SBA-16 for

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Catalysis and Kinetics

Optimal synthesis of hierarchical porous composite ZSM-5/SBA-16 for ultra-deep hydrodesulfurization of DBT and 4,6-DMDBT, Part 2: The influence of Aging temperature on the Properties of NiMo Catalysts Xilong Wang, Peng Du, Zhen Zhao, Jinlin Mei, Zhentao Chen, Yuyang Li, Peng Zheng, Jiyuan Fan, Aijun Duan, and Chunming Xu Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b01454 • Publication Date (Web): 11 Jun 2018 Downloaded from http://pubs.acs.org on June 12, 2018

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Energy & Fuels

Optimal

synthesis

of

hierarchical

porous

composite

ZSM-5/SBA-16 for ultra-deep hydrodesulfurization of DBT and

4,6-DMDBT,

Part

2:

The

influence

of

Aging

temperature on the Properties of NiMo Catalysts

Xilong Wang †, Peng Du †, Zhen Zhao, Jinlin Mei, Zhentao Chen, Yuyang Li, Peng Zheng, Jiyuan Fan, Aijun Duan *, Chunming Xu *

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing, 18 Fuxue Road, Beijing, P.R. China, 102249

†Xilong Wang and Peng Du contributed equally to this work.

Corresponding Author: *E-mail: [email protected]. Tel: +86 10 89732290. *E-mail: [email protected]. Tel: +86 10 89733392.

Abstract ZSM-5/SBA-16 (ZS) supports were prepared using two-step hydrothermal crystallization method. The effect of aging temperature on the structural properties of series ZS supports was studied. The prepared samples were analyzed by XRD, SEM, 1

ACS Paragon Plus Environment

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N2 physisorption,

27

Page 2 of 44

Al MAS NMR, H2-TPR, Raman, XPS, pyridine-FTIR and

HRTEM. The hydrodesulfurization (HDS) performance of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was examined at T = 340 ºC and PH2 = 4 Mpa. The NiMo/ZS-45 catalyst synthesized at the aging temperature of 45 ºC exhibited the best catalytic activities of DBT and 4,6-DMDBT, which attributed to its regular shape, well-organized pore structure, high sulfidation degree and a compromise between the acidity and metal-support interaction (MSI, Mo-O-Si). Moreover, the possible DBT and 4,6-DMDBT HDS reaction networks over NiMo/ZS-45 were proposed.

Keywords ZSM-5/SBA-16;

Aging

temperature;

Dibenzothiophene;

4,6-dimethyldibenzothiophene; Hydrodesulfurization

1. INTRODUCTION The exhaust emissions caused by diesel vehicles not only pollute the environment but also affect people's health.

1-4

More stringent environmental regulations and the

control on sulfur content in diesel have been implemented in various countries. 5-7 It is generally believed that the difficulty in ultra-deep desulfurization of diesel is to remove DBT and 4,6-DMDBT. 8-12 However, the most widely-used catalysts are not efficiently active to remove these sulfide molecules because of the steric inhibition of alkyl groups adjacent to sulfur atoms. 13-16 For achieving ultra-deep HDS, new type of catalysts, especially new catalyst supports, need to be developed urgently since they 2


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can affect the morphology, orientation, size, and sulfidation degree of the sulfide active phase. 17, 18 Rana et al reported that HDS catalysts supported on silica exhibited a lower mutual effect between the support and the active phase, which can lead to better sulfurization of the catalyst with more CoMoS-II or NiMoS-II HDS active sites. 19

Examples of zeolites like Y, ZSM-5 and Beta used in industrial catalysts are

common.

20-22

Among these zeolites, ZSM-5 is the most used due to its simple

synthesis process and variable physicochemical parameters. ZSM-5 also exhibits good hydrogenation and isomerization performance when applied to HDS reactions. 23, 24 Wu et al. 25 reported that the nano-sized HZSM-5 catalyst showed good isomerization performance in the removal of 4,6-DMDBT, which effectively eliminate the steric inhibition of alkyl-substitutes in the molecules of 4,6-DMDBT during the HDS reaction. Sugioka et al.

26

found that the catalytic performance of HZSM-5 supported

catalyst was better than that of the widely used industrial alumina catalysts. However, the small pore of ZSM-5 limits the diffusion of sulfur-containing macromolecular compounds, which is also reflected in many other studies.

27-29

Mesoporous silica

materials present several advantages such as wide surface areas, high pore volumes and mean pore-size distribution. These structural features are conducive to improving the mass transfer performance and dispersion of the active metal. SBA-16 is a kind of desired mesoporous silica support for potential applications because of its cubic cage structure with multi-direction and large pore structure, which is conducive to diffusion and being functionalized.

30, 31

Cao et al.

32

reported that NiMo/Al-SBA-16 with

corresponding support prepared under 50 °C displayed high DBT HDS activity under 3


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the condition of 20 h-1. Guzman et al. 33 also reported that SBA-16 substrate material is an efficient support for HDS catalysts. Nevertheless, pure silica mesoporous materials are short of Brönsted and Lewis acid that favor the HDS reaction. In addition, the structural stability, especially the thermal and hydrothermal stability, is relatively low compared to the microporous molecular sieves and the traditional alumina supports. In recent years, different research groups reported micro-mesoporous composite silica materials as the promising supports for hydrotreating catalysts since the composite silica materials are a combination of the merits of microporous molecular sieve and mesoporous silica materials. Zhang et al.

34

studied HDS activity in DBT

over NiMo/Beta-KIT-6. The NiMo/Beta-KIT-6 catalyst exhibited higher conversions in DBT HDS than the pure Beta and KIT-6 supported catalysts, and even than the commercial NiMo/γ-Al2O3 catalyst, the study found. Similar studies like the applications of Beta-SBA-15 and ZSM-5/KIT-6 micro-mesoporous composite materials on HDS have been also reported. 25, 35 So far, there were few reports about the synthesis of micro-mesoporous silica materials ZSM-5/SBA-16 (ZS). In addition, the influence of synthetic environment on the structure performance of this kind of catalyst support has been also paid less attention. In the preparation process of support, the synthesis may have different exposures to environmental factors, resulting in various textural and structural properties. Taking hydrotreating catalysts as an example, good dispersion, suitable acidity and a moderate mutual effect between the metal precursors and the support are 4


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desirable.

