Î³-Al2O3 Catalysts Modified Using

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Catalysis and Kinetics

Effects of the active phase of CoMo/#-Al2O3 catalysts modified using cerium and phosphorus on the HDS performance for FCC gasoline Butian Xia, Liyuan Cao, Kaiwei Luo, Liang Zhao, Xiaoqin Wang, Jinsen Gao, and Chunming Xu Energy Fuels, Just Accepted Manuscript • Publication Date (Web): 26 Mar 2019 Downloaded from http://pubs.acs.org on March 28, 2019

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Effects of the active phase of CoMo/γ-Al2O3 catalysts modified using cerium and phosphorus on the HDS performance for FCC gasoline

Butian Xia#, Liyuan Cao#, Kaiwei Luo, Liang Zhao*, Xiaoqin Wang, Jinsen Gao, Chunming Xu

State Key Laboratory of Heavy Oil Processing, China University of Petroleum (Beijing), Beijing, P.R. China, 102249

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

Email:

Liang Zhao ([email protected]);

Tel:

86-10-89739078

Fax:

86-10-69724721

ACS Paragon Plus Environment

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Abstract: The modified CoMo/γ-Al2O3 catalysts with difference Ce and/or P loading were prepared by the incipient wetness impregnation method. The catalysts were characterized using XRF, N2-adsorption-desorption, pyridine FTIR, H2-TPR, HRTEM and XPS. The effect of Ce and/or P on the active phase, acidic properties and catalytic activity of CoMo/γ-Al2O3 catalysts were investigated in detail. The results showed that phosphorus additive can slightly increase the stacking number of MoS2 slabs by reducing the metal-support interaction (MSI). And the addition of a small amount of cerium (1.75wt%) not only increased the average slab length and stacking layer number of MoS2 slabs, but also formed the new Brønsted acid sites on the support, which changes efficiently enhance thiophene HDS and olefins isomerization activity of the catalyst. These favorable effects are more obvious in the case of co-exist of cerium and phosphorus. The CoMo/γ-Al2O3P(2)Ce(1.75) catalyst exhibits the highest thiophene HDS and olefin isomerization conversion were 98.58% and 19.51%, respectively. High isomerization activity are able to inhibit the loss of gasoline octane number. Based on the above results, it can be concluded that the synergistic effect between Ce and P can achieve deep desulfurization and minimal the loss of octane number by modulating the acidity of the support and optimizing the active phase of the sulfided catalysts.

Keywords: Hydrodesulfurization, Olefin isomerization, FCC gasoline, Cerium, Preservation of octane number.


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1. INTRODUCTION With the increasingly stringent requirements for gasoline sulfur standards worldwide, the production of ultra-low-sulfur gasoline are becoming irresistible trend in many countries

1-4.

Fluid catalytic-cracked (FCC) gasoline is a major sulfur source in

commercial gasoline 5. Therefore, the efficiently removal of sulfides from FCC gasoline has received focusing attention for clean gasoline production 2. Hydrodesulfurization (HDS) of gasoline is the most widely applied and effective technology at present. Traditionally hydrodesulfurization (HDS) catalyst used alumina as a support and Co or Ni modified MoS2 crystallites as active phase. However, it is well known that traditionally HDS catalysts exhibits high hydrogenation of olefins (HYDO) activity, causing serious loss of gasoline octane number 3. In order to overcome that problem and improve the performance of HDS catalysts, it is imperative that develop a catalyst with high HDS/HYDO selectivity to maximum desulfurization and minimize olefin hydrogenation (HYDO) 6, 7. The morphology of HDS catalysts active phase directly determine the catalytic properties. So far, much efforts have been devoting to explore the relationship between the HDS/HYDO selectivity and the morphology of active phase 6-12. The active phase of HDS catalysts has two types 8: "Co-Mo-S-I" and "Co-Mo-S-II". The "Co-Mo-S-I" active phase appears as a single layer distribution, and the metal-support interaction is stronger. The "Co-Mo-S-II" active phase presents to multi-layered stacking state with weaker metal-support interaction and higher sulfidation degree. Compared with "CoMo-S-I", the "Co-Mo-S-II" active phase had the better HDS/HYDO selectivity. Generally, it is difficult to achieve ultra-deep hydrodesulfurization and preserve the octane number simultaneously on the conventional CoMo/γ-Al2O3 catalysts. The main problems of the conventional CoMo/γ-Al2O3 catalysts include that their strong metalsupport interactions (MSI) and single Lewis acid sites

13.

Strong metal-support

interactions (MSI) usually lead to decrease in HDS activity and single Lewis acid sites is beneficial to occur hydrogenation of olefins (HYDO) 14. One of the most economical and efficient way to solve these problems is to weaken the metal-support interactions (MSI) and optimize the dispersion of the acid sites by adding additives, such as


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chelating agents 15, 16, boron 17, and phosphorus 18. Actually, many studies have pointed out that adding additives is critical to improving the selectivity of HDS/HYDO. Because these additives can weaken the interaction between active metals and support, which in favor of forming more CoMoS-II phase, and hence an increase in catalytic performance. In addition, many studies also have pointed out that the HDS/HYDO selectivity could be modulated by the length of MoS2 slabs because long MoS2 slabs exhibited high HDS/HYDO selectivity

19-21.

Li

20

indicated that the slab length was more important

than stacking number of MoS2 crystallite for improving the HDS/HYDO selectivity of CoMo/Al2O3 catalysts. According to literature reports, the slab length of MoS2 crystallite was tuned usually by adding alkali metals such as sodium, potassium and magnesium into catalysts 20, 22-26. P.V. Nikulshin found that the introduction of a higher amount of potassium into CoMo/Al2O3 catalyst resulted in an increase in metal sulfuration and the formation of large-sized KCoMoS active phase. K-modify catalysts shown a slightly decrease in HDS reaction and a sharply decrease in hydrogenation of olefins (HYDO) reaction, which cause a proportional increase in HDS/HYDO selectivity

23.

Similarly, Fan et al. 6 reported that synergism effect of potassium and

phosphorus on commercial CoMo catalysts. The conclusion shown only K modified catalyst presented poor HDS activity, however, doping K and P into CoMo catalyst would adjust the acid strength and promote the formation of mildly MoS2 slabs length, so that the HDS and HYDO activities of KCoMoP/Al2O3 catalyst reach a good balance. Badoga revealed 25 that the addition of sodium to the CoMo catalysts led to seriously decrease in both HDS and HYDO activities. In summary, these publications suggest that alkali metals as modifier can slightly increases the HDS/HYDO selectivity, however, they almost always come at the expense of reducing the HDS activity, which is not conducive to the ultra-deep desulfurization of FCC gasoline. Therefore, in order to obtain a catalyst with both ultra-deep desulfurization and high HDS/HDYO selectivity, searching new additives to optimize active phase and acidic properties of CoMo catalysts is worth studying. Cerium as a well-known catalytic additive has a strong affinity for organic sulfides


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26-28.

