM catalyst. The MoS2 used for the MM catalysts was prepared as an unsupported MoS2 catalyst by dissolving an appropriate amount of molybdenum-octoate and CS2 in decalin to yield a 3000 ppm Mo solution and a S/Mo atomic ratio of 3. The liquid mixture was placed in the stirred-batch reactor, purged to remove air and then pressurized to 2.8 MPa H2 at 6 ACS Paragon Plus Environment
Page 7 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
room temperature and heated to 400 °C while mixing at 1000 rpm. After 2 h, the reactor was cooled and the MoS2 was recovered by centrifuge at 12,000 rpm with several washing steps to remove the solvent. The MoS2 was subsequently placed in a glass U-tube reactor and dried in a furnace at 150 °C under N2 flow for 6 h. (ii) In situ catalysts (IS) were prepared in situ during the catalytic test. Appropriate amounts of molybdenum octoate, CS2 and the ASA to obtain the concentrations of Mo and ASA required, were added to the phenanthrene-decalin reactant mixture and placed in the 300 mL stirred-batch reactor. The reactor was heated to 400 °C and the reaction proceeded without further pre-treatment of the catalyst. Details of the reaction conditions are described below. (iii) Impregnation catalysts (IMP) were prepared by wet impregnation of ASA with a solution of molybdenum octoate in hexane. After impregnation, the samples were dried at 120 °C overnight and treated at 200 °C in static air for 3 h to chemically link the molybdenum octoate onto the ASA. The precursors were then added to a solution of CS2 in decalin (S/Mo ratio of 3) and sulfided using the 300 mL stirred-batch reactor operated at 2.8 MPa H2, 1000 rpm and 400 °C for 2 h. After sulfidation, the catalyst was recovered by centrifuge, washed and dried for further catalytic tests.
The catalyst activities for the hydroconversion of the model reactant mixture (10 wt% phenanthrene in decalin) were measured in the 300 mL stirred-batch reactor, operated at 400 °C and 2.8 MPa H2. The MM and IMP catalysts were added to the phenanthrenedecalin feed prior to the reaction; whereas, molybdenum octoate, CS2 and the ASA were added to the phenanthrene-decalin feed in the case of the IS catalysts. A liquid sample was
7 ACS Paragon Plus Environment
Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 8 of 41
withdrawn from the reactor following heat-up to 400°C and every hour thereafter for a total reaction time of 4 hours. Kinetic rate constants were calculated from these data by applying a 1st-order kinetic analysis, assuming conversion rates were only dependent on the concentration of the liquid reactant, and that the high and approximately constant H2 pressure ensured zero order kinetics with respect to the H2. The rate constants of decalin (kDec) and phenanthrene (kPhe) were calculated according to equations (S1) and (S2) (see Supporting Information). The identification and quantification of the liquid products was done using a GC/MS Shimadzu (QP-2010-S) equipped with a Restek RTX5 30 m × 0.25 mm column, with n-tetradecane as an internal standard. After the reactions, the catalysts were recovered, washed and dried for further characterization. Phenanthrene (Xp) and decalin (XD) conversions were calculated using equations (1) and (2): = ⁄ − ⁄ ⁄ ⁄ ∗ 100
(1)
= ⁄ − ⁄ ⁄ ⁄ ∗ 100
(2)
where , , and correspond to the areas determined by GC-MS analysis for the decalin, the internal standard and the phenanthrene in the sample mixture, respectively. The ratios ⁄ and ⁄ refer to the area ratio of component j to the standard
component area at the beginning of the reaction and after a reaction period of t hours, respectively. Hydrogen consumption was not measured directly but estimates based on the phenanthrene conversion and product selectivity showed H2 consumption to be < 15% of the initial moles of H2 at the maximum phenanthrene conversion. The selectivity and yield to the selected groups of products were calculated using the following equations: 8 ACS Paragon Plus Environment
Page 9 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
= / !*"
% &'
# / $( ∗ 100 3
+ = ,- 4
Where ∑ is the sum of the GC-MS areas of all products corresponding to the group i. and are the concentration and the area of the internal standard, and
is the
response factor for the group of products i. ,- is the total conversion of the feed and is calculated as ,- = 0.1 + 0.9
2.3 Catalyst Characterization MoS2 morphology, stacking and length distribution were determined from high resolution transmission electron microscopy (HRTEM) using a (JEOL) JEM 200 scanning transmission electron microscope operated at 200 kV. The length and stacking number of at least 200 particles were used to generate histograms for both properties of each sample. Structural characterization was determined by X-ray diffraction (XRD) using Bruker D8 Focus (0−20, LynxEye detector) diffractometer with Co Kα (λ = 1.789 Å) radiation. Surface composition of the catalysts and chemical state of Mo and S were determined by X-ray photoelectron spectroscopy (XPS) using a Leybold Max200 spectrometer with Mg Kα as photon source generated at 1253.6 eV. The C 1s peak at 284.5 eV was taken as reference to determine the binding energies. XPSPEAK41 software was used for deconvolution of the experimental spectra. Shirley background subtraction was applied, and
9 ACS Paragon Plus Environment
Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 10 of 41