36

These are all strongly affected by the structural characteristics of the

support. The aging temperature is one of important factors to the structural characteristics of porous silica materials. 37, 38 However, it remains unclear for the influence of the aging temperature used in the support preparation process on the structure of ZSM-5/SBA-16. In this research, ZS composites were fabricated via two-step hydrothermal crystallization method using ZSM-5 precursor. Different aging temperatures were investigated in the synthesis process. DBT and 4,6-DMDBT were selected to investigate the activities of NiMo catalysts supported on the series ZS materials. In order to analyze the synergistic effects of MSI, acidic sites and other factors on DBT and 4,6-DMDBT HDS activity, multiple characterization techniques have been adopted. The results showed that NiMo/ZS-45 catalyst exhibited the higher DBT and 4,6-DMDBT HDS conversions, which could be attribute to the synergism of the well-ordered pore structure, regular morphology, high sulfidity and a compromise between the acidity and the MSI. The possible reaction network for the DBT and 4,6-DMDBT HDS over series NiMo/ZS were also investigated, respectively.

2. EXPERIMENTAL SECTION 2.1 Preparation of the supports 2.1.1 Synthesis of ZSM-5 seed The synthesis process of zeolite ZSM-5 seed was described in the research of part 1 (DOI: 10.1021/acs.energyfuels.8b00708). 5


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2.1.2 Synthesis of ZS supports ZS synthesized under different aging temperatures (25 ºC, 35 ºC, 45 ºC, 55 ºC and 65 ºC) were prepared by following steps. 4.0 g surfactant F127 and 10 g KCl were added into 240 mL HCl solution (1.5 mol/L). Afterwards, the hybrid was stirred for 2.0 h at a given aging temperature. Afterwards, 12.0 g co-surfactant butanol was dropped into the above mixture and stirred for 2.0 h at the same temperature. After 16.6 g TEOS being added, the resultant solution was stirred for 30 min for prehydrolysis, and then 18.57 g zeolite ZSM-5 seed was added slowly into the above mixture. The solution was stirred for 1 h and then kept static for 24 h. The resulting mixture was transferred into a Teflon-lined stainless autoclave and reacted at 100 °C under static condition for 24 h. The solid product was gained through filtration and dried at 90 ºC for 8.0 h, then calcined in air at 550 ºC for 6 h to wipe off the structure directing agent. The ZS materials synthesized at different aging temperatures were denoted as ZS-25, ZS-35, ZS-45, ZS-55 and ZS-65, correspondingly.

2.1.3 Preparation of the corresponding catalysts The preparation of series catalysts and the corresponding details were described in the research of part 1 (DOI: 10.1021/acs.energyfuels.8b00708). The corresponding NiMo catalysts were labeled as NiMo/ZS-x, and x represents different aging temperatures.

2.2 Characterization of the supports and the catalysts 6


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The characterization methods (XRD, H2-TPR, XPS and HRTEM et al.) of series supports and the corresponding catalysts and the relevant details were described according to the published paper. 39, 40

2.3 Evaluation of HDS performance of catalysts The HDS reaction conditions (temperature, H2 pressure, H2/Oil ratio, WHSV) and the corresponding details were described in the research of part 1 (DOI: 10.1021/acs.energyfuels.8b00708).

Besides,

Desulfurization

degree

(%)

was

calculated by Equations (a): HDS (%) = (Sf -Sp)/Sf ×100%

(a)

where Sf represents the feeds’ sulfur contents (ppm) of the and Sp represents the products’ sulfur contents (ppm).

3. RESULTS 3.1 Characterization of the supports 3.1.1 XRD of the supports

(B)

Intensity, a.u.

(A)

Intensity, a.u.

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

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a b c d e 1

2

3 4 2θ, degree

f a b c d e 10

5

20

30 40 2θ, degree

50

Figure 1. (A) Small-angle and (B) wide angle XRD patterns of series ZS obtained at different aging temperatures. (a) ZS-25, (b) ZS-35, (c) ZS-45, (d) ZS-55, (e) ZS-65, (f) ZSM-5. 7


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Figure 1(A) displays the small-angle XRD pattern of series ZS synthesized at different aging temperatures. It can be seen that all the samples have the characteristic peaks at 2θ=0.2°~1° which correspond to the cubic Im3m space group of SBA-16, manifesting that all the synthesized composites possess a typical mesoporous feature of SBA-16. 29 This is also well reflected by the results of the subsequent TEM images. In addition, when the aging temperature is 45 ºC, the intensity of the main diffraction peak (110) of ZS-45 is stronger than those of other ZS materials, indicating that it possesses the best structural order among these series materials. Furthermore, the augmentation of the aging temperature caused an apparent blue shift toward the lower angles, indicating the enlargement of the pore size, which agrees well with the subsequent results of nitrogen adsorption-desorption. As shown in the wide-angle XRD pattern in Figure 1(B), all the ZS series materials synthesized at different aging temperatures showed characteristic peaks assigned to ZSM-5 crystals at 2θ = 8~10 ° and 22.5~25 °, respectively, and the peak intensities are much weaker than those of the pure ZSM-5 zeolite crystal, indicating that the ZSM-5 structure present in the composite is the primary and secondary unit structure of ZSM-5 rather than the fully crystallized ZSM-5. In addition, there was no significant change in the positions and intensities of the respective peaks because of no change in the addition amount of the ZSM-5 microemulsion.

3.1.2 N2 physisorption of the supports

8


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Figure 2(A) shows N2 physisorption isotherms for the ZS series materials synthesized at various aging temperatures. It can be observed from the figure that all materials have a steep hysteresis loop in the range of relative pressure P/P0 = 0.4-0.8. The isotherms are type IV in line with the classification by IUPAC and have a H2 hysteresis loop derived from mesopores.