Moreover, cerium is one of the common elements that regulate the acidity of

zeolite. Li et al. 29 indicated Ce ion-exchanged USY zeolite had higher Brønsted acid sites and higher BAS/LAS ratio. However, as far as we know, few reports have explored the influence of Ce on activity of CoMo/γ-Al2O3 catalysts. In this study, through cerium and phosphorus as modifiers, a series of modified CoMo/γ-Al2O3 catalysts were prepared using incipient impregnation method. The catalytic performance of all prepared catalysts were evaluated by hydrotreating of model gasoline. Then we investigated the effect of adding Ce to catalyst on the morphology of the active phase and acidic properties, and the essence of modification of Ce on the catalytic performance for HDS catalysts been rationally suggested. The results of this paper hope to provide a better reference value for the design and improvement of HDS catalysts for FCC gasoline. 2. Expermiental 2.1. Catalysts preparation γ-Al2O3 was pulverized and sieved to a size of 200-400 mesh. Using cerium nitrate (Aladdin, >99.9%) as precursor, a series of containing different amounts of CeO2 (0.75, 1.75, 2.50 wt%) modified γ-Al2O3 was prepared by incipient wetness impregnation. And the obtained modified γ-Al2O3 were aged at room temperature for 12 hours, dried at 120 for 6 hours, and calcined at 550 for 4 hours. Such obtained samples were donated separately as Al2O3Ce(x) (x is cerium loading) respectively. P-modified γ-Al2O3 containing 2wt% P2O5 was prepared also via incipient wetness impregnation with aqueous phosphoric acid solution (Aladdin, >99%), and then aging, dried and calcined according to the same conditions as above. Such obtained samples were donated separately as γ-Al2O3P(2). Then γ-Al2O3P(2) was further modified by cerium nitrate and the content of Ce was 1.75 wt%. The obtained support was denoted as γAl2O3P(2)Ce(1.75). All of the above Ce- and P- modified γ-Al2O3 were used to prepare CoMo catalysts by incipient impregnation method. The preparation process as follows: firstly, the citric acid (CA) as a chelating agent was dissolved in deionized water at the room temperature. The basic cobaltous carbonate (2CoCO3·3Co(OH)2·H2O, Aladdin, China) was slowly


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added to the CA solution. Next, the hexaammonium molybdate ((NH4)6Mo7O24, Aladdin, China) was added to the Co-CA complex solution to synthetic the impregnation solution, which was used to impregnate modified supports. After impregnation process, all catalysts were aged at room temperature for 12 hours and dried at 120°C for 6 h. The elemental analysis (Ce, P, Mo, Co,) of all the catalysts were determined by X-ray fluorescence spectroscopy (XRF) on an Axiosm AX instrument (Table S1). 2.2. Characterization of catalysts 2.2.1 BET The pore structure properties of the oxidized catalysts were determined by N2 adsorption–desorption isotherms on an automated gas sorption analyzer (Micromeritics Tristar 3020). The specific surface areas were obtained by the Brunauer–Emmett– Teller formula. The pore size distributions and total pore volumes were measured by the BJH method. 2.2.2 HRTEM The high-resolution transmission electron microscopy (HRTEM) images of the presulfided catalysts (before used in reaction) were obtained on a micro-gate carbon film mounted by a Philips Tecnai G2 F20 STWIN microscope. And 20-25 representation images and at least 400 slabs were counted for each catalyst. Combining the statistical results with the following formulas to calculate the average slab length (𝐿) and stacking number (𝑁) 23:

 xL L=  x  xN N=  x n

i 1 i n

i

（1）

i 1 i

n

i 1 i n

i

（2）

i 1 i

where Li and Ni are the length of MoS2 slab or the number of stacking layers, xi is the number of slabs with length Li. The MoS2 dispersion (D) represents the ratio of active Mo atoms at the edge and corner positions to total Mo atoms. The formula for calculating the MoS2 dispersion (D) is as follows 20:


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M  M Oc D  Oe  MOT



t i 1

6ni - 6

 i1 3ni 2 - 3ni  1 t

（3）

where ni is the number of Mo atoms on the side of a single MoS2 slab, as calculated by its length (L=3.2(2ni-1)Å) 20. And t is the total stacking layer number of MoS2 slabs. The formula for calculating edge-to-corner ratio of MoS2 slab is as follows 30:

f e Moe 10  L / 3.2  3   f c Mov 2

（4）

where 𝐿 is the average length of MoS2 slab (nm). 2.2.3 X-ray photoelectron spectroscopy (XPS) The pre-sulfided catalysts (before used in reaction) were analyzed by XPS. The XPS spectra were obtained on a PHI-1600 ESCA spectrometer. The measurement conditions were as follows: the radiation source was Al Kα, the power was 0.4 eV, the internal standard was the binding energy of the carbon C1s (Eb=284.8 eV). The spectra of Co2p and Mo3d XPS were fitted by XPSPEAK 4.1 software. The relative contents of CoMoS, CoxSy, Co2+, MoS2, Mo5+ and Mo6+ species were obtained by calculating the peak area. 2.2.4 H2-TPR Analysis of H2 temperature-programmed reduction (H2-TPR) of oxidized catalysts on a Quantachrome apparatus (Auto-sorb, USA). Prior to the TPR measurement, the oxidized catalysts were pretreated at 400°C for 2 h under N2 flow and cooled to room temperature. Then switched to H2/Ar mixed gas (10 v% Ar) at flow rate of 40 ml/min, the sample was heated to 1000°C at the rate of 10°C/min, TCD detector detects recording signal. 2.2.5 Py-FTIR The acidic properties of the oxidized catalysts were measured by Fourier transform infrared (FTIR) of adsorbed pyridine. The pyridine-FTIR spectra of the catalysts were collected at 200 °C and 350 °C using a FTS-3000 spectrophotometer. The 200 °C spectra were used to calculate the amount of total acid sites and 350 °C spectra were used to calculate the amount of the strong acid sites. The formulas for calculating the amount of acid are as follows 42:


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CB 

1.88  AB  R 2 m

(5)

CL 

1.42  AL  R 2 m

(6)

where CB and CL are the acid amount of B acid and L acid (mmol·g-1). AB and AL represent the peak area of the absorption peaks of B acid and L acid, respectively. And R is the radius (cm) of the sample tablet. m is the mass of the sample (mg) 2.3 Examination of the catalytic properties The HDS reactions of catalysts were evaluated in a fixed-bed reactor loading with 0.5 g catalysts (40–60 mesh). All the catalysts need to be pre-sulfided in 3wt% CS2 solution, pre-sulfided reactions were carried out in two steps at 230°C 1 h and 320°C 4h. After pre-sulfided, we evaluated the catalytic performance of the catalysts by model gasoline hydrogenation reaction firstly. The composition of model gasoline include thiophene (1000ppm S), 1-hexene (30 wt.%), n-heptane (70 wt.%). The reaction conditions are as follows: LHSV= 3h−1, T = 270 °C, P = 2 MPa, H2/feed = 300. Then chose the best activity and selectivity catalyst to test in hydrotreating of heavy fraction in FCC gasoline produced by Shandong Jingbo Petrochemical Co., Ltd (Distillate fraction: 100°C~185°C, Sulfur content：766 ppm, olefin content：32 wt.%, RON: 92.1).Hydrotreating of FCC gasoline was carried out in the following conditions: LHSV= 2.5 h−1, T = 250-290 °C, P = 2 MPa, H2/feed = 300. The formulas for calculating the activities and selectivity of the catalysts are as follows 22: HDS % 

HYDO% 

S f  Sp Sf

100

O f  Op Of

HDS / HYDO 

100

ln(1  HDS %) ln(1  HYD%)

（7）

（8）

（9）

where 𝑆𝑓 and 𝑆𝑝 are the mass fractions of sulfides in the feedstock and products,


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respectively. And 𝑂𝑓 and 𝑂𝑝 are the mass fractions of olefins in the feedstock and products, respectively. The rate constants of the pseudo-first-order reaction of thiophene HDS and 1-hexene HYDO were obtained by the following equation 23: T K HDS 

H K HDYO 

FT 1 ln( ) W 1  xT

（10）

FH 1 ln( ) W 1  xH

（11）

where 𝑘𝑇𝐻𝐷𝑆 and 𝑘𝐻 𝐻𝑌𝐷𝑂 are the rate constant of thiophene HDS and 1-hexene HYDO (mol g-1 h-1), respectively. FT and FH are the feeding rate (mol h-1). W is the weight of the catalyst (g). 𝑥𝑇 and 𝑥𝐻 are the conversion of thiophene and 1-hexene (%), respectively. The turnover frequencies (TOF, s-1) was tested under the following conditions: T = 220 °C, P=2 MPa, H2/feedstock = 200, LHSV = 6 h-1. And the formula for calculating TOF value is as follows 23, 31: T TOFHDS 

FT  xT  MrCo W  CCoMoS  3600

（12）

H TOFHDYO 

FH  xH  MrCo W  CCoMoS  3600

（13）

Where FT and FH are the feeding rate (mol h-1). 𝑥𝑇 and 𝑥𝐻 are the conversion of thiophene and 1-hexene (%), respectively. 𝑀𝑟𝐶𝑜 is the molar mass of cobalt (58.9 g/mol). W is the weight of the catalyst (g). 𝐶𝐶𝑜𝑀𝑜𝑆 is the CoMoS phase amount (wt.%) 23, 31.