the peaks were decomposed through mixed Gaussian−Lorentzian functions (80%−20%). The Brunauer−Emmett−Teller (BET) surface area and the pore volume were determined from N2 adsorption − desorption isotherms measured at −196 °C using a Micromeritics ASAP 2020 analyzer. Samples were degassed at 150 °C under vacuum for 8 h before analysis. The surface area was calculated using the BET equation in the relative pressure range (P/Po) of 0.01−0.20. N2 adsorption at a relative pressure of P/Po = 0.99 was used to obtain the total pore volume (Vtotal).. Particle size of the MoS2, ASA and bifunctional MoS2/ASA catalysts were measured using a Horiba LB-550 dynamic light scattering (DLS) particle size analyzer. Samples were dispersed in acetone, stirred for several hours and then allowed to settle for 20 mins before the size of the particles that were most stable in suspension was determined. Total and Brønsted acidity of the catalysts were determined by temperature programmed desorption of ammonia (NH3-TPD) and isopropylamine (IPA-TPD), respectively. The measurements were performed on a Micromeritics Autochem II chemisorption analyzer equipped with a thermal conductivity detector (TCD) and coupled to a ThermostarTM PFEIFFER mass spectrometer. Each sample was degassed at 450 °C for 30 min under He flow of 30 mL/min, before cooling to 50 °C. The sample was then saturated with the adsorbate, either in a flow of 5% NH3/He over a 30 min period, or in pulses of isopropylamine (IPA). The gas flow was then switched to He to remove physisorbed NH3 or IPA over a 90 min period. The sample was then heated under He flow at a heating rate of 10 °C /min to 500 °C and the amount of NH3 or propylene desorbed was quantified. Note that the characterization techniques described above were applied to the catalysts recovered after the catalytic test so that all catalysts had the same reaction history. Since the IS 10 ACS Paragon Plus Environment
Page 11 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
catalysts were generated during reaction we cannot access “fresh” IS catalyst samples and consequently only the used catalysts can be reasonably compared. However, to assess the acidity of the IS catalysts without the possible influence of coke formation that may occur during reaction, IS samples were also prepared as described above but in the presence of decalin alone (rather than the phenanthrene-decalin mixture) and for a reaction period of only 1 hour. For consistency, MM and IMP catalysts were also reacted in a decalin mixture for 1 hour and these samples were recovered for the acidity measurement. 3. RESULTS AND DISCUSSION 3.1 Catalyst characterization 3.1.1
Morphological and structural properties
Figure 1 shows the HRTEM micrographs for the MM, IS, and IMP catalysts at a composition of 2.9Mo-ASA in which the layered structure of MoS2 can be observed. Significant morphological differences are apparent: MoS2 particles were segregated from ASA in the MM catalyst; whereas, the IS system showed MoS2 particles covering the ASA. MoS2 lamellae were scarce and difficult to observe on the IMP catalyst, suggesting that the MoS2 layers were not completely formed or that they were highly dispersed over the ASA surface and were therefore not as distinguishable as for the other preparation methods.
11 ACS Paragon Plus Environment
Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 12 of 41
Figure 1. HRTEM images of catalysts at a composition of 2.9Mo-ASA prepared by different methodologies: a) MM; b) IS; c) IMP Figure 2 shows the length and stacking number histograms for the MoS2 particles of the MM and IS catalysts at a composition of 2.9Mo-ASA, obtained by the analysis of at least 200 particles, with the fitting functions used to estimate the mean values reported in Table 1, plotted as dashed lines. The histograms show that the MoS2 particles were longer and more stacked for the MM catalysts compared to the IS catalysts. MoS2 particles in the MM catalyst presented similar dimensions to those reported for unsupported MoS2 alone,30 which indicates that the interaction of the preformed MoS2 with the ASA during the catalytic test did not modify the particle morphology. Additionally, we reported previously the positive effect of the presence of ASA for the IS prepared catalyst in decreasing the MoS2 particle dimensions and hence increasing Mo dispersion (fMo) from 8.1 % for the bulk MoS2 to 12.6 % for the IS prepared catalyst. The Mo dispersion is a measure of the Mo atoms located at the crystallite edges, which are supposed to be responsible for the activity.30 Similar dimensions and fMo to those reported for IS (1.5Mo-ASA) and bulk MoS2 were obtained here for the IS (2.9Mo-ASA) and the MM catalyst (Table 1). Note that it was not possible to obtain histograms for the MoS2 of the IMP catalyst because of the few 12 ACS Paragon Plus Environment
Page 13 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
particles detected, and the values reported in Table 1 for length and stacking number were obtained from the measurement of about 20 particles.
Figure 2. Histograms of length and number of stacks of MoS2 for the MM and the IS catalysts at a composition of 2.9Mo-ASA. Table 1. Mean values for the length and number of stacks of MoS2 for the MM, the IS and the IMP catalysts at a composition of 2.9Mo-ASA. MM Properties Stacking number TEM 3.9 ± 1.6 13.1 ± 5.4 Length (nm) 8.6 Mo dispersion, fMo *Average of 20 measurements -- Not measured
IS 2.3 ± 1.4 8.4 ± 3.8 12.6
IMP*