41-43

The inflexion position moves gradually

toward higher relative pressures and the volume of nitrogen adsorbed increases with aging temperatures, which indicates an augment in pore size. 44 Figure 2(B) shows the pore size distribution gained via the method of BJH. The series materials display a narrow mesopore distribution between 2~6 nm. Table S2 (in Supporting Information) lists the pore structural parameters of series ZS. The specific surface areas, pore volumes and pore size increase with the aging temperature increasing, which is consistent with the results reflected in the above

dV/dD, cm3·g-1·nm-1

adsorption-desorption isotherms.

Volume, m3·g-1

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

(A) a b c d e

0.0

0.2 0.4 0.6 0.8 1.0 0 Relative Pressure, P/P 0

(B) a b c d e 20 40 Pore diameter, nm

60

Figure 2. (A) N2 physisorption isotherms and (B) pore diameter distribution patterns of the ZS series materials obtained at various aging temperatures. (a) ZS-25, (b) ZS-35, (c) ZS-45, (d) ZS-55, (e) ZS-65.

9


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3.1.3 27Al MAS NMR of the supports Figure 3 presents

27

Al NMR spectra of the ZS series materials synthesized at

various aging temperatures. All the ZS series materials have significant peaks at δ = 0 ppm and δ = 54 ppm which are ascribed to the octahedral (extra-framework Al species) and tetrahedral coordinated aluminum atoms, respectively. temperature increases, the peak intensities of

27

45

As the aging

Al NMR spectra at δ = 0 ppm

gradually increase, indicating the increase of non-framework aluminum in the composite. This further suggests that, as the aging temperature increases, the percentage of aluminum entering into the framework gradually decreases.

Intensity, a.u.

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 44

a b c d e

200 150 100 50

Figure 3.

27

0 -50 -100-150 ppm

Al NMR spectra of the ZS series materials. (a) ZS-25, (b) ZS-35, (c)

ZS-45, (d) ZS-55, (e) ZS-65.

3.1.4 TEM images of the supports The ordered channel structure of the ZS series samples with a body-centered cubic structure (Im3m) was confirmed by TEM. It can be seen from Figure S1 (in

10


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Supporting Information) that the degree of internal order of the ZS series materials decreases as the aging temperature increases.

3.1.5 SEM images of the supports The morphologies of series ZS synthesized under different aging temperatures are shown in Figure 4. It can be seen that as the aging temperature increases, the morphology of the materials change from sphere to polyhedron. As the aging temperature is 45 ºC, the morphology of the material presents well regular octadecahedron. As the temperature is above 45 ºC, the shapes of the particles gradually become irregular. Since the assembly rate increases with the temperature, it is difficult to generate regular mesoporous materials. This is also evidenced by the reduced orderliness observed from TEM images. In addition, the hydrophobicity of the hydrophilic end (EO) of the surfactant increased; hence, the stretched hydrophilic end becomes curved and moves closer to the hydrophobic end (PO), which makes the micellar particles change from sphere to irregular shape.

46

This eventually leads to

irregularities in the shape of the material. Moreover, the sizes of the micellar particles become larger in this process, leading to an augment of the pore size of the synthesized

materials,

which

is

consistent

with

adsorption-desorption.

11


the

result

of

nitrogen

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(a)

Page 12 of 44

(b)

10 µm

20 µm

(c)

(d)

10 µm

10 µm

(e)

20 µm

Figure 4. SEM images of the ZS series supports. (a) ZS-25, (b) ZS-35, (c) ZS-45, (d) ZS-55, (e) ZS-65.

3.2 Characterization of the catalysts 3.2.1 Pyridine-FTIR of the oxide catalysts

12


L

(A) L B

1700

L

B L+B a b c d e

1600 1500 Wavenumber, cm-1

Absorbance, a.u.

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

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Absorbance, a.u.

Page 13 of 44

(B)

1400 1700

B

L L

B

L+B L

1600 1500 Wavenumber, cm-1

a b c d e 1400

Figure 5. Pyridine-FTIR spectra on various catalysts (a) NiMo/ZS-25, (b) NiMo/ZS-35, (c) NiMo/ZS-45, (d) NiMo/ZS-55 and (e) NiMo/ZS-65 after degassing at (A) 200 ºC and (B) 350 ºC.

To further confirm the acid strength and acid types of NiMo/ZS series catalysts, the samples were investigated via Pyridine-FTIR (Py-IR). Py-IR spectra of NiMo/ZS series catalysts were recorded within the scope of 1700-1400 cm−1 as reported in Figure 5. The Py-IR spectra recorded at 200 ºC is attributed to the total contents of acid sites, while the Py-IR spectra recorded at 350 ºC is attributed to the contents of mediate and strong acid. According to the reported references, 4 the characteristic signals at 1446, 1492, 1575 and 1622 cm-1 are attributed to L acid. Pyridine adsorbed on B acid displays peaks at 1546 and 1639 cm-1. Furthermore, the band at 1490 cm-1 reflects the presence of both L and B acid. Subsequently, the peak intensities of various catalysts all decrease as the trends of NiMo/ZS-25 > NiMo/ZS-35 > NiMo/ZS-45 > NiMo/ZS-55 > NiMo/ZS-65.

13


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The specific data about the distribution of acid strength and the acid amounts of series NiMo/ZS are displayed in Table S3 (in Supporting Information). The quantities of acid sites and the ratio of B and L acid for both total acid and the medium & strong acid all decrease as the trends of NiMo/ZS-25 > NiMo/ZS-35 > NiMo/ZS-45 > NiMo/ZS-55 > NiMo/ZS-65. The Py-IR results confirm that the extents of Al atom incorporated into the framework decrease with increase in aging temperature, which result in decreasing acidities of the support. All of the phenomena are consistent with the 27Al MAS NMR results. 3.2.2 H2-TPR of the oxide catalysts H2-TPR tests were carried out on series NiMo/ZS in the form of the oxidation state. The TPR profiles of series NiMo/ZS are exhibited in Figure 6. All catalysts in the TPR profile show two peaks. The low-temperature characteristic peak observed in the range of 400-600 °C is due to Mo6+ → Mo4+ (MoO3 → MoO2), while the high temperature characteristic peak observed in the range of 700-900 °C is the reduction of Mo4+ → Mo0 (MoO2 → Mo0).