3. Results 3.1 BET The N2 adsorption–desorption isotherms of γ-Al2O3 and oxidized catalysts are shown in Fig.1. For the γ-Al2O3, the adsorption–desorption isotherms exhibits type IV curve, which has the H4 hysteresis loop with the mesoporous structure. However, the adsorption–desorption isotherms of the CoMo catalysts exhibit an H2 hysteresis loop with the mesoporous structure 31. It is explained that the active metals have a significant


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influence on the pore structure of the γ-Al2O3. Table 1 shown the textural and structural characterization results of the samples. Compared with the CoMo/γ-Al2O3 catalyst, the introduction of cerium or phosphorous lead to apparently decrease in the textural characteristics (SBET, Vmes, and Dpore). This reason may be caused that the catalysts prepared by the impregnation method will decompose into the corresponding oxides during the roasting process, resulting in the specific surface decrease and blocked the pores and channels 32. In addition, with the increase of Ce loading, the N2 adsorption– desorption results show that the microporous volume of catalyst reduce slightly from 0.007 to 0.004 cm3g-1, while the mesoporous volume decrease dramatically from 0.40 to 0.30 cm3g-1, pore volume narrow down from 0.39 to 0.30 cm3g-1 and pore size narrow down from 7.3 to 6.0 nm. These results indicate that the excessive Ce will block the mesoporous structure, which resulting in a decrease in the average pore size. It is obvious from the fact above that excessive Ce amounts seriously blocked the pores and channels.

Figure 1. The nitrogen adsorption–desorption isotherms of γ-Al2O3 and prepared catalysts. (a) CoMo/γ-Al2O3, (b)CoMo/γ-Al2O3P(2), (c) CoMo/γ-Al2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γ-Al2O3Ce(2.5), (f) CoMo/γ-Al2O3P(2)Ce(1.75). Table 1. Structural characterization results of the γ-Al2O3 and all the catalysts


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Samples

SBET (m2g-1)

Vmes (cm3g-1)

Vmic (cm3g-1)

Dpore (nm)

γ-Al2O3

235

0.60

0.006

10.3

CoMo/γ-Al2O3

215

0.40

0.007

7.6

CoMo/γ-Al2O3P(2)

206

0.37

0.007

7.3

CoMo/γ-Al2O3Ce(0.75)

213

0.38

0.006

7.3


207

0.36

0.004

6.9


201

0.30

0.004

6.0

CoMo/γ-Al2O3P(2)Ce(1.75)

203

0.35

0.004

6.9

3.2 Pyridine-FTIR In this study, one of the most important aims is to explore the effect of acid properties on catalyst performance in hydrogenation reactions. The pyridine-FTIR spectra are shown in Fig. 2. According to the literature 31, 33, the characteristic peaks at 1452, 1575, and 1622 cm-1 are identified to Lewis acid sites, the characteristic peak at 1542 cm-1 is considered to Brønsted acid sites, and the peak at 1493 cm-1 is appointed to combination of Lewis and Brønsted acid sites. There are only Lewis acid sites and no Brønsted acid sites in the spectra of the γ-Al2O3, CoMo/γ-Al2O3 and CoMo/γ-Al2O3P(2) catalysts, on the contrary, the peak at 1542 cm-1 is observed in the spectra of the CoMo/γ-Al2O3Ce(x) and CoMo/γ-Al2O3P(2)Ce(1.75) catalysts, indicating that the presence of Brønsted acid sites in these catalysts. This result could be explained that the formations of Brønsted acid sites are related to the introduction of cerium, which may be attribute to the Ce incorporation into the Al-OH band. Furthermore, the amount of Brønsted and Lewis acid sites were calculated by formula (5) and (6), and the results were summarized in Table S2. It can be known that the phosphoric acid modified CoMo/γ-Al2O3 catalyst leads to the amount of total acid sites decrease from 103.3 to 93.0 umol g-1 and the medium and strong acid sites decrease from 51.5 to 42.4 umol g-1. These results are attributed to the interaction between phosphoric acid and hydroxyl groups, which result in the consumption of more hydroxyl groups 24, 25. With the increase of loading amount of cerium, the amount of LASs decrease and the amount of BASs almost unchanged, which makes the BAS/LAS ratio lightly increases.


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Figure 2. The pyridine FTIR spectra of γ-Al2O3 and oxidized catalysts. (a) CoMo/γ-Al2O3, (b) CoMo/γ-Al2O3P(2), (c) CoMo/γ-Al2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γAl2O3Ce(2.5), (f) CoMo/γ-Al2O3P(2)Ce(1.75). (A) 200 °C and (B) 350 °C

3.3 H2-TPR In order to reveal the strength of the metal-support interaction (MSI) 35, the H2-TPR of all catalysts were tested and results were shown in Fig.3. It can be seen that there are two major peaks in the range of 460-660 °C and 690-793 °C, respectively. The reduction peak of low temperature is assigned to the process of reducing MoO3 species


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to the low coordination Mo4+ species (Mo6+→HxMoO3→Mo4+), and the reduction peak of high temperature is ascribed to the entirely reduction process of the tetrahedral coordination Mo4+ species (Mo4++2e-→Mo0) 31. The CoMo/γ-Al2O3 catalyst show the highest reduction temperature, which indicates that metal oxides on the support are difficult to be reduced. Compared with the CoMo/γ-Al2O3 catalyst, the low-temperature peak of the modified catalysts by cerium slightly shift to the lower temperature, which indicates that the metal–support interaction (MSI) on the catalyst is weakened and metal oxides are easier to be reduced. The low temperature characteristic peak of CoMo/γAl2O3P(2) stay almost unchanged, but the high temperature characteristic peak shifts to the lower temperature, indicating that tetrahedral coordination Mo4+ species is more easier reduced after the addition of phosphorus. The reason may be that after the phosphorus modification, a part of the strong acid sites on the support is neutralized, which increases the dispersion of the active metal, thereby weakening metal-support interaction (MSI)

23.

With the synergism of cerium and phosphorus, The CoMo/γ-

Al2O3P(2)Ce(1.75) catalyst shows the lowest reduction temperature, suggesting that the synergistic effect of phosphorus and cerium can further boost to the sulfidation of Mo species.

Figure 3. H2-TPR curves of the oxide catalysts: (a) CoMo/γ-Al2O3, (b) CoMo/γ-Al2O3P(2), (c) CoMo/γ-Al2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γ-Al2O3Ce(2.5), (f) CoMo/γ-


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Al2O3P(2)Ce(1.75).

3.4 HRTEM The typical morphology of MoS2 slabs of the sulfided catalysts were displayed in Fig. 4, wherein the black linear-stripes belongs to MoS2 slabs 20-23. The distributions of the slab length and the stacking number of MoS2 slabs are shown in Fig. 5, and statistical results were listed in Table 2. Compared with the CoMo/γ-Al2O3 catalyst, it is clear that addition of cerium can significantly increase the slab length and stacking layer number of MoS2 slabs, but has no obvious effect on the MoS2 dispersion (D). With the increase of cerium loading, the average slab length increase from 3.0±0.1to 3.7±0.1 nm and the average stacking number increase from 2.0±0.1 to 2.5±0.1. These results can be explained as follows: With an increasing cerium content on the CoMo/γAl2O3 catalysts, cerium as an electron donor could continuously contribute electrons to MoS2 slabs and thereby strengthened the electronic cloud density around Mo atoms. Meanwhile, the electron donor of Ce also can act as an adhesive between two adjacent layers to consolidate the multi-layer stacking of MoS2 slabs and form more edge sites in the MoS2 slab

36, 37.

Interestingly, the CoMo/γ-Al2O3P(2)Ce(1.75) catalyst has a

higher stacking number (2.6±0.1) and a longer average length (3.8±0.1 nm) than other modified catalysts, which indicates that there is a combined action between cerium and phosphorus on the catalyst.


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Figure 4. HRTEM images of the sulfide catalysts: (a) CoMo/γ-Al2O3, (b) CoMo/γ-Al2O3P(2), (c) CoMo/γ-Al2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γ-Al2O3Ce(2.5), (f) CoMo/γAl2O3P(2)Ce(1.75).


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Figure 5. Distributions of slab lengths (A) and stacking number (B) of the sulfide catalysts Table 2. HRTEM analysis results of the sulphided catalysts Samples

L(nm)

N

D

(fe/fc)Mo

CoMo/γ-Al2O3

3.0±0.1

2.0±0.1

0.31

3.19

CoMo/γ-Al2O3P(2)

3.0±0.1

2.2±0.1

0.31

3.19


3.2±0.1

2.1±0.1

0.30

3.50


3.5±0.1

2.4±0.1

0.28

3.97


3.7±0.1

2.5±0.1

0.28

4.28

CoMoP/γ-Al2O3P(2)Ce(1.75)

3.8±0.1

2.6±0.1

0.28

4.44

3.5 XPS The Mo 3d and Co 2p XPS spectra of the sulfided catalysts were shown in Figs. 6 and 7. The binding energy of various species are listed in Table. S3 (In supporting information). The detailed compositions of sulfided catalysts are summarized in Table 3. According to the literature, there are three double peaks of the Mo 3d spectra15, 23, 37: (1) the doublet of binding energies around 229.1±0.1 and 232.3±0.1eV are connected to Mo4+ species of the MoS2 phase, (2) the doublet of binding energies at 231.2±0.1 and


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235.2±0.1 eV are related to MoSxOy species, (3) the doublet of binding energies at 233.2±0.1 and 236±0.1 eV are correlated with Mo6+ species. The Co 2p XPS spectra shown in Fig.7. The peaks at about 781.1±0.1 and 793.9±0.1 eV are connected with CoMoS phases; the binding energies at about 778.5±0.2 and 793.2±0.2 eV are related to Co9S8 species; and the peaks at 783.1±0.2 and 796.5±0.2 eV are assigned to Co2+ species.

Figure 6. Mo3d XPS spectra recorded for sulfided catalysts: (a) CoMo/γ-Al2O3, (b) CoMo/γ-


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Al2O3P(2), (c) CoMo/γ-Al2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γ-Al2O3P(2.50), (f) CoMo/γ-Al2O3P(2)Ce(1.75) Table 3. The XPS characterization results of sulfide catalysts Co distribution (%)

Mo distribution (%)

Samples CoMoS

Co9S8

Co2+

MoS2

MoSxOy

Mo6+

CoMo/γ-Al2O3

43.6

39.2

18.2

49.6

25.1

25.3

CoMo/γ-Al2O3P(2)

46.5

34.5

19.0

52.9

23.4

23.7


45.7

35.7

19.6

56.5

20

23.5


48.2

32.5

19.3

58.3

18.6

23.1


47.1

37.0

18.9

59.1

18.5

22.4


54.4

25.5

20.1

62.7

17.0

22.3


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Energy & Fuels

(a)

(b)

(c)

(d)

(e)

(f)

Figure 7. Co2p XPS spectra recorded for sulfided catalysts: (a) CoMo/γ-Al2O3, (b) CoMo/γAl2O3P(2),

(c)

CoMo/γ-Al2O3Ce(1.75),

(d)

CoMoP/γ-Al2O3P(2)Ce(1.75),

(e)

CoMo/γ-

Al2O3Ce(2.50), (f) CoMo/γ-Al2O3P(2)Ce(1.75)

The Mo 3d spectra were peak-differentiating and imitating. The relative amounts of MoS2, MoOxSy and MoO3 species are listed in Table 3. It can be seen that the sulfided CoMo/γ-Al2O3 catalyst exhibits the lowest amount of MoS2 (49.6%) and the highest


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amount of MoO3 species (25.3%). With the increase of cerium loading, the relative amount of MoS2 species increase together, which indicates that the addition of cerium can improve Mo sulfide degree. In addition, XPS characterization also show that when phosphorus and cerium coexisted on the catalyst, the modified catalyst display the highest relative amount of MoS2 (61.7%) and the lowest relative amount of MoO3 species. which because the synergistic effect between cerium and phosphorus on the catalyst further weaker the metal-support interaction (MSI). The Co 2p spectra were decomposed, and the Table 3 listed the relative contents of CoMoS, Co9S8, Co2+species. As we can see that after phosphorus modification, the relative content of CoMoS species increases from 43.6% to 46.5%, indicating that phosphorus additive can facilitate more Co atoms insert into the MoS2 slabs, thus forming more CoMoS species. Adding cerium to the catalyst also increases the relative amount of CoMoS species, moreover, with the increase of Ce loading, the relative amount of CoMoS species increases first and then decreases, and the relative content of Co9S8 species has an opposite variation trend. More interestingly, both the highest Co sulfidation and the highest CoMoS active phase content are observed over CoMoP/γ-Al2O3P(2)Ce(1.75) catalyst, which show highly consistency with H2-TPR and HRTEM results. 3.6 HDS performance of catalysts 3.6.1 Results of the HDS of model fuel In order to investigate the effect of cerium and phosphorus as additives on the HDS performance, all catalysts were performed HDS reaction using model fuel as feedstock, furthermore, the CoMo/γ-Al2O3P(2)Ce(1.75) catalyst was also selected to test by the real FCC gasoline feedstock. As two main indicators, the HDS activity of thiophene and the change of octane number were used to evaluate the performance of catalysts. Table 4 lists the HDS reaction results using model fuel as feed. With the addition of phosphorus, the conversion of thiophene increases slightly (from 86.41% to 90.73%), while the conversion of 1-hexene decreases from 73.22% to 65.24%, so that the HDS/HYDO selectivity factor increased from 1.52 to 2.25. With the increase of cerium loading, the thiophene conversion continuously increases but the catalyst selectivity


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increases first and then decreases. The CoMo/γ-Al2O3P(2)Ce(1.75) catalyst exhibits the highest selectivity and conversion of isomerization, indicating that synergistic effect between cerium and phosphorus can further optimize the acidic properties and the active phase of the catalysts. Table 4. Hydrotreating products of model fuel (30% 1-hexene, 1000ppm thiophene, Heptane as solvent) for catalysts Conversion of Catalyst

HDS%

HYDO%

Selectivity

CoMo/γ-Al2O3

86.41

73.22

1.52

2.07

CoMo/γ-Al2O3P(2)