47

The first reduction temperatures and the deep

reduction temperatures decrease in the same tendency: NiMo/ZS-25 (503 °C, 855 °C) > NiMo/ZS-35 (481 °C, 837 °C) > NiMo/ZS-45 (465 °C, 832 °C) > NiMo/ZS-55 (449 °C, 817 °C) > NiMo/ZS-65 (441 °C, 793 °C), which is indicative of the same decreasing trend of the MSIs over the NiMo/ZS series catalysts. The proportions (Table S4, in Supporting Information) of low-temperature reduction species decrease in the order of NiMo/ZS-65 > NiMo/ZS-55 > NiMo/ZS-45 > NiMo/ZS-35 > NiMo/ZS-25. Appropriate MSI is conducive to obtaining suitable 14


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Page 15 of 44

dispersions of active Mo species, which can improve the reduction and sulfidation of the oxide Mo species. This point will be further addressed in the discussion section.

TCD signal, a.u.

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

503

a

481

b

465

c d e

200

855 837 832 817

449 441

793

400 600 800 Temperature, oC

1000

Figure 6. H2-TPR profiles of the oxide catalysts. (a) NiMo/ZS-25, (b) NiMo/ZS-35,

(c) NiMo/ZS-45, (d) NiMo/ZS-55 and (e) NiMo/ZS-65.

3.2.3 Raman of the oxide and sulfide catalysts

Raman spectra of series supported NiMo catalysts in oxide and sulfide types are presented in Figure 7(A) and (B), respectively. The spectra of series oxide catalysts show typical peaks at 955, 908, 826, 331 and 564 cm-1. The absorption peaks at 955, 908 and 826 cm-1 can attribute to the NiMoO4 precursor phase.

48

The peak at 331

cm-1 is due to M = OT (T stands for terminal bonding) bending vibration which is relevant with the existence of octahedral MoO42- species. The band at 564 cm-1 is associated to the stretching vibration of Al-O bond. 49, 50 Especially, the broad peak at 890-1000 cm-1 is the characteristics of stretching vibrations of M = OT double bond, usually associated to the strength of MSI.

51

The trend displayed for the (M = OT)

intensity is NiMo/ZS-25 > NiMo/ZS-35 > NiMo/ZS-45 > NiMo/ZS-55 > 15


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NiMo/ZS-65, which suggests that the MSI decrease as the aging temperature rises in the support synthesis process. In addition, the Mo = OT species are easily sulfided and may promote the generation of active sites. 52 The spectra of series sulfide catalysts display apparent absorption bands at 380, 405, 454 and 634 cm-1. The bands at 380 and 405 cm-1 can be attributed to the E12g and A1g of the active MoS2 crystal texture. The bands at 454 and 634 cm-1 are ascribed to the resonance Raman scatting,

53, 54

whose strength is associated with the

sulfurization of the catalysts. The tendency observed for the intensity of the bands is NiMo/ZS-45 > NiMo/ZS-35 > NiMo/ZS-25 > NiMo/ZS-55 > NiMo/ZS-65, indicating that the sulfidation degree of the Mo species follows the parallel order.

(A)

a b c d e

200

(B)

Intensity, a.u.

Intensity, a.u.

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 16 of 44

400 600 800 1000 1200 Raman shift, cm-1

a b c d e 400

600 800 Raman shift, cm-1

1000

Figure 7. Raman spectra of (A) oxide catalysts and (B) sulfide catalysts. (a)

NiMo/ZS-25, (b) NiMo/ZS-35, (c) NiMo/ZS-45, (d) NiMo/ZS-55 and (e) NiMo/ZS-65. As can be seen from the Raman spectra, the majority of the Mo species in oxidation state have been converted into the sulfide MoS2 active phase after the pre-sulfurization stage. In addition, the characteristic peaks of the Ni metal compound 16


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do not appear because the Ni species has a relatively weak peak intensity and may be obscured by the strong absorption peak of the Mo species.

3.2.4 XPS of the sulfide catalysts

XPS is a useful method for determining the surface composition and chemical state of the supported catalysts. XPS experiments were carried out on series sulfide NiMo/ZS. XPS spectra of series NiMo/ZS sulfide catalysts are presented in Figure 8 and corresponding data are reported in Table S5 (in Supporting Information). The fitting standards are described on the previous researches. 11, 55 The sulfidation degree of series sulfide catalysts follows the sequence of NiMo/ZS-45 (70 %) > NiMo/ZS-35 (65%) > NiMo/ZS-25 (60 %) > NiMo/ZS-55 (58 %) > NiMo/ZS-53 (53 %), which coordinates well with the Raman analysis of the corresponding sulfide catalysts.

17


Energy & Fuels

(Ⅵ Ⅵ)

Mo Ⅵ (3/2),(5/2)

240

S

2-

236 232 228 224 Binding energy, eV

(c)

Intensity, a.u.

(b)

(Ⅴ Ⅴ)

Mo Ⅴ (3/2),(5/2)

Intensity, a.u.

(Ⅳ Ⅳ)

Mo Ⅳ (3/2),(5/2)

(Ⅳ Ⅳ)

Mo Ⅳ (3/2),(5/2) (Ⅵ Ⅵ)

Mo Ⅵ (3/2),(5/2)

240

S

2-


(e)

(Ⅳ Ⅳ)

Mo Ⅳ (3/2),(5/2)

(Ⅳ Ⅳ)

Mo Ⅳ (3/2),(5/2) (Ⅵ Ⅵ)

Mo Ⅵ (3/2),(5/2)

240

Intensity, a.u.

Intensity, a.u.

(a)

Intensity, a.u.