90.73

65.24

2.25

2.43


91.44

68.46

2.13

9.37


95.45

60.04

3.36

16.00


95.67

65.37

2.98

17.60


98.58

58.62

4.76

19.51

isomerization (%)

In addition, we got an interesting result that the composition of hydrogenated products on CoMo/γ-Al2O3Ce(x) had clearly differences from the one on CoMo/γAl2O3. To illustrate this, the results of hydrocarbon product distribution are shown in Table 5. It is noticed that the highest quantity of hexane was obtained for CoMo/γAl2O3, and no iso-paraffins and branched olefins were observed for CoMo/γ-Al2O3 catalyst. Adding of cerium to the catalysts can reduce hydrogenation saturation of 1hexene, meanwhile generating more isomerization products include iso-paraffins and branched olefins. Interestingly, the higher loading of cerium, the higher content of isoparaffins and branched olefins. As we can know from Table5, the reaction path way of 1-hexene on CoMo/γ-Al2O3 catalyst in the following two ways 38: (1) hydrogenation saturation of 1-hexene to hexane; (2) isomerization of double bond of 1-hexene to form internal olefins. However, the reaction path way of 1-hexene on CoMo/γ-Al2O3Ce(x) have three ways: (1) hydrogenation saturation of 1-hexene and its isomers to


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corresponding paraffins; (2) isomerization of double bond of a little of 1-hexene turn into internal olefins; (3) isomerization of skeleton of 1-hexene to form different branched olefins. It is well known that branched olefin has lower activity and higher octane number in hydrogenation process than that of terminal linear olefin, so that the formation of branched olefin is profitable. Table 5. The results of hydrocarbon product distribution in hydrotreating of model fuel n-hexane

Iso-paraffin

Internal olefins

Branched olefins

(wt.%)

(wt.%)

(wt.%)

(wt.%)

CoMo/γ-Al2O3

21.96

-

0.62

-

CoMo/γ-Al2O3P(2)

20.56

-

0.73

-


20.52

0.65

0.76

1.4


18.00

1.86

0.74

2.2


18.59

1.90

0.69

2.7


17.58

1.79

0.77

3.3

Samples

3.6.2 Results of the HDS of FCC gasoline The Fig.8 presents the effect of reaction temperatures on HDS, HYDO and ∆RON of FCC gasoline over CoMo/γ-Al2O3 and CoMo/γ-Al2O3P(2)Ce(1.75) catalysts. The evaluation results of FCC gasoline are good agreement with the previous characterizations results and HDS results of model fuel. It can be seen that the cerium and phosphorus modified catalyst have higher potential in preservation of octane number. Moreover, CoMo/γ-Al2O3P(2)Ce(1.75) has a higher hydrodesulfurization activity than that of CoMo/γ-Al2O3 catalyst under the same reaction temperature. The hydrogenation product distribution of the two catalysts shows a significant difference as temperature rose. For CoMo/γ-Al2O3 catalyst, the olefins content reduces sharply when the temperature rises, resulting in octane number loss than 3.5 units at 280 °C, which is not suitable for hydrotreating of FCC gasoline. For CoMo/γ-Al2O3P(2)Ce(1.75) catalyst, as the temperature rises in favor of the formation of isomerized products, loss


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of octane number is compensated due to the formation of high octane components such as iso-paraffins and branched olefins in the hydrogenation process. According to calculations, loss of octane number for CoMo/γ-Al2O3P(2)Ce(1.75) catalyst at 280 °C is about 1 unit.

Figure 8. Dependence of HDS, HYDO and ∆RON of FCC gasoline hydrotreatment on temperature over CoMo/γ-Al2O3 and CoMo/γ-Al2O3P(2)Ce(1.75) catalysts

4. Discussion


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4.1 Effect of addition of Ce on the morphology of active phase In this work, the morphology of active phase of sulfide catalysts was exhibited by HRTEM and XPS methods. From the images of HRTEM results, it could be found that stacking number and average length of MoS2 slabs slightly increases as the increase loading amount of Ce. As we know, the longer average slab length represent that the higher edge/corner ratio of a MoS2 slab (Equation (4)). Furthermore, it is speculated that the edge sites of MoS2 slab is the active site of HDS reaction and the corner sites of MoS2 slab is responsible for the HYDO reaction according to the density functional theory (DFT) calculations

40,

so that appropriate increase edge/corner ratio could

improve HDS/HYDO selectivity. XPS analysis confirm that with small Ce amounts into catalysts will increase the relative amount of CoMoS species. By comparing XPS and HRTEM data, it can be clearly seen that the addition of cerium can optimize the morphology of active phase. Based on the above results, we speculated a schematic about cerium influence on the active phase is shown in Fig. 9. Using cerium as a modifier enlarges the size of the MoS2 crystallites layer and increases the stacking layer number. The higher stacking layer number and the longer slab length, the more edge active sites, which promote the HDS activity and suppress the HYDO reactions significantly. However, in this work, we discovered that when loading the excessive amount of Ce (2.50 wt.%), although the average length of MoS2 slabs of the catalyst still advantage, the selectivity of the catalyst relatively decreased. Someone has reported

24

that the HDS/HYDO selectivity of the catalyst is linearly related to the

amount of CoMoS active phase catalyst. By combining with Table 3 and Table 4, it can be found that with the Ce loading increases from 1.75 to 2.5 wt%, the CoMoS content in the sulfided catalyst decreases from 48.2 to 47.1 and the HDS/HYDO selectivity decreases from 3.36 to 2.98. These results indicate that excessive Ce will decrease the content of the CoMoS phase, resulting in a decrease in HDS/HYDO selectivity of the catalyst.


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Figure 9. Schematic illustration of cerium influence on the active phase morphology

To investigate the effect of Ce on catalytic performances, we speculated that the rate constant and TOF number of thiophene HDS and1-hexene HYDO over catalysts (Table 6). The CoMo/γ-Al2O3 catalyst had the lowest thiophene HDS rate constant of 3.0 mol g-1 h-1 and the highest 1-hexene HYDO rate constant of 293 mol g-1 h-1. With the rise of Ce content, HDS rate constants increase from 3.0 to 5.0 mol g-1 h-1, HYDO rate constants decrease from 293 to 270 mol g-1 h-1. Figure.10. shows the relationship of TOF number in thiophene HDS and1-hexene HYDO on the amount of Ce addition. It can be observed that with the increase of Ce loading, the values of TOFHDS increase firstly and then decrease, and the values of TOFHYDO decrease linearly. The experimental results support the hypothesis that Ce has ability to promote HDS activity and inhibit HYDO reaction by modifying the morphology of active phase. As shown is Fig. 10, the values of TOFHDS for CoMo/γ-Al2O3P(2)Ce(1.75) catalyst higher than the CoMo/γ-Al2O3Ce(1.75) catalyst, suggesting that use Ce and P simultaneously as modifiers can optimize the CoMoS active phase and further promote the HDS activity. Table 6. Catalytic performances of CoMo/γ-Al2O3 and Ce modified catalysts in hydrotreating of model gasoline. Conversion (%) a Samples

CoMo/γ-Al2O3 CoMo/γ-Al2O3 Ce(0.75)

KHDS×105

KHDYO×105

TOFHDS

TOFHYDO

(mol g-1 h-1)

(mol g-1 h-1)

(×10-4 s-1)

(×10-4 s-1)

Thiophene

1-Hexene

17.2

25.4

3.0

293

1.15

189

25.6

25.2

4.7

289

1.60

174


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CoMo/γ-Al2O3 Ce(1.75) CoMo/γ-Al2O3 Ce(2.50) CoMo/γ-Al2O3 P(2)Ce(1.75) a:

Page 26 of 54

26.4

25.1

4.9

289

1.63

169

26.0

23.2

5.0

270

1.58

164

30.1

23.9

5.7

273

1.68

166

Reaction conditions: T = 220 °C, P=2 MPa, LHSV = 6 h-1, H2/feedstock = 200.