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 18 of 44

2-


(d) Mo(ⅣⅣ) (3/2),(5/2)

(Ⅴ Ⅴ)

Mo Ⅴ (3/2),(5/2)

(Ⅵ Ⅵ)

Mo Ⅵ (3/2),(5/2)

240

S

S

2-


(Ⅴ Ⅴ)

Mo Ⅴ (3/2),(5/2)

(Ⅵ Ⅵ)

Mo Ⅵ (3/2),(5/2)

240

S

2-


Figure 8. Mo3d XPS spectra of the sulfide catalysts. (a) NiMo/ZS-25, (b)

NiMo/ZS-35, (c) NiMo/ZS-45, (d) NiMo/ZS-55, (e) NiMo/ZS-65. 3.2.5 HRTEM of the sulfide catalysts

The MoS2 morphologies of fresh sulfide catalysts were investigated by means of HRTEM technique. The data were counted by calculating the amounts of stacked 18


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Energy & Fuels

layers and size of more than 400 slabs using a mass of micrographs of various zone of the sulfide catalyst. HRTEM images of various catalysts are displayed in Figure 9. All catalysts show the typical fringes of MoS2 slabs with various stacking degrees and slab length. As the aging temperature increases, there is a significant overall increase in slab length and in stacking degree of the MoS2 slabs. For the HDS reaction investigated in this research, the generation of high MoS2 stacking appears unbeneficial because low edge-to-basal active sites can be exposed. However, when the active metal appears low degree of stacking on the surface of the catalyst, it is restrictive to the generation of NiMoS-II active phases of HDS due to the strong MSI. Thus, to adjust an appropriate MSI is crucial for the improvement of the HDS efficiency. The average length (Lav), the number of layers (Nav) and the dispersiveness (fMo) for the MoS2 crystallites for different catalysts are presented in Table 1. Lav and Nav values of MoS2 phases on series NiMo/ZS sulfide catalysts follow the order of NiMo/ZS-65 (4.3 nm, 3.2) > NiMo/ZS-55 (4.1 nm, 3.0) > NiMo/ZS-45 (3.9 nm, 2.8) > NiMo/ZS-35 (3.8 nm, 2.7) > NiMo/ZS-25 (3.5 nm, 2.5). However, fMo values of MoS2 phases on series NiMo/ZS follow the tendency of NiMo/ZS-25 (0.35) > NiMo/ZS-35 (0.32) > NiMo/ZS-45 (0.31) > NiMo/ZS-55 (0.29) > NiMo/ZS-65 (0.26). Compared to the other four catalysts, NiMo/ZS-45 catalyst is not only in possession of a suitable stacking degree of MoS2 slabs, but also a relatively high dispersiveness, which can improve the HDS efficiency.

19


Energy & Fuels

50 40 30 20 10 0 1 2 3 4 5 6 7 8 Number of layers

50 40 30 20 10 0 1 2 3 4 5 6 7 8 Number of layers

(B)

%

%

(A)

10 nm

50 40 30 20 10 0 1 2 3 4 5 6 7 8 Number of layers

50 40 30 20 10 0 1 2 3 4 5 6 7 8 Number of layers

%

(D)

%

(C)

10 10 nm nm

10 nm

(E)

10 nm

50 40 30 20 10 0 1 2 3 4 5 6 7 8 Number of layers

(F)

%

80 NiMo/ZS-25

Fraction, %

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 20 of 44

NiMo/ZS-35

60

NiMo/ZS-45 NiMo/ZS-55

40

NiMo/ZS-65

20 0

0-20

20-40 40-60 60-80 >80 Slab length, 10-1 nm

10 nm

Figure 9. HRTEM micrographs of the catalysts in sulfide form. (a) NiMo/ZS-25, (b)

NiMo/ZS-35, (c) NiMo/ZS-45, (d) NiMo/ZS-55, (e) NiMo/ZS-65, (f) the length distribution of the MoS2 particles. 20


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Energy & Fuels

Table 1. Lav and Nav of MoS2 slabs.

Catalyst

Lav (nm)

Nav

fMo

NiMo/ZS-25

3.5

2.5

0.35

NiMo/ZS-35

3.8

2.7

0.32

NiMo/ZS-45

3.9

2.8

0.31

NiMo/ZS-55

4.1

3.0

0.29

NiMo/ZS-65

4.3

3.2

0.26

3.3 Results of DBT HDS The DBT HDS evaluation on series NiMo/ZS were measured under different WHSVs from 10 to 100 h-1 and the results are reported in Figure 10. For comparison, the evaluation result of a commercial NiMo/Al2O3 catalyst was obtained. The contact time between the reactants and the catalysts was prolonged by the decrease of WHSVs. Moreover, they follow the same decline trend: NiMo/ZS-45 > NiMo/ZS-35 > NiMo/ZS-25 > NiMo/ZS-55 > NiMo/ZS-65 > NiMo/Al2O3. The highest DBT HDS conversions were obtained over NiMo/ZS-45 catalyst at all WHSVs, which might benefit from the synergistic effects of the ordered pore structure of the support, regular morphology, high sulfidation degree, suitable MSI and appropriate acidity.

21


Energy & Fuels

100

Desulfurization degree, %

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 22 of 44

80

c b a d e f

60 40 20

100

80

60 40 WHSV, h-1

20

0

Figure 10. DBT HDS results at different WHSVs (340 ºC, 4 MPa, 200 mL/mL) (a)

NiMo/ZS-25, (b) NiMo/ZS-35, (c) NiMo/ZS-45, (d) NiMo/ZS-55, (e) NiMo/ZS-65, (f) NiMo/Al2O3.

The DBT HDS product distributions on NiMo/ZS-45 (GC spectra, Figure S5, in Supporting Information) under various WHSVs are presented in Figure 11. Lowering WHSV can increase DBT desulfurization degree via direct desulfurization (DDS) pathway, which can be seen from the increase of biphenyl (BP) selectivity and the decrease of cyclohexylbenzene (CHB) selectivity. DDS route is the principal reaction route of DBT HDS reaction at 10-100 h-1 on NiMo/ZS-45, which can be seen via that the BP selectivities no less than 50 % at 10-100 h-1. As WHSVs decreases, the selectivities of cyclopentylmethylcyclohexane (CPMCH), cyclopentylmethylbenzene (CPMB) and isophenyl hexadiene (PHDi) products gradually increase, while the selectivity of tetrahydrodibenzothiophene (THDBT) product decreases.

22


Page 23 of 44

BP

60 Selectivity, %

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

40

CHB

CPMB

20 THDBT PHDi CPMCH 0 100

80

60 40 WHSV, h-1

20

0

Figure 11. DBT HDS product distributions on NiMo/ZS-45 at various WHSVs.

To investigate the reaction routes of DBT on series NiMo/ZS, the HDS products were detected using GC-MS at the same condition with the total DBT conversion (equal to 50 %) (Figures S4, in Supporting Information). The corresponding DBT HDS reaction network is deduced in Figure S6 (In Supporting Information). DBT HDS proceeds through two major parallel pathways: 55 (i) DDS pathway, C–S bonds break directly and BP is the final product; and (ii) HYD pathway, which involves the hydrogenation of the aromatics ring prior to the desulfurization step, CHB, CHEB, THDBT, PHDi, CPMB and CPMCH are the intermediate or final products. The DBT HDS product distributions on various NiMo/ZS are shown in Table 2. The HYD/DDS ratios for various catalysts decrease in the following sequences: NiMo/ZS-25 (1.33) > NiMo/ZS-35 (1.13) > NiMo/ZS-45 (0.85) > NiMo/ZS-55 (0.75) > NiMo/ZS-65 (0.69) > NiMo/Al2O3 (0.59). The existence of B acid is beneficial to the emergence of isomerization products. kHDS of DBT on different catalysts decrease as the sequences of NiMo/ZS-45 > NiMo/ZS-35 > NiMo/ZS-25 >

23


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

NiMo/ZS-55 > NiMo/ZS-65 > NiMo/Al2O3. kHDS of NiMo/ZS-45 are all higher than those over other catalysts.

24


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Energy & Fuels

Table 2. DBT HDS product distributions on various catalysts a.

Catalyst NiMo/ZS-25 NiMo/ZS-35 NiMo/ZS-45 NiMo/ZS-55 NiMo/ZS-65 NiMo/Al2O3 a

Product selectivity (%)

kHDS (10-4 mol g-1 h-1)

THDBT

CHEB

PHDi

CHB

CPMB

CPMCH

BP

HYD/DDS ratio

9.8 11.5 14.1 9.1 8.6 7.3

3 2 1 1 1 1

1 1 1 1 1 2

3 2 2 1 1 0

36 35 32 31 30 34

11 10 8 7 7 0

3 3 2 2 1 0

43 47 54 57 59 63

1.33 1.13 0.85 0.75 0.69 0.59

HYD

DDS

Obtained at about 50% of total desulfurization degree by adjusting WHSVs (340 oC, 4 MPa, 200 mL/mL).

HYD: THDBT + CHEB + PHDi + CHB + CPMB + CPMCH; DDS: BP.

25


Energy & Fuels

3.4 Results of 4,6-DMDBT HDS Desulfurization degree, %

100

f d e

80 60 40 20

c b a 100

80

60 40 WHSV, h-1

20

0

Figure 12. 4,6-DMDBT HDS results at various WHSVs (340 oC, 4 MPa, 200

mL/mL). (a) NiMo/ZS-25, (b) NiMo/ZS-35, (c) NiMo/ZS-45, (d) NiMo/ZS-55, (e) NiMo/ZS-65, (f) NiMo/Al2O3. The 4,6-DMDBT HDS conversions of various catalysts obtained at the WHSVs from 10 to 100 h-1 are shown in Figure 12. The 4,6-DMDBT HDS efficiencies for various catalysts increase with decreasing WHSVs. Moreover, 4,6-DMDBT desulfurization degree on series catalysts follows the sequences of NiMo/ZS-45 > NiMo/ZS-35 > NiMo/ZS-25 > NiMo/Al2O3 > NiMo/ZS-55 > NiMo/ZS-65.

40

Selectivity, %

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 26 of 44

3,3'-DMCHB 4,4'-DMBP

30 20

THDMDBT Iso-MIPT 3,3'-DMBCH

10

3,3'-DMBP

0

100

80

60 40 20 WHSV, h-1

0

Figure 13. 4,6-DMDBT HDS product distributions on NiMo/ZS-45 at different

WHSVs. 26


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Energy & Fuels

Figure 13 shows 4,6-DMDBT HDS product distributions (GC spectra, Figure S8, in Supporting Information) for NiMo/ZS-45 under various WHSVs. 4,6-DMDBT HDS efficiency increase with the decrease of WHSV through isomerization (ISO) pathway rather than HYD route pathway, the typical products of which are 4,4'-dimethylbiphenyl (4,4'-DMBP) and iso-methyl-isopropyltetralin (Iso-MIPT). DDS is not the prior reaction pathway of 4,6-DMDBT HDS on NiMo/ZS-45, since the 3,3'-dimethylbiphenyl (3,3'-DMBP) selectivity is no more than 10 % under various WHSVs. The selectivity of 3,3'-dimethylbicyclohexyl (3,3'-DMBCH) increases slightly with the increasing WHSVs. Figures S7 (in Supporting Information) presented the 4,6-DMDBT HDS product distributions of various catalysts. 4,6-DMDBT HDS reaction network over series NiMo/ZS are presented in Figure S9 (in Supporting Information). There are three 4,6-DMDBT HDS pathways: DDS, HYD and ISO, respectively. DDS, S atom is directly removed through the cleavage of C-S bonds, producing the final product of 3,3'-DMBP. HYD, a hydrogenation reaction in 4,6-DMDBT occurs firstly at one of the aromatic rings and produces the intermediate products, 4,6-THDMDBT and 4,6HHDMDBT. After that, these intermediates transform into other products after the desulfurization reactions, 3,3'-DMCHEB and 3,3'-DMCHB. ISO, the methyl groups of 4,6-DMDBT are transferred firstly, 3,7-DMDBT and 3,6-DMDBT are detected in 4,6-DMDBT HDS product. The 4,6-DMDBT HDS product distributions on series catalysts are displayed in Table 3. The ISO proportions over different catalyst follow the sequences of 27


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

NiMo/ZS-25 (56 %) > NiMo/ZS-35 (52 %) > NiMo/ZS-45 (50 %) > NiMo/ZS-55 (45 %) > NiMo/ZS-65 (41 %) > NiMo/Al2O3 (0 %). kHDS of 4,6-DMDBT follow the sequences of NiMo/ZS-45 > NiMo/ZS-35 > NiMo/ZS-25 > NiMo/Al2O3 > NiMo/ZS-55 > NiMo/ZS-65.