Figure 10. The relationship of TOF number in HDS and HYDO on the amount of Ce

loading 4.2 Effect of the acidic properties on catalytic performance To further investigate the influence of acidic properties of catalysts on catalytic performance, comparison of CoMo/γ-Al2O3 and Ce modified catalysts showed that the latter have higher activity in HDS and isomerization of olefins. Fig. 11 shows the linear dependence of HDS activity and conversion of isomerization on the BAS/LAS ratio for the modified catalysts during the hydrotreating of thiophene and 1-hexene. As can be seen from picture, increasing the BAS/LAS ratio appropriately was beneficial to improve HDS activity and the conversion of olefin isomerization. According to reports in the literature 17, 33. Brønsted acid sites are able to strength the electron deficiency of


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active metals through electron-induced effect, improving the π adsorption of thiophene and enhancing the HDS efficiency. For the isomerization reaction, it occurs at the combined effect of Brønsted and Lewis acid sites. Brønsted acid sites as the primary reactive sites can act as isomerization active sites directly. Lewis acid sites usually as a secondary reaction center in the isomerization reaction

41,

so that suitable increase

BAS/LAS ratio would reduce the possibility of side reactions and improve the selectivity of isomerization. But the structure-activity relationship between BAS/LAS ratio and the catalyst activity still need further exploration.

Figure 11. Dependence of HDS% and conversion of isomerization (%) of model gasoline hydrotreating on BAS/LAS ratio.

In addition, the amount of Lewis acid on the catalyst have a remarkable effect on the olefins saturation activity. Olefins are easily adsorbed on the Lewis acid sites and occur a hydrogen saturation reaction, therefore, the hydrogen saturation activity of olefins increases with the increase of Lewis acid sites 41. As shown in Fig. 2 and Table 5, the CoMo/γ-Al2O3 possess the highest olefins saturation activity due to the existence of a large of Lewis acid sites, and does not has obvious isomerization function because of the absence of Brønsted acid sites on the support. The addition of Ce result in the acidic


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properties of the catalyst were changed. Ce as an additive formed new Brønsted acid sites and neutralized part of the Lewis acid sites on the surface of catalyst, so that cerium modified catalysts possess better HDS and olefin isomerization efficiency. The formation mechanism of the Brønsted acid centers is speculated in Fig.S1. The formations of Brønsted acid sites are related to the Ce incorporation into the Al-OH band. Cerium has a lower electronegativity than aluminum (χ𝐶𝑒=1.12, χ𝐴𝑙=1.61, provided by the PDG), this then cerium is used as an electron donor to donate electron for Al-OH, strengthen the Al-O band energy and weaken the O-H band energy. Therefore, Brønsted acid sites are formed easily by the O-H bond breaks to release Hprotons. Compared with CoMo/γ-Al2O3Ce(0.75) and CoMo/γ-Al2O3-P(2)Ce(1.75) catalyst, the latter has a higher BAS/LAS ratio value meanwhile have more excellent HDS and olefin isomerization activities. It is illustrated that use of Ce and P to modify catalyst can obtain moderate acid sites distribution, and thus effectively promote the improvement of catalyst performance. 5. Conclusion In this paper, Ce and P were used as modifiers to modify the CoMo/γ-Al2O3 catalysts, and the physicochemical properties and catalytic properties of the modified catalysts were tested. The results shown that the addition of P can modulate the active phase by reducing the metal-support interaction, thus improving the HDS activity of the catalyst. The addition of Ce not only beneficial to increase the average length and the stacking number of MoS2 slab, but effectively adjust the acidic properties of the support with forming new Brønsted acid sites and increasing BAS/LAS ratio. Therefore, Ce modified catalysts have excellent isomerization performance. Moreover, with the harmonious action of Ce and P on the catalyst, the characterization results show that CoMo/γ-Al2O3P(2)Ce(1.75) catalyst has suitable acidity and the lowest metal-support interaction, and hydrogenation results of FCC gasoline also proved CoMo/γAl2O3P(2)Ce(1.75) catalyst have excellent HDS activity and isomerization activity. It can be concluded that synergistic effect between Ce and P on HDS catalysts can achieve deep desulfurization and protect the octane number of gasoline simultaneously.


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Acknowledgments The authors acknowledge the supports from the National Natural Science Foundation of China (21838011, 21822810) and National Key Research and Development Program (No. 2018YFC1902603)


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References [1] Singh, R.; Kunzru, D.; Sivakumar, S., Monodispersed ultrasmall NiMo metal oxide nanoclusters as hydrodesulfurization catalyst. Applied Catalysis B Environmental. 2016, 185:163-173, DOI: 10.1016/j.apcatb.2015.12.013. [2] Brunet, S.; Mey, D.; Guy Pérot, et al. On the hydrodesulfurization of FCC gasoline: a review. Applied Catalysis A General. 2005, 278(2):143-172, DOI: 10.1016/j.apcata.2004.10.012 [3] Song, C.; Ma, X., New design approaches to ultra-clean diesel fuels by deep desulfurization and deep de-aromatization. Applied Catalysis B Environmental. 2003, 41, (1), 207-238, DOI: 10.1016/S0926-3373(02)00212-6 [4] Ishutenko; Mozhaev; Salnikov; Nikulshin, Selective hydrodesulfurization of model fluid catalytic cracking gasoline over sulfided Al2O3-supported Anderson heteropolyoxomolybdatebased catalysts. Reaction Kinetics Mechanisms & Catalysis 2016, 119, (2), 615-627, DOI: 10.1007/s11144-016-1083-9 [5] Song, C. S., An overview of new approaches to deep desulfurization for ultra-clean gasoline, diesel fuel and jet fuel. Catalysis Today 2003, 86, 211-263, DOI: 10.1016/S0920-5861(03) 00412-7 [6] Fan, Y. U.; Jun, L. U.; Gang, S.; Liu, H.; Bao, X., Effect of synergism between potassium and phosphorus on selective hydrodesulfurization performance of Co-Mo/Al2O3 FCC gasoline hydro-upgrading catalyst. Catalysis Today 2007, 125, (3), 220-228, DOI: 10.1016/j.cattod.2 007.02.022 [7] Liu, H.; Liu, C.; Yin, C.; Chai, Y.; Li, Y.; Liu, D.; Liu, B.; Li, X.; Wang, Y.; Li, X., Preparation of highly active unsupported nickel–zinc–molybdenum catalysts for the hydrodesulfurization of dibenzothiophene. Applied Catalysis B Environmental 2015, 174-175, 264-276, DOI: 10.1016 /j.apcatb.2015.02.009 [8] Topsøe, H.; Clausen, B. S.; Candia, R.; Wivel, C.; Mørup, S., In situ Mössbauer emission spectroscopy studies of unsupported and supported sulfided CoMo hydrodesulfurization catalysts: Evidence for and nature of a CoMoS phase. Journal of Catalysis 1981, 68, (2), 433452, DOI: 10.1016/0021-9517(81)90114-7 [9] Li, Y. W.; Pang, X. Y., Role of hydrogen in HDS/HYD catalysis over MoS2: an ab initio investigation. Journal of Molecular Catalysis A Chemical 2001, 169, (1), 259-268, DOI: 10.1016/S1381-1169(00)00568-9 [10] A. S. Hatanaka, M. Yamada, and O. Sadakane, Selective Catalytic Cracked Gasoline Hydrodes -ulfurization on the Co−Mo/γ-Al2O3 Catalyst Modified by Coking Pretreatment. Ind. Eng. Chem. Res. 1998, 1748-1754. [11] Candia, R.; Clausen, B. S.; Topsøe, H., On the Role of Promoter Atoms in Unsupported Hydrodesulfurization Catalysts: Influence of Preparation Methods. 1981, (12), 1225-1232. DOI: 10.1002/bscb.19810901206 [12] Daage, M.; Chianelli, R. R., Structure-Function Relations in Molybdenum Sulfide Catalysts: The "Rim-Edge" Model. Journal of Catalysis 1994, 149, (2), 414-427, DOI: 10.1006/jcat. 1994.1308 [13] Li, T.; Duan, A.; Zhen, Z.; Liu, B.; Jiang, G.; Jian, L.; Wei, Y.; Pan, H., Synthesis of ordered hierarchically porous L-SBA-15 material and its hydro-upgrading performance for FCC gasoline. Fuel 2014, 117, (1), 974-980, DOI: 10.1016/j.fuel.2013.10.035 [14] Wang, X.; Zhen, Z.; Xu, C.; Duan, A.; Li, Z.; Jiang, G., Effects of Light Rare Earth on Acidity


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and Catalytic Performance of HZSM-5 Zeolite for Catalytic Cracking of Butane to Light Olefins. Journal of Rare Earths 2007, 25, (3), 321-328. DOI: 10.1016/s1002-0721(07)60430-x [15] Nikulshin, P. A; Ishutenko, D. I.; Pimerzin, A. A.; Konovalov, V. V.; Pimerzin, A. 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. Journal of Catalysis 2014, 312, (2), 152-169, DOI: 10.1016/j.jcat.2014.01.014 [16] Nikulshin, P. A.; Mozhaev, A. V.; Pimerzin, A. A.; Konovalov, V. V.; Pimerzin, A. A., CoMo/Al2O3catalysts prepared on the basis of Co2Mo10-heteropolyacid and cobalt citrate: Effect of Co/Mo ratio. Fuel 2012, 100, (5), 24-33, DOI: 10.1016/j.fuel.2011.11.028 [17] Usman; Kubota, T.; Araki, Y.; Ishida, K.; Okamoto, Y., The effect of boron addition on the hydrodesulfurization activity of MoS2/Al2O3 and Co–MoS2/Al2O3 catalysts. Journal of Catalysis 2004, 227, (2), 523-529, DOI: 10.1016/j.jcat.2004.08.028 [18] Maity, S. K.; Flores, G. A.; Ancheyta, J.; Rana, M. S., Effect of preparation methods and content of phosphorus on hydrotreating activity. Catalysis Today 2008, 130, (2-4), 374-381, DOI: 10.1016/j.cattod.2007.10.100 [19] Gao, D.; Duan, A.; Xin, Z.; Zhen, Z.; Hong, E.; Qin, Y.; Xu, C., Synthesis of CoMo catalysts supported on EMT/FAU intergrowth zeolites with different morphologies and their hydroupgrading performances for FCC gasoline. Chemical Engineering Journal 2015, 270, 176-186, DOI: 10.1016/j.cej.2015.02.015 [20] Mingfeng, L. I.; Huifeng, L. I.; Feng, J.; Yang, C.; Hong, N., The relation between morphology of (Co)MoS2 phases and selective hydrodesulfurization for CoMo catalysts. Catalysis Today 2010, 149, (1), 35-39, DOI: 10.1016/j.cattod.2009.03.017 [21] Yu, F.; Gang, S.; Liu, H.; Bao, X., Morphology tuning of supported MoS2 slabs for selectivity enhancement of fluid catalytic cracking gasoline hydrodesulfurization catalysts. Applied Catalysis B Environmental 2009, 91, (1), 73-82, DOI: 10.1016/j.apcatb.2009.05.008 [22] Song, L.; Zhang, S.; Wei, Q., A new route for synthesizing nickel phosphide catalysts with high hydrodesulfurization activity based on sodium dihydrogenphosphite. Catalysis Communications 2011, 12, (12), 1157-1160, DOI: 10.1016/j.catcom.2011.03.038 [23] Nikulshin, P.; Ishutenko, D.; Anashkin, Y.; Mozhaev, A.; Pimerzin, A., Selective hydrotreating of FCC gasoline over KCoMoP/Al2O3 catalysts prepared with H3PMo12O40: Effect of metal loading. Fuel 2016, 182, 632-639, DOI: 10.1016/j.fuel.2016.06.016 [24] Fan, Y. U.; Jun, L. U.; Gang, S.; Liu, H.; Bao, X., Effect of synergism between potassium and phosphorus on selective hydrodesulfurization performance of Co-Mo/Al2O3 FCC gasoline hydro-upgrading catalyst. Catalysis Today 2007, 125, (3), 220-228, DOI: 10.1016/j.cattod. 007.02.022 [25] S. Badoga, R.V. Sharma, A.K. Dalai, and J. Adjaye, Synthesis and characterization of mesoporous aluminas with different pore sizes: Application in NiMo supported catalyst for hydrotreating of heavy gas oil. Applied Catalysis A: General, 2015, 489, 86-97. DOI: 10.1016/j.apcata.2014.10.008 [26] A. Trovarelli, Catalytic Properties of Ceria and CeO2-Containing Materials. Catalysis Reviews, 1996, 38,439-520. [27] Cuiqing L I, Sun G, Chengyue L I, et al. Preparation, Characterization, Hydrodesulfurization and Hydrodenitrogenation Activities of Alumina-supported Tungsten Phosphide Catalysts. Chinese Journal of Chemical Engineering, 2006, 14(2):184-193. DOI: 10.1016/s1004-9541