28


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Energy & Fuels

Table 3. 4,6-DMDBT HDS product distributions on different catalysts a.

Catalyst

kHDS (10-4 mol· g-1·h-1)

Product selectivity (%) HYD

DDS

4,6-THDMDBT+ 3,3’-DMCHB 3,3’-DMBCH 4,6-HHDMDBT

3,3’-DMBP

4,4’-DMBP

IsoMIPT

Total ISO

NiMo/ZS-25

5.7

4

29

7

4

37

19

56

NiMo/ZS-35

6.9

NiMo/ZS-45

8.2

5 5

30 31

8 8

5 6

35 34

17 16

52 50

NiMo/ZS-55

4.1

NiMo/ZS-65

3.9

6 8

32 32

9 11

8 8

31 28

14 13

45 41

0

0

0

4.3 2 38 5 55 o Obtained at about 50% of total desulfurization degree by adjusting WHSVs (340 C, 4 MPa, 200 mL/mL). NiMo/Al2O3

a

ISO

HYD: 4,6-THDMDBT + 4,6-THDMDBT + 3,3'-DMCHB + 3,3'-DMBCH; DDS: 3,3'-DMBP; Total ISO: 4,4'-DMBP + Iso-MIPT.

29


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

4. DISCUSSION In this research, the as-synthesized ZS materials prepared by various aging temperatures. For elucidating the influence of different aging temperature factors on DBT and 4,6-DMDBT HDS performance over various NiMo/ZS, the structural characteristics of the supports were investigated by various characterizations. The structural characteristics of series ZS supports play a large part on DBT and 4,6-DMDBT HDS performance. Although it seems clear that the aging temperature has an impact on the structure of series ZS supports, especially on the orderliness but shows little influence on specific surface area, pore size and pore volume. The change of aging temperature can affect the orderliness of the ZS series materials and the regularity of their particles morphology, thereby affecting the activity of the final catalyst. When the aging temperature is 45 ºC, the ZS-45 material possesses long-range order and regular shape, which corresponds to the excellent performance of the corresponding catalyst. In addition, the aging temperature changes can affect the aluminum content into the framework and hydroxyl groups on the surface of the support, thereby affecting the catalyst acidity and the mutual effect between the active metal and the support. However, when the aging temperature increases, the B & L acidity decrease, which is not conducive to the improvement of the final catalyst performance. On the other side, the interaction between the support and the metal weakens when the aging temperature increases. Weak MSI favors the formation of relatively high stacking degree of MoS2 active phases, exposing more brim and edge active sites, thereby enhancing the performance of the final catalyst. Although the 30


Page 30 of 44

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Energy & Fuels

NiMo/ZS-25 catalyst possesses a higher B & L acidity, strong MSI limits its HDS activity. Similarly, the NiMo/ZS-65 catalyst has relatively weak MSI, but low B & L acidity is restrictive to its HDS performance. Therefore, the better performance of the NiMo/ZS-45 catalyst may be due to an appropriate compromise between the acidity and the MSI. Furthermore, high sulfidation degree reflected by the XPS results is also one of the main reasons for the high activity over NiMo/ZS-45. DBT HDS was chosen as one of the model reactions, of which the main products are CHB, CPMB and BP. This means that DBT HDS has experienced the two parallel pathways: DDS and HYD. B and L acid decrease in the following tendency of NiMo/ZS-25 > NiMo/ZS-35 > NiMo/ZS-45 > NiMo/ZS-55 > NiMo/ZS-65, which are in line with the order of HYD/DDS ratio over these catalysts. It is reasonable to consider that the high B & L acidity of series NiMo/ZS is conducive to leading to high proportion of HYD routes. HDS of 4,6-DMDBT was another model reaction in this study, of which the reaction pathways are: DDS, HYD and ISO, respectively. With the increase of B acidity, the whole reaction proceeds through the ISO pathway. The reason is that B acid sites caused the isomerization of 4,6-DMDBT, which changed the position of the methyl groups, thus reducing the steric inhibition of methyl groups and making the following desulfurization processes easier. The above results confirmed that the high catalytic activity of NiMo/ZS-45 in DBT and 4,6-DMDBT HDS can be attributed to the synthetic action of its good textural properties, regular morphology, moderate acidity, suitable MSI and high 31


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

sulfidation degree. In addition, the B & L acidity can influence the HDS reaction pathway and the catalytic performance of DBT and 4,6-DMDBT.

5. CONCLUSION A series of ZS micro-mesoporous composite materials were synthesized using the two-step hydrothermal crystallization method. Different aging temperatures during the synthesis process were investigated on structural properties of the support and the activity of the final catalysts. The characterization results exhibited that ZS-45 material possessed a long-range ordered pore structure and regular morphology. The corresponding catalyst NiMo/ZS-45 displayed maximal kHDS in DBT and 4,6-DMDBT HDS due to its synthetic effect of moderate acidity and the suitable MSI, appropriate dispersion, high sulfidation degree, well-ordered pore channels and uniform shape. The analysis of the product distribution over series NiMo/ZS implied that the DBT HDS underwent the two conventional path reactions of HDS: HYD and DDS, while 4,6-DMDBT HDS went through three reaction pathways: HYD, DDS and ISO. For DBT HDS, all NiMo/ZS series catalysts had higher performances than the reference NiMo/Al2O3 catalyst. The research confirmed that high B & L acidity of series NiMo/ZS led to higher rates of HYD routes. The data implies that the DDS route was the principal reaction route of DBT HDS reaction for the best active catalyst NiMo/ZS-45.

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Energy & Fuels

For 4,6-DMDBT HDS, the dominating reaction route for NiMo/ZS-45 was ISO. In addition, the 4,6-DMDBT HDS efficiencies increased with the decrease of WHSV through ISO pathway for the NiMo/ZS-45 catalyst. It could be seen through correlating the acidity of the catalysts and the reaction pathways that the high B acidity could facilitate the process of ISO route.