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(06)60057-8 [28] Ping, L.; Yue, Y., Rare Earth Metals Ion-exchanged β-Zeolites as Supports of Platinum Catalysts for Hydroisomerization of n-Heptane. Chinese Journal of Chemical Engineering 2011, 19, (2), 278-284, DOI: 10.1016/s1004-9541(11)60166-3 [29] Li, J.; Zeng, P.; Liang, Z.; Ren, S.; Guo, Q.; Zhao, H.; Wang, B.; Liu, H.; Pang, X.; Gao, X., Tuning of acidity in CeY catalytic cracking catalysts by controlling the migration of Ce in the ion exchange step through valence changes. Journal of Catalysis 2015, 329, 441-448, DOI: 10.1016/j.jcat.2015.06.012 [30] D. Ferdous, A.K. Dalai, J. Adjaye, and L. Kotlyar, Surface morphology of NiMo/Al2O3 catalysts incorporated with boron and phosphorus: Experimental and simulation. Applied Catalysis A: General 2005, 294, 80-91, DOI: 10.1016/j.apcata.2005.07.025 [31] X. Wang, Z. Zhao, P. Zheng, Z. Chen, A. Duan, C. Xu, J. Jiao, H. Zhang, Z. Cao, and B. Ge, Synthesis of NiMo catalysts supported on mesoporous Al2O3 with different crystal forms and the superior catalytic performance for hydrodesulfurization of dibenzothiophene and 4,6dimethyldibenzothiophene. Journal of Catalysis 2016, 344, 680–691, DOI:10.1016/j.jcat.2016. 10.016 [32] Rashidi, F.; Sasaki, T.; Rashidi, A. M.; Kharat, A. N, Ultradeep hydrodesulfurization of diesel fuels using highly efficient nanoalumina-supported catalysts: Impact of support, phosphorus, and/or boron on the structure and catalytic activity. Journal of Catalysis 2013, 299, (2), 321335, DOI: 10.1016/j.jcat.2012.11.012 [33] W. Han, H. Nie, X. Long, M. Li, Q. Yang, and D. Li, Preparation of F-doped MoS2/Al2O3 catalysts as a way to understand the electronic effects of the support Brønsted acidity on HDN activity. Journal of Catalysis 2016, 339 135-142. DOI:10.1016/j.jcat.2016.04.005 [34] Morterra; Magnacca, A case study: surface chemistry and surface structure of catalytic aluminas, as studied by vibrational spectroscopy and adsorbed species. Catalysis Today 1996, 27, (3-4), 497-532, DOI: 10.1016/0920-5861(95)00163-8 [35] W. Zhou, Q. Zhang, Y. Zhou, Q. Wei, L. Du, S. Ding, S. Jiang, and Y. Zhang, Effects of Gaand P-modified USY-based NiMoS catalysts on ultra-deep hydrodesulfurization for FCC diesels. Catalysis Today 2017. DOI: 10.1016/j.cattod.2017.07.006 [36] S. Eijsbouts, L.C.A.V. Oetelaar, and R.R.V. Puijenbroek, MoS2 morphology and promoter segregation in commercial Type 2 Ni–Mo/Al2O3 and Co–Mo/Al2O3 hydroprocessing catalysts. Journal of Catalysis 2005, 229, 352-364, DOI: 10.1016/j.jcat.2004.11.011 [37] T. Huang, J. Xu, and Y. Fan, Effects of concentration and microstructure of active phases on the selective hydrodesulfurization performance of sulfided CoMo/Al2O3 catalysts. Applied Catalysis B: Environmental, 2017, 220, DOI: 10.1016/j.apcatb.2017.08.029 [38] Nadeina, K. A.; Klimov, O. V.; Pereima, V. Y.; Koryakina, G. I.; Danilova, I. G.; Prosvirin, I. P.; Gerasimov, E. Y.; Yegizariyan, A. M.; Noskov, A. S., Catalysts based on amorphous aluminosilicates for selective hydrotreating of FCC gasoline to produce Euro-5 gasoline with minimum octane number loss. Catalysis Today 2016, 271, 4-15, DOI: 10.1016/j.cattod.2016. 01.010 [39] WEN; XiaoDong; Zeng, T.; TENG; BoTao; ZHANG; FuQiang; LI; YongWang; Wang, J., Hydrogen adsorption on a Mo27S54 cluster : A density functional theory study. Journal of Molecular Catalysis A Chemical 2006, 249, (1), 191-200, DOI: 10.1016/j.molcata.2006.01.018 [40] Hensen, E. J. M.; Beer, V. H. J. D.; Veen, J. A. R. V.; Santen, R. A. V., A Refinement on the


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Notion of Type I and II (Co)MoS Phases in Hydrotreating Catalysts. Catalysis Letters 2002, 84, (1-2), 59-67, DOI: 10.1023/a: 1021024617582 [41] Frank, J. C.; Guyot, A.; Hamaide, T.; Deore, C. E. L., 5607890 Supported Lewis acid catalysts derived from superacids useful for hydrocarbon conversion reactions. Journal of Molecular Catalysis A Chemical 1998, 125, (2–3), 153-154, DOI: 10.1016/S1381-1169(98)80016-2


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Figure 1. The nitrogen adsorption–desorption isotherms of γ-Al2O3 and prepared catalysts. (a) CoMo/γAl2O3, (b)CoMo/γ-Al2O3P(2), (c) CoMo/γ-Al2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γAl2O3Ce(2.5), (f) CoMo/γ-Al2O3P(2)Ce(1.75). 119x87mm (220 x 220 DPI)


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Figure 2. FTIR spectra of pyridine adsorbed on γ-Al2O3 and catalysts. (a) CoMo/γ-Al2O3, (b)CoMo/γAl2O3P(2), (c) CoMo/γ-Al2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γ-Al2O3Ce(2.5), (f) CoMo/γAl2O3P(2)Ce(1.75). (A) 200 °C and (B) 350 °C 136x201mm (150 x 150 DPI)


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Figure 3. H2-TPR profiles of the oxide catalysts: (a) CoMo/γ-Al2O3, (b) CoMo/γ-Al2O3P(2), (c) CoMo/γAl2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γ-Al2O3Ce(2.5), (f) CoMo/γ-Al2O3P(2)Ce(1.75). 214x164mm (300 x 300 DPI)


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Figure 4. HRTEM images of the sulfide catalyst: (a) CoMo/γ-Al2O3, (b) CoMo/γ-Al2O3P(2), (c) CoMo/γAl2O3Ce(0.75), (d) CoMo/γ-Al2O3Ce(1.75), (e) CoMo/γ-Al2O3Ce(2.5), (f) CoMo/γ-Al2O3P(2)Ce(1.75) 237x161mm (100 x 100 DPI)


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Figure 5. Distributions of slab lengths (A) and stacking number (B) of the sulfide catalysts 133x205mm (150 x 150 DPI)


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Energy & Fuels

Figure 6. Mo3d XPS spectra recorded for sulfided catalysts: (a) CoMo/γ-Al2O3 202x165mm (300 x 300 DPI)


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Figure 6. Mo3d XPS spectra recorded for sulfided catalysts: (b) CoMo/γ-Al2O3P(2) 203x166mm (300 x 300 DPI)


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Figure 6. Mo3d XPS spectra recorded for sulfided catalysts: (c) CoMo/γ-Al2O3Ce(0.75) 202x164mm (300 x 300 DPI)


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Figure 6. Mo3d XPS spectra recorded for sulfided catalysts: (d) CoMo/γ-Al2O3Ce(1.75) 203x166mm (300 x 300 DPI)


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Figure 6. Mo3d XPS spectra recorded for sulfided catalysts: (e) CoMo/γ-Al2O3P(2.50) 202x166mm (300 x 300 DPI)


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Figure 6. Mo3d XPS spectra recorded for sulfided catalysts: (f) CoMo/γ-Al2O3P(2)Ce(1.75) 202x165mm (300 x 300 DPI)


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Figure 7. Co2p XPS spectra recorded for sulfided catalysts: (a) CoMo/γ-Al2O3, 208x164mm (300 x 300 DPI)


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Figure 7. Co2p XPS spectra recorded for sulfided catalysts: (b) CoMo/γ-Al2O3P(2) 208x166mm (300 x 300 DPI)


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Figure 7. Co2p XPS spectra recorded for sulfided catalysts: (c) CoMo/γ-Al2O3Ce(1.75) 208x166mm (300 x 300 DPI)


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Figure 7. Co2p XPS spectra recorded for sulfided catalysts: , (d) CoMoP/γ-Al2O3P(2)Ce(1.75) 208x166mm (300 x 300 DPI)


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Energy & Fuels

Figure 7. Co2p XPS spectra recorded for sulfided catalysts: (e) CoMo/γ-Al2O3Ce(2.50) 208x164mm (300 x 300 DPI)


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Figure 7. Co2p XPS spectra recorded for sulfided catalysts: (f) CoMo/γ-Al2O3P(2)Ce(1.75) 208x165mm (300 x 300 DPI)


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Energy & Fuels

Figure 8. Dependence of HDS, HYDO and ∆RON of FCC gasoline hydrotreatment on temperature over CoMo/γ-Al2O3 and CoMo/γ-Al2O3P(2)Ce(1.75) catalysts 93x176mm (300 x 300 DPI)


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Figure 9. Schematic illustration of cerium influence on the active phase morphology 227x58mm (300 x 300 DPI)


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Figure 10. Dependence of the TOF number in thiophene HDS and1-hexene HYD over catalysts on the amount of Ce addition. 244x176mm (300 x 300 DPI)


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Figure 11. Dependence of HDS% and conversion of isomerization (%) of model gasoline hydrotreating on BAS/LAS ratio. 234x170mm (300 x 300 DPI)


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Î³-Al2O3 Catalysts Modified Using

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