ACKNOWLEDGMENT This work was financially supported by the National Natural Science Foundation of China (No.21676298, U1463207 and 21503152), and CNPC Key Research Project and KLGCP (GCP201401).

ASSOCIATED CONTENT Supporting Information. TEM images (Figure S1), DBT HDS results of reference catalysts (Figure S2), DBT and 4,6-DMDBT HDS results with time on stream (Figure S3), GC spectrogram of DBT product (Figure S4), GC spectrogram of DBT product at various WHSVs (Figure S5), DBT HDS reaction network (Figure S6), GC spectrogram of 4,6-DMDBT product (Figure S7), GC spectrogram of 4,6-DMDBT product at various WHSVs (Figure S8), 4,6-DMDBT HDS reaction network (Figure S9), Chemicals needed in the experiments (Table S1). Physical properties of various ZS (Table S2), Acid distributions of various catalysts (Table S3), H2-TPR results of series catalysts (Table S4), and Mo3d XPS statistical results (Table S5).

33


Energy & Fuels

For Table of Contents Only DBT 4,6-DMDBT

10 8

TOF, h-1

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 34 of 44

6 4 2 0

NiMo/ZS-25 NiMo/ZS-35 NiMo/ZS-45 NiMo/ZS-55 NiMo/ZS-65

ZS-x represent ZSM-5/SBA-16 composite materials synthesized at different aging temperatures, in which x represent 25, 35, 45, 55 and 65 oC, respectively.

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4,6-dimethyldibenzothiophene,

and

their

hydrogenated

intermediates over bulk tungsten phosphide. J. Catal. 2015, 330, 330-343. (3) Wang, X.; Mei, J.; Zhao, Z.; Zheng, P.; Chen, Z.; Li, J.; Fan, J.; Duan, A.; Xu, C. Restrictive Diffusion in the Hydrodesulfurization over Ni-MoS2/Al2O3 with different crystal forms. Ind. Eng. Chem. Res. 2017, 56, 10018-10027. (4) Wang, X.; Mei, J.; Zhao, Z.; Chen, Z.; Zheng, P.; Fu, J.; Li, H.; Fan, J.; Duan, A.; Xu, C. Controllable Synthesis of Spherical Al-SBA-16 Mesoporous Materials with Different

Crystal

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Energy & Fuels

Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene. Ind. Eng. Chem. Res. 2018, 57, 2498-2507. (5) Lauritsen, J.; Besenbacher, F. Atom-resolved scanning tunneling microscopy investigations of molecular adsorption on MoS2 and CoMoS hydrodesulfurization catalysts. J. Catal. 2015, 328, 49-58. (6) Bui, N.; Geantet, C.; Berhault, G. Maleic acid, an efficient additive for the activation of regenerated CoMo/Al2O3 hydrotreating catalysts. J. Catal. 2015, 330, 374-386. (7) Shan, S.; Yuan, P.; Han, W.; Shi, G.; Bao, X. Supported NiW catalysts with tunable

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hydrodesulfurization of fluid catalytic cracking naphtha. J. Catal. 2015, 330, 288-301. (8) Song, H.; Wang, J.; Wang, Z.; Song, H.; Li, F.; Jin, Z. Effect of titanium content on dibenzothiophene HDS performance over Ni2P/Ti-MCM-41 catalyst. J. Catal. 2014, 311, 257-265.

(9) Wang, X.; Zhao, Z.; Chen, Z.; Li, J.; Duan, A.; Xu, C.; Gao, D.; Cao, Z.; Zheng, P.; Fan, J. Effect of synthesis temperature on structure-activity-relationship over NiMo/γ-Al2O3 catalysts for the hydrodesulfurization of DBT and 4,6-DMDBT. Fuel Process. Technol. 2017, 161, 52-61. (10) Ho, T.; McConnachie, J. Ultra-deep hydrodesulfurization on MoS2 and Co0.1MoS2: Intrinsic vs. environmental factors. J. Catal. 2011, 277, 117-122. (11) Wang, X.; Du, P.; Chi, K.; Duan, A.; Xu, C.; Zhao, Z.; Chen, Z.; Zhang, H. Synthesis of NiMo catalysts supported on mesoporous silica FDU-12 with different 35


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morphologies and their catalytic performance of DBT HDS. Catal. Today 2017, 291, 146-152. (12) Wang, X.; Zhao, Z.; Zheng, P.; Chen, Z.; Duan, A.; Xu, C.; Jiao, J.; Zhang, H.; Cao, Z.; Ge, B. Synthesis of NiMo catalysts supported on mesoporous Al2O3 with different crystal forms and the superior catalytic performance for hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene. J. Catal. 2016, 344, 680-691. (13) Hansen, L.; Ramasse, Q.; Kisielowski, C.; Brorson, M.; Johnson, E.; Topsøe, H.; Helveg, S. Atomic-scale edge structures on industrial-style MoS2 nanocatalysts. Angew. Chem. Int. Ed. 2011, 50, 10153-10156. (14) Nikulshin, P.; Ishutenko, D.; Mozhaev, A.; Maslakov, K.; Pimerzin, A. Effects of composition and morphology of active phase of CoMo/Al2O3 catalysts prepared using Co2Mo10-heteropolyacid and chelating agents on their catalytic properties in HDS and HYD reactions. J. Catal. 2014, 312, 152-169. (15) Kibsgaard, J.; Lauritsen, J.; Lægsgaard, E.; Clausen, B.; Topsøe, H.; Besenbacher, F. Cluster-Support Interactions and Morphology of MoS2 Nanoclusters in a Graphite-Supported Hydrotreating Model Catalyst. J. Am. Chem. Soc. 2006, 128, 13950-13958. (16) Sun, Y.; Wang, H.; Prins, R. Hydrodesulfurization with classic Co-MoS2 and Ni-MoS2/γ-Al2O3 and new Pt-Pd on mesoporous zeolite catalysts. Catal. Today 2010, 150, 213-217.

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SBA-16 for

